Photovoltaic Cells as an Alternate Energy

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2010
Photovoltaic Cells as
an Alternate Energy
EET 213W
Written Report
Jason Matuszkiewicz
Penn State
4/29/2010
INTRODUCTION
There are many basic needs in today’s society. Without readily available
shelter, food, air, or water today’s society would degrade into the Dark Ages.
There is one more basic need that is the cornerstone of today’s high-tech
industrial society. Without inexpensive and ample quantities of this resource,
populations would drasticially decrease. The transition between today’s world
and a world without this resource would make the scariest Hollywood movie
seem like a musicial. This resource is ENERGY. Historically our energy needs have
been supplied by the use of Fossil Fuels. Society has committed tremendous
amounts of effort in the exploration and exploitation of these resources. Fossil
Fuel use has shot human society from subsistence living with small world-wide
populations into what we expect today.
The quantity of Fossil Fuels is finite. There are many debates on just how
much of these resources are left. Without participation in this debate, finite
means finite. Whether, Fossil Fuels last one day, one year or one century. Society
will need to deal with this issue. The country that developes and implements the
solution will be rewarded greatly.
Most people have very little knowledge of what resources are currently
used and were. This report will give a top-line overview of what resources and
were these resources are used. The overview will be focused on a national and
state-wide level. The second objective of this report will be to supply information
regarding Today’s Residential Alternative choices. The third objective of this
report is to give details regarding a Residential Photovotic example. The Resident
example was choosen intentionally rather than an Industrial example for a
specific reason. Until more people particapate in renewable energy solutions on a
grass-root level, Renewable energy will not be implemented by the main stream.
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TABLE OF CONTENTS
A. Description of Current Energy Needs and were Alternative Energy Stands Today.
1. TODAY’S U.S. ENERGY SOURCE AND USE
2. PA’s ENERGY OVERVIEW
B. Discussion of Different Avaible Alternative Energy Options
1. Small Scale Hydro
2. Bio-mass
3. Small scale Wind Energy
4. Small scale Geo-Thermo
B. RESIDENTIAL PV EXAMPLE
1. Pre-installation considerations
a. Why choose Solar PV power?
b. Who will design, install, etc. the PV power system.
c. Were will the PV panels be placed?
2. PV System Installation
a. Basic Configurations of Solar Sytems
b. Common Components of Solar System Types
1). The Solar Cell
2). Three basic types of PV panels.
3). Panel Mounting
c. Power storage/Usage methods
1). GRID-TIED COMPONENTS
a) Inverters
b) AC BREAKER @ PANEL
c) KILOWATT-HOUR METER
2). OFF-GRID SYSTEM COMPONENTS
a) CHARGE CONTROLLER
b) BATTERY BANK
c) ADDITION DC DISCONNECT
d) AC INVERTER/AC BREAKER
C. COST EXAMPLES
1. Current Average Cost data
2. Current PV System Component Cost
3. System Break-Even Point
D. Conculsions
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TODAY’S U.S. ENERGY SOURCE AND USE
GRAPHIC ONE
U.S. Primary Energy Consumption by Source and Sector, 2008
http://www.eia.doe.gov/overview_hd.html
Energy Information Administration
1000 Independence Ave., SW
Washington, DC 20585
Most people’s knowledge of energy use is very rudimentry. If our goal is to leesen our
dependance on Fossil Fuels, it is important to first establish the current baseline. GRAPHIC ONE
was taken from the US Energy Information Adminstration. The graphic shows 2008 energy data. On
the left of the graphic, it shows the source percentage of the total energy use in the US. The graphic
right shows what percentage a sector takes from the total energy use. The numbers on the lines
connecting Supply Sources and Demand Sectors detail the percentage split of the adjoining heading.
Based on this graphic 83% of our energy needs are supplied by Fossil Fuel sources. The
quantity of energy used by the US in 2008 can be seen on GRAPHIC TWO which was calculated as
99.30 Quadrillion BTUs.
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GRAPHIC TWO
Energy Flow 2008
http://www.eia.doe.gov/overview_hd.html
Energy Information Administration
Recently, Alternative Energy has been growing at exponential rate. Even with these great
strides, the actual impact of alternative energy on the Source mix is very insignificant. In 2008,
Energy derived from Alternative means accounted for 7.3% of the total. To exacerbate the
situation, hydropower electric generation accounted for 38% of the total energy generated in the
Alternative Source. Great increases in hydro-electric production are very unlikely. The percent
breakdown of Alternative Energy was taken form Graphic Three.
