Energy, environmental, health and cost benefits of cogeneration from fossil fuels and nuclear energy using the electrical utility facilities of a province

Energy for Sustainable Development 13 (2009) 43–51

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Energy for Sustainable Development

Energy, environmental, health and cost benefits of cogeneration from fossil fuels and nuclear energy using the electrical utility facilities of a province Marc A. Rosen University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario, Canada L1H 7K4

a r t i c l e

i n f o

Article history: Received 26 January 2009 Accepted 26 January 2009 Keywords: Cogeneration Combined heat and power Emissions Efficiency Fossil fuel Nuclear energy

a b s t r a c t A method is investigated for increasing the utilization efficiency of energy resources and reducing environmental emissions, focusing on utility-scale cogeneration and the contributions of nuclear energy. A case study is presented for Ontario using the nuclear and fossil facilities of the main provincial electrical utility. Implementation of utility-based cogeneration in Ontario or a region with a similar energy system and attributes is seen to be able to reduce significantly annual and cumulative uranium and fossil fuel use and related emissions, provide economic benefits for the province and its electrical utility, and substitute nuclear energy for fossil fuels. The reduced emissions of greenhouse gases are significant, and indicate that utility-based cogeneration can contribute notably to efforts to combat climate change. Ontario and other regions with similar energy systems and characteristics would benefit from working with the regional electrical utilities and other relevant parties to implementing cogeneration in a careful and optimal manner. Implementation decisions need to balance the interests of the stakeholders when determining which cogeneration options to adopt and barriers to regional utility-based cogeneration need to be overcome. © 2009 International Energy Initiative. Published by Elsevier Inc. All rights reserved.

Introduction Cogeneration, which is the simultaneous production of thermal and electrical energy, has significant potential for transforming present energy supply systems so they are more sustainable. Thermal plants, such as fossil-fuel and nuclear 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 then converted to mechanical energy (in the form of a rotating shaft), which in turn is converted to electricity. A portion, normally 20% to 45%, of the heat is converted to electricity, and the remainder is rejected to the environment as a waste. Cogeneration systems are similar to thermal electricity-generation systems, except that some of the generated heat is delivered as a product, normally as steam or hot water, and the quantities produced of electricity and waste heat are reduced. Overall cogeneration efficiencies based on both the electrical and thermal energy products of 80% to 90% are achievable (Rosen, 1998). The main advantage of cogenerating thermal and electrical energy is that less input energy is consumed than would be required to produce the same products in separate processes. Additional benefits often include more economic, safe and reliable operation, as well as reduced environmental emissions (Rosen, 1998). The latter is primarily attributable to reduced energy consumption and the use of modern technologies in large, E-mail address: [email protected].

central installations. Note that the reduced emissions of greenhouse gases can be significant, allowing cogeneration to contribute notably to mitigating climate change. Cogeneration can be applied to plants of varying sizes, ranging from those for single buildings to utility-scale facilities. In this article, a method is investigated for dramatically increasing the utilization efficiency of energy resources and reducing the corresponding environmental emissions. This work focuses on electrical utilityscale cogeneration. The article is mainly in the form of a case study, which investigates the potential benefits of the simultaneous production of thermal and electrical energy via cogeneration using the facilities of the principal electrical utility in the province of Ontario, Canada, Ontario Power Generation (formerly Ontario Hydro). The assessments are applicable to Ontario and other regions with similar energy systems and characteristics. Ontario has a population of approximately 12 million, accounting for about one third of Canada's population. With an area of just over one million square kilometers, Ontario has a varied landscape, including the mineral-rich Canadian Shield, which separates the fertile farmland in the south and the grassy lowlands of the north. There are over 250,000 lakes in Ontario, containing approximately one-third of the world's fresh water. Ontario's climate varies widely over the year, with temperatures often exceeding 30 °C in summer and sometimes dropping below − 40 °C in winter. Ontario is one of Canada's main industrial provinces, with industries such as agriculture, mining, manufacturing, software and other leading-edge technology firms.

0973-0826/$ – see front matter © 2009 International Energy Initiative. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.esd.2009.01.005

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M.A. Rosen / Energy for Sustainable Development 13 (2009) 43–51

Background on cogeneration

Cogeneration plants have been analysed thermodynamically (Misa et al., 2007). Advanced thermodynamic analysis methods based on exergy (Dincer and Rosen, 2007) for assessing and improving efficiency have been applied to cogeneration facilities (Kanoglu et al., 2007; Dincer and Rosen, 2007) and related technologies such as district heating and cooling (Rosen et al., 2005). Exergy analysis is not applied in the present investigation, but is being considered in ongoing studies by the author of utility-based cogeneration. Design, synthesis and optimization aspects of cogeneration systems have also been examined. For example, design criteria have been identified for distributed cogeneration plants (Bertaa et al., 2006). Also, the synthesis of industrial utility systems has been examined in an effort to achieve decarbonisation cost effectively (Varbanov et al., 2005). The optimal design of gas turbine cogeneration plants, considering the discrete nature of equipment capabilities, was also studied recently (Yokoyama and Ito, 2006). Cogeneration based on new and advanced technologies has been proposed. In one energy analysis, for example, a cogeneration plant using coal gasification and solid oxide fuel cell is considered (Ghosh and De, 2006). Cogeneration systems incorporating cooling, commonly known as trigeneration systems, have also been assessed, e.g., the thermal integration of trigeneration systems was recently investigated (Teopa Calva et al., 2005) as was the improvement of district energy efficiency with trigeneration (Emho, 2003). Other factors relating to cogeneration have also been identified and examined. For instance, electrical aspects haves been studied, e.g., considerations for utility/cogeneration inter-tie protection (Rifaat, 1995), as have economic factors, e.g., demand charge considerations were studied in the optimization of cogeneration dispatch in the context of a deregulated energy market (Coffey and Kutrowski, 2006).

