Issue Brief CONGRESSIONAL RESEARCH SERVICE LIBRARY OF CONGRESS
SOLAR BNHAGY FkOM SPACE: SATELLITE POWER STATIONS ISSUE BRIEF NUMBER IB7dO12 AOTHOS: Salih, Barcia S. Science Policy Research Division THE LIBRAEI OF COEGRESS CONGRESSIONAL RESEARCH SERVICE MAJOR ISSUES SISTER DATE ORIGINATED 02/14/78 DATE UPDATED 09/12/79 FOR ADDITIONAL INFORMATION CALL 287-BSO^ ^03 \ 0912
From the Space Studies Institute Research Library = ssi.org
IB7»012 UPDATE—09/12/79 ISSUE DEFINITION In the quest for new, inexhaustible sources of energy, solar energy has become a promising contender, because the Sun's energy is not expected to be depleted for six billion years. Several factors prevent solar energy from falling freeiy onto the Earth's surface, however, leading to the concept of building electric power plants which utilize solar energy in Earth orbit. Electricity generated by these stations would be beamed down in the form of microwaves to receiving antennas located on the planet's surface. This concept is referred to as satellite power stations (SPS). Through the authorization and appropriation process, Congress has demonstrated a consistent interest in pursuing feasibility studies of an SPS program. The Executive branch has appeared less enthusiastic about the concept, and a 1976 Office of Management and Budget decision transferred responsibility for the program to the Energy Research and Development Administration (now part of the Department of Energy) from the national Aeronautics and Space Administration, which had previously performed the feasibility studies. This transfer of responsibility was viewed in some quarters as a downgrading of the program, especially when ERDA did not request any funding for SPS in its FI77 budget. In the 95th and 96th Congresses, specific legislation has been introduced to increase funding for determining the technical, economic, and environmental feasibility of the concept. BACKGROUND AMD POLICY ANALYSIS Solar energy is receiving increasing attention as an electrical power source, either through direct conversion of sunlight into electricity (photovoltaics) or by using the energy to heat working fluids which operate conventional turbines (solar thermal). Solar energy, however, is prevented from failing freely onto the Earth's surface by inclement weather, the diurnal cycle, and the screening effects of the atmosphere (on a clear day, the amount of sunlight reaching the ground is about 65* of that above the atmosphere). Solar energy systems on the surface of the planet would therefore require storage systems for those times when solar energy is not available, making then less attractive as a base load power source. Alternatively, these power plants could be placed in orbit around the Earth where sunlight is both continuously available and more intense. Called satellite power stations (SPS), they would be placed in geosynchronous orbit where an object maintains the same position relative to a given point on the globe. Although the SPS would be eclipsed by the Earth's shadow for varying periods of time each day, the eclipse time would never exceed 72 minutes, meaning the system could theoretically operate for 99% of the year, an attractive feature for a base load power source. Because of the need for periodic maintenance, however, plant factors of 80% - 92% have been estimated. Tne electricity would be produced at the orbital station and converted into microwaves, then beamed down to receiving and rectifying antennas (called rectennas) on the planet's surface where the microwaves would be reconverted into electricty. At the present time, the SPS concept is still in the feasibility determination stage, making judgments about it difficult to render. NASA and
DOE are now nearing the end of a 3—year study of the various SPS designs described neiow. Once the results ot those studies are available (scheduled for early 1980), a decision can be made as to whether to proceed with a prototype SPS or to shelve the concept temporarily or permanently. In January 1979, DOE and NASA published a reference design tor SPS, selecting a photovoltaic system constructed in geosynchronous Earth orbit, generating 5,000 megawatts of power. In doing so, the agencies set aside designs for a solar thermal nature. For completeness, this issue brief describes both concepts. Before discussing the two most common SPS concepts, photovoltaic and solar thermal, it shoul be noted that two other designs are sometimes included under the rubric of SPS. The first suggests placing nuclear power plants in orbit, primarily to ease siting restrictions and environmental concerns. This system would not benefit from the greater availability or intensity of sunlight in orbit. Also, concerns about nuclear reactor—bearing satellites were heightened when a Russian satellite (Kosmos 954) accidentally deorbited and landed in northwestern Canada in January 1978. The other guasi-SPS design is a Power Relay Satellite (PRS), proposed by Krafft Ericke (of Space Global, Inc.). As its name implies, this satellite would relay power generated by solar power plants, not produce the power itself, and therefore does not qualify in the SPS category - According to the Ehricre plan, solar power plants on the surface of the planet would generate electricity which would be converted into microwaves, then beamed up to the PRS and back down to an area requiring the power and reconverted into electricity. PRS is designed to accommodate the requirement that solar power stations be located in sunny regions (sucn as Arizona), while the power they produce may be needed in less sunny places like Syracuse, New Xorx. SPS TECHNOLOGY The photovoltaic concept, or SSPS for Satellite Solar Power Station, was first proposed Dy Peter Glaser of Arthur D. Little, Inc., in 1988. His plan calls tor constructing arrays of solar ceils in space for the direct conversion ot sunlight into electricity. a 5,000 megawatt SSPS (measured at the rectenna) would consist of two arrays, each approximately 5 by 6 Kilometers, separated by the microwave transmitter, and would generate 9,300 megawatts of power at the orbital station. An SSPS could also be designed to produce 10,000 megawatts at the rectenna. A reaction control system would be required to maintain the satellite in its desired orbit and to keep the solar arrays pointed continuously toward the Sun. Mirrors could be used to concentrate the solar energy onto the arrays. The soiar cells could De made of either silicon or gallium arsenide (or other substances which may develop from future research). Silicon solar cells are the type in common usage today, and it is considered possible that these cells could attain an efficiency rating of 18% (converts 18% of light received into electricity) by the time an SSPS would be in use (compared with the 11—15% efficiency factor now achievable). Gallium arsenide cells are expected to have a higher efficiency, perhaps as high as 27%. They are also less susceptible to damage from space radiation and can provide higher efficiencies at higher temperatures, allowing concentration ratios (use of mirrors to intensify sunlight) up to 5 (silicon cells can operate efficiently with a concentration ratio of only about 2.) Until recently, gallium arsenide was also considered superior to silicon because it could operate with full performance at a thickness of 5 microns, while silicon began losing its efficiency at a thickness less than 100 microns. New research, however,