GRAPHIC THREE
Renewable Energy Consumption in the Nation’s Energy Supply, 2008
http://www.eia.doe.gov/cneaf/alternate/page/renew_energy_consump/rea_prereport.htmlEnergy Information Administration
1000 Independence Ave., SW
Washington, DC 20585
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PA’s ENERGY OVERVIEW
This report will zoom in from a National perspective to a state-wide perspective. Below is
listed a short overview of Pennsylvania’s energy Outlook.
Pennsylvania Quick Facts
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The first commercial U.S. nuclear power plant came online in 1957 in Shippingport; today, Pennsylvania
ranks second in the Nation in nuclear power generating capacity.
Pennsylvania is a major coal-producing State and sells about one-half of its coal output to other States
throughout the East Coast and Midwest.
Pennsylvania is the leading petroleum-refining State in the Northeast.
The Drake Well in Titusville, Pennsylvania, was the world’s first commercial oil well, and western
Pennsylvania was the site of the world’s first oil boom.
Resources and Consumption
Pennsylvania is rich in fossil fuels. The Appalachian basin, which covers most of the State,
holds substantial reserves of coal, as well as minor reserves of crude oil and natural gas.
Renewable energy resources are also abundant. The Susquehanna River and several smaller
river basins offer considerable hydropower resources, and the Appalachian and Allegheny
mountain ranges are areas of high wind power potential, as are areas both onshore and offshore
along Pennsylvania’s short Lake Erie shoreline. The industrial sector is Pennsylvania’s leading
energy-consuming sector, due in part to energy-intensive industries including aluminum
production, chemical manufacturing, glass making, petroleum refining, forest product
manufacturing, and steel production.
Petroleum
Pennsylvania is the leading petroleum-refining State in the Northeast. Pennsylvania’s large-scale
petroleum refineries are located along the Delaware River near Philadelphia and process primarily
foreign crude oil shipped from overseas. These refineries supply regional Northeast markets. In
addition to local Pennsylvania and New Jersey refineries, Pennsylvania receives propane via the
TEPPCO pipeline from the Gulf Coast and by rail from other States and Canada.
Natural Gas
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Although minor, Pennsylvania’s natural gas production has grown in recent years. Pennsylvania
remains dependent on several major interstate pipelines, most of which originate in the Gulf Coast
region, to meet the majority of State demand. Pennsylvania's natural gas storage capacity is
among the highest in the Nation, which allows the State to store the fuel during the summer when
national demand is typically low, and quickly ramp up delivery during the winter months when
markets across the Nation require greater volumes of natural gas to meet their home heating needs.
Natural gas is used in Pennsylvania primarily for residential and industrial use.
Coal, Electricity, and Renewables
Pennsylvania is a major coal-producing State. Northeastern Pennsylvania’s coal region holds the
Nation’s largest remaining reserves of anthracite coal, a type of coal that burns cleanly with little
soot. Although Pennsylvania supplies virtually all of the Nation’s anthracite, most of the State’s coal
production consists of bituminous coal mined in the western part of the State, where several of the
Nation’s largest underground coal mines are located. Pennsylvania coal demand is high, and it is
one of the top coal-consuming States in the Nation. Pennsylvania’s coal dominates the State’s power
generation market, typically accounting for more than one-half of net electricity production.
Pennsylvania’s electricity markets also rely substantially on nuclear power, and the State ranks
second in the Nation after Illinois in nuclear generating capacity. Pennsylvania’s five operating
nuclear plants have supplied slightly more than one-third of State electricity generation in recent
years. Nuclear power has been an important fuel for electricity generation in Pennsylvania since
1957, when the first commercial U.S. nuclear power plant came online in Shippingport.
Pennsylvania is one of the top electricity-producing States in the Nation and electricity production
exceeds State demand. Pennsylvania is among the largest users of municipal solid waste and
landfill gas for electricity generation and produces substantial hydroelectric power. The State
also produces a small amount of energy from wind. In December 2004, Pennsylvania adopted an
alternative energy portfolio standard that requires electric distribution companies and generators
in the State
to supply 18.5 percent of Pennsylvania’s electricity
from alternative energy sources by 2020.
Energy Information Administration
http://tonto.eia.doe.gov/state/state_energy_profiles.cfm?sid=P
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Residential Alternative Energy Options
There are many different options available to today’s consumer. The actual choice is limited by
the property location, size, and local resources. This report will breifly describe the available choices.
1. Small Scale Hydro
If the property has a small stream running through it, it may make sense to consider this
option to produce Alternative Energy. Graphic Four details the compents to such a system.