Technology considerations

Cogeneration and the existing electrical-utility supply system

Two main categories of heat demands can normally be satisfied through cogeneration:

For its current electrical generation, Ontario's electrical utility relies mainly on nuclear and hydraulic energy and fossil fuels (mainly coal). The overall station efficiency, based only on electrical energy, is taken to be 37% for coal-fired plants and 30% for nuclear plants (Rosen, 1998). The largest energy loss is the heat rejected from the condensers in cooling water. Thus, efficiency can be markedly improved for both types of plants if the thermal energy rejected by the condensers is used, i.e., if cogeneration is implemented. Many cogeneration systems are possible based on current coal and nuclear electrical stations in Ontario. For example, 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 (Ontario Hydro, 1984) 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 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 on-site heavy-water production plant and the Bruce Energy Centre, a nearby industrial park. A significant degree of flexibility exists in the current system for utility-based cogeneration within both individual station units and multiple unit stations. In addition, many enhancements of the existing system are possible using advanced cogeneration technologies. Although many existing and proposed cogeneration systems utilize natural gas as their fuel, the present work concentrates on those fuels presently used by Ontario's electrical utility; natural gas-based cogeneration systems are thus not considered, although future schemes in the province for utility-based cogeneration may involve gas-fired systems. Moreover, natural gas can be used in combined

The case study: •

•

considers the annual and cumulative (over 20 years) benefits of utility-based cogeneration for Ontario, relative to the business-asusual situation in Ontario where cogeneration is applied only in a very limited manner, and focuses on the utilization phase of the life cycle for the relevant cogeneration infrastructure since, due to the long life times of such systems (usually well over 20 years), the environmental impacts are concentrated in that phase.

This data for the study reported here are based on investigations carried out by the author in the mid-1990s, but the primary results are reasonably valid today. A validation of the results to ensure they are representative of the present is provided in the Validation of results section. Alternatively, the case study can be viewed as applicable to a hypothetical region with characteristics similar to those of Ontario at the time considered. Related studies of the economic, environmental and health benefits of regional utility-based cogeneration and district energy in Ontario and Canada have been carried out (Diener and Cain, 1993; FVB/Eltec. 1993; MacRae, 1992; Rogner, 1993). Also, analyses such as the one reported here have been carried out for many similar technologies, e.g., a comparative assessment of environmental and health impacts of electrical power generation, including nuclear-based processes, has been reported by Rashad and Hammad (2000). Options for nuclear energy beyond electricity generation, including the provision of heating, have been investigated (Soutworth et al., 2007) and are important given the predictions for increased nuclear energy utilization (Rogner et al., 2008a, 2008b; Cleveland, 2008; Toth, 2008).

•

•

Residential, commercial and institutional processes, which require large quantities of heat at relatively low temperatures (e.g., for heating air and water). Industrial processes, which require heat at a wide range of temperatures (e.g., for drying, heating and boiling in various industries including resource extraction, chemical and petrochemical processing, metal processing, fertilizer production, manufacturing, cement production, construction, pulp and paper processing, forestry, agriculture).

The use of a central heat supply to meet the heat demands of the residential–commercial sector (which is taken here to include the institutional sector) is often referred to as district heating, and has been applied extensively. It is noted that cogenerated heat can even be used to drive absorption chillers for space cooling, rather than using more conventional electrically driven chillers. Many types and applications of cogeneration systems exist. Cogeneration systems are in use throughout the world (e.g., over 4000 are listed in the Association of Energy Engineers' cogeneration database). Most of these are based on fossil-fuels. The size and type of a cogeneration system are normally selected to match as optimally as possible the thermal and electrical demands. Recent developments in cogeneration Cogeneration has been investigated recently from many perspectives. In Canada, for instance, the prospects have been examined for cogenerating heat and electricity from CANDU nuclear power plants (Burnstaple and Tong, 1984). Also, residential total energy systems incorporating cogeneration have been studied (Gusdorf et al., 2008).

M.A. Rosen / Energy for Sustainable Development 13 (2009) 43–51

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Table 1 Annual energy use by sector in natural units for 1990 Electricity (TWh) Natural gas and NGLsa (teraliters) Oil and petroleum (gigaliters) Coal (megatons) Otherb (kilotons) Uranium (tons)

Sector

Province 132 Province (excluding utility sector) 132 c Utility sector – a b c

21.0 21.0 –

21.8 21.5 0.33

•

Thermal energy demands and potential markets Potential markets in Ontario for utility-cogenerated thermal energy, which exist mainly in the residential, commercial, institutional and industrial sectors, are a portion of the total thermal-energy demands. These markets depend on many technical factors: Heat characteristics: 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. Note that coal and nuclear power plants are based on steam turbines from which waste heat is normally available at relatively low temperatures, but higher temperatures can be attained, e.g., high-pressure steam for industrial applications, provided one is willing to tolerate a significant loss in electrical power output. Heat availability: Heat must 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. This factor is particularly important if the thermal energy distribution is accomplished via a network, e.g., a district heating system. Given nuclear plants tend to be few, large and separated by large distances, rather than spread out geographically, the potential contributions for nuclearderived heat are lower than those for fossil-derived heat. Infrastructure: An overall infrastructure and all relevant technologies must exist for all cogeneration steps, including heat supply, distribution, storage and utilization.

