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The environmental, health, and safety implications of solar energy in central station power production
Orer~v Vol. IX, No. 6, pp. 681485,
03f+5432/‘93
1993
Copyright 0
Printed in Grcat Britain. All rights rcscrved
$h.lM)-+ 0.00
lYY3 Pcrgamon Prca Ltd
THE ENVIRONMENTAL, HEALTH, AND SAFETY IMPLICATIONS OF SOLAR ENERGY IN CENTRAL STATION POWER PRODUCTION? ROGER Management
Information
Services,
Inc.,
H. BEZDEK
116 Fourth
Street.
S.E..
Washington,
DC 20003.
(Received 24 August 1991: received for publication 28 Orlober
1J.S.A
1992)
Abstract-We compare the impact on greenhouse-gas emissions. environmental degradation. and human health and safety of solar energy systems with the nuclear and fossil-energy options. When all direct and indirect aspects of the different energy production and delivery systems are properly accounted for, we find the following: (i) given current technologies, on a standardized energy unit basis, solar energy systems may initially cause more greenhouse-gas emissions and environmental degradation than do conventional nuclear and fossil-energy systems. (ii) An ambitious program to utilize solar energy systems in place of nuclear and fossil-fuel systems could, for the next 4 or 5 decades, actually increase environmental degradation. In addition, the production of materials for these technologies involves hazardous substances that must be handled cautiously to avoid environmental damage. (iii) In comparing solar energy systems with the conventional alternatives, it is important to recognize the substantial costs, hazardous wastes, and land-use issues associated with solar technologies. (iv) Based upon risk perceptions and current technologies, the health and safety risks of solar energy systems may be substantially larger than those associated with some fossil- and nuclear-energy resource options.
INTRODUCTION
The utilization of all forms of solar technologies in the nation’s energy mix is clearly desired and necessary to satisfy future energy needs, but an assessment of alternative energy technologies must include recognition of all of the potential environmental costs associated with the technologies. Solar energy systems may be inherently more or less risky and environmentally dangerous than any of the conventional the entire
alternatives.
fuel and production
This determination
cycles for all energy
systems.
can only be made It should
by evaluating u priori
not be assumed
that the solar alternatives are always more environmentally benign because produce no greenhouse gases or negative environmental externalities..+ This but it is often difficult to articulate because it is, at least at first glance, Environmental analyses of different energy systems should be comprehensive
they (supposedly) is a crucial point, counterintuitive.
positive
all phases
and
negative
externalities
resulting
(directly
and
indirectly)
from
in estimating
the
of the
energy production cycle and consistent in ensuring that all positive and negative externalities (direct and indirect) are included in the assessment of each energy source technology. In recognition of the growing concern with respect to the emission of greenhouse gases, significant
attention
has been
focused
on solar energy
systems
because
of the perception
they produce virtually no such gases and may thus be preferable to the conventional and fossil-energy alternatives. More generally, it is often claimed that solar energy
l-Address
for mailing:
Management
STherc are five greenhouses global warming: be responsible responsible
CO,.
CH,,
for about
Information
Services,
gases which cause the Earth’s NzO. one-half
Inc., 2716,
and two chlorofluorocarbons of the greenhouse
Colt Run Road.
atmosphere effects,
for the other half. 681
VA
22124.
systems
U.S.A.
to retain heat and which may thus contribute
(CFCI, with
Oakton,
that nuclear
and CF,CL). the other
four
Carbon
dioxide
i\ estimated
gases listed above
to to
collectively
682
ROGER H. BEZDEK
cause little air or water pollution, do not contribute to greenhouse-gas emissions, and pose little danger to human health and safety (Ref. 1, pp. 67-101). Given the trend toward integrated resource planning, the validity of such assertions is extremely important and could result in decisions that favor solar energy systems and actively discourage and penalize the use of nuclear and fossil-energy alternatives (The incorporation of externalities into integrated resource planning is discussed in Ref. 2). The purpose of this paper is to summarize information currently available about the validity of such claims.
ENVIRONMENTAL EXTERNALITIES RESULTING CONVENTIONAL, CENTRAL-POWER-STATION
FROM SOLAR ENERGY
ENERGY SYSTEMS
AND
The major solar energy options are solar space heating and cooling, solar water heating, photovoltaics (PV), wind-energy conversion systems (WECS), hydroelectric power generation, biomass, solar thermal electric, and passive solar/conservation. There is a strong inherent supposition in the global warming and environmental externalities literature that these alternative energy-supply options are to be preferred on environmental grounds and are not economically viable only because of the underpricing of external environmental costs, government subsidies to such traditional sources as oil, gas, nuclear, and coal, misguided energy policies, and related factors.3 The reasoning behind the supposition is generally based upon a framework whereby a coal plant is compared to solar heating systems, PV systems, or a solar thermal electric power plant. The coal plant, even with the best scrubber technology and other environmental controls, emits substantial residuals into the air and water and contributes to greenhouse-gas accumulation in the atmosphere, whereas the solar systems produce virtually no pollution or greenhouse gases. Apparently, then, the only question is how much credit the solar systems should be given or to what extent the coal plant should be penalized to account for externalities. However, most of the currently considered solar options have significant environmental costs as part of the up-front production of the solar energy systems. Generally speaking, after installation, most solar energy systems have positive long-run environmental impacts, whereas the short-run and intermediate environmental impacts are strongly negative. The manufacture, transportation, and construction of solar energy systems have, on a per unit of energy basis, relatively large front-end environmental costs, as is the case also with financial expenditures (Ref. 4, pp. 52-58 of Ref. 5, and pp. 124-132 of Ref. 6). In effect, most of the environmental degradation is purchased and occurs immediately when the solar energy systems are produced and installed. These externalities can be viewed as pre-operation effects because they occur before the energy system goes into operation. Generation of these up-front environmental costs is counterbalanced against the environmental savings over the life of the systems. For example, a solar space-heating system has an associated life-cycle pollution balance. In the years of manufacture, construction, and installation, there are. significant environmental wastes produced, including substantial amounts of greenhouse gases, due to the production of the materials used in the system (Ref. 4, pp. 52-58 of Ref. 5, and pp. 124-132 of Ref. 6). The environmental degradation associated with the same capacity of a coal-fired or nuclear electric power plant may be considerably less than that associated with the solar system.4,5%7 In the year of installation, the solar system is a serious net pollution contributor, and a solar water and space heating system for a single family house may produce an additional 20-40 lb of particulates, 50-75 lb of SO*, and substantial quantities of greenhouse gases, as compared with an equivalent coal-fired alternative.? Following system start-up, however, the solar system produces relatively little further environmental degradation and generates environmental tThe precise amounts of the environmental externalities produced will depend the types of materials used in its manufacturing, and related variables.-
on the system size and configuration,
The environmental,
health, and safety implications of solar energy
683
savings (or negative residuals) by precluding the use of some coal every year. In the U.S., the net savings will pay back the net environmental degradation effects in about 8-15 yr and result in net environmental savings thereafter; the wide range in the estimates is caused by variability in the types of system, location, energy efficiency, etc. Similar reasoning applies to photovoltaics and solar thermal electric systems. However, for these energy-resource options, the environmental payback will usually be lo-25 yr. The reason for the longer payback is that these technologies are relatively less energy efficient than dispersed solar energy systems, and they also suffer from disadvantages (transmission, etc.) of all central power station technologies. While the payback figures will differ among systems, applications, and regions of the country, the salient point is that environmentally benign solar energy systems generate in the years in which the components for the systems are produced and installed and for many years thereafter, substantial negative impacts on the environment and on greenhouse-gas emissions. This little-noted fact must be recognized and handled correctly in the assessment of the environmental externalities resulting from different types of energy systems, especially since it is so often neither recognized nor accounted for in comparing the environmental impacts of different energy resource