SUSTAINABLE COMMUNITY ENERGY ANALYSIS
conducted for the
WALDEN THREE FOUNDATION
prepared by
Thermal Conversion Corp
A subsidiary of Nuvotec, Inc.
2345 Stevens Drive
Richland, WA 99352
May 2004
Andreas S. Blutke
President
Thermal Conversion Corp
J. Mark Henderson
President & COO
Nuvotec, Inc.
509-375-1940 office
509-375-0401 fax
ablutke@thermalconversion.com
509-375-1940 office
509-375-0401 fax
markhenderson@nuvotec.com
Table of Contents
0.0
Disclaimer ............................................................................................................... 3
1.0
Description and Use of Model ................................................................................ 3
1.1
Introduction ......................................................................................................... 3
1.2
Inputs / Outputs ................................................................................................... 5
1.3
Instructions for Users .......................................................................................... 5
1.4
Recycling Management ...................................................................................... 7
1.5
Waste Management ............................................................................................. 8
1.5.1
Biogas Plant / Digester.................................................................................... 8
1.5.2
Plasma Gasification ........................................................................................ 9
1.5.3
Plasma Melter System................................................................................... 10
1.6
Energy Management ......................................................................................... 10
1.6.1
Combined-Cycle Gas Turbine (CCGT) and Combined Heat and Power ..... 12
1.6.2
High-Temperature Fuel Cell (HTFC) System .............................................. 13
1.6.3
Solar Energy Systems ................................................................................... 13
1.7
Transportation Systems ..................................................................................... 14
1.8
Imports / Exports............................................................................................... 15
2.0
Description of Subsystems.................................................................................... 17
2.1
Domiciles & Small Businesses ......................................................................... 17
2.2
Solar Installations.............................................................................................. 17
2.3
Farming ............................................................................................................. 18
2.4
Forestry ............................................................................................................. 19
2.5
Industry ............................................................................................................. 19
2.5.1
Food Processing..................................................................................... 19
2.5.2
Wood Processing ................................................................................... 19
2.5.3
Steel Production & Canning ................................................................. 20
2.5.4
Glass Production & Bottling .................................................................. 21
2.5.5
Aluminum Production ............................................................................ 21
2.5.6
Cement Plant .......................................................................................... 23
2.5.7
Lime Plant & Construction .................................................................... 24
2.5.8
Manufacturing & Assembly ................................................................... 24
2.5.9
Textile Industry ....................................................................................... 24
2.5.10 Solar System Manufacturing ................................................................ 25
2.5.11 Wind Energy System Manufacturing ................................................... 26
3.0
References ............................................................................................................. 27
4.0
Block Diagrams .................................................................................................... 30
4.1
Figure 1: First Level Overview ........................................................................ 30
4.2
Figure 2: Second Level Overview .................................................................... 30
4.3
Figure 3: Detailed Overview ............................................................................. 30
4.4
Figure 4: Model Housing Unit .......................................................................... 30
4.5
Figure 5: Waste / Energy Management Concept .............................................. 30
2
0.0
Disclaimer
The information presented in this document is non-proprietary and based on publicly
accessible data. Where public data was not available, assumptions were made to
provide functionality to the developed computer model. Such assumptions are indicated
in the model by color code.
The model developed in this study is hypothetical in nature. Although an incorporation
of improvements is planned as more data becomes available, the accuracy of the
content is limited and is not necessarily comprehensive, complete, accurate, or up to
date. To the full extent permissible by law, the developer of this information disclaims
any liability for damages or losses arising from the use of the information.
1.0
Description and Use of Model
1.1
Introduction
Sustainable living entails that human civilizations value, preserve, and protect their
natural resources on the planet. Sustainable development is frequently described as
“the development that meets the needs of the present generation without compromising
the ability of future generations to meet their own needs”. Natural resources of clean air,
clean water, fertile land, fossil fuels, metals and minerals may seem abundant, but in
reality, world population growth and increased resource usage and consumption is
leading to a depletion of many crucial resources for life as known today. For example,
the extraction, conversion, and use of energy are the single largest cause of air and
water pollution, as well as of emissions that may lead to global climate change [46].
Reviewing energy production in detail shows that most developed countries use
primarily fossil fuels (coal, oil, and natural gas) and nuclear fuels for heating, cooling,
manufacturing, and transportation. As the developing countries gradually grow their
economies and improve their living conditions, they add to the rapidly growing world
energy consumption. It is apparent that the high use and dependency on fossil fuels and
nuclear power are hardly sustainable at today’s consumption rates and will be less so
with further increases in demands of the coming years.
Sustainability and sustainable urban existence equally include environmental, economic,
and social aspects, also referred to as the “triple-bottom-line”. Environmental objectives
include to maximize energy efficiency, to conserve resources, to minimize
pollution/damage to the environment, and to conserve wildlife habitats. Economic
objectives address the support of local economies and to provide dignifying employment
opportunities, while social objectives include to improve the quality of life and to promote
social fairness and equality for all people.
Based on the vision by The Walden Three Foundation, Thermal Conversion Corp was
contracted to generate a computer-based model that aims the simulation of sustainable
living in communities without reducing the living standards typical in developed countries
today. Such a sustainable community is designed with the most energy-efficient
methods of production and living available to-date, maximum use of renewable energies,
3
minimization of materials usage combined with maximum materials and energy (heat)
recycle, and highly integrated waste and energy concepts for energy production from
organic waste materials. The city is simulated as “solar city”, utilizing a maximum of
building surfaces for photovoltaic and hot water production and to minimize energy and
time consumed in transportation. The emphasis on energy producing systems based on
renewable energies, waste minimization, and maximum re-usage of wastes for energy
and secondary usage provides a vision to minimize the use of and dependency on fossil
fuels and nuclear power. The model is aimed to assist communities in developed and
developing countries with information and assessment capabilities to gradually achieve
higher levels of sustainability. The model described in this document focuses primarily
on the technical aspects of sustainable living. However, social and economical
sustainability aspects are equal motivators for the concepts proposed in this
development.
The model includes multi-family residences, businesses, industries, and an infrastructure
typical for a selectable size of population; the model in its presented form is built for a
community of 100,000 people. The sustainable community with its surrounding farm and
forest land is self-sustained in terms of basic food supply and energy production, but it
interacts with other communities and the environment in its mass and energy flows.
Products and services are exported/ exchanged with imports of raw and processed
materials and manufactured goods from other communities (see Figure 1).
An emphasis is placed on balancing a selection of industries in the community typical
and necessary for a developed society with energy consumption by those industries.
Residential living is modeled as multi-family dwellings to maximize energy efficiency.
Renewable energy sources such as solar heating and electric power generation
(photovoltaic), recycle of organic wastes for energy production, and use of waste heat
are included for residences and businesses. The waste-to-energy concepts are based
on technologies available today that maximize recycle and minimize the use of landfills.
The energy analysis considers solar heating and power, total electric power, natural gas,
coal and other fuels, and steam/heat.
The model is intended for education, stimulation of discussions, and to become a tool in
the efforts of further developments towards sustainable living. The model is gradually
improved and developed to higher levels of accuracy and feasibility with the support of
numerous individuals. We encourage persons who review and use the model to pass on
any comments and critique so that corrections or missing inputs can be implemented.
Ultimately, the model shall provide the information basis required for planning of new
and upgrades of existing communities with higher levels of sustainability.
The model can be downloaded and used for free by individuals. The user can review
the information contained in the models current revision. Further, the model can be
used by any person to study for example the impact of changes on demands or
production rates, complex interrelations and effects on import/export of materials, fuels,
and goods, the energy mix in the sustainable community, and many more aspects.
A conscious effort was undertaken to select technologies and/or systems that could be
economically competitive. However, this model does not provide the information of
economical effects nor does it claim to be a most economical constellation at cost
structures of to-date. A limited amount of data was available to expose a detailed listing
on heat/steam demands and generation, staffing and skills requirements, and actual
4
hours of labor.