•

•

•

Attitude: The attitude towards the idea must be positive for all parties involved, including suppliers, distributors, users and others.

Sector

Coal Other Uraniumb Totalc Electricity Natural Oil and gas and petroleum NGLs

Province Province (excluding utility sector) Utility sector

477 477

824 824

–

–

b c

796 782

307 21

158 158

640 –

3200 2260

14

286

–

640

940

Notes on NGLs, others and hydraulic energy are as in Table 1. Uranium energy of is taken to be heat delivered by fission. The total column is the sum of the rows.

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 (e.g., environmental), cogeneration alternatives may be considered even if the specific application is not economically competitive.

Multiple scenarios are considered in which the effects of implementing electrical utility-based cogeneration are examined for the province. The scenarios are assessed by evaluating the changes in quantities such as energy consumption, environmental emissions and impacts, health effects and environmental and health costs when cogeneration is implemented, relative to a base year. The effects of implementing the cogeneration scenarios are considered for • •

a one-year period for a base year, and a period of 20 years. The latter assessment ascertains the cumulative effects over time of implementing the cogeneration scenarios.

To provide a finer understanding, the effects of cogeneration implementation on the overall province for the annual assessments of the scenarios are broken down into those associated with the electrical-utility sector and those associated with the remainder of Ontario, i.e., the province excluding the utility sector. Base case Data for the base year, relative to which the scenario are assessed, are provided in tabular form for various parameters. Specifically, the following are listed for the province for the base year (1990): •

• •

•

Table 2 Annual energy use by sector (PJ)a for 1990

a

1040 – 1040

Scenarios for utility-based cogeneration

Potential markets in Ontario for utility-cogenerated thermal energy also depend on important non-technical factors: •

5340 5340 –

NGLs denotes natural gas liquids. “Other” includes coke and coke oven gases, originally from coal. Hydraulic energy use is not shown.

cycle systems that convert fuel energy to electricity at high efficiency, leaving smaller amounts of waste heat (at very low temperature) available. Biomass systems are also not considered since they have limited application in utility-scale cogeneration, even though biomass use in Ontario is growing.

•

11.1 0.71 10.4

•

Energy-use data, in natural units (Table 1) and in energy units (Table 2). The total column in Table 2 is the sum of the rows, i.e., the annual provincial energy use (3200 PJ) includes the values to the left for the primary energy forms and the secondary form, electricity. Environmental emissions (Table 3). Selected health data, including mortality (i.e., premature death), morbidity (i.e., disease and sickness) and lost productive work days (Table 4). Selected environmental impacts, such as loss in yield of fish and crops and lost fishing days (Table 5). Costs associated with health and environmental effects given in Tables 4 and 5 (Table 6). Values in the table include occupational and public contributions for the coal and uranium sectors, as provided by Hart and Rosen (1994). Considered are health costs and environmental damage costs from coal use and catastrophic risk from uranium use.

As noted earlier, data for the base year are taken or adapted from previous investigations by the author, including Rosen (1994) for Tables 1–3 and Hart and Rosen (1994) for Tables 4–6. Values in Table 6

46

M.A. Rosen / Energy for Sustainable Development 13 (2009) 43–51

Table 3 Annual emissions by sector for 1990 Sector

Material emissions (kilotons)

Province Province (excluding utility sector) Utility sector a b c

SO2

NOX

CO2

CO

Particulates

V.O.C.

Spent uranium

1380 1060 321

618 526 92

164,000 132,000 32,000

3504 3500 4

849 837 11

775 775 0.5

1.04 – 1.04

Thermal pollutionb (PJ)

Radiationc (1015 Bq)

591 – 591

11 – 11

V.O.C. denotes volatile organic compound. Thermal pollution is heat emitted to bodies of water that cause appreciable temperature rise. Radioactive emissions from non-nuclear-energy sources are not accounted for, e.g., radioactivity in coal-station stack gases.

have been modified to 2007 Canadian dollars by adjusting the original data using the Consumer Price Index (CPI) tabulated by Statistics Canada (accessible at http://www40.statcan.ca/l01/cst01/econ46a. htm). The CPI data, which represents changes in prices of all goods and services purchased for consumption, indicates the need to apply a factor of 1.57 to the original costs. Scenarios Six scenarios are considered, based on the 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 details for each scenario are provided in Table 7. The scenarios are intended to 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 number of scenarios is intended to be sufficient to illustrate the potential benefits of utility-based cogeneration over the range of viable implementation possibilities, but limited enough to avoid confusion. The scenarios consider two potential cogenerated-heat users: the residential–commercial and industrial sectors. Based on data in Statistics Canada's “Quarterly Reports on Energy Supply-Demand in Canada,” the annual heat demand in Ontario in the base year was 514.5 PJ for the residential–commercial sector, and 414 PJ for the industrial sector (Rosen, 1994). The residential–commercial demands are almost exclusively for low-temperature heat for space and water heating. As building space heat demand varies seasonally, the thermal energy demands were broken down seasonally to quantify better the thermal demands. The industrial heat demand is for various tasks and can be approximately broken down as follows: • • •

a

14% at low temperatures (b125 °C), 36% at medium temperatures (125 °C to 400 °C), and 50% at high temperatures (N400 °C).

