Nuclear energy as a component of
sustainable energy systems
Marc A. Rosen and Ibrahim Dincer (corresponding author)
Faculty of Engineering and Applied Science, University of Ontario Institute of Technology,
2000 Simcoe Street North, Oshawa, Ontario, Canada, L1H 7K4
E-mail: [email protected], [email protected]
Abstract Achieving sustainable solutions to today’s energy, environmental, and sustainable
development problems requires long-term planning and actions. Energy issues are particularly
prevalent at present and nuclear energy, despite the ongoing debate, appears to provide one
component of an effective sustainable system. In this paper we investigate increasing the utilization
efficiency of energy resources and reducing environmental emissions to achieve more sustainable
development, focusing on utility-scale cogeneration and contributions of nuclear energy. A case study
is presented for Ontario using the nuclear and fossil facilities of the main provincial electrical utilities. It
is observed that implementation of utility-based cogeneration in Ontario can contribute to a sustainable
future by reducing significantly annual and cumulative uranium and fossil fuel use and related
emissions, providing economic benefits for the province and its electrical utilities, and allowing nuclear
energy to be substituted for fossil fuels.
Keywords nuclear energy; cogeneration; efficiency; environment; sustainable development
Introduction
Energy is the driver of technology, life and society. Energy resources help in
creating wealth and improving living standards for individuals and countries.
Development that is sustainable requires, among other factors, access to energy
resources, so energy is a key consideration in discussions of sustainable development [1–3].
Nuclear power is considered by many to have environmental and economic advantages over the thermal power from fossil power stations. Nuclear power does not contribute notably to global warming because nuclear power plants do not emit
greenhouse gases like CO2 during operation (although some CO2 emissions are associated with other phases of the life cycle of nuclear power plants). In many presentday situations, nuclear power plants produce base-load electricity less expensively
than many other energy sources, in large part because of their low operating costs. The
capacity factors and safety records of nuclear power reactors have improved in recent
years, as have their construction times and costs. The approach to final disposal of
spent fuel is still unresolved, but many alternatives have been proposed. Several
researchers [e.g., 4–6] feel that to promote the use of nuclear energy for the 21st
century some problems must be overcome, including issues about the nonproliferation of nuclear material and the disposal or elimination of radioactive waste. Other
concerns include the sufficiency of reserves of uranium for present and future nuclear
plants and the resources required to mine and refine low-grade ores and the excessive
time required for licensing plants and obtaining all approvals and consents.
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M. A. Rosen and I. Dincer
Governments can provide financial and other incentives to encourage the construction of certain types of technologies. For example, the Japanese government has
requested that electric power utilities construct 13 nuclear power stations between
now and 2010, providing approximately a 30% increase in nuclear power generation capacity. Nakata [5] feels that it would be unrealistic for electric power utilities
to build more nuclear power stations at this time without government encouragement because of its higher capital cost and the difficulty of obtaining public acceptance at local sites.
Thermal power plants form the basis of most cogeneration systems. In thermal
power plants, an energy resource (normally a fossil or nuclear fuel) is converted to
heat in the form of steam or hot gases. The heat is converted to mechanical energy,
which in turn is converted to electricity. About 20–45% of the heat is converted to
electricity, and the remainder is emitted to the environment. Cogeneration systems
are similar, except that some of the generated heat is delivered as a product (normally steam or hot water), and less electricity and waste heat are produced. Overall
cogeneration efficiencies of over 80% are achievable, accounting for electrical and
thermal products. Advantages of cogenerating thermal and electrical energy include
1) use of less input energy than would be required to produce the same products
in separate processes, 2) reduced environmental emissions, due to reduced energy
consumption and the use of modern technologies in large, central installations, 3)
economic savings, and 4) safer and more reliable operation. Cogeneration can be
applied in various sizes, ranging from single-building to utility-scale facilities, and
can be integrated with nuclear power facilities.
In this article, a method is investigated for dramatically increasing the utilization
efficiency of energy resources and reducing the corresponding environmental emissions, focusing on utility-scale cogeneration and the potential contributions of
nuclear energy. Technical details of nuclear power have been extensively published.
Fewer studies have been undertaken on the environmental and sustainability aspects
of nuclear power plants [e.g., 4–14].
The present work examines the potential of nuclear energy to be a component of
a sustainable energy system in the future, by considering a case study in which the
potential annual and cumulative (over a longer time period) benefits are investigated
of the simultaneous production of thermal and electrical energy (cogeneration) using
the nuclear and fossil fuel facilities in a large, industrialized geographic region. A
focus is placed on the utilization phase of the life cycle for the relevant cogeneration infrastructure since, due to the long lifetimes of such systems (usually well over
20 years), the environmental impacts are concentrated in that phase.
