3 ms·

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 energ

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.

seigenblues 16y ago
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 :)
- tbrownaw 16y ago
  I think I found the actual paper: http://zeppola.mit.edu/pubs/FvRu_Thermal_Reversal_AngewChem.pdf http://zeppola.mit.edu/pubs/FvRu_Thermal_Reversal_AngewChem.... [ http://zeppola.mit.edu/index.php?option=com_joodb&view=article&joobase=3&id=70:mechanism-of-thermal-reversal-of-the-fulvalenetetracarbonyl-diruthenium-photoisomerization-toward-molecular-solarthermal-energy-storage&Itemid=57 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
  - seigenblues 16y ago
    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.

seigenblues 16y ago

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 :)

tbrownaw 16y ago
I think I found the actual paper: http://zeppola.mit.edu/pubs/FvRu_Thermal_Reversal_AngewChem.pdf http://zeppola.mit.edu/pubs/FvRu_Thermal_Reversal_AngewChem.... [ http://zeppola.mit.edu/index.php?option=com_joodb&view=article&joobase=3&id=70:mechanism-of-thermal-reversal-of-the-fulvalenetetracarbonyl-diruthenium-photoisomerization-toward-molecular-solarthermal-energy-storage&Itemid=57 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
- seigenblues 16y ago
  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.