has shown that, although the efficiency of silicon cells does decrease somewhat as the cell becomes thinner than 100 microns, the efficiency increases again as the cell becomes even thinner. It is now expected that a silicon cell 5 microns in thickness would have comparable efficiency to the gallium arsenide cells. End—to—end efficiency of an SSPS system is expected to be about 7.06* for a silicon ceil design, and 6.97* for a system using gallium arsenide, assuming a cell efficiency of 16.5* for silicon and 18.2* for gallium arsenide. The major factors in favor of silicon cells are familiarity in working with them and a possible supply problem with gallium. In the DOE/NASA reference design, no choice was made between the two solar cell options. Solar thermal systems involve focusing solar energy with mirrors into a cavity containing a heat absorber (helium, potassium vapor, or liquid cesium) which becomes heated and drives a turbine which produces electricity. The solar thermal concepts most often discussed are the closed Brayton cycle and the Rankine cycle. (A third concept, using thermionic diodes, was dropped from active consideration because of its low end-to-end efficiency — about 4*% — and high weight requirements.) These power plants would probably be built on a modular concept, with each module containing a solar concentrator (mirrors), a cavity heat absorber, turbomachinery, and other subsystems. Both tne Brayton and Rankine cycles depend on high temperatures to heat the cavity heat absorber, requiring a concentration ratio of anout 1000 (compared with 2 to 5 for tne photovoltaic systems). A large area of mirrors would therefore be needed to concentrate the solar energy, a disadvantage both in terms of weight requirements and construction time. In a closed Brayton cycle SPS, helium is compressed and then heated by the solar energy, causing the gas to expand. This process generates power to run the turbines, after which the helium flows through a radiator where the heat is rejected into space, and then tne cycle begins anew. Temperatures of about 1380 degrees centigrade are required for this system to be competitive with an SSPS. The Rankine cycle operates in a manner similar to the Brayton cycle, but uses liquid cesium or potassium vapor as the cavity heat absorber, and can be competitive with SSPS using lower temperatures, about 1038 degrees centigrade. Initially, the Boeing Company sponsored a Brayton cycle SPS called Powersat, which would have consisted of 16 modules and produced 10,000 megawatts at tne rectenna with an end-to-end efficiency of about 9-10%. Boeing later concluded an SPS study showing a silicon photovoltaic system would be preferable to the Brayton cycle. Rockwell International has proposed a Rankine cycle SPS using liquid cesium as the cavity heat absorber and a steam bottoming cycle, with an expected end-to-end efficiency of 9.3%. Boeing's second choice tor an SPS is a Rankine cycle using potassium vapor. Rectenna design would be essentially the same for either the photovoltaic or solar thermal system. Each rectenna for a 5,000 megawatt SPS would be approximately 13 by 10 kilometers and would require about 270 square kilometers of land area, depending on its latitute (as latitude Increases, a "flashlight* effect occurs requiring larger, more elliptical rectennas) .. A 10,000 megawatt SPS would use two rectennas, rather than a single, large one. The orbiting microwave transmitters would consist of 7,220 subarrays, necessitating an automatic phasing system to ensure that the total power output from the transmitter would remain constant. A pilot signal emanating
from the rectenna's center would be needed as an aiming device to maintain automatic alignment between the rectenna and the transmitter. Misdirection of the bean could be precluded by circuiting which would stop transmission should alignment with the pilot signal deviate beyond an acceptable amount. Lasers have also been suggested as an alternative to microwaves for power transmission to Earth, although less investigation has been made of this possibility. INTERNATIONAL ASPECTS The SPS concept is international in character for a number or reasons. First, if the United States decides to pursue an SPS program, the resulting availability of electricity could make the United States an energy exporter, rather than importer. For example, the United States could construct and operate the SPSs, with receiving antennas located in other countries. Second, such a large-scale, expensive project could benefit from financial input from many countries. Japan and the European Space Agency (a consortium of 11 European nations plus Canada) indicated at international space program hearings held by the House Science and Technology Committee in May 1976 that they would be very interested in a cooperative SPS project. Third, the many potential problems associated with SPS (environmental effects, radio frequency interference, etc.) may require international negotiations and studies. TECHNICAL AND ECONOMIC FEASIBILITY Technical as mentioned earlier, NASA and DOE are currently in the midst of studies to determine the feasibility of SPS designs. The ultimate technical feasibility of the photovoltaic and solar thermal designs is rarely questioned, even by critics of the overall plan. Experience has already been acquired in operating both photovoltaic and solar thermal systems. Although construction of large space structures has not been demonstrated, insurmountable obstacles are not expected. Transmission of microwaves is another area in which experience already exists although not over such long distances. Objections to the SPS concept are not usually based on technical feasibility, but rather on economic and environmental concerns. Economic Factors Cost estimates for research, design, development, test, and evaluation (RDDT&E) of an SPS system can only be speculative at this early stage. Estimates for photovoltaic SPSs fall in the $60-80 billion range, while that for a solar thermal program might be somewhat higner, due primarily to the large area of concentrators (mirrors) required and attendant construction problems. These estimates Include development of a special Heavy Lift Launch Vehicle (HLLV) which would ne required for either SPS concept. The space shuttle, (see Issue brief 73019, Space Shuttle) which is expected to become operational in 1980, is not considered adequate by SPS advocates to support a full scale SPS program, although it might be able to serve as a transport vehicle through the prototype stage. HLLV would be fully reusable “space
