Users Guide for Deployment of Stationary Fuel Cells
22 August 2014
Fuel Cell Focus Group
Focus Group Scope: The scope of this Focus Group is to develop a comprehensive understanding of the fuel cell codes for
both stationary and mobile fuel cells for specific use with telecom, wireless, datacom, emergency 911, police radio, security
and surveillance, and catastrophic infrastructure for commercial, military, or residential use at ground level, on rooftop, or
on platform applications for backup, supplemental and/or alternative electric power sources as well as associated fuel
storage requirements.
Document Scope: The Users Guide for Deployment of Stationary Fuel Cells
for Wireless and ICT Infrastructure will support the deployment of fuel cell technologies for the wireless and ICT industries.
Table of Contents
1. Introduction
2. Use of Fuel Cells In the ICT Industry
3.
Benefits of using Fuel Cells
4.
Overview of Fuel Cell Technologies
5. Generic Diagram for backup Power System
6. Fuels table
7. Summary C&S Sheet
8. Basic Principles of Fuel Cell Safety
9. Fuel Supply Considerations
10. General Criteria for Fuel Cell Siting (use detailed information already written)
11. Comparison of Fuel Cell technologies to other Power Generation Technologies /Cost Comparison of Backup
Power Technologies
Annex A Supplementary Information
Annex B Example Systems
Annex C Example Permits
Introduction
The purpose of this document is to support the deployment of fuel cells by providing background information on fuel cell
technologies, fuel sources, and permitting that would help a project developer. The Guide may also be helpful to other
parties involved in project deployment such as:
-
Equipment manufacturers
-
Fuel suppliers
-
Code official
-
Municipal planners
-
Emergency responders
Use of Fuel Cells in the ICT Industry
.
May 28, 2013
Telecom networks require significant energy to operate. Even though energy prices are presently at relatively reasonable
levels, the operators are trying to reduce the energy consumption of their networks. There are several factors behind this
focus. For example, energy bills contribute to more than half the operating cost of the network. In addition, lower energy
usage is an effective way for operators to minimize their environmental impact, reduce carbon footprint and use more
sustainable forms of energy.
Since telecom networks typically have tens of thousands of sites, operators must reduce operational and maintenance
costs to compete effectively. Operators around the world are exploring applications of alternate energy solutions in their
networks. Solar arrays, wind turbines and fuel cells have all been implemented in various telecom applications with varying
degrees of success. These solutions have higher initial costs but offer significantly lower costs of operation and
maintenance with substantially lower carbon footprint. The options for reducing costs and the environmental impact of
running a network are not only good for the environment; they also make excellent business sense for operators and
support sustainable, profitable business. Some governments, such as the United States, are even offering tax incentives to
help foster the adoption of these technologies. This paper provides evidence that hydrogen fuel cell back-up power
systems are not only reliable and green, but result in real operating expense reduction.
Fuel Cells
Fuel cells are electrochemical devices that convert chemical energy in fuels into electrical energy directly, thereby
generating power with high efficiency and low environmental impact. There are a variety of different types of fuel cells.
This paper focuses on the Proton Exchange Membrane (PEM) fuel cell which utilizes hydrogen as a fuel. PEM fuel cells are
best suited for backup power applications as they provide high power densities and operate at low temperatures (60 to
80°C), which allows them to startup faster than other fuel cells.
Typically, backup power for telecommucation sites is provided by lead-acid batteries and diesel generators, which have
considerable environmental impact. Fuel cells provide an eco-friendly backup power solution as the only byproducts are
heat and water. They are efficient, reliable, quiet, and designed to last a long time.
Advanced Fuel Cell Solution for Telecommunications Networks
Wireline and wireless telecom networks have a wide range of power loads and an extensive set of compliance
requirements. The CommScope solution incorporates a compact fuel cell solution in an enclosure, which has been
deployed over the past 6 years with other active electronics in the outside plant for several other applications by leading
telecommunication companies. The combination of existing industry knowledge and numerous field deployments was
instrumental in development of this highly reliable solution for outdoor power backup applications.4
Figure 1 illustrates a 8-kilowatt fuel cell module housed in a 63-inch (H) x 45-inch (W) x 52-inch (D) cabinet, which is
Telcordia GR-487 compliant. The cabinet contains all necessary power conditioning equipment for providing regulated DC
Voltage to match site requirements, typically at battery float voltage. The system provides instantaneous power upon loss
of AC or DC power using a small bridge battery located in the battery compartment of the cabinet.
Figure 1The equipment stack in the cabinet from the top to the bottom includes the following:
1. AC to DC Rectifier, used to provide primary power when grid electricity is available
2. Overall System Controller (OSC)
3. A Power Conditioning Modules (PCM) – a DC-DC converter, which provides regulated voltage to load
4. Wireless Radio and Microwave backhaul equipment
5. An 8-kilowatt Fuel Cell Power Module (FCPM) – Proton Exchange Membrane (PEM) based hydrogen fuel cells
In addition, the cabinet has a DC distribution panel with breakers for connecting the DC load, the PCM and bridge batteries.
The OSC provides the necessary means to detect loss of AC or DC power in order to turn on the FCPM for providing power
when needed. The PCM’s prime function is to take unregulated DC voltage from the FCPM stack and convert to a steadystate DC voltage as required by the telecommunications application. Typically 54 volts of direct current (VDC) is provided
with a +/- 0.5 volt variance. The system operates in a hydrogen fail safe mode in accordance with ANSI/CSA FC-1
requirements. The OSC also provides a series of alarms such as open door intrusion, power major/minor and other alarms
along with those specific to fuel cell technology. In addition, the OSC controls the time necessary to purge five volumes of
air from the system, per the FC-1 requirement. This purging operation followed by turn up of the FCPM to full power is
about 90 seconds.
The cabinet equipment configuration discussed above is recommended for new site installations or for sites where the
existing radio equipment can be accommodated in the fuel cell cabinet to reduce the overall site footprint and power
consumption. For existing sites, the fuel cell cabinet can also be installed with only the fuel equipment in the cabinet, and it
can interface with the existing power supply, batteries, and radio equipment located in other cabinets or shelter on the
site.
Key Features of the Advanced Fuel Cell Solution
The following list highlights the key features of the solution:
• No monthly start up requirement
• Unlimited start/stop capability
• Industry leading fuel cell efficiency
• Patented Dry/Dry Operation – No humidification required for the hydrogen or air feed to the fuel cell
• Highest power density in the industry
• Single footprint capable of accommodating electronics in the cabinet, which houses the fuel cell
• Power conditioning with a range from -42 VDC to -58 VDC, which matches most telecommunication sites. Typically
these sites are set at battery float voltage around -54 VDC.
• Design in accordance with ANSI/CSA FC-1, CE and Telcordia requirements
• All aspects pertaining to the proper and safe handling of hydrogen fuel source.
• A system controller capable of maintaining all aspects relating to fuel cell operation and safety as well as providing all
Telco required alarms
• Cabinet thermal systems and controls required to meet Telcordia -40°C to +46°C ambient temperature conditions
• Cabinet ventilation controls required to operate the fuel cell to their maximum efficiency
• Electrical system including bridging power in order to ensure no loss of DC power to the site load during an AC power
outage
The hydrogen to the fuel cell cabinet is provided by hydrogen cylinders stored in a hydrogen storage cabinet (Figure 2),
which has the capacity to store 16 standard hydrogen cylinders. The hydrogen cylinders are configured in two banks of
eight with an automatic switch-over from one bank to another. This cabinet includes the pressure regulator, manifold,
flexible hoses, check valves and safety relief valve. The storage cabinet can be placed next to the fuel cell cabinet or located
away from it for hydrogen logistics reasons. The hydrogen pressure of each bank is continuously monitored and an
automatic email can be issued when it reaches a preset threshold. This feature allows notification to the hydrogen
distributor for refueling the cylinders in the cabinet.
Figure 2All aspects of the fuel cell operation are monitored by the system controller and can be communicated remotely
using an Ethernet connection or a wireless modem.
Several alarms are also reported by the system controller. Following is a partial list of these alarms:
• Door Open Alarm
• Ventilation Fan Alarm
• DC Power Major and Minor Alarms
• AC Fail Alarm
• Battery on Discharge
• Ambient Temperature (Internal and External)
• Hydrogen Storage Pressure for each Bank
• Cabinet Low Temperature Alarm
• FCPM Major and Minor Fail Alarm
Data collected through remote fuel cell activation or as gathered when actual power outages occurred can be used to
evaluate the reliability and durability of the fuel cell.
Global Field Installations and Results
The fuel cell solution was installed in various configurations at several locations around the world to test the operational
reliability and durability of the system in different climate conditions with varying quality of power grids. These
deployments ranged from outdoor and indoor wireless cell sites to wireline huts and shelters in Asia, Europe and North
America.
Asia Field Installation
Figure 3 illustrates an application on a cell site in an emerging wireless market in Asia. The existing backup power solution
on this site included several strings of lead acid batteries and a diesel generator. The site has numerous power outages
every day and considerable amount of diesel fuel is consumed, thereby creating significant air pollution. In addition, diesel
pilferage is rampant, which increases the cost of operating the site.
Figure 3
The fuel cell and the hydrogen storage cabinets were placed next to each other on an existing concrete pad on this site.
The DC bus of the wireless site was connected to DC distribution panel in the fuel cell cabinet. The system controller
monitored and recorded data on all aspects of the fuel cell operation. The data was transmitted remotely through a
wireless GPRS modem. This site experienced frequent power outages and as such the fuel cell operated each day to
provide power. The daily power outages ranged from as low as 15 minutes to as high as 17 hours. The fuel cell provided the
required power load and kept the wireless cell site operational at all times.
The system monitored the hydrogen fuel consumption at the site and generated automatic e-mail for the local hydrogen
distributor to schedule hydrogen delivery on the site. This notification scheme worked very well in ensuring timely delivery
of the hydrogen to the site. Figure 4 depicts the power outage on this wireless cell site for a 50-day period, during which
there were 235 outages. The fuel cell supported all the outages and operated for a cumulative time period of 126 hours.
Figure 4
Another installation in Asia was on a cell site shared by several wireless operators and owned by a tower company. Figure 5 illustrates this
application. The fuel cell provided backup power for two operators on this site. The DC bus for the wireless operators was tied to the DC
distribution panel in the cabinet. This site also experienced frequent power outages and the fuel cell provided backup power during all outages.
The setup of this installation was similar to the one described above with respect to monitoring and data collection. Figure 6 depicts the power
outage on this wireless cell site for a 30-day period, during which there were 48 outages. The fuel cell supported all the outages and operated for a
cumulative period of 31 hours. The ambient temperature during these operational periods at these sites was about 45ºC. Both of these field
installations have demonstrated the high reliability and durability of the fuel cell cabinets in providing backup power.
Figure 5
Figure 69
Europe Field Installation
Figure 7 illustrates the deployment of the fuel cell cabinet on a wireless cell site in Europe. Prior to this deployment, the
BTS equipment on the site was housed in a shelter with an air-conditioner, which consumed considerable amount of
power. The shelter was removed from the site and all equipment in it accommodated in the fuel cell cabinet within 6
hours. The site footprint was reduced by over 50 percent and the energy consumption was reduced as the air-conditioner
was eliminated. This site is located in a remote area in Eastern Europe and it experiences several utility outages. Figure 8
depicts the power outages on this site for a 6-month period, during which there were 82 outages, which ranged from a few
minutes to up to 8 hours. The fuel cell supported all the outages and operated for a cumulative time period of over 56
hours. This fuel cell controller on site is connected to a GPRS modem and the wireless operator can remotely log in to
monitor all aspects of the fuel cell operation. Contrary to the initial perception, hydrogen delivery to the site was not an
issue.
Figure 7
Figure 810
North America Field Installation
Figure 9 illustrates the deployment of the fuel cell cabinet outside the headquarters of the Society of Cable
Telecommunication Engineers in Exton, PA. This building has solar panels on the roof, which are connected to an inverter
to provide AC power. When required, the AC power from the inverter provides backup power to the data center located in
the building. Otherwise it offsets the AC load in the building. In this installation, the fuel cell was tied to the DC side of the
solar power system. The fuel cell operates when there is an AC outage and the solar panels can’t provide the power
required, because either it is nighttime or there isn’t enough solar irradiance due to cloud cover. This office building has
few power outages during a given year.
Figure 9
During Hurricane Irene, the office building had an 18-hour power outage. The fuel cell provided the backup power during
this period. The office building has recently experienced other power outages due to bad weather in the area and the fuel
cell has supported all these power outages.11
Key Observations
The field installations in various parts of the world, and with different equipment configurations, have demonstrated that
the advanced fuel cell solution provides a reliable and cost-competitive means of providing backup power. A summary of
the key observations from these field installations is listed below:
• The fuel cell operated in diverse environments with 100 percent availability
• Average maintenance costs were reduced by 77 percent and average operational costs were reduced by 37 percent
• On average, the footprint space was reduced by 50 percent
• Real time remote monitoring of power backup reduced truck rolls
• Hydrogen is widely available and misconceptions about safety easily were dispelled after installation and operational
experience
Conclusion
The fuel cell application, in various geographical locations around the world and in different equipment configurations, has
demonstrated that it is a highly reliable, durable and cost-competitive solution. Several telecommunications companies
around the world have started to evaluate the fuel cell technology for backup power. Some governments and agencies are
providing incentives to help companies embrace this environmentally friendly technology and deploy it in significant
volumes.
www.commscope.com
Visit our website or contact your local CommScope representative for more information.
© 2013 CommScope, Inc. All rights reserved.
All trademarks identified by ® or ™ are registered trademarks or trademarks, respectively, of CommScope, Inc. This
document is for planning purposes only and is not intended to modify or supplement any specifications or warranties
relating to CommScope products or services.
Benefits of Fuel Cell Technologies
Stationary fuel cells range in power from hundreds of watts to multiple megawatts, and power everything from remote
telecom towers to large office complexes. Fuel cells offer choice of feedstocks. Many stationary fuel cells run on hydrogen;
however, stationary fuel cells are often powered by natural gas or biogas at facilities dealing with organic waste streams.
Larger fuel cells using molten carbonate or phosphoric acid technologies can use a variety of hydrogen-rich feedstocks and
convert the fuel into hydrogen using an internal reformer.
Stationary fuel cells offer a number of advantages over competing power sources. One such advantage is that fuel cells
produce exceedingly reliable, high quality power. This is important for many types of business users. Natural variance in
voltage from the grid can damage sensitive electronic equipment. US businesses lose $29 billion annually from computer
damage due to power outages. This is why many data centers have ditched grid power and invested in fuel cell systems,
which can be up to 99.9999% reliable. That translates to roughly one minute of downtime in a six year span. Since fuel cell
systems keep running during power outages, they also eliminate the need for backup generators. –
http://www.fchea.org/index.php?id=55
Fuel cells are used for primary power, or as back-up power in grid-powered locations for applications such as
telecommunications, security, transportation communications and others. Fuel cells are also being used in remote and offgrid applications as one component to a hybrid power solution which can involve other power sources; such as solar arrays,
wind turbines, batteries, and generators.
According to a recent whitepaper from ReliOn “There are currently more than 1,000 telecommunication sites using fuel cell
power solutions in North America alone. While this represents a small percentage as far as total telecom sites, it is clear
that fuel cells are a growing solution to the need for reliable energy for sites in locations as diverse as cities, suburbs, rural,
off-grid and environmentally sensitive areas.”
Using fuel cells in telecommunication facilities increase reliability, decrease maintenance costs, and decrease emissions.
Reliability is increased because a number of system solutions, using a variety of hydrogen-rich feedstocks, can be utilized
independently from the grid. These fuel cells will continue to operate as long as fuel is provided to the fuel cell.
Fuel cell systems offer lifecycle cost savings for backup power distributed at telecom nodes over a range of requirements;
from short duration runtime applications to extended duration runtime applications.
Fuel storage can be provided on site, allowing the site to operate for longer periods. Fuel cell-based backup power systems
are designed to operate for approximately ten years, while battery strings may need total replacement every three to five
years. Additionally fuel cell solutions require only minimal annual maintenance compared to quarterly site visits to service
diesel generators or batteries.
Unlike generators, fuel cells do not use combustion and therefore there are no NOx, SOx or particulate emissions at the
point of use. A fuel cell utilizing hydrogen fuel produces no harmful emissions at the point of use. Because of this, they are
exempted from emissions permitting by the California Air Resources Board as well as many other states. Fuel cells are also
quiet. This makes them suitable for places where noise is an issue, including environmentally sensitive areas.
Emergency Preparedness
Recent events, such as the Hurricane Katrina disaster of 2005 and Superstorm Sandy of 2012, to name just two, have
increased focus on availability and reliability of telecommunications services. Telecom systems, whether wireless or
wireline, must be able to provide continuous, reliable service to customers at all times, and in particular during extended
power outages. The choice of backup power technology has a direct impact on the availability of services to the end-user
and contributes significantly to a telecommunication company’s market success.
Traditional solutions include batteries and diesel generators. During extended-duration backup power needs or in urban
locations where noise and pollution are a particular concern, fuel cells offer a practical solution. Fuel cell backup power
solutions offer numerous compelling advantages over conventional battery and diesel generators in emergency backup
power applications. These include environmental benefits, improved reliability and durability, scalability, and lifecycle cost
savings – particularly at telecom nodes which require relatively low power over a long duration.
Further Reading:
Back-up Power and Fuel Cells Fact Sheet, FCHEA, http://www.fchea.org/core/import/PDFs/factsheets/Backup%20Power%20Fuel%20Cells%20Fact%20Sheet.pdf
The Business Case for Fuel Cells 2012, Fuel Cells 2000, http://www.fuelcells.org/uploads/FC-Business-Case-2012.pdf
Fuel Cell Basics for Communications Industry Professionals, ReliOn Power, The Alternative Energy e-Magazine:
http://www.altenergymag.com/emagazine/2012/10/fuel-cell-basics-for-communications-industry-professionals/1988
Using Fuel Cells for Backup Power for Telecommunications Facilities, U.S. Department of Energy Hydrogen and Fuel Cells
Program, http://www.hydrogen.energy.gov/permitting/telecommunications.cfm
Why Fuel Cells for Telecoms Backup is a Good Call, Fuel Cells Today, http://www.fuelcelltoday.com/analysis/analystviews/2013/13-06-05-why-fuel-cells-for-telecoms-backup-is-a-good-call
Benefits of Fuel Cell Solutions for Backup Power Needs in Telecom, Dantherm Power,
dantherm-power.com/files/PDF/DP_Telecom_Advantages.pdf
Overview of Fuel Cell Technologies
A fuel cell is an electrochemical device that combines hydrogen and oxygen to produce electricity; heat, and water (see
Figure 2.1). The hydrogen comes from any hydrocarbon fuel such as natural gas, gasoline, diesel, or methanol. The
oxygen comes from air around the fuel cell. Because fuel cells are electrochemical devices that operate without
combustion, they do not generate combustion emissions.
A fuel cell can operate at high efficiencies and provide an
opportunity for the capture of heat that is given off by the process
(cogeneration). The fuel cell itself has no moving parts, making it
a quiet and reliable source of power, electricity, heat, and water.
Fuel cell equipment comprises individual fuel cells “stacked” to
make a fuel cell stack that is the heart of the fuel cell equipment
or power plant. In addition, there may be a fuel processing
section of the equipment that is separate from or integral to the
cell stack. Where alternating current (ac) power is needed,
Figure 2.1. Fuel Cell Configuration
there will be a power conditioning section to convert the direct
current (dc) power produced by the fuel cell into ac power.
Although all fuel cell power plants contain these components, the assembly of these components into the actual equipment is
very important. Stationary fuel cell equipment can be categorized as either unitary, matched modular, modular, or sitebuilt.
A typical fuel cell is composed of a fuel cell processor/reformer, electrodes, electrolyte, oxidant, fuel cell stack, and
power-conditioning equipment. These components are described briefly in the following paragraphs.
• Fuel Processor/Reformer
The job of the fuel processor/reformer is to provide relatively pure hydrogen to the fuel cell, using a fuel that is readily
available or easily transportable. The hydrogen comes from any hydrocarbon fuel such as natural gas, liquified petroleum
gas, or even diesel fuel. The generic term generally applied to the process of converting liquid or gaseous light hydrocarbon
fuels to hydrogen and carbon monoxide is reforming. A number of methods are used to reform fuel. The three most
commercially developed and popular methods are steam reforming, partial-oxidation reforming, and autothermal reforming.
These processes involve heating the hydrocarbon fuels to the point of vaporization and then injecting superheated steam to
help force the reaction to completion. The heat source for the reaction is usually an immediately adjacent high-temperature
furnace that combusts a small portion of the raw fuel or the fuel effluent from the fuel cell. Rejected heat from the fuel cell
system also can be used for the heat source.
The reforming of hydrocarbon-rich fuels is often not complete, and gases including carbon monoxide pass through the
reforming process. These gases are converted to water and carbon dioxide with a catalyst.
• Electrodes
A hydrogen-rich gas from the reformer (or hydrogen from storage on the site) is fed
continuously to the electrodes where an electrochemical reaction takes place to produce an
electric current. As with a battery, two electrodes—the anode and the cathode—are used to
produce electricity.
Anode
The anode, the negative post of the fuel cell, has several jobs. It conducts the electrons freed
from the hydrogen molecules so they can be used in an external circuit. The anode is etched
with channels that disperse the hydrogen gas equally over the surface of the catalyst is used to
split the hydrogen molecules into positively charged ions, giving up one electron each.
The positively charged ions then migrate through the electrolyte (see description of
electrolyte below) to the positive post (cathode). The negatively charged electrons travel
through the external circuit to produce electric energy.
Cathode
The cathode, the positive post of the fuel cell, also is etched with channels that distribute the
continuous supply of oxygen from air (oxidant) to the surface of the catalyst. It also conducts
the electrons back from the external circuit to the catalyst, where they can recombine with the
hydrogen ions and oxygen to form water.
• Electrolyte
The electrolyte transports the positively charged hydrogen ions to the cathode and thereby
completes the cell electric circuit. It also provides a physical barrier to prevent the fuel and
oxidant gas streams from directly mixing.
• Oxidant
The most common oxidant is gaseous oxygen, which is available from air for stationary fuel
cell applications. The oxidant is introduced into the system at the cathode (see cathode
above).
Stationary fuel cell equipment
can be categorized in a number
of different ways:
• unitary – All the components
(fuel processor, cell stack, and
power-conditioning unit) are
matched together and assembled
in one complete piece of
equipment.
• matched modular – One or
more of the components are
separate from the others but
have been designed to work
together and are provided by
one manufacturer for assembly
in the field.
• Modular – The components
have not been designed
specifically to work together and
are not provided by one
manufacturer but by separate
manufacturers for assembly in
the field.
• site-built – This field-erected
fuel cell uses components and
pieces from various sources to
make up a fuel cell power plant.
Unitary equipment will typically
provide a smaller output (up to
~500 kW) due to the limitation
on the size of the equipment
posed by the single package in
which it would be provided.
Matched modular or modular
would have larger outputs. Sitebuilt fuel cell power plants
would provide large outputs, on
the order of a few megawatts or
more.
• Fuel Cell Stack
A single fuel cell produces only about 0.7 volt. To increase the voltage, many separate fuel cells must be combined to form a
fuel cell stack. The fuel cell stack is integrated into a fuel cell system with other components, including a fuel reformer,
power electronics, and controls. Simply stated, the more cells in the stack and the more stacks in the equipment, the greater
the power output. The term stack power density describes how much power is produced for a given area of
fuel cell.
• Power-Conditioning Equipment
The fuel cell system can provide either dc or ac power. Power conditioning for a fuel cell power plant used to supply dc
rated equipment includes current and voltage controls. Power conditioning for a fuel cell power plant used to supply acrated equipment includes dc to ac inversion and current, voltage and frequency control, stepping the voltage up or down
through a transformer depending on final equipment utilization voltage, and maintaining harmonics output to an acceptable
level. In addition, transient response of the power-conditioning equipment should be considered. For utility grid
interconnection, synchronization, real power (watts) ramp rate, and reactive power (volt-amperes reactive, or VAR) control
also must be addressed.
2.2
Types of Fuel Cells
Four primary fuel cell system types have been utilized in stationary fuel cell equipment installed in commercial buildings.
The descriptions that follow provide specific detail on the following fuel cell system types:
•
•
•
•
molten carbonate fuel cells (MCFCs)
phosphoric acid fuel cell (PAFCs)
proton exchange membrane fuel cell (PEMFCs)
solid oxide fuel cells (SOFCs).
Alkaline fuel cells (AFCs) are not discussed in this document because they are not usually installed in commercial
buildings. They are a type of fuel cell with low overall efficiencies and low operating temperatures.
Fuel cells are classified primarily by the kind of electrolyte they employ. This determines the kind of chemical reactions
that take place in the cell, the kind of catalysts required, the temperature range in which the cell operates, the fuel required,
and other factors. These characteristics, in turn, affect the applications for which these cells are most suitable. Table 2.1
provides a comparison of the four fuel cells discussed.
Table 2.1. Fuel Cell Comparison
Molten Carbonate Fuel Cell
MCFC
PAFC
10-kW to 2-MW MCFC systems
SOFC
have been tested.
Ion exchange membrane
Solid metal oxide
MCFC systems promise high
140–212°F
1100–1830°F
fuel-to-electricity
efficiencies,
(60–100°C)
(600–1000°C)
about 60% normally
or 85% with
cogeneration, as the excess heat
External
External/Internal
generated can be harnessed and
O2/Air
O2/Airheat and
used in combined
power
plants.
35-50%
45-60%
PEMFC
Electrolyte
Molten carbonate salt
Liquid phosphoric acid
Operating Temperature
1100–1830°F
(600–1000°C)
