Space Power Resources, Manufacturing and Development Volume 12 Numbers 3 & 4 1993
SPACE POWER Published under the auspices of the Council for Economic and Social Studies on behalf of the SUNSAT Energy Council. Editors: Dr. Gay E. Canough, ETM Solar Works and Dr. Andrew Hall Cutler, NASA Space Engineering Center, The University of Arizona Associate Editors: Fred Koomanoff, Dept, of Energy, USA Richard Boudreault, Consultant, Montreal, Canada Lars Broman, SERC, Sweden William C. Brown, Massachusetts, USA Lucien Deschamps, Paris, France Ben Finney, U of Hawaii, USA Peter Glaser, Aurther D. Little, Inc. USA Dieter Kassing, ESTEC, The Netherlands Mikhail Ya. Marov, U of North Carolina, USA Gregg Maryniak, International Space Power Program, USA Makoto Nagatomo, ISAS, Japan Mark Nelson, Institute of Ecotechnics, USA John R. Page, U of New South Wales, Australia Tanya Sienko, NASDA, Tsukuba, Japan Space Power is a quarterly, international journal for the presentation, discussion and analysis of advanced concepts, initial treatments and ground-breaking basic research on the technical, economic and societal aspects of: large-scale space-based solar power, space resources utilization, space manufacturing, space colonization, and other areas related to the development and use of space for the benefit of humanity. Recent subject coverage: • history and status of national space power programs • technologies for large-scale space power e.g. solar power satellites • systems aspects of large-scale power, e g. SPS and central space power utilities • potential extraterrestrial resources for use in space-based manufacturing • lunar and planetary science for understanding space resource location and availability • plasma and other space environment interactions with large space structures • medical, psychological, sociological and cultural aspects of human presence in space • forms of advanced space propulsion and power technologies and systems. Space Power is published four times per year. These four issues constitute one volume. An annual index and titlepage is bound in the December issue. 1993 is volume 12 ISSN = 0883-6272 Editorial Correspondence: Dr. Gay E. Canough, Space Power c/o ETM Solar Works, Inc., PO Box 67, Endicott, NY 13761, phone/fax = (607) 785-6499 e-mail (Internet): CANOUGH@BINGVAXA.CC.BINGHAMTON.EDU radio call sign: KB2OXA. Business Correspondence including orders, subscriptions, advertisements, back issues and off prints should be addressed to the publisher: Council for Economic and Social Studies, 1133 13th NW, Washington DC 20005, 202 371 2700, fax 1523 Subscriptions: libraries: $288/year, individuals: $155/yr., additional $25 for airmail Cover: An artist's conception of a solar power satellite constructed of lunar materials, on station over the Earth's equator. Reproduced by courtesy of Charles L. Owen, Institute of Design, Illinois Institute of Technology, 10 W. 35th St. Chicago IL 60616.
Multi-component Liquid Metal Coolants with Regulated Properties for Space Nuclear Reactors in a Large Orbital Station D.N.KAGAN* SUMMARY The method of experimental investigation of thermodynamic functions of multi-component liquid-metal systems on the basis of alkali and alkali earth metals is proposed and realized. Being both high temperature and low temperature coolants simultaneously, these systems can be used for nuclear and solar power installations in space. Introduction These systems are the basis of the new kind of coolants and working fluids for energetics and technology. The method is based on calculation of characteristic functions (potentials) in the broad area of temperatures and concentration by integration of differential equations of chemical thermodynamics with experimental determination of: 1) under integral functions (partial and integral enthalpies of formation in all areas of named parameters of state) 2) boundary conditions (concentration dependencies of activities or Gibbs energies at one (not high) reference temperature T j = 400 K ). The advantages of this algorithm, which can be provided with reliable input experimental data and permits one to obtain an internally consistent thermodynamic description of the studied systems, are demonstrated. For solution of both experimental tasks, two groups of installations were constructed. The first group includes a complex of calorimetric apparatae with a level of sensitivity permitting the determination of the integral and partial enthalpies of formation of liquid-metal systems. The second group is based on determination of the activities of the components via partial pressure of the saturated vapor obtained by measurement of the intensity of their atomic flows. The data for the thermodynamic functions in the range 0 < Xj < 1 and 200 < T < 1500 K are obtained. All the data at high and extremely low temperatures were absent in literature. Physical interpretation of results are submitted. * Institute for High T emperatures of the Russian Academy of Sciences IVTAN, Izhorskaya, 13/19, Moscow, 127412, Russia
Nomenclature The power plant of a large orbital station consists of a fast neutron nuclear reactor, built-in thermo-electric generator and a cooling system. The latter contains a main loop with liquid-metal high temperature coolant which, in turn, is cooled with help of a bundle of high temperature liquid metal heat pipes. For the initial fast preheating of the cooling system (after it has been cold) there is a special loop filled by low-melting liquid-metal coolant. This coolant (a three component eutectic of system Na-K-Cs) is a universal one and is suitable not only for nuclear reactors but also for solar power sources. Binary and ternary systems of alkali and alkali-earth metals as coolants have the advantage of pure components and the additional merits: • possibility of regulation of thermo, electro and nuclear , physical properties by varying the component fractions, • maximum wide range of working temperatures of the liquid phase being both high- temperature and low-temperature coolants simultaneously , • maximum effectiveness all over this range concerning heat exchange, heat storage, and mass characteristics. For example, by regulating the fractions (of metals), compositions corresponding to special points of phase diagrams which have extraordinarily low temperature of crystallization (T = 200 K), can be obtained This temperature is the minimum one for all the metal liquids known in the world, and the coolant remains in the liquid state at any earth temperature and for most real conditions on a large orbital station. The
purpose of the study was to obtain the correct thermodynamic description of binary and ternary liquid-metal systems as a basis for coolants of the new kind with regulated properties for power generation and technology in the range of compositions and temperatures 0 < Xj < 1 and 200 < T < 1500 K. This means building the set of characteristic functions (potentials) which in coordinates P,T,Xj are Gibbs energies of formation of the systems (partial and integral functions, absolute and excessive values) and thus the activities and coefficients of activity of components AG;, AG, AGi, AG , aj, Yj. Then all the derivatives i.e. the rest thermodynamic functions which are enthalpy and entropy of formation, excessive heat capacity, &H-, AH, AS, , AS, AS/, AS and ACp can be obtained. Direct measurement of the change in the partial Gibbs energy of the components at formation of the liquid-metal alloy in this broad temperature range, using the EMF method [1-4], is extraordinarily difficult because of the absence of steady high- temperature solid electrolytes with the necessary ionic composition for use as membranes in concentration cells. Determination of partial pressure and activity of the components via an experimental study of absorption spectra by the atomic absorption method [5,6] is limited to a small range of temperatures because of the influence of the radiation contribution to corresponding lines. Effusion methods at high temperatures, with either optical or mass spectroscopic or chemical methods of determining of flow composition, are not suitable for alkali- metal systems because of high saturation pressures and technical difficulties of operating with high intensity atomic flows of alkali metals coming out of the apparatus. Method Instead of direct measurement of the Gibbs energy of alloy formation, AG;, or activity of components, aj, at high temperature the following methods are described: • experimental determination of the temperature and concentration dependencies of enthalpy of formation (heat of mixing) AH, A/7Z in the required range of parameters: AH, AH, = f(xj, T), that is easier and can be fulfilled with hermetic working cells • experimental determination of the activity of components aj or the partial Gibbs energy AGZ at a certain (not high) reference temperature T j= 400K: aj = f(xj ,T const) or AG, = f(xj, Tj= const) Solving the differential equation of chemical thermodynamics of the type ,
The solutions of these equations are of the following kind: The proposed scheme does not require any special assumptions, can be provided with reliable experimental input data and as a result permit us to obtain internally consistent thermodynamic description of the systems under study. Experimental Two types of measurements were carried out: 1) determining the caloric properties of liquid-metal systems (enthalpy of formation, heat capacity, heats of phase transitions) in the range of concentrations and temperatures using a few adiabatic reaction calorimeters of several types for systems with a number of components from 2 to 4 [7,8], 2) determining the thermodynamic activity or partial Gibbs energy in the range of concentrations at one non-high reference temperature (Tj = const. ~ 400K) by effusion method (modified Knudsen method) on partial pressure of saturation vapor components obtained by measurement of intensity their atomic flows (the effusion orifice was made with a calibrated electron-beam pulse generated directly in vacuum
chamber of the apparatus when the hermetic effusion cell has reached the required working temperature) [9] Results The enthalpy of formation at all the concentrations and temperatures and the activity of components at all the concentrations and one temperature (Tj= 400K.) were measured. Then in accordance with the described method by solving of equation (3) or (4) the activity (and Gibbs energy) at all the concentrations and temperatures were calculated and the rest thermodynamic functions were obtained with help of standard relations:
The data for binary and ternary systems Cs-Na, K-Na, Cs-K, Cs-K-Na, Ba-Cs, Be-Ba, Be-Sr, Be-Ca, Be-Mg, Ca-Sr, Ca-Ba. Sr-Ba, Mg-Ba, Mg-Ca and so Cs-F and Lili (lithium hydride) were obtained with the above parameters [8,9,11], The functions for binary alkali-metal systems from liquidus line up to 1200K are demonstrated on Figure l(a,b,c) Discussion Model theories were used for the interpretation of the experimental data and were the basis of their adequate approximation. For the enthalpy of formation ,a quasichemical model was proposed by Guggenheim[10], Developed for these liquid-metal alloys [11] it takes into account the alteration of short-range order structure compared to the random distribution, as well as the concentration and temperature dependencies of the energies of all kinds of pair-wise inter-particle interactions (e.g. three kinds for binary systems). For the entropy of formation (obtained from the difference between experimental values of the enthalpy of formation and the Gibbs energy of formation) the hard-sphere model with a little dependence of hard-sphere diameters on concentration [12 ] as fitting parameter of theory can be used. The long-wave limit of the concentration correlation function was computed for the range of temperatures and concentrations with help of obtained thermodynamic data (for binary systems of alkali metals up to 1200K see Figure 2). These results were compared with available data from the literature (T=400 K) for diffraction experiments (Scc(0) is obtained via the static structure factor S(0)) [14,15 ], as well for some thermodynamic experiments [1-6] and calculations [4,12], There was agreement concerning the magnitude and coordinate of the maximum of the function: It corroborates the existence of long-range fluctuations of concentration in some liquid-metal systems, i.e. micro-non-homogeneous (cluster) structure of the liquid alloy and therefore the decreasing of thermodynamic stability of the system as a homogeneous liquid phase. This fact correlates with phase diagrams, e.g. for the Cs-Na system liquidus line in the named concentration range is practically horizontal. This means that increasing concentration fluctuations show a tendency for phase stratification [3, 4]. Some peculiarities of behavior of the thermodynamic
functions are the change of sign of the excessive Gibbs energy of formation and the excessive entropy of formation. This phenomenon is analogous to the inversion of the compressibility factor for one-component liquids in the negative range of values of second virial coefficient. Corresponding to these results, mutual alloys of the metals studied are not only non-ideal solutions, but being real solutions, were in different thermodynamic classes depending on the temperature and size factor [11] .The analysis lead to the possibility of separate ranges of existence for each class and particularly to an explanation of the anomaly [16] of deviation from Roult's law which has been displayed in independent measurements of saturation pressure. The results on concentration and temperature dependencies of the short-range order parameter, energies of inter-particle interaction, and concentration correlation function : • explain the contraction of studied alloys [17], • explain the anomalies in acoustic [18] , electromagnetic [19] properties and NMR spectra [20] • display the correlation with phase diagrams and point towards understanding of the properties of some liquid-metal system properties. Acknowledgements The author wishes to express his gratitutde for support from the Russian Foundation for Basic Research (RFBR) under grant number 94-02-05512-a References [1] Lokshin,E.P., Ignatjev,O.C. Activities of components in Na-K, Na-Rb and Na-Cs alloys. Thermophysics of High Temperatures, 1971, v9, No.l, p.94, 1975, vl3, No.l, p.75. [2] Lantratov,M.F. Thermodynamic properties of liquid NaK alloys. Joum. Appl.Chem., 1973, No.7, p.1485. [3] Ichikawa,K., Granstaff,S.H., Thompson,J.C. Chemical potentials and related thermodynamics in liquid NaCs alloys. Joum.Chern.Phys., 1974, v61, No. 10, p.4059; 1973 ,v59, No.4, p. 1680; Joum.Phys.F, 1974, v4, No.l,p.L9 [4] Neale,F.E., Cusack,N.E. Thermodynamic properties of liquid NaCs alloys. Joum.Phys.F: Metal Physics,1982,vl2, No. 12, p.2839; Joum. of Noncristalline Solids, 1984, v 61/62, Parti, p.169 [5] Cafasso,F.A., Khanda,V.M., Feder,H.M. Thermodynamic properties and ordering in liquid Na-K alloys. Advances in Physics, 1967, vl6, No.63, p.535
[6] Ciurylo.J., Rozwadowski,M. Saturated vapour pressure of Cs over a KCs solution. Acta Phys.Pol., 1977, vA51, No.4, p.583 [7] Kagan,D.N. Adiabatic calorimetry. Compendium of Thermophysical Property- Measurement Methods. 1.Survey of Measurement Techniques (Maglic,K.D., Cezairliyan,A. ed.). N.Y.L., Plenum Press Publ., 1984. Chapter 12, p.461; Investigation of the Thermophysical Properties of Alkali Metals in the Condensed Phase. Soviet Techn.Rev.B: Therm. Phys. (Sheindlin,A.E., Fortov.V.E., ed.). N.Y.L., Harwood Acad. Publ. GmbH, 1987, vl. [8] Spilrain,E.E., Kagan,D.N., Uljanov, S.N. Thermodynamic functions of alkali earth metals. Surveys of Thermophysical Properties of Substances. Moscow, Publ. Thermophysical Center, 1986, v3(59) [9] Kagan, D.N. Measurement of activity of components in liquid alloys of alkaly metals by effusion method on electronbeam installation. Thermophysics of High Temperatures, 1988, v26, No.2, p. 360, No.3, p.478 [10] Guggenheim,E. A. Mixtures. Oxford, Oxford Univ. Press., 1952 [11] Kagan,D.N., Krechetova,G.A. Characteristics of interparticle interaction in liquid binary systems of alkaly metals, dependence on temperatures. Thermophysics of High Temperatures, 1981,vl9, No.2, p.432; 1980,vl8, No.4, p.880, No.3, p.501,639; Thermodynamic properties and characteristics of interparticle interaction of liquid binary systems of alkali metals. Surveys of Thermophysical Properties of Substances. Moscow, Publ. Thermophysical Center, 1980, v2(22). [12] Visser,E.G., Alblas,B.P., De Hosson,J.T., Van der Lugt,W. Thermodynamic calculations for the liquid systems Cs-Na, K-Na, Cs-K, Pb-Li. Joum. Phys.F: Met.Phys., 1980, vlO, No.8, p.1681; Physica, 1982, vll4B, No.l, p.59 [13] Bhatia,A.B., Thornton,D.E., Hargrove,W.H., March,N.H.,et al. Liquid Metals. Moscow, Metallurgy Publ., 1980; Motion of Atoms of Liquid. Moscow, Metallurgy Publ., 1980 [14] Huijben,M.J„ Alblas,B.P., Van der Lugt,W., et al. Structure properties of the liquid systems CsNa, KNa, CsK by Xray and neutron difraction experiments. Acta Cryst., 1979,vA35, p 431; Joum.Phys.F: Met.Phys. 1977,V7,p.L119; 1980,vlO, p.531; Physica, 1979,v97BC, p.338; 1981,vlO6B, p.2229; 1980,vl01B, p.177 [15] Henninger,E.H., Buschert,R.C., Heaton,L.R. Atomic structure and correlation in liquid binaries by Xray and neutron difraction with application to NaK. Joum.Chem.Phys., 1966, v44, No.5, p.1758 [16] Shkermontov,V.L, Shpilrain,E.E., Belova,A.M., Pokrasin,M.A., Roshupkin, V.V. Experimental study of saturation pressure of binary and ternary systems of liquid
metals. Thermophysics of High Temperatures, 1984, v22, No.l p.175; 1980, vl8, No.2, p.290; 1986, v24, No.2, p.244; 1988, v26, No.4, p.819 [17] Huijben,M.J., Alblas,B.P., Van der Lugt,W. Density dilatometric measurements of the liquid systems CsNa, K Na, CsK. Scripta Metallurgical 975,v9 p.653; 1976, vlO, p.571; Physica, 1981, vlO6B, p.22 [18]Kim.M.C., Letcher,S.V., Jarzynski, J., Litovitz,T.A. Ultrasonic velocity and adsorption in liquid of KRb, KNa, and NaCs mixtures. Joum.Chem.Phys., 1971, v55, p.1164; 1964, v41, p. 1290 [19] Tamaki,S., et al. Prop.Liq.Met. Proc. 2 Int.Conf.,1972. Tokyo, Halpsted Press, N.Y., 1973,p.289 [20]K.aeck,J.A. Electronspin in alkali alloys. Phys.Rev.,1968, vl75,p.897
Concept of a Lunar Energy Park MASAYUKI NIINO, KATSUTO KISARA, LIDONG CHEN* Summary: This paper presents a new concept for an energy supply system named Lunar Energy Park (LEP,) as one of the next-generation clean energy sourcse. In this concept, electricity is generated by nuclear power plants built on the Moon and then transmitted to receiving stations on the Earth by laser beam through transporting systems situated on geostationary orbit. The lunar nuclear power plants use a high- efftciency composite energy conversion system consisting of thermionic and thermoelectric generators to change nuclear thermal energy into electricity directly. The nuclear resources are considered to be available from the Moon and the nuclear fuel transport from Earth to Moon is not necessary. Because direct energy conversion systems are used, the lunar nuclear plants can be operated and controlled by robots and are maintenance-free, and so will give no pollution. The key technologies for LEP include improvements of conversion efficiency of both thermionic and thermoelectric converters, and developments of laser-beam power transmission technology. In this paper, the details on the lunar nuclear plant construction, energy conversion system, energy transmission system and the research plan strategies are reviewed. Background Contemporary civilization has developed with the help of the large amount of consumption of fossil fuels such as petroleum, natural gas and coal. It is estimated that fossil fuels, presently serving as the major source of energy, will be exhausted within about 50 years, if the demand for energy continues to grow at an increasing rate of 3% per year. On the other hand, these natural resources are used not only as energy sources, but also as important raw materials for the chemical industry. Accordingly, they have to be conserved as valuable resources of mankind. Furthermore when we turn to environmental problems, it is apparent that the increasing emission of carbon dioxide by fossil fuel combustion poses the serious problem of global warming. To cope with such difficult situation the resources depletion problem and the environmental problem, searching for alternative energy has been being widely examined in various aspects. As for nuclear energy, although it had been expected to become the mainstay of clean alternative energy, nuclear power generation has many difficult problems. Among them are the disposal of radioactive wastes, the obsolescence and renovation of nuclear power facilities, and, as a result the campaign for the total abolition of nuclear power in terms of securing safety, especially since the occurrence of nuclear accidents at Three Mile Island in the USA and Chernobyl in the former USSR. * Kakuda Research Center, National Aerospace Laboratory Koganezawa 1, Kimigaya, Kakuda City, Miyagi 981-15, Japan
Hydroelectric power is another clean alternative, but the number of river systems throughout the world suitable for large-capacity generation is limited. Moreover, construction of large dams to provide large amounts of electricity may cause new environmental destruction. Therefore, large-scale river developments including construction of hydroelectric plants will not be able to fill the blank in energy supply, which might occur in the near future. Nevertheless, any shortage of energy supply will not be allowed for contemporary civilization development. To cope with the energy problem affecting the global environment, utilization of solar energy is being widely studied. Unfortunately, for solar energy, its energy density is too low and its distribution is too wide, and thus its fullest utilization is at present unfeasible. It is estimated that it will take at least a few centuries to be able to fully utilize solar energy as a basic energy. Therefore, it is thought that solar energy will not meet the requirements of the times of energy supply shortage due to the depletion of fossil fuels, which may occur within 50 years at the earliest.
Let us look into another issue. It is the wish of all people to promote the progress of the peaceful use of science and technology, which will bring invaluable benefits to mankind. The recent world situation indicates that today is the most appropriate time for utilizing space for peaceful purposes. To date, space development has progressed largely for military purposes. However, now that space development for such purposes is being de-emphasized, the only way to promote space development and make it as a new technology field for peaceful purposes is to introduce economics into this field. In the interests of promoting science and technology for the progress of the utilization of nuclear energy and space development, we would like to propose a concept of lunar energy park (LEP) as a means to cope with future energy crises and global environmental problems. LEP will mainly consist of nuclear power plants constructed on the Moon, and a power transmission system to transfer energy produced there to the Earth through relay satellites in geostationary orbit, using lasers. The concept of LEP is shown in figure 1 and the details are described below. Lunar Energy Park The Moon has appropriate conditions for nuclear power generation, since it has rich nuclear resources and abundant raw materials for plant construction. In addition, since the Moon has no atmosphere and is exposed to powerful cosmic and radioactive rays, such problems as shielding as on the Earth do not arise. In nuclear power generation on the Earth, turbines and water are used. On the Moon, however, the lunar energy park will convert nuclear energy directly into electricity by means of a maintenance-free and highly reliable reactor incorporating innovative concepts. The LEP consists of such facilities as nuclear fuel supply plants, nuclear power generation facilities and power transmission facilities. The electricity produced from the Moon is transmitted to the energy relay satellites in geostationary orbit via laser beam of wavelength with high transmitting efficiency. Then, at the relay satellites it is converted to laser light of wavelength with characteristics of high transmission efficiency in air, which is then transmitted to energy-receiving stations located on isolated islands on the Earth. From the receiving stations, the energy is distributed to various districts. Nuclear Reactor The LEP reactor is a new type different from those on Earth. By reducing the nuclear energy output to an extremely low level through the low-reaction operation, the heat load (q) reaches a few W/cm^, approximately a hundredth that of a reactor on Earth, and maximum heating source temperature is maintained at about 2,000K. Power generation employs a direct energy conversion system consisting of thermionic/thermoelectric composite converters, which is shown in figure 2 The efficiency of such direct converters is expected to be greatly improved due to the FGM (Functionally Gradient Material) technology. [1] The conversion elements are directly wrapped on the nuclear fuel.
The nuclear reactor does not require forced cooling in principle, but employs a radiation cooling system. As a new type of nuclear reactor, we propose a 2-dimensional nuclear reactor, in which conversion elements are assembled in layers, forming the reactor structure by sandwiching layers with the heat source in the center, as schematically shown in figure 3. In this case, the nuclear reactor is formed with the structure having no moving parts. Each reactor plant is about 100 m x 100m in size, and generates one-million kilowatts of power. By installing a large number of these reactors on the Moon, the required power can be obtained. With regard to the direct nuclear pumping laser system[2], nuclear reactors on the Moon can be replaced by this system when its technology attains full development. Supply of Fuels As of 1990, worldwide energy consumption is said to amount to about 0.36Q per year (IQ = lO^J = 3 x 10^ kWh). To reduce the risk of heavy dependence on a single source of energy supply, some 25% of global energy requirement will be generated at the LEP.
The Moon and the Earth are both planets with the same geological features. Therefore, nuclear resources are available on the Moon as well. The reserves of nuclear resources of the Earth are estimated at 103 to 104 Q. If the ratio of nuclear energy resources on the Moon is the same as that of the Earth, the resources on the Moon will be 102 to 103 Q. Accordingly, the Moon itself will be the supply source of fuels for the nuclear reactor on the Moon. Energy supply from the Moon will be possible for thousands of years. Survey robots will be used to find nuclear resources, and excavation and other types of robots will collect them for processing at lunar nuclear fuel supply plants. Power Transmitting/Receiving System In the LEP system, energy is transmitted from the Moon to relay satellites to the Earth. The power transmitting and receiving system is shown in figure 4. During the transmitting and receiving course, energy conversion is conducted many times, and therefore conversion efficiency is a top-priority task for realization of the LEP system. A conversion efficiency of 30% will be the final target.
Energy Transmitting System on the Moon Energy is transmitted by laser from the Moon to relay satellites (in geostationary orbit) to power-receiving stations (on Earth). The distance between the Moon and the relay satellites is approximately 300,000 km, and thus it is important to finely control the diffusion of beam. For that purpose, a short wavelength laser, that is, a laser in the ultraviolet region, is required. The use of short wavelength laser makes compact both the laser transmitter on the Moon and the receiver (antenna) on the relay satellites. At present, the efficiency of energy conversion from electricity to laser light is too low, and much energy is lost as heat. Accordingly, consideration is given to the improvement of efficiency by recovering lost heat and using it again for power generation. However, the development of a laser oscillator with high conversion efficiency will be a priority subject for the future. At the ultimate stage, development of a direct nuclear pumping laser system [2] is expected for the nuclear reactor, in which nuclear energy is converted directly into laser light, not using the process from nuclear energy to electricity and then to laser light. In any case, energy will be transmitted from the Moon to the relay satellites in geostationary orbit using a laser system.
The relay satellites will circle in geostationary orbit at a distance of 36,000 km round the Earth every 24 hours. It is necessary to control the laser transmitting system accurately to track the relay satellites which are reciprocating always at an angle of 0.14 radian. Therefore, a highly reliable and highly accurate control system will be required. Relay Satellites The relay satellites in geostationary orbit serve as large-scale energyconversion stations. The relay satellites receive the ultraviolet laser beam from the Moon, convert the wave length, and transmit it to Earth as infrared laser. In SPS[3] proposed by P.E. Glaser, microwave is proposed for transmission of electricity from the satellites to Earth. Recent research results, [4] however, revealed a possibility that some nonlinear interaction of intense microwave and the ionosphere plasma may be caused by the microwave power transmission, and thus the transmission of large amount of energy by microwave may pose great risk to the global environment. Therefore, we would like to adopt a system in which energy is transmitted by infrared laser, which is thought to give less influence to the environment of the Earth and has a high efficiency in power transmission. By taking into account the effective utilization of geostationary orbit, multiple numbers of satellites can be arranged to supply energy to the Earth. The size of receiving antenna on a relay satellites depends on the wave length of the laser beam adopted and tracking accuracy of the laser transmitting system at the LEP. The antennas of a relay satellite and of the laser transmitting system on the Moon have to be always tracked to align. Power-Receiving Stations on the Earth Infrared laser light from the relay satellites in geostationary orbit is received at stations on isolated islands. Since the distance and orientation between the relay satellites and the receiving stations is almost unchanged, it is possible to construct large- capacity light-collecting equipment on the Earth. By connecting the equipment to existing power distributing systems, energy can be distributed all over the world. Construction of the Lunar Energy Park The LEP will be constructed by human beings, and, after start-up, will be maintenance-free. The environment on the Moon is different from that of the Earth, because powerful cosmic rays fall on the Moon. During construction of the LEP, the residential areas will be required in the location near to its construction site. After completion of the LEP, however, human beings will not be permanently stationed on the Moon when LEP is in steady operation. At the time of steady operation, the LEP will be operated automatically, including inspection of functions and repairs, using primarily intelligent robots. Routine construction work will be also undertaken mainly by robots. Construction of plants on the Moon will require large quantities of equipment and materials. It is appropriate that precision equipment will be provided from Earth, and building materials will be procured on the Moon. Fe-Si resources suitable for
building materials are abundant on the Moon, and good quality construction materials are available there. However, establishment of a transport system from the Earth to the Moon is essential. Feasible transport systems are chemical-fueled shuttle thrusters between the Earth and the relay satellites, space planes for the transport of people, and shuttles powered by ions, electricity, solar heat, nuclear power, or laser (laser, of course, being supplied from the LEP) for the transport between the relay satellites and the Moon. The construction sites for LEP will be at the polar regions of the Moon, from which a line of sight to the Earth is always available. The Moon has the same cycle period of its self-rotation as that of revolution round the Earth, and thus only at the poles is communication with the Earth always available. Thus, laser transmission of energy will always be possible. Since there is no atmosphere on the Moon, meteorites from space strike unimpeded. To avoid meteorites, the residential area has to be constructed underground. The heat radiating parts of nuclear reactors are exposed so it is necessary to provide protective shielding against small meteorites. For large meteorites, it will be necessary to constantly monitor them by radar and destroy them by laser. Program for LEP Development and International Cooperation The LEP is still at the conceptual stage. There are many factors to be examined, for instance, competitiveness with other types of energy, or estimation of the cost for realization of the concept. A great number of problems exist - realization of ultrahigh-efficient energy conversion system based on the FGM concept, construction of nuclear reactors in space, particularly the new type reactor, space robots, large-output highly-efficient laser generating equipment, laser-receiving equipment, safety monitoring technology for laser transmitted from the relay satellites to electricityreceiving equipment on Earth, and space mass transport system at ultra low cost. To realize such a grand program, international cooperation is essential, and the consensus of many countries is also necessary. Hereafter, we will intensively examine the LEP concept in more detail and establish a research committee for mapping out the development program. Furthermore, we will seek the participation in the LEP development program not only of scientists at home and abroad in the fields of nuclear power engineering, space engineering, materials engineering, optical communication engineering, resources engineering, but also scientists in the fields of economics, environmental engineering and international laws. Acknowledgments The authors thank professor H. Arashi of Tohoku University and Dr. K. Haga of Power Reactor and Nuclear Fuel Dev. Corp, for helpful discussions. References
[1] "Investigation report on the improvement of energy conversion efficiency by functionally gradient material technology", Science and Technology Agency of Japan, 1993. [2] D. E. Beller and J. M. Jacobson, "Parametric Design Study of a Nuclear-Pumped- Laser-Driven Inertial Confinement Fusion Power Plant", Transactions of Specialist Conference on Physics of Nuclear Induced Plasmas and Problems of Nuclear Pumped Lasers, Organized by Institute of Physics and Power Engineering of Russia, 26-29 March 1992, Obninsk, USSR, Edited by P. P. Dyachenko and A. V. Zrodnikov, pp.323-324. [3] P. E. Glaser, "Power from the Sun: Its Future", Science, Vol. 162, No.3856, 1968, pp. 857-861. [4] H. Matsumoto, N. Kaya, H. Kojima, M. Fujita, Y. Fujino, M. Hinada and R. Akiba, "Summary Report of ISY-METS Rocket Experiment", Proceedings of the 12th ISAS Space Energy Symposium", Organized by Institute of Space and Astronautical Science of Japan, 10-11 March 1993, Sagamihara, Japan, p.69-75.
Attend the third annual Northeast Space Development Conference, NSDC '94 Place: Rensselaer Polytechnic, Troy NY XZv Date: September 24-25, 1994 Progress in Commercial Space Development Register before April 15,1994 for the special rate of $50 Send a copy of this ad and your registration to: The Space Society RPI - Rensselaer Union Box 86 Troy NY 12180 For information about NSDC, call Dr. Gay E. Canough at ETM Solar Works solar power systems wireless power transmission For complete news on what is happening with solar power, terrestrial and celestial, subscribe to the SUNS AT Energy Council Newsletter! $25/yr Contact: Dr. Gay E. Canough, editor and publisher ETM Solar Works, PO Box 67, Endicott, NY 13761 phone/fax (607) 785-6499 _______ e-mail: Canough@bingvaxa.cc.binghamton.edu_______ SUNSAT F Energy Council Newsletter
Power From Space: Expected Role and Influence on Energy System Development L. S. BELYAEV, A. S. KOROTEEV, YU. N. RUDENKO* Summary: The prospective global energy situation including possible formation of the -world energy system is considered in the report. Conditions and problems of the use of large-scale energy flows from the space systems are discussed in this context. General views on global energy prospects The major conclusion of the World Conference on "Environment and Development" organized by the United Nations in Rio de Janeiro last year is that mankind cannot continue to develop in the traditional mode because of irrational use of natural resources and treatment of the environment. If the developing countries follow the path taken by the developed ones to achieve their prosperity, a global catastrophe is inevitable. The world society should change over to the sustainable development that would provide balances between the solution of social and economic problems and conservation of the environment as well as between the interests of existing and future generations. And this is a matter of all countries and nations. This is in particular true for the energy development that has influenced nature to the greatest extent. However, the measures and ways for a sustainable energy development are not clear enough as yet. Let us consider the energy demands first. Active energy conservation measures should obviously be undertaken and they will decrease the energy consumption especially in the developed countries. But if one takes into account that energy consumption per capita in the developing countries is tens of times lower than in the industrialized ones, then the high absolute growth of energy demands can be foreseen in the former countries particularly considering the population growth. Therefore, the growth of global (total) energy demands is most probable in the first part of the next century, but its exact figures are not known. By the year 2050, forecasts show that the global energy consumption would be 15-20 billion tons of coal equivalent (t.c.e.) (as compared to approximately 12 billion t.c.e. consumed at present). As concerns the energy resources, many studies carried out in various countries and international bodies after the energy crisis (see, for example, [1]) have shown that there are enough energy resources on our planet and the mankind will not face the energy hunger. However, they are very unevenly distributed throughout the world territory, the cost of energy does increase and certain rather serious constraints on the use of some forms of energy resources appeared in the last decade. * Siberian Energy Institute, 130 Lermontov st., Irkutsk 33 664033 Russia email: root@sei.irkutsk.su.relcom
One of the most influencing constraints is caused by possible changes in climate due to the greenhouse effect of increasing CO2 concentration in the atmosphere. It will veiy probably lead to restrictions on fossil fuel use in a global scale. Presently it is not clear how severe these restrictions might be. However, they should be taken into consideration and some scenarios with decreasing use of fossil fuels especially coal (whose resources are abundant) must be investigated. Another important constraint may be imposed on nuclear energy development depending on the possibility of creation of sufficiently safe reactors and acceptable fuel cycle. There are opposite opinions on this topic and both situations (scenarios) with and without use of nuclear energy should be taken into account. Restrictions on the use of fossil fuels and nuclear energy can drastically increase the role of renewable energy sources (RES). Large scale use of RES is certainly desirable from the environmental view point. But it requires the development of appropriate technologies (and even systems) which are very expensive at present. The increase in the RES share in the global energy balance to 40-50% will require huge financial and material expenditures comparable with the world total military expenses. Among possible ways of extensive use of RES solar space power systems [2], particularly the Lunar power system can be pointed out. Possible achievements in technological progress are vital for the future energy development. It concerns environmentally friendly technologies based on fossil fuels, new types of safe nuclear .reactors, a large variety of technologies for the utilization of RES, development of fusion reactors, etc. The most important renewable sources are terrestrial and space installations or systems for large- scale use of solar energy. Depending on the results of technological progress the centralized and decentralized energy supply will play different roles. The trend towards the decentralized energy supply on the base of RES will certainly be enhanced in the next century. However, it is not acceptable for large industrial centers and towns. Therefore, the centralized energy supply should receive further extension, if such broad-scale technologies as safe nuclear reactors, Lunar power system, etc. are successfully developed. In this case, formation of large energy systems at the regional and world levels will proceed. It is obvious that international cooperation becomes vitally necessary for development and commercialization of new energy technologies and creation of energy systems themselves. Concept of the world energy system The trend towards formation of specialized energy systems at the continental and global levels can clearly be seen in the development of centralized energy supply. They spread over the territory comprising big countries, regions and continents. The existing oil supply system is of the global nature already. Power and gas supply systems have actually become regional ones in some parts of the globe (in Europe, North America,
Asia) and the integration process is under way. The hypothesis of creation of the Global Electrical Network has been studied in the recent years [3]. Volumes of coal transported between regions is steadily increasing. Therefore, we can expect that the world-wide electric power, gas and coal supply and even nuclear energy systems will be created. The latter will include large international (inter-regional) projects for reprocessing and storage of nuclear fuel and long-term disposal of high-level actinides. This leads to the idea of possible integration of the indicated specialized energy- systems into the multi-product World Energy System [4], A somewhat similar idea has earlier been expressed by W. Haefele and W. Sassin [5], The concept considered below is a further step in this direction and differs from [5] in some aspects. It can be one of the possible options for the future global energy development. The multi-product World Energy System (WES) is expected to have the following features [4]: • WES is a single technically and technologically interconnected aggregation of power, gas, oil, coal, and heat supply systems; • WES integrates in fact the world power, oil, gas, coal and nuclear systems that already exist or may be installed in the distant future; • WES is viewed as a possible way of further development of centralized energy supply; • technological unity of WES is its most important property that requires the operation control and development management of WES as a whole; • WES can be created only on the base of international efforts and cooperation. Large energy centers (with the capacity of tens of GW) which are designed for production of electricity and heat, synthetic fuel, chemical and other products are basic elements of WES integrating specialized energy systems (of power, gas, oil and coal supply) into technological unity (see Figure 1). Each center (possibly located on a certain restricted territory) can provide several countries with energy, fuel and raw materials. Creation of such centers is possible on the basis of international cooperation only. The following examples of such centers can be pointed out: • gas-chemical complexes constructed in the Near East, North Africa, West Siberia, etc. for production of electricity, liquid fuels, chemical raw materials, etc.; • nuclear centers which can produce electricity, synthetic liquid and gaseous fuels as well as chemical and other products from coal, shales, bituminous sands, etc.; • energy complexes on the base of large coal fields (in Siberia, China, Australia, etc.) for production of electricity and synthetic fuels;
• large solar centers (in Sahara, Middle Asia, etc.) or rectennas from solar power satellites or the Lunar power system for production of electricity and synthetic fuels (for example, hydrogen); • large tidal power plants (for example, the Penzhinsk station) used for production of electricity, hydrogen, etc. Such centers will have a powerful transport infrastructure and will be an interconnecting link between regional single product energy systems of different kinds. Apart from large energy centers (and transport ties) WES may include: • large installations (plants, complexes) for conversion of one form of fuel and energy to another (for example, for hydrogen production by water electrolysis or for using hydrogen or methane for electricity generation); • large-scale energy storage systems for leveling the daily, seasonal and yearly energy consumption (underground gas storage, large water reservoirs of hydro power plants, hydrogen storage, warehouses for the fuel elements for nuclear power plants) that should be used for regulating the energy consumption in WES as a whole; for example, underground gas storage can regulate both the gas consumption and electricity production (by gas-fired power plants). These WES elements not indicated in Figure 1, together with energy centers create a technological unity (interdependence) of the processes of WES operation and necessity of coordinated WES development management and operational control. Creation of WES can provide new opportunities for mankind in the solution of global problems: a) more economic, reliable and sustainable energy and fuel supply; b) easier solution of global environmental problems caused by energy systems including the CO2 problem; c) improvement of the energy supply in the developing countries, particularly by environmentally clean energy carriers (electricity, natural gas, hydrogen); d) involvement of the presently unused energy resources especially in the developing countries; e) realization of considerable effect from the combination of seasonal (yearly) and daily (weekly) consumption curves in regions of different latitude and longitude; this is most important for the use of renewables with the uneven output; f) improvement of the territorial location of energy plants;
