Most efficient way to store excess energy

On sunny days, the solar panels are producing their maximum output and they combine with the micro hydro electric system output in the stream on our property to create excess power after the storage batteries have been fully charged

Right now this excess is “dumped” into a 85 gallon hot water tank for showering and other hot water uses.

The home is off grid some we can’t send the excess back to the local power company. At some point we may get a Nissan Leaf and charge it with this excess power.

No, the answer to this question is the same as the answer always is to “would this energy be ‘free’”. There ain’t no such thing as a free lunch. You’re using some power to raise the water, and you get that back when you drain the water, and you’re using some power to raise the float, and you get that back when you lower the float. All that you gain from splitting up the load that way is extra complexity, for no advantage.

Having the floater with the weight would cause the overall level of water (for the same volume of water) to be higher (proportionate to that weight), thus making the pump work harder to pump the water in. Yes, you would get back more energy, but you would also have to expend more to begin with.

Could we pull H2O and CO2 out of the air and make fuel out of them? Plants have been doing exactly that for millions of years.

I like the idea of using the electricity to generate other resources, if we don’t need it to power our TV sets: generate hydrogen for fuel cell vehicles, run desalinization plants or build more of those water 'vaporator billboards to supply fresh water.

Yes, but IIRC, it took them 200 million years to work out how to do it. :slight_smile:

Yes, this is absolutely physically possible, the chemical pathways for doing this are well known and have been used for decades in various forms. (http://www.patents.com/us-7420004.html)

The problem is that it takes an immense amount of energy to synthesize liquid hydrocarbons out of thin air, and using liquid hydrocarbons in an IC engine is also pretty lossy.

So this sort of thing will probably always only be a niche process, where the ability to synthesize liquid fuel on site with no need for other chemical feedstocks is important–such as, a nuclear aircraft carrier in the middle of the ocean that can synthesize jet fuel rather than rely on a constant stream of tankers.

You’d probably be better off just making hydrogen. The problem is storing all that gaseous hydrogen, which is a pain in the ass. A storage chemical that is liquid at shirt-sleeve temperatures is much easier to handle.

Your best bet would probably be making H2. Not the most efficient per se but it doesn’t run into obvious limitations and the byproduct is marketable in itself.

Relevant article on role of vanadium in flow batteries, as well as mentioning supply/demand issues for vanadium.

A few folks mentioned H[sub]2[/sub]. Some countries are doing this and pumping the hydrogen into the existing natural gas infrastructure. There are huge inefficiencies here, and hydrogen leaks horribly, but it uses existing infrastructure and increases the heating value of the gas going to the existing NGCC power plants.

Electrons are cheap, and it’s hard to make money by inefficiently storing something with little value to begin with.

One avenue is catalyzed thermochemistry:

… and bio-engineering of algae:

… and other methods (might be a pay-wall on this one):

Big Oil is backing a lot of this research. Three cheers for Big Oil!

I have often said that if we really cared about the environment we wouldn’t be spending hundreds of billions of dollars on not-ready-for-prime-time solar and wind technology … we would be spending tens of billions of dollars on research. But nobody ever listens to me.

I would like to learn about banks offering 2% loans and the companies that are using the quoted business model. Please tell us more.

j_sum1 also mentions the value to power companies. I am not aware of any current opportunities that would allow a homeowner with modest storage capacity to participate in peak shaving, but keeping the grid balanced has a cost, and home storage could be an economical part of the solution. Just not yet.

The business model certainly exists although I don’t believe it can possibly work at present without either a fat government subsidy for rooftop solar or coercion of the utilities to produce a minimum level of renewable.

For instance, in Ontario

I don’t know what kind of deal they’ll be offering now that the MicroFIT price schedule has been drastically reduced - it is now half the original rate

There were similar opportunities in Germany and Spain, but I understand that the subsidies have been sharply reduced since the Credit Crunch and assume - perhaps unwisely - that the gold rush has finished there as well.

In the US, one such firm is Duke Energy, but in this case the impetus came from the stick, not the carrot:

… and their attempts to cash in on the programme themselves has been fiercely criticized:

It nearly always works like that though - a technology doesn’t have to be perfect to be rolled out, just good enough - and current wind/solar technologies are good enough, for now.

If we waited until technologies were mature before rolling them out, the world would be a very different, much less advanced place than it is today.

And just where do you think those hundreds of billions of dollars are going? Research on alternative energy technologies (of all sorts) is done by the companies that make them. They get their funding for that research from the technologies they’re selling. Thus, “spending money on not-ready-for-prime-time technology” is spending money on research. Plus you get the benefit of those almost-ready-for-prime-time windmills.

It is true that technologies don’t have to be perfect to be rolled out, largely because perfect technologies are hard to come by.

Whether or not wind/solar technologies are good enough is an assertion that is open to dispute.

As the Master states:

As for solar, even the big boosters can’t make a case for it:

And those ‘falling installation costs’ … is that because of improved production technologoy and economies of scale? Nope:

So Western subsidies for consumers are supplemented by Chinese subsidies for producers. The technology simply isn’t there yet. This is craziness.

As far as other technologies are concerned … I have been unable to think of any other technology that has been introduced on a widespread basis through the use of government subsidies. Smart phones, cell phones, the Internet, computers, electric power, automobiles, air travel, telephones, telegraphs, railways … all these were became widespread through people trying to make a buck on the idea’s own merits.

The only instance I could think of that is even remotely supportive of your case was emission controls and fuel economy standards for cars. Did you have any actual examples in mind?

The best approach is research - the DoE’s Sunshot project is laudable:

More of this and less feel-goodism in the renewable industry sector would get us a lot further ahead.

According to the Industrial Research and Development Information System ( a project of the National Center for Science and Engineering Statistics (NCSES) / The National Science Foundation), the “Funds for industrial R&D as a percent of net sales of companies performing industrial R&D in the United States, by industry and company size: 2007” comes to 3.8% across all industries; 4.1% if the sample is restricted to manufacturers.

One will also remember that the manufacturer will only see a fraction of the total cost of the project - much will get soaked up by installation, distribution, transport and sales.

It’s an incredibly wasteful way of funding research.

I take it that Thot is the actual surface temperature of the sun? (and Tcold would be the air on earth around the panel location)

Yes on both counts.

Try fossil fuels.

I thought we were talking about the introduction of technologies.

I have no desire to enter into a political debate; but I will sign off by pointing out the laughable reasoning of the quoted article:

Heaven forbid that oil companies be exempted from paying taxes twice on the same profits, expensing their expenses, or being exempt from price controls! I will point out the enormous subsidy granted to renewable energy by not taxing the producers at a rate 1,507,263%