truck" and it is hoped that costs for transportation of material into orbit would be about $10—20 per pound, considerably lower tnan what is expected for the shuttle. About half of SPS RDDT&E costs are for space transportation, requiring perhaps four different vehicles: the HLLV for transporting construction materiai from Earth to low Earth orbit (LEO), a Cargo orbital Transfer Vehicle (COTV) for taking that material from LEO to geosynchronous orbit (GEO), a personnel launch vehicle (PLV), for example the shuttle, for carrying people from Earth to LEO, and finally a personnel orbital transfer vehicle (POTV) for transporting crews from LEO to GEO. The naSA/DOE reference design estimated that for building two 5,000 megawatt SPSs per year, a silicon cell design would require 375 HLLV flights, 30 PLV flights, 30 COTV flights and 212 POTV flights; while a gallium system would require 225 HLLV tlights, 38 PLV flights, 22 COTV flights, and 17 POTV liignts. Peter Glaser has estimated the cost for an individual 5,000 megawatt commercial SSPS at approximately $7.5 billion including launch costs, or $1500 per Kilowatt. This would result m a cost before transmission (busbar cost), according to Glaser, of 27 mills per kiiowat hour. Less optimistic estimates suggest the cost to be about 55 mills per Kilowatt hour, and all these estimates are contingent upon the HLLV actually reducing space transportation costs to $10-20 per pound as well as a significant reduction in the cost of photovoltaic cells. During tne time it was proposing a Brayton cycle SPS, the Boeing Company estimated the cost of an individual Powersat at $13 billion. Advocates claim that SPS could be commercially available in the 1995-2000 time period. The number of SPSs required to meet U.S. electrical needs would depend on the rate of growth in demand over the next decades, although for April 1979, total U.S. electrical capacity was approximately 586,000 megawatts, meaning that fifty-nine 10,000 megawatt SSPSs would be needed to equal that capacity. Capacity is different from use, however. The use factor for present U.S. electrical power plants is only about 43%, since the plants need to be shut down for repairs for varying lengths of time. The SPS use factor is expected to be about 80-92%, so fewer SPSs could provide an equivalent amount or electricity. Considering the high RDDT&E costs of SPS, it seems unlikely that private industry would be able to completely fund such a program, although several industries (such as Boeing, Arthur D. Little, Grumman, and Rockwell International) are expending some of their own money for feasibility studies. In addition, the Sunsat Energy Council was established in April 1978 representing 25 U.S. scientific and industrial organizations. Formation of the Council was announced by former Senator Frank Moss at a Senate press conference on Apr. 6, 1978; Senator Moss is now legal counsel for Sunsat. Council President Peter Glaser reported that the group will study the technical, environmental, socio-economic, and institutional issues involved in tne development of SPSs, as well as trying to increase public awareness of SPS as an energy option. The Council's activities will be funded by contributions from member organizations and individual members, although this money will not be used for research and development of an SPS. Nevertheless, initial investment would almost certainly have to come from the Federal Government. SPS advocates argue that the government would spend equivalent or greater sums on energy research and development in the next fifteen years anyway, and that it could just as well be spent on SPS as on other energy sources. Conversely, the present Administration's emphasis is on short-term energy solutions, such as coal and conservation, and it appears unlikely that a concept such as SPS would receive sufficient support to
allocate requisite funding for SPS to become operational as early as 1995. CONGRESSIONAL INTEREST Through FY7b, SPS feasibility studies were performed for the government by the National Aeronautics and Space Administration (NASA) under the general category or advanced studies. For FY77, however, the Office of management and budget (Omb) transferred responsibility for SPS to the Energy Research and Development Administration (ERDA), now part of the Department of Energy (DOE). It was expected that money for SPS would be appropriated to ERDA, and ERDA would contract with NASA for services which that agency could best perform, especially in the area of space technology. The OMB action followed the perceived intent of the Solar Energy Research, Development and Demonstration Act of 1974 and the Energy Reorganization Act or 1974 which sought to centralize all solar energy programs. OMB's decision to transfer SPS to ERDA came late in the budget cycle, and as a result neither NASA nor ERDa requested any funding for SPS for FY77. Some congressional committees with jurisdiction over the NASA budget expressed dismay at the lack of a funding request for SPS. The House Science and Technology Committee ultimately added 15 million to NASA*s Budget for SPS, although the Senate Aeronautical and Space Sciences Committee did not follow suit. The Senate committee commented in its report on the NASA bill that although it was "sensitive to the addition by tne Rouse," it believed there was "little point in adding specific amounts for energy activities. Rather, [the committee} stresses the need for the Executive branch to promptly clarify the policies and procedures for carrying out tne intent of the Energy Reorganization Act of 1974. . . ." The conference committee on the authorization adopted the Senate*s position. During the PY77 appropriation process, a similar situation developed, with the House Appropriations Committee adding $5 million for SPS and tne Senate Appropriations Committee, nothing. This time tne conference committee adopted a middle ground and $2.5 million was finally added to NASABs FY77 budget. ERDA later added $.6 million to the effort. FY78 for PY78, NASA requested $1 million for SPS studies, while ERDA again requested no funding. During this time, ERDA was in tne process of preparing a plan for cooperation between itself and NASA in the field of satellite power stations. Once again, the house Science and Technology Committee added $5 million for SPS programs in NASA, for a total of $6 million. Again the Senate disagreed, pointing out that ERDA had been given the responsibility for managing such a program and it would only agree to inclusion oif the $1 million requested by NASA. Tne conference committee on tne authorization bill agreed to adding $3 million of the $5 million recommended by the house (P.L. 95—7b) . The appropriations committees found themselves in the identical situation, with the House adding $5 million and the Senate approving only the $1 million requested. The appropriations conference committee agreed upon adding $3 million of the $5 million added ny the House. Thus, NASA was appropriated $4 million for SPS studies in PY78, of which $2.3 million was later transferred to ERDA which added another $.5 million to the total (P.L. 95—119).