g) increase of economic and business activity, international trade and scientific- technological cooperation as well as improvement of political climate and appearance of the alternative for armament expenditures. Formation of the world energy system will obviously proceed gradually (by stages) starting from the modem state of national and regional energy systems. The ways of transition will depend on future conditions which seem now to be very uncertain. Uncertainty in the possibility (and terms) of creating safe nuclear reactors and cheap photovoltaic cells influence WES structure most of all. Nuclear and solar energies are the only alternatives to fossil fuel that can be developed in a really large scale, though both are rather expensive. If attempts of safe nuclear reactor creation are not successful, then the nuclear way will be impossible and only the solar alternative is left. With the restriction of fossil fuel consumption this case will be the most difficult. However, in the general case the whole spectrum of energy forms (oil, coal, electricity, solar and nuclear energy) should be considered in WES structure. Depending on the total energy demands, admissible volumes of CO2 emission and economic indexes of various energy forms (their competition with each other), the scales of development of various specialized systems included in WES will be different (down to zero). Figure 1 illustrates the principal structure of WES for such a general case. A multitude of specialized energy systems is aggregated into large energy centers (complexes) into a multi-product system. Other WES elements and local heat supply systems are not specified. The WES concept certainly requires rather broad discussion by international experts or teams. Some peculiarities of WES caused by energy supply from space are considered in the next section. Varieties of the world energy system with large-scale energy supply from Space Solar power satellites (SPS) on the geostationary orbit (which rotate at the speed of Earth's rotation and "hang" over the receiver or rectenna) with a capacity of about 5 GW [6] and the Lunar power system (LPS) with a capacity of 20000 GW [7] are the most interesting projects for space energy systems utilizing solar energy and transmitting it to the Earth via microwave beams. One more large-scale project on recovery of Helium-3 at the Moon with its transportation to the Earth and subsequent utilization in fusion reactors [8] is not directly a space energy system (the fusion reactors are located on the Earth). Other known proposals (for example, [9, 10]) are of insufficient scale for the world energy system and can be treated as intermediate stages in realization of the first two projects. Solar power satellites or rather their terrestrial part - rectennas - can surely be the WES elements. An individual satellite as an energy source will differ negligibly from
large power plants which use other renewable energy sources, in particular terrestrial solar or tidal power plants. It will be characterized by regular interruptions in operation during nights when the satellite finds itself in the Earth's shadow. Therefore, the energy storage systems or duplication of capacity at other (traditional) power plants will be required. It should be noted that the strict "hovering" of the satellite over one point (rectenna) can be provided only, if the geostationary orbit comes strictly along the equator (the rectennas in this case are located on the equator itself). It also turns out to be possible to launch satellites onto the orbit at a small angle to the equator. In so doing the satellite will shuttle along the proper meridian, crossing the equator twice a day and moving away from it to both sides at a certain distance which depends on the orbit angle to the equator. If this angle is relatively small, the satellite will be constantly seen from the points situated close to the equator and the given meridian. It seems possible to arrange constant reception of energy from the satellite to the rectenna situated in such a point by the corresponding focusing of a microwave beam. However, on the whole the energy from satellites on the geostationary orbit can be received only in a certain "equatorial" zone whose width must be determined by ballisticians. For some reason this constraint on the use of SPS is not noted in [2,6], If several (especially dozens of) solar power satellites are launched, their role in WES and the effect on its modes will be essential. Interruptions in power supply at nights are in principle less painful than irregular interruptions (due to weather or Lunar cycles), particularly in the day and evening time. In electric power systems such interruptions in power supply from rectennas can even assist in solving the problem of a night gap in load. However, a large share of rectennas in electric power systems can stipulate special measures to be taken. They may include either the mentioned storage systems or the duplicating capacities of the traditional power plants or power supply from the neighboring systems with excessive base power. Principally it is possible to transmit power for very long distances (5-10 thousand kilometers) in the longitudinal direction from the rectennas, whose satellites are lighted by the sun, towards the rectennas situated in the shadow. The choice of these measures requires special studies. On the whole a strict regularity of interruptions in SPS operation at nights is their positive feature in comparison with other renewable energy sources. Note that the problem of interruptions in power supply is typical of all renewable energy sources except for geothermal energy. Possible solutions are determined by specific sources and conditions of their use. However, a large-scale use of renewable energy sources in WES is characterized by some general features and trends: 1. Until the creation (invention) of cheap energy storage installations of large capacity renewable energy sources of large capacity will be applied in the systems (first of all in electric power systems) as a rule for fuel saving with complete duplication of their capacity. It is explained by the fact that at present pumped storage plants whose cost is comparable with the cost of other traditional power plants are the cheapest storage plants. If this cost is added to the cost of power plants on renewable sources and the obtained sum is increased in proportion to which the guaranteed (leveled) capacity of the renewables is lower than their installed capacity, specific costs on a guaranteed
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