SPACE SOLAR POWER REVIEW Volume 5, Number 3, 1985 PERGAMON PRESS New York / Oxford / Beijing / Frankfurt / Sao Paulo / Sydney / Tokyo / Toronto
SPACE SOLAR POWER REVIEW Published under the auspices of the SUNSAT Energy Council Editor-in-Chief Dr. John W. Freeman Space Solar Power Research Program Rice University, P.O. Box 1892 Houston, TX 77251, USA Associate Editors Dr. Eleanor A. Blakely Lawrence Berkeley Laboratory Colonel Gerald P. Carr University of Texas Dr. M. Claverie Centre National de la Recherche Scientifique Dr. David Criswell California Space Institute Mr. Leonard David PRC Energy Analysis Company Mr. Hubert P. Davis Eagle Engineering Professor Alex J. Dessler Rice University Mr. Gerald W. Driggers, President L-5 Society Mr. Arthur M. Dula Attorney: Houston, Texas Editorial Assistant: Jean S. McHenry Professor Arthur A. Few Rice University Mr. I. V. Franklin British Aerospace, Dynamics Group Dr. Owen K. Garriott National Aeronautics and Space Administration Professor Norman E. Gary University of California, Davis Dr. Peter E. Glaser Arthur D. Little, Inc. Professor Chad Gordon Rice University Dean William E. Gordon Rice University Dr. Arthur Kantrowitz Dartmouth College Mr. Richard L. Kline Grumman Aerospace Corporation Dr. Harold Liemohn Boeing Aerospace Company Dr. James W. Moyer Southern California Edison Company Professor Gerard K. O'Neill Princeton University Dr. Eckehard F. Schmidt AEG—Telefunken Dr. Klaus Schroeder Rockwell International Professor George L. Siscoe University of California, Los Angeles Professor Harlan J. Smith University of Texas Mr. Gordon R. Woodcock Boeing Aerospace Company Dr. John Zinn Los Alamos Scientific Laboratories Editorial Office: John W. Freeman, Editor-in-Chief, Space Solar Power Research Program, Rice University, P.O. Box 1892, Houston, TX 77251, USA.
0191-9067/85 $3.00 + .00 Copyright ® 1985 SUN SAT Energy Council EDITORIAL Has the U.S. lost its lead in Space Solar Power research? According to a report from Moscow World Service, “The Soviet Union intends to carry out, already before the end of this century, a major program termed by experts as a star electricity project.” The report goes on to describe an orbiting solar energy system that sounds like a solar power satellite and to report that Soviet Cosmonauts have already tested assembly techniques for the solar panels in orbit. Moreover, Soviet Scientist Leonid Leskov writing in Space Policy (February, 1985) describes further ideas relating to energy systems for space including orbiting reflectors to provide continuous sunlight on collectors on the Earth’s surface. In Japan, annual meetings are being held dealing with space energy systems for terrestrial application (Space Solar Power Review, Volume 5, No. 2, 1985). In the U.S. there is no government support for Solar Power Satellite research at the present time. A modest study is being conducted by Space Research Associates for the Space Studies Institute to develop an SPS design based on the use of lunar materials. It is probable that the substantial SPS related generic research will be accomplished under the Strategic Defense Initiative. There is no funded effort to monitor and evaluate this research for its SPS application. The U.S. SPS momentum developed in the late 70’s and 80’s is slipping away due to a crowded list of space priorities and errors in judgement. Ironically, the push for increased commercialization of space grows stronger but terrestrial energy applications of space continue to be excluded from the list of prospective space industries. John W. Freeman Editor-in-Chief
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0191-9067/85 $3.00 + .00 Copyright ® 1985 SUN SAT Energy Council SOLAR ENERGY — DREAMS AND REALITY* H. TABOR Scientific Research Foundation Hebrew University Campus P.O.B. 3745 Jerusalem, Israel Abstract — Fossil fuel reserves will last decades, not centuries. The options are: reduced rate of energy consumption, nuclear and renewables. Concentrating on the last, in particular solar energy, this paper shows both the possibilities and the limitations, in particular that the income of solar radiation is limited. This highlights the importance of the solar space-satellite concept. A pre-requisite to understanding the part that solar energy can play in the total world energy picture is an examination of fossil fuel reserves and other potential sources of energy. Additionally, we must know the present and estimated future consumption of energy on a global scale. Until 1970, world energy consumption was rising at about 5% a year, i.e., consumption doubled in about 14 years. One effect of the energy crisis of the mid-70s was that the annual rate of growth of consumption has dropped to about 2% — or a doubling time of 35 years. Table 1 shows the best estimates of reserves of the three major fossil fuels — oil, gas and coal — with the ultimate reserves including sources not considered exploitable at present. Table 2 shows how long these reserves would last on the basis of a 2% or 5% annual increase in consumption. (The bottom line of this table assumes that most users will have switched to coal, as this represents the major reserves.) The startling result is that the reserves are adequate for decades, not centuries as often claimed. Table 2 is mathematically correct but will, in practice, be modified by economic and social factors. The major economic factor is that as the reserves dwindle, the cost of ‘winning’ them will go up and this could result in a reduced consumption rate. Against this is the social factor resulting from the difference between the developed (industrialized) countries and the developing world. At the present time the industrial world comprising 20% of the world’s population consumes 80% of the world’s energy with the figures reversed for the developing world: on a per capita basis, the energy consumption in the industrialized countries is 16 times that in the developing world. *Lecture to the IEA workshop on “Large Thermal Solar Systems" held in San Diego, California, June 1984.