FY79 For FY79, DOE requested $4.6 million for SPS, while NASA requested no SPS funding. Although action on the FY79 authorization bill (H.R. 121b3) was not completed during the 95th congress, there was no dispute regarding the SPS request, and the $4.6 million is included in the FY79 appropriation bill for DOE research and development that was signed into law on Oct. 18, 1978 (P.L. 95-482). Despite the fact that NASA did not request any FY79 SPS funding, Congress added $2 million to the NASA appropriation bill (P.L. 95-392). This was a compromise Detween the $3 million added Dy the House and the zero addition Dy the Senate. A provision was made in the FY79 National Science Foundation (NSF) authorization bill for the Director of NSF, in consultation with the Administrator of NASA, the Secretary of Energy, the Director of the Office of Science and Technology Policy and others, to determine the need for NSF to provide support for a study of the feasibility of constructing SPSs from material mined from the Moon and/or asteroids. If the NSF Director decides that such a study is necessary, then $500,000 will be made available from the general NSF funds (that is, no additional money was granted to NSF for this study). The bill (H.B. 11400) was signed into law on Oct. 18 (P.L-95—414) , 1978. NSF is now in the process of negotiating a contract with the National Academy of Sciences (to be funded jointly by NSF and DOE) to perform such a study for completion in 1981. Other SPS Legislation in the 95th Congress In addition to the authorization and appropriation bills for NASA and DOE, three bills were introduced in the 95th Congress specifically relating to SPS. In the House, Congressman Bonnie Flippo (D—Ala) introduced H.R.10601 on Jan. 30, 1978 (later changed to H.R.12505), calling for establishment of a Solar Power Satellite Research, Development and Demonstration Program. A companion bill, S.2860, was introduced by Senator Mlecher. Hearings were held on the House bill by the Science and Technology Committee on Apr. 12, 13, and 14, 1978, and it was favorably reported from committee on May 6 (H.Rept. 95-1120). The House passed the bill on June 22 by a vote of 267-96. Hearings were held on the Melcher bill by the Senate Energy and Natural Resources Committee on August 14, although it was never reported from committee. Both these bills would have established an SPS program office within DOE, while allowing for contracted work to be done by NASA on the space segment of SPS. An appropriation of $25 million would have been made for Ff79 to study the major technical problems regarding the viability of the SPS concept. A third SPS bill, S.3541, was introduced on Sept. 30, 1978, Dy Senator Schmitt, focusing on NASA’s role in an SPS program. The SPS program office mould be set up in NASA, rather than DOE, in the Schmitt bill, and the same amount of money would have been appropriated for technical feasiDility studies. The bill was referred to the Committee on Commerce, Science and Transportation, where no action was taken. FY80
For FY80, the Administration has requested $8 million for SPS in the DOE budget, with no SPS money requested in the NASA budget. The House Science and Technology Committee recommended the $8 million for SPS in its report on the DOE authorization bill, H.R.3OOO, on Hay 16 (H.Rept. 96-196), and the Senate Energy Committee followed suit on June 26 (S.Rept. 95-232). The House Appropriations Committee reduced the SPS allotment to $6.5 million in its June 7 report (H.Rept. 96—243), and the House accepted that action in its vote on H.R.4388 on June 18. The Senate Appropriations Committee reduced the amount For SPS to $5.5 Million (S.Rept. 96-242, July 12), and tHe full Senate accepted that recommendation in passing the bill on July 18. On July 25, the Conference Committee reported the FY80 appropriation bill (H.Rept. 96—388) and accepted the Senate's position of reducing the amount requested tor SPS to $5.5 million. The House passed the conference report on Aug. 1. On Feb. 22, 1979, Congressman Flippo and a number of co-sponsors introduced H.R. 2335, the Solar Power Satellite Research, Development and Evaluation Program Act of 1979. The bill is essentially similar to H.R. 12505 passed by congress in 1978. The primary difference is the substitution of the word "Evaluation" for "Development." This change was made to clarity the intent of the bill to provide for an evaluation of SPS feasibility rather than for actual construction of an SPS prototype or a commitment to an SPS commercialization program. The bill was referred to the House Committee on Science and Technology, where hearings were held on Mar. 28, 29, and 30. The committee favorably reported the bill on May 15 (H.Rept. 96-l51). ISSUES OF CONCERN Environmental Three areas of possible environmental impact of commercially operating SPS stations are: (1) microwave radiation affecting the atmosphere as it is transmitted from space to Earth; (2) microwave radiation effects at the rectenna site; and (3) possible atmospheric damage caused by pollutants emanating from tne launch vehicles used to transport SPS construction material into orbit. Regarding the first question, SPS advocates are convinced that the beam will be of such low power density that it will not affect either the atmosphere itself (through heating), or birds, or aircraft passing through it. Others feel that there is too little information about the impact of microwaves on these objects to make such a determination and that further study is needed. Hicrowave radiation dangers at the rectenna site are also not regarded as serious by SPS advocates, who claim that the rectennas could be shielded so that little or none of the radiation would pass through to the ground underneath, and that the level of microwave radiation at the rectenna's perimeter would be well within current standards for exposure. (One problem with this is that no international standard for microwave radiation exposure now exists. The U.S. standard for occupational exposure is considerably higher than that permitted in the Soviet Onion, and U.S. standards are currently being reviewed.) Regarding land usage for the rectennas, SPS advocates suggest that a fence surrounding the rectenna's perimeter would be sufficient to prevent accidental exposure to the higher level of radiation at the center of the rectenna. DOE does not agree, however, stating in a November 1976 report
