The battery and inverter components are the two most important part of any renewable energy system, whether utilizing solar, wind, hydro or wood gas, The battery bank is required to store power as it is received from one of the renewable energy systems. Solar panels only generate power when there is sunlight, wind turbines can only generate power when the wind blows (at certain minimum levels), and hydro electrical is dependent upon the flow of the water, A wood gas / generator can only provide power as long as it is creating wood gas (generally 5-8 hour runtime intervals). A battery bank of sufficient size and capacity is required to store power for the required needs. The type and size of the battery bank will be dependent upon the specific power needs of the user. The battery bank will typically be in 12, 24 or 48 volts direct current (DC) configuration.
To convert the DC power as stored in the battery bank to usable power for household applications, it must be converted to AC power (110/220 VAC). This is the normal power system you have in a standard household. To convert the DC power to AC power, an inverter is used. Again, the inverter must be of the appropriate size to provide the amount of AC power need for the household or off grid application, The inverter also charges the battery bank from the power received from the external power systems (solar, wind, hydro, wood gas) , when avaialble.
The inverter is the second most important component of a power system. The inverter must be sized to match the user power requirements and the size of the battery bank. The inverter must also be rated for continuous use, as it will be converting the DC power from the battery bank into AC power for continuos useage in the household or offgrid application. The inverter will also maintain the battery charge level as power is received from external sources (i.e. solar, wind, hydro, generator, etc.)
The inverter is connected to the main AC electrical panel of the household or Off Grid application and serves to provide the main (in case of complete Off Grid) or backup (in case of Grid Tie or emergency backup) AC power .
There are several type of batteries available, but these can vary greatly in cost and affordability. The most common types of batteries include:
Flooded lead acid batteries are the most common and mostly used batteries for off grid power applications. They require a certain level of manual maintainance in monitoring water levels and electrolyte. Flooded lead-acid batteries are also the most affordable and cost effective. The sealed lead-acid batteries do not require maintenance of water levels or electrolyte, but are more expensive than flooded batteries. AGM (Absorbed Glass Matt) batteries are a form of sealed lead-acid batteris that also do not require maintenance but are more expensive than standard sealed lead-acid. Lithium batteries are also available but are rarely used given their high cost.
Batteries are typically available in 2, 6, 12, 24, and 48 volts (DC). Batteries may be wired in serial or parallel to achieve a desired voltage and Amperage (Amps) rating needed for a specific off grid power system. This voltage and amp rating can be determined through a 'system sizing' exercise in which the user determines the power needed to meet all of the user power requirements.
Battery life expectancy must also be taken into consideration during the selection of a battery bank. Batteries can last anywhere from 1 to 20 years. Sometimes buying an expensive battery that will last 20 years is more cost effective than buying cheaper batteries that will have to be replaced every 2-4 years
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