From this we see that, if the developing nations were to try — even partially — to catch up with the developed nations in energy consumption per capita — for example by mechanizing their agriculture and by industrial development — the world would be faced with an energy crisis of unimaginable proportions. And who can tell Vh billion impoverished people that they have to stay as they are? Since it takes several decades to introduce, on a large scale, any new energy technologies — and we only have a few decadest of fossil fuel reserves left — alternative scenarios must be considered. THE OPTIONS Essentially there are three: 1. Reduce the rate of growth of energy consumption. 2. The nuclear option. 3. The renewables. 1. Reduction in Energy Use If the annual rate of increase of energy consumption were brought down to zero, the proven reserves would last about a century and the ultimate reserves — if they could be exploited — would extend this a further century. But it is not realistic to expect the developing world to remain at its present low level of energy consumption even if the industrialized countries could reduce their energy-consumption tlf new exploitable reserves were discovered equal to the total in Table 1, the lifetime would be extended by only 14 years, at the 5% per annum increase rate or by 35 years at the 2% rate!
growth rate to zero: the proven reserves would then last about 90 years and the ultimate reserves about 133 years. But a zero growth rate would mean an actual negative per-capita growth rate when allowing for population growth. We are aware that considerable economies in energy consumption are possible in the developed world: vehicles could be made smaller; passive design of buildings could save a considerable amount of energy; energy waste in industry could be reduced. But all this calls for considerable effort and a disciplined public.* Thus the earlier conclusion, that reserves will last decades, not centuries, appears to be the realistic appraisal. 2. The Nuclear Option Whilst there will undoubtedly be some local increase in nuclear power production, the picture on a large scale appears to be that nuclear energy will not replace the diminishing fossil fuels. The reasons for this appraisal are: a. the nuclear lobby has not allayed the fears of a large part of the public on the potential dangers of nuclear stations. This is accentuated by b. the world is far more vocal than it was fifty years ago: measures which, even in the democracies, could be pushed through by a strong government can face very serious and effective blocking opposition today. c. no really satisfactory solutions have been offered concerning the disposal of radio-active waste, now accumulating in the stores at existing nuclear power stations. d. the production of weapons-grade plutonium is a source of great anxiety in a world racked by international terrorism. e. many utilities are reluctant, in an uncertain world, to make the very large investments that nuclear stations involve. The above remaks refer to current types of light-water and heavy-water fission reactors. What of the possibilities of nuclear fusion? Here there is almost no limitation of fuel, i.e., deuterium from the oceans. The prognosis is not very encouraging when we realize that the finest brains in the world have been working for the last fifty years trying to obtain a controlled fusion reaction without success. This is no proof that success will not come in the near future, but the probability is low, and it would be grossly irresponsible to build a scenario for future energy supplies based upon the assumption that controlled fusion will be achieved. 3. The Renewables These include a few small sources, such as wave energy, tides and geothermal energy! and the major source, solar energy, and its derivatives wind and hydropower. Thus, what appears to be the only option available has created both the challenge and the attraction of harnessing the sun. Can we see the sun replacing our fossil fuels as these become exhausted; This is the dream. What is reality? *The oil shortage in the mid-seventies resulted in a drop off of sales of large cars in the U.S. But a few years later these sales were rising again. tThis is renewable if one is prepared to wait several decades after a well has become depleted.
We first note that whilst solar energy is renewable ad infinitum, it is not infinite in its rate of energy supply. Thus, the total insolation on the surface of the globe is approximately 10,000 times the total present energy use and we define a local “solar ratio” as the ratio of the total insolation on a given area to the energy use in that area. Since the oceans cover approximately two-thirds of the surface of the globe, the solar ratio for the land areas is approximately 3,000. Table 3 shows the solar ratios for several specific areas. The figures for the highly industrialized areas such as the UK+ are startling: solar converters of 1% net efficiency could not supply the energy needs even if the entire country were covered with converters! It is also important to note that, unlike entropy, the solar ratio is constantly decreasing as consumption rises and the supply remains the same. How much of the solar radiation in any area can we exploit? This depends upon the conversion efficiency with some examples given in Table 4. Thus, the dream of vast areas of bio-converters — even of much improved species — is limited to a few areas of the world where population density (i.e., energy consumption per unit land area) is low and the land is cheap. Putting collectors or PV panels on roofs is an approach for overcoming, in part, the solar ratio limitation. Thus, Israel has some three million sq m of collectors on tThe solar ratio for West Germany is almost identical to that for the UK.