GRAPHIC FOUR
Off-Grid Battery-Based Microhydro-Electric Systems
http://homepower.com/basics/hydro/
2. Bio-mass
Like small-scale Hydo, energy produced by Bio-mass has limitations. Bio-mass is limited to rural
areas or suburbia. Even with the limitations, energy produced from Bio-mass will have role in the
Alternative Energy mix for two reasons. First, petroleum is the source for ninty-five percent of the
transportable fuels used by cars, trucks, etc. Today, Biodiesel is produced on a small-scale by indivuals
from used fryer oil. The process that is used is the same process that is used to make soap except the soap
is the by-product. The ability to produce “liquid fuels” from Biomass is an important aspect of this
option.
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Producing energy from the “waste stream” is the second benefit of small-scale bio-mass. Some
of today’s home use commericial or farm wastes to produce home heating. Below is GRAPHIC FIVE
which show an example of a home heating furnace that produces heat from corn-cobs.
GRAPHIC FIVE
CROWN ROYAL STOVES
http://homepower.com/basics/hydro/
3. Small scale Wind Energy
Small-scale wind energy is one option that has the alot potential. As of today, small scale wind
has the lowest cost per kW. A comparision of large scale generation prices are listed on GRAPHIC SIX.
The large-scale comparsion was choosen because a small-scale comparision could not be found. There
are two basic configurations for small-scale wind turbines which are HAWTs and VAWTs. Graphics
SEVEN and EIGHT are examples of each. The downsides to wind turbines would be noise and visual
pollution.
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GRAPHIC SEVEN
Hawt wind turbine
GRAPHIC SEVEN
Hawt wind turbine
Research has been done to limit the noise polution and adapt turbine designs to an urban setting.
The designs are based on slow RPM machines that take advantage of tubulent conditions on urban
buildings. GRAPHIC EIGHT shows an example of an urban designed wind turbine,
GRAPHIC EIGHT
520H Aeroturbine
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4. Small scale Geo-Thermo
Small scale Geo-Thermo takes advantage of the fact that temperatures underground are around
(50-73 °F) all year round. The system transfers heat from the ground that is absorbed in the heat
exchanger. This heat is then transferred to the house usually through a forced air system. During the
cooling season, the cool air is supplied to the house in a simliar manner. The components of this system
are simple. Holes of various diameters may be drilled into the earth in a verticial or horizontal manner.
The holes act as conduits to take ground water at a constant temperature to the house heat exchanger. A
water pump Is used to accomplish this. There is an addition fan in the exchanger that blows air into or
out off the heat exchanger. One of the benefits of this system is that it acts as both heating and cooling.
The downsides of the system would be the cost of drilling the required “wells”. Additionaily, a secondary
heat source maybe required to subliment the “heat-pump” system during periods of extreme cold.
GRAPHIC NINE presents an example of a heat pump system.
GRAPHIC NINE
HEAT PUMP
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http://en.wikipedia.org/wiki/Main_PageEnergy Information Administration
RESIDENTIAL PV EXAMPLE
The last basic alternative energy option that is offered to consumers is photovoltaic energy. This
technology converts solar radiation directly into electricity. An example of a Residental PV system is the
focus of this report. The specific example is broken into two parts. The work needed to be done before
anything is installed will be focussed on first. Secondly, a specific application will be layed out.
There are many reasons why PV panel installations have not become main-stream. The panels
have design lifes of 20 to 30 years. This is a long-term commitment. The upfront cost can be significant
even if the system provides a portion of the average 10 kW of energy/month used by the average
Americian household. There are many challenges to successfully design and install a PV system. With
large upfront cost in both money and time, the power output is not guaranteed. The discusiion next will
center on the required pre-work that should be done.
1. Pre-installation considerations
a. Why choose Solar PV power?
Here are four of the most common reasons to choose Solar PV power.
PV power is Green Power
Solar energy is clean, renewable, and good for the environment. Most of the
electricail generation comes from nuclear and fossil fuel-burning power plants, which
produce emissions including long-lived radioactive wastes, greenhouse gases and other
air pollutants, including those responsible for acid rain. By using renewable solar energy
to meet a portion of your household's electric needs, you can significantly reduce your
household's contribution to the release of these pollutants.(1)
Emergency Power
Solar electric systems can provide your household with emergency back-up electricity in
the case of storms or other utility outages. At these times solar electric power
systems can work along with a conventional generator or alone. (1)
Remote Power
If you plan to build away from established utility service, you should consider the cost of
installing a utility line needed to provide the utility's energy. Often, the cost of extending
conventional power to your residence is more expensive than the solar option. Solar
electric systems are also often a good choice for providing electricity for use in areas
that don't have convenient power sources near by. Common uses can include boats,
electric fence chargers, outdoor lighting, and remote water pumping. (1)
Independent Power
Renewable energy systems provide your home or business with increased
independence. Reducing dependence on traditional fuel sources provides long-term
protection from growing energy costs and uncertain supplies. (1)
(1) http://www.rerc-vt.org/solar/10-use-elect.htm#ind
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b. Who will design, install, etc. the PV power system.
