Solar Power Answers
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System Design

Getting the design of the system right is key to ensuring both reliability of supply and minimum cost. A little time spent in accurate estimation of energy consumption and planning the installation wil pay dividends in the future. The calculators on this page will help in the process of building the optimum solar power system for your needs.

Solar Panel Sizing

loads calculator If you followed the advice in the energy section, you will have reduced your electrical energy requirements to a bare minimum. The next stage is to use these to calculate the daily energy requirement. Start the loads calculator and follow the instructions to calculate your daily energy requirement.

array size calculator Next, start the array size calculator. Enter the daily energy requirement and select the seasons you will be using it in. The result tells you the amount of solar generation needed in Watts peak. For example, if the answer is 100 Wp, then you need two 50 Watt solar panels, five 20 Watt panels or any other combination that adds up to 100 Watts. The actual panels to be used may be determined by their availability, the area available to you or other considerations.

battery calculator Now you can size the battery. First you have to decide on the system voltage. A simple rule of thumb is this: If there are 12 Volt loads or it's a small system (a few hundred Watts), make it 12 Volt. Otherwise make it 24 Volt. Only think about 48 Volts if you have telecoms equipment to power or it's a very big system, at least 1 kW (1000 Watts).

To size the battery, use the battery calculator. You'll need to use the daily energy requirement calculated earlier.

cable calculator Only one big thing left; cable. If the major components are a long way from each other or the loads, you may need substantial cable to avoid loss of power. Decide where the components are going and use the cable calculator to work out the size of the major cables.

Other Components

Now that the major system components are in place, all that remains is the simple matter of sizing the:

  • Charge Controller and
  • Inverter
It is possible to do without a charge controller only if the battery is very large relative to the solar panel array. An example is the "Battery Saver" panels designed to plug into a car cigarette lighter. Otherwise, add up the short-circuit current of the solar panel array and use the next largest controller.

Apart from a few wiring tips, you are now ready to buy the parts.