300–390°F
Reforming
External/Internal
External
Oxidant
CO2/O2/Air
O2/Air
Efficiency (without
cogeneration)
45-60%
35-50%
Maximum Efficiency (with
cogeneration)
85%
80%
60%
Maximum Power Output
Range (size)
2 MW
1 MW
250 kW
220 kW
Waste Heat Uses
Excess heat can produce
high-pressure steam
Space heating or water
heating
Space heating or water heating
Excess heat can be used
to heat water or produce
steam
2.2.1
(150–200°C)
Electrochemical Reactions
85%
Anode:
Molten Carbonate Fuel Cells
The molten carbonate fuel cell (MCFC) uses a molten carbonate salt as the electrolyte. It
may also be fueled with coal-derived fuel gases or natural gas.
MCFCs are high-temperature fuel cells that use an electrolyte composed of a molten
carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminum
oxide (LiAlO2) matrix. Because they operate at extremely high temperatures
of 600ºC (roughly 1100ºF) and above, nonprecious metals can be used as catalysts at the
anode and cathode, reducing costs.
Manufacturers claim that fuel efficiencies approach 60%, considerably higher than the
35%–50% efficiencies of a phosphoric acid fuel cell plant. When the waste heat is
captured and used, overall fuel efficiencies can be as high as 85%.
Unlike alkaline, phosphoric acid, and polymer electrolyte membrane fuel cells, MCFCs
do not require an external reformer to convert more energy-dense fuels to hydrogen. Due
to the high temperatures at which they operate, these fuels are converted to hydrogen
within the fuel cell itself by a process called internal reforming, which also reduces cost.
H2+CO3 2- ⇒ H2 O + 2eCathode:
½O2+CO2+2e
⇒ CO
3
2-
Cell:
H2+½O2+CO2 ⇒ H2O+CO2
MCFCs are not prone to carbon monoxide or carbon dioxide "poisoning"—they even
can use carbon oxides as fuel—making them more attractive for fueling with gases made from coal. Although they are
more resistant to impurities than other fuel cell types, scientists are looking for ways to make MCFCs resistant enough to
impurities from coal, such as sulfur and particulates.
The primary disadvantage of current MCFC technology is durability. The high temperatures at which these cells operate
and the corrosive electrolyte used accelerate component breakdown and corrosion, decreasing cell life. Scientists currently
are exploring corrosion-resistant materials for components as well as fuel cell designs that increase cell life without
decreasing performance.
2.2.2
Phosphoric Acid Fuel Cells
A phosphoric acid fuel cell (PAFC) consists of an anode and a cathode made of a finely
dispersed platinum catalyst on carbon paper, and a silicon carbide matrix that holds the
phosphoric acid electrolyte.
Phosphoric Acid Fuel Cell
International Fuel Cells has
installed many of these 200-kW
phosphoric acid fuel cells. This
one is situated at a hospital and
provides power and heat.
PAFCs are more tolerant of impurities in the reformate than proton exchange membrane
fuel cells, which are easily "poisoned" by carbon monoxide—carbon monoxide binds to
the platinum catalyst at the anode, decreasing the fuel cell's efficiency. They are 85%
efficient when used for the cogeneration of electricity and heat but less efficient at
generating electricity alone (35% to 50%). This is only slightly more efficient than
combustion-based power plants, which typically operate at 33% to 35% efficiency.
More than 200 PAFC systems have been installed all over the world including hospitals,
nursing homes, hotels, office buildings, schools, utility power plants, military bases, an
airport terminal, landfills, and waste water treatment plants. Most are the 200-kW PC25
fuel cell power plant manufactured by the ONSI Corporation, including one that powers a
police station in New York City's Central Park and two that provide supplemental power
to the Conde Nast Building at 4 Times Square in New York. The PC25 is a prepackaged
tested and listed unit delivered on a skid to facilitate installation and interconnection with
the building systems and fuel source. The largest PAFC system to be tested is an 11-MW
power plant sited in Japan. Many of these installations have operated for more than
40,000 hours without interruption.
Photo courtesy of
International Fuel Cells
More than 200 of the
International Fuel Cells 200-kW
ONSI units have been put into
service all over the world.
Photo courtesy of
International Fuel Cells
Electrochemical Reactions
Anode:
H2 ⇒ 2H+ + 2eCathode:
½ O2+2H++2e- ⇒ H2O
Cell:
H2+½O2 ⇒ H2O
2.2.3
Proton Exchange Membrane Fuel Cells
The proton exchange membrane fuel cell (PEMFC) uses a fluorocarbon ion exchange with a
polymeric membrane as the electrolyte. These cells operate at relatively low temperatures
and can vary their output to meet shifting power demands. These properties make PEMFCs
the best candidates for light-duty vehicles, buildings, and much smaller applications.
PEMFCs operate at relatively low temperatures, around 80°C (176°F). Low-temperature
operation allows them to start quickly (less warm-up time) and results in less thermal stress
on system components. However, this low-temperature operation requires that a noblemetal catalyst (typically platinum) be used to separate the hydrogen electrons and protons.
The platinum catalyst is extremely sensitive to carbon monoxide poisoning, making it
necessary to employ an additional reactor to reduce carbon monoxide in the fuel gas if the
hydrogen is derived from a carbon-containing fuel. Developers are exploring different
catalyst formations that are more resistant to carbon monoxide.
Manufacturers claim that the PEMFC system efficiencies range from 35% to 50% and,
with capture and use of waste heat, can have an overall efficiency approaching 60%.
Proton Exchange Membrane
Fuel Cell
Avista Labs has developed a
modular technology, allowing
“hot swapping” of stack
subcomponents and on-line
maintenance.
Photo courtesy of Avista Labs
Ballard Generation Systems' first
field trial of a 250-kW Natural
Gas PEM Fuel Cell Power
Generator is sited at the Crane
Naval Surface Warfare Center
for a two-year demonstration and
testing program.
Photo courtesy of Ballard
Electrochemical Reactions
Anode:
H2 ⇒ 2H+ + 2eCathode:
½O2+2H++2e- ⇒ H2O
Cell:
H2+½O2 ⇒ H2O
2.2.4
Solid Oxide Fuel Cells
Solid oxide fuel cells (SOFC) currently under development use a thin layer of zirconium
oxide as a solid ceramic electrolyte and include a lanthanum manganate cathode and a
nickel-zirconia anode. This is a promising option for high-powered applications such as
industrial uses or central electricity generating stations.
SOFCs operate at very high temperatures—around 1000ºC (~1800ºF). High-temperature
operation removes the need for a precious-metal catalyst. It also allows SOFCs to reform
fuels internally, which enables the use of a variety of fuels and reduces the cost
associated with adding a reformer to the system.
SOFCs are the most sulfur-resistant fuel cell type. In addition, they are not poisoned by
carbon monoxide, which is actually used as fuel. As a result, SOFCs can use gases made
from coal or other gas-fired fossil fuels.
High-temperature operation has disadvantages. It results in a slow start-up and requires
significant thermal shielding to retain heat and protect personnel, which may be
acceptable for utility applications but not for transportation and small portable
applications. The high operating temperatures also place stringent durability
requirements on materials. The development of low-cost materials with high durability at
cell operating temperatures is the key technical challenge facing this technology.
Currently available unpressurized SOFCs provide electric efficiencies in the range of
45%. Argonne National Laboratory suggests that pressurized systems could yield fuel
efficiencies of 60%. Power generating efficiencies could reach 60% to 85% with use of
waste heat to facilitate cogeneration.
Solid Oxide Fuel Cell
This system, developed by
SiemensWestinghouse, is the
world’s first fuel cell/gas turbine
hybrid., It began operation at the
University of California–Irvine
in May 2000. It integrates a
microturbine generator with a
solid oxide fuel cell and
produces 220 kW at a system
electrical efficiency of 58%.
Future SOFC/gas-turbine hybrid
plants are expected to have
electrical efficiencies of 60%–
70%.
Photo courtesy of
SiemensWestinghouse
Electrochemical Reactions
Anode:
H2+O2- ⇒ H2O +2eCathode:
½O2+2e- ⇒ O2Cell:
H2+½O2 ⇒ H2O
Basic schematic showing equipment and purpose of equipment
Figure 1. shows a basic fuel cell system. The key components of the system are as follows:
-Fuel
-Fuel cell
-Battery (provide reserve power)
-DC Bus
-Rectifier (convert DC to AC)
-AC distribution
Fuels Table
Fuel
Physical Properties
Regulations
MSDS Links
Hydrogen,
Gaseous
Colorless, Odorless, Tasteless and NonToxic; 14 times lighter than air;
Flammable range 4%-75%
Light, volatile, colorless, distinctive odor,
Toxic; The 64%/36% methanol/water
mixture by weight used in methanol
reformers is flammable
Naturally occurring gas consisting mostly
(95%) of Methane; 1.7 times lighter than
air; Flammable range 4%-16%
Colorless, Tasteless gas with an odorant
added; Non-Toxic; 1.5 times denser
than air; Flammable range 2.15%-9.6%
OSHA
29CFR1910.103
MSDS
OSHA
29CFR1910.106
MSDS
NFPA30
OSHA
29CFR1910.101
MSDS
NFPA54
OSHA
29CFR1910.110
MSDS
NFPA30,
NFPA58
Methanol
Natural Gas
Propane
Applicable
Code(s) for
Fuel Storage
NFPA55,
NFPA2
Notes: Hyperlinks on first column linked to requirements for fuel storage and fuel cell design and installation, which cover
C&S, OSHA, EPA, DOT, DOE resources, current FEMA and Zoning requirements
Summary of Codes and Standards Applicable to Stationary Fuel Cell Installations
Title of Code/Standard
2015 International Mechanical Code (IMC)
Contact
ICC
Regulates and controls the design, construction, installation, quality of
materials, location, operation and maintenance of use of mechanical
systems.
2015 International Fuel Gas Code (IFGC)
ICC
Regulates and controls the design, construction, installation, quality of
materials, location, operation and maintenance or use of fuel gas systems.
2015 International Fire Code (IFC)
ICC
The purpose of the IFC is to establish the minimum requirements consistent with
nationally recognized good practice for providing a reasonable level of like
safety and property protection from the hazards of fire, explosion or dangerous
conditions in new and existing buildings, structures and premises.
2015 International Residential Code (IRC)
ICC
Provides minimum requirements to safeguard life or limb, health and public
welfare for one and two family occupancies and townhouses.
2015 International Building Code (IBC)
ICC
Establishes the minimum requirements to safeguard the public health, safety and
general welfare through structural strength, means of egress facilities, stability,
sanitation, adequate light and ventilation, energy conservation, and safety to life
and property from fire and other hazards attributed to the built environment.
2015 International Plumbing Code (IPC)
Regulates and controls the design, construction, installation, quality of
materials, location, operation and maintenance or use of plumbing
equipment and systems.
ICC
Title of Code/Standard
NFPA 70 (NFPA 70)
Contact
NFPA
2014 National Electric Code
§692, Fuel Cell Systems—Requirements for the installation of fuel cell power
systems, which may be stand-alone or interactive with other electrical power
production sources and may be with or without electrical energy storage such as
batteries.
NFPA 55
NFPA
Gaseous Hydrogen Systems
Covers the general principles recommended for the installation of gaseous
hydrogen systems on consumer premises where the hydrogen supply to the
consumer premises originates outside the consumer premises and is delivered by
mobile equipment.
Liquefied Hydrogen Systems
Covers the general principles recommended for the installation of liquefied
hydrogen systems on consumer premises where the liquid hydrogen supply to the
consumer premises originates outside the consumer premises and is delivered by
mobile equipment.
NFPA 54 - National Fuel Gas Code
NFPA
Natural Gas Systems
Applies to the installation of fuel gas piping systems, fuel gas utilization
equipment, and related accessories.
NFPA 58 -Liquefied Petroleum Gas Code
NFPA
LPG
Applies to the highway transportation of liquefied petroleum gas and to the
design, construction, installation and operation of all liquefied petroleum gas
systems.
NFPA 853-2013 (NFPA 853)
NFPA
Standard for the Installation of Stationary Fuel Cell Power Plants
Applies to the design and installation of 1) a singular prepackaged self-contained
power plant unit;
2) combination of prepackaged self-contained units; 3) power plant units comprised
of two or more factory matched modular components intended to be assembled in
the field.
ASME
AMSE Boiler and Pressure Vessel Code
The International Boiler and Pressure Vessel Code establishes rules of safety
governing the design, fabrication, and inspection of boilers and pressure vessels and
nuclear power plant components during construction.
Title of Code/Standard
ANSI FC1
Contact
CSA
Standard on Stationary Fuel Cell Power Plants
Provides fire prevention and fire protection requirements for safeguarding
life and physical property associated with buildings or facilities that employ
stationary fuel cells or all sizes.
ICC — International Code Council, 5203 Leesburg Pike, Suite 600, Falls Church,
VA 22041, (703) 931-4533, www.iccsafe.org
NFPA — National Fire Protection Association, 1 Batterymarch Park. Quincy, MA
02269-9101, (800) 344-3555, www.nfpa.org
ASME — ASME International, Three Park Avenue, New York, NY 10016, 1-800-843-2763, or
1-973-882-1167, Fax: 1-973882-1717
UL — Underwriters Laboratories Inc., 333 Pfingsten Road, Northbrook, IL 60062-2096, Tim
Zgonena, (847) 272-8800 Ext.
43051, timothy.p.zgonena@us.ul.com
CSA — CSA International, 8501 E. Pleasant Valley Road, Cleveland, OH
441310-5575, (216) 524-4990 Ext. 8303, http://www.cas-international.org
Basic Principles of Fuel Cell Safety
The fuel cell engine uses hydrogen (directly, or indirectly produced from other fuels) to
electrochemically produce electrical power. The hazards of fuels, electrical power, machinery, etc. are
well understood and addressed by multiple safety standards and codes for fuel cells and their fuels.
The important safety categories that apply to fuel cell power systems are: Flammability, Hazardous
material, Ventilation, Mechanical, Electrical, and Electromagnetic.
Fuel cells do not employ radioactive components or materials, nor produce ionizing radiation.
The following categories are addressed by codes and standards for product safety:
o
Flammability - Flammable Gas and Liquid
- safety concerns: potential fire, explosion risk
o
o
Protection against fire or explosion hazard addressed by FC 1 for stationary fuel cell systems
and FC 3 for portable applications, and repeated in NFPA 853.
o
Fire prevention, pressure relief, and leakage containment or venting of fuel storage per
NFPA 2, 30, 55, 58, 853.
Hazardous Material
- safety concerns: inhalation, skin exposure, oral poison, etc.
o
o
Occupational Health & Safety Organization (OSHA) per Code of Federal Regulations 29, Part
1910 (29CFR1910).
Ventilation and Make-up air
- safety concerns: potential asphyxiation, removal of excess heat
o
o
room ventilation & fuel supply ventilation per OSHA (29CFR1910) and International Building
Code (IBC)
o
NFPA853 ventilation requirements for fuel cell power systems.
Mechanical
- safety concerns: personal injury hazard due to contact with moving parts (fans & louvers), compressed
gas
o
o
o
Addressed by FC 1 & FC 3:

physical inspection & protection (IEC/ANSI/NEMA 60529 rating: IP2x for indoor or
outdoor applications).

compliance to NFPA 79 for machine safety.
compressed gas rupture risk is addressed by International Fuel Gas Code (reflected by state
fire codes), and NPFA 55.
Electrical
- safety concerns: shock hazard, discharge hazard, possible ignition source.
hazardous voltages, currents, energy - if touched, insulation & critical spacing to prevent accidental
discharges & resulting molten material, and possible ignition sources for flammable gas.
o
Addressed by FC 1 & FC 3 for power generator

o
o
compliance to IEC/UL 60950-1 for electrical spacing & insulation.
Installation per NFPA 70, especially Article 692 for fuel cell systems.
Electromagnetic
- safety concerns: unexpected interference and loss of safety controls due to Radio Frequency (RF)
energy
RF radiated emissions (ElectroMagnetic Compliance - EMC)
o
EMC: RF radiated emissions are addressed by the Federal Communications Commission
(FCC) per Code of Federal Regulations 47, Part 15.
Fuel Supply Considerations
Fuel cells convert the chemical energy of a fuel to electrical energy. The fuel cell operates for as long as
fuel is available. Hydrogen is often the chemical energy source for the system; alternatively, hydrogen
carrying substances such as methanol, natural gas, propane, and ammonia can also be used, depending
on the fuel cell design. The choice of catalyst in the fuel cell determines whether a given fuel can be
used directly, or must be processed (reformed) before the core electrochemical reaction takes place.
The fuel cell design also determines the operating characteristics, such as start-up time and loadfollowing ability – some designs are better aligned than others to wireless and other critical ICT power
requirements.
Compressed hydrogen and liquid methanol are commonly used today by stationary fuel cells for backup
power at cellular sites (10 kW or less). The vast majority of deployments are PEM fuel cells that require
pure hydrogen which can be supplied directly or reformed (e.g. from methanol) on site. Direct Methanol
Fuel Cell (DMFC) technology is also used today for backup power, but in smaller numbers. As the name
suggests, DMFC technology is designed to use methanol directly without a reformer. Natural gas is used
today in larger prime power fuel cell power plants (100 kW or more, e.g. for large servers), and both
natural gas and propane are used by micro-Combined Heat and Power (CHP) fuel cells. Smaller (5kW or
less) Solid Oxide Fuel Cell (SOFC) technology, used mainly in prime power applications, can flexibly
accept any of the fuels mentioned above. Natural gas, propane, and ammonia fuel cells for telecom
backup power are in active development.
The fuels chosen for the scope of this document are hydrogen, methanol, natural gas, and propane,
based on the applicability of fuel cells that use these fuels for wireless and other critical ICT
infrastructure and on availability of commercial products.
Hydrogen
Hydrogen is the most abundant element in the universe, but stable molecular hydrogen gas is rare on
earth because it is so diffusive and buoyant (characteristics that also make it a safe fuel). Hydrogen is
found abundantly in many chemical compounds (e.g. water), and is easily manufactured from feedstock
fuels such as methane. It is also often produced as a by-product of chemical processes, and can be
created as a form of renewable energy through electrolysis and reformation of biogas. Hydrogen fuel
cells have the simplest design, but there is a tradeoff with fuel logistics, as hydrogen is often stored and
transported at high pressure. Fuel cells typically require a hydrogen purity of 99.95%.
Sources
In addition to being a source of energy, hydrogen is used in a number of industries today: float glass
manufacturing, metal production and welding, chemicals, refining, automotive and transportation
equipment, and aerospace and aircraft. The primary source of hydrogen for these industries is industrial
gas companies, and several other options are available as listed below:

Industrial Gas Companies
Industrial gas companies are well represented across the continent, and have the widest selection of
delivery options. Most offer both gaseous and liquid hydrogen. As a compressed gas in smaller
quantities, hydrogen can be sourced in a variety of cylinder sizes and bulk packs. For larger quantities,
gaseous hydrogen can be delivered in tube trailers. When cooled to liquid form, hydrogen can be
transported in tanker trucks and transferred to bulk liquid tanks; however, it needs to be converted to
gaseous form before use in fuel cells.
A sampling of industrial gas companies supplying hydrogen include: Air Liquide, Air Products, Airgas,
Linde, and Praxair.

Hydrogen Vehicle Re-Filling Stations
The number of hydrogen re-filling stations continues to grow as the infrastructure is being established
for hydrogen fuel cell vehicles. In addition to vehicles, these stations could sell hydrogen to anyone who
is licensed and equipped to re-fill hydrogen storage containers.
http://commons.wikimedia.org/wiki/File:Hydroge
n_fueling_nozzle.jpg
Public domain; author: EERE

http://cafcp.org/getinvolved/stayconnected/blog/cec_ann
ounces_funding_28_hydrogen_stations
Figure x. Hydrogen re-filling station.
Hydrogen Re-Sale by Heavy-Use Industries
In addition to automotive, the material handling industry is becoming a significant consumer of
hydrogen as warehouses and industrial facilities migrate from battery-driven and combustion-enginedriven forklift trucks to new hydrogen alternatives. These facilities need to store a sizable amount of fuel
– in liquid form if the truck fleet is large enough – and the managers of that fuel could re-sell some of
the hydrogen for backup power, providing an alternate source of revenue.
http://www.lindeus.com/en/innovations/hydrogen_energy/hydro
gen_energy_applications/forklifts.html
Figure x. Hydrogen fuel cell forklift being refueled at warehouse facility.

Chemical Plants Producing Hydrogen as Waste By-Product
Industrial facilities, such as sodium chlorate, chlor-alkali, and caustic soda plants, often produce massive
quantities of by-product hydrogen that can potentially be captured and sold for other purposes, such as
fuel cell backup power.
As an example, in India, Aditya Birla Group operates a caustic soda plant in Nagda, Madhya Pradesh. Byproduct hydrogen from this process is captured, purified, stored in cylinders, and used to power fuel
cells in a cellular network operated by IDEA Cellular, part of the Aditya Birla Group.
The IWHUP project featured a Combined Heat and Power fuel cell powered by hydrogen recovered from
a nearby sodium chlorate plant. http://www.americanoilinvestments.com/articles/Oil-GasNews_4618.html
http://www.htec.ca/#!history/c588
Figure x. Waste hydrogen capture facility. Photo courtesy HTEC.

Gas Pipelines
Hydrogen gas pipelines are often found in oil refinery zones such as in Southern California and Texas.
This continuous flow of fuel is ideal for fuel cells that produce high power and/or run continuously.
http://commons.wikimedia.org/wiki/File%3AHydrogen
_pipelines.jpg
Public domain: EERE
Figure x. Section of hydrogen gas pipeline.
As an example, Toyota Motor Sales, USA, Inc. operates a 1.1 MW hydrogen PEM fuel cell at its Sales and
Marketing Headquarters in Torrance, CA. The fuel cell is used to satisfy peak and mid-peak power needs.
The pipeline that provides hydrogen to this fuel cell also supplies a nearby hydrogen fueling station
http://www.ballard.com/aboutballard/newsroom/news-releases/news10171201.aspx
Figure x. A 1.1 MW fuel cell at Toyota Motor Sales, USA, Inc. fueled by pipeline hydrogen.
Photo courtesy Ballard Power Systems, Inc.

Renewable Sources
Hydrogen can be produced renewably through the electrolysis of water, where electrolysis (and optional
compression) is powered by energy sources such as wind, photovoltaic panels, hydropower, biomass,
and geothermal.
A few examples of trials of electrolyzer/fuel cell systems are identified in the following link
http://fuelcellsworks.com/news/2014/07/03/hydrogen-production-systems-provider-acta-s-p-aannounces-commercial-update/
Although early in its development stage, manufacturing hydrogen from biomass is another alternative
for the renewable production of biomass1.
Fuel Delivery/Storage Options
Hydrogen is delivered and can be stored as a compressed gas, a liquid, or bonded in matter; however,
liquid hydrogen must be gasified before delivery to the fuel cell, and bonded hydrogen must be
released, as fuel cells consume hydrogen in gaseous form. Hydrogen is stored as a compressed gas at
the point of use.

Compressed Gas
Pressure vessels of various sizes, shapes, and composition are used for the transport and storage of
compressed hydrogen gas.
1
http://www.hydrogen.energy.gov/pdfs/51726.pdf
In small quantities, steel cylinder tanks are the most common form of delivered gaseous hydrogen, but
aluminum tanks are also available. The cylinders can also serve as the storage medium on site, and are
swapped when empty (or near empty). In this “cylinder swap” case, the cylinder tanks typically remain
the property of the fuel supplier, and a monthly rental fee is applied for each cylinder at the purchaser’s
site. Alternatively, a permanent installation of cylinders on site can serve as the storage medium, and is
refilled by transferring hydrogen from a delivery vehicle. In this “fill-in-place” scenario, the storage
medium is often purchased as a package with the fuel cell.
(a)
(b)
(c)
http://www.airgas.com/content/details
.aspx?id=7000000000234
Figure x.(a) Steel cylinders installed in a cabinet for individual cylinder service (photo courtesy Ballard Power
Systems, Inc), (b) Steel cylinders installed in a cabinet – manifolded together for “fill-in-place” service (photo
courtesy Air Products and Chemicals, Inc.), (c) sample range of steel cylinder sizes (photo courtesy Airgas).
In larger quantities, compressed hydrogen can be delivered in bulk trailers. Capacities for conventional
tube trailers typically range from about 25,000 – 140,000 scf (60 – 330 kg). A variety of advanced highpressure solutions are now available that can double capacity with the use of composite materials that
withstand higher pressures. The trailers can be used to refill on-site storage vessels or can be left on-site
as a form of storage. A monthly rental fee may apply if the storage asset remains the property of the
hydrogen vendor.
http://commons.wikimedia.org/wiki/File%3ACo
mpressed_hydrogen_tube_trailer.jpg
Public domain; author: EERE
(a)
(b)
Figure x.(a) Conventional steel tube trailer,
(b) trailer with 450 bar (6,500 psi) composite cylinder blocks (6 x 89 kg of hydrogen) (photo courtesy HTEC),
As mentioned above, cylinders made of high-strength carbon composite materials enable storage at
higher pressure, and increase the density of stored hydrogen. These cylinders can be manifolded
together in modular bulk packs, or installed as individual cylinders into hydrogen cabinets. Carbon
composite cylinders are not a standard offering from hydrogen vendors, so these assets are often
purchased rather than rented. Composite cylinders were developed primarily by the automotive
industry demanding lightweight, high-density hydrogen storage tanks for hydrogen fuel cell vehicles.
The lighter weight and higher pressure attributes make them attractive also for stationary applications
where weight and/or space must be minimized.
(a)
(b)
(c)
Figure x. (a) Cutaway of composite cylinder bulk pack (photo courtesy HTEC),
(b) Arrangement of composite cylinders in trailer from Figure x-1 (c) above (photo courtesy GTM Technologies),
(c) Composite cylinder installed in a wheeled cart to facilitate rooftop delivery (photo courtesy GTM Technologies).