options. More important, this example allows us to hypothesize what could happen if the nation moves aggressively toward widespread utilization of solar energy systems to displace and substitute for conventional central-power-station technologies. At the increasing levels of solar utilization required, a huge volume of solar energy systems is required to displace a 500 MWe power plant, and many more solar systems will have to be built in relatively short periods of time.? This process will exacerbate the front-end greenhouse-gas emissions and other wastes emitted during the production of the solar energy systems. It is obvious that the more widespread and the more rapidly the solar technologies are introduced to displace conventional alternatives, the worse this near-term environmental degradation will become. At some point in time, the solar systems will become generators of net environmental benefits, but for ambitious and meaningful solar energy programs, this will be many years in the future. 2y7Thus , if the U.S. were to embark on an ambitious program in the mid-1990s to satisfy a substantial portion of its energy requirements by using solar energy systems, greenhouse gas emissions could increase for several decades and the net pollution balance could remain negative for 3 or 4 decades because of the huge number of solar energy systems that would have to be produced and installed over the next 30 or 40 yr.3: The amount of materials and costs of the solar equipment required to compete with a 500 MW conventional plant are enormous.§ In addition, it must be recognized that solar systems do not function at night, during the rain or snow, on cloudy days, etc., so that storage and backup systems are required and capacity from a traditional power plant may be needed as ultimate backup to provide adequate system reliability. These factors must be taken into account in the comparison of environmental externalities between solar energy and the conventional electric generation alternatives. When the capital, manufacturing, processing, tAt increasing levels of solar energy utilization, more solar systems will be built in a relatively short period of time, thus exacerbating the front-end pollution damages. Since the number of systems built will have to increase cont~nuousiy and dramatically for 2 or 3 decades, solar energy may possibly remain a net pollution contributor for several decades, until the rate of market growth begins to stabilize.‘.’ *The sheer magnitude of the effort involved in utilizing solar energy to provide a substantial portion of the nation’s energy requirements is not generally appreciated. Utilization of solar energy to provide only IO-15% of U.S. energy consumption may require deployment within 25 yr of the following: 26 million solar water heaters, 7 million solar water and space heating systems, 1 million solar heating and cooling systems, 5 million solar passive heating systems, 6 miltion small-scale wind systems, 500 large-scale, central power wind systems, 1300 large-scale solar thermal electric central power plants, and 6 million photovoltaic power systems (Ref. 4, p. 353). With the exception of solar water heaters, the numbers of any types of solar energy systems currently in existence are negligible. §For example, with a capacity factor of between 0.40 and 0.20, construction of a 500 MW solar thermal electric power plant could require 500 thousand tons of steel, 1.5 million tons of concrete, 50 thousand tons of glass, and 35 thousand tons of aluminum.
ROGER H. BEZDEK
484
transportation, and maintenance costs of solar systems are correctly accounted for-including the on-site backup and the capacity required from “traditional” supply, the environmental (and all other) costs of solar energy systems may be much higher than is commonly assumed. Another factor beyond the environmental analysis associated with the production of solar energy systems is the use of land required for these systems. A 500 MWe photovoltaic or solar thermal electric power plant will require 5000 to 10,000 acres, depending on system ~nfiguration, location, and related factors, but not including transmission lines, backup facilities, etc. (Ref. 8, p. 2.53). The pursuit of ambitious solar energy goals may require that one of every two new residential and commercial buildings utilize some type of solar energy system.* Solar energy systems, especially passive systems, imply the use of space, which is increasingly at a premium. There are unique problems directly associated with the production of some solar energy systems. For example, the production of photovoltaic cells requires the use of hazardous substances and gases. These include silane, which explodes on contact with air, and arsine, phosphine, diborane, and other toxic gases used in the manufacture of advanced cell types (Ref. 8, pp. 2.52-2.53). Mass production of photovoltaic cells on the scale necessary to substitute for nuclear and fossil-energy technologies will result in the production of enormous quantities of these hazardous substances and will require careful handling and disposal of unwanted byproducts.
