Supplying significant power to Earth is a very large challenge (6). The United States uses approximately 600 GWe (electric power) and the world 1,800 GWe. World thermal power production approaches 5,000 GWt. Consider competing approaches used on Earth to supply us with power. Hydroelectric dams are the largest single unit sources of electricity. Grand Coulee is presently the largest operating dam. It is a solar terrestrial power system. Sunlight evaporates water from the Pacific Ocean which then falls as rain into the 300,000 square kilometers drainage basin of the Columbia River. Water collects behind Grand Coulee dam and is forced by gravity through its huge turbines. Over 9 GWs of turbines could be installed in Grand Coulee. However, even the mighty Columbia River cannot always supply a sufficient flow of water. The dam normally produces less than 6 GW of the cheapest power in the nation. Grand Coulee is over 1.3 km long, about a tenth of a kilometer high and contains 40,000,000 tons of concrete and reinforcement. Over 7,000 people worked 7 years to complete the dam just in time to power aluminum production in World War II. It was a vast social project which proved to the depressed America of the 1930s that man had some physical control over his life and country. Grand Coulee pays back its energy of construction every eight months. However, the dam would have never been built if it had been necessary to dig out the drainage basin of the Columbia River before constructing the dam. Grand Coulee used the unique natural resources of geography and adequate rain for which there was no human investment. We will argue in a few paragraphs that the moon provides a space equivalent of many Columbia River basins for the efficient construction of solar power plants. There are even larger dams than Grand Coulee under construction (19). But there are too few “Columbia River Valleys” on Earth to provide most of the power needs of Earth. Grand Coulee works and it provides a useful image of the size of other large power systems. Coal fired power plants appear to be very mass efficient and are relatively easy to build compared to a dam or nuclear plant. However, every year a complex of 10 GWe coal plants would burn the mass equivalent to Grand Coulee in coal. The U.S. now burns over 18 Grand Coulees of coal a year and the world several times this much. Coal use must increase as the resources of hydrocarbons rapidly decrease. We live in the peak decades of the fossil fuel era. High grade petroleum is being quickly depleted. Coal is available in enormous quantities but its use will become progressively more inefficient and expensive. There is increasing concern over the long-term impact on the environment of introducing extremely large quantities of CO2 annually into the atmosphere. Our worldwide industrial society is based on non-recoverable fuels and minerals. Our human activities deplete major resources of the Earth. Constantly increasing consumption of non-renewables forces industries to use lower grade resources. Competition between individuals, companies and nations can only become sharper over the next decades. Energy is the most basic of our industrial needs. Given adequate, cheap energy all other industrial materials can be extracted from the common resources of Earth or even the moon (7, 9, 10). Steady economic growth appears to depend on the net energy yield available to the world economy (5). Power systems which consume depletable resources (coal, oil, gas . . .) have a negative energy yield. Nuclear power plants require very sophisticated construction techniques and are of the general scale of Grand Coulee (8,000,000 tons) but of shorter expected service life. Nuclear fission systems pose major decommissioning problems and rare but catastrophic accidents cannot be ruled out. Radioactivity of the fuels, ashes and
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