the roofs (which save 2% of the country’s fuel bill) and take up no land area. These rooftops could accommodate ten times this area of collectors or PV panels if a local use could be found for the heat collected or, in the case of PV panels, if the electricity could be coupled into the grid. The design of buildings to exploit solar radiation to reduce consumption of fuels for heating and lighting is another example of overcoming the solar ratio limitation in part: more space must be left between the buildings than would otherwise be the case. The dream of each household generating its own electricity needs from the sun is still a long way off. This is not just a question of cost (currently between 50-100 US cents /kWh) but of statistical load sharing: batteries could help on short-term storage, but seasonal storage would be very difficult. Much fossil fuel is consumed for the propulsion of vehicles. Power for vehicles could come from the sun using bio-coverters producing oils directly — such as the copafera plant proposed by Prof. Calvin — but the net conversion efficiencies are extremely low, thus severely limiting this approach. Alternatively, electric vehicles could be driven with electricity produced from the sun by any of the proposed methods, with the advantage that this integrates with non-solar sources of electricity. So far we have discussed limitations of availability of solar energy. But costs are also a limitation. The simplest, high-efficiency thermal converters — for such purposes as water heating — are currently economically viable in sunny areas. As one moves to less sunny areas and to more sophisticated collector systems, the economic viability decreases. In particular, the sophisticated tracking systems may involve high maintenance costs and at least two recent reports from the field on tracking trough-type collector systems have shown that the value of the energy produced did not cover the cost of maintenance! From this we have to pursue the philosophy that the sophistication should be in the thinking, not in the hardware. (A classical example of this is the salt-gradient solar pond where the scientific background and engineering planning are both highly sophisticated, leading to a relatively simple low-cost collector system). The limitations of solar energy availability mentioned above do not provide any excuse for not exploiting solar energy wherever possible, any more than Carnot’s restrictive law prevents engineers burning millions of tons of fuel every year to produce power in a highly ‘inefficient’ process! In particular, the high solar ratio in the developing world indicates that, in many areas, there will be ample solar radiation (provided these areas are not in too much of a hurry to catch up — in energy consumption — with the industrialized world). Since the areas of high solar ratio are those with low energy consumption, an important field for R and D is that of energy transport over long distances. High- temperature dissociation of chemicals to form gases that can be transported by pipeline and re-combined at the far end, is being studied as a possible means of low-cost energy transport. The limitation in insolation availability point to two lines of approach, apart from a constant effort to raise conversion efficiencies: 1. To find ways of using part of the 2/3 of total solar radiation that falls on the oceans. OTEC (ocean temperature energy conversion) is one example, but the difficulties are considerable. Other examples are extension of marine agriculture and the concept of underwater habitations to reduce the congestion on the land areas. 2. To go into outer space to collect solar radiation that would not, otherwise, reach
the Earth, i.e., the space solar satellite beaming converted solar energy to Earth via microwaves. This was the dream of Peter Glaser and his colleagues some 10—15 years ago — considered then as science fiction, but no longer such: (a) efficient energy transfer by microwaves has been demonstrated; (b) a space shuttle has been realized, making manned space stations a practical proposition. This has led to recent proposals and predictions of sending people off the Earth into outer space because the space on Earth is getting overcrowded (i.e., shortage of materials and energy). It would appear to me more sensible to ship energy to the Earth than to ship people out. This is a solar dream that I believe is feasible: it needs a major decision of the type taken to send a man to the moon. The truth is — as indicated earlier — we don’t have many alternatives.
0191-9067/85 $3.00 + .00 Copyright ® 1985 SUNSAT Energy Council COOPERATION OF MULTIDISCIPLINARY RESEARCH ACTIVITIES FOR SPS* MAKOTO NAGATOMO Institute of Space and Astronautical Science 4-6-1 Komaba Meguro-ku Tokyo 153 Japan Abstract — Although the basic principles of the SPS system are known very well, the system for future electrical power is so large and complicated that more extensive study in the individual disciplined fields are required to identify and to solve problems between disciplinary areas. In the early stage of the study, prior to starting dedicated study for SPS, researchers had to rely on general data of known facts within the framework of existing disciplined fields. A chance for SPS researchers to take advantage of other research projects is the space station. A concept of central facility to accommodate several experiments can be used for the SPS project. Another example is the international geophysical observations which are multidisciplinary and most valuable for environmental study. It is important to organize a small multidisciplinary study group to promote this project. Evolution of jobs of individual disciplinary study through the project life has been briefly surveyed. 1. INTRODUCTION It has been recognized that the Solar Power Satellite (SPS) system is so large that it can be realized only by multinational cooperation (1). For the same reason, multidisciplinary research is essential from the beginning of the study. It is difficult to organize a formal international multidisciplinary team at the present stage when the project is not authorized. On the other hand, there are many problems to be surveyed by such a team prior to authorization of the project. Thus, the situation resembles the endless question, which should come first, the chicken or the egg? This paper discusses the possibility for some existing research projects to play an important role in the early SPS study and evolution of work throughout SPS research and development. 2. UNIQUENESS OF SPS SYSTEM CONFIGURATION A conventional electrical powerplant using fossil or nuclear fuels is constructed in an integrated system in which it is considered that all the problems should be technically solved enclosed in a system at reasonable expenses. Recently, with increase of the power level per unit and the number of units as well, harmful effects of the system output have become significant. Thus the environmental issue is a factor in determining the value of an energy system. The situation of a conventional type of *Presented at the 34th Congress of the International Astronautical Federation, Budapest, Hungary, 10-15 October 1983.
energy system is schematically shown by Fig. 1. It should be noted that the dotted line interface was added after the power plant had been developed and had begun operation. On the other hand, the SPS system being proposed will be composed of two major system elements which will be deployed on the Earth’s surface and in outer space. The SPS system is exposed to the terrestrial environment, as the power is transmitted by radiation of electromagnetic waves, including light. Considering this feature, the SPS system is depicted by Fig. 2, to be compared with the conventional system in Fig. 1. In addition to physical characteristics of a complete SPS system, there are two important aspects of the SPS location. One is transportation of the SPS, and another one is the legal aspect of occupying the orbital position. Since these factors dominate in a certain phase of the SPS project, Fig. 2 contains these to show the overall system elements of the SPS project.
