I can only say "Holy hot tamales, Batman!" Heat batteries chargeable using sunlight is a huge breakthrough, on par with the discovery of how to store electricity. If they can find a cheaper material to do this, the potential implications are staggering. I wish them the best of luck in their quest.

I expect that it necessarily has rather low efficiency, so it would be best suited for off-grid / low-equipment situations where you care more about heat than electricity. Say you can make a reusable long stip of stuff that you unroll in the sunshine during the day, and then coil up in your tent and "ignite" one end at night and it takes 8-10 hours for the reaction to reach the other end. Or depending on how hot it can get, maybe even a reusable "campfire" that doesn't need fuel and can be a bit safer than a real fire.

>According to Grossman, the next step is “to use a combination of simulation, chemical intuition, and databases of tens of millions of known molecules to look for other candidates that have structural similarities and might exhibit the same behavior.”

That last bit was the most interesting part of the article to me. I've read and studied a fair amount about number crunching to try and figure out the behavior of proteins, but I haven't heard about anyone trying that in reverse and just throwing random chemicals in a simulation and seeing if they have the desired properties. It seems like that sort of chemical simulation for material science would predate folding at home and the like.

Hunt around for references to "computational chemistry." It is a useful tool in the drug discovery world and I would be very surprised if it was not also being applied to material science for very specific targets like this.

I'm becoming increasingly cynical about the way energy "breakthroughs" are reported. It's not the science side - it's great that they've worked out how this compound remains stable after absorbing energy. But you can't present this finding as any kind of breakthrough until they've actually found a compound that exhibits the same effect cost effectively. That they're looking is good. That they now know what to look for is better. But they're still searching. There's no breakthrough.

Let's get real - Ruthenium is about US$5500 per kilogram. You can buy the best lithium batteries on the market for significantly less.

> That they now know what to look for is better. But they're still searching. There's no breakthrough.

http://www.merriam-webster.com/dictionary/breakthrough

3a : a sudden advance especially in knowledge or technique

That they know what to look for now is very much a breakthru, just a "knowledge" one rather than a "technique" one.

> Let's get real - Ruthenium is about US$5500 per kilogram. You can buy the best lithium batteries on the market for significantly less.

Doesn't matter. They actually understand what's going on to some degree, well enough that now they can just throw supercomputer time at it for a while. Maybe they'll find something useful, maybe they'll show that there isn't anything useful.

As a dude working at a solar thermal startup, i would be really excited to see this work. OTOH, solar thermal is already about 30% cheaper than photovoltaics, so that diruthenium is gonna have to be replaced by something really, really cheap...

Our tank losses are nonzero, but in the scheme of things, not all that huge, either. So for it to become cost effective, this storage would have to compete with basically water and glycol in cheap, unpressurized tanks.

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.

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.

"All Earth turned off its burning coal, its fissioning uranium, and flipped the switch that connected all of it to a small station, one mile in diameter, circling the Earth at half the distance of the Moon."

A line from "The Last Question" by Issac Asimov.

Diruthenium ... that sounds even better than dilithium!

Won't work. In the last sentence they basically admit wishful thinking. Can we quit voting up faith-based science articles?

“to use a combination of simulation, chemical intuition, and databases of tens of millions of known molecules to look for other candidates that have structural similarities and might exhibit the same behavior.”

"We learned something interesting, and now we're going to go find out if its easily practically useful or currently just a curiosity."

I don't see how that's "wishful thinking" or "faith-based" or anything like that.

i think the important point, as discussed in the comments at the top, is that they had a genuine knowledge breakthrough. for those of us wishing for immediate technological change, it may not sound like a lot, but for the scientists who have been working on this issue for decades, it is huge. & yes, we don't know yet, but hopefully it will lead to something more soon.

How to store solar energy indefinitely: potential energy of an elevated mass. Done. Is it really that hard? Just use the solar energy to lift something really heavy, and then prop that thing up. It won't leak or discharge for a really long time, depending on what's holding it up.

Heavy things propped up generally have a very low volumetric energy density. Chemical fuels often have four orders of magnitude better energy density. Although I haven't read the original paper, it seems likely that this "fuel" is probably closer to the chemical-fuel ballpark than the propped-up-heavy-things ballpark.

You didn't read the article did you.

So... they've basically invented plants?

No. Plants are living organisms that require (relatively) complex cell machinery to carry out photosynthesis. This is a single molecule that can be "charged" but does not change its chemical composition.

The mechanisms that plants (and animals) use for chemically storing energy are useful for living things, but aren't all that great for long-term, large-scale energy storage. In some sense, we already use plants like that (biodiesel) and, in general, it sucks.

> This is a single molecule that can be "charged" but does not change its chemical composition.

Oh, I missed that part. Very important difference, thanks!