1.2
Inputs / Outputs
The sustainable community is modeled in a MS Windows Excel program. A series of
figures provide an overview of the community model. Figures 1 thru 3 provide
progressively more details to materials, energy, and emission flows within the
subsystems. Inputs and outputs to subsystems are categorized as follows:
Inputs to a subsystem may include:
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Water (from aquifer or water treatment plant),
Steam/heat (from industry)
Electric power (from power plant or solar systems)
Natural gas and other fuels (imports)
Raw materials (imports),
Manufactured goods (imports),
Products (imports or from community).
Outputs from subsystems may include:
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Waste water,
Sewage/manure
Fuel Waste,
Non-Fuel Waste,
Steam/Heat,
Fuel Gas (syngas or CH4),
Electric power,
Recyclable materials (glass, metal/aluminum, paper, etc.),
Products (for internal use or export),
Air emissions.
The emphasis in the study was to capture significant materials and energy flows and to
provide transparency for these streams. Hence, data was gathered and analyzed to
provide input values based on references or (where needed) to make reasonable
assumptions.
1.3
Instructions for Users
Individual Excel sheets have been generated for subsystems and summaries to provide
a structured approach and overview to the collective data set included in the model.
Subsystems include:
 Domiciles & small businesses,
 Farming (animals (including fish), vegetable, corn, and fruit),
 Forestry (tree farms),
 Food processing including meat processing, poultry dressing, dairy
product, and vegetable & fruit processing plants,
 Wood processing including wood mills, pulp and paper production, and
furniture manufacturing,
5
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Aluminum production,
Steel production,
Canning plant,
Cement production
Construction business,
Glass production,
Bottling plant,
Solar systems manufacturing, and
General manufacturing and assembly.
Waste water treatment plant,
Digester (biogas) plant (for manure and sewage),
Gasification plant (for fuel waste),
Plasma melter system (for non-fuel waste), and
Electric power generation (CCGT) plant.
Summaries and Overviews are provided for:
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Fossil fuel usage (NG, gasoline and diesel fuel),
Steam/heat (generation and usage),
Import & export (materials and goods),
Materials and Recycle,
Energy power demand, and
Energy balance.
Subsystem sheets allow the user to study the material and energy inputs and outputs,
assumptions made, calculations, and data sources.
Input and output streams are not specified for individual small businesses. However,
general model assumptions were made for energy requirements for small businesses
and service infrastructure operations. Small businesses include (at a minimum):
bakeries, banking, grocery stores, drugstores, restaurants, retail stores, hardware
stores, insurances, arts and crafts business, entertaining businesses, beauty stores,
travel agencies, coffee shops, tailoring, wood carving, etc. Service infrastructure
operations include: heating/cooling, postal, water systems, transportation, delivery,
receiving/storage, recycling, maintenance and repair (see Figure 4).
A user of the model can change the inputs (e.g. the number of people in the community,
the amount of wood products, individual quantities for food consumption assumptions,
etc.) on individual sheets and review the effects on the overview sheets. For example, if
the population changes the diet to current U.S. consumption rates, this will increase the
demand for food, etc., which then will require more food production. This in turn requires
more materials, energy demand, emissions, etc., but it also will lead to more waste,
which in turn can be used for energy production, etc.
Input fields have light blue or green background to signify various levels of confidence in
the data used and/or for the referenced source of the information. Input fields with a
light blue color indicate data inputs chosen as placeholders, data with lower certainty of
accuracy, or a free selection of values without background source needed. Input fields
with green color indicate that inputs chosen are backed up by a source and/or have a
high level of accuracy. It should be noted that by making changes to fields other than
input fields, the model may become partially impaired.
6
Input with high certainty
Input with lower certainty
Additionally, numbers with a clear background indicate a display of information or
calculated values using data only from the given Excel sheet. A separate color scheme
is used to denote cells using imported data from other sheets. Such imported data is
indicated in a field with a yellow background.
Data imported from other Sheet
An important note for users is that some calculations are iterative and will require the
user to enter recalculated values to bring the overall calculations to a higher level of
accuracy. Instructions are provided in such sheets. The following sheets demand
manual inputs: “CCGT System”, “Plasma Melter”, and “Waste Water Treatment Plant”.
1.4
Recycling Management
Sheet “Materials & Recycle Overview” provides a summary for materials included or not
included in the recycling/re-use concepts accounted for in the model.
Recycle and re-use of materials has a significant effect on reducing the demand for
materials and energy consumption and reduction of secondary emissions (to
environment and landfill). The percentage of recycle versus production of virgin
materials can be adjusted in the individual subsystems (e.g., pulp & paper production,
steel production, etc.). Obviously, there are limitations to the amount of recycling due to
materials degradation (paper fiber), availability of recycle materials (versus demands),
and product quality (e.g., due to impurities in the recycle materials). The concept of
recycle demands education, motivation, and efforts (e.g., separation) by all individuals in
the community. Recycling is assumed for domiciles as well as for any type of business
(e.g., manufacturing). The materials modeled for recycling include:
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Paper and cardboard,
Aluminum (containers, sheets, etc.),
Steel (containers, sheets, construction materials, etc.),
Wood products, and
Glass (containers, etc.).
Note: The use of glass bottles was chosen over plastic due to the following reasons:
The energy consumption associated with primary production of plastic containers is
about 10% below the amount needed to glass containments of the same container
volume. No functional recycle system for plastic bottles is in place yet to offer the re-use
of plastic without complete re-processing. In contrast, multi-use of glass bottles for highdemand beverages (e.g., water, soda, etc.) has been implemented for over 25 years in
Germany and other Western European countries with great success. Multi-use of glass
containers (up to more than 25 times prior to re-melting) reduces the energy used for a
calculated one-time usage to a fraction of the original primary energy spent. Hence, the
use of plastic bottles was not selected as a viable recycling path and plastics (e.g.
7
imported from other communities) are assumed to be a fuel source in the gasification
system or to be exported for recycling outside of this community.
[Note: The model can easily be adjusted to include plastic re-processing, if desired.]
References: [1], [2]
1.5
Waste Management
See Figure 5 “Waste & Energy Management Concept”, including the waste-to-energy
concept used in the model.
See sheets “Gasification System”, “Plasma Melter”, “Waste Water Treatment Plant”,
“Digester System”, and “Materials & Recycle Overview”.
Highly organic waste streams (sewage, manure, etc.) are processed in a digester
system (biogas plant) for methane production. A gasification system (based on plasma
reforming) is selected for converting fuel waste (biomass, organic wastes, animal
corpses, etc.) into synthesis fuel gas (syngas), such as hydrogen (H2) and carbon
monoxide (CO). A plasma melter system was selected for converting non-fuel waste
(residues from production, non recyclable wastes, inorganic materials, etc.) into slag
materials. Fuel gas from the melter system is fed to the gasification system.
All biomass is converted either to methane or syngas. The conversion of specific
biomass streams to soil or fertilizer was not considered in the model.
References: [3], [4], [5], [9], [40], [41], [42], [43], [44]
1.5.1 Biogas Plant / Digester
Biogas can be produced from highly organic feed materials including animal manure
(from cattle, pigs, and poultry), sewage, but also from a number of organic wastes (e.g.,
from fish and food processing and from medical industry). Biogas is the product of the
digestion of soluble and suspended organic materials by naturally occurring anaerobic
bacteria in an oxygen reduced atmosphere. At this point of development, the model only
considers manure waste streams as inputs for the biogas plant; all other organic
materials are processed in the gasification system.
The dry composition of biogas typically consists of about 60 vol.-% methane (CH4), 38 to
40 vol.-% carbon dioxide (CO2), and depending on the organic feed, up to 0.2 vol.-% of
hydrogen sulfide (H2S). There are a number of options for the use of biogas, including
the generation of heat and power by combustion, but also the production of industrial
gases (CH4 and CO2). The model considers the biogas as fuel in the combined-cycle
gas turbine for electric power and heat production. Typically, the H2S is removed from
the biogas (prior combustion) with so-called iron sponge (wood shavings or wood chips
impregnated with hydrated iron oxide, Fe2O3), which is reprocessed, resulting in
elemental sulfur as by-product.
The operation of a biogas plants (also called digesters) is determined by the selected
operating temperature: mesophilic operations at 35 to 38ºC and thermophilic operations
at 52 to 55ºC. The warmer process is typically chosen for high feed rates with shorter
waste retention durations because of the higher bacteria activities at higher
8
temperatures. It also results in a a slight increase in biogas production. The most
experience with such units is in Germany and Denmark. Thermophilic digesters use
closed processing tanks compared to open or closed lagoons used for mesophilic
digestion, which requires waste retention durations of 20 to 25 days. The mesophilic
digester requires a larger floor plan but is less expensive and more forgiving with regard
to process variations (e.g., weather influence on temperature).
Biogas plants are motivated by a number of conditions: Raw manure can be a strong
odor nuisance and can lead to over-fertilization of fields, resulting in nitrate and
phosphate contaminated lakes and streams. Untreated, raw manure emits large
amounts of methane, which have a tremendous greenhouse gas effect (21 times the
effect of CO2). An equivalent CO2 emission reduction of over 7 tons/year for each cow
and over 95% or odor reduction can be realized compared to untreated manure. It
should be noted that the distance of the manure collection point to the treatment plant
needs to be rather close (optimally less than 5 miles) to avoid loosing the benefit of bioenergy production due to the use of transportation energy.
A second benefit of a biogas plant is the production of natural fertilizer, which improves
the utilization of plant nutrients and reduces the consumption of mineral (chemical)
fertilizer. In many cases the natural fertilizer reduces water pollution compared to
mineral fertilizer.
References: [3], [40], [41], [42], [43], [44]
1.5.2 Plasma Gasification
An induction coupled plasma (ICP) reforming process is selected as the plasma
gasification system for organic wastes in the community. Organic waste streams from
agriculture (with the exception of manure treated in the biogas plant), forestry, industry,
households, and businesses are converted into clean-burning synthesis gas, a mixture
of hydrogen and carbon monoxide. The clean synthesis gas is used as fuel gas in the
combined-cycle gas turbine (CCGT), and replaces and/or supplements natural gas as
the fuel source. Synthesis gas use in high-efficiency, high-temperature fuel cells is still
under development, but may offer more efficient electric power generation in the near
future. Hence, in the model the technology chosen for power generation from syngas is
the CCGT system.
“Plasma” is the so-called fourth state of matter (the others are: solid, liquid, and gas).
Plasma is a super-heated gas, similar to the surface of the sun. In case of steam
plasmas, the super-heated gases are composed of atomic hydrogen (H+), atomic oxygen
(O-), and hydroxyls (OH-). These are very reactive chemical species that are beneficial
in the reforming reaction (or conversion) of organic feed materials (e.g., biomass, etc.)
into hydrogen and carbon monoxide. Interestingly, if the plasma does not react with any
material, it goes back to the state of the gas. In case of the steam plasma, it becomes
again steam and with further cooling it becomes again water.
The ICP torch system uses electric power and operates continuously at sustained
plasma temperatures from 3,000 to over 10,000ºC, depending on the plasma gas
selected. Steam reforming or combinations of steam and dry (CO2) reforming are best
9
suited for highly organic feeds. Compared to the typical combustion chamber of
incineration plants, the plasma reforming reaction chamber is less than half the size.
Combustion system use air to burn the organic materials. Because 79% of air is
nitrogen, combustion produces secondary reactants of nitrogen oxides (NOx). The ICP
Reforming Process can avoid the use of air and therefore produce very clean fuel gases
that alternatively can be used for chemical feed stocks. Technically, gasification
reactions can also be achieved in fuel-based partial oxidation process systems. One
reason for choosing the ICP Reforming Process in the waste and energy system of the
city model is the goal for minimization in use and imports of fossil fuels. In comparison,
the ICP Reforming Process is expected to be a more flexible processing tool for the
variety of organic waste materials that are generated in the operation of the city.
Process heat is to be recovered for building heating purposes.
References: [4]
1.5.3 Plasma Melter System
A plasma melter or vitrification system is best suited for non-organic and very low
organic wastes. The process uses electric power for joule heating and arc plasma
electrodes to melt solid wastes, resulting in slag materials usable in building and road
construction. The waste and energy management selected in the model considers
feeding the process gas from the plasma melter system into the plasma gasification unit
to fully convert carryover carbon typical for plasma melter systems to synthesis gas
rather generating a secondary waste stream.
Process heat is to be recovered for building heating purposes.
References: [5]
1.6
Energy Management
See Figure 5 “Waste & Energy Management Concept”.
See sheet “CCGT System”, “Electric Power Demand”, “Fossil Fuel Usage”, and “Energy
Balance”.
Lifecycle analyses for electric power generation systems have been performed by the
World Business Council for Sustainable Development and other organizations,
considering aspects of materials consumption, waste generation, environmental
compliance, and human health effects. In order to achieve more sustainable electric
power generation systems, the efforts are frequently ranked from most sustainable to
least sustainable solutions and practices consider energy savings, energy efficiency, use
of renewable energy, waste to energy, gas fueled CHP, gas fueled CCGT, conventional
gas power plant, cleaner coal plant, and older coal plant. Some studies review nuclear
power plants as the least sustainable solution, whereas other studies (e.g., by British
Energy [50]) point out the benefits of nuclear power systems (e.g., low emissions CO 2
abatement potential).
The energy management system introduced in the model for the sustainable community
10
focuses on:
avoiding and optimizing the use of energy,
utilizing renewable energy systems (solar, wind, water, geothermic heat, etc.)
based on the naturally given local conditions,
converting organic and fuel wastes generated within the community into energy
(in form of fuel gas including biogas and synthesis gas from gasification), and
using fuel gas in combined heat and (electric) power (CHP) systems.
Further, emphasis is given on minimizing the use (and therefore the dependency) of
fossil fuels including coal, oil, and natural gas. Implementing these guidelines leads to
the selection of electric power as the main form of energy within the community (with a
reasonable amount of power back-up systems). It should be noted that heating of
buildings and facility is primarily achieved (e.g., with hot water) by efficient use of solar
energy and heat distribution from industrial operations. A community that generates
sufficient electric power at all times will avoid the import of electric power from other
communities and therefore the consumption of energy generated with possibly lesser
sustainable power generation systems (e.g., nuclear power).
Power generation systems selected in this model are based on best available systems
today. However, new technologies like high-temperature fuel cell systems, expected to
be available in a few years may support the production of electricity as a clean and
convenient primary source of energy for distribution within the sustainable community
with higher power efficiencies than currently available. Such maturing technologies are
planned to be implemented in future upgrades in this model as those systems are
gradually further improved.
In this model, the syngas from the gasification system and methane from the digester
(biogas) plant (see Waste Management) provide the fuel basis for a combined-cycle gas
turbine (CCGT) system. The CCGT system is the primary electric power generation
system for the community. Electric power generators are driven by a combination of gas
turbine (fuel combustion) and steam turbine (recovery of sensible energy). Natural gas
is used as start-up and backup gas, and can be used as supplemental fuel should peak
demands not be achievable with the fuel mix produced by the community.
In principle, the CCGT system could be replaced with a high-temperature fuel-cell (FC)
system (e.g., molten carbonate fuel cell systems) at a point that these systems become
available at the power levels demanded by the community. FC systems have the
potential for even higher electric power generation efficiencies compared to CCGT
systems, reducing the need for fuel production (or use of NG). Both CCGT and FC
systems are considered high-efficiency combined heat and power (CHP) systems with
the potential of using the residual sensible heat for building and facility heating purposes.
[Note: At the current set of input assumptions, replacing CCGT with FC systems would
result in increased electric power availability and potentially export capacities.]
The sustainable community is designed to maximize the use for solar energy in form of
photovoltaic (PV) electric power generation and solar heating. All buildings (domiciles
and industry) provide surfaces (roofs, south side walls) for solar energy collection. PV
electric power is naturally used for peak electric power demand during daytime. Energy
storage in batteries and underground heat storage systems are assumed but not built
into the model at this time. The design of the sustainability model allows choosing the
11
fraction of building surfaces that are either used for PV or solar heat to optimize the
usage for solar energy.
[Note: A solar system production plant was included as one of the key industries of the
sustainable community.]
Additional renewable energy systems, especially wind power, but also geothermal,
hydro, and other forms of renewable energy will be gradually integrated with future
upgrades to the model.
