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Comment by tbrownaw | Hacker News Reader

Shouldn't this have the same efficiency problems as photovoltaics, where it can only use photons above a certain energy and only takes that same amount of energy from each used photon (the energy difference between charged and uncharged molecules playing the role of the bandgap)? I wouldn't think it would be that hard to reach 30% storage efficiency for a few days (weeks?) with normal heat-something-up storage given reasonable volume and insulation.

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Not really -- solar thermal already is about 75% efficient. I.e., 100J of light => 75J of heat added to working fluid. My understanding was that this chemical toggles state at the addition of any heat -- not necessarily by the addition of solar energy. But that's just a guess, i'd never heard of diruthenium before five minutes ago either :)

I think I found the actual paper: http://zeppola.mit.edu/pubs/FvRu_Thermal_Reversal_AngewChem.... [ http://zeppola.mit.edu/index.php?option=com_joodb&view=a... ].

    * It stores energy from light, at 350nm (near UV)
    * It releases energy when catalyzed or heated (barrier is 30 kcal/mol)
    * It stores 0.2 MJ/Kg (vs. 0.5 MJ/Kg for lithium ion batteries)
    * Using iron instead of ruthenium lowers the energy barrier for returning to the ground state, enough that it's useless at normal temperatures

Wow, cool! I take it back, then :)

Would i be correct in thinking that this probably makes it less useful? Current thermal collectors use absorbent coatings that are "full-spectrum," with a minimum of IR emission, which i have to imagine contributes to their really high efficiencies.

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