Energy, the environment and sustainable development
Sustainable development requires a sustainable supply of clean and affordable
energy resources that do not cause negative societal impacts. Energy resources such
as fossil fuels and uranium are finite, while resources such as sunlight, wind and
falling water are renewable and therefore sustainable over the relatively long
term. Wastes (convertible to useful energy via waste-to-energy incineration) and
International Journal of Low Carbon Technologies 2/2
Nuclear energy as a component of sustainable energy systems
111
biomass fuels are also viewed as sustainable energy sources, where supplies exceed
demand.
Environmental impact is associated with energy-resource utilization. For sustainable development, only energy resources that release no or minimal emissions to the
environment, would be utilized, and thus cause no or little environmental impact.
However, since all energy resources lead to some environmental impact, increased
efficiency can somewhat alleviate the concerns regarding environmental emissions
and their negative impacts. For the same services or products, less resource utilization and pollution is normally associated with increased efficiency.
Sustainability objectives often lead local and national authorities to incorporate
environmental considerations into energy planning. The need to satisfy basic human
needs and aspirations, combined with increasing world population, make the need
for implementation of sustainable development policies increasingly apparent. Criteria necessary for achieving sustainable development in a society include [15]:
• information about, and public awareness of, the benefits of sustainability
investments,
• environmental education and training,
• appropriate energy strategies,
• the availability of renewable energy sources and cleaner technologies,
• a reasonable supply of financing, and
• monitoring and evaluation tools.
Environmental concerns and sustainable development
Environmental concerns are linked to sustainable development in that activities that
continually degrade the environment are not sustainable. The cumulative environmental impact of such activities over time often leads to a variety of health, ecological and other problems.
Efficiency and environmental impact are directly related since, for the same services or products, less resource utilization and pollution is normally associated with
increased efficiency. Also, consideration of the entire life cycle for energy resources
and technologies suggests that improved efficiency reduces environmental impact
during most stages of the life cycle.
The interdependence between people and the environment has become increasingly clear recently, as energy is a necessity for maintaining and improving standards of living throughout the world. The widespread use of fossil fuels may have
impacted the planet in significant ways. In addition to the impacts of mining and
drilling for fossil fuels and discharging wastes from processing and refining operations, the greenhouse gases created by burning these fuels is regarded as a major
contributor to global warming. Global warming and large-scale climate change have
implications for food chain disruption, flooding and severe weather events.
Use of nuclear energy can help reduce environmental damage and contribute to
sustainability, in rural and urban areas and in both developing and industrialized
countries. The development and utilization of nuclear energy merits a high priority.
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M. A. Rosen and I. Dincer
Solar
energy
technologies
Nuclear
energy
technologies
Geothermal
energy
technologies
SUSTAINABLE
ENERGY
TECHNOLOGIES
Figure 1.
Biomass
energy
technologies
Hydrogen
energy
technologies
Wave/tidal
energy
technologies
Sectoral
applications
(e.g.,
commercial,
residential,
industrial)
Hydro
power
technologies
Sustainable
Power
• Better environment
• Better efficiency
• Better cost effectiveness
• Better sustainability
• Better energy security
Key energy resources for sustainable/low carbon energy technologies and their
interdependences.
Pathways for using energy resources for sustainable power production are shown
in Figure 1, highlighting the role of nuclear energy. Utilization of sustainable energy
sources is expected to reduce energy-related environmental problems such as global
climate change, and emissions of CO, CO2, NOx, SOx, non-methane hydrocarbons
and particulate matter. More generally, some potential measures to decrease the environmental impact associated with energy use include the following:
• Development and application of clean energy technologies
• renewable energy technologies
• cogeneration, district heating and energy storage technologies
• alternative modes of transport
• clean coal technologies
• Development and application of clean energy management
• energy conservation and more efficient energy utilization
• energy source switching from fossil fuels to environmentally benign energy
forms
• optimum monitoring and evaluation of energy indicators
• Improvement of energy awareness and policy
• education and training for sustainable development
International Journal of Low Carbon Technologies 2/2
Nuclear energy as a component of sustainable energy systems
113
• policy integration
• promoting public transport
• changing life styles
• increasing public awareness
• introduction of carbon or fuel taxes
• Improved energy-related environmental measures
• application of techniques for reduction, re-use and recycling of resources
• acceleration of forestation
• substitution of greener materials for conventional materials
Nuclear energy and sustainability
Nuclear energy can be a significant component of sustainable energy systems. Some
studies have been undertaken on the environmental and sustainability aspects of
nuclear power, which support this view.
Tsujikura [8] believes that light water reactors will continue to play a dominant
role in power generation in the near term, and that it is necessary to establish a quasidomestic nuclear fuel cycle for them, especially in the areas of enrichment and spent
fuel reprocessing. He feels that public acceptance is a significant factor that can best
be achieved by improving the safety of light water reactors and providing extensive
information including decisions by industry and government.