In most industrial operations heat is generated as waste heat. A sustainable industrial
complex takes into account that such heat can be used e.g., in form of steam, for
heating of surrounding buildings and structures. As more detailed information is made
available, the model is gradually upgraded to identify the generation of heat in industrial
processes and to optimize the usage of steam of different qualities (temperature,
pressure). The largest amounts of process heat for secondary use are generated in the
organic waste gasification and CCGT system. Another use for pressurized steam is for
cooling of buildings by integration of absorption refrigeration systems. More data is
currently investigated to integrate this system for energy conversion.
References: [6], [7], [8], [9], [10]
1.6.1 Combined-Cycle Gas Turbine (CCGT) and Combined Heat and Power
Combined cycle electric power generation systems represent the most advanced power
generation systems available to-date. A combined-cycle gas turbine (CCGT) power
plant is essentially an electrical power plant in which a gas turbine and a steam turbine
are used in combination to achieve greater efficiency than would be possible with one
system only. The gas turbine power by the fuel gas (syngas) drives the electrical
generator. The hot gas turbine exhaust is then used to produce steam in a heat
exchanger, which supplies a steam turbine which, by expansion of the compressed
steam generates additional electric power. Using the residual heat from the combustion
gases for heating purposes, the CCGT system becomes a fully integrated combined
heat and power (CHP) plant. Condensed steam is recycled for the steam cycle; residual
waste water is fed to the treatment plant [6].
The variety of technical configurations of CCGTs is primarily driven by the form and type
of fuel selected (e.g., coal, natural gas, synthetic gas/biogas), the output power required,
and the selection of product mix (electric power, steam (high and low pressure).
Net thermal efficiencies of 60% for electric power generation can be achieved for natural
gas. CCGT systems from General Electric and few other companies can be applied to
fuel gas from gasification systems and digester plants. Net thermal efficiencies selected
in the model are at 53%.
In addition to electric power production, the computer model accounts for the direct use
of heat in form of steam for heating of buildings and process heat required in other
manufacturing plants. With proper installations, steam can be easily transported over
reasonable distances even at lower temperatures.
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More data is still required to fully integrate steam as a heating medium in the community
model.
References: [6], [9]
1.6.2 High-Temperature Fuel Cell (HTFC) System
Fuel cells are an emerging technology in the energy sector that offer very low to zero
emissions of harmful pollutants at the location of electric power production. A fuel cell is
an electrochemical device that converts hydrogen or hydrogen/carbon monoxide fuels
directly into energy without combustion. The only products of the fuel cell
electrochemical reaction are electricity, heat and water, if complete conversion of the
fuel gas can be achieved.
Various fuel cells are under development for mobile or stationary applications at a wide
range of power output levels. Proton exchange membrane (PEM) fuel cells require high
purity hydrogen as fuel and operate at net power efficiencies of less than 40%.
The most promising high temperature fuel cell systems (HTFCs) include solid oxide fuel
cells (SOFCs) and molten carbonate fuel cells (MCFCs) with expected net power
efficiencies up of 65 to 75%. SOFCs and MCFCs can convert hydrocarbon fuels, such
as natural gas, carbon monoxide, and hydrogen, directly into electrical power without the
use of an external fuel-processing step (required in most cases with PEM fuel cells).
HTFCs are expected to come on-line within the next 10 years offering an alternative to
today’s CCGT systems. As these systems are coming closer to commercialization, this
technology will be included in the computer model.
References: [7], [8], [9]
1.6.3 Solar Energy Systems
Solar power is, next to wind power, the most important renewable energy source. The
year-round production of 1 MW (electrical) from renewable sources avoids yearly air
emissions of 600 to 2,300 tons of CO2, 16 tons of NOx, 9 tons of SO2, and 600 kg of
other particulate from the combustion of fossil fuels [45]. Solar systems may still be
expensive today, but they are sustainable energy production systems, if care is given to
the method of production to minimize energy consumption as well as emissions during
the production process. As development efforts to reduce energy consumptions and
methods in production of solar systems mature, the model will be revised to reflect such
improvements.
Solar systems can be used for the production of electric power or various forms of heat
(e.g., hot water, steam, etc.). Solar systems for electric power production (photovoltaic)
are generally based on crystalline and amorphous (thin-film) silicon cells, but also nonsilicon solar cells with semiconductor materials are used. As of 2000, the highest power
efficiencies are produced with crystalline Si-cells: 16.5% with mono-crystalline and
14.5% with multi-crystalline Si-cells industrially. The highest efficiencies achieved in
13
laboratory tests are at 24.7% [35].
The computer model accounts for electric power generation from crystalline Si-cells and
solar heat for hot water production, utilizing rooftops and façades of all low-energy
buildings and a selectable additional area designated for solar power production in the
sustainable community. This for example allows the user to calculate the required area
to eliminate the imports on natural gas as supplemental fuel in the CCGT system. It is
recognized that for electric solar systems to provide the power required for the daytime
peak demand in the city, a certain amount of energy storage (e.g., in battery systems) is
required.
Each world region has distinct solar power potentials. A solar coefficient of 5.0 kWh/m 2day is assumed in the model; adjustment to specific locations can be made easily.
References: [9], [35], [45]
1.7
Transportation Systems
See sheet “Transportation”.
Transportation systems such as light and heavy duty motor vehicles, rail systems,
aircraft, freight ships, and recreational boats provide a wide range of benefits, but it is
recognized that they also generate unintended adverse impacts on environmental quality
and human health. These impacts include direct or indirect effects on human and
animals, clean air and water, environmentally sensitive habitats and species. Impact
factors include gaseous emissions such as air pollutants, toxic emissions, and
greenhouse gases, noise pollution, solid wastes, and various liquid emissions (e.g., oil,
de-icing materials, etc.). Key air pollutants include carbon monoxide (CO), ground level
ozone (O3) and its precursors such as volatile organic compounds (VOCs) and oxides of
nitrogen (NOx), lead (Pb), particulate matter (PM10 and PM2.5), and sulfur dioxide (SO2).
Today’s transportation systems primarily consume petroleum products: about 2/3 of the
petroleum used in the US in 1997 was consumed by transportation systems. In the
same year, transportation systems caused about 61% of all US CO emissions, 31% of
VOCs, 36% of NOx, and contributed to a smaller percentage to emissions of lead and
particulate matter. Cities usually have higher pollution concentrations compared to rural
areas. In cities, as much as 95% of all CO emissions may come from on-road vehicles.
In 1997, more than 100 million people in the US lived in counties with O3 concentrations
above the National Ambient Air Quality Standards (NAAQS) established by the US
Environmental Protection Agency (EPA).
Hazardous air pollutants (HAPs), commonly referred to as toxic air pollutants, are
regulated in the US under the EPA Clean Air Act, listing 188 pollutants or chemical
groups as HAPs that are known or suspected to cause cancer or other serious human
health effects or to cause damage to (e.g., aquatic) ecosystems. In 1993, mobile
sources released about 21% of HAPs of a total 8.1 million tons of air toxics released US
nationwide. In urban areas, the concentration of HAPs is generally higher with up to 40
percent of emissions from mobile sources.
14
It is undisputed that conventional transportation systems based on fossil fuels not only
produce tremendous amounts of pollutants, they can cause short- and long-tem adverse
health effects for people and greatly impact environment and habitats. Hence, the
sustainable city in this model is designed to keep car and truck traffic outside the city to
provide a healthier and more amenable way of living. A modern transportation system
can be designed to include a series of electrical transportation systems such as
commuter buses (of various sizes), rail, transport belts, elevators, etc. provided for
personnel and material transportation. Transportation pathways may be largely under
ground, avoiding excessive pavement, keeping a maximum of recreational spaces
above ground, and offering pathways primarily for more recreational, non-motorized
transportation methods (walking, bicycling, etc.) but also for emergency vehicles.
The concept includes a plan for terminals at the city limits (ports) for import and export of
goods. Automobiles may be parked at or near these terminals for owners for travel
outside the city limits. The vision includes an integrated transportation system that
would allow the individual to travel conveniently and expeditiously from one location
(e.g., terminal) to another (e.g. entrance of business and domiciles). As most of the
transportation systems rely on stored or on-line electric power (with appropriate back-up
systems), a power generation system (see 1.6 Energy Management) has to be
sustainable in itself to avoid or minimize gaseous, liquid, and solid emissions.
