My impression from examining chart below is that the "aluminum economy" is wanted: Refuel your car by turning in your aluminum oxide and getting back aluminum metal which you stick into your car's Al-air battery and off you go. The oxide is then re-converted to metal at a electrolytic smelting plant somewhere electricity is cheap. Stuff MJ/kg MJ/liter $Cost/kg (year 2014) ------------------------------------------------------------------------ Gasoline 46.4 34.2 4 Fat 37 Coal 30 20 (if one solid lump) 0.066 Batteries 0.1 to 0.9 0.3 to 4.3 TNT 4.6 Boron 58.9 137.8 5000 Silicon 32.2 75.1 3.1 Aluminum 31.0 83.8 1.9 Aluminum-air and Silicon-air batteries both have been made, and the former successfully commercially (were extensively used as backup power sources for the phone system). Oxygen, Silicon, Aluminum are the 3 most abundant elements in Earth's crust in decreasing order. Boron is about 90 times rarer than aluminum, Lithium is about 50 times rarer than Boron, and Beryllium about 10 times rarer than Lithium. The "boron economy" is stupid because boron is too rare & expensive to make. (It also has a very high melting point and is very hard, two other reasons it is hard to deal with.) It seems absolutely absurd to claim we each should run our car by refueling it with $200,000 worth of boron. The "hydrogen economy" is stupid since H is too dangerous/explosive and has far too low volumetric energy-density. There have been metal hydride storage ideas to get safer, but these are expensive and complex and low per-mass energy density. Either way running your car with hydrogen is absurdly unattractive. Rechargeable batteries are stupid since too expensive, do not last long enough, inefficient, low energy density, toxicity and environmental disposal problems. Beryllium is stupid since toxic and very rare. Lithium is stupid since rare. Silicon perhaps would be better than aluminum but I doubt it because it is more expensive, lower electric conductivity, harder, brittle, higher melting point (1687K versus Aluminum's 933K). -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)