Environmental issues cannot be isolated from technical problems in this system. The problem is how to identify a real problem among interacting parts of the system with the environment, since any part of the system can be a potential environmental issue. The legal issue peculiar to the location of the SPS is international property of outer space and solar energy rights. This problem may have no solution with which everyone can agree, but will be gradually solved through practice by implementing a small scale project. Such a small project is necessary in order to define this problem. The economic aspect of SPS is difficult and complicated, because technical efforts to improve economical performance of the SPS system are not developed enough for identifiying major project elements including space transportation system (STS). Dr. Glaser pointed out the uniqueness of the DOE/NASA SPS conceptual study because these issues were studied prior to its existence (2). 3. NECESSITY OF MULTIDISCIPLINARY ACTIVITIES IN EARLY R&D PHASE The scientific principle of the SPS to convert solar energy to electrical power and transmit it to Earth is exhibited by many satellites. In this sense, SPS avoids the difficulties of nuclear fusion. This does not mean individual technologies are ready to give information required for SPS systems engineering. For such a large system, systems engineers in charge of integration of the systems and a system planner developing the total program will have many questions about interacting elements of the system. Most of such questions can be answered by specialists, since what the systems engineers and planners want to know is specific information. Actually the specialist can provide general knowledge on his speciality obtained from other experience, not knowing circumstances of the addressed question. Questions will be returned to the first questions. For example, if a specialist of structure design is questioned about the large structure to deploy solar cells, which is an important system element to determine the concept of other elements, he will request the following information. What are the constraints and requirements? What is the maximum acceptable mass? What are the conditions to determine the rigidity of the structure? What is the allowable deformation? How long is the life and how is the structure to be disposed of? Even if the area of concern is limited to just SPS, several typical problem areas can be listed besides this example. Technical problems are such as the life of a material to be used for structure elements of SPS, evaluation of disturbance of SPS motion to determine the attitude control system, electrical problem interaction between the SPS electrical system and environmental plasmas. Concerned environmental problems are rocket exhaust products, ionosphere heating and the local environment of a power receiving site. Research is required on both the microscopic mechanism of molecular and plasma behavior and the macroscopic dynamics of Earth’s atmosphere to decide the method to measure the change of climate allegedly to be caused by the long-term effect of radiation from the SPS. 4. PRACTICAL APPROACH TO COOPERATION OF MULTIDISCIPLINARY RESEARCH ACTIVITIES Many discussions on concepts of SPS can be made by specialists of many disciplines, and it is found that experimental research is essential to answer questions
concerning the above-listed problem areas, because these are key issues of the concept and are not answered by present knowledge. Since there is no strong justification at present for establishing a dedicated organization to conduct the systematic experimental research on SPS, such studies should be linked with other research projects conducted by existing research organizations. There are two important opportunities for this attempt. Space Station Many experiments will be carried out on the Space Station, taking advantage of the increased capacity of the electrical power supply, flight period and sophisticated orbital maneuvering such as the formation flight of multiple flight facilities. Experiments to use a common facility can be linked by a project. The experimental facility proposed as Space Energetics and Environments Laboratory (SEEL) has been planned in this direction (3). The experiments to be conducted with the SEEL are as follows. Space Plasma Experiment. This is supposed to be an extension of SEPAC, a payload for Spacelab one mission, to perform active space experiments. The objective of this experiment is to study the interaction of particle beam and atmosphere and plasma wave propagation, relating to ionosphere and magnetosphere research. Spacecraft charging and neutralization can be studied in the context of this experiment. Advanced Propulsion Test. The usefulness of electric propulsion has been verified by test operations of the attitude control system of several satellite missions. The next step is to apply a larger type of test operation to a main propulsion system. The Space Station will provide a more inexpensive test for this than a ground test facility. Space Radar. This is an experiment to study the feasibility of adopting an onboard traffic radar system to detect an artificial satellite colliding with the Space Station. The requirement of a high power transmitter features this experiment. Microwave Transmission Test. This is an updated version of the MINIX which is a Japanese sounding rocket experiment. The scientific objectives are a transmission test, measurement of the heating of a simulated ionosphere and perturbation of the atmosphere and ionosphere by microwave. Thus, this experiment is most closely related to an environmental issue of the SPS. 2-Dimensionally Deployable Solar Array. This is an experiment to deploy a unique deployment mechanism which can be applied for various purposes. The deployment test cannot be conducted on the ground. Space Laser. This experiment is not well defined except that it will test a laser utilizing excitation by solar light. Although this is proposed as a purely technological test of the laser, varieties of application are conceivable. These experiments have been linked by a core facility of free-flyer type of high power generator with a solar panel which is as large as the space station project could provide. In this case the solar power plant is designed to meet the requirements of each experiment and the investigators will conduct individually disciplined studies. Still, on the whole, these experiments address the fundamental problems of the SPS.