HEALTH
AND
SAFETY RISKS OF CONVENTIONAL
SOLAR ENERGY ALTERNATIVES
COMPARED
WITH
All forms of energy production involve risk to human health and safety, and an indirect result of the development of coal and commercial nuclear power over the past 5 decades is increased risks to the health and safety of the nation’s population. An important question is how these risks compare with those which would have resulted from the production of equivalent power from other energy sources such as solar energy (Ref. 12, pp. 28-32). The usual comparison made is that of a nuclear power plant with a coal-fired plant of equal generating capacity, since coal is the other major base-load option in the U.S. More generally, however, all energy sources are substitutes. Natural gas, oil, hydroelectricity, and solar energy technologies as well as coal can be used as substitutes to produce electricity and space heating and cooling. In comparing the risks inherent in different energy sources, controve~y surrounds the question of what activities to include: accidents, routine operation, the fuel cycle, construction of the plant, and manufacturing the materials from which it is to be built. However, a valid comparison of the relative risks of different energy sources must use a standard per unit comparison (equivalent number of b.t.u.s or kilowatt hours of electricity produced) and must include the total production cycle of the energy source: mining, production, transportation, installation, operation, maintenance, and disposal of unwanted byproducts. Over the past 2 decades many researchers have estimated the relative risks of different energy sources, and illustrative, representative resuhs of their work are given in Table 1. ‘M* One salient feature of the data in this table is the wide range of uncertainty about the effects of power production by the different energy sources. This is not surprising for wind and solar power, since there is not yet enough experience on which to base firm estimates. It is noteworthy, however, that the hazards of these sources of energy are far from negligible. People do fall off of roofs while installing or maintaining solar energy systems and some people will be injured or killed by flying fragments of broken windmill blades. However, the major portion of the health and safety risks associated with these so called clean sources is the huge (relative to energy output) materials requirements of these technologies and the concomitant risks involved in the necessary mining, manufacturing, transportation, and related activities. Once again it is the front-end costs that are paramount (pp. 9-30 of Ref. 10, and Ref. 11). The most notable characteristic of this table is that it shows that energy sources can be
The environmental, Table
health,
and safety
implications
685
of solar energy
1. Total man-days lost and deaths per 1000 MWe-yr of operation for different energy systems.“‘.” Energy
source
Coal Oil Nuclear Natural gas Hydroelectricity Wind Methanol Solar space heating Solar thermal electric Photovoltaics Ocean thermal energy
conversion
Days lost
Deaths
80010(Kl 250-825 x-15 7-x 60-70 30-90 175-200 160180 50-90 75- 125 20-50
20-90 9-20 l-2 1 , 7-o 15-20 7-10 x-9 h-9 J-4
ranked on the basis of risk per unit of output. Natural gas is the cleanest and safest energy source, despite the fatalities resulting from gas explosions and from hazardous drilling operations. Nuclear power is seen to be the second least risky energy source after natural gas, while coal and methanol Objective
analysis
present
the greatest
of the data in Table
for natural gas, the most solar energy technologies
health
and safety
1 indicates
that commercial
risk-free energy source. The advantage is striking in that orders of magnitude
nuclear power is 4-8 times less risky than wind photovoltaics, 6-10 times less risky than solar thermal solar space
heating.
Thus,
risks.
the direct
measured in terms of accidents energy technologies frequently
and indirect
energy, electric,
health
power
is, except
10-15 times less risky than and 5-20 times less risky than
and safety
and fatalities may be substantially advocated as substitutes.
nuclear
of nuclear power over the are involved. Commercial
risks of nuclear
power
as
lower than those of the solar
Acknowledgemen&-The author is indebted to M. Fertel, C. Goldstein, B. Fleming. E. Nunnelee, and an anonymous referee for comments on earlier drafts of this manuscript, but retains sole responsibility for the opinions expressed here and for any errors. This work was supported, in part, by the U.S. Council for Energy Awareness.
REFERENCES
K. Bossong, A. Antypas, and S. Denman. “Turning Down the Heat: Solutions to Global 1. N. Rader, Warming,” Public Citizen Critical Mass Energy Project, 215 Pennsylvania Avenue. SE, Washington, DC 20003 (1988). 2. D. Moskovitz, “Profits and Progress Through Least Cost Planning, National Association of Room 1102 ICC Bldg., Washington, DC 20044 (1989). Regulatory Utility Commissioners,” 3. R. Ottinger, Environmental Costs of Electricity, Oceana, New York, NY (1990). R. Chew, and R. Wendling, Nat. Resour. J. 22, 337 (1982). 4. R. Bezdek, G. Bennington, 5 0. Hohmeyer, Social Costs of Energy Consumption, Springer, Berlin (1988). _ Costs of Electricity Generation,” OECD, Paris (1985). 6. “Environmental International Journal 7, 301 (1982). 7. R. Bezdek and N. Kannon, Energy-The Inc., Management Information Services, Inc., and Brookhaven National Laboratories, 8. Enviroplan, “Proposal to Develop a Methodology for Estimating Environmental Externality Costs for Supply and NJ 07068 Demand Side Electric Resources in New York State,” 3 Becker Farm Road, Roseland, (1991).
