# How to store electrical energy?

## Main Question or Discussion Point

Hello

I made a little wind turbine so when it is directed at wind it turns and generates electricity as I can see the outcoming voltage on voltmeter. My question is how can I store its energy?
Can I use a rechargable battery and let it run out, then stick copper wires at each sides of it coming from the terminals of the turbine; so that perhaps the battery charges again?

Thanks

## Answers and Replies

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tech99
Gold Member
Hello

I made a little wind turbine so when it is directed at wind it turns and generates electricity as I can see the outcoming voltage on voltmeter. My question is how can I store its energy?
Can I use a rechargable battery and let it run out, then stick copper wires at each sides of it coming from the terminals of the turbine; so that perhaps the battery charges again?

Thanks
Yes. The battery needs to be connected with + to the positive generator terminal. You need to make sure the battery is suitable for the generator. I am guessing the generator is a little unit, about 1 inch diameter, so how many volts does the generator give? How much current does it give on the ammeter range (short circuit conditions).

While recharging a battery would be the most practical way - you may also find it interesting to look into hooking up a flywheel - this is a wheel that the fan connects to with a one way ratchet mechanism and possibly some gearing to obtain faster momentum. The fan starts the flywheel spinning while there is wind available - then during periods without wind when the fan slows down (due to air resistance on the blades) the ratchet allows the flywheel to continue uninterrupted thanks to conservation of angular momentum. This rotational energy (minus losses due to air resistance and bearing frictions) is stored until needed and then utilized by drawing off electrical energy through a generator.

CWatters
Homework Helper
Gold Member
You might want to put a diode between the turbine and battery so the battery doesn't spin the turbine when the wind stops.

No. Don't just hook a battery to a wind turbine.

Batteries can be particular about how they are charged. Charging them too fast can cause them to explode. Wind turbines have highly variable power outputs.

That said, batteries are the common choice for small systems. But you will need some sort of charger/controller to do this safely.

How big is your turbine?

First -- charge into a capacitor, or a small bank of them ( is your generator putting out AC or DC ? - If AC you will need to rectify to DC first - that is a basic circuit however). This will filter and store a relatively small amount of energy, however will give you a basis for learning about your generator. From there you now have a more stable DC source, you could look into a DC to DC battery charging circuit to do the bulk storage.

anorlunda
Staff Emeritus
In addition to the amount of energy stored, the other critical parameter is for how long you need to stor it. Capacitors, flywheels, batteries: each has advantages for differnt time periods.

If you want to store several kWh for half a day, then lead acid deep discharge batteries may be best.

If you are running LED lights from a wind generator, and you want to reduce illumination variations every time the wind gusts, then capacitors may be best.

In all cases, as Jeff said, you will need a charge controller.

Where it works it is great. But there are few areas where this will work.

It needs a high altitude lake. It's less useful in plains, deserts, or off coasts.