Rashad and Hammad [7] have comparatively assessed the environmental and
health impacts of nuclear and other electricity-generation systems. The study
includes normal operations and accident scenarios, and accounts for the full energy
supply chain, and the environmental impacts from the waste-management cycles are
also discussed. The authors point out that nuclear power, while economically feasible and meeting 17% of global electricity demand, is almost free of the air polluting gases that threaten the global climate. Nuclear power is seen to compare well
with other sources for electricity generation in terms of such environmental emissions as SO2, NOX, CO2, CH4 and radioisotopes, taking into account the full fuel
chains.
Duffey [11] describes the role of nuclear energy in a sustainable future, addressing social, economic and environmental concerns. The over 400 nuclear reactors
operating worldwide today avoid annual emissions of nearly two billion tonnes of
greenhouse gases (GHGs), yet they receive little recognition for the emissions avoidance in current Kyoto and other policies. Duffey notes that more focus is placed on
conservation, renewables and efficiency, despite the fact that these measures alone
also can not significantly reduce the atmospheric GHG burden. Future economic
growth in all countries is tied to energy and electricity use, and prosperity and the
alleviation of poverty depend on an emissions-free and safe energy supply. Recent
price hikes in fossil fuels and power blackouts also emphasize the need for the reliable power providable with nuclear energy. Duffey expects that a particularly important future role for nuclear power will be its links to the hydrogen economy, since
the introduction of hydrogen into the transportation sector will benefit the environment only when it is derived from low carbon sources. He shows that major reducInternational Journal of Low Carbon Technologies 2/2
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M. A. Rosen and I. Dincer
tions in GHGs worldwide can be obtained by nuclear-electric production of hydrogen. He also demonstrates a potential key synergism with renewable wind power in
the hybrid production of distributed hydrogen.
Takahashi [4] highlights that energy security is vital for steady growth of the
world’s economy and, although many novel non-nuclear energy sources are being
explored, that much less attention is given to nuclear energy. He indicates that safety,
environment protection and non-proliferation should be given high priority in developing nuclear energy, and proposes establishing deep underground nuclear parks,
where energy production as well as fuel processing can be carried out in a well protected small area, perhaps under international supervision to ensure non-proliferation. To foster public support for the development of nuclear energy, Takahashi
suggests expanding other beneficial uses of radioactive materials, such as in medical
applications and as tools for scientific research. Takahashi feels that nuclear science
and technology will be vital for evolutional change of human civilization and the
survival of society.
Fiore [13] points out that deregulation and new environmental requirements, combined with increasing scarcity of fossil resources and world energy demand, have
renewed the debate on tomorrow’s energy systems. Nuclear energy has positive and
negative attributes. On the one hand, it is cost competitive and does not contribute
to the greenhouse effect, providing a strong candidate for sustainability and acceptability. On the other hand, nuclear fission reactors incur risks for the environment
and health. Fiore notes that some researchers prefer another type of nuclear energy,
fusion. ITER (International Thermonuclear Experimental Reactor) is an international
collaborative project aimed at bringing fusion to a production stage so it can address
global challenges like meeting the increasing energy needs of developing countries.
The project involves major technological, economic and political challenges.
Tokimatsu et al. [10] revealed conditions under which nuclear fusion could be
introduced economically (by achieving breakeven prices), and to evaluate the future
role of nuclear fusion in energy systems. Once breakeven prices are achieved, the
authors expect nuclear fusion to capture a portion of the electricity market by 2100,
to help reduce annual global total energy systems costs, and to help mitigate carbon
emissions in line with CO2 constraints. Future uncertainties are key issues in evaluating nuclear fusion, so the authors allowed for uncertainties in energy demand scenarios, the introduction timeframe for nuclear fusion, capacity projections of nuclear
fusion, the CO2 emissions target in 2100, capacity utilization ratios of energy/environment technology options, and utility discount rates. The investigation concluded
that presently designed fusion reactors may be ready for economic introduction into
energy systems beginning around 2050–2060, and that such reactors would reduce
both annual energy costs and the carbon tax (the shadow price of carbon) under a
CO2 concentration constraint.
Case study
The province of Ontario, Canada is considered for the case study and the implementation of utility-based cogeneration in that province is evaluated. The principal
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115
electrical utilities in Ontario include Ontario Power Generation, formerly Ontario
Hydro. With a population of approximately 12 million and a land area of just over
one million square kilometers, Ontario is the main industrial province in Canada.
Both annual and cumulative benefits of utility-based cogeneration are determined
for Ontario, relative to the business-as-usual situation where cogeneration is applied
only in a very limited manner. The case study is based on investigations carried out
by one of the authors in the mid-1990s [16–18], but is believed to present results
and general trends that are relatively accurate, meaningful and valid today. Related
economic, environmental and health benefits studies have been carried out [19–22].