9. Management
Inc. and Management Analysis Corporation, “Right on the Information Services, Money: Costs, Benefits, and Results of Federal Support for Nuclear Energy,” 116 Fourth Street SE. Washington, DC 20003 (1991). 10. H. Inhaber, Energy Risk Assessment, Gordon & Breach, New York, NY (1982). Il. H. Inhaber, in Nuclear Power: Policy and Prospects, pp. 117-130, P. M. S. Jones ed., Wiley, New York, NY (1987). 12. P. Ricci and L. Molton, in Annual Review of Energy, pp. 77-95, J. Hollander ed., Annual Reviews. Inc., Palo Alto, CA (1986).
03f+5432/‘93
1993
Copyright 0
Printed in Grcat Britain. All rights rcscrved
$h.lM)-+ 0.00
lYY3 Pcrgamon Prca Ltd
THE ENVIRONMENTAL, HEALTH, AND SAFETY IMPLICATIONS OF SOLAR ENERGY IN CENTRAL STATION POWER PRODUCTION? ROGER Management
Information
Services,
Inc.,
H. BEZDEK
116 Fourth
Street.
S.E..
Washington,
DC 20003.
(Received 24 August 1991: received for publication 28 Orlober
1J.S.A
1992)
Abstract-We compare the impact on greenhouse-gas emissions. environmental degradation. and human health and safety of solar energy systems with the nuclear and fossil-energy options. When all direct and indirect aspects of the different energy production and delivery systems are properly accounted for, we find the following: (i) given current technologies, on a standardized energy unit basis, solar energy systems may initially cause more greenhouse-gas emissions and environmental degradation than do conventional nuclear and fossil-energy systems. (ii) An ambitious program to utilize solar energy systems in place of nuclear and fossil-fuel systems could, for the next 4 or 5 decades, actually increase environmental degradation. In addition, the production of materials for these technologies involves hazardous substances that must be handled cautiously to avoid environmental damage. (iii) In comparing solar energy systems with the conventional alternatives, it is important to recognize the substantial costs, hazardous wastes, and land-use issues associated with solar technologies. (iv) Based upon risk perceptions and current technologies, the health and safety risks of solar energy systems may be substantially larger than those associated with some fossil- and nuclear-energy resource options.
INTRODUCTION
The utilization of all forms of solar technologies in the nation’s energy mix is clearly desired and necessary to satisfy future energy needs, but an assessment of alternative energy technologies must include recognition of all of the potential environmental costs associated with the technologies. Solar energy systems may be inherently more or less risky and environmentally dangerous than any of the conventional the entire
alternatives.
fuel and production
This determination
cycles for all energy
systems.
can only be made It should
by evaluating u priori
not be assumed
that the solar alternatives are always more environmentally benign because produce no greenhouse gases or negative environmental externalities..+ This but it is often difficult to articulate because it is, at least at first glance, Environmental analyses of different energy systems should be comprehensive
they (supposedly) is a crucial point, counterintuitive.
positive
all phases
and
negative
externalities
resulting
(directly
and
indirectly)
from
in estimating
the
of the
energy production cycle and consistent in ensuring that all positive and negative externalities (direct and indirect) are included in the assessment of each energy source technology. In recognition of the growing concern with respect to the emission of greenhouse gases, significant
attention
has been
focused
on solar energy
systems
because
of the perception
they produce virtually no such gases and may thus be preferable to the conventional and fossil-energy alternatives. More generally, it is often claimed that solar energy
l-Address
for mailing:
Management
STherc are five greenhouses global warming: be responsible responsible
CO,.
CH,,
for about
Information
Services,
gases which cause the Earth’s NzO. one-half
Inc., 2716,
and two chlorofluorocarbons of the greenhouse
Colt Run Road.
atmosphere effects,
for the other half. 681
VA
22124.
systems
U.S.A.
to retain heat and which may thus contribute
(CFCI, with
Oakton,
that nuclear
and CF,CL). the other
four
Carbon
dioxide
i\ estimated
gases listed above
to to
collectively
682
ROGER H. BEZDEK
cause little air or water pollution, do not contribute to greenhouse-gas emissions, and pose little danger to human health and safety (Ref. 1, pp. 67-101). Given the trend toward integrated resource planning, the validity of such assertions is extremely important and could result in decisions that favor solar energy systems and actively discourage and penalize the use of nuclear and fossil-energy alternatives (The incorporation of externalities into integrated resource planning is discussed in Ref. 2). The purpose of this paper is to summarize information currently available about the validity of such claims.