It is most important for key members of this project to recognize the importance of SPS and its basic problems. International Geophysical Year Importance of the environmental issue of the SPS was pointed out at the same time that it was proposed. The SPS is the first energy system for which the environmental effect has been assessed prior to the start of its development (2). Concerns prevail about the effect of energy dissipation into the atmosphere due to energy transmission by radiation on the climate change of Earth. Actually consumption of the conventional energy will have a similar effect on Earth. For example, increase of carbon dioxide in the atmosphere and floating dust of the combustion product which is produced not only by electrical powerplants but also by automobiles and other facilities consuming fossil fuels is observed. Thus, to know what the Earth environment is in the scale of a planet and how it is changing has the same importance as to know the effect of rocket exhaust products, dissipation of transmitted energy in the atmosphere and other sources of pollution supposed to be caused by the SPS, because the latter will be evaluated by reference to the former. The former activities are represented by the International Geographic Year research, which is typical multidisciplinary research. It should be emphasized that such scientific enterprise should be undertaken in the near future and special consideration is required to determine the global environmental condition on that occasion. 5. EVOLUTION OF JOBS OF MAJOR DISCIPLINES Multidisciplinary research activities are important during the whole project, because R&D activities will be required from the beginning through operations of the early operational model. Cooperation of multidisciplinary research activities involves different combinations of jobs. The type of jobs of disciplined area differs with progress of the SPS project and the sequence of jobs are different for individual areas. An approach to make such a job plan will be discussed here. To handle the macro-project of SPS more easily, an idea of macro-phasing was proposed to divide the SPS project into three phases as depicted by Fig. 3, where each phase is featured by a main experimental facility (4). Macro-phase I. The main facility of this phase is the Space Station and one concept has been presented here. The central facility is considered to be experimental equipment of SPS which will provide technical data for the future system design. The experimental operations will include experiments of technologies to be used for SPS and the receiving facility. The electrical propulsion test is directly related to the orbital space transportation of the SPS. Environmental study of this phase will be basic data collection required for experimental study of the next phase. Macro-phase 2. It is assumed that, in this phase, an intermediate scale model between the space station and the 1 GW operational model will be constructed and test- operated. According to a preliminary study (4), the experimental study is possible for such disciplined areas as the SPS system design, long period heating of the ionosphere, operation of power receiving station, Earth-to-low Earth orbit transportation operation and electrical propulsion system operation. Critical hardware for the SPS and the receiving station facility will be developed for the operational model of the
SPS. Economical study will develop the cost models including key parameters being tested. Macro-phase 3. This is the development phase of the overall SPS system. Key technologies are supposed to have been developed and few candidates recommended for the operational system are used for this model. Main experiments of this model will be concerned with recommended solution of the environmental issue which is
expected to be verified by the end of this phase, and test operation to verify the cost model and provide data for the economical analysis. These job evolutions are summarized in Table 1. CONCLUSION (1) The SPS is such a large and complicated system that intensive research in the many disciplined areas are required for research and development of the SPS. (2) At an early stage of the SPS project, research and development works should be started before a multidisciplined SPS project is authorized. If an existing research project is managed properly, it can produce as much data as a dedicated project. The Space Station and the International Geophysical Year research are typical enterprises that incorporate SPS study. (3) It is important that an SPS-minded multidisciplinary research group should be involved in the center of such a research project in cooperation with individual specialists. (4) Multidisciplinary research will be necessary throughout the project phases. The job plan of disciplined research should be to identify task areas of the whole project. REFERENCES 1. U.S. Congress Office of Technology Assessment, Solar Power Satellite (summary), Aug. 1981. 2. P.E. Glaser, Solar Power Satellite—What, How, and When? Space Solar Power Review 1, 245-246, 1980. 3. K. Kuriki, M. Nagatomo, H. Okuda, and T. Yamanaka, Japanese Free-Flying Satellite, presented at the 34th Congress of the International Astronautical Federation, Budapest, Hungary, 10^15 October 1983, paper No. IAF-83-31. 4. M. Nagatomo, Space Station: An Early Experimental Solar Power Satellite, presented at UNISPACE ’82, Energy from Space Symposium, 1982, Space Solar Power Review, 4, 143-154, 1983.
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0191-9067/85 $3.00 + .00 Copyright ® 1985 SUN SAT Energy Council THE EFFECT OF MICROWAVE RADIATION (2.45 GHz CW) ON THE MOLT OF HOUSE FINCHES (CARPODACUS MEXICANUS) FRED E. WASSERMAN Department of Biology Boston University Boston, MA 02215, USA TREVOR LLOYD-EVANS Manomet Bird Observatory Manomet, MA 02345, USA SAM P. BATTISTA Arthur D. Little, Inc. 30 Memorial Drive Cambridge, MA 02142, USA DAVID BYMAN Penn State University Worthington Scranton Campus 120 Ridgeview Drive Dunmore, PA 18512, USA THOMAS H. KUNZ Department of Biology Boston University Boston, MA 02215, USA Abstract — Molt, the cyclical replacement of feathers, is essential to mating and the adaptation of birds to a variety of environmental changes. All house finches (Carpodacus mexicanus) molted successfully after continuous exposure to microwaves for up to 18 weeks at power densities of 1, 10 and 23 mW/cm2. An analysis of the time required for the last half (5(>%) of molt revealed that the mean difference between control (5 birds) and 10 mW/cm2 (9 birds) exposed animals was not statistically significant. The time for the last half of molt for the 25 mW/cm2 exposed animals (2 birds) was estimated to be 103 to 108 days as compared to 60 days for the controls. Gross and microscopic examination of house finches continuously exposed to 25 mW/cm2 for up to 18 weeks revealed no gross or histopathology. Each of six birds was observed for changes in muscle tone, righting reflex, vestibular function, pupillary (light) reflex, and corneal and lip pain reflexes. The necropsy was carried out with special emphasis placed on tissues that reportedly are most sensitive to microwaves (i.e., eye, bone marrow, blood, gonads, brain, thymus, and adrenals). INTRODUCTION The Satellite Power System (SPS) has great potential for providing electrical power; however, it has not been determined whether it would cause deleterious environmental effects. The receiving antenna (rectenna) is estimated to cover 100 km2 with the microwave field within the rectenna area ranging from 0.1 mW/cm2 to 23 mW/cm2
