Email chat about batteries and how to store wind energy

answering another email today…

Hi Ruth,

I have just come across your website (whilst looking for a feeder for bees, of all things!) and have not yet had time to check out all the links, so I apologise if my question is already answered somewhere.
What I would like to know is if it is possible to store the energy produced by a wind turbine somehow, other than in a battery?

Yes, but the battery is still probably the best option for small stand-alone (off-grid) systems. Nowadays the biggest market is for grid connected systems that ‘use the mains grid as a battery’, but I live off-grid and I like being independent. So I do use batteries and I also use a generator for back up if the wind is not sufficient (like recently).

The biggest argument against wind turbines that I keep hearing is that they only work when the wind blows,

Yes I would say that this is their biggest weakness. They only work about 80% of the time, and for part of that time they do not produce very much output. The wind is very fickle. So a lot of the energy comes when you do not need it, and there are also times when you do not get what you need. But it’s a natural commodity and a bit wild, and I love it.

and when it doesn’t blow you have no electricity.

Well in a properly designed system you will have solar photovoltaics, and batteries, and a generator for backup, so that is not at all true, no.

What I would like to see is the energy produced by the turbine being stored in some other way than a battery.

Me too, but I have not seen any good options yet. Except for the grid of course. But that’s more like trading than storage. The grid is a good option for mixing up different energy sources to produce a blend that offers the best of them all. But I like being independent personally.

My understanding (admittedly extremely dodgy) is that the electricity a turbine generates is AC, which is then converted to DC to store it, and then usually converted back to AC to use it, all of which is extremely inefficient.

Not that bad. Overall in my system, it’s about 85 % efficient.

(Also batteries aren’t exactly ‘green’).

No, they are not, I do agree with you there. Lead is a very toxic chemical. But it’s there to be used and there are worse things in the world. For a long time people actually got their drinking water out of lead pipes and survived. It can be recycled. Sulphuric acid is biodegradable and no real problem.

Would it not be possible and more efficient to store the power in some other form,

I doubt that. All of the other forms of energy storage I have looked into are really inefficient on the small scale. Pumped storage of water in reservoirs is good on the large (grid) scale but not so efficient in small systems unfortunately.

for example like a clockwork radio that stores power in a spring, gradually releasing it on demand.

The motor and the generator to do this in small systems are not very efficient compared to a lead-acid battery.

I don’t suppose that a giant spring would be a suitable store,

It would have to be big. Pumping water up to a high reservoir is better. It works really well actually.

but I was wondering about using a turbine to compress air, storing that, and then using the compressed air to drive a turbine to produce electricity on demand. Is anyone doing anything similar to this at the moment?

It’s a nice idea but unfortunately the air gets hot and then as it cools it loses much of the pressure and thus the energy. Again it’s more feasible on a (very) large scale where you can keep the heat in. I believe that something similar is done to augment the power from steam turbines with stored energy. Using old oil and gas wells and the like to store compressed air.

Not being at all technically minded, I am sure that there are a lot of problems that I haven’t thought of, such as storing the compressed air itself, but I am sure that there must be a more efficient way of using a wind turbine, so that instead of there being lots of NIMBYs, everyone will want one!

I have come to the conclusion that NYMBYs will be negative whatever you do. Using natural renewable energy is beautiful for me regardless of the problems, but some people will not be happy until it is totally cheap and reliable and convenient, and free of any possible downside. Until then they will go on burning up the resources of the planet and leaving nothing for future generations. And they will laugh at the idea of using ‘ugly, inefficient’ wind turbines. I don’t understand their logic.

Until 100 years ago we used the wind to power a lot of things, but since then we have burned a lot of stuff because it is easier to get energy fast that way. However this is not sustainable. A lot of people don’t seem to get this obvious fact.

My own little dream is to have a wind turbine to compress the air, then to have a car that runs on compressed air. Just pipe dreams or not?

It’s feasible. But I would recommend batteries if you want something practical. Lithium batteries for that actually. It’s not just a dream. But it does need people to believe in it or it may continue to appear to be one.

Also you need a proper wind turbine on a tall tower or pole to catch a proper wind and not just a toy on the roof. There is no real wind at the rooftop level.

have fun