ENVIRONMENTAL EXTERNALITIES RESULTING CONVENTIONAL, CENTRAL-POWER-STATION
FROM SOLAR ENERGY
ENERGY SYSTEMS
AND
The major solar energy options are solar space heating and cooling, solar water heating, photovoltaics (PV), wind-energy conversion systems (WECS), hydroelectric power generation, biomass, solar thermal electric, and passive solar/conservation. There is a strong inherent supposition in the global warming and environmental externalities literature that these alternative energy-supply options are to be preferred on environmental grounds and are not economically viable only because of the underpricing of external environmental costs, government subsidies to such traditional sources as oil, gas, nuclear, and coal, misguided energy policies, and related factors.3 The reasoning behind the supposition is generally based upon a framework whereby a coal plant is compared to solar heating systems, PV systems, or a solar thermal electric power plant. The coal plant, even with the best scrubber technology and other environmental controls, emits substantial residuals into the air and water and contributes to greenhouse-gas accumulation in the atmosphere, whereas the solar systems produce virtually no pollution or greenhouse gases. Apparently, then, the only question is how much credit the solar systems should be given or to what extent the coal plant should be penalized to account for externalities. However, most of the currently considered solar options have significant environmental costs as part of the up-front production of the solar energy systems. Generally speaking, after installation, most solar energy systems have positive long-run environmental impacts, whereas the short-run and intermediate environmental impacts are strongly negative. The manufacture, transportation, and construction of solar energy systems have, on a per unit of energy basis, relatively large front-end environmental costs, as is the case also with financial expenditures (Ref. 4, pp. 52-58 of Ref. 5, and pp. 124-132 of Ref. 6). In effect, most of the environmental degradation is purchased and occurs immediately when the solar energy systems are produced and installed. These externalities can be viewed as pre-operation effects because they occur before the energy system goes into operation. Generation of these up-front environmental costs is counterbalanced against the environmental savings over the life of the systems. For example, a solar space-heating system has an associated life-cycle pollution balance. In the years of manufacture, construction, and installation, there are. significant environmental wastes produced, including substantial amounts of greenhouse gases, due to the production of the materials used in the system (Ref. 4, pp. 52-58 of Ref. 5, and pp. 124-132 of Ref. 6). The environmental degradation associated with the same capacity of a coal-fired or nuclear electric power plant may be considerably less than that associated with the solar system.4,5%7 In the year of installation, the solar system is a serious net pollution contributor, and a solar water and space heating system for a single family house may produce an additional 20-40 lb of particulates, 50-75 lb of SO*, and substantial quantities of greenhouse gases, as compared with an equivalent coal-fired alternative.? Following system start-up, however, the solar system produces relatively little further environmental degradation and generates environmental tThe precise amounts of the environmental externalities produced will depend the types of materials used in its manufacturing, and related variables.-
on the system size and configuration,
The environmental,
health, and safety implications of solar energy
683
savings (or negative residuals) by precluding the use of some coal every year. In the U.S., the net savings will pay back the net environmental degradation effects in about 8-15 yr and result in net environmental savings thereafter; the wide range in the estimates is caused by variability in the types of system, location, energy efficiency, etc. Similar reasoning applies to photovoltaics and solar thermal electric systems. However, for these energy-resource options, the environmental payback will usually be lo-25 yr. The reason for the longer payback is that these technologies are relatively less energy efficient than dispersed solar energy systems, and they also suffer from disadvantages (transmission, etc.) of all central power station technologies. While the payback figures will differ among systems, applications, and regions of the country, the salient point is that environmentally benign solar energy systems generate in the years in which the components for the systems are produced and installed and for many years thereafter, substantial negative impacts on the environment and on greenhouse-gas emissions. This little-noted fact must be recognized and handled correctly in the assessment of the environmental externalities resulting from different types of energy systems, especially since it is so often neither recognized nor accounted for in comparing the environmental impacts of different energy resource