Technology considerations
Many types and applications of cogeneration systems exist throughout the world,
and most use fossil fuels, although some are based on nuclear energy. The size and
type of a cogeneration system are normally selected to match as optimally as possible the thermal and electrical demands. Two main categories of heat demands can
normally be satisfied through cogeneration:
• industrial processes, which require heat at a wide range of temperatures for such
tasks as drying, heating and boiling in various industries including chemical processing, manufacturing, metal processing, mining and agriculture.
• residential-commercial processes, which require large quantities of heat at relatively low temperatures for heating air and water. The use of a central heat supply
to meet the heat demands of the residential-commercial sector (including the institutional sector here) is often referred to as district heating, and has been applied
extensively. Cogenerated heat can be used to drive absorption chillers for space
cooling, rather than using more conventional electrically driven chillers.
For its current electrical generation, Ontario’s electrical utility relies mainly on
nuclear and hydraulic energy and fossil fuels (almost entirely coal). The overall
station efficiency (based only on electrical energy) is taken to be 37% for coal-fired
plants and 30% for nuclear plants. Efficiency can be markedly improved for both
types of plants if the thermal energy rejected by the condensers is used through
cogeneration. Cogeneration systems are possible based on current coal and nuclear
electrical stations in Ontario (e.g., steam can be extracted from one or more points
on the turbines and exported to nearby heat users, or steam can pass through part of
the steam turbines and then be diverted for use in heating). In the early 1980s,
Ontario’s electrical utility published a brochure entitled “Heat Energy Locations in
Ontario” stating that large supplies of heat in the form of steam or hot water are
available at several of its stations around the province (at as high as 230°C for nuclear
and 510°C for coal-fired stations). Nevertheless, cogeneration is used only very minimally in the current electrical generation system (e.g., cogenerated steam from the
Bruce Nuclear Power Station is used for heating in such other facilities as the onsite heavy-water production plant and the Bruce Energy Centre, a nearby industrial
park). A significant degree of flexibility exists in the current system for utilitybased cogeneration within both individual station units and multiple unit
International Journal of Low Carbon Technologies 2/2
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M. A. Rosen and I. Dincer
stations, and many enhancements of the existing system are possible using advanced
cogeneration technologies. The present work concentrates on fuels presently used
by Ontario’s electrical utilities, so natural gas-based cogeneration systems are not
considered.
Thermal energy demands and users
Potential markets in Ontario for utility-cogenerated thermal energy, mainly in the
residential, commercial, institutional and industrial sectors, are a portion of the total
thermal-energy demands. These markets depend on many factors:
Technical factors:
• Heat characteristics and availability: the quantity, supply rate and temperature of supplied heat must satisfy all demand requirements and, in addition,
the system must be able to accommodate actual variations in heat-demand
parameters (quantity, temperature, etc.). In this area, cogenerated heat from
nuclear plants is usually at a lower temperature and thus less valuable than
that from fossil-fired plants. Cogenerated heat must also be available when it
is in demand, either by cogenerating when heat is demanded or storing the
heat during periods between its generation and utilization.
• Location: users and suppliers of thermal energy must be located within a suitable distance of each other. Given nuclear plants tend to be few, large and
separated by large distances, rather than spread out in many geographic
regions, the potential contributions for nuclear-derived heat are lower than
those for fossil-drived heat.
• Infrastructure: an overall infrastructure and all relevant technologies must
exist for all cogeneration steps, including heat supply, distribution, storage
and utilization.
Non-technical factors:
• Economics: given a traditional economic approach, the economics for cogeneration options should be at least competitive with, and preferably superior
to, the economics for other non-cogeneration options. Note that the inclusion
of externalities such as environmental costs can substantially increase the economic competitiveness of cogeneration, and that for policy reasons (such as
those reflecting the importance of environmental issues), cogeneration alternatives may be considered even if the specific application is not economically
competitive.
• Attitude: the attitude towards the idea must be positive for all parties involved
(suppliers, distributors, users, etc.).
Scenarios for utility-based cogeneration
Six scenarios are considered, for each of which changes are evaluated in energy consumption and environmental emissions when cogeneration is implemented, relative
to a base-case year. The scenarios consider the effects of cogeneration implementation on:
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Nuclear energy as a component of sustainable energy systems
117
• the overall province,
• the electrical-utility sector, and
• the non-electrical-utility sector (i.e., the remainder of Ontario).