(see REFERENCES under ERDA) that each rectenna might require an "exclusion area" twice tne radius of the rectenna itsell or more, if for no other reason than public opinion. Should this higher estimate prove true, land investments might be extremely high ror a commercial SPS system, since each SPS requires at least one rectenna. A third possible environmental problem is damage to the atmosphere from exhaust fumes expelled by launch vehicles transporting personnel into space, especially considering the large number of launches required per SPS. Charles Bloomquist (see REFERENCES) has stated that with 360 shuttle launches per year, "up to a 2% increment in [water] may accrue in the 25-30 mile (40-50 km) altitude range," as well as possible difficulties with hydrogen chloride and aluminum oxide from tne solid rocket boosters. The HLLV planned for carrying SPS construction material would use liquid fuel so is not of concern in this regard. Radio Frequency Interference The DOE/NASA reference design for SPS selects 2.45 gigahertz as the frequency ror beaming the electricity produced by an SPS down to Earth from geosynchronous orbit. At the present time, there are a large number of operating satellites in space at various frequencies, and the trend appears to suggest that even more will be operating by the time an SPS system could become commercially available. Proposals call for a large number of SPS stations, which together with their high power levels, could cause a severe radio frequency interference pattern with other satellites and/or ground-based systems in the vicinity of the rectenna. This is another subject requiring further study. Resource utilization Some concern has been expressed by Summers, et al. (see REFERENCES) over the amount or aluminum required to construct an orbital photovoltaic SPS and its associated rectenna. Those authors reported that for each 10,000 megawatt SSPS, over one million metric tons of aluminum would ne needed, or 13% of U.S. reserves (0.8% of the world's reserves). Glaser has commented that "materials necessary for construction are largely those in plentiful supply, such as silicon and aluminum." Although his case may be true on a world-wide scale, it seems conceivable that imports might be required for some of tne construction materials. This, too, is speculative, however, for some new type of material might be developed prior to initiation or an SPS program. as mentioned earlier, if gallium arsenide is chosen for a photovoltaic SPS, there may ne a problem with gallium availability. DOE identifies four materials that could present problems in availability: mercury, tungsten, silver, and gallium. funding Prior to FI 77, NASA was responsible for conducting studies of SPS designs and aid so under general categories such as "advanced studies." Exact numbers are therefore not available for years prior to FY77. For FY77, $2.5 million was appropriated to NASA for SPS, and ERDA added another $.6 million. For FY78, NASA was appropriated $4 million, although $2.3 million of that amount was transferred to ERDA, which added another $.5 million to the effort. For FY79, NASA requested no funding for SPS, although Congress
appropriated $2 million to the agency for SPS worK anyway. The $4.6 million requested by DOE was appropriated. For FY80, DOE has requested $8 million for SPS, while NASA has requested no SPS funding. [See “Congressionai Interest" and “Legislation* sections for further information.j These funding levels are for SPS specifically. NASA has identified another $47.1 million in FY80 from other programs that could relate to SPS. LEGISLATION H.E. 2335 (Flippo) Solar Power Satellite Research, Developnent and Evaluation Program Act of 1979. Would establish an office within the Department of Energy to manage a Solar Power Satellite Research, Development, and Evaluation Program, and authorize $25 million for FY80 for the program. Hearings were held on Mar. 28, 29, and 30, 1979. The committee favorably reported the bill on May 15 (H.Rept. 96—151). H.R. 4388 (Bevill) Energy and Water Development Appropriation Bill, 1980. Reported from House Appropriations Committee on June 7, 1979 (H.Rept. 96—241). The Committee recommended a reduction in SPS funding from the $8 million requested to $6.5 million, stating that it felt such funding "should be adequate to meet essential needs in these areas, considering the funding available for similar activities in other areas of the Department." The bill passed the House on June 18. The Senate Appropriations Committee reduced the amount for SPS to $5.5 million (S.Rept. 96-242, July 12), and the full Senate accepted that recommendation in passing the bill on July 18. On July 25, the Conference Committee reported the FY80 appropriation bill (H.Rept. 96-388) and accepted the Senate*s position of reducing the amount requested for SPS to $5.5 million. The House passed the conference report on Aug. 1. S. 688 (Jackson)/H.R. 3000 (Staggers) FY80 DOE Civilian Applications Bill. Includes a request for $8 million for SPS studies. The House Science and Technology Committee reported the bill on May 16 (H.Bept. 96-196), including the requested amount for SPS, and the Senate Energy Committee followed suit on June 26 (S.Rept. 96-232). HEARINGS U.S. Congress. House. Committee on Science and Astronautics. Subcommittee on Space Science and Applications. Energy Research and Development and Space Technology. Hearings, 93rd Congress, 1st session. Washington, U.S. Govt. Print. Off., 1973. 570 p. Hearings held Hay 7, 22, and 24, 1973. U.S. Congress. House. Committee on Science and Technology. Subcommittee on Space Science and Applications and Subcommittee on Advanced Energy Technologies and Energy Conservation Research, Development and Demonstration. Solar Power Satellite. Hearings, 95th Congress, 2d session. Washington, U.S. Govt. Print. Off., 1978. 458p.
