Inexpensive and Environmentally Safe Solar Power for Earth from Bases on the Moon DAVID R. CRISWELL+ Lunar Power System (LPS) The latest Space Commission Report to the President of the United States (1991), a recent NASA (1989) task force on energy from space, and the acting Associate Administrator of NASA (Cohen 1991) all recommend immediate studies of bases on the moon to provide electric power to Earth. Lunar power bases should be the next major goal in space. Figure 1 shows the general features of the Lunar Power System (LPS). Pairs of power bases on opposite limbs of the moon convert dependable solar power to microwaves. The Earth stays in the same region of the sky as seen from a given power base. Thus, pairs of bases can beam power dependably to collectors, called rectennas, on Earth. Rectennas, simply specialized types of TV antennae and electric rectifiers, are the major cost element. Figure 1 greatly exaggerates the sizes of the orbital reflectors (<lkm diameter) and rectennas (0.4 to several kilometers diameter). In the late 1970s the Department of Energy estimated the cost of rectennas. LPS power from rectennas will cost a fraction of a cent per kilowatt-hour when receiving beams with an intensity of 20% of sunlight or 250 Megawatts per square kilometer. To power the United States the U.S. rectennas would occupy only 5% of the land area now devoted to the production and distribution of electricity in the United States. The cost of power increases as beam intensity decreases. For a beam intensity equal to approximately 1% of the intensity of sunlight, or one-fifth the leak allowed from a home-microwave oven, the power would cost approximately 10 cents/ kilowatt- hour. A mature pair of lunar bases can broadcast several thousand gigawatts of power, approximately the level of electric power now generated on Earth. The mature LPS uses very large segmented antennae on the moon, approximately 50 to 100 kilometers diameter as perceived from Earth, to direct power to Earth. Each large antenna is composed of tens of thousands of fixed, billboard-sized screens made of lunar materials. These large, segmented antennae reduce the stray power around a beam to a tiny fraction of the safe levels specified in guidelines in the United States. LPS can be environmentally neutral, even if 50 times more electric power is provided to Earth than is now used on Earth. LPS can safely provide both low and high power beams. Rectennas in isolated regions could receive more intense beams * Director, Institute of Space Systems Operations, University of Houston, TX 77204-5502, USA.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==