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
You need to calculate your daily energy requirement. Start the loads calculator and follow the instructions to calculate your daily energy requirement.
Next, start the array size calculator. Note: This calculator is designed for UK conditions and our solar radiation is much higher in New Zealand particularly in Northland. 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.
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.
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.
Now that the major system components are in place, all that remains is the simple matter of sizing the:
1. Charge Controller
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.
If you have electrical experience then wiring up your solar power system should be straightforward. Although the wiring is likely to be more complicated than normal mains wiring, all the principles involved are the same. We recommend you utilise the services of a qualified electrician in installing your system.
The DC wiring may be the whole system or confined to the battery room. Every system is different, but here iare diagrams for a typical 12 Volt lighting system and 230 Volt system to help with the wiring design. The cable sizes can be calculated using the calculator but be aware that the low-voltage DC cables will need to be larger than you are used to. Normal mains wiring accessories can usually be used at their rated current at up to 30 Volts DC. You will also need some specialised low-voltage parts such as battery clamps which can be obtained from us.
This wiring diagram is an example of the type of 12 Volt lighting systems that are common in homes throughout the developing world. It relies on the controller to provide fusing and battery protection, so you should choose a model of controller which incorporates these functions. Note that the battery negative terminal should be earthed for electrical safety.
The AC wiring is just the same as in any mains installation. It is very important that the manufacturer's instructions are closely followed when installing the inverter, especially with regard to earthing requirements. Always ensure that the AC and DC circuits are kept entirely separate.
This wiring diagram is an example of a system of about 500 peak watts which is designed to give a 230 Volt output to power normal mains appliances. The DC wiring is configured for 24 Volts, so as to reduce cabling and controller costs. It assumes that the inverter has a low-voltage disconnect function to protect the batteries from over-discharge. Note that the battery negative terminal and the consumer unit should be earthed for electrical safety. Also note the separate battery fuse which is necessary owing to the potential for very high short-circuit currents.