Hearings held Apr. 12, 13, 14, 1978. U.S. Congress. House. Committee on Science and Technology. Subcommittee on Space Science and Applications and Subcommittee on Energy Research, Development and Demonstration. Solar Satellite Power System concepts. Hearings, 94th Congress, 2d session. Washington, U.S. Govt. Print. Off., 197o. 653 p. Hearing held Feb. 20, 1976. U.S. Congress. Senate. Committee on Aeronautical and Space Sciences. Subcommittee on Aerospace Technology and National Needs. Solar Power from Satellites. Hearings, 94th Congress, 2d session. Washington, U.S. Govt. Print. Off., 1976. 230 p. Hearings heid January 19 and 21, 1976. REPORTS AND CONGRESSIONAL DOCUMENTS U.S. Congress. House. Committee on Appropriations. Public Works for Water and Power Development and Energy Research Appropriation Bill, 1979; report to accompany H.R. 12928. Washington, U.S. Govt. Print. Off., 1978. 143 p. (95th Congress, 2d session. House. Report no. 95- 1Z47) U.S. Congress. House. Committee on Science and Technology. Authorizing appropriations to the National Aeronautics and Space Administration [FY1979; report to accompany H.R. 11401. Washington, U.S. Govt. Print. Off., 1976. 238 p. (95th Congress, 2d session. House. Report no. 95—973) ----- Authorizing appropriations for the Department of Energy for fiscal year 1979; report to accompany H.R. 12163. Washington, U.S. Govt. Print. Off., 1978. 356 p. (95th Congress, 2d session. House. Report no. 95-1078, Part I) ----- Establishment of a Solar Power Satellite Research, Development, and Demonstration Program; report to accompany H.R. 12505. Washington, U.S. Govt. Print, Off., 1978. 21 p. (95th Congress, 2d session. House. Report no. 95-1120) U.S. Congress. Senate. Committee on Commerce, Science, and Transportation. NASA authorization for fiscal year 1979; report on H.R. 11401. Washington, U.S. Govt. Print. Off., 1978. 72 p. (95th Congress, 2d session. Senate. Report no. 95—799) CHRONOLOGY OF EVENTS 08/01/79 — House passed conference report on FY80 energy and water development appropriation bill. 07/25/79 — Conference committee reported FY80 energy and water development appropriation bill (H.Rept. 96—388) accepting the Senate's position of reducing the
amount requested for SPS to $5.5 million. 07/18/79 — Senate passed H.B. 4388, Energy and Water Development. Appropriations Bill, 1980, with no change to the committee recommendation for SPS. 07/12/79 — Senate Appropriations Committee reported H.R. 4188, Energy and Water Development Appropriations Bill, 1980, reducing the request for SPS from $8 million to $5.5 million (S.Rept. 9 6-242). 06/26/79 — Senate Energy Committee reported DOE FY80 authorization bill, recommending the $8 million requested for SPS (S.Rept. 96-232). 06/18/79 — House passed the 1980 Energy and Hater Development Appropriations bill concurring with the House Appropriations Committee recommendation for SPS. 06/07/79 — House Appropriations Committee reported H.R. 4388, the Energy and Water Development Appropriations Bill, 1980, recommending a decrease in the request for SPS from $8 million to $6.5 million (H.Rept. 96-243). 05/16/79 — House Science and Technology Committee reported H.R. 3000, the DOE FY80 authorization bill, recommending the $8 million requested for SPS (H.Rept. 96-196, Part 3). 05/15/79 — House Science and Technology Committee favorably reported H.R. 2335 (H.Rept. 96-151). 02/22/79 — H.R. 2335 was introduced to provide for a Solar Power Satellite research, Development and Evaluation Program. 01/10/79 — American Institute of Aeronautics and Astronautics released a position paper calling for expanded funding tor SPS research, Dut stating that it is too early to commit to development or demonstration of the concept. 04/06/78 — Creation of the Sunsat Energy Council was announced at a Senate press conference. The Council, composed of representatives from 25 U.S. scientific and industrial organizations, will try to publicize the sps option. 10/01/77 —Department of Energy, consolidating the functions of several agencies including the Energy Research and Development Administration, was created. 01/20/75 — The Energy Research and Development Administration was created, becoming the lead agency for ail soiar energy research and development. 10/26/74 — The Soiar Energy Research, Development, and Demonstration Act was enacted, providing for a
national solar energy progran. 11/22/68 — Peter Glaser first proposed the development of satellite power stations in an article in Science (see REFERENCES). ADDITIONAL REFERENCE SOURCES American Institute of Aeronautics and Astronautics. Solar power satellites: an AIaa position paper. Astronautics and Aeronautics, January 1979: 14-17. Bloomquist, Charles E. Survey of satellite power stations. Prepared for the task group on satellite power stations, Energy Research and Development Administration. McLean, Va., PRC Systems Science Co., September 197b. PRC R-1844. 269 p. ECON, Inc. Political and legal implications of developing and operating a satellite power system: final report. Princton, New Jersey, ECON, Inc., Aug. 15, 1977. 169 p. Glaser, Peter E. Power from the sun: its future. Science, Nov. 22, 1968: 857-861. ----- Solar power from satellites. Physics today, February 1977: 30-36. Killian, Harrison J., Gordon L. Dugger and Jerry Grey, eds. Solar energy tor earth: an AIAA assessment. New York, American Institute of Aeronautics and Astronautics, Apr. 21, 1975. 110 p. Solar power from satellites — some questions. Physics today, July 1977: 9, 11, 15, 66-69. (Responses to Peter Glaser's February 1977 Physics Today article). Summers, Robert A., H. Richard Bleiden and Charles E. Bloomquist. Assessment of satellite power stations. Paper presented at third Princeton/AIAA conference on Space Manufacturing Facilities, Princeton, N.J., May 9-12, 1977. New YorK., American Institute of Aeronautics, 1977. No. 77-552. (unpaginated) U.S. Department of Energy and the National Aeronautics and Space Administration. Satellite Power System: Concept Development and Evaluation Program — Reference System Report. Washington, U.S. Dept, of Energy, October 1978 (Published January 1979) . DOE/ER—0023. various pagings U.S. Energy Research and Development Administration. Final report of the ERDA task group on satellite power stations. Washington, Energy Research and Development Administration, November 1976. 14 p. U.S. Library of Congress. Congressional Research Service. Science Policy Research Division. Fact book on non-conventional
from the Space Studies Institute Resaarch Library - ssi.org
energy technologies. Prepared, for a seminar on new energy technologies: policies and problems. Feb. 21, 1979. Washington, 1979. 198 p. (Reprint no. 79-47 SPR) ----- Soiar power [byj J. Glen Hoore. (Continuously updated) Issue brier 74059 U.S. National Aeronautics And Space Administration. George C. Marshall Space Flight Center. Satellite power systems: an engineering and economic analysis summary. NASA TM X-73344. Washington, U.S. Govt. Print. Otf., 1977. (various pagings)
SOLAR ENERGY FROM SPACE: SATELLITE POWER STATIONS ISSUE BRIEF NUMBER IB78012 AUTHORS: Smith, Marcia S. Science Policy Research Division THE LIBRARY OF CONGRESS CONGRESSIONAL RESEARCH SERVICE MAJOR ISSUES SYSTEM DATE ORIGINATED 02/14/78 DATE UPDATED 09/12/79 FOR ADDITIONAL INFORMATION CALL
CBS-1 IB78012 UPDATE-09/12/79 ISSUE DEFINITION In the quest for new, inexhaustible sources of energy, solar energy has become a promising contender, because the Sun's energy is not expected to be depleted for six billion years. Several factors prevent solar energy from falling freely onto the Earth's surface, however, leading to the concept of building electric power plants which utilize solar energy in Earth orbit. Electricity generated by these stations would be beamed down in the form of microwaves to receiving antennas located on the planet's surface. This concept is referred to as satellite power stations (SPS). Through the authorization and appropriation process, Congress has demonstrated a consistent interest in pursuing feasibility studies of an SPS program. The Executive branch has appeared less enthusiastic about the concept, and a 1976 Office of Management and Budget decision transferred responsibility for the program to the Energy Research and Development Administration (now part of the Department of Energy) from the national Aeronautics and Space Administration, which had previously performed the feasibility studies. This transfer of responsibility was viewed in some quarters as a downgrading of the program, especially when ERDA did not request any funding for SPS in its FY77 budget. In the 95th and 96th Congresses, specific legislation has been introduced to increase funding for determining the technical, economic, and environmental feasibility of the concept. BACKGROUND AMD POLICY ANALYSIS Solar energy is receiving increasing attention as an electrical power source, either through direct conversion of sunlight into electricity (photovoltaics) or by using the energy to heat working fluids which operate conventional turbines (solar thermal). Solar energy, however, is prevented from failing freely onto the Earth's surface by inclement weather, the diurnal cycle, and the screening effects of the atmosphere (on a clear day, the amount of sunlight reaching the ground is about 65% of that above the atmosphere). Solar energy systems on the surface of the planet would therefore require storage systems for those times when solar energy is not available, making them less attractive as a base load power source. Alternatively, these power plants could be placed in orbit around the Earth where sunlight is both continuously available and more intense. Called satellite power stations (SPS), they would be placed in geosynchronous orbit where an object maintains the same position relative to a given point on the globe. Although the SPS would be eclipsed by the Earth's shadow for varying periods of time each day, the eclipse time would never exceed 72 minutes, meaning the system could theoretically operate for 99% of the year, an attractive feature for a base load power source. Because of the need for periodic maintenance, however, plant factors of 80% - 92% have been estimated. Tne electricity would be produced at the orbital station and converted into microwaves, then beamed down to receiving and rectifying antennas (called rectennas) on the planet's surface where the microwaves would be reconverted into electricity. At the present time, the SPS concept is still in the feasibility determination stage, making judgments about it difficult to render. NASA and
DOE are now nearing the end of a 3—year study of the various SPS designs described below. Once the results of those studies are available (scheduled for early 1980), a decision can be made as to whether to proceed with a prototype SPS or to shelve the concept temporarily or permanently. In January 1979, DOE and NASA published a reference design for SPS, selecting a photovoltaic system constructed in geosynchronous Earth orbit, generating 5,000 megawatts of power. In doing so, the agencies set aside designs for a solar thermal nature. For completeness, this issue brief describes both concepts. Before discussing the two most common SPS concepts, photovoltaic and solar thermal, it should be noted that two other designs are sometimes included under the rubric of SPS. The first suggests placing nuclear power plants in orbit, primarily to ease siting restrictions and environmental concerns. This system would not benefit from the greater availability or intensity of sunlight in orbit. Also, concerns about nuclear reactor—bearing satellites were heightened when a Russian satellite (Kosmos 954) accidentally deorbited and landed in northwestern Canada in January 1978. The other guasi-SPS design is a Power Relay Satellite (PRS), proposed by Krafft Ehricke (of Space Global, Inc.). As its name implies, this satellite would relay power generated by solar power plants, not produce the power itself, and therefore does not