In summary, eliminating traffic from the inner city keeps more natural spaces untouched
from the construction of roads and increases the recreational value inside the
community. A smart design for the city layout minimizes the travel distances and the
time and energy spent for transportation. All transportation systems operate on electric
power (and possibly on hydrogen in future layouts), creating a clean atmosphere free of
fossil fuel combustion products and noise.
Experience with electric vehicles is been reported by a number of organizations to-date.
Energy storage in lighter batteries at higher energy densities is the main challenge in the
development. However, to-date the following aspects are already achieved:
35% fuel economy improvement over conventional delivery trucks,
up to 250 miles per gallon with light-weight city cruisers (3 wheels, 30 miles, 1
person) and 3.5 to 5.5 kWh / 100 km (~ 60 miles)
Energy density of lead battery: ~0.030 kWh/kg (~400 times lower than gasoline)
Energy density of modern batteries: Ni ~0.060 kWh/kg, Lithium-Ion ~0.120
kWh/kg (~100 lower than gasoline at typically 12 kWh/kg)
Usage typically ~ 20 kWh/100 km in city traffic (compared to ~175 kWh/100 km
for sport utility vehicles (SUVs)
Typical car battery (1995) 14 kWh loading => 70 to 90 km / load
Loading: ~ 2.5 kW at a regular outlet => ~4 hrs for a reach of 50 km.
References: [11], [12], [51]
1.8
Imports / Exports
See sheet “Materials Import & Export”.
The sustainable community exchanges goods and services with other communities for
import and export of materials and manufactured products. Energy system selection was
15
based on the minimization of imports of fossil fuels and use of renewable energies,
combined with the minimization of power demand. The overview sheet in the model
provides a summary of the main imports and exports.
The model supports variations of production and consumption rates which generally will
result in the balance of imported and exported goods and materials. The subsystems
impacts of such changes (e.g., waste water generation, syngas production, etc.) and the
influence on materials and energy flows can be readily explored.
Goods and services imported to the community may include:



Fuel, including natural gas, oil, and coal.
Fuel waste and non-fuel waste streams from surrounding communities,
including bio-waste, sewage waste, plus farming and forestry wastes.
Raw and processed materials and manufactured goods and services,
including and associated with chemicals, processing materials, metals,
living and luxury goods, etc.
The list of goods exported by the community may include:






Farming goods, including fresh and processed (e.g. canned, frozen, etc.)
red meat (beef, pork), poultry (chicken, turkey), fish, milk and other dairy
products, eggs and egg products, fruits, vegetables, corn, livestock, etc.
Forestry and processed wood products, including hardwood and
softwood, lumber and wood products for construction and other uses,
paper and paper board.
Solar energy (PV and hot water) generation systems, including
photocells, hot water panels, etc.
Primary and processed materials, including aluminum, steel, glass,
cement, etc.
Electric power.
Additional exports may include special recyclable materials (e.g.,
batteries, etc.).
Export services may include:





Engineering and services (incl. installation) of renewable energy systems
(e.g. solar power)
Waste and energy management and systems expertise, e.g. for organic
wastes such as sewage sludge, farming wastes, bio-waste.
Engineering services (e.g. process engineering & construction) of
waste/sustainable energy management systems.
Training/education associated with sustainable living, farming and
forestry.
Tourism, expositions, trade shows, conferences, education, etc.
16
2.0
Description of Subsystems
2.1
Domiciles & Small Businesses
See sheets “Domiciles Input & Outputs”, “Domiciles & Small Businesses”, “Consumption
by Domiciles 1”, “Consumption by Domiciles 2”, “Energy Consumption”, and
“Consumption Overview”.
One base assumption for the sustainable community is that the community has the
capability of producing at a minimum the basic goods and services needed. This
includes food, clean water, living quarters, health care, education, transportation, energy
(electric power), waste management, etc.
Inputs and outputs for domiciles and small businesses are configured in the sheets
“Domiciles Inputs & Outputs”, “Domiciles & Small Businesses”, and “Consumption by
Domiciles“. Referenced data or assumptions were made to include specific energy
requirements (electric power, water heating), clean water consumption (purpose,
hot/cold) and waste generation (fuel waste, non-fuel waste, sewage).
Based on the consumption by individuals in households, the personnel-related
consumptions were estimated for communal organizations and other industries (see
sheet “Domiciles Inputs & Outputs”).
Basic assumptions and adjustments for the inputs pre-setting the demand by domiciles
for foods, clean water, and energy/fuels are provided in sheet “Consumption by
Domiciles”.
Per capita consumption of basic goods in the U.S. is (far) higher than in other hightechnology countries (e.g. in Europe) (see sheet “Energy Consumption”).
Based on referenced U.S. consumption, the model allows to pre-set individual demands
by selecting a percentage value (of the U.S. value) for each category. This establishes
the basis for demands in production within the farming, forestry, energy production,
heating/cooling, etc.
Note: The percentages selected for the first analysis are based on typical European
consumption levels. For example, higher prices for primary energy services in Europe
have led to more energy-conscious behavior and reduced per capita usage of primary
energies.
References: [13], [14], [15], [23]
2.2
Solar Installations
See sheet “Domiciles Inputs & Outputs”.
The above sheet provides the inputs to configure population demographics and buildings
for residential, municipal, and commercial occupation. The selection for the building
design allows determining building surfaces usable for solar installations.
The
17
population demographics and building occupation include assumptions/selections for:







Number of individuals in community (e.g., 100,000 persons)
People per family,
Families per multi-family home,
Number of single- or multi-family homes, and apartments,
Number of communal, governmental, and industrial buildings.
Number of small businesses within apartment complex building,
Occupied floors by apartment buildings, small businesses, community
(schools, hotels, etc.) and governmental organizations, and industry.
In addition, the inputs for technical assumptions for the buildings are provided in the
same sheet. Technical assumptions include solar systems (solar energy potential,
system efficiencies, etc.), building configuration, and building surface usage and areas
for photovoltaic versus hot water production. Solar radiation parameters can be chosen
to apply the model for a specific location. Background information and sources of data
are available at references [52] thru [55].
Data used for the energy requirement in houses are based on proven designs and
performances in “Low-Energy-Houses” and specifically on the German design
“Passivhaus” [58]. It is assumed that building materials are to be selected based on
principles of sustainability and health effects. This leads to the use of ecological
materials in construction, avoidance of chemicals in wood treatment, paint, etc. Natural
construction materials such as clay, adobe, recycled paper, untreated wood, and other
biomaterials could be considered and may be included in the materials balance at a later
time.
Upgrades to the model will be performed on a regular basis to account for any significant
improvements in the use of solar systems.
References: [16], [17], [18], [19], [20], [52], [53], [54], [55], [58]
2.3
Farming
See sheets “Animal Farms 1”, “Animal Farms 2”, “Grain Production”, “Fruit & Vegetable
Farms”, and “Energy Usage”.
Production rates of meat, fish, milk, vegetable, fruit, and grain are based on the
demands by the population. Energy and water consumption and waste generation
depend directly on production rates. Additional production for export of farming goods
can be achieved by indicated inputs.
The model is set up to consider the reproduction lifecycles of animals with various types
of waste generated (manure, corpses, etc.). Distinctions are made for the use of meat
(OTM rule forbids to use meat of animals dying a natural death to be consumed by
people).
Whereas the model does not select one farming method over another, ecological or biofarming is to be applied with a minimum use of pharmaceutical products or chemical
fertilizer.
18
References: [21], [22], [24], [25]
2.4
Forestry
See sheets “Tree Farms” and “Consumption by Domiciles“.
Trees are grown for wood and wood chips used in the production of construction
materials, pulp and paper, and wood furniture (and for export, if selected). No data was
found to indicated a “typical” demand by the community, because the demand is highly
dependent on the wood usage and the level of recycle of wood products (e.g., for pulp
production). The model includes an assumed consumption rate for the community.
Sustainable forest practices are assumed.
