Frontier literature reading
前沿文献阅读高枕无忧的意思
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姓名：望月怀古
An Overview of the Solar Power Satellite Options Abstract-The objective of the solar power satellite (SPS) is to convert solar energy in space for u on Earth. Its most significant benefit is the potential for continuously generating large-scale electric power for distribution on a global basis. While there has been no SPS development program in the United States since 1980, it has continued to be investigated in veral countries. The SPS system is outlined and the status of the SPS concept development is reviewed. Results of asssments of key issues are reported including economic considerations and environmental issues such as health and ecological effects of microwave beaming, non-microwave health and ecological effects, beam effects on the atmosphere and ionosphere, and ele
ctromagnetic compatibility, as well as physical resource requirements including land u, materials availability and energy pay-back periods. Legal issues and the need for international agreements on SPS operations are outlined. International SPS-related activities are discusd within the context of evolving space programs with the focus on Europe, Japan and the former U.S.S.R. An approach for an evolutionary advancement of SPS to meet requirements for power supplied at first for u on Earth and in space is prented, and a growth path to achieve the potential of power from space for u on Earth is outlined. The significance of advancements in technologies applicable to the development of the SPS as an alternative energy option for u on Earth, and as a potential stimulus for space infrastructure evolution, including the u of extraterrestrial resources, are discusd.基金业绩
1. INTRODUCTION
The world is encountering a “shifting of history’s tectonic plates”[1]. The fundamental changes occurring in the global economy, the uncertainties brought about by the disintegration of the Soviet Union, and the efforts to create a United Europe are resulting in the reevaluation of the 21st Century world order. Viable options must be provided to meet increasingly insistent demands for higher living standards of the exponentially growing global population, and to forestall instabilities leading to military confrontations with potentially disastrous results.
Key to the achievement of a new world order will be the development of energy resources at a societally acceptable and economically affordable cost within a realistic planning horizon. This must be the theme for the future development of all energy sources whether bad on fossil, nuclear or renewable resources. The significance of the SPS concept within the context of meeting global energy demands, and in consonance with this theme is its potential to meet not only growing global needs for electricity, but also to replace fossil and nuclear fuels. The SPS will be a macro project when there is a connsus regarding its benefits for humanity. Macro projects are distinct when compared to all other enterpris by virtue of the deployment of advanced technology and process that were previously demonstrated on a much smaller scale, the magnitude of the required investments with returns on such investments extending over a time frame not customary in conventional projects, and
with expected societal benefits to large regions, groups of nations, or globally.
There is an opposing view how best to meet future energy demands bad on the development of appropriate technology utilizing distributed, small-scale, renewable energy sources. Appropriate technology is a concept bad on the view of a world of small, largely lf-sufficient communities following the Jeffersonian model but hardly a realistic goal for the world community of the 21st Centu
ry [2]. The technical, economic and societal dilemmas of large-scale engineering projects have been recognized by E. F. Schumacher[3], but not considered always and inevitably “inappropriate. ” As Schumacher points out: “It depends on what we are trying to do.”
2. THE SPS SYSTEM
As originally conceived[4] an SPS could utilize various approaches to solar energy conversion. Among the conversion process, photovoltaic conversion was lected as a uful starting point becau solar cells were already in wide u in communication, Earth obrvation and meteorological satellites, both in low-Earth orbit (LEO) and in geosynchronous orbit (GEO). Since then, an added incentive has been the substantial progress being made in the development of advanced photovoltaic materials, microwave and lar power beaming, and the increasing confidence in the achievement of significant cost reductions in space transportation, and in the u of lunar materials envisioned as part of the Space Exploration Initiative[5].
In the SPS concept, solar cell arrays would convert solar energy directly into electricity and feed it to microwave generators forming part of a planar, phad-array transmitting antenna. The antenna would direct a microwave beam of very low power density precily to one or more receiving antenn
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as, at desired locations on Earth. At the receiving antennas, the microwave energy would be safely and efficiently reconverted into electricity and then transmitted to urs. An SPS system could consist of many satellites in Earth orbits, e.g., in GEO, each SPS beaming power to one or more receiving antennas at desired locations.
Congressional Office of Technology Asssment[6], and the National Rearch Council of the National Academy of Sciences[7]. The asssments considered technical, economic, environmental and societal issues. In preliminary studies of the SPS concept (1968 to 1972), a plan for an SPS R & D program was outlined[8]. In 1972, a feasibility study was undertaken to evaluate an SPS design for a power output of 5 GW for u on Earth [9]. This feasibility study identified key technological, environmental and economic issues for further study and provided the foundation for more extensive system definition studies[10]-[12]. An asssment of the SPS concept was the objective of the SPS Concept Development and Evaluation Program (CDEP) [13]. “To develop, by the end of 1980, an initial understanding of the technical feasibility, economic practicality, and societal and environmental acceptability of the SPS concept.”
This asssment indicated that no single constraint has been identified which would preclude the development of an SPS for either technical, economic, environmental or societal reasons, and that t
he NASA SPS Reference System which assumed that 5 GW of ba load power would be generated at the receiving antenna on Earth demonstrated that the technology for transmitting power from space to Earth is amenable to evolutionary development, and that the SPS concept is technically possible. In the 1980’s, the applications of extraterrestrial energy and materials resources to meet future global energy needs were of increasing interest[14]. The challenges to develop the SPS capable of using lunar resources are formidable. International efforts including
demonstration projects will be required over a period of decades to make the transition from the current SPS design concepts to designs that can u lunar resources or could be deployed on the lunar surface[15].
3. Economic and Societal Asssment Issues
Economics: Detailed technical asssments of the SPS system were performed as part of the CDEP by the U.S. Department of Energy and NASA[13]for both microwave and lar beam transmission, with positive results. The CDEP addresd economic and societal issues in considerable depth becau they are the key to future SPS development as summarized below.
The economic justification for an SPS development program must acknowledge that it is not possible 雷克萨斯标志
to know now the cost of a technology which will not be fully developed
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for at least 15 years or commercialized in less than 20 years. Justification is equally difficult to provide for other advanced energy technologies.
Cost-effectiveness analys alone are inappropriate becau they would require the extremely difficult task of postulating credible scenarios of the future. The near-term decisions regarding the planning for an SPS program should be bad on the resources allocated to the SPS development tasks and their priorities rather than the projected economics of the SPS in the 21st Century.
停止的反义词Cost projections do not provide meaningful estimates of the potential market penetration of the SPS or alternative energy supply technologies becau the uncertainties in forecasting prices are much larger than the cost differentials on which the cost comparisons among competing technologies will eventually be bad. However, such cost studies provide estimates of the delivered cost of power to indicate whether the SPS has any chance of being competitive, identify the major cost elements so that program efforts can be properly focud to reduce the projected costs, develop a consistent framework to evaluate different technological options, determine the impacts of raw material requirements and availability on cost and the effects of a development program on labor costs and c
apital markets, and asss the cost risk in comparison with alternative energy supply technologies, including environmental impacts and societal effects.
The SPS was compared with alternative energy technologies, including coal, nuclear and terrestrial photovoltaic systems, in terms of cost and performance, health and safety, environmental effects, resource requirements, and institutional issues[16].
The asssments indicated that: The life-cycle cost range for the SPS overlaps the competitive cost ranges of alternative energy technologies; All the technologies considered will have distinct, though different, health and safety impacts; The low-level and delayed impacts of all energy technologies are difficult to quantify and asss; Each technology has material requirements that could be critical, becau of environmental control standards or limited production capability, however, the requirements do not appear to limit the SPS; The total amount of land required for the complete fuel cycle is roughly the same for all energy technologies; however, the SPS and terrestrial centralized photovoltaic systems would require large contiguous land areas, although SPS receiving antennas could be placed on off-shore floating structures; The SPS, fusion and other advanced energy technologies may be difficult to operate within the current regulatory environment; however, the SPS would also be subject to international regulations that may also apply to other energy technologies.
The Department of Energy and NASA SPS program was unique in that for the first time a与成功有关的名言有哪些
technology development program focud not just on key technology issues but was also concerned with environmental effects, comparative economic factors, societal issues and program risks and uncertainties before any commitment to a development program was made[17]. Among the consideration the most significant non-technical issues where the SPS’s environmental effects and resource requirements.
4. Environmental Effects
The key environmental effects associated with the SPS are tho which could affect human health and safety, ecosystems, climate, and interactions with electromagnetic systems. Health and Ecological Effects of Microwave Power Transmission:At the perimeter of a receiving antenna, the public would be expod to microwaves at a power density of 0.1 mW cm-2. If as assumed for the NASA SPS reference system, 60 receiving antennas in the continental United States were spaced an average of 300 km apart, the minimum power density at any point beyond the antenna location would be about 10-4mW cm-2[18]. In the former USSR, the maximum value for continuous, 24-hour, exposure of the general public was estimated to be 10-3 mW cm-2. The workers within the receiving
antenna area would not be expod to levels exceeding U.S. guidelines for occupational exposure with suitable precautionary measures. The fact that large populations have been expod to microwave energy from communications, medical, radar and industrial process for many decades and, more recently, from 250 million microwave ovens, without demonstrated adver effects on human health and the ecosystem, is an indication that microwaves beamed from space to Earth are unlikely to result in undesirable health and ecological effects, although rearch of such effects on biota (e.g., birds, should be continued[19]).
Non-Microwave Health and Ecological Effects: Among the various space-related activities only the exposure of the space workers to ionizing radiation appears to prent a major health risk. Most of the other health and ecological effects of the construction and operation of receiving antennas and launch sites have conventional impacts which would be controlled or mitigated by appropriate engineering solutions, and are analogous to developing and constructing alternative energy sources. The risks from ionizing radiation to space workers could be minimized through carefully designed shielding for space vehicles, for working and living modules and by the provision of solar storm shelters. Of greatest concern in GEO are the high-energy, heavy ions emanating from galactic radiation which may result in exceeding recommended exposure limits for workers. More data are re
quired to establish the expected ionizing radiation environment in GEO to guide the design of measures to limit exposure of space workers.
Effects on the Atmosphere: Weather and climatic effects of waste heat relead at a receiving antenna site would be generally small, comparable to the heat relead over suburban areas. The absorption of microwave power in the troposphere is expected to increa during heavy rainstorms, but even then would have only a negligible effect on the weather. The air quality effect of the launch of advanced space transportation vehicles, which would increa sulphur dioxide concentration, would not be critical. Nearly all of the carbon monoxide would be oxidized to carbon dioxide, and the amount of nitric oxides formed would be negligible. The change in the globally averaged ozone layer due to SPS launches would be undetectable as would the effects of nitrogen oxides. Transient clouds at stratosphere and mesosphere altitudes could be induced in the vicinity of the launch site, but they would not be expected to have a detectable impact. Some acid rain might occur near the
