Nanohedron wrote:
david_h wrote:
... the story is incomplete without telling us about turning rust back into iron (as PB+J says).
No disagreements there. If it's a strictly chemical process, then the system's not closed. But if power is required, then the burning of iron to power the "unburning' of iron sounds like a distinct possibility. Wouldn't that be a closed system?
Firstly, there is no such thing as a closed system, unless you mean the universe itself. Secondly, this particular one is not closed. From reading about this elsewhere, when the iron powder is first subject to combustion, the product of that combustion is light, heat and rust particles. In order to re-use those rust particles, you need to extract the oxygen. This is done by adding hydrogen and power, to produce, by electrolysis, iron and water. So, in total, you're putting in oxygen and hot gases at the start in order to sustain the combustion process, and you're putting in hydrogen and more power* to recycle the iron. No power is produced in the second phase, although it is in the first phase in the form of light and heat.
Sorry for my slapdash use of various quasi-scientific terms there ...
* I see that they're saying that solar or wind power could be used for this phase but, if that's the case, it rather begs the question as to why they don't just use solar or wind power in the first place. As I understand it, it's because, "due to location or other factors," it is not always possible to use solar or wind power. That leads to the presumption that, in order to recycle the rust particles in an environmentally friendly way, you might have to transport them. Hmmm ...