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Does creating hydrogen from solar energy provide a lesser amount of energy than is extracted from the Sun? Isn't it more efficient to use the electricity being generated by the Solar resource itself?

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Yes, if you want electricity, it's much cheaper and more efficient to just use the electricity directly from a solar panel, than to do any transformation of that electricity into any other form, then back to electricity.

The only reasons that we'd use electricity to electrolyse water to create hydrogen, is if we had spare electricity now, and wanted to store the energy for use later; or we wanted to use the hydrogen as a fuel for transport; or if we wanted hydrogen (or HO, or O2) as a chemical feedstock.

  • Is hydrogen fuel produced more efficient than storing the excess energy in a battery? – vortex_sparrow Aug 10 '15 at 6:19
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    That's a very good question: please do post it as a new question. – EnergyNumbers Aug 10 '15 at 6:31
  • @Air - I don't know which is more efficient, but you have to take into consideration that batteries are expensive, have a limited life, and don't scale well since doubling or tripling storage capacity can be expensive and take considerable space. – Kevin Fegan Aug 20 '15 at 0:36
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I think the biggest challenge to "renewable" energy is answered by asking two questions:

1) When do you want to use the energy?

If you want to use the energy NOW, of course the answer is going to be don't convert it. Use it.

But what about using solar... at night? What about using Wind power... when there is a lull in the wind?

The issue is that Solar doesn't shine all day (in one spot). Clouds cover the sun. Wind doesn't always blow.

During the "droughts" of energy, you need some way to tide you over. Either you need to store your previous extra energy... or you need another source - being tied to the grid for example.

2) What do you do with excess energy?

You've just created 10 units of electricity... but you can only use 5. What happens to the extra 5? Either you a) store the energy somewhere or b) you need to sell/trade via Net Metering.

If you don't store the extra somewhere, you'll lose it. If you lose 50% of it converting it to something else, that's still better than losing 100% of it doing to not storing it somewhere.

If you are connected to the grid, and the local policies (State/City/Electric Company/etc) allow it, look into Net Metering to buy/sell power. Give it to the electric company when you have extra. Buy it from them when you aren't producing. Maybe you can simply owe nothing each month... or you might be able to make money.

The next unasked question would be What is the best way/place to store energy

If
... you aren't connected to the grid
... the Net Metering options aren't beneficial for your situation
... you just don't want to sell

Then: what route should you take to store the excess energy? Batteries? Hydrogen? Pressurized air? Tons of options exist to "store" - and they all have different pro's/con's.

But "I need this energy later" and "I generate more than I use" are two very solid reasons to store it somewhere/somehow.

  • I understand your answer for an 'off the grid' situation. Currently, doesn't excess power just spin the meter in reverse? In effect, just supplying it to those who need it, with no loss in trying to store it. – JoeTaxpayer Aug 10 '15 at 15:03
  • I'm not real knowledgeable about it, but I would look into Net Metering. That article seems recent, and has some good pointers on where to start learning. I think a large point is it depends on where you live, your particular electric company, country/state/county laws, etc. – WernerCD Aug 10 '15 at 15:22
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    @Joe maybe it does, maybe you forcefully sell excess electricity to electric company, maybe you break your contract with that company. Depends where you live and on contracts/laws. But only thing what it does is pushing problem of uneeded power up (but there is chance that someone else needs it). And often its power with wrong phase, which is actually harmfull (warms up wires and does not do work). And because of these concerns, this causes GREAT problems in europe where north germany produce lot of wind power when it is not needed or at least where it is not needed. – Alpedar Aug 10 '15 at 15:37
  • Yes - net metering is what I was referring to. @Alpedar - in many parts of the world, it's common, and regulated. And until there are so many customers doing it, it won't be a problem. Of course, if more than half of households did this, there would be too much excess power to consume. We're far from there right now. – JoeTaxpayer Aug 10 '15 at 15:41
  • Yeah, the little I've looked says it depends greatly on your location/situation. Even if you are connected to the grid, some companies don't buy/sell. Some won't pay for more than it takes to bring you to a bill of zero. A zero bill could be enough for you - and simple enough - or you could look into other ways to use that energy. Or you could try to do like the examples I've seen and pull in some extra cash. – WernerCD Aug 10 '15 at 16:14

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