The scenarios illustrate the potential benefits of utility-based cogeneration over the
range of viable implementation possibilities. Base year energy data (in physical units
and energy units) are given in the top two sections of Table 1 and environmentalemission data are presented in the top section of Table 2. Following earlier investigations by the author, the base-case year is taken here to be 1989. The effects of
implementing the cogeneration scenarios are considered first for a one-year period
(the base year); then the cumulative effects over many years (more than 20) of implementing the cogeneration scenarios are evaluated.
The six cogeneration scenarios considered are all based on the existing facilities
of Ontario’s electrical utility. The scenarios involve the use of heat from basic or
advanced utility-based cogeneration networks to supply some of the heat demands
of the residential-commercial and/or industrial sectors. The scenarios can be divided
into three groups:
• Of the annual heat demand of the residential-commercial sector, a basic utilitybased cogeneration network supplies a small portion (9%) (Scenario A) and an
advanced utility-based cogeneration network supplies a significant portion (40%)
(Scenario B).
• Of the annual heat demand of the industrial sector, a basic utility-based cogeneration network supplies a small portion (6%) (Scenario C) and an advanced
utility-based cogeneration network supplies a significant portion (12%) (Scenario
D).
• Of the annual heat demand of the residential-commercial and industrial sectors,
a basic utility-based cogeneration network supplies a small portion (Scenarios A
and C combined, yielding Scenario E) and an advanced utility-based cogeneration network supplies a significant portion (Scenarios B and D combined, yielding Scenario F).
The scenarios likely span the possible ranges of market penetration for utility-based
cogeneration in Ontario, with Scenarios A and C assuming the least penetration and
Scenario F assuming the most.
The scenarios consider two hypothetical utility-based cogeneration networks:
• Basic: the current network of thermal electrical stations in Ontario, with only
minor cogeneration modifications implemented in some nuclear and coal
stations.
• Advanced: a modified network, where some multi-unit stations are separated and
located near heat demands, and advanced cogeneration technologies are used
along with current-technology thermal stations modified for cogeneration. Government incentives to promote cogeneration are assumed to result in significant
market penetration and public acceptance.
Hot-water storages are used in both networks, especially for coal stations, which
operate much more intermittently than nuclear stations. The energy efficiency for a
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118
Table 1.
M. A. Rosen and I. Dincer
Base-case annual energy use in Ontario and % reductions for six cogeneration
scenariosa
Base-case
energy use (PJ)
Utility sector
Province
(no utility)
Province (total)
Base-case
energy use
(physical units)
Utility sector
Province
(no utility)
Province (total)
Electricity
Gas &
NGLs
Oil &
petroleum
Coal
Other
Uranium
Total
–
477
–
824
14
782
286
21
–
158
640
–
940
2260
477
824
796
307
158
640
3200
Electricity
(TWh)
Gas &
NGLs
(Teraliters)
Oil &
petroleum
(Gigaliters)
Coal
(Megatons)
Other
(Kilotons)
Uranium
(Tons)
–
132
–
21.0
0.33
21.5
10.4
0.71
–
5340
1040
–
132
21.0
21.8
11.1
5340
1040
% reductions in values (Scenario A)
Utility sector
–
–
Province
5.3
2.8
(no utility)
Province (total)
5.3
2.8
% reductions in values (Scenario B)
Utility sector
–
–
Province
24
13
(no utility)
Province (total)
24
13
% reductions in values (Scenario C)
Utility sector
–
–
Province
3.0
1.2
(no utility)
Province (total)
3.0
1.2
% reductions in values (Scenario D)
Utility sector
–
–
Province
6.3
2.4
(no utility)
Province (total)
6.3
2.4
% reductions in values (Scenario E)
Utility sector
–
–
Province
8.3
4.0
(no utility)
Province (total)
8.3
4.0
% reductions in values (Scenario F)
Utility sector
–
–
Province
30
15
(no utility)
Province (total)
30
15
a
0
0.5
17
0
–
0.5
6.8
–
10
2.4
0.5
17
0.5
6.8
4.6
0
2.1
41
0
–
2.3
30
–
33
10
2.0
38
2.3
30
17
0
0.3
13
2.7
–
2.5
2.5
–
5.8
1.4
0.3
13
2.5
2.5
2.7
0
0.6
16
5.6
–
5.1
5.3
–
8.6
2.8
0.6
16
5.1
5.3
4.5
0
0.7
20
2.7
–
3.0
9.4
–
13
3.7
0.7
19
3.0
9.4
6.3
0
2.6
47
5.6
–
7.5
35
–
38
13
2.6
44
7.5
35
21
Hydraulic energy use is not shown as it is ‘free.’ ‘Other’ includes coke and coke oven gases, originally
from coal. Uranium energy use is taken to be delivered fission heat. NGLs denotes Natural Gas Liquids.
Total base-case annual energy use for the overall province (3200 PJ) includes shown primary energy forms
and secondary form, electricity.
Source: Rosen [16].
International Journal of Low Carbon Technologies 2/2
321
1060
1380
17
1.2
4.9
41
5.5
14
13
2.7
4.3
17
3.4
6.5
20
2.9
6.8
47
8.8
18
Utility sector
Province (no utility)
Province (total)
% reductions in values (Scenario A)
Utility sector
Province (no utility)
Province (total)
% reductions in values (Scenario B)
Utility sector
Province (no utility)
Province (total)
% reductions in values (Scenario C)
Utility sector
Province (no utility)
Province (total)
% reductions in values (Scenario D)
Utility sector
Province (no utility)
Province (total)
% reductions in values (Scenario E)
Utility sector
Province (no utility)
Province (total)
% reductions in values (Scenario F)
Utility sector
Province (no utility)
Province (total)
47
4.8
12
20
1.5
4.2
17
1.5
3.8
13
0.7
2.5
41
3.4
9.0
17
0.7
3.2
92
526
618
NOX
47
7.4
15
20
1.7
5.2
17
2.1
4.9
13
1.0
3.3
41
5.5
12
17
1.2
4.2
32
132
164
CO2 (1000)
47
4.2
4.2
20
1.2
1.2
17
0.9
0.9
13
0.4
0.5
41
3.4
3.4
17
0.7
0.8
4
3500
3504
CO
47
1.6
2.1
20
0.5
0.7
17
0.4
0.6
13
0.2
0.4
41
1.2
1.7
17
0.3
0.5
11
837
849
Particulates
47
2.9
3.0
20
1.7
0.8
17
0.7
0.7
13
0.3
0.3
41
2.3
2.3
17
0.5
0.5
0.5
775
775
V.O.C.
35
–
35
9.4
–
9.4
5.3
–
5.3
2.5
–
2.5
30
–
30
6.8
–
6.8
1.04
–
1.04
Spent uranium
83
–
83
22
–
22
14
–
14
6.7
–
6.7
69
–
69
15
–
15
591
–
591
Thermal pollution (PJ)
35
–
35
9.4
–
9.4
5.3
–
5.3
2.5
–
2.5
30
–
30
6.8
–
6.8
11
–
11
Radiation (1015 Bq)
a
V.O.C. denotes volatile organic compound. Thermal pollution is taken to be heat rejected to bodies of water, so as to cause appreciable temperature rises. Radioactive emissions from non-nuclear-energy sources, such as radioactivity in coal-station stack gases, have not been considered.
Source: Rosen [16].
SO2
Material emissions (kilotons)
Base-case annual emissions to environment in Ontario and % reductions in base-case values for six cogeneration scenariosa
Base-case emissions to the environment
Table 2.
Nuclear energy as a component of sustainable energy systems
119
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M. A. Rosen and I. Dincer
cogeneration plant hc is dependent on the electrical efficiency he and thermal efficiency ht as follows:
hc = he + ht
Based on data for Ontario’s electrical generating stations, for both networks the following approximations can be made for the electrical efficiencies:
hc = 32 − (0.11)T (for nuclear cogeneration)
and
hc = 40 − (0.074)T (for coal cogeneration)
where the electrical efficiency he is in per cent and T denotes the cogeneratedheat temperature in °C. The overall efficiencies are taken to be 85% for nuclear or
coal cogeneration, and the thermal efficiencies can be evaluated using the above
expressions as the differences between the corresponding overall and electrical
efficiencies.
The scenarios consider two potential cogenerated-heat users:
• Residential-commercial sector. Based on data in Statistics Canada’s “Quarterly
Reports on Energy Supply-Demand in Canada,” the annual heat demand in
Ontario in the base-case year was 514.5 PJ for the residential-commercial sector.
Residential-commercial demands are almost exclusively for low-temperature
heat for space and water heating.
• Industrial sector. Based again on Statistics Canada data, the annual heat demand
in Ontario in the base-case year was 414 PJ for the industrial sector. The industrial heat demand is for various tasks and can be approximately broken down as
59.5 PJ at low temperatures (<125°C), 147.0 PJ at medium temperatures (125°C
to 400°C) and 208.5 PJ at high temperatures (>400°C).
In all scenarios, half of the cogenerated heat is used to offset electricity provided by
Ontario’s electrical utility to users for heating. The other half of the cogenerated heat
is used to offset the non-electrical utility energy resources (e.g., natural gas and oil)
used by others for heating. In this way, nuclear energy is substituted for fossil fuels.
Also, the cogenerated heat is assumed to be produced from coal and nuclear energy,
in the same proportions as electricity is generated from them in the base year (i.e.,
33% from coal and 67% from nuclear energy); for scenario F, however, values of
31% and 69% respectively are used since insufficient coal is otherwise available for
cogeneration. To supplement the cogenerated electricity, current-technology noncogenerating coal and nuclear generating stations are used, in the same proportions
as cited above.