One important question to ask with PV power is “Who is going to design, purchase, and install
the PV system”? This question centers around two factors which are money and one’s knowledge. PV
costs are high. Based on a HOMEPOWER.com article, installation cost are about 12 %. The actual
installation cost will vary significantly with system size and local installer cost. If the materials cost
$30,000 then an addition installation cost of $3,600 would be added to total price tag.
PV system installation may not be for the” weekend warrior”. PV installations require
construction, electrcial, code, and inspection skills to name a few. In additon, Grid-tied installations will
require highly regulated procedures to tap onto the grid. A PV system will require an interface with one
or more third party representatives. Examples of these interfaces would be insurance agents, electricial
code enforcers, local building inspectors, and financing agents.
GRAPHIC TEN
http://homepower.com/view/?file=HP109_pg22_Russell
Making Sense: of Solar-Electric System Costs
By Scott Russell
c. Were will the PV panels be placed?
First, you personal choice may dictate PV placement.
Most tradition PV installations are on top of the roof. This choice maximizes the usuable space because
roof placement does not conflict with living space. However, there are downsides to this approach.
It may be hard to service the panels if required.
May jeopardize the integrity of your roof and cause water damage.
May increase the cost of house insurance.
Your roof may not be at the correct angle or orientation for a PV system.
Another PV option maybe a ground mount. The downside to this approach is the space taking.
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The positive aspects would be:
Lower install costs
Easy to maintain.
Flexible angle and orientation options.
Could be detached from the home.
There are three main factors that will impact how much energy a solar PV system will generate.
Shading
It is important however to ensure that your PV array will not be shaded during the main part of the day
and so avoid placing your array where there will be significant shading from surrounding buildings or
trees.
Orientation
The sun rises in the East and sets in the West, but never goes north. Clearly therefore the more that a
solar PV array is facing South the more direct sunlight it will receive and the more energy it will produce.
In general you should only site a solar PV array so that it faces between the South East and the South
West otherwise its energy generation will be significantly reduced. Before you use your compass to site
an array, you must correct for your site’s declination error. In the Northern Hemisphere, a compass
needle aligns itself along the magnetic north-south line. A PV array should be oriented to “true” or
“solar” south (“geographic” south), so you’ll need to account for magnetic declination—the angular
difference between true and magnetic north. The graphic below shows the magenetic declination for
the U.S>
GRAPHIC ELEVEN
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TILT/ ANGLE
With solar south determined, the next step is to find the optimum tilt for the array. Because a PV
module performs best when its surface is perpendicular to the sun’s rays, considering the sun’s
elevation in the sky is important. In the Northern Hemisphere, the sun rises to its greatest height at
noon on the summer solstice (about June 21). It sinks to its lowest angle at noon on the winter solstice
(about December 21). These elevations vary depending on your location’s latitude. Generally, to
produce the most energy over an entire year at my location, a fixed array should be oriented to true
south and set at a tilt of 36° from the ground.
(3)
http://homepower.com/view/?file=HP109_pg22_Russell
Making Sense: of Solar-Electric System Costs
By Scott Russell
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2. PV System Installation Example
a. Basic types of Solar Systems
This section will detail the components required in any PV system. There are two different PV
installations that could be choosen. GRAPHIC FOURTEEN shows a GRID-TIED installation. In this
installation, PV surplus power can flow back to the grid. The PV owner would receive a credit during this
condition from the Power Company. When PV produced power is lower than the load both the PV
system and the grid supplies power to the loads. GRAPHIC FIFTHTEEN shows a BATTERY-SYSTEM. This
system stores the produced power in a battery bank. The stored power is then independently delivered
from the Grid to house loads. The differences between the two types of installations vary in how the
produced power is stored and delivered.
GRAPHIC FOURTEEN
Grid Intertied Solar-Electric Systems
GRAPHIC FIFTHTEEN
Off-Grid Solar-Electric Systems
http://homepower.com/basics/solar/#ACBreakerPanel
b. Common Components of Solar System Types
1). The Solar Cell
The first component of any PV system is the PV Array. The Basic Building block of the array is the cell.
