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Solar energy is inexhaustible and has generally benign environmental impacts.1
Solar energy has widespread public acceptance and relatively uniform geographic distribution.2
Certain solar technologies are suitable for use in small units and many are considered potentially less complex and hazardous than other energy supply technologies now in use.3
In the long term, solar energy should be able to provide each of the energy forms used by people: heat, electricity, and fuels.4
Because the risks from solar energy appear to be generally less than those of other energy sources and public confidence in solar energy is strong, employing solar energy technologies will not create political controversy.5
The thermal burden of the earth is not increased by the use of solar collectors.6
Solar collectors could eliminate the need for energy transportation and distribution networks, thereby reducing waste. Up to 70 percent of the cost of providing electricity in the U.S. is in its distribution.7
Solar collectors have a high energy yield.8
Large solar farms in the desert regions could increase land productivity by shading areas that could then be used for range land.9
Many solar power systems don't required sophisticated, complex organizations for installation and operation.10
Small-scale solar energy devices can be mass produced with great savings to the consumer.11
The direct applications of solar thermal energy are generally more costly than conventional alternatives.12
There are high initial costs to build and install solar collectors.13
In order for the potential of solar energy to be used most effectively, large areas of land for solar collectors are required.14
Because solar collectors must be very large, they use high volumes of nonrenewable materials in their construction, resulting in high energy costs.15
Solar energy is unreliable because sunshine can be intermittent.16
Solar energy is diffuse and of low quality.17
Solar energy is not storable in its primary form.18
Solar collectors have low efficiency (5-15 percent) in extracting energy from the sun.19
The effects of weather are often unpredictable.20
Widespread use of rooftop flat-plate collectors would require large amounts of steel, copper, and glass compared to centralized power plants.21
Leaks of collector fluids used in solar space and water heating can damage buildings and contaminate buildings' water supply. Toxic substances used in the manufacture of photovoltaic cells are occupational hazards, can contaminate water in manufacturing areas, and can be released from overheated or burning cells.22
While there is no question that the total amount of energy reaching the earth from the sun far exceeds the amount people could ever use, the diffuse nature of solar energy makes it expensive to capture.23
An extensive array of solar power technologies have been established, and they can be divided into three broad categories: space and water heating (passive and active), solar-thermal power generation, and photovoltaics. Solar-thermal and photovoltaic systems are used to generate electricity.24
Solar thermal technology converts solar energy through high concentration and heat absorption into electricity or process heat. Applied solar thermal technologies cover a broad range of sizes and temperatures, and offer the advantage of storable energy, extending useful operation into non-daylight hours. Hybrid systems, which use fossil fuel combustion as a backup, can increase reliability and provide constant power output.25
Solar thermal systems are now generating more than 100 MWe (e=electricity) in the U.S., with projected increases to 550 MWe over the next five years, based on industry plans.26
Component costs for solar thermal systems have decreased, and steady advances in research have made these systems increasingly efficient.27 However, the cost of solar-thermal-generated electricity must be reduced significantly to be competitive.28
It appears possible that systems for converting concentrated sunlight to electricity could become competitive with oil- or gas-fired plants in favorable locations, with continued research and development advances. Demonstration units could be on line by the end of this decade, and 500 MW could be installed by the year 2000.29
Photovoltaic cells directly convert solar energy into electricity. Most commercial cells are made from silicon, one of the most abundant elements on earth. They come in various sizes and shapes, and are connected in series, parallel, or both, to form modules to produce higher voltages. Even greater power is possible when modules are interconnected to form arrays. These arrays, together with other components, form a photovoltaic power system.30
Despite a growing worldwide photvoltaic market,31 large-scale commercial photovoltaic electricity generation is currently unfeasible. Technological innovations are needed to reduce costs, improve efficiency, and provide storage systems for backup power when sunlight is not available.32 At present, the largest operating photovoltaic system is 5 MW.33
1 National Academy of Sciences, U.S. Energy Supply Prospects to 2010, (Washington, D.C.: National Academy of Sciences, 1979), p. 19.
4 Energy in Transition, op. cit., pp. 39-40.
5 Ibid., p. 39.
6 Gabel, op. cit., p. 143.
9 Ibid., pp. 143-146.
10 Ibid., p. 144.
12 Energy in Transition, op. cit., p. 39.
13 Deudney and Flavin, op. cit., p. 60
14 Energy in Transition, op. cit., p. 39.
15 National Academy of Sciences, U.S. Energy Supply Prospects to 2010, op. cit., p. 19.
16 Gabel, op. cit., p. 144.
22 Holdren, op. cit., p. 141.
23 Peirce, op. cit., p. 248.
24 Edison Electric Institute, "Alternative Energy Sources and Technologies," op. cit., pp. 16-18.
25 Energy Security, op. cit., p. 203.
26 Ibid., p. 204.
27 Ibid., p. 202.
28 Ibid., p. 204.
29 F.L. Culler and E.L. Zebroski, "Electricity Supply Outlook and R&D Options for the U.S.," in Guidelines for DEO Long-Term Civilian R&D, Vol. VI, Appendix F, December 1985, p. 14.
30 Energy ALternatives, Special Committee on Alternative Energy and Oil Substitution, (Canada: Minister of Supply and Services, 1981), p. 217.
31 Energy Security, op. cit., p. 204.
32 Edison Electric Institute, "Alternative Energy Sources and Technologies," op. cit., p. 17.
33 Energy Security, op. cit.