Station in Ontario has eight individual units consisting of a nuclear reactor and the associated power generation equipment. Although the distinction between conventional and advanced cogeneration is not completely clear, it is noted that in this study conventional cogeneration technologies are taken to include steam power plant cogeneration, gas turbine cogeneration and diesel engine cogeneration, while advanced cogeneration technologies are taken to include combined-cycle cogeneration, fluid-bed cogeneration and fuel cell cogeneration. For the advanced network, government intervention through legislation and incentives to promote cogeneration is assumed sufficiently great to result in significant market penetration for cogeneration and the perception of cogeneration as a conventional heating technology. Thermal energy storage is used in both networks, especially for coal stations, which operate much more intermittently than nuclear stations. Based on data for Ontario's electrical generating stations, for both networks (i) overall efficiencies are taken to be 85% for nuclear or coal cogeneration, (ii) electrical efficiencies (in %) are approximated by the expressions 32 − (0.11)T for nuclear cogeneration and 40 − (0.074)T for coal cogeneration, where T denotes the cogeneratedheat temperature (in °C), and (iii) thermal efficiencies are given by the differences between the corresponding overall and electrical efficiencies (Rosen, 1998). In all scenarios, half of the cogenerated heat is used to offset electricity provided by the electrical utility to users for heating. The other half of the cogenerated heat is used to offset the nonelectrical utility energy resources (e.g., natural gas and oil) used by others for heating. 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 non-cogenerating coal and nuclear generating stations are used, again in the same proportions as cited above.

The scenarios consider two hypothetical utility-based cogeneration networks: basic and advanced. The basic network consists of the current provincial network of thermal electrical stations, with only minor cogeneration modifications implemented in some nuclear and coal stations. The advanced network consists of a modified network, where some multi-unit stations are separated and located near heat demands, and where advanced cogeneration technologies are used along with current-technology thermal stations modified for cogeneration. The term multi-unit stations is used here to refer to the fact that many utility-scale plants have multiple power plant units, e.g., the Pickering Nuclear Generating

Thermal demands satisfied with cogenerated heat

Table 4 Annual values for health parameters for 1990

Table 5 Annual values for environmental parameters for 1990

Mortality

Morbidity

Lower

Upper

18.9

25.7

1043

Lost work days 1,691,000

The portions of the heat demands to be met by utility-cogenerated heat are estimated by considering the factors discussed in the Thermal energy demands and potential markets section. The main factors involved here in deciding to use utility-cogenerated heat are taken to be distance, infrastructure, attitude, economics and temperature. It is assumed for the residential–commercial sector that •

utility-cogenerated heat temperatures permit for all scenarios 100% of the heat demands to be satisfied, as they are all at low temperatures;

Lost fishing days

Yield loss (%) Fish

Crops

0.046

0.378

43,900

M.A. Rosen / Energy for Sustainable Development 13 (2009) 43–51 Table 6 Annual health and environmental costs for 1990a

47

Table 8 Percentage of utility fuel used for cogeneration

Health cost ($)

Health and environmental cost ($)

Scenario

Coal

Uranium

66,200,000

192,000,000

A B C D E F

12 77 6 13 22 100

8 49 4 2 12 49

a

•

Values are in 2007 Canadian dollars.

35% of heat demands are within a serviceable distance of the cogeneration plant for scenario A, and 60% for scenario B; and 25% of potential users find the infrastructure/attitude/economic conditions favourable enough to use cogenerated heat for scenario A, and 65% for scenario B.

•

It is assumed for the industrial sector that •

Approach and methodology

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; 30% of low-, 23% of medium- and 15% of high-temperature demands are located within a serviceable distance of the cogeneration plant for scenario C, while the corresponding values are 60%, 45% and 30% for scenario D; and 40% of potential users find the infrastructure/attitude/economic conditions favourable enough to use cogenerated heat for scenarios C and D.

•

•

Consequently, the six scenarios considered can be quantitatively described as follows: A a basic utility-based cogeneration network supplies a small portion (9%) of the annual heat demand of the residential–commercial sector; B an advanced utility-based cogeneration network supplies a significant portion (40%) of the annual heat demand of the residential–commercial sector; C a basic utility-based cogeneration network supplies a small portion (6%) of the annual heat demand of the industrial sector; D an advanced utility-based cogeneration network supplies a significant portion (12%) of the annual heat demand of the industrial sector; E a basic utility-based cogeneration network simultaneously supplies the portions of the heat demands for the residential– commercial and industrial sectors referred to in scenarios A and C, respectively; and F an advanced utility-based cogeneration network simultaneously supplies the portions of the heat demands for the residential–

Table 7 Descriptions of the electrical utility-based cogeneration scenarios Scenario

Type of utility-based cogeneration networka

Sector receiving utility-cogenerated heat

Proportion of sector heat demands met via utility-based cogeneration

A B C D E

Basic Advanced Basic Advanced Basic

Small Large Small Large Small

F

Advanced

Residential–commercial Residential–commercial Industrial Industrial Residential–commercial and industrial Residential–commercial and industrial

a

commercial and industrial sectors referred to in scenarios B and D, respectively.

Large

The basic network is comprised of the current provincial network of thermal electrical stations with only minor cogeneration modifications to some nuclear and coal stations, while the advanced network is a hypothetical network in which some multi-unit stations are separated and located near heat demands, advanced cogeneration technologies are used and current thermal electrical stations are modified to support cogeneration.

In this study, the six cogeneration scenarios identified previously are investigated, utilizing data described earlier regarding: •

•

The thermal energy supply available from present-day fossil fuel and nuclear power plants with cogeneration as well as hypothetical advanced power generation networks that may exist in the future. The thermal energy demands for the scenarios as determined using the assumptions identified early. This approach first evaluates the total potential thermal demand in the province and then reduces it using practical factors and constraints to only that portion which can reasonably be expected to be satisfied via cogeneration.

Both annual and cumulative assessments are carried out. The annual assessment considers a one-year period, while the cumulative assessment considers a multi-year period and integrates the annual results over the period covered. A 20-year period is considered in the cumulative assessment carried out in this paper. Although the annual assessment is simpler, it does not account for the fact that systems change over time, e.g., new cogeneration systems may be installed, or existing power plants may modified to permit cogeneration. The cumulative assessment can account for such changes, as each future year after the base year is treated individually. Results and discussion for annual assessment Annual assessment results for the cogeneration scenarios are presented relating to the utility sector, where cogeneration occurs, and the residential–commercial and industrial sectors, which use the cogenerated heat. The percentage of coal and uranium that are used for cogeneration in coal and nuclear power plants, respectively, are listed in Table 8 (Rosen, 1994). The thermal energy requirements supplied by cogeneration in the residential–commercial and industrial sectors have been adapted from earlier work (Rosen, 1994) and are presented in Table 9. Note that the percentage values in that table apply to the columns. For instance, the values in the second column in Table 9 provide the percentage of the total heat demand in the residential/commercial sector met via cogeneration, while the values in the rightmost column provide the

Table 9 Percentage of annual heat demand met by cogeneration, by sector Scenario

Residential–commercial

Industrial

Total

A B C D E F

9 40 0 0 9 40

0 0 6 13 6 13

5 22 3 6 8 28

48

M.A. Rosen / Energy for Sustainable Development 13 (2009) 43–51

Table 10 Percentage reductions in annual provincial energy use Scenario A B C D E F

Electricity 5.3 24 3.0 6.3 8.3 30

a

Natural gas and NGLsa

Oil and petroleum

Coal

2.8 13 1.2 2.4 4.0 15

0.5 2.0 0.3 0.6 0.7 2.6

17 38 13 16 19 44

Table 12 Percentage reductions in annual provincial energy use in utility sectora Other 0.5 2.3 2.5 5.1 3.0 7.5

Uranium 6.8 30 2.5 5.3 9.4 35

Total 4.6 17 2.7 4.5 6.3 21

Energy use (for the province in Table 10, for the province excluding the utility sector in Table 11 and for the utility sector in Table 12). Uranium is not shown in Table 11 because it is not used outside the utility sector. Similarly, electricity, natural gas and NGLs, oil and petroleum and others are not shown in Table 12 because the use of each in the utility sector does not change for the cogeneration scenarios. Environmental emissions (for the province in Table 13, for the province excluding the utility sector in Table 14 and for the utility sector in Table 15). Spent uranium, thermal pollution and radiation are not shown in Table 14 because emissions of each in the province excluding the utility sector do not change for the cogeneration scenarios. Health measures for the province (Table 16). Environmental impacts for the province (Table 17). Costs associated with health and environmental effects for the province (Table 18).

•

• • •

Note that the results in Tables 10–18 are all expressed as a percentage change relative to the corresponding values for the base year. Note also that the percentage reductions in annual energy use listed in Tables 10–12 can be applied to the energy data in either natural units (Table 1) or energy units (Table 2). Furthermore, note that the environmental and health benefits associated with the scenarios are a direct outcome of the energy use and environmental emission reductions. The results in Tables 10–15 have been taken or adapted from Rosen (1994) and in Tables 16–18 from Hart and Rosen (1994). Note that the impact of cogeneration as determined by the scenarios depends on the extent of utility cogeneration already present in the base year. In the case of Ontario, very little utility-based cogeneration was used during the base year. Also, little new cogeneration has progressed since then, so the potential benefits identified in the scenario assessments remain untapped. Some of the

Total

6.8 30 2.5 5.3 9.4 35

10 33 5.8 8.6 13 38

a

Only quantities that change are shown.

Electricity

Natural gas and NGLsb

Oil and petroleum

Coal

Other

Total

A B C D E F

5.3 24 3.0 6.3 8.3 30

2.8 13 1.2 2.4 4.0 15

0.5 2.1 0.3 0.6 0.7 2.6

0 0 2.7 5.6 2.7 5.6

0.5 2.3 2.5 5.1 3.0 7.5

2.4 10 1.4 2.8 3.7 13

Only quantities that change are shown. NGLs denotes natural gas liquids.

barriers that have prevented the cogeneration potential to be attained include the following: •

The requirement for a significant up-front investment to attain financial savings over the life of the system. The need to reach an agreement among the many stakeholders involved in the provision of cogenerated services, including local and provincial governments, electrical utilities, fossil fuel companies and industry, as well as the potential users of electricity and heating/cooling. The need to balance the interests of the stakeholders can be especially challenging when utility-based cogeneration is regional in extent. The expectation for a large number of customers to agree to purchase the cogenerated heating or cooling, often for a long-term period (e.g., five or ten years), to remove the financial risk for those making the investment in utility-based cogeneration.

•

•

The key points demonstrated in Tables 10–18 are that, for all scenarios considered, energy use and environmental emissions as well as health and environmental impacts and costs, decrease for each of the overall province, the electrical utility sector, and the rest of the province. In addition, provincial electricity-generation requirements decrease for all scenarios. 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%. The reductions determined in health and environmental effects and costs are clearly significant for each of the scenarios considered. It is noted that most of the environmental benefits are associated with the reductions in the use of fossil fuels, rather than nuclear energy. But a portion of the benefits are due to a substitution of uranium for fossil fuels. The reductions obtained in mortality, morbidity and lost productive work days do not provide a comprehensive assessment of health effects, but they do suggest that the cogeneration scenarios bring health benefits. Similarly, the reductions identified in yield loss of fish and crops as well as lost fishing days are not representative of all environmental impacts, and those results suggest that additional environmental advantages may be obtainable. Similar statements can be made regarding health and environmental costs. As a consequence, it is felt by the author that further investigations appear to be merited to identify and quantify additional advantages associated with health effects, environmental impacts, and health and environmental costs.

Scenario Material emissions

Scenario

b

Uranium

17 41 13 16 20 47

Table 13 Percentage reductions in annual provincial emissionsa

Table 11 Percentage reductions in annual provincial energy use excluding utility sectora

a

Coal

A B C D E F

NGLs denotes natural gas liquids.

percentage of the total heat demand in the combined residential/ commercial and industrial sectors met via cogeneration. The results of the annual scenario assessment are provided in Tables 10–18. For the most part, the result tables follow the corresponding formats in Tables 2–5. Specifically, percentage annual reductions in Ontario are presented for the following: •

Scenario

SO2 A B C D E F

NOX CO2

4.9 3.2 4.2 14 9.0 12 4.3 2.5 3.3 6.5 3.8 4.9 6.8 4.2 5.2 18 12 15 a

Thermal Radiation pollution

CO Particulates V.O.C. Spent uranium 0.8 3.4 0.5 0.9 1.2 4.2

0.5 1.7 0.4 0.6 0.7 2.1

0.5 2.3 0.3 0.7 0.8 3.0

6.8 30 2.5 5.3 9.4 35

15 69 6.7 14 22 83

6.8 30 2.5 5.3 9.4 35

Notes on V.O.C., thermal pollution and radioactive emissions are as in Table 3.

M.A. Rosen / Energy for Sustainable Development 13 (2009) 43–51 Table 14 Percentage reductions in annual provincial emissions excluding utility sectora Scenario

a b

Table 16 Percentage reductions in annual provincial health parameters Scenario

Material emissions

A B C D E F

SO2

NOX

CO2

CO

Particulates

V.O.C.b

1.2 5.5 2.7 3.4 2.9 8.8

0.7 3.4 0.7 1.5 1.5 4.8

1.2 5.5 1.0 2.1 1.7 7.4

0.7 3.4 0.4 0.9 1.2 4.2

0.3 1.2 0.2 0.4 0.5 1.6

0.5 2.3 0.3 0.7 1.7 2.9

Only quantities that change are shown. V.O.C. denotes volatile organic compound.

Some key annual results in Tables 10–18 for each scenario are highlighted in Table 19, including the reductions in fuel use by the electrical utility as well as electricity consumption and carbon dioxide emissions in the province. Specific implications of these findings are significant: •

Annual uranium use by the electrical utility and related emissions decrease for all scenarios, by between 3% for low penetration of utility-based cogeneration and 35% for high penetration. Annual coal use by the electrical utility and coal-related emissions decrease for all scenarios, by between 13% and 47%. Annual provincial electricity consumption decreases for all scenarios, by between 3% and 30%, thereby permitting provincial electrical generation to decrease by corresponding percentages. Annual emissions of carbon dioxide decrease for all scenarios, by between 3% and 15% for the province and by between 13% and 47% for the electrical utility sector. Given that carbon dioxide is the principal greenhouse gas, it is evident that utility-based cogeneration can contribute significantly to mitigating its contribution to global warming and, subsequently, climate change.

• •

•

Results and discussion for cumulative assessment In the cumulative assessment of the benefits of utility-based cogeneration in Ontario, the annual effects reported in the previous section are extended for 20 years following the base year. Methodology The general characteristics of the six scenarios considered in the previous section are unchanged in the cumulative assessment, but data for the base year are modified for future years. The scenarioassessment procedure for the original base year is then applied to each new base year so as to determine the reductions in energy use and emissions for that year. The cumulative assessment follows the method applied in a previous investigation by the author (Rosen and Le, 1994). But here the results for the prior assessment are scaled to a 20-year time frame. To modify the base year, past predictions from the National Energy Board of Canada are utilized of future annual energy use and Table 15 Percentage reductions in annual provincial emissions by utility sectora Scenario Material emissions

Thermal Radiation pollution

SO2 NOX CO2 CO Particulates V.O.C. Spent uranium A B C D E F

17 41 13 17 20 47 a

17 41 13 17 20 47

17 41 13 17 20 47

17 41 13 17 20 47

17 41 13 17 20 47

17 41 13 17 20 47

6.8 30 2.5 5.3 9.4 35

15 69 6.7 14 22 83

49

6.8 30 2.5 5.3 9.4 35

Notes on V.O.C., thermal pollution and radioactive emissions are as in Table 4.

A B C D E F

Mortality Lower

Upper

16 45 12 15 18 45

16 40 13 15 19 46

Morbidity

Lost work days

16 40 12 15 19 46

17 41 13 16 20 47

environmental emissions. The predictions were selected to correlate with the base-year data considered in the previous section (Rosen and Le, 1994; National Energy Board of Canada, 1991). The predictions for each year considered are evaluated noting that there is no wood energy use in the residential sector and assuming the following: • • •

utility-sector oil use, provincial coal use (excluding the utilitysector) and agriculture-sector energy use are all constant, the fuel breakdown for space and hot water heating in the annual assessment remains unchanged, and the reductions in environmental emissions are proportional to the reductions in the use of the fuels from which the emissions originate.

Annual emissions to the environment of SO2, NOx and CO2 from the electrical utility sector are considered. The modified base-year emissions are also based on projections by the National Energy Board of Canada (1991). Reductions in energy utilization For scenarios A to F, annual and cumulative reductions in provincial energy use over 20 years are evaluated for the utility sector, the non-utility sector and the total province. Five energy forms are considered: electricity, natural gas and natural-gas liquids (NGLs), oil and petroleum, coal, and uranium. It is observed for the cogeneration scenarios that the approximate cumulative reductions over 20 years in usage for electricity, coal and uranium, respectively, range from as low as 400 PJ, 2100 PJ and 500 PJ (for scenario C) to as high as 3300 PJ, 3900 PJ and 5500 PJ (for scenario F). The annual and cumulative reductions for electricity, natural gas and NGLs, and oil and petroleum occur predominantly in the nonelectrical-utility sectors of the province, while the reductions for coal and uranium occur mainly in the utility sector. A small part of the coal reduction occurs within the industrial portion of the non-utility sector for scenarios C, D, E and F. It is noted that the reductions in the utilization of the primary energy forms coal and uranium are not independent of the reduction in the utilization of the secondary energy form electricity. Rather, the reduction in electricity use for heating, achieved through the use of cogenerated heat in its place, leads to reduced requirements for the coal and uranium used to generate the electricity. The scenario-assessment results therefore indicate that the cumulative reductions over 20 years in energy use would be significant due to implementation of a utility-based cogeneration program. Reductions in environmental emissions For scenarios A to F, annual and cumulative reductions in emissions of SO2, NOx and CO2 by the utility-sector over 20 years are evaluated. It is shown that the cumulative reduction in utility-sector CO2 emissions ranges from as low as 140,000 kt (for scenario C) to as high as 250,000 kt (for scenario F). The reduction in utility-sector emissions of CO2 due to implementation of the cogeneration scenarios is particularly significant, given its role in climate change.

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M.A. Rosen / Energy for Sustainable Development 13 (2009) 43–51

Table 17 Percentage reductions in annual provincial environmental parameters Scenario A B C D E F

Lost fishing days

Yield loss (%) Fish

Crops

17 41 13 17 20 48

17 41 13 16 20 47

17 41 13 16 20 47

Similarly, cumulative reductions in SO2 and NOx emissions, respectively, range from as low as 900 kt and 300 kt (for scenario C) to as high as 1400 kt and 600 kt (for scenario F). The associated environmental benefits regarding acid precipitation, smog and other impacts would be significant. The scenario assessments consequently illustrate that the cumulative reductions over 20 years in energy-related environmental emissions associated with implementation of utility-based cogeneration would be significant. Validation of results The annual assessments, as pointed out earlier, are based on investigations carried out by the author in the mid-1990s (Rosen, 1994; Hart and Rosen, 1994; Rosen and Le, 1994). Although there have been significant changes in Ontario since then, the results have been shown by the author to be somewhat valid today, in terms of percentage reductions in energy use, environmental emissions, and environmental impacts and costs. The rationale for this result, which validates the main data of the annual assessments, is provided here. A comparison of data for the base year used in this study with those in Ontario for 2006, as reported several references (Statistics Canada, 2007, 2008), reveals that data for the base year has changed since the study was first carried out. For instance, as of 2006, the annual use of natural gas and natural gas liquids has increased by 40%, of oil and petroleum has increased by 65%, of coal has increased by 60%, and of electricity has increased by 16%. Also, the energy use in the province, excluding the utility sector, has increased by 15%. Thus the base-year values in Tables 1–6 likely understate data for the present year. However, the results of the annual assessments reported here are provided in percentage terms. Given that less significant changes have been observed in the ratios of energy supply among the different key commodities or the ratios of energy supply to sectoral thermal demands, the percentage reductions in energy use (see Tables 10–12), environmental emissions (Tables 13–15), and environmental impacts and costs (Tables 16–18) have not changed markedly. Similarly, the results reported for fractional fuel cogeneration (Table 8) and fractional sectoral thermal demands met via cogeneration (Table 9), as well as the summary results (Table 19), have not varied significantly. The cumulative assessment results reported here, being based on a 20-year period corresponding to earlier assessments (Rosen and Le,

Table 18 Percentage reductions in annual provincial health and environmental costs Scenario

Health cost

Health and environment cost

A B C D E F

20 49 15 19 23 57

15 38 11 14 17 44

Table 19 Percentage reductions in key consumption and emission parameters Scenario Utility-sector Utility-sector Provincial electricity Carbon dioxide coal use uranium use consumption emissions Utility sector Province A B C D E F

17 41 13 16 20 47

7 30 3 5 9 35

5 24 3 6 8 30

17 41 13 17 20 47

4 12 3 5 5 15

1994), likely underestimate the values that would be predicted for a 20-year period starting at present. The underestimation is likely on the order of 20–50%. Nevertheless, the cumulative results serve to illustrate the significance over time of the benefits of introducing electrical utility-based cogeneration. Conclusions The case study suggests that electrical utility-based cogeneration would benefit Ontario or a region with similar characteristics and energy systems in that (i) cogeneration can be implemented at the province's thermal (nuclear and fossil-fuel) stations in many ways; (ii) potential markets for utility-cogenerated heat exist in the province, mainly in the residential–commercial and industrial sectors; (iii) for the same services delivered, cogeneration permits increased efficiency, reduced energy consumption and related emissions, reduced environmental and health consequences and, based on experiences elsewhere, cost savings and improved safety; and (iv) the use of utility-based cogeneration in the province can increase the utilization of nuclear energy by substituting it for other fuels. It would therefore be worthwhile for Ontario, its electrical utilities and other relevant parties 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 same observation applies to other regions with similar energy systems and characteristics. Implementation decisions are complex and must involve the many stakeholders involved, including local and provincial governments, electrical utilities, electricity and heating/cooling customers, fossil fuel companies and industry. The interests of the stakeholders where they differ need to be balanced in determining which cogeneration options to adopt and barriers to regional utilitybased cogeneration need to be overcome. Acknowledgment The author is grateful for the support provided by the Natural Sciences and Engineering Research Council of Canada.

