A stand alone ( