2009-09-19

Space Based Solar Energy

One topic on today’s CBC Radio One’s Quirk and Quarks discussed space based solar power. The discussion missed a significant factor and I sent the following thoughts in response:


Today's discussion about space based solar power was most interesting. One point did get missed and it is very essential when considering the scale of such a project. That is the law of conservation of energy. Whatever the source of energy, whatever the purpose into which we put energy, when we use energy we only transform it from one form of energy to another. What is the final form of all energy that we use, the energy waste product? It is always heat. H-E-A-T!


Our earth experiences a certain flux of energy from the sun already. Living things capture some of that energy and transform it for life functions, either using it immediately, which just turns it into waste heat, or storing it. Unused solar energy either gets reflected or absorbed and again transformed into heat. Waste heat gets radiated back out into space and our atmosphere moderates that radiation. In equilibrium, the flux of energy falling onto the earth's surface equals the amount of energy stored by life processes plus the heat our earth radiates back into space. Earth's average temperature remains constant.


Our current global warming problem stems from two sources. The one most talked about at present being our habit of releasing carbon dioxide and thus inhibiting the earth's capacity to radiate waste heat away into space. We retain more of the heat we generate. The other part of the problem in using fossil fuels lies in the fact that we are using long stored energy. We actually increase the flux of energy at the surface of the earth. Thus the flux of energy at the surface of the earth is greater than the sum of reduced energy the earth radiates back into space and energy stored by means other than atmospheric heating. Earth's average temperature rises.


Space based solar energy only solves half the problem. Fully implemented, it may stop the increase in carbon dioxide in our atmosphere and thus remove the problem of reduced radiation of waste heat back into space. Unfortunately, as with other currently considered alternative energy sources, geothermal, nuclear fission, nuclear fusion, it still adds to the energy flux at the surface of the earth. At the scale your discussion suggests as necessary for this energy source to be feasible, this addition of solar energy that would otherwise pass the earth by will be vast. The flux of energy at the surface of the earth will be greater than the combined energy the earth normally radiates back into space and natural energy storage other than into the atmosphere. Earth's average temperature will still rise.


If we are going to bring vast amounts of energy onto the surface of our planet, in addition to the energy the earth normally receives, then we must either have means of storing that extra energy somewhere other than in our atmosphere or improve the earth's capacity to radiate waste energy back out into space. No two ways about it!


Capturing and using the solar energy that would normally pass us by really implies using that energy where we capture it, out there in space not down here. The real long term answer lies in getting off this planet (and staying off any other) as proposed long ago by Gerard K. O'Neill.