References Bertaa GL, Pratob AP, Garbarino L. Design criteria for distributed cogeneration plants. Energy 2006;31(10–11):1403–16. Burnstaple AG, Tong WS. Co-generation of heat using CANDU nuclear power plants. Proc. Am. Soc. Mech. Eng. Joint Power Generation Conference, Vol. 84-JPGC-NE-4, 30 Sept., Toronto, Canada; 1984. Cleveland J. Advanced plants to meet rising expectations for nuclear power. Int. J. Global Energy Issues 2008;30(1–4):393–412. Coffey B, Kutrowski E. Demand charge considerations in the optimization of cogeneration dispatch in a deregulated energy market. Int. J. Energy Res. 2006;30 (7):535–51. Diener SG, Cain SR. Achieving the economic potential for industrial cogeneration in Ontario: a financial perspective on electric utility policy. Energy Stud. Rev. 1993;5 (3):180–9. Dincer I, Rosen MA. Exergy: energy, environment and sustainable development. Oxford, UK: Elsevier; 2007. Emho L. District energy efficiency improvement with trigeneration: basic considerations and case studies. Energy Eng.: J. Assoc. Energy Eng. 2003;100(2):66–80.

M.A. Rosen / Energy for Sustainable Development 13 (2009) 43–51 FVB/Eltec. Potential heat production from existing and future electric generating plants, Report No. 9102-G-806 for the Canadian Electrical Association; 1993. Ghosh S, De S. Energy analysis of a cogeneration plant using coal gasification and solid oxide fuel cell. Energy 2006;31(2–3):345–63. Gusdorf J, Douglas MA, Szadkowski F, Yang L, Limouse E, Manning M, Swinton M. Residential total energy system installation at the Canadian Centre for Housing Technology. Cogener. Distributed Gener. J. 2008;23(1):33–51. Hart DR, Rosen MA. Environmental and health benefits of utility-based cogeneration in Ontario, Canada. Energy Environ. 1994;5:363–78. Kanoglu M, Dincer I, Rosen MA. Exergetic performance analysis of various cogeneration systems for buildings. ASHRAE Trans. 2007;113(Part 2):105–12. MacRae KM. Realizing the benefits of community integrated energy systems. Calgary, Alberta: Canadian Energy Research Institute; 1992. Misa T, Crisford M, Jain S, Bansal PK. Thermodynamic analysis of an in-situ cogeneration plant. Proc. Inst. Mech. Eng., Part A: J. Power Energy 2007;221(5):591–602. National Energy Board of Canada. Canadian energy supply and demand, 1990–2010; 1991. Ontario Hydro. Heat energy locations in Ontario. Information brochure. Toronto: New Business Ventures Division; 1984. Rashad SM, Hammad FH. Nuclear power and the environment comparative assessment of environmental and health impacts of electricity-generating systems. Appl. Energy 2000;65(1–4):211–29. Rifaat RM. Critical considerations for utility/cogeneration inter-tie protection scheme configuration. IEEE Trans. Ind. Appl. 1995;31(5):973–7. Rogner HH. Clean energy services without pain: district energy systems. Energy Stud. Rev. 1993;5(2):114–20. Rogner HH, McDonald A, Riahi K. Long-term performance targets for nuclear energy. Part 1: The global scenario context. Int. J. Global Energy Issues 2008a;30(1–4):28–76.

51

Rogner HH, McDonald A, Riahi K. Long-term performance targets for nuclear energy. Part 2: Markets and learning rates. Int. J. Global Energy Issues 2008b;30(1–4):77-101. Rosen MA. Assessment of various scenarios for utility-based cogeneration in Ontario. Energy Int. J. 1994;19:1143–9. Rosen MA. Reductions in energy use and environmental emissions achievable with utility-based cogeneration: simplified illustrations for Ontario. Appl. Energy 1998;61(3):163–74. Rosen MA, Le M. Assessment of the potential cumulative benefits of applying utilitybased cogeneration in Ontario. Energy Stud. Rev. 1994;6:154–63. Rosen MA, Le MN, Dincer I. Efficiency analysis of a cogeneration and district energy system. Appl. Therm. Eng. 2005;25(1):147–59. Soutworth F, Gauthier JC, Lecomte M, Carre F. Potential applications for nuclear energy besides electricity generation: AREVA global perspective of HTR potential market. Proc. Conf. on Advanced Nuclear Fuel Cycles and Systems (GLOBAL 2007), Boise, Idaho, U.S., 9–13 Sept.,; 2007. p. 1563–74. Statistics Canada. Energy supply and demand: 2006. The Daily, Dec. 20; 2007. Statistics Canada. Primary and secondary energy — Ontario. Tables 1–8 and 2–8 in Report on Energy Supply-Demand in Canada — 2006. Report 57-003-X, June 3; 2008. Teopa Calva E, Picón Núñez M, Rodríguez Toral MA. Thermal integration of trigeneration systems. Appl. Therm. Eng. 2005;25(7):973–84. Toth FL. Prospects for nuclear power in the 21st century: a world tour. Int. J. Glob. Energy Issues 2008;30(1–4):3-27. Varbanov P, Perry S, Klemeš J, Smith R. Synthesis of industrial utility systems: costeffective de-carbonisation. Appl. Therm. Eng. 2005;25(7):985-1001. Yokoyama R, Ito K. Optimal design of gas turbine cogeneration plants in consideration of discreteness of equipment capabilities. J. Eng. Gas Turbine Power 2006;128(2): 336–43.