The portions of the heat demands to be met by utility-cogenerated heat are estimated by applying the factors discussed in the previous section. The main factors
considered in deciding to use utility-cogenerated heat are taken to be distance, infrastructure, attitude, economics and temperature. Several assumptions are made for
each end-use sector considered:
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Nuclear energy as a component of sustainable energy systems
121
• Residential-commercial sector. It is assumed that a) utility-cogenerated heat temperatures permit for all scenarios 100% of the heat demands to be satisfied, as
they are all at low temperatures; b) 35% of heat demands are within a servicable distance of the cogeneration plant for scenario A, and 60% for scenario B;
and c) 25% of potential users find the infrastructure/attitude/economic conditions
favorable enough to use cogenerated heat for scenario A, and 65% for scenario
B.
• Industrial sector. It is assumed that a) utility-cogenerated heat temperatures
permit 100% of low- and medium-temperature industrial heat demands to be satisfied for scenarios C and D, and 30% of high-temperature demands for scenario
C and 40% for scenario D; b) 30% of low-, 23% of medium- and 15% of hightemperature demands are located within a servicable distance of the cogeneration plant for scenario C, while the corresponding values are 60%, 45% and 30%
for scenario D; and c) 40% of potential users find the infrastructure/attitude/
economic conditions favorable enough to use cogenerated heat for scenarios C
and D.
Case-study results and discussion
Annual assessment
Table 1 lists reductions in annual energy use for each scenario, expressed as a percentage of the corresponding base-case values. Similarly, Table 2 lists percent reductions in base-case annual emissions. Table 3 highlights important findings, including
for each scenario the heat demands supplied by cogeneration (broken down by
sector), the reductions in the electrical utlility’s energy (coal and nuclear) use
and electricity production, and the percentage of coal and nuclear plants that
cogenerate.
The key points demonstrated are that, for all scenarios considered, energy use and
environmental emissions decrease for the utility sector, the rest of the province and
Table 3.
Summary of principal data and findings for the cogeneration scenarios
Heat demand satisfied
by cogeneration (PJ yr−1)
Scenario
A
B
C
D
E
F
% reductions in some key
utility parameters
% of fuel
cogenerating
for utility
Residential/
commercial
Industrial
Total
Coal
use
Uranium
use
Electricity
production
Coal
Uranium
46
206
0
0
46
206
0
0
26
54
26
54
46
206
26
54
72
260
17
41
13
16
20
47
7
30
3
5
9
35
5
24
3
6
8
30
12
77
6
13
22
100
8
49
4
2
12
49
Source: Rosen [16].
International Journal of Low Carbon Technologies 2/2
122
M. A. Rosen and I. Dincer
the overall province; and provincial electricity-generation requirements decrease.
Specific implications of these findings are significant, and highlight the impact
nuclear energy can have:
(i)
(ii)
(iii)
(iv)
provincial annual electricity consumption decreases by as low as 3% to as high
as 30%, permitting provincial annual electrical generation to decrease by corresponding percentages;
annual uranium use by the electrical utility and related emissions both
decrease by from 3% to 35%;
annual coal use by the electrical utility and coal-related emissions both
decrease by from 13% to 47%; and
excluding the electrical utility sector, the province’s annual use of fossil fuels
and the corresponding annual emissions both decrease by approximately 1%
to 15%.
A detailed assessment of further environmental and health benefits for the scenarios has been performed, based on the energy use and environmental emission results
presented for the base year. Considered were health effects such as mortality (i.e.,
premature death), morbidity (i.e., disease and sickness) and lost productive work
days, as well as such environmental effects as loss in yield of fish and crops, and
lost fishing days. Also, the costs associated with these health and environmental
effects were considered. The base-case values for these parameters, as well as the
reductions in them for each of the six cogeneration scenarios, are presented in Table
4. Clearly, the reductions in health and environmental effects and costs are significant for each of the scenarios considered. Most of the benefits are associated with
Table 4.
Annual reductions in health and environmental effects and costs for the base
case and six cogeneration scenarios
Health effectsa
Costs (million $)a
Environmental effects
Yield loss (%)
Cogeneration
scenario
Mortality
Base
A
B
C
D
E
F
18.9–25.7
3.0–4.2
8.5–10.3
2.2–3.1
2.8–3.9
3.4–4.8
8.5–11.7
Morbidity
Lost work
days
1,043
165
412
124
158
194
475
1 691,000
286,000
688,000
222,000
275,000
334,000
792,000
a
Health
Health and
environmentb
Fish
Crops
Lost
fishing
days
42.2
8.4
20.8
6.3
8.0
9.7
24.0
122.3
17.9
46.9
13.0
16.9
21.3
54.0
0.046
0.008
0.019
0.006
0.008
0.009
0.022
0.378
0.065
0.155
0.050
0.062
0.075
0.178
43,900
7,500
18,000
5,800
7,200
8,800
20,700
Values include occupational and public contributions for each of the coal and uranium sectors, as listed
in the source, and are in 1988 Canadian dollars.
b
Total includes health costs and environmental damage costs from coal use and catastrophic risk from
uranium use.
Source: Hart and Rosen [18].
International Journal of Low Carbon Technologies 2/2
Nuclear energy as a component of sustainable energy systems
123
the reductions in the use of fossil fuels, rather than nuclear energy. But some of the
benefits are due to a substitution of uranium for fossil fuels.
Cumulative assessment
The methodology used to assess the annual effects of utility-based cogeneration in
Ontario is applied here for years following the base year through to 2010. To modify
the base-case year, predictions are utilized of annual energy use and environmental
emissions to 2010 from the National Energy Board of Canada’s 1991 report “Canadian Energy Supply and Demand, 1990–2010” and data from Statistics Canada. The
base-case predictions for each year considered are evaluated noting that there is no
wood energy use in the residential sector and assuming utility-sector oil use is constant from 1990 to 2010 at 14 PJ yr−1, provincial coal use (excluding the utilitysector) is constant at 21 PJ yr−1, and agriculture-sector energy use is constant at
43 PJ yr−1. Annual emissions of SO2, NOx and CO2 from the electrical utility sector
are considered. The main cumulative results follow:
• Energy-utilization reductions: For scenarios A to F, reductions in provincial
energy use between 1989 and 2010 are evaluated for the utility sector, the nonutility sector and the total province. Reductions for electricity, natural gas and
NGLs, and oil and petroleum occur in the non-electrical-utility sectors, while the
reductions for coal and uranium occur in the utility sector, except for a small
portion of the coal reduction that occurs in the industrial portion of the non-utility
sector for scenarios C, D, E and F. The reductions in electricity, coal and uranium
use, respectively, range from as low as 414 PJ, 2358 PJ and 500 PJ (for scenario
C) to as high as 3587 PJ, 4328 PJ and 6057 PJ (for scenario F).
• Emissions reductions: For scenarios A to F, reductions in emissions of SO2, NOx
and CO2 by the utility-sector between 1989 and 2010 are evaluated. The reduction in utility-sector emissions of CO2 due to implementation of the cogeneration scenarios is particularly significant. The cumulative reduction in
utility-sector CO2 emissions ranges from as low as 156,200 kt (for scenario C) to
as high as 277,600 kt (for scenario F). Similarly, cumulative reductions in SO2
and NOx emissions, respectively, range from as low as 932 kt and 345 kt (for
scenario C) to as high as 1565 kt and 614 kt (for scenario F).
The cumulative reductions in energy use and related emissions would be significant.
The results obtained for 1989–2004 appear to be reasonably accurate, based on
actual data for that period, and the predictions for 2004–2010 remain sufficiently
reasonable for this investigation, where the benefits accrue with minor variations
from changes in energy use patterns.
Further discussion
Utility-based cogeneration can be implemented at Ontario’s thermal (nuclear and
fossil-fuel) stations in many ways, using current or advanced cogeneration technologies, and potential markets for utility-cogenerated heat exist in the province,
International Journal of Low Carbon Technologies 2/2
124
M. A. Rosen and I. Dincer
mainly in the residential-commercial and industrial sectors. Utility-based cogeneration would benefit Ontario in that the use of utility-based cogeneration in Ontario
can increase the utilization of nuclear energy by substituting it for other fuels, and,
for the same services delivered, cogeneration permits increased energy efficiency,
reduced environmental emissions and related environmental and health consequences, reduced energy consumption, and, based on experiences elsewhere, cost
savings and improved safety. It would therefore be worthwhile for Ontario, its electrical utility and other relevant stakeholders to investigate the options for cogeneration, and to develop and where appropriate implement a plan for utility-based
cogeneration designed for optimal provincial benefits. The choice is complex and
involves trade-offs.
Conclusions
Nuclear energy has many advantages over thermal power produced from fossil fuels,
particularly in the environmental and sustainability areas. A case study indicates that
regional utility-based cogeneration can be implemented at Ontario’s nuclear and
fossil-fuel stations and that potential markets for utility-cogenerated heat exist.
Utility-based cogeneration would benefit the region through increased substitution
of nuclear energy for fossil fuels and increased energy efficiency, reduced environmental emissions and related environmental and health consequences, reduced
energy consumption, and, based on experiences elsewhere, cost savings and
improved safety. Nuclear energy may consequently play a key role in sustainable
energy systems.
Acknowledgements
The authors are grateful for the support provided by the Natural Sciences and Engineering Research Council of Canada.
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