qualify in the SPS category - According to the Ehricke plan, solar power plants on the surface of the planet would generate electricity which would be converted into microwaves, then beamed up to the PRS and back down to an area requiring the power and reconverted into electricity. PRS is designed to accommodate the requirement that solar power stations be located in sunny regions (such as Arizona), while the power they produce may be needed in less sunny places like Syracuse, New York. SPS TECHNOLOGY The photovoltaic concept, or SSPS for Satellite Solar Power Station, was first proposed Dy Peter Glaser of Arthur D. Little, Inc., in 1968. His plan calls for constructing arrays of solar cells in space for the direct conversion of sunlight into electricity. a 5,000 megawatt SSPS (measured at the rectenna) would consist of two arrays, each approximately 5 by 6 Kilometers, separated by the microwave transmitter, and would generate 9,300 megawatts of power at the orbital station. An SSPS could also be designed to produce 10,000 megawatts at the rectenna. A reaction control system would be required to maintain the satellite in its desired orbit and to keep the solar arrays pointed continuously toward the Sun. Mirrors could be used to concentrate the solar energy onto the arrays. The solar cells could be made of either silicon or gallium arsenide (or other substances which may develop from future research). Silicon solar cells are the type in common usage today, and it is considered possible that these cells could attain an efficiency rating of 18% (converts 18% of light received into electricity) by the time an SSPS would be in use (compared with the 11—15% efficiency factor now achievable). Gallium arsenide cells are expected to have a higher efficiency, perhaps as high as 27%. They are also less susceptible to damage from space radiation and can provide higher efficiencies at higher temperatures, allowing concentration ratios (use of mirrors to intensify sunlight) up to 5 (silicon cells can operate efficiently with a concentration ratio of only about 2.) Until recently, gallium arsenide was also considered superior to silicon because it could operate with full performance at a thickness of 5 microns, while silicon began losing its efficiency at a thickness less than 100 microns. New research, however,
has shown that, although the efficiency of silicon cells does decrease somewhat as the cell becomes thinner than 100 microns, the efficiency increases again as the cell becomes even thinner. It is now expected that a silicon cell 5 microns in thickness would have comparable efficiency to the gallium arsenide cells. End—to—end efficiency of an SSPS system is expected to be about 7.06% for a silicon ceil design, and 6.97% for a system using gallium arsenide, assuming a cell efficiency of 16.5% for silicon and 18.2% for gallium arsenide. The major factors in favor of silicon cells are familiarity in working with them and a possible supply problem with gallium. In the DOE/NASA reference design, no choice was made between the two solar cell options. Solar thermal systems involve focusing solar energy with mirrors into a cavity containing a heat absorber (helium, potassium vapor, or liquid cesium) which becomes heated and drives a turbine which produces electricity. The solar thermal concepts most often discussed are the closed Brayton cycle and the Rankine cycle. (A third concept, using thermionic diodes, was dropped from active consideration because of its low end-to-end efficiency — about 4% — and high weight requirements.) These power plants would probably be built on a modular concept, with each module containing a solar concentrator (mirrors), a cavity heat absorber, turbomachinery, and other subsystems. Both the Brayton and Rankine cycles depend on high temperatures to heat the cavity heat absorber, requiring a concentration ratio of about 1000 (compared with 2 to 5 for the photovoltaic systems). A large area of mirrors would therefore be needed to concentrate the solar energy, a disadvantage both in terms of weight requirements and construction time. In a closed Brayton cycle SPS, helium is compressed and then heated by the solar energy, causing the gas to expand. This process generates power to run the turbines, after which the helium flows through a radiator where the heat is rejected into space, and then the cycle begins anew. Temperatures of about 1380 degrees centigrade are required for this system to be competitive with an SSPS. The Rankine cycle operates in a manner similar to the Brayton cycle, but uses liquid cesium or potassium vapor as the cavity heat absorber, and can be competitive with SSPS using lower temperatures, about 1038 degrees centigrade. Initially, the Boeing Company sponsored a Brayton cycle SPS called Powersat, which would have consisted of 16 modules and produced 10,000 megawatts at the rectenna with an end-to-end efficiency of about 9-10%. Boeing later concluded an SPS study showing a silicon photovoltaic system would be preferable to the Brayton cycle. Rockwell International has proposed a Rankine cycle SPS using liquid cesium as the cavity heat absorber and a steam bottoming cycle, with an expected end-to-end efficiency of 9.3%. Boeing's second choice for an SPS is a Rankine cycle using potassium vapor. Rectenna design would be essentially the same for either the photovoltaic or solar thermal system. Each rectenna for a 5,000 megawatt SPS would be approximately 13 by 10 kilometers and would require about 270 square kilometers of land area, depending on its latitude (as latitude increases, a “flashlight” effect occurs requiring larger, more elliptical rectennas). A 10,000 megawatt SPS would use two rectennas, rather than a single, large one. The orbiting microwave transmitters would consist of 7,220 subarrays, necessitating an automatic phasing system to ensure that the total power output from the transmitter would remain constant. A pilot signal emanating
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