Both GRID-TIED and OFF-GRID system have this component in common. GRAPHIC SIXTEEN which came
from a HOMEPOWER.COM article provides a detail explanation. The cell works on the same principles as
a Diode. A silcon wafer is doped on one side with a “Negative Doping material”. The middle layer is left
“UnDoped”. On the far end, a “Positive Doping material” is added to the wafer. When the sunlight hits
the wafer, this action frees up electrons in the “N layer” . The electrons flow through the circuit and
push electrons from the “P layer”. This electron jumps the nuetral silicon middle layer. This middle
allows electrons to flow from the P to the N layer. However, this section will not allow reverse flow.
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GRAPHIC SIXTEEN
Solar Cell Basics
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http://homepower.com/view/?file=HP121_pg64_Aldous
Most PV arrays are constructed in panel form that comes in many different sizes. However, there are PV
array designs that are very unique. The tradition designs will be discussed next.
2). Three basic types of PV panels.
Monocrystalline cells are cut from a single crystal of silicon- they are effectively a slice from a crystal.
These are the most efficient and the most expensive to produce.
Polycrystalline (or Multicrystalline) cells are effectively a slice cut from a block of silicon, consisting of a
large number of crystals..These cells are slightly less efficient and slightly less expensive than
monocrystalline cells and again need to be mounted in a rigid frame.
Amorphous cells are manufactured by placing a thin film of amorphous (non crystalline) silicon onto a
wide choice of surfaces. These are the least effient and least expensive to produce of the three types.
Due to the amorphous nature of the thin layer, it is flexible, and if manufactured on a flexible surface,
the whole solar panel can be flexible.
One characteristic of amorphous solar cels is that their power output reduces over time, particularly
during the first few months, after which time they are basically stable. The quoted output of an
amorphous panel should be that produced after this stabalization.
(4) http://www.solar-facts.com/panels/panel-types.php
GRAPHIC TWELVE shown below shows an interesting apllication of this tyoe of solar cell. If the process
could be perfected, manufacturing would be high volume low cost.
GRAPHIC TWELVE
http://www.oksolar.com/roof/
OK.Solar.com
There is a downside to solar cells. Not all the aailble energy is converted into power. Based on
an article in Wikipedia the effieciency is very low. Typical solar panels have an average efficiency of 12%,
with the best commercially available panels at 20%. http://en.wikipedia.org/wiki/Photovoltaic_array There are highcost solar cells that can achieve up to 50% efficiency.
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However, future advances will increase the yields. Professor Graig Grimes at Penn State is
working on such a solution. His solution is to use a combination of nantubes and dyes called dyesensitized solar cells. The dye absorbs the phototons. The nanotubes act as a conduit to transport the
photons to the “P junction” and out of the cell producing power.
GRAPHIC SEVENTEEN
Titania nanotubes
Graig Grimes (Penn State)
These cells have achieved 5% efficiency based on “Spring 2010 Penn State Engineering” article. This does
not seem significant but the “cells” were in the development phase. The principle has a major
advantage. First, these cells have the potential to collect a larger portion of the light spectrum compared
to silicon cells. Secondly, the cost per unit is alot lower than silicon cells. Carbon is the building block of
nanotubes. Carbon is a lot cheaper than silicon. In additon, the fabrication processes is cheaper.
3). Panel Mounting
GRAPHIC EIGHTEEN
WATTSUN SOLAR TRACKERS
http://www.wattsun.com/residential_gallery.html
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As previoulsy stated in the “Were will the PV panels be placed?” section, this report discussed
the importance of PV panel placement. The description was based on a fixed or manually adjusted
mounting system. There is a way to increase the overall system efficiency by tracking the sun with a
dynamic mounting system. GRAPHIC EIGHTEEN shows an example of such as system. The strongest sun
radiation is determined by the intergrated sensor. On-Board electronics optimal places the panels with a
drive unit. The drive unit consists of either a fraction DC gearmotor or a linear actuator. GRAPHIC
NINETEEN shows examples of each. The downside of the “SUN TRACKING” option is cost which could
add $3000 to $7000 to the system.
GRAPHIC NINETEEN
FRACTIONAL DC MOTOR
LINEAR ACTUATOR
http://www.wattsun.com/pdf/Wattsun_TRLA_Universal_2_Module_Installation_Guide.pdf
An appropriately-sized DC disconnect switch is the next requirement. The simple requirement is
required by code for good reason. When the system needs to be serviced, the DC disconnect allows the
PV power to be isolated.
C. Power storage/Usage methods
The similarities between GRID-TIED and OFF-GRID systems end at the PV panels. First, system
compenents of the GRID-TIED design will be covered.