References: [26], [27]
2.5
Industry
Input/output sheets for the various industries are structured in a similar fashion to allow
easy overviews. Input materials (type, quantity, etc.), specific energy requirement (type,
amount), water and steam consumption, waste generation (fuel, non-fuel, etc.), and
additional outputs (e.g., process steam, secondary products) are specified for each
industrial process. Production rates are either determined by the demands of city
residents, by a typical size plant, or by assumption. Export of goods can be established
by increasing production levels higher than the consumption requirements of the
community.
2.5.1 Food Processing
See sheet “Food Processing”, and “Energy Usage”.
Food processing plants consist of meat processing, dairy product plants, grain
processing, and fruit and vegetable plants. Meat plants process beef, pork, chicken,
turkey and fish. Dairy products plants process raw milk to cheese (natural or
processed), fresh milk (beverage), processed milk (condensed or evaporated), and
frozen products (yogurt, etc.). Grain processing plants produce wheat flour, corn, rice,
and other products. Fruit and vegetable plants produce fresh products and processed
(cut, pealed, sugared, etc.) fruit and vegetable products.
The production rates are based on the demands of the sustainable community. Export
of goods can be achieved by increasing the total production levels higher than the
consumption requirements of the community.
References: [28], [29], [30], [31]
2.5.2 Wood Processing
See sheets “Wood Mill”, “Pulp & Paper Production”, and “Furniture Production”.
The use of wood is divided into three categories: a) lumber and wood products (e.g., for
19
housing construction), b) pulp, paper, and cardboard, and c) furniture and fixtures.
Lumber can be treated, but is very much ready as end product leaving the mill. Wood
planned for furniture production is passed on to the furniture manufacturing plant.
Another fraction of the raw wood is passed onto the chipping and pulping process. Pulp
can be sold as a product or further processed to cardboard and paper.
Wood is ideal material for recycling and depending on the processing step, up to 75% of
the primary energy can be saved (if cardboard and paper are the end products). Wood
“waste” can be produced in form of:




Sawdust, bark, and wood chips (wood mill),
Wood chips and left-over wood (furniture plant),
Lumber, sheets, etc. (construction sites), and
Wooden products (domiciles and businesses).
Most of these streams can go directly to the chipping process, preceding the pulping
process. Recycled paper and cardboard are added here to produce pulp, the base
product for cardboard material. Paper production requires further thermal/chemical
processing as a function of paper quality required.
Note 1: For simplicity the model does not make a distinction between paper and
cardboard. The paper production process from pulp is via the Kraft process. (Model
upgrade possible).
Note 2: Recycling rate, wood production rate, and wood product export quantities are
linked. More than one adjustment may be needed if changes are made.
References: [32], [33]
2.5.3 Steel Production & Canning
See sheets “Steel Production” and “Canning Plant”.
The model includes the full spectrum of steel production including:





Coke production (from coal) and sinter production (from iron ore),
Pig iron production in a blast furnace (BF, from sinter) and molten steel
production in a basic oxygen furnace (BOF, from pig iron),
Molten steel production in electric arc furnace (EAF, from scrap metal),
Thin slab casting followed by cold rolling, and
Continuous casting followed by hot rolling.
The main materials for producing raw iron (pig iron) in a blast furnace are sinter and
coke. Sinter is made from iron ore and coke; coke itself is made from coal. Crude steel
is produced from pig iron (w/ or w/o scrap iron) in a basic oxygen furnace (BOF) or
alternatively in an electric arc furnace (EAF) from (up to 100%) scrap metal.
The model assumed a mix of primary crude steel production in a BOF and in the EAF,
since the planned rates of metal recycling shall be maximized in the model community.
20
The EAF saves up to 40% of primary energy compared to molten steel production from
raw iron. Crude steel is then processed primarily to cold and hot rolling products: Cold
rolling products include coils, strips, and sheet metal, while hot rolling products generally
include wire, bars, rods, rails, profiles, and beams.
Typical small-size steel production plants have a yearly capacity between 50,000 and
100,000 ton per year. Due to the various applications of steel and the dependency of
industries in general, a data point for how much a community (of 100,000 persons)
would actually “consume” on steel products was not found. It can be assumed that
much of the steel would be exported.
The canning plant allows the community to produce containers needed in food
processing. Steel cans are easy to produce and to recycle. No specific data was found
to specify energy requirement, inputs are assumptions and subject to revision.
However, the canning plant is not expected to make a significant difference in the overall
energy balance.
References: [34], [38]
2.5.4 Glass Production & Bottling
See sheets “Glass Production” and “Bottling Plant”.
The production rate for glass (primary use containers) consists of the amount of glass
produced from raw materials, from recycled glass (crushed and re-melted), and from
bottle recycling (intact, chemical cleaning only – see also Section 1.4 Recycling). Glass,
aluminum, and steel (and not plastic) are assumed to be the key materials used for
containers. The primary energy reduction potential for multi-usage of bottles can exceed
95% depending on the lifetime of the container (compared with glass production from
raw materials).
Glass production from raw materials is a process using high amounts of (primarily
electric) energy. Since the primary energy reduction in glass recycling (crushing and remelting) can exceed 20%, it is expected that 100% of the glass will be recycled in the
sustainable community.
For simplicity, the model is set up such that all glass is used as containers (so-called
hollow glass (which are primarily bottles)). The bottling plant can fill-up beverages
consumed in the community. However, there was no data available for the specific
energy requirement for bottling. Hence, inputs are preliminary and are subject to
revision.
Note: Sheet glass (e.g., for windows) production is assumed to have a lower specific
energy requirement. Such variations could be included at a later date.
References: [34]
2.5.5 Aluminum Production
See sheet “Aluminum Production”.
21
Aluminum is produced from the ore bauxite in three main processing steps: 1. Bauxite
extraction and alumina refining (Bayer Process), 2. Alumina smelting (mostly in: HallHeroult Process), and 3. Final Aluminum Processing.
Bauxite extraction typically is performed in open-pits and is either processed into
alumina near the mining location or shipped to smelting markets around the world for
processing. Bauxite mining causes large area land use (e.g., in natural forests) and
erosion with the associated impacts on vegetation and wild life. Since the 1990s, some
aluminum companies (e.g., Alkem) started to apply sustainability development principles
to a number of bauxite extraction fields with the goal to return land after use back to the
original conditions (reforestation, re-introduction of flora and fauna). In the Bayer
process, bauxite crushed, digested (washed with a hot sodium hydroxide solution
(NaOH) at 250 ºC), precipitated (cooled), and calcined (reheated to 1050 ºC) resulting in
alumina (Al2O3). Bauxite extraction and the Bayer process require large amounts of
energy, process water (steam), process materials (caustic soda and lime), land usage,
and even the relocation of tribes and communities. Emissions include waste water,
heat, (metal) particulate emissions and dust, mine tails (bauxite contains 10-40%
impurities), and spent sodium. In addition, the transportation of bauxite or alumina
requires large amounts of fossil fuels.
Alumina is reduced to aluminum (Al) mostly in the Hall-Heroult process. It takes over 13
MWh electric power to produce 1 metric ton of raw aluminum. (The world average is at
16 MWh per ton due to use of a range of production processes and operations of older,
frequently inefficient plants). The smelting process requires large volumes of carbon
(0.4 to 0.5 ton carbon / ton aluminum) and cryolite (Na3AlF6). Aluminum fluoride (AlF3) is
used to reduce the melting point of the cryolite. Alumina smelting results in large
aluminum ingots (slabs, rolls, bars, blocks, etc), that are then transported to the
manufacturing plants for final processing. Frequently, hot aluminum is transported over
shorter distances to some aluminum product manufacturers. Primary emissions from
the smelting process include carbon dioxide, heat, waste water, potliner, spent carbon,
and perflourocarbon emissions (e.g., CF4 and C2F6).
Finally, the manufacturing plants of aluminum products reheat and form purchased
aluminum ingots to a wide variety of products, including automobiles, windows, doors,
frames, construction materials, and beverage containers. The manufacturing of
aluminum products requires different amounts of energy and produce different types and
amounts of wastes and emissions (aluminum scrap and dust, etc.).
