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More on Storage
July 13th, 2009
Alright, so you've got a solar panel or wind turbine built, now what do you do with all of this power you're generating? You can't always use it right away, and sometimes you're generating it in the middle of the night when you're not using much power at all.

Most solar systems use a battery bank to store energy over short periods of time, until it can be used. For many home renewable energy systems, this is probably the best option. The storage system in this case consists of three different parts:

1. The Charge Controller

Because your renewable energy source doesn't always provide the same amount of power to the batteries, connecting it to them directly would be disastrous. For this reason, a charge controller is used to charge your batteries, and keep them at the right level.

When you choose your charge controller, be sure that it is the right one for your system. It needs to have the proper voltage and current ratings and also enough connections for your entire system. Some charge controllers can even be connected to the grid, so that you can sell your power back to the power company and reduce your bill even further! Be careful with this feature though, sometimes these controllers will also charge your batteries from the grid when the renewable source isn't creating any power, and that will cost you money.

2. Batteries

Batteries come in many shapes, sizes and ratings. Be sure that you choose the right batteries for your application. Although you may think that car batteries are the best, they are actually some of the worst batteries for a solar power system. If you choose to use a series of them, you will be sorely disappointed because you'll be replacing them after mere months.

Most "deep cycle" batteries are not suitable either, however many DIY alternative energy systems use batteries such as golf cart or marine batteries and they last a moderate amount of time. However typically, purpose-designed batteries are best.

Absorbent glass mat batteries are the batteries of choice for indoor battery banks. They are no-maintenance and do not require venting like flooded lead-acid batteries do. They carry the electrolyte in glass mat between the plates, it is absorbed into the spaces between the glass fibers and thus can't leak out.

3. Inverter

Since many people are looking at off-grid living these days, the inverter plays an important role in this venture. Inverters come in many shapes and sizes, however there are three main types:

Square Wave Inverters
Quasi-Sine Wave Inverters and
True Sine Wave Inverters

Typically, inverters used for camping that connect to a car's cigarette lighter are square wave inverters. They are the least expensive type, but do not produce "clean" AC. A square wave is fine for certain appliances, however many newer appliances and electronics utilize timers and motors which require AC which very closely approximates a sine wave.

Quasi-sine wave inverters are the most economical choice for DIY power systems. They produce AC power which is between a square wave and a true sine wave. They come at a moderate cost, but are suitable for most applications, including computers and televisions. For very advanced and expensive applications, only a true sine wave inverter will do.

True sine wave inverters produce very clean AC power and are the best apprixmation of a true sine wave. However this accuracy comes at a cost. They are by far the most expensive inverters.

Inverters can also connect to the grid, and more than likely if your system is grid-connected, this is where you want to do it. The power company doesn't like you selling them anything but 60Hz (or 50Hz in Europe) AC power.

If you'd like more information on these and other green energy topics visit Home Energy Focus for a series of guides to DIY green power.

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