Liquid Hydrogen
Transportation and storage of liquid hydrogen is an economical option for applications where large
amounts of hydrogen are consumed. As a fuel cell requires hydrogen in gaseous form, additional
infrastructure is needed at, or near, the point of consumption to convert liquid hydrogen to gaseous
hydrogen. At atmospheric pressure, hydrogen exists as a liquid below 33 K, but must be cooled to about
20 K (-253 ⁰C / -424 ⁰F) for it to exist in liquid state without evaporating. Storage and handling
procedures for cryogenic liquids must be employed.
Liquid hydrogen is transported by trailer trucks in large cryogenic tanks ranging in capacity from 7,500 to
13,000 gallons (28,400 to 49,200 L), which equates to about 2,000 to 3,500 kg of hydrogen. An example
is shown below of a cryogenic tanker trailer as well as a liquid hydrogen storage and gasification facility
at a site employing a fleet of fuel cell forklift trucks. The additional capital required for storage and
gasification of the liquid hydrogen is economical in warehouse facilities that deploy at least 40 fuel cell
forklift trucks. Although not common today, there may be applications where liquid hydrogen is
economical for stationary fuel cells that produce large amounts of power and/or experience heavy use.
http://hydrogentank.en.busytrade.com
/products/info/2087771/LiquidHydrogen-Transport-Truck-Tank.html
(I’m sure there’s an NREL photo to
replace this)
(a)
(b)
http://www.plugpower.com/Libraries/Documentation
_and_Literature/Whitepaper_Debunking_Hydrogen_F
uel_Cell_Myths.sflb.ashx
Figure x. (a) Liquid hydrogen transport tank, (b) Liquid hydrogen storage and gasification facility at a warehouse
deploying a fleet of fuel cell forklifts.

Advanced Hydrogen Storage Technologies
There are many new technologies being developed for hydrogen storage motivated primarily by the
growing number of hydrogen applications, including hydrogen fuel cell power generation. These new
technologies include, for example, metal hydrides, ammonia, formic acid, and carbon nanotubes, to
name just a few. As these technologies are in the development stage, they are not included here as
commercial options at time of publication, but industry is moving quickly.
Refueling
Hydrogen is refueled either by replacing or re-filling the storage container.

Storage Container Replacement
For hydrogen storage cabinets designed for cylinder swapping, individual cylinders are delivered to the
site by truck, and technicians move the cylinders to and from the storage location with hand trucks. In
some cases, bulk solutions are designed to be “drop-and-swap”, allowing a large amount of hydrogen to
be replaced in a short period of time if the site area is large enough to accommodate the heavy
equipment required.
http://h2bestpractices.org/storage/com
pressed_gas/storage_vessels/cylinderh
andling.asp
(Look for generic NREL photo)
(a)
(b)
Figure x. (a) Hand-truck for moving individual cylinders to/from storage location,
(b) “Drop-and-swap” of a bulk container of composite cylinders (photo courtesy HTEC).

Storage Container Refilling
Compressed hydrogen storage systems can be designed to be “fill-in-place”, allowing refueling from a
truck through a hose. This model avoids wasting any hydrogen remaining in cylinders that are swapped,
and as well allows heavy fuel storage vessels to remain in place. This model is suitable for accessible
sites in regions where there are trucks equipped to re-fill cylinders at high pressure.
http://www.hydrogen.energy.gov/pdfs/rev
iew12/h2ra006_maxwell_2012_p.pdf
Photo on Slide 18.
(a)
(b)
Figure x. (a) Fill-in-place delivery by a hydrogen bobtail truck to compressed hydrogen storage at a cellular site,
(b) Fill-in-place delivery by composite bulk storage cylinders on a trailer (photo courtesy GTM Technologies).
Liquid hydrogen storage tanks are always re-filled (as opposed to swapped), and refueling must be done
with attention to cryogenic procedures. For a fuel cell application, stored liquid hydrogen must be
converted to gaseous form before it can be used by the fuel cell.
Site Considerations
For ground-based sites, replacement and refilling modes are both viable options for refueling gaseous
hydrogen. The refilling mode is desirable as it avoids moving heavy storage containers; however, site
accessibility can limit its use. Although a slower and more labor intensive mode of refueling, cylinders
can be moved safely by hand-cart through spaces that cannot be navigated by a vehicle.
For rooftop sites, replacement and refilling modes are both viable options, but more challenging than
for ground-based sites. It is assumed in both cases that the hydrogen storage is on the roof with the fuel
cell, as there often is no suitable space available around the building at ground level or inside the
building. For the fill-in-place mode, if allowed by the building owner, hydrogen piping can be installed
from the storage tanks down the outside of the building to ground level where the delivery truck can
connect a refilling hose. For the replacement mode, cylinders (steel or carbon composite) can be taken
up an elevator, after which there may be some stairs to roof level. During a power outage or other times
when elevators are not operational, cylinders can be carried with a cylinder hand-truck up the stairwell
if the building is not too tall.
For both ground-based and rooftop sites, compressed gas fuel such as hydrogen is almost always stored
separately from the fuel cell cabinet, so compressed gas fuel cell systems tend to have a larger physical
footprint compared to liquid-fueled systems, where fuel can be stored in the base of the fuel cell
enclosure. Storing hydrogen in higher pressure carbon composite tanks can help to reduce the footprint
required for fuel.
Taking appropriate setback distances into account for hydrogen storage, the effective footprint (i.e. the
physical occupied footprint plus the clearance area required for regulatory compliance) of the hydrogen
solution tends to be the largest of available options.
Hydrogen is a very safe fuel for use on a rooftop, as it is the most buoyant of all gases (relative density of
0.0693 relative to air), and disperses quickly (diffusion coefficient2 of 0.61 x 10-4 m2/s, compared to
gasoline diffusion coefficient3 range of 0.006-0.02 x 10-4 m2/s). In the unlikely event of a leak, hydrogen
rises straight up into the open air and rapidly dilutes to noncombustible concentrations. The Lower
Flammability Limit (LFL) of hydrogen is 4%4, which is higher than the LFL of gasoline at 1.2%5.
Methanol
The methanol/water mixture used in fuel cells exists naturally as a liquid at room temperature and
atmospheric pressure, and typical blends freeze at around-73 ⁰C (-100 ⁰F). As it is a stable liquid, it can
be transported and stored in plastic or metal containers making fuel logistics simple. Methanol can be
used directly – for example, by DMFC and SOFC systems – or indirectly – for example, by PEM fuel cells
with a suitable reformer.
Sources
Pure methanol is one of the most widely distributed chemicals in the world used in numerous products
such as windshield washer fluids, automotive fuels, furniture refinisher, paint remover, windshield
deicer, and household cleaners/solvents, as examples. The water in the methanol/water mix must be
purified and de-ionized before blending with methanol at the prescribed ratio.

Methanol Sources
Methanol with the required degree of purity can be obtained from many sources worldwide. Please see,
for example, the list of member companies of the Methanol Institute (http://www.methanol.org/aboutus/member-companies.aspx).

Renewable Sources
Methanol can be produced renewably and sustainably through conversion of bio-mass. For example,
BioMCN6, a company in the Netherlands, produces and sells industrial quantities of “bio-methanol” that
is chemically equivalent to methanol manufactured conventionally, and meets IMPCA standards. The
process implemented by BioMCN converts crude glycerine, a residue from biodiesel production, into
2
http://www.hysafe.org/download/997
http://www.jocet.org/papers/012-J30011.pdf
4
Hydrogen density and LFL from http://www.hysafe.org/download/997
5
https://www.mathesongas.com/pdfs/products/Lower-(LEL)-&-Upper-(UEL)-Explosive-Limits-.pdf
6
http://www.biomcn.eu/
3
bio-methanol. The product is either physically shipped to consumers of the chemical, or alternatively,
BioMCN has established a certificate trading system whereby the sustainability rights of the biomethanol produced by BioMCN in the Netherlands are transferred to a chemical consumer, while the
chemical consumer sells back to BioMCN an equivalent amount of conventional methanol. The
certificate trading system saves freight costs and avoids unnecessary production of CO2 by transport of
bio-methanol.

Methanol/Water Blenders
For pre-blended fuel, the fuel supplier is responsible for sourcing methanol, sourcing or producing
water, and blending it such that the final product meets the requirements of the fuel cell.
One such company supplying methanol/water fuel under the brand name, HydroPlus™7, is Brenntag
Pacific, who can distribute the product throughout North America.8. The HydroPlus mixture is between
61-63% methanol by weight, which is approximately 70% methanol by volume. Other blending ratios
may apply to specific products or as required by local authorities.
Fuel Delivery/Storage Options
Generally, there are two methods for delivery of fuel: (a) deliver pre-blended fuel, (b) deliver pure
methanol. In the latter case, blending with water can be performed on site before transfer to the fuel
storage tank, or it may be blended internally within the system if it can provide its own water.
With either form of delivery, the storage medium for the fuel is very commonly a fixed tank that remains
on site. The tank may be internal – located within the envelope of the fuel cell solution, or external –
located outside the envelope of the fuel cell solution, but nearby.
(a)
(b)
Figure x. (a) Internal methanol/water tank (part of base),
(b) external tank supplying three 5 kW fuel cells electrically connected in parallel.
Both photos courtesy Ballard Power Systems, Inc.
Fuel can be delivered to the fixed tank in a variety of transportable container sizes:
7
8
HydroPlus™ is a trademark of Ballard Power Systems, Inc.
http://www.brenntagpacific.com/en/
(a)
(b)
(c)
(d)
Figure x. (a) 275 or 330 gallon Intermediate Bulk Container (IBC) totes,
(b) 55 gallon drums (4 per pallet), (c) 5 gallon pails, (d) 1 gallon jugs.
All photos courtesy Ballard Power Systems, Inc.
Alternatively, the external fuel tank can be swapped out, similar in concept to hydrogen cylinder
swapping. An IBC tote can be used for this mode of delivery. Common IBC capacities are 275 gallons
(1,040 L) and 330 gallons (1,250 L). Unlike the more common cylinder swapping for hydrogen fuel cells,
this method of fuel delivery is less common for methanol/water fuel cells. The tank can be swapped
while the fuel cell is inactive, or to avoid loss of availability, the tank may be hot-swapped with one or
more other tanks on a manifolded fuel supply.
Refueling
Once delivered to the site, the methanol/water fuel can be transferred to the storage tank by a variety
of mechanisms:

Fuel in smaller containers (1 gallon jugs and 5 gallon pails) can be poured directly into the fuel
tank with an appropriate spout or funnel to avoid spillage.

Fuel in larger containers (55 gallon drums and larger IBC totes) can be pumped out with AC or
DC-powered pumps, hand pumps or siphons, or tanker trunk with a hose.
(a)
(b)
(c)
Figure x. (a) AC powered pump,
(b) hand pumps and a jiggle siphon, (c) fuel delivery system in pickup truck with extendable hose,
All photos courtesy Ballard Power Systems, Inc.
Site Considerations
For ground-level sites, methanol fuel can be delivered and dispensed easily from containers such as
drums or pails or directly from a fixed-tank fuel truck if the truck can get close enough to the site to be
reached by hose.
For rooftop sites, liquid methanol/water fuel can be transported by elevator in drums, pails or jugs to
the top floor, after which there may be some stairs to roof level. During a power outage or other times
when elevators are not operational, fuel can be carried up the stairwell in pails or jugs, whichever is
more manageable for the service personnel.
As a liquid fuel, methanol/water has a higher energy density than a gaseous fuel, and so occupies less
volume, and can be integrated into the fuel cell cabinet, saving physical footprint. For quantities less
than 60 gallons9, there are no setback requirements, so the effective footprint can be very small,
particularly advantageous for rooftops where available area is scarce and expensive.
9
NFPA 30, Chapter 21.
The Lower Flammability Limit (LFL) of methanol is higher (6.7%10 by volume) than the LFL of all of the
other fuels considered here (see Summary Table x), meaning more of it needs to accumulate before it
can ignite. Methanol vapor density is slightly heavier than air (1.1111), but it disperses (with diffusion
coefficient12 of 0.15 x 10-4 m2/s, compared to gasoline diffusion coefficient13 range of
0.006-0.02 x 10-4 m2/s) 50% faster than propane and similar to natural gas. The volatility of methanol is
relatively low (32 kPa14 Reid Vapor Pressure (RVP) versus 48-62 kPa RVP for gasoline15). Methanol’s
relatively neutral buoyancy in air, low volatility, higher dispersion relative to propane and gasoline, and
flammability only at high concentrations are properties that contribute to its safety in general, and
particularly for rooftops.
Propane
Propane or Liquid (or Liquefied) Petroleum Gas (LPG) is a hydrocarbon that is widely distributed in a
variety of containers. In the US, propane is available in three grades: HD5, HD10, and Commercial,
where the constituents vary amongst the three grades:



HD5: At least 10% pure propane, and no more than 5% propylene and no more than 5%
butane/methane. All residential propane service is HD5, and it is also commonly used in
vehicles. Defined by GPA 2140: https://www.gpaglobal.org/publications/view/id/36/
HD10: Can contain up to 10% propylene, which can lead some engine components sticking.
“HD10” means fuel that meets the specifications for propane used in transportation fuel
found in Title 13, California Code of Regulations, section 2292.6.
Commercial: Less controlled mixture of propylene, butane, and methane; not used in vehicles.
The HD5 fuel grade is preferred for fuel cells16. It can be used directly – for example, by SOFC systems –
or indirectly – for example, by PEM fuel cell systems with a suitable reformer.
Sources
There are many propane dealers distributed throughout the US. Check local directories to find propane
dealers who offer HD5 grade propane fuel.
Fuel Delivery/Storage Options
Propane is already used at cellular sites today to fuel combustion-engine generators, and the propane is
stored in tanks most commonly external to the generator, but sometimes within the generator
enclosure. Fuel is delivered by bobtail truck to refill the tanks. The tank must be placed where it can be
10
http://www.engineeringtoolbox.com/explosive-concentration-limits-d_423.html
http://www.epa.gov/chemfact/s_methan.txt
12
http://www.gsi-net.com/en/publications/gsi-chemical-database/single/343.html
13
http://www.jocet.org/papers/012-J30011.pdf
14
http://www.methanol.org/Technical-Information/Resources/Technical-Information/Physical-Properties-of-PureMethanol.aspx
15
http://www.epa.gov/otaq/fuels/gasolinefuels/volatility/standards.htm
16
http://www.propanecouncil.org/uploadedFiles/REP_11071%20Propane%20Issues%20for%20Fuel%20Cell%20Ass
essment%20Vol1(1).pdf
11
accessed by the delivery truck. At sites where less energy is required (less required power and/or
operating time), a smaller tank may be used which could be replaced rather than refilled.
(a)
(b)
(c)
Figure x. (a) Vertical swappable propane tank, (b) Large-capacity fixed propane tank at cellular site,
(c) Propane bobtail truck used for delivery of fuel.
Refueling
At ambient temperatures, propane exists as a liquid only under pressure, so special nozzles and tank
hardware is required for the transfer of fuel to a tank. An example of bulk propane tank valves and
gauges is illustrated below, showing that both the liquid and vapor phases of propane must be
accommodated during refilling.
Figure x. Propane tank valves and gauges.
Site Considerations
For ground-level sites, propane tanks can be swapped, or the fuel can be dispensed directly from a
propane bobtail truck if it can get close enough to the site to be reached by hose.
For rooftop sites, propane can be transported by elevator in smaller tanks, after which there may be
some stairs to roof level. During a power outage or other times when elevators are not operational, fuel
can be carried up the stairwell in tanks sized to be manageable for the service personnel.
As propane exists as a liquid under pressure, propane has a higher energy density than a gaseous fuel,
and so occupies less volume. The fuel tank is often external to the system, which adds to the physical
footprint; however, the high energy content and volumetric density of propane enables long run times
in a relatively small fuel storage space. No setback requirements apply to tanks smaller than 125
gallons17; however, in prime power applications, larger tanks are desirable to reduce the frequency of
refueling visits.
Propane vapor is heavier than air (1.56 relative density18), so propane vapor tends to pool, and it tends
not to disperse well (diffusion coefficient19 of 0.10 x 10-4 m2/s, compared to gasoline diffusion
coefficient20 range of 0.006-0.02 x 10-4 m2/s). The Lower Flammability Limit (LFL) of propane is
comparable (2.1%21 by volume) to the LFL of gasoline. Leaks are in gaseous form as propane cannot exist
in liquid form at atmospheric pressure.
In practice, propane systems can be difficult to site on rooftops for the same reason that gasoline
combustion-engine generators are not permitted on rooftops – the safety concerns of heavier-than-air
vapors, low LFL, and high volatility are similar. Propane is common for residential and commercial use,
and siting of propane systems is straightforward for ground-based installations.
Natural Gas
Natural gas is a common fuel with residential, commercial, and industrial service for heat and power
generation. If it is available in piped form, power can be generated for as long as gas is supplied in the
pipes. Natural gas can be used directly – for example, by Molten Carbonate Fuel Cell (MCFC), Phosphoric
Acid Fuel Cell (PAFC), and SOFC systems – or indirectly – for example, by PEM fuel cells systems with a
suitable reformer.
Sources
Natural gas is widely available throughout the US, predominantly delivered by pipe infrastructure, but
also available in compressed gas cylinders.
Fuel Delivery/Storage Options
Piped natural gas does not need on-site fuel storage as it is dispensed on-demand from piped
infrastructure. The local gas company supplying the fuel must verify that the service is compatible with
the fuel cell in terms of pressure and available flow rate.
17
NFPA 58, Chapter 6.
http://www.engineeringtoolbox.com/gas-density-d_158.html
19
http://cafr1.com/Hydrogen_vs_Propane.pdf
20
http://www.jocet.org/papers/012-J30011.pdf
21
http://www.engineeringtoolbox.com/explosive-concentration-limits-d_423.html
18
Figure x. Outdoor natural gas connections.
As with hydrogen, natural gas can be stored and transported as a compressed gas in high-pressure
cylinders; however, this mode of storage/delivery is used predominantly by motive applications. For
stationary applications, if piped natural gas is not available, and if there are no issues with siting,
propane is used instead.
Refueling
As referenced above, piped natural gas does not need on-site fuel storage, so no refueling is required.
The supply of fuel continues as long as it is available from the gas supplier. Although piped fuel obviates
the need to visit sites to deliver fuel, security of gas supply is out of the control of the gas consumer.
Site Considerations
As no fuel needs to be transported, there are no special transportation considerations for rooftop sites
relative to ground-level sites.
Piped natural gas can be used both at ground-based sites and rooftop sites, as long as the infrastructure
is available, and the building owner and local authorities allow it; however, natural gas infrastructure is
often only present in residential and commercial buildings, so natural gas is a good option for rooftops,
but simply may not be available at standalone ground-based telecom sites. If natural gas service is
available, consultation with the gas company and landlord is advised to ensure that: (a) the gas service
meets the pressure/flow-rate requirements of the fuel cell, and (b) the landlord/other tenants agree to
share the gas supply.
Natural gas is lighter than air (0.55 methane/air relative density22), and its dispersion rate (diffusion
coefficient23 of 0.16 x 10-4 m2/s, compared to gasoline diffusion coefficient24 of 0.006-0.02 x 10-4 m2/s) is
comparable to that of methanol vapor. Natural gas leaks tend to rise in air, and disperse 8-27x faster
than gasoline. The Lower Flammability Limit (LFL) of methane (the principle constituent of natural gas) is
slightly lower (5%25 by volume) compared to that of methanol, and higher than the LFL of gasoline and
propane. The high buoyancy of natural gas, coupled with its relatively high LFL and good dispersion
properties are factors that contribute to its safety.
22
http://www.engineeringtoolbox.com/gas-density-d_158.html
http://cafr1.com/Hydrogen_vs_Propane.pdf
24
http://www.jocet.org/papers/012-J30011.pdf
25
http://www.engineeringtoolbox.com/explosive-concentration-limits-d_423.html
23
Fuel Comparison
Some properties of hydrogen, methanol/water, propane, and natural gas for fuel cells are compared in
the table below. Data reflect information at time of publication.
Hydrogen
Small Fuel Cell
Status26
Methanol/Water
Propane
Natural Gas
Commercial
Commercial
Early Commercial
Early Commercial
FC Module Size27
0.2-10 kW
0.3-7.5 kW
0.25-5 kW
0.25-5kW
Small Fuel Cell Vendors
Many
Few
Few
Few
Typical Usage
Backup power
Backup power
Prime power
Prime power
Fuel state
Compressed gas
Stable liquid
Liquid under pressure
Compressed gas
0.0693
1.11
1.56
0.55
4%
6.7%
2.1%
5%
n/a (gas)
32 kPa
n/a (gas)
n/a (gas)
30-102x faster
7.5-25x faster
5-17x faster
8-27x faster
Mode of transport
Steel or composite
cylinders
Plastic or metal totes,
drums, pails, jugs
Mode of storage
Steel or composite
cylinders
Integrated tank or
external metal tank
Mode of refueling
Cylinder swap or fillin-place
Pour or pump liquid
Portable tanks or bobtail
truck
Integrated tank or
external pressurized
tank
Swap tanks or refill with
propane-specific
nozzles/valves
Common sources of fuel
(who to call)
Industrial gas
companies
Density relative to
air28
Lower Flammability
Limit29
Reid Vapor Pressure30
Diffusion relative to
gasoline31
Minimum quality
Ground-based site
considerations
Rooftop-based site
considerations
99.95% industrialgrade hydrogen
Suitable given
sufficient space for
fuel storage respecting
setback limits
Safe given hydrogen
properties; fuel
logistics challenging,
especially when
Methanol/water
blenders (e.g. Brenntag
North America)
Methanol: IMPCA
specifications; Water:
ASTM 1125, ASTM
D5907, IMPCA 004-08,
ASTM D4517; 61-63%
methanol by weight
Integrated tank less than
60 gallons allows
deployment in tight
spaces
Safe given methanol
properties; liquid fuel
simplifies fuel logistics –
delivering to site and
Piped infrastructure
n/a
No refueling - direct
feed from piped
infrastructure
See local directory for
propane distributors
Determine supplier of
gas to a specific site
HD5
Contact gas
company/landlord to
assure adequate
pressure and flow rate
for application
Suitable given sufficient
space for fuel storage
May not find natural gas
service at all ground
sites
May be challenges due
to properties of
propane; small tank
delivery enables service
If natural gas service
available, no site visits
required for fuel
delivery; current
26
“Commercial” means products that are available for sale in meaningful numbers, are supported with service and spare parts, and have
evidence of deployment in significant numbers. “Early Commercial” means products that are available for sale, but no evidence yet of
deployment in significant numbers.
27 Modules can be cascaded for higher site power requirements.
28 For reference, typical gasoline density is 3-4 relative to air: http://tsocorp.com/wp-content/uploads/2012/12/Gasoline-Unleaded-Regular.pdf
29 For reference, compare to typical gasoline LFL of 1.2%: https://www.mathesongas.com/pdfs/products/Lower-(LEL)-&-Upper-(UEL)-Explosive-Limits-.pdf
30
For reference, compare to typical gasoline RVP of 48-62 kPa: http://www.epa.gov/otaq/fuels/gasolinefuels/volatility/standards.htm
31
For reference, diffusion coefficient of gasoline ranges from 0.006-0.02x10-4 m2/s: http://www.jocet.org/papers/012-J30011.pdf
elevator not available
carrying up to roof
to roof when elevator
not available
architectures more
suitable for prime power
than backup power
Table x. Comparison of fuel attributes.
Footprint vs. operating time with a 5 kW load is charted below for six different potential fuel options:






Hydrogen fuel cell, 8 cylinders, 300-series steel, 2,400 psi, swappable.
Hydrogen fuel cell, 16 cylinders, large steel, 3,000 psi, fill-in-place cabinet.
Hydrogen fuel cell, 8 cylinders, 90 L carbon composite, 5,000 psi, fill-in-place cabinet.
Hydrogen fuel cell with methanol/water reformer, 59 gallon internal tank (located within fuel
cell enclosure under fuel cell equipment – no incremental footprint for fuel)
Hydrogen fuel cell with methanol/water reformer, 275 gallon Intermediate Bulk Container
external tank.
Propane fuel cell with propane reformer, 125 gallon propane tank.
Figure x. Comparison of footprint vs. operating time with 5 kW load for six different fuel cell systems.
General Guidance on Site Selection
Site assessment and selection is the most critical components to ensuring that a fuel cell candidate site
can be carried through the entire design, permitting, and construction process. Fuel cell generators can
be located in metropolitan, rural, and remotely isolated locations. Any existing documentation such as a
property lines, construction drawings, and an
internet search can be a quick and efficient way to make an overall determination of existing conditions
of a site location. The physical site audit is where the most information can be collected about the
layout of a site, the existing conditions and proposed equipment, and the overall viability for the
installation of a fuel cell generator. During this process you should first document the exact location of
the project and any obstacles that may potentially affect the ability of a candidate site to be
constructed, fueled, or maintained for the life cycle of the fuel cell. These considerations should include
the use or storage of any alternative fuel types, generators, or other back‐up power equipment, and the
main utility or power supply.
Gathering as much information about the current operation and functionality of the equipment or
facility, along with taking a real time measurement of the actual DC or AC load will provide the
framework for determining the type, size, and runtime of a fuel cell system deployment. When siting an
area or location for a fuel cell generator it is important to consider the optimal installation location, but
to also investigate the surrounding areas and make considerations for how the property or adjacent
properties may be developed or utilized in the future. There are several national, state, and local
jurisdictional codes that must be adhered to when deciding the final location of a fuel cell generator.
Code compliance is not necessarily reflective of the type of fuel cell system being installed, but typically
is more influenced by the fuel type, quantity, storage and delivery pressure at which the fuel is kept
during standard operating conditions. Below is a list of the most common site conditions that must be
observed when evaluating the viability of a fuel cell generator.







Buildings and structures on the same property
Openings in adjacent buildings
Above ground and underground flammable or combustible liquid and gas storage
Ignition sources
Overhead electrical utilities
Public streets, walkways, and gathering areas
Property lines
The purpose of this guide is to provide a high level overview of fuel cell technology and hydrogen safety
with regard to site selection. This information is provided as reference material for the siting of
hydrogen fuel cell systems that will be reviewed by an authority having jurisdiction (AHJs), installation
contractors and end-user customers. This document will assist decision-makers in determining the
applicability of permitting for fuel cell system siting and installation. The siting of a fuel cell power
system depends on many variables relating to the power generation unit size, type of fuel source, and
safety compliance. A fuel cell power system and associated equipment, components, and controls shall
be sited and installed in accordance with the manufacturer’s instructions and meet the following
requirements:

Location, Capacity, Siting, & Setbacks
Siting Fuel Cell Power Systems: [NFPA853-2010 5.1]
o
Fuel cell systems shall be installed on a firm foundation capable of supporting the
equipment, components and physically protected.
o
It shall be located so the foundation of, and access to, associated components and the fuel cell power
system are above the base flood elevation.
The equipment should be resistant to rain, snow, ice, freezing temperatures, wind, seismic events and
lightning.
The selected site locations should allow for service, maintenance and emergency accessible to service
& fire department personnel.
The system shall be located so the power systems and components of a matched modular or fieldengineered fuel cell power system and their exhaust vent are separated from doors, windows, outdoor
air intakes, and other openings into a building.
Fuel cells shall be located 5 ft. away from flammable or combustible materials, hazardous chemicals,
high stacked materials and other fire hazard exposures.
It shall be located such that a fire or failure of one of the systems does not present an exposure hazard
to an adjacent fuel cell power system.
Fuel cell systems shall not be located in areas that are used or are likely to be used for combustible,
flammable or hazardous materials storage.
o
o
o
o
o
o
Outdoor Installations: [NFPA853-2010 5.2]
o
o
Do not direct exhaust vents onto walkways or pedestrian paths.
Fuel-bearing components should be located 15 ft. from building openings, including HVAC
intakes.
o
If fuel cell power system is 50kW or less, this is modified by Section 9.2 to: fuel-bearing components
located 10 ft. from building openings, including HVAC intakes, and exhaust outlets not directed onto
pedestrian walkways.
Indoor Installations:
o
o
o
o
[NFPA853-2010 5.3]
Fuel cell power systems in a room shall be separated from the rest of the building by floor,
wall, and ceiling (including piping seals and joints) with at least a 1-hour fire resistance
rating.
Key feature include fire doors, ventilation dampers and egress routes.
If fuel cell power system is 50kW or less, this is modified by Section 9.3 to: fuel cells supplied by
natural gas, propane, or fuel oil and located in residences do not require fire-rated separations.
Fuel cells supplied by methanol or other alcohol fuels and located in residences do not require firerated separations if meet requirements of Sections 9.3.6.1 through 9.3.6.4
For liquid fuel:
o
o
o
o
o
o
[NFPA853-2010 9.3]
Less than 5 gallons of liquid fuel is allowed within the entire system including piping, during all modes
of operation, standby, and shutdown.
Bulk fuel storage systems shall be located outside.
Solid pipe or tube, all-welded, soldered, or brazed construction shall be used for indoor piping up to
and through the fuel cell power system enclosure.
The fuel cell system requires leakage detection and automatic isolation of the indoor fuel piping from
the outdoor bulk fuel supply upon detection of fuel leakage (using pump stoppage, valve closure, or
other manufacturer supplied control).
Requires an automatic isolation valve at the tank for outdoor bulk fuel storage located at an elevation
above the fuel cell power system.
Liquid fuel systems shall be provided with curbing, diking, or drainage in accordance with NFPA 30,
Flammable and Combustible Liquids Code.
Rooftop Installations: [NFPA853-2010 5.4]
o
Any roofing material below and within 12 inches horizontally from the power system, or its
components shall be non-combustible, or have Class A rating per either ASTM E 108
Standard Test Methods for Fire Tests of Roof Coverings or UL 790 Standard Test Methods
for Fire Tests of Roof Coverings.
Hydrogen Fuel Safety
The fuel source utilized in a fuel cell power system is industrial-grade hydrogen. Compressed, bottled
hydrogen is the most readily available commercial source of industrial grade hydrogen and can be found
throughout the world and at over 2,500 locations in the U.S. Compressed hydrogen is a versatile fuel
having a wide operating temperature range. The telecommunications industry is currently deploying
systems to the field that incorporate a hydrogen storage and delivery system. This system is provisioned
for use with compressed hydrogen gas cylinders. When designing systems which store, distribute and
utilize hydrogen gas it is imperative to address the characteristics of hydrogen to ensure a safe operating
environment. Hydrogen is the lightest gas known, with a flammable range from 4% - 74% by
concentration (see Figure 1). It is useful to compare this to a known quantity. By way of comparison,
propane has a flammable range from 2.4% - 9.6%. Propane’s flammability concentration is nearly 2
times lower than that of hydrogen. While hydrogen has a wider flammability range, it can be reasonably
acknowledged that the more important metric is the lower flammability limit.
Figure 1
Hydrogen Storage System
The hydrogen storage cabinet utilized in a standard deployment is a passively ventilated enclosure open
to outside air. The electrical equipment installed in this cabinet is rated for use in a hydrogen
environment. While a leak is not likely to occur, the system is designed to ensure a safe operation if one
were to occur. Hydrogen is 0.0695 the density of air, or 14 times less than the density of air. The storage
system is designed to ensure that in the event of a hydrogen leak, the hydrogen gas is vented to
atmosphere and allowed to disperse. Hydrogen’s dispersion characteristics will ensure as distance from
the leak source increases, the density of hydrogen will quickly drop below the flammable limit. By
comparison, propane is denser than air at 1.5 times the density of air and will tend to fall or settle at
ground level. Propane may gather in low spots along grade and not disperse without the use of forced
ventilation. Hydrogen is colorless, odorless, tasteless and non-toxic. Therefore, it is necessary to utilize
gas detection equipment when using or handling hydrogen gas. These hydrogen sensors are capable of
activating and shutting the systems down at 7,500 ppm, or less than 1/5th the Lower Flammable Limit of
hydrogen, which is 40,000 ppm. When replacing gas cylinders in a bottle exchange storage system, it is
recommended that the use of handheld combustible gas detectors be used to verify that there is no
leakage. Hydrogen gas detectors are commercially available and affordable. Liquid soap solution also
works effectively to locate any leaks. Outdoor Enclosure utilizes stainless steel and/or brass connection
fittings. It is recommended that the use of non-sparking cylinder wrenches be used for connecting the
gas cylinder fittings.
Rooftop Installation of Hydrogen Fuel Cell Systems
Though a rooftop application may not be ideal for a diesel or propane generator, due to the possibility
of liquid fuel spillage issues, this application is ideal for a hydrogen fuel cell, since the hydrogen fuel is
much lighter than air. Any unintentional release or seepage of the fuel dissipates rapidly and simply
escapes into the upper atmosphere. A fuel cell system can be installed on a rooftop as a complete unit
including the fuel storage, or alternately, can be installed with the fuel cell equipment cabinet located
on the rooftop and the fuel storage cabinet located on the ground as a separated system. This design
may be preferred in some instances where delivery of the hydrogen fuel to the rooftop is unfeasible or
where the rooftop cannot bear the additional weight of the fuel storage vessels. In addition to the codes
and standards that are relevant in general site selection and installation, the document, NFPA 853,
Standard for the Installation of Stationary Fuel Cell Power Systems, specifically addresses rooftop
installations in Chapter 5, “Siting and Interconnections, Section 5.4, Rooftop Installation”. The extent of
the NFPA reference is to ensure that the rooftop material under the fuel cell system and within 12
inches horizontally is non-combustible, or that it has a Class A rating. It could be suggested that a metal
plate, grate or raised platform, concrete or other such stable and nonflammable base be used beneath
the fuel cell system when installed on a rooftop to meet this requirement. Otherwise, the installation is
considered an outdoor installation. The International Fire Code (IFC) and International Building Code
(IBC) consider this an outdoor application with setback to exposure requirements listed in table 3504.2.1
of Chapter 35 of the IFC. Another important consideration is the delivery of the hydrogen cylinders to
the system by the gas supplier. In our experience, the use of a service elevator is the preferred method
for delivering compressed gases to rooftops. Compressed gases are delivered in this fashion on a regular
basis to laboratories, medical offices, and other commercial facilities located above the ground floor. If a
service elevator is not available, a public elevator or other similar means is typically acceptable. Contact
the local gas provider for additional recommendations. As stated in the general discussion on
installation of fuel cells, the final decision regarding acceptable placement of a fuel cell system and
hydrogen storage ultimately resides with the customer and the local AHJ.
Recommended Setback Distances
As a standard practice, we offer the following hydrogen storage setback distance/clearance
recommendations shown in Figure 2. Which are based on fuel cell industry recognized practices and
cross-referenced with the International Fire Code Chapter 35. The IFC is recognized by most AHJ’s to be
the controlling code for flammable gases. These manufacturer’s recommendations are also in alignment
with the Hydrogen Executive Leadership Panel (HELP) document titled, “Site Evaluation Worksheet for
Flammable Gas Storage; Stationary Fuel Cells”. The Hydrogen Executive Leadership Panel is a joint
initiative of the National Association of State Fire Marshals (NASFM), the Research and Innovative
Technologies
Administration of the U.S. Department of Transportation, and the International Consortium for Fire,
Safety, Health and the Environment and can be found at the following website:
http://www.nasfmhydrogen.com/.
These recommendations are offered for the convenience of the customer; however, ultimately it is the
responsibility of the customer and/or the AHJ to select the setback distances which are both appropriate
and reasonable. Note that the recommended setback distances shown in Figure 2 are intended to
extend from the hydrogen storage cabinet /or system to the type of specific exposure. In issuing and
making this document available, is not intended to render a professional or other services for or on
behalf of any person or entity. This document makes no guarantee or warranty as to the accuracy or
completeness of any information within the following table.
General Criteria for Fuel Cell Siting
Site Evaluation Worksheet for Flammable
Gas Storage Stationary Hydrogen Fuel Cells
Typical hydrogen
storage
criteria Building
for Controlling
Code
Setback CodeSetback
2010 editions
of thesiting
International
Code, International
Mechanical
quantities and
lessInternational
than 4,226 Fuel
standard
cubic
feet
Gas Code, which have references to the International Fire
<4,226 scf
4,226 to
(scf) and 4,226 to 21,125 scf. Interpretation by
Code.
Buildings
on the same
Non-rated(AHJ) will IFC Table 3504.2.1
5 ft.
10 ft.
the Authority
Having Jurisdiction
21,125
c
construction or
determine final setback distances.
property
scf
2-hour
construction
IFC
Table
3504.2.1
0
ft.
5
ft.
openings within 25 ft.
and no openings
4-hour
construction
IFC Table 3504.2.1
0 ft.
0 ft.
within 25
ft.
and
Underground flammable or combustible liquid
Recommend
5 ft.
10 ft.
no openings within 25
storage,
ft.
Ignition sources (including appliance
burner
Recommend
5 ft.
10 ft.
distance to vent or fill openingb
igniters, hot work and hot surfaces capable of
Overhead
electric vapors)b Overhead electric wire Recommend
5 ft.
10 ft.
ignitingbflammable
utilities
Overhead bus, trolley Recommend
5 ft.
10 ft.
or train wire
Public streets, public alleys or public ways
IFC Table 3504.2.1
5 ft.
10 ft.
Distance to lot lines of property that can be built IFC Table 3504.2.1
5 ft.
10 ft.
uponvegetation and combustible materialsc
Dry
IFC 2703.12 / 2704.11 15 ft.
25 ft.
Diked, distance to dike Recommend
5 ft.
10 ft.
Above ground
Not
diked,
distance
Recommend
5
ft.
10 ft.
flammable or
to tank
combustible liquid
Additional
flammable gas storage areasc
IFC Table 3504.2.1
5 ft.
10 ft.
b
storage
a. The minimum required distances shall not apply when fire barriers without openings
or penetrations having a minimum fire-resistance rating of 2 hours interrupt the line
of sight between the storage and the exposure. The configuration of the fire barrier
shall be designed to allow natural ventilation to prevent the accumulation of
hazardous gas concentrations.
b. These distances are recommended based upon the distances contained within IFC
Table 3504.2.1. c. These distances are specified in the International Fire Code, 2010
edition.
Revision Date: June 25, 2010
Narrative:
There are questions regarding minimum setback requirements for hydrogen fuel storage. Please accept
these example calculations as a reasonably allowable “minimum distance” for fuel storage setbacks for
the quantity of hydrogen storage at 8,000 scf, with a storage pressure of 3,000 psi. “Exposures” noted in
Figure 3 for the HSM (Hydrogen Storage Module) supporting the Fuel Cell system(s) under your
authority. This table of calculated sited requirements is a Reference to Chapter 10, Gaseous Hydrogen
Systems, NFPA 55, 2010 Edition.
Discussion:
As allowed in section 10.3.2.2.1.1, paragraph (C), equations will be used to determine the actual
setbacks for all 16 “Exposures” expressed in Chapter 10 of NFPA 55, 2010 Edition. Using equations in
table 10.3.2.2.1.1 (B) Separation Distance Based on Alternative Pipe or Tube Internal Diameters, we have
determined the allowable setbacks resulting for ¼ tubing at pressures >250psi to ≤ 3000psi.
There are two tubing diameters in this discussion;
1. The high pressure fuel lines located inside the fuel storage system (Hydrogen Storage Module)
2. The low pressure fuel line outside the Pressure Control Manifold that supplies hydrogen to the
ReliOn® Fuel Cell System.
The high pressure fuel line located inside the HSM is constructed of ¼ x 0.035 WT stainless steel tubing.
The service pressure for the fuel lines in the HSM is 3000psi maximum. The low pressure fuel line
located outside of the HSM is constructed of 3/8 x 0.035 WT fuel line tubing. The fuel line from the
*HSM to the fuel cell system has an operating pressure <10psi thus is not applicable to this Chapter and
not relevant for the setback distances in this case.
For discussion sake however, the equations provided in Chapter 10 allowed by section 10.3.2.2.1.1,
paragraph (C), were used for the fuel line tubing outside the HSM; the setback calculations for the
>250psi to ≤ 3000psi formula using the ¼ inch tubing supersedes the lower pressure 3/8 fuel line tubing
outside the Hydrogen Storage Module directly supplying hydrogen to the ReliOn Fuel Cell System.
As an example, provided in Example 3 is the equation and resulting calculation for the actual setback for
“note” (a) Exposure (1) Lot lines. The formula is called out on page 55-45 of NFPA 55, 2010 Editions
under table 10.3.2.2.1.1 (B) for >250psi to ≤ 3000psi.
Example 1:
Solving for Lot lines greater of a or b the minimum distance would be as follows;
Note (a) Da = 0.73903d0.99962
d = the tubing ID in millimeters or in case is 4.572 mm (0.180 inches) derived by subtracting the wall
thickness (multiplied by 2) from the OD of the tube.
Da = 0.7390(tubing ID in millimeters) 0.99962
Example 1 Result:
Da = 0.7390(4.572)0.99962 = 3.35 meters or 11 ft.
The allowable minimum distance setback for “Exposure” (1) Lot lines at 11 feet is result of whichever is
greater of note (a) or (b) as allowed in the equation in Table 10.3.2.2.1.1 (B) Separation Distance Based
on Alternative Pipe or Tube Internal Diameters on page 55-45 of NFPA 55 2010. The formula for note (b)
is provided in Table 10.3.2.2.1.1 (B).
Summary:
The minimum setback allowed is the greater of the a or b calculation. The note (b) result is 5.46 feet so
in this case, the note (a) result of 11 feet would be your minimum distance setback for Exposure (1) Lot
lines. There are 16 Exposures noted in Chapter 10 of NFPA 55, 2010 Edition. For your convenience,
provided below in FIGURE 3 are the minimum allowable setback distances in Feet (ft.) resulting from the
equations allowed in section 10.3.2.2.1.1 paragraph (C). It us suggested that you confirm the below
setback values and this information is available in Chapter 10 of NFPA 55, 2010 Edition
Exposure
(1) Lot Lines
(2) Exposed Persons…
(3) Buildings and structures…
(4) Openings in buildings…
(5) Air intakes…
(6) Fire barrier walls…
(7) Unclassified…
(8) Utilities…
>250psi to ≤ 3000psi (in ft.)
11
4
d = 5, e = 5, f = 5
a = 11, d = 5
11
5
15
5
(9) Ignition…
(10) Parked cars
(11) Flammable gas storage…
(12) Aboveground vents…
(13) Hazardous materials…
(14) Hazardous materials…
(15) Ordinary combustibles…
(16) Heavy timber…
11
11
d = 5, b = 5.5
5
5
5
5
5
FIGURE 3
Comparison of Fuel Cell Technologies to Other Power Generation
Technologies/Cost Comparison of Backup Power Technologies
Hydrogen
10 kW
Outdoor
Enclosure
H2 Fuel Cell
Hydrogen
10 kW
Indoor rackmount
H2 Fuel Cell
Diesel
50 KVA
Outdoor
installation
Diesel genset
w/ ATS
Combustion
Engine
Fuel storage
in base
140 gal subbase tank
70 Operating
Hours
Batteries
10 kW
Outdoor
installation
VRLA Battery
No Reformer
No Reformer
Fill-in-Place
(FIP) Storage
FSM 16 - 285
kWh
28.5
Operating
Hours
Outdoor FIP
Storage
FSM 16 - 285
kWh
28.5
Operating
Hours
Equipment Cost
$
50,000
$
45,000
$
30,000
$
72,000
Federal Tax
Credit
State Credits
$
(15,000)
$
-
$
(13,500)
$
-
$
$
-
$
$
-
Permitting/Insta
llation
$
13,500
$
13,500
$
18,000
$
15,000
TOTAL FIRST
COST
$
63,500
$
58,500
$
48,000
$
87,000
Annual
Maintenance &
$
700
$
700
$
5,000
$
4,500
Energy
Storage
4 x 420 Ah
8 Operating
Hours
Capital
Cost
Operatin
g Costs
Fuel
Lifecycle costs after 1 year
Lifecycle costs after 5 years
Lifecycle costs after 10
years
$
49,200
$
52,000
$
55,500
$
45,700
$
48,500
$
52,000
$
53,000
$
73,000
$
98,000
$
91,500
$
109,500
$
132,000
10 Kw Backup
Methanol/Wate
r
5 kW
Outdoor
Enclosure
H2 Fuel Cell
Diesel
Batteries
5 kW
Outdoor
installation
VRLA Battery
40 Operating
Hours
25 KVA
Outdoor
installation
Diesel genset
w/ ATS
Combustion
Engine
Fuel storage in
base
26 gal sub-base
tank
30 Operating
Hours
Equipment Cost
$
25,000
$
25,000
$
36,000
Federal Tax Credit
$
(7,500)
$
-
$
$
-
$
$
-
$
$
$
Methanol/wate
r Reformer
Internal Storage
Tank
59 gal - 200 kWh
Energy Storage
2 x 420 Ah
8 Operating
Hours
Capital
Cost
State Credits
Permitting/Installa
tion
10,000
16,000
10,000
TOTAL FIRST COST
$
35,000
$
41,000
$
46,000
Annual
Maintenance &
Fuel
$
300
$
5,000
$
2,250
$
27,800
$
29,000
$
30,500
$
46,000
$
66,000
$
91,000
$
48,250
$
57,250
$
68,500
Operating
Costs
Lifecycle costs after 1 year
Lifecycle costs after 5 years
Lifecycle costs after 10 years
5 Kw Backup
Natural Gas
5 kW
Outdoor Enclosure
H2 Fuel Cell
Natural Gas
Reformer
Piped Natural Gas
Piped supply
Capital Cost
Diesel
25 KVA
Outdoor installation
Diesel genset
Combustion Engine
External tank
500 gal sub-base
tank
Monthly refueling
Equipment Cost
$
56,000
$
30,000
Federal Tax Credit
$
(15,000)
$
-
$
$
-
Permitting/Installation
$
25,000
$
20,000
TOTAL FIRST COST
$
81,000
$
50,000
Annual Maintenance &
Fuel
$
5,100
$
25,400
$
71,100
$
91,500
$
117,000
$
75,400
$
177,000
$
304,000
State Credits
Operating
Costs
Lifecycle costs after 1 year
Lifecycle costs after 5 years
Lifecycle costs after 10 years
5 Kw Guide
Cummin http://www.cumminspower.com/w
s DGCA ww/Commercial/Diesel/d-3423.pdf
Standby
Prime
kW (KVA)
kW (KVA)
40 (50)
36 (45)
Lo 1/ 1/ 3/4 Full 1/4 1/2 3/4 Full
ad 4
2
US, 1.2 1.8 2.5 3.3 1.2 1.7 2.4 3.0
gp
h
L/h 5
r
7
9
12
5
6
9
11
Ge
ner
ic
Lo 1/ 1/ 3/4 Full
ad 4
2
US, 1.5 2.2 3.0 4
gp
h
http://www.cumminspower.com/w
ww/Commercial/Diesel/s-1012.pdf
14 gallon
0
tank
35 hrs at
10
0%
47 hrs at
75
%
64 hrs at
50
%
93 hrs at
25
%
Est 2
im
ate
70
gal 10kW DC + rectifier
/hr loss + other AC
hrs
MQ Power
DCA25SSIU3C
Sta 27 KV
nd
A
http://www.multiquip.com/multiquip/pdfs/SuperSilent_25_150_Spec_
Sheet_V2_0912_DataId_91330_Version_1_DataId_295333_Version_1.p
df
Pri 25 KV
me
A
by
22
k
W
Lo 25 50
ad % %
gal 0.5 0.8
/hr 8
5
L/h 2.2 3.2
r
26
15.
7
21.
5
30.
6
44.
8
Pri
me
20
75
%
1.2
1
4.6
kW
10
0%
1.6
6
6.3
gal
ta
nk
hrs at
10
0%
hrs at
75
%
hrs at
50
%
hrs at
25
%
50 gal
80. /yr
8
4
US
D/
gal
20 US
32 D/
3.2 yr
DG Specifications
Po
10
kW
3
US
12V
we
r
Vol
tag
e
Cur
ren
t
155
FT
Batt
48
V
208
.33
33
A
1
stri
ng
2
stri
ngs
3
stri
ngs
4
stri
ngs
$7,
208.
333
33
104.
166
67
69.4
444
44
52.0
833
33
12
A/s
trin
g
A/s
trin
g
A/s
trin
g
A/s
trin
g
D/
Ah
US
D/
Ah
<
0.5
hr
1
hr
1.5
hrs
2
hrs
bloc
k
48V
string
208
.33
33
208
.33
33
208
.33
33
208
.33
33
A
tot
al
A
tot
al
A
tot
al
A
tot
al
104
.16
67
208
.33
33
312
.5
Ah
Exp
ect
ed
105
Namepla Pri
te
ce
Ah
210
Ah
31
0
Ah
Ah
315
Ah
46
5
Ah
416
.66
67
Ah
420
Ah
62
0
Ah
Ah
15
5
Ah
$1,
86
0
$3,
72
0
$5,
58
0
$7,
44
0
erie
s
Enclosure
Rec
tifie
rs
500
$7,
500
$3,
000
$18
,00
0
$36
,00
0
$72
,00
0
4
7
155
FT
http://parts.arrow.com/item/detail/elt
ek-valere/h2500a1-vv#JzRR
for one 2-hour
cabinet
for a 4hour
system
for an 8hour
system
x 4strings
year
replacem
ent
$30,
000
$4,2
85.7
1
Po
we
r
Vol
tag
e
Cur
ren
t
5
kW
48
V
104
.16
67
A
1
stri
ng
2
stri
ngs
104.
166
67
52.0
833
33
battery
blocks
amortized
replacement
cost
A/s 1
trin
g
A/s 2
trin
g
hr
hrs
104
.16
67
104
.16
67
A
tot
al
A
tot
al
104
.16
67
208
.33
33
Ah
Exp
ect
ed
105
Namepla Pri
te
ce
Ah
15
5
Ah
Ah
210
Ah
31
0
Ah
$1,
86
0
$3,
72
0
3
stri
ngs
4
stri
ngs
$18
,00
0
$36
,00
0
$72
,00
0
2
34.7
222
22
26.0
416
67
46.2
10
0.01
0.462
4,047
Nm3
/h
scf/h
USD/1000
cu ft
USD
/cu
ft
USD
/h
USD
/yr
hrs
hrs
104
.16
67
104
.16
67
A
tot
al
A
tot
al
312
.5
Ah
315
Ah
46
5
Ah
416
.66
67
Ah
420
Ah
62
0
Ah
$5,
58
0
$7,
44
0
for one 4-hour
cabinet
for a 8hour
system
for a 16hour
system
x 4$15,
strings
000
7
year
$2,1
replacem 42.8
ent
6
Battery Specifications
1.24
A/s 3
trin
g
A/s 4
trin
g
battery
blocks
amortized
replacement
cost
http://www.clearedgepower.com/downloads/files/datasheets/DS0101
_PureCell_M5_011014.pdf
http://www.eia.gov/dnav/ng/ng_pri_sum
_dcu_nus_m.htm
1
12
2.54
100
30.48
0.304
8
0.028
317
43.79
019
ft
in/ft
cm/i
n
cm/
m
cm/f
t
m/ft
m3/f
t3
Ncf/
h
Natural Gas
Annex A Supplementary Information
Annex B Example Systems
Annex C Example Permits