1). GRID-TIED COMPONENTS
a) Inverters
Inverters work by taking the DC power from the source, such as an array of photovoltaic
modules and inverting it to AC power so it can be fed into the grid. The inverter must also synchronize
its frequency with that of the grid (e.g. 60 Hz) using a local oscillator and limit the voltage to no higher
than the grid voltage. Typical modern GTI's have a fixed unity power factor, which means its output
voltage and current are perfectly lined up, and its phase angle is within 1 degree of the AC power grid.
The inverter has an on board computer which will sense the current AC grid waveform, and output a
voltage to correspond with the grid. Grid-tie inverters are also designed to quickly disconnect from the
grid if the utility grid goes down. This is an NEC requirement that ensures that in the event of a blackout,
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the grid tie inverter will shut down to prevent the energy it produces from harming any line workers
who are sent to fix the power grid. GRAPHIC TWENTY shows an inverter example.
GRAPHIC TWENTY
GRID-TIED INVERTER
http://www.xantrex.com/web/id/1890/docserve.aspx
Most PV systems use one central INVERTER. If this component fails, the system ceases to produce
power. There is a new produce in the marketplace that decentralization the invertion process. In
additon, it allows the system to be upgraded to a higher KW rating easier. One example of this produce
is as follows:
The Enphase Microinverter System consists of three components:
* The Microinverter that attaches to the racking beneath each solar module and converts DC power to
grid-compliant AC power
* The Envoy Communications Gateway (EMU) that collects and transmits performance information
from each solar module to a proprietary website for use by the customer
* The Enlighten website where Enphase customers can monitor and manage their solar power
systems 24 hours a day
GRAPHIC TWENTY-ONE
MICRO GRID-TIED INVERTER
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http://www.enphaseenergy.com/products/moreinfo/howitworks.cfm
b) AC BREAKER PANEL & INVERTER DISCONNECT BREAKER PANEL
The inverter output power is connected to the grid and house loads via an AC breaker. The
breaker enables the inverter to be isloated for maintenance reasons. In additon, the breaker protects
wiring from overcurrent.
GRAPHIC TWENTY-TWO
MICRO GRID-TIED INVERTER
https://homepower.com/basics/solar/#KilowattHourMeter
c) KILOWATT-HOUR METER
The meter tracks the amount of Kilowatts that the PV system has put onto the GRID. Based on
local requirements, meters can be one NET Metering device or two ONE-way meters.
The NET METERING design measures watts being supplied by the GRID. When the power is
being pushed onto the GRID by the PV system, the meter can measure this value.
The TWO METER design uses one meter to measure power consumed and one meter to
measure the power produced. Te above graphic shows an example of the Meter.
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2). OFF-GRID SYSTEM COMPONENTS
As previously discussed, the GRID-TIED system went from the PV panels to an INVERTER. The
OFF-GRID system stores and draws power from a battery bank. This is the major differences between
the ON and OFF GRID sytems.
a) CHARGE CONTROLLER
Between the battery bank and the PV modules is a charge controller. A charge controller’s primary
function is to protect your battery bank from overcharging. It does this by monitoring the battery bank.
When the bank is fully charged, the controller interrupts the flow of electricity from the PV panels.
Batteries are expensive and pretty particular about how they like to be treated. To maximize their life
span, you’ll definitely want to avoid overcharging or undercharging them. Like other aspects of the PV
system there is a great variety of chargers and assioated costs.
GRAPHIC TWENTY-THREE
BATTERY CHARGER CIRCUIT
http://www.outbackpower.com/docman/1401102020748flexmax.pdf
b) BATTERY BANK
There are some serious safety concerns that anyone should consider before installing a Battery
Bank. The battery charging process produces extremely flamable hydrogen gas. If an explosion occurs, it
will send acid flying and cause a fire in the process. Most battery banks are stored in a structure away
from other buildings. The battery house is constructed with the batteries inside a containment device in
the event that there is a release of acid.
Not all batteries are universally designed. Solar batteries require “DEEP CYCLING”. Solar
applications require batteries to discharge to below 50 percent of their storage capacity, repeatedly.
Regular car batteries are designed to supply high short bursts of power and will fail in a solar application.
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Carefull consideration should be given to choosing the type, number, and configuration of a battery
bank. The following advice was taken from the experts at HOMEPOWER.COM regarding batteries:
To design a stand-alone renewable energy system, you first establish an “energy budget”—the
number of watthours you will consume per day. Next, you need to determine how many days of stored
energy (autonomy) is required. This variable can range between three and six days (or more) depending
on your average daily electrical consumption, the output of the RE charging sources and their seasonal
availability, and your willingness to use a backup engine generator. Most home systems grow larger over
time. Loads are added, a PV array is enlarged, but a battery bank cannot be readily expanded. Batteries
like to work as a matched set. After about a year, it is unwise to add new batteries to an established
bank. If you foresee growth in your system, it is best to start with a battery set that is larger than you
need. But be sure you have sufficient charging capability,\ or the battery bank will be chronically
undercharged, which will lead to sulfation and premature failure.