The model does not account for energy or materials inputs/outputs associated with
bauxite extraction, alumina production, and transportation of alumina ingots to the
smelting plants. It is assumed that aluminum plants in the model receive alumina in the
desired shape and size for the production of aluminum or used secondary aluminum
(scrap, recycle) in the production of aluminum ingots. At this point, the model includes
the aluminum product manufacture and formation primarily of beverage containers
(cans) and frames in solar modules. For energy and materials flows associated with the
manufacture of the final aluminum products, see “Canning Plant” and “Solar Systems”.
Emphasis is put on the recycle of aluminum products due to the tremendous ecological
(and economical) benefits. At a value of over $1,000 / metric ton, aluminum is the most
valuable commodity waste material. Re-melting aluminum takes only 5 to 10% of the
22
smelting energy in comparison to primary smelting of alumina into aluminum due to the
relatively low melting temperatures of 700-800 ºC. Hence, 90-95% of the primary
energy required to produce aluminum ingot can be avoided by introducing a functional
aluminum collection and recycle system. In addition, every ton of recycled aluminum
avoids the extraction of several tons of bauxite, tremendous amounts of energy,
environmental impacts, and emissions.
Aluminum is recycled from cars, doors, structural frameworks, windows, and beverage
cans. Each category has different recycling rates and quantities and the rates vary quite
strongly in different countries and states. For example, in the US aluminum recycling
from cars in 2002 was at about 85 to 90%. In 1998 the recycle rate for aluminum cans in
the US was at 63% (compared to values over 90% in Western European states, e.g.,
Norway). At a recycle rate of 60%, the material of 100 newly produced cans are
remanufactured to a total of 150 recycled cans. Every new can is therefore 2.5 times
used before it finally ends up on the landfill. In comparison, a recycle rate of 90%
calculates to 11 times use prior to final disposal.
The model accounts for aluminum recycling of cans and other containers (domiciles and
businesses) as well as for waste aluminum from manufacturing and construction
businesses. The production rate for aluminum may have to be increased to account for
higher materials consumption in manufacturing (e.g., of solar systems).
References: [34], [36], [37]
2.5.6 Cement Plant
See sheet “Cement Plant”.
Various methods for cement production and cement products are possible. The
production process chosen for cement products is a high-temperature, dry process using
a pre-calciner, including preheating. This configuration has lower operating costs and
energy consumptions than more simple process designs.
Clinker, the rough precursor to cement, is made from minerals containing calcium,
silicon, aluminum, and iron. Limestone, marl and chalk are the major sources of
calcium. Clay, shale, bauxite, and iron ore provide silicon, aluminum and iron
components. Cement is produced by mixing finely ground clinker with a small amount of
calcium sulphate (gypsum). Depending on the type of cement produced, additional
components such as fly ash, furnace slag, or filter dust, are added. For example,
standard Portland cement is a 95% clinker with 5% gypsum mixture. So-called blast
furnace cement can contain up to 95% slag with 5% clinker.
Within the range of cement products, concrete is a mix of 11% Portland cement, 16%
water, 6% air, 26% sand (fine aggregate), and 41 gravel or crushed stone (coarse
aggregate).
Specific energy requirements and materials inputs are used for Portland cement
production. The model could be upgraded to reflect a higher product range, if desired.
It should be noted that concrete as building material for buildings and structures as well
23
for roads have several benefits in a life-cycle analysis due to long-term use and
properties on heat capacity, strength, durability, etc.
For example, concrete
streetscapes need 40% less lighting, concrete buildings can minimizes or even eliminate
the need for air conditioning due to temperature regulating effects, and concrete roads
lead up to 10% lower fuel consumption (and far longer use) compared to the fossilbased tar pavement mixtures.
References: [34], [52]
2.5.7 Lime Plant & Construction
See sheet “Lime Plant” and “Construction”.
Lime is a product derived from high temperature calcination of limestone (CaCO 3).
Natural resources are required for lime production, since the transportation of limestone
is expensive. To be classified as limestone, the rock must contain at least 50% calcium
carbonate. When the rock contains 30 to 45 % magnesium carbonate, it is referred to as
dolomite or dolomitic limestone. Lime can also be produced from aragonite, chalk, coral,
marble, and seashells.
Equal to the range of raw input materials is the range of lime products: calcium lime,
dolomitic lime, and hydraulic lime. Hydraulic limes are partially hydrated and contain
cementations compounds, and are used exclusively in building and construction. The
main uses of (all the various types of) lime include: metallurgical, environmental,
construction, and agricultural purposes.
Specific energy requirements and materials inputs are used for quicklime (or burnt lime,
CaO) production. The model could be upgraded to reflect a higher product range, if
desired.
The model allows for construction of buildings and structures (e.g., bridges). The data
inputs are subject to change because multiple applications are not defined; the model is
based on steel-reinforced concrete structures.
References: [34]
2.5.8 Manufacturing & Assembly
See sheet “Manufacturing & Assembly”.
The manufacturing and assembly of goods can involve a wide range of products (which
are therefore not specified). However, allowances for energy and other material
consumption, and for waste generation from manufacturing are included in the model.
References: [34]
2.5.9 Textile Industry
See sheet “Textile Production”.
24
This section is under construction.
2.5.10 Solar System Manufacturing
See sheet “Solar System Production”.
Solar energy for heating or production of electricity provides an important input in the
sustainable city concept. Electricity produced in photovoltaic (PV) systems can provide
the peak power required during the daytime. Hence, baseline power production systems
(see Waste & Energy Management System, Figure 5) can operate more efficiently at
relatively constant power production capacity. The production of hot water from solar
cells reduces the need for combustion-based water heating using fossil fuel in residential
and industrial buildings.
Because solar energy systems are integrated as a basic element in the energy
management system, a solar system plant is included in the industrial mix. Basic
materials production of raw silicon and the production of PV modules (e.g., polycrystalline Si cells) and solar heating elements were included. The city may become a
supplier of solar systems production and may install, operate, and maintain solar
systems of other communities. Hence, the community should become a leader in the
development and manufacturing of solar technologies.
As of 2002, 98% of all solar cells are silicon-based. Crystalline silicon cells are
dominant, but the introduction of thin-film solar cells and the development of non siliconbased solar cells are rapidly progressing. Higher systems efficiencies and improved
production methods are progressively offering a wider range of applications for solar
systems.
At this point of development, the model includes only the production of poly-crystalline
solar cells. The production of complete systems consists of three main steps: production
of silicon, manufacturing to solar modules, and assembly to the final solar system. The
main materials used beside silicon are glass (cover) and aluminum (frames).
Silicon from sand (silica) or other silicon-rich raw materials needs to be purified, which is
typically performed in a high-temperature chemical vapor deposition process, using
chlorine as the binding medium. Chlorine can largely be recycled and “waste” hydrogenchloride (HCl) can be re-used in other industries. The specific energy requirement in
silicon production is very high. Typically, an operation of 3 to 7 years of power
generation is required to recover the energy required in the production of new crystalline
solar units. The purity of silicon required for solar cells are significantly lower than silicon
used in computer chips, which results from the fact that the solar industry is the largest
user of “waste” computer chips. [Note: the use of alternative materials (e.g., carbon)
and production methods for silicon are in the development phase.]
More text will be added.
References: [17], [18], [19], [20], [35], [45]
25
2.5.11 Wind Energy System Manufacturing
See sheet “Wind Energy Systems”.
Wind energy is considered the most sustainable form of energy production. Life cycle
analyses [57] indicate that a modern wind turbine system produces about 80 times the
total life-cycle energy used for manufacture, installation, operation, maintenance, and
scrapping/recycle with an operation of 20 years. It takes only about 3 months of wind
turbine system operations to recover all the energy used in this entire life-cycle.
Wind power units have a wide range of commercial availability from several kWh to
multiple MWh electric power production capacity per wind turbine system. AS of May
2004, the 3 largest individual wind turbine systems are installed in Northern Germany by
Enercon [56] with a capacity of 4.5 MW. Today’s typical on-land installations use
individual wind turbines of 1.0 to 2.0 MW. Wind farms have been built with capacities up
to 600 MWh in the US and up to…
Wind turbines avoid CO2 emissions by sustainable production of electric power. A 1 MW
wind turbine typically generates over 3,300 MWh per year - enough to supply 940
households (at 3.5 MWh each). Given a typical energy mix in a western European
country, a 1 MW wind turbine annually avoids 21,700 tons of CO2 equivalent.