options. More important, this example allows us to hypothesize what could happen if the nation moves aggressively toward widespread utilization of solar energy systems to displace and substitute for conventional central-power-station technologies. At the increasing levels of solar utilization required, a huge volume of solar energy systems is required to displace a 500 MWe power plant, and many more solar systems will have to be built in relatively short periods of time.? This process will exacerbate the front-end greenhouse-gas emissions and other wastes emitted during the production of the solar energy systems. It is obvious that the more widespread and the more rapidly the solar technologies are introduced to displace conventional alternatives, the worse this near-term environmental degradation will become. At some point in time, the solar systems will become generators of net environmental benefits, but for ambitious and meaningful solar energy programs, this will be many years in the future. 2y7Thus , if the U.S. were to embark on an ambitious program in the mid-1990s to satisfy a substantial portion of its energy requirements by using solar energy systems, greenhouse gas emissions could increase for several decades and the net pollution balance could remain negative for 3 or 4 decades because of the huge number of solar energy systems that would have to be produced and installed over the next 30 or 40 yr.3: The amount of materials and costs of the solar equipment required to compete with a 500 MW conventional plant are enormous.§ In addition, it must be recognized that solar systems do not function at night, during the rain or snow, on cloudy days, etc., so that storage and backup systems are required and capacity from a traditional power plant may be needed as ultimate backup to provide adequate system reliability. These factors must be taken into account in the comparison of environmental externalities between solar energy and the conventional electric generation alternatives. When the capital, manufacturing, processing, tAt increasing levels of solar energy utilization, more solar systems will be built in a relatively short period of time, thus exacerbating the front-end pollution damages. Since the number of systems built will have to increase cont~nuousiy and dramatically for 2 or 3 decades, solar energy may possibly remain a net pollution contributor for several decades, until the rate of market growth begins to stabilize.‘.’ *The sheer magnitude of the effort involved in utilizing solar energy to provide a substantial portion of the nation’s energy requirements is not generally appreciated. Utilization of solar energy to provide only IO-15% of U.S. energy consumption may require deployment within 25 yr of the following: 26 million solar water heaters, 7 million solar water and space heating systems, 1 million solar heating and cooling systems, 5 million solar passive heating systems, 6 miltion small-scale wind systems, 500 large-scale, central power wind systems, 1300 large-scale solar thermal electric central power plants, and 6 million photovoltaic power systems (Ref. 4, p. 353). With the exception of solar water heaters, the numbers of any types of solar energy systems currently in existence are negligible. §For example, with a capacity factor of between 0.40 and 0.20, construction of a 500 MW solar thermal electric power plant could require 500 thousand tons of steel, 1.5 million tons of concrete, 50 thousand tons of glass, and 35 thousand tons of aluminum.
ROGER H. BEZDEK
484
transportation, and maintenance costs of solar systems are correctly accounted for-including the on-site backup and the capacity required from “traditional” supply, the environmental (and all other) costs of solar energy systems may be much higher than is commonly assumed. Another factor beyond the environmental analysis associated with the production of solar energy systems is the use of land required for these systems. A 500 MWe photovoltaic or solar thermal electric power plant will require 5000 to 10,000 acres, depending on system ~nfiguration, location, and related factors, but not including transmission lines, backup facilities, etc. (Ref. 8, p. 2.53). The pursuit of ambitious solar energy goals may require that one of every two new residential and commercial buildings utilize some type of solar energy system.* Solar energy systems, especially passive systems, imply the use of space, which is increasingly at a premium. There are unique problems directly associated with the production of some solar energy systems. For example, the production of photovoltaic cells requires the use of hazardous substances and gases. These include silane, which explodes on contact with air, and arsine, phosphine, diborane, and other toxic gases used in the manufacture of advanced cell types (Ref. 8, pp. 2.52-2.53). Mass production of photovoltaic cells on the scale necessary to substitute for nuclear and fossil-energy technologies will result in the production of enormous quantities of these hazardous substances and will require careful handling and disposal of unwanted byproducts.
