Energy Storage for Alternative Energy Systems, Part One of a Three part series

July 12, 2009 - PRLog -- Energy Storage for Alternative Energy Systems, Part One of a Three part series

Anytime you are considering the installation of an alternative energy source, one of the factors you must take into account is the storage needs relative to the energy use intended for the alternative energy source. This is true regardless of whether it is a solar energy system or a wind generator. The following is a series of article that create an overview of energy storage through the use of batteries and some of the option and considerations you will need to focus on as you progress toward energy independence.

Alternative Energy Storage-Part One:

Battery Size
Now don’t go to sleep on me! This stuff can tend to get a bit on the technical side but believe me, I’m no techie so this will be in terms that even I can understand. Hang in there, this really is pretty simple and once you get the concept, it will be easy. This is an important step in acquiring a knowledge base necessary to be successful as an energy independent homeowner, so just hang on and let’s learn together. I’m going to give this to you a small piece at a time so you don’t get overwhelmed.

When designing a homemade solar or wind power system, the size of the battery storage bank will depend on the amount of storage capacity required. This along with the maximum charge rate, maximum discharge rate, and the minimum temperature at which the batteries will be used are all factors to be analyzed. By determining the one requiring the largest capacity we will establish the battery size. Don’t stop here, you can do this…..
Remember, the batteries are typically a DC system and the energy needs (appliances, lights etc.) are typically AC. So we need to learn the relationship between amps and amp-hour requirements of 120 volt AC items versus how their usage impacts the DC low voltage storage batteries. There are some specific formulas and details about how to do this accurately on our website. The easiest way to quickly estimate the total battery amp hours required is to first determine total watt-hours required by all loads, and then divide by the nominal DC system voltage. This resulting number will be an indicator of the amount of amp hours needed to operate all loads for a given period. Then you should calculate additional amp hour capacity for "reserve" capacity to prevent complete discharge.

There are other factors for determining the full extent of the battery drain, such as temperature, start-up factors, etc., but this should help you get a more complete picture on how to size your low DC voltage batteries when powering 120/240 volt loads using an inverter. For example, temperature has a significant effect on lead-acid batteries. At 40°F they will have about 75% of rated capacity, and at 0°F their capacity drops to about 50%. The storage capacity of a battery, the amount of electrical energy it can hold, is usually expressed in amp hours. If one amp is used for 100 hours, then 100 amp-hours have been used. A battery in a solar power system should have sufficient amp hour capacity to supply needed power during the longest expected period "no sun" or extremely cloudy conditions. In wind systems allowance for "no wind" days should be included. A lead-battery should be sized at least 20% larger than this amount. If there is a source of back-up power, such as a standby generator along with a battery charger, the battery bank does not have to be sized for worst-case weather conditions.

This is Part One in a series dedicated to Storage batteries for Homemade Alternative Energy. If you are considering a DIY solar energy or wind energy system, watch for our next article about how to properly install a battery storage bank.

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