References: [56], [57]
26
3.0
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
Information on “Recycling”, Internet link:
http://www.climnet.org/publicawareness/waste.html
Information on “Recycling”, Internet link:
http://www.newtonkansas.com/dep/san/page14.html
Information on “Digester System”, TCC Proprietary Information
Information on “Plasma Gasification”, TCC Proprietary Information
Information on “Plasma Melter”, Internet link:
http://www.inentec.com/pemprocess.html
Information on “CCGT’s”, Internet link:
http://www.asme.org/igti/resources/articles/intro2gta.htmlsfd
Information on “Fuel Cells”, Internet link:
http://www.fe.gov/techline/tl_fuelcellhybrid_start-up.shtml
Information on “Fuel Cells”, Internet link:
http://www.princeton.edu/~humcomp/sophlab/ther_58.htm
“Assessment of Electric Power Conservation and Supply Resources in
the Pacific Northwest”, Battelle/PNL 1982
Information on “Absorption Refrigeration”, Internet Link:
http://geoheat.oit.edu/pdf/tp51.pdf
Information on “Electric Vehicles”, Internet link:
http://www.calstart.org/resources/papers/four_year_report.html
Information on “Electric Vehicles”, Internet link:
http://www.solectria.com
http://www.solectria.com/downloads/ac55.pdf
“Energy and Materials Consumption and Production in the USA”, Internet
link:
http://www.eia.doe.gov/oiaf/archive/aeo01/supplement/supref.html
Information on “Energy Consumption”, Internet link:
http://www.eia.doe.gov/emeu/mecs98/datatables/d98n11_3.pdf
Information on “Energy Consumption”, Internet link:
http://enduse.lbl.gov/info/lbnl-35475.pdf
Information on “Solar Systems/ Wind Energy”, Internet link:
http://www.ecomall.com/biz/solarcat.htm
Information on “Solar Systems”, Internet link:
http://www.solarbuzz.com/applications.htm
Information on “Solar Systems”, Internet link:
http://www.udel.edu/ceep/papers/InternationalComparison.pdf
Information on “Solar Systems”, Internet link:
http://www.sfv.de/sob99334.htm
Information on “Solar Systems”, Internet link:
http://shop.store.yahoo.com/etaengineering/kc80.html
“Livestock manure production rates and nutrient content”, Internet link:
http://ipmwww.ncsu.edu/agchem/chptr10/1011.PDF
“Agricultural Fact Book 2000”, U.S. Department of Agriculture, Internet
link:
http://dir.yahoo.com/Science/Agriculture/Statistics/USDA_Agriculture_Fac
t_Book/
“Umweltökonomische Gesamtrechnungen 2001” (Statistics on energy
27
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
and water consumptions, and emissions for Germany and Europe),
Internet
link:
http://www.destatis.de/presse/deutsch/pk/2001/ugr_bericht_01.pdf
“An Analysis to Develop a Program for Energy-integrated Farm Systems”,
PNL, 1981
Information on “Farming”, Internet Link:
http://www.strickhof.zh.ch/avbetrie/unsbetr/lindau.htm
Information on “Forestry”, Internet link:
http://www.eia.doe.gov/emeu/mecs/iab/forest_products/index.html
“Technology Assessment of Solar Energy Systems: Availability and
Impacts of Woody Biomass Utilization in the Pacific Northwest”, PNL,
1981
“Renewable Energy Resource Options for the Food Industry”,
Battelle/PNL 1981
“Energy Conversion Equipment Applications in the Food Processing
Industry”, Battelle/PNL 1981
“Survey of Energy Conversion Equipment Applications in the Food
Processing Industry”, Battelle-NW, 1981
“Cogeneration Handbook for the Food Processing Industry”, PNL, 1984
Information on “Wood Processing”, Internet link:
http://www.csa.com/routenet/epan/pulppasnIIa.html
Information on “Wood Processing”, Internet link:
http://www.unido.org/ssites/env/sectors/sectors51.html
Information on “Industrial Processes”, Internet link:
http://www.belspo.be/belspo/ostc/geninfo/publ/pub_ostc/CG2131/rappCG
31Ann1_uk.pdf
Information on “Solar Industry and Systems”, Internet link:
http://www.intercortex.com/solar/pdf/EU16Glasgow.pdf
[36]
[37]
[38]
[39]
[40]
“Aluminum Recycling in the US in 1998”, Internet link:
http://www.aluminum.org/Content/NavigationMenu/The_Industry/Recyclin
g/Recycling.htm
Information on “Aluminum Recycling”, Internet link:
http://www.world-aluminum.org/environment/climate/lifecycle1.html
“Effluent Streams in Steel Production (4/2003)”, Internet link:
http://www.aise.org/magazine/03april25_35.pdf
Information on “Water Consumption” (in German), Internet link:
http://www.mev.etat.lu/admenv/eaux/wasser/versorgung.html
“Biogas Plants in Denmark”, Internet link:
http://websrv5.sdu.dk/bio/pdf/rap2.pdf
[41]
Information on “Biogas Plants in the US”, Internet link:
http://www.econ.duke.edu/Journals/DJE/dje2001/lewis.pdf
[42]
“Biogas Systems in the Northwest of the US”, Internet link:
http://www.climatesolutions.org/pubs/pdfs/Biogas.pdf
[43]
[44]
[45]
[46]
Information on “Biogas Technology”, Internet link:
http://www.epa.gov/agstar
Information on “Biogas Implementation”, Internet link:
http://www.epa.gov/agstar/library/nydairy2003.pdf
Information on “Photovoltaic Systems”, Internet link:
http://www.nrel.gov/ncpv/value.html
Information on “Solar Electric Power”, Internet link:
28
[47]
[48]
[49]
[50]
[51]
[52]
[53]
[54]
[55]
[56]
[57]
[58]
http://www.sandia.gov/pv/docs/PDF/PV_Road_Map.pdf
Information on “Solar Power”, Internet link:
http://www.fv-sonnenenergie.de/publikationen/th9798/th9798_068073.pdf
“Photovoltaics for Buildings”, Internet link:
http://www-cenerg.ensmp.fr/ease/photovoltaic.pdf
Information on “Heat Treatment of Steel”, Internet link:
http://www.zianet.com/ebear/metal/heattreat1.html
“Environment and Sustainable Development: Challenges and
Opportunities”, Internet link:
http://www.britishenergy.com/environment/downloadable_items/sustainable_development/
environment_and_sustainable_development.doc
“Indicators of the Environmental Impacts of Transportation”, Internet link:
http://itre.ncsu.edu/cte/indicators.PDF
Information on “Concrete Sustainability”, contact the Environmental
Council of Concrete Organizations (ECCO) at http://www.ecco.org
“Consumer Energy Information/Solar Radiation for Energy”, Internet link:
http://www.eere.energy.gov/consumerinfo/refbriefs/v138.html
“Link to Solar Data (North America)”, Internet link:
http://maps.nrel.gov/annualdir.html
Link to Solar Data (worldwide-limited), Internet link:
http://wrdc-mgo.nrel.gov/
Insolation Map (America, Africa, Middle East, Indonesia), Internet link:
http://www.atlanticsolar.com/technical/insol.htm
“4.5 MW Wind Power System by Enercon“, Internet link:
http://www.enercon.de/englisch/produkte/fs_start_produkte.html
“The Energy Balance of Modern Wind Turbines“, Internet link:
http://www.windpower.dk/en/publ/enbal.pdf
Information on “Low-energy houses (in Switzerland)“, Internet link:
http://www.energienetz.ch/SonnenArchitektur/Text/Energieinfos/Energiein
fos_index.html
29
4.0
Block Diagrams
Block diagrams are provided to describe the structure of the model.
4.1
4.2
4.3
4.4
4.5
Figure 1:
Figure 2:
Figure 3:
Figure 4:
Figure 5:
First Level Overview
Second Level Overview
Detailed Overview
Model Housing Unit
Waste / Energy Management Concept
30