HEALTH
AND
SAFETY RISKS OF CONVENTIONAL
SOLAR ENERGY ALTERNATIVES
COMPARED
WITH
All forms of energy production involve risk to human health and safety, and an indirect result of the development of coal and commercial nuclear power over the past 5 decades is increased risks to the health and safety of the nation’s population. An important question is how these risks compare with those which would have resulted from the production of equivalent power from other energy sources such as solar energy (Ref. 12, pp. 28-32). The usual comparison made is that of a nuclear power plant with a coal-fired plant of equal generating capacity, since coal is the other major base-load option in the U.S. More generally, however, all energy sources are substitutes. Natural gas, oil, hydroelectricity, and solar energy technologies as well as coal can be used as substitutes to produce electricity and space heating and cooling. In comparing the risks inherent in different energy sources, controve~y surrounds the question of what activities to include: accidents, routine operation, the fuel cycle, construction of the plant, and manufacturing the materials from which it is to be built. However, a valid comparison of the relative risks of different energy sources must use a standard per unit comparison (equivalent number of b.t.u.s or kilowatt hours of electricity produced) and must include the total production cycle of the energy source: mining, production, transportation, installation, operation, maintenance, and disposal of unwanted byproducts. Over the past 2 decades many researchers have estimated the relative risks of different energy sources, and illustrative, representative resuhs of their work are given in Table 1. ‘M* One salient feature of the data in this table is the wide range of uncertainty about the effects of power production by the different energy sources. This is not surprising for wind and solar power, since there is not yet enough experience on which to base firm estimates. It is noteworthy, however, that the hazards of these sources of energy are far from negligible. People do fall off of roofs while installing or maintaining solar energy systems and some people will be injured or killed by flying fragments of broken windmill blades. However, the major portion of the health and safety risks associated with these so called clean sources is the huge (relative to energy output) materials requirements of these technologies and the concomitant risks involved in the necessary mining, manufacturing, transportation, and related activities. Once again it is the front-end costs that are paramount (pp. 9-30 of Ref. 10, and Ref. 11). The most notable characteristic of this table is that it shows that energy sources can be
The environmental, Table
health,
and safety
implications
685
of solar energy
1. Total man-days lost and deaths per 1000 MWe-yr of operation for different energy systems.“‘.” Energy
source
Coal Oil Nuclear Natural gas Hydroelectricity Wind Methanol Solar space heating Solar thermal electric Photovoltaics Ocean thermal energy
conversion
Days lost
Deaths
80010(Kl 250-825 x-15 7-x 60-70 30-90 175-200 160180 50-90 75- 125 20-50
20-90 9-20 l-2 1 , 7-o 15-20 7-10 x-9 h-9 J-4
ranked on the basis of risk per unit of output. Natural gas is the cleanest and safest energy source, despite the fatalities resulting from gas explosions and from hazardous drilling operations. Nuclear power is seen to be the second least risky energy source after natural gas, while coal and methanol Objective
analysis
present
the greatest
of the data in Table
for natural gas, the most solar energy technologies
health
and safety
1 indicates
that commercial
risk-free energy source. The advantage is striking in that orders of magnitude
nuclear power is 4-8 times less risky than wind photovoltaics, 6-10 times less risky than solar thermal solar space
heating.
Thus,
risks.
the direct
measured in terms of accidents energy technologies frequently
and indirect
energy, electric,
health
power
is, except
10-15 times less risky than and 5-20 times less risky than
and safety
and fatalities may be substantially advocated as substitutes.
nuclear
of nuclear power over the are involved. Commercial
risks of nuclear
power
as
lower than those of the solar
Acknowledgemen&-The author is indebted to M. Fertel, C. Goldstein, B. Fleming. E. Nunnelee, and an anonymous referee for comments on earlier drafts of this manuscript, but retains sole responsibility for the opinions expressed here and for any errors. This work was supported, in part, by the U.S. Council for Energy Awareness.
REFERENCES
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9. Management
Inc. and Management Analysis Corporation, “Right on the Information Services, Money: Costs, Benefits, and Results of Federal Support for Nuclear Energy,” 116 Fourth Street SE. Washington, DC 20003 (1991). 10. H. Inhaber, Energy Risk Assessment, Gordon & Breach, New York, NY (1982). Il. H. Inhaber, in Nuclear Power: Policy and Prospects, pp. 117-130, P. M. S. Jones ed., Wiley, New York, NY (1987). 12. P. Ricci and L. Molton, in Annual Review of Energy, pp. 77-95, J. Hollander ed., Annual Reviews. Inc., Palo Alto, CA (1986).