bcw@duke.UUCP (11/01/83)
From: Bruce C. Wright Re: SPS and global heating Although it is true that most of the energy beamed to earth from an SPS will be radiated into the environment as heat, it does not at all follow that this will result in more (or even significant) global warming than fossil fuel. First of all, much of the energy in generating stations is expended as heat directly (about 60% as I recall), while in an SPS system the energy is converted much more efficiently (more like 20% waste or less as I recall). This would allow a much larger amount of useful energy for the same amount of heat load if SPS stations were used. Secondly, although it is true that the energy from fossil fuel was absorbed from the sun at one time, it is being released MUCH MUCH faster than it was ever absorbed from solar energy. Thirdly, and in many respects most importantly, the net heat accumu- lation on the earth is going to be the integral sum of the amount of heat received from the sun minus the amount of heat radiated from the earth. The major problem with fossil fuel is NOT the amount of heat it produces directly (though that is a local problem in many places), but the amount of carbon dioxide that it produces, which tends to hold the heat better than most of the other compounds in the atmosphere; therefore fossil fuels reduce the amount of heat which can be re- radiated by the earth IN ADDITION to adding to the heat load directly. In addition, in many places power is generated by wood or other recently living plant matter. This has the effect of decreasing the ability of the biosphere to absorb carbon dioxide, aggravating the heating problem. Objecting to SPS because it would increase the earth's heat load is JUST PLAIN SILLY. There are many other problems with SPS (notably the fact that it is not a tested technology, and depends on several factors which are themselves not tested technology - such as assembly of large objects in space, how to get the material there when we have no experience with doing this on that magnitude from either the earth or the moon, etc), but this is a red herring. Bruce C. Wright @ Duke University