and this large area will be virtually impossible to close off to airborne biota. The average body size of many common avian species (5 cm in length) suggests that these animals would have a maximum microwave absorption efficiency of 2.45 GHz and the rate of energy absorption could double or triple due to resonance (1). Molt was chosen as a sensitive indicator of the possible deleterious effects of microwave irradiation on the endocrine and autonomic nervous systems of birds. Molt is a complex mechanism of cyclic (often annual) ecdysis and endysis of feathers. The timing of molt is related to the seasons of breeding and migration: according to Thomson (2), “the cyclical occurrence of molt is determined by intrinsic (physiological) factors in which the thyroid and hypothalmic-pituitary-gonadal systems are principally concerned, activated also by extrinsic (physical) influences. Of the latter, day length appears to be the most important, but temperature also contributes.” Molt is genetically controlled within a given species or larger taxonomic grouping and normally falls into a rigid time frame. Molt begins a fixed number of days after the breeding activity (for adults) or fledging (for juveniles). It usually ends before fat deposition and fall migration or before winter fat deposition in northern non- migratory species (3). A significant interruption or retardation of molt induced by exposure to microwave fields could have a detrimental effect on the bird’s survival. A delay or failure to molt flight feathers (which is triggered to a great extent by day length) could result in an inability of the bird to participate successfully in long migratory flights. Similarly, non-migrant species without a normal molt would be less well equipped to cope with cold weather during northern winters. Another adaptable factor in avian survival is the loss of brightly colored plumage via the adult postnuptial molt which produces a more cryptic non-breeding plumage that is less obvious to predators. Molt, therefore, is a critical factor affecting a bird’s ability to adapt to its environment and thus serves as a sensitive indicator of altered physiology. It is reasonable to postulate that the proposed rectenna configuration would not provide suitable sites for bird’s nests or roosts above or among the active rectenna elements, i.e., in areas subject to field strengths of greater than 1 mW/cm2. These locations would lack shelter from climatic extremes and airborne predators. We expect that nesting or roosting will more likely occur beneath the active elements, or within and among the support and alignment structures and that only birds in flight over the rectenna would be exposed to power densities greater than 1.0 mW/cm2. Unless faced with strong headwinds, birds flying at 30 km/h should not be exposed to power densities greater than 1.0 mW/cm2 for more than 30 min. Therefore, molting house finches (Carpodacus mexicanus) were initially studied to answer the following question; will microwave exposures alter molting of birds that are exposed while nesting in areas immediately adjacent to the proposed rectenna site? METHODS Exposure Facilities and Microwave Generating Equipment The microwave irradiation facilities were designed to provide planwave illumination with a power density variation of ± 0.5 dB maximum over the cages. The radiating source was a Narda #645 standard-gain horn which provided lineraly polarized radiation. It was a precision cast, one-piece unit which shows great uni-
formity in performance over a production lot. The on-axis gain of this horn at 2.45 GHz was 14.57 dB relative to an isotropic radiator, and use of the universal response curves for sectoral horns (4) indicated that the Narda #645 would provided power uniformity within ± 0.5 dB over a region that lies within 7 degress of the axis. Homs were positioned for overhead illumination and yielded a power density variation of ± 1 dB over a floor space of 1.2 x 1.8 m (Fig. 1). A divided platform was used for the support of cages. Each half was covered with anechoic material and the bottom platform fitted with casters so that the entire assembly containing the cages could be rolled out from opposite sides of the exposure chamber. Lighting was separately provided to each half of the platform so that day/night periods could be independently adjusted.
Five replicates of this irradiation chamber were built. Three chambers were operated at 0.1, 1.0 and 10.0 mW/cm2, respectively, from one Cober S6F generator, using topwall couplers of 20 dB and 10 dB for the horn feeds to the first two chambers and a direct waveguide feed to the horn in the third chamber. The two remaining irradiation chambers were energized by a dedicated Cober S6F generator. One of these operated at 25 or 50 mW/cm2 for subchronic exposure studies while the other was used in studies involving acute exposures in conjunction with a wind tunnel. Molt in House Finches Following its introduction to the Northeastern United States in 1940 (5), the house finch has become a year-round resident. The adult prebasic molt is complete and typical of resident passerines (6). In southeastern Massachusetts, the resident, non-migrant house finches have one complete molt between the end of June and December. Adult birds with worn plumage and brood patches (females) or cloacal protruberances (males) were trapped before the onset of prebasic molt with the exception of five birds which had just started to molt. Trapping sites were Chatham, Plymouth, and Rockport, Massachusetts. Individually numbered plastic legbands were applied to each bird. The finches were housed in rectangular microwave transparent cages 1 x 1 x 0.5 m that were divided into four separate cells, each containing one or two birds. Cages were placed in either microwave exposure chambers or in control chambers. Initial experiments concentrated on differentiating responses between the control and 10 mW/cm2 exposure groups in order to provide data of highest relevance to the SPS system. The sample sizes of birds could not be increased beyond ten animals because most of the space in the chamber was already committed to other experiments. These reasons and our inability to obtain adequate numbers of birds at the critical time (before onset of molt) precluded conducting experiments at 0.1 mW/cm2 and reduced the number of birds available for exposure to levels of 1 mW/cm2. We proposed initially to expose representative numbers of birds to 25 mW/cm2 until two problems were encountered. Firstly, there was a delay in completion of the 25 mW/cm2 chamber. Waiting until the chamber was completed would have meant missing the first week or two of molt at the end of June and early July. Secondly, in early July, house finches placed in a nonfunctioning exposure chamber exhibited gaping behavior from hypothermia within an hour when ambient temperatures were greater than 30°C. Additionally, there was small likelihood of birds being exposed to 25 mW/cm2 on a continuous basis at a rectenna site. For these reasons, we chose to use 10 mW/cm2 exposures for the major sample and delayed the 25 mW/cm2 exposures until later in the season (4 September) when ambient temperatures are lower. At this time, two birds that had already started molting were included in the 25 mW/cm2 experiment. The birds were exposed continuously, except for times of cage maintenance, e.g., cleaning, feeding, water replacement, for a period ranging between 110 and 150 days. Artificial lighting was controlled to simulate day length. A balanced diet of water, seeds, fresh fruit, vegetables and mealworms was given daily, perches were provided and cages were cleaned daily. The ambient or room temperature where the controls were kept typically ranged between 21 and 32 °C during a mid-summer day in 1980, between 20 and 24°C during the fall, and was held at 10°C during November and December. All birds acclimated satisfactorily and, with one exception, survived to completion of the experiment.
The following data were collected for each bird every 7 to 13 days from 30 June to 5 December 1980. 1. Band number 2. Cage and cell number 3. Microwave exposure (and date of commencement) 4. Card number 5. Data 6. Sex (7) 7. Cloacal protuberance or brood patch development (as indications of breeding condition, see Svensson (8), Salvadori and Youngstrom (9)). 8. Total Molt Scoring. The molt card is based on the one used by the British Trust for Ornithology, see Snow (10). Snow’s numbering, sequences, and definitions are used. Following the standard “molt score” system used by Evans (11), old remiges and rectrices were scored zero; one for feathers absent or in pin; two, three, and four for various stages of growth; and five for complete new feathers. The scoring system used ranged from a minimum score of zero (no feather loss) to a maximum score of 240 (full or total molt) as shown below: • primaries 90 (18 major feathers x 5) • Secondaries 60 (12 major feathers x 5) • Tertails 30 (6 major feathers x 5) • Tails 60 (12 major feathers X 5) Total Maximum Score 240 The score from the feathers of the bird’s right side was multiplied by 2 to produce the total molt score for that bird, as it was assumed that the normal course of molt was symmetrical (10). The total scores from periodic observations were plotted against data to indicate speed and timing of molt (12,13). 9. Flight feather length measurements. The feathers chosen are (with a few exceptions due to wear or accidental loss) the left side primaries (PP) numbers 1, 4, 9; secondaries (SS) 1, 4; tertial (TT) 7; tail (TL) 1 and 6. The old unmolted feathers were measured once from the base to tip with a dial vernier calipers to 0.1 mm. Feather loss was noted and all growing feathers measured periodically until completion of growth. Variability of length of old feathers may be introduced by normal wear, especially on the tail and perhaps primary 9. On the first observation, birds were observed for any abnormalities and conventional measurements were taken of tail length, including flat and chord lengths of wings from carpal joint to the tip of the longest primary. Results and Discussion In reviewing data for molt of flight feathers, several confounding factors were evident. Individual birds began and ended molting at different times and some birds had already started to molt when they were included in the experiment. It was also evident that data for the end of molting were more complete and, therefore, might be more useful as a common point of reference with which to combine molting of different birds within and among treatments. In those instances where molting was not complete (score of 240) at the last observation, the scores for
the five previous observations were plotted against the corresponding observation time, and the curve extrapolated to where it intercepted the score of 240. This point was assigned a value of zero to represent the best estimate of the complete regrowth of the 48 indicator feathers or a score of 240. Scores obtained at each measurement for each bird were then plotted beginning at zero and continuing back to the beginning of molt. Thus, days to completion of molt is plotted against the corresponding molt score. Since the times for each observation were different, the scores at 10 day intervals were obtained for each bird and the curves plotted. The time required for each bird to achieve the last half of its molt was also determined. Controls The individual curves for regrowth of flight feathers on five unexposed (control) birds are shown in Fig. 2. It can be seen that the shape of the molt curve for flight feathers is sigmoid and that molting requires approximately 115 to 150 days. From each of the curves plotted in Fig. 2, the time required for each bird to achieve the last half of its molt (score of 120 to 240) was noted and the mean ± standard deviation, 59.6 ± 5.8 days, computed.
Data for individual birds exposed to 10 mW/cm2 are plotted in Fig. 3. Based on values obtained from individual curves the mean and standard deviation for the last half of molting for 10 mW/cm2 exposed birds is estimated to be 62.1 ± 7.3 days with full molting requiring 110 to 150 days. Two birds were exposed to microwave irradiation at 1 and 25 mW/cm2, respectively. One of two birds exposed to 1 mW/cm2 (Fig. 4) and both exposed to 25 mW/cm2 (Fig. 4) were already molting at the time they were included in the experiment. While the shape of the curves for both birds at 1 mW/cm2 resembled those (sigmoid) obtained for the controls and 10 mW/cm2, the curves for the two 25 mW exposed birds were markedly different, indicating microwave radiation may have delayed molting. Although there were too few birds at 25 mW/cm2 for conclusive evidence, there is no indication of altered molting for the 1 and 10 mW/cm2 exposed birds when compared to the controls (Fig. 5). An analysis of the time required for the last half (50%) of molt revealed that the mean difference between control and 10 mW/cm2 exposed birds using a t-test was about 2 days and was not statistically signfiicant (p>0.05) whereas the time for the last half of molt for the 25 mW/cm2 was
estimated to be 103 to 108 days as compared to 60 days for the controls. Although both birds at 25 mW/cm2 completed their molting process, the question as to whether the slower rate of molting was due to microwaves or the change in environment during molting (birds had already started to molt when captured) remains unresolved. Effects of Microwaves on Length of New Feathers In addition to using the system of scoring changes in growth of flight feathers, measurements of the length of individual feathers at the end of molt was carried out for the controls and 10 mW/cm2 exposed birds. A decrease in length of the original feathers compared to new feathers was expected due to normal wear of the feathers since the last molt. Table 1 contains the ratios of the length of original and new feathers of selected indicator feathers. There was no significant effect of microwaves on the length of new feathers compared to the original feathers lost during molt. In general, the original feathers of the birds exposed to 10 mW/cm2 were longer than their new feathers, while the reverse was true for the controls. It is unlikely that this very small difference in feather length will influence flight and survival of the birds and, therefore, should not be considered of biological consequence.
Gross and Microscopic Examination of House Finches Irradiated Continuously To determine whether continuous exposure to microwave irradiation of birds to 10 and 25 mW/cm2 causes organ damage, twelve exposed and six control birds (0 mW/cm2) initially were examined grossly at Arthur D. Little and then sent to Dr. S.W. Nielson, DVM, Ph.D. at the University of Connecticut for necropsy and histopathologic examination. An examination of the treated and control birds revealed no detectable effects in overt behavior or in selected visceral and somatic reflexes caused by microwave irradiation. Each bird was examined for changes in muscle tone, righting reflex, vestibular function, pupillary (light) reflex, and corneal and lip pain reflexes. The cornea and lens were also examined with an ophthalmoscope for evidence of opacity and retina damage, e.g., changes in color. A necropsy was performed first on the six birds continuously irradiated with microwaves at a level of 25 mW/cm2 along with six control birds. In the event pathology was observed on either gross or histopathology, the intent was to necropsy the six birds exposed to the 10 mW/cm2. The necropsy was conducted with special emphasis placed on tissues that reportedly are most sensitive to microwaves (i.e., eye, bone marrow, blood, gonads, brain, thymus, and adrenals). Since no gross or histopathology was found at the 25 mW/cm2 level, the six birds at lower dose or 10 mW/cm2 were not necropsied. In summary, these results fail to show any gross or microscopic pathology attributable to microwave irradiation of birds as might be encountered at a rectenna site at levels proposed for SPS system. Acknowledgements — This research was supported by a contract from the U.S. Environmental Protection Agency (No. 68-02-3278) to Arthur D. Little, Inc. and subcontracts to Boston University (No. A-11038) and Manomet Bird Observatory (No. A-11040). Although the research described in this article has been funded wholly by the United States Environmental Protection Agency, it does not necessarily reflect the views of the Agency and no official endorsement should be inferred. For help of various kinds we thank Edward Cook, Russ Smallman, and Ken Youngstrom. REFERENCES 1. C.H. Dumey, C.C. Johson, P.W. Barber, M.F. Iskander, J.L. Lords, D.K. Ryser, S.J. Allen, and J.C. Mitchell, Radiofrequency Radiation Dosimetry Handbook, Ed. 2, Report SAM-TR-78-22, Brooks Air Froce Base, Texas: USAF School of Aerospace Medicine Aerospace Medical Division (AFSC), 1978. 2. A.L. Thompson, A New Dictionary of Birds, Thomas Nelson, London, 1964. 3. E. Stresemann, Die Mauser der Vogel, J. Ornith., 107, 118-169, 1966. 4. H. Jasik, Antenna Engineering Handbook, McGraw Hill Book Company, New York, 1961. 5. L. Griscom and D.E. Snyder, The Birds of Massachusetts, Peabody Museum, Salem, MA, 1955. 6. J. Dwight, The Sequence of Plumages and Moults of the Passerine Birds of New York, Ann. New York Acad. Sci., 13, #73-360, 1900. 7. M. W. Wood, A Bird-Banders Guide to Determination of Age and Sex of Selected Species, College of Agriculture, Pennsylvania State University, University Park, PA, 1969. 8. L. Svensson, Identification guide to European passerines, Naturhistorika Riksmuseet, Stockholm, Sweden, 1970. 9. A. Salvadori and K.A. Youngstrom, A System Survey of a Bird Observatory, 1973. Part I: A Recording Form for Banding Data. Bird-Banding, 14, 10-24, 1973. 10. D.W. Snow, A Guide to Moult in British Birds, British Trust for Ornithology Field Guide No. 11, 1967. 11. P.R. Evans, Autumn Movements, Moult and Measurements of the Lesser Redpoll (Carduelis flammea cabaret), Ibis, 108, 183-216, 1966. 12. I. Newton, Feather Growth and Moult in some Captive Finches, Bird Study, 14, #10-24, 1967. 13. D.W. Snow, The Moult of British Thrushes and Chats, Bird Study, 14, 16, 115-129, 1969.
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