Sand as a form of power storage?
The military actively encouraged, when it did not finance directly, the giant cyclotrons, betatrons, synchrotrons, and synchrocyclotrons, any one of which consumed more steel and electricity than a prewar experimentalist could have imagined. These were not so much crumbs from the weapons-development table as they were blank checks from officials persuaded that physics worked miracles. Who could say what was impossible? Free energy? Time travel? Antigravity? In 1954 the secretary of the army invited Feynman to serve as a paid consultant on an army scientific advisory panel, and he agreed, traveling to Washington for several days in November. At a cocktail party after one session, a general confided that what the army really needed was a tank that could use sand as fuel.
Silicon is high up on energy density… http://nzenergy-environment.co.nz/home/free-articles/could-silicon-power-stations-replace-coal-and-nuclear.html
Future power stations could burn silicon instead of coal. This is the radical vision of Waikato University scientist Earl Bardsley, who believes the world’s desert sands are an ideal source of silicon. And if this sand can be converted to silicon using solar power, it could be a cheap and eco-friendly solution to the world’s energy needs. Prof Bardsley says solar energy could be used to create silicon from sand at smelters on the desert margins. The only waste product from silicon power stations would be large amounts of solid silicon-dioxide “ash” but this could be recycled back to the smelters to be reduced to silicon again…Prof Bardsley calculates says a stockpile of silicon just a few metres thick over a square kilometre has the same energy content as all NZ’s hydro lakes. He suggests a large solar power system in Australia could provide silicon fuel for a modified Huntly power station. In energy terms, silicon is comparable to coal when burned.
“The Sustainable Global Energy Economy: Hydrogen or Silicon?”, Bardsley 2008:
We envisage the use of silicon as a global carrier of renewable energy based on carbon-neutral reduction of silica (quartz) in silicon smelters to yield metallic silicon in bulk supply. The silicon is then shipped around the world for electricity generation in emission-free thermal power stations which oxidise the silicon at high temperature to provide base load electricity. The storage efficiency factor is about 30%, taking into account energy losses in silicon reduction and subsequent conversion to electric power (Auner and Holl, 2006).
…The second critical technological requirement is the construction of efficient silicon-fired power stations where the oxidation of fuel silicon can be maintained at a sufficient rate to produce the desired power output. A restricting factor here is that the SiO2 oxidation product remains with the silicon and partially restricts its subsequent oxidation. An operating temperature in excess of 1,600 °C may be required so that both the silicon and SiO2 remain in the liquid phase to maximise continued oxidation through oxygen diffusion into the molten material. Considerations of optimal power station design are beyond the scope of this paper but the silicon combustion process could involve maximising the surface area of the silicon fuel material in an oxygen-enhanced environment. If silicon power stations are indeed viable, then they would be very different from their fossil fuel equivalents in that no emissions are generated and they would yield copious amounts of solid SiO2 ‘ash’ of some 50% greater volume than the original fuel silicon. This inert silicon dioxide might be recycled back to a silicon smelter or used locally in land fill.
Well. That’s not a power system I’ve ever seen proposed before: burning silicon to silicon oxide at 1600 degrees. (Is mesothelioma an issue…? On the other hand, hard to be filthier than coal.) Pretty elegant proposal: extract sand from the deserts, purify with solar power to store their variable power for later use, transport and burn locally - and eliminates most of the base load, storage, and transmission problems with other power supplies & with dealing with the randomness of renewable power supplies.