[kdtop]

The reason we burn fossil fuels is because we can pull the oil out of the ground and utilize the stored energy. This seems like a different situation than is being described with using iron oxide as a sort of "battery", that will have to later be recharged (reduced away from iron oxide). Thus it seems more like a mechanism for utilizing previously stored energy than as a readily available energy source waiting for exploitation.

[craftkiller]

With solar's rapidly declining price, its not hard to imagine a near-future where daytime energy is abundant. In such a scenario, materials that come out of the ground with energy and materials that you need to charge-up like this are practically equivalent. Therefore the days of oil's value are numbered as long as we continue to develop fuel-like renewable energy stores like this.

[herogreen]

But would solar price be the same if the world global energy mix used no fossil fuel ? My belief is no, not at all, unless we used nuclear which can give an energy density similar to fossil fuels. But I have no research data to back this claim.