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Comment by jbri | Hacker News Reader

Earth receives about 1.3 to 1.4 kW per square meter from the sun (and that's before the atmosphere absorbs and reflects a huge chunk of that) - which is effectively an upper bound on the energy that can be produced by any solar power source. A playing-card sized device is going to take more than a day to produce a day's worth of electricity for a current developed-world lifestyle, even if it were 100% efficient.

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Solar panels are already good enough that they are used in developed countries such as USA and UK. Are they perfect? No, they cost too much, and they don't generate enough electricity, but they are used none-the-less.

By the sound of it, this new creation would be more efficient, either in price, electricity generation, or both, than traditional solar panels - if that wasn't the case, why on earth would any project use them in third world countries, when they could instead use solar panels.

So, based on those two facts, surely anyone who would be using solar panels ought to look to be using this product in the next few years? (And, depending on how much better than traditional solar panels it is, possibly more people/companies would want to use it than are willing to use solar power right now.)

>>Solar panels are already good enough that they are used in developed countries such as USA and UK. Are they perfect? No, they cost too much, and they don't generate enough electricity, but they are used none-the-less.

Does no one follow energy news, except for oil prices and the Polywell project?! :-)

Many estimates talk about soon reaching "grid parity" in large parts of the world. If this leaf isn't good enough, there will be some other solar variant soon.

http://en.wikipedia.org/wiki/Grid_parity

It seems to go faster than this prediction from 2009: http://news.bbc.co.uk/2/hi/8386460.stm

(Kurzweil argued in 2008 that solar energy will take over http://www.livescience.com/4824-solar-power-rule-20-years-fu... )

Where do you get your energy news from?

I don't really follow it either, just some tech/science news outlets that waste my time by covering [edit: Energy], too... :-)

BTW one reason that Grid Parity is a moving target is that one of the input costs to making solar power is energy. When energy (hydrocarbon fuel) becomes more expensive, instead of making solar power cheaper in comparison, it has no real effect.

Instead, regular power becomes more expensive, which makes building solar power also more expensive, and the net result is a wash.

That seems weird. That would imply that the lifetime energy capture of a solar panel is roughly equivalent to the creation and installation energy cost.

Indeed. That used to be said of eolic energy (wind power). For example you can see a cost breakdown in 2005 here:

http://www.mnforsustain.org/windpower_schleede_costs_of_elec...

I believe the energy costs are now competitive (but wind still cannot serve as "base" power), but my yet-unresearched hunch is that solar is still at the same stage that wind was: only viable due to the massive tax breaks.

Doesn't seem weird at all, I think. Solar just barely passed breakeven in the last decade, unless you factor in subsidies. I notice that for a random zip code in Maine, http://bpsolar.cleanpowerestimator.com/bpsolar.htm shows that absent federal and state subsidies, you'll save only about $4600 over 25 years with their default settings. It's phrased as saving $36K, though, due to subsidies and interesting presentation. :) But BP Solar really wants you to buy solar panels, of course.

I don't see, in the linked article, a comparison of the efficiency of this device to that of existing solar panels (which are quite a bit more efficient than natural leaves).

> [solar panels] are quite a bit more efficient than natural leaves ...

Got a citation for that? I'd be interested to learn more.

http://en.wikipedia.org/wiki/Photosynthetic_efficiency vs 10% to 30%+ for solar cells (depending on technology/price).

> Solar panels are already good enough that they are used in developed countries such as USA and UK. Are they perfect? No, they cost too much, and they don't generate enough electricity, but they are used none-the-less.

Subsidy and vanity explain a lot of economic activity.

Plus, energy costs are not very uniform. It's much easier/cheaper to get power to the next house in a suburb than it is to get power to a freeway sign 10 miles from the nearest town. That's why solar is cost effective in some situations even when it doesn't make sense in general.

I think the point is that it can use that small amount of energy to break the hydrogen bond in the water, releasing more energy than was used.

Edit: Apparently I made a mistake. See the correction, which I was the first to upvote.

Breaking bonds does not release energy. Bonds are the way the are because they are (locally) the lowest-energy configuration for the atoms that are taking part. You need to put energy in to get out of a low-energy configuration.

The device appears to use water->hydrogen as an energy storage mechanism, to solve (at some efficiency cost) the issue of energy demand generally being out of sync with the supply from the sun. You put energy in to convert water into hydrogen+oxygen, and then you can get that energy back out by converting it back into water.

Since most reactions do not end up with all the constituent atoms as free ions, the real question is how the sum of bond energies of the reaction product(s) compares to the sum of bond energies of the starting molecule(s).

In the case of water, 2 H20 -> 2 H2 + O2 is endothermic, but reactions do not have to be endothermic, or else chemistry would be very boring and cold.

Pisses me off that comments like the one I'm replying to get downvoted. He expressed his understanding of the science, if he's wrong then by all means explain why and upvote those who have explained why - but don't downvote just because somebody made a mistake, it's surely better to have the discussion than for nobody to bring it up.

I won't upvote GP because it contains a factual error and you can't upvote only parts of a comment. If it was edited to include a note about the mistake, thus dismissing the error, I'm sure it'll get get some votes.

I'm not saying upvote incorrect comments, but there is a place inbetween punishing and rewarding.

I sometimes vote such comments towards one, especially if they're only one vote away.

you can't upvote only parts of a comment

Well, that's an interesting UI idea...

What if we covered our houses with them? Instantly I'm dreaming of lush, green cities, covered with the stuff :)

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