A common blunder is to buy the smaller batteries because that approach is less expensive up
front. The problem is that when current splits between parallel strings, it’s never exactly equal. Often, a
slightly weak cell or terminal corrosion will cause a whole battery string to receive less charge. It will
degrade and fail long before other parallel strings. And because partial replacement aggravates
inequalities, the only practical solution is to replace the entire battery bank.
When installing new charge controllers or inverters in your system, make sure to program the
appropriate charge setpoints for your specific battery type. Battery-based PV systems will usually have a
solar charge controller and an AC battery charger, for use with an engine generator or the grid. The AC
charger will typically be built into your inverter. Voltage settings appropriate for your type of battery
must be programmed into these devices. If incorrect charge setpoints are chosen, sealed batteries can
be overcharged and lose their internal moisture. Flooded batteries will be deprived of a full finish charge
and will deteriorate if charge setpoints are too low.
http://homepower.com/view/?file=HP114_pg54_Dankoff
c) ADDITION DC DISCONNECT
In battery-based systems, a disconnect between the batteries and inverter is required. This disconnect is
typically a large, DC-rated breaker mounted in a sheetmetal enclosure. This breaker allows the inverter
to be quickly disconnected from the batteries for service, and protects the inverter-to-battery wiring
against electrical fires.
d) AC INVERTER/AC BREAKER
Just like in the GRID-TIED system, this system requires an inverter to invert the DC voltage to AC
used by house loads.
24
COST EXAMPLES
Last but not least is cost data of a PV system. In this section, this report has taken data
pertaining to average electric usage, electric cost, and Solar PV system component cost and made some
basic financial cost comparisions. Please note, every attempt was made to compare data from the same
year. However, it was not possible. The general intention of this report was to come up with a good
estimate.
1. Current Average Cost data
GRAPHIC TWENTY-FIVE
AVERAGE COST OF NEW U.S. HOME
The Average New Home Price, KW/month Usage, and Cost per KW were taken from Graphics
Twenty five, six, and seven. This data will be used as comparsion later in this report.
GRAPHIC TWENTY-SIX
AVERAGE KW/MONTH USAGE PER U.S. HOME
http://tonto.eia.doe.gov/ask/electricity_faqs.asp#electricity_use_home
GRAPHIC TWENTY-SEVEN
2010 AVERAGE CENTS/KW in PA
25
http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_b.htm
2. Current PV System Component Cost
Graphic Twenty-Eight shows the prices of PV system “Kits”for both Grid-Tied and Off-Grid
systems. The kits components were matched by the supplier. This elimates the consumer from making
design mismatches. This report has extracted cost data for the 6.6 KW system and will use as a
comparision.
GRAPHIC TWENTY-EIGHT
ON / OFF GRID COMPONENT COMPARSION
26
3. PV System Break-Even Point
With the preceeding cost data, a break even point and percent of new home cost can be
determined. The values were calculated on Graphic Twenty-Nine. These two values points will give a
financial perspective of PV cost. A 6.6 KW Grid-tied system would add 9% to the average new home cost.
Adding the same size OFF-GRID system would increase the cost by 13%. A Break-Even Point is another
important financial determinate. This was calculated at 18 years for the GRID-TIED, and 27 years for the
OFF-GRID systems.
To simplify the cacluations please note the following assumptions:
1.
2.
3.
4.
The cost of the NET-METER was not added to GRID-TIED system
The cost of installation, permits, etc were not included in both systems
A 6.6 KW system is 60 % of the average U.S. electric home usage
The break-even point did not include an increase of electric rates.
GRAPHIC TWENTY-NINE
BREAK EVEN and % of NEW HOME COST
27
CONCULSIONS
Based on current costs, the average consumer would be nuts to consider a PV installation. The
break-even point of 18 to 27 years is a joke within a society that changes a TV Channel in-between
commericials. Additionally, “PV panels” are only guaranteed for 20 years. Once the money is spent for
the system, it does not guarantee that the owner will receive any benefit. If something breaks or there is
a lower output, the overall benefit evaporates. This conculsion is supported by the number of PV
systems in-use today. This conculsion would end right here except for the following considerations.
Finite means Finite
Comparing TODAY’S electric and PV costs assumes that “Finite Fossil Fuels” will be plentiful and
inexpensive. By the definition of the word FINITE, that is a ludacrest assumption. The only dileberation
that can be made is “When will the costs of Fossil Fuels exceed the costs of Alternative Energy”. This
question will be the Tipping Point of Human Society as we know it.
Assoiated Hidden Fossil Fuel Costs
This report is centered on a techinicial and informational level. It is not a politicial statement.
However, a true comparision between Fossil Fuels and Alternative Energy requires mentioning the
“hidden costs”. “Fossil Fuels Use” increases Health, Enviromental, and Military expenditures. The exact
dollar amount will not be suggested in this report. However, this report will mention two dollar amounts
to scale the magnitude of the cost. A National Academy of Sciences study was commisioned to detemine
the impact of Burning Fossil Fuels. The NY Times reported in the OCT 19, 2009 edition the following:
” Burning fossil fuels costs the United States about $120 billion a year in health costs, mostly because of thousands
of premature deaths from air pollution, the National Academy of Sciences reported in a study issued Monday. “
The second dollar amount comes from an “US Department of Defense May 07, 2009 article outlining the
2010 Defense Budget. The following is quoted from that article:
“DoD Releases Fiscal 2010 Budget Proposal
President Barack Obama today sent to Congress a proposed defense budget of $663.8 billion for fiscal 2010. The
budget request for the Department of Defense (DoD) includes $533.8 billion in discretionary budget authority to fund base
defense programs and $130 billion to support overseas contingency operations, primarily in Iraq and Afghanistan.”
The “hidden costs” add up to Billions. What is the true Fossil Fuel Cost?
28
Were does PV stand in the Energy Mix?
Even with high costs, there is little doubt that Photovoltaic Systems will be a portion of the
Future Energy mix. PV panels are the only choice for most Residential Consumers. The reason is simple.
PV Panels have little impact on the neighbors. The panels do not make noise. The PV panels can be
mounted low to the ground, thus, elimanting any falling hazards towers. The Concepts of converting
sunlight into Electricity have been tried and tested for many years. Construction and Installations
procedures have been repeated many times over the years.
The major draw-back of the Photovoltaic cells may prove to be the greatest positive. In this
report, it was stated that solar cells are only 12 to 20 percent efficient. This means that there is an
addition 80 percent of efficiency undiscovered. Below is a graph that plots the expected decrease in
$/KW for solar cell through higher production volume and technology improvements.
http://discuss.epluribusmedia.net/content/moores-law-solar-30c-watt-years-come
There is a high probability that conventional electric costs will increase at higher pace than PV
costs. Many government agencies are requiring Ultilities to generate power with Alternative Energy. This
action has two results. First, it may increase the Ultility rates because the “for now” cheaper Fossil Fuels
will be replaced with more expensive Alternatives. From a Residential Perspective, this increase closes
the cost gap and may motivate the home owner to install a PV system. Secondly, Ultilities purchase
large quantities of PV panels. The higher production volumes should decrease the cost of PV panel to
the consumer. Thirdly, there may be a lot of many to be made in the PV industry. With the increased
profitiablility, improvements will be made. This will decrease overall cost.
29
Reccomendations to the Residential consumer.
Based on the research done for this report, it is suggested that a homeowner to the following.
1. Determine the miniuim KW load that is needed for the home
This could be the emergency load in case of a power outage or the lowest “comforable” load.
2. Calculate the PV system component cost of that load. Since the GRID-TIED system seemed the least
expensive option, the component choices would reflect this. The actual component choices should
empahasize future flexiblity. Reccomendations would include:
A. Over-sizing the conductor (wire) from the PV panel location to the Main Breaker Panel. The
conductor should be rated for at least 60% of the peak home load.
Note: This will allow a future power upgrade with minimal problems.
B. Using the Microinverter system instead of the central Inverter.
Note: Again, future upgrades will be less costly.
3. Determine if the installation can be wholely or partial down by the homeowner. Estimate the
remaining contractor installation costs, and add this to the total cost.
Note: There are Alternative Energy Rebates at the time of this report.
2010 FEDERAL REBATE is 30 % of qualified systems
4. Run the plan by the current house insurance company and local zoning boards.
The time to change the installation plan is during the planning stage and not the installation.
5. With a good estimate, measure the personnel financial impact to the house budget.
The partial house load example was intentionial choosen to lessen this impact.
6. Choose GO/ NO GO
7. If GO implement and adjust the plan.
8. Determine if the results warrant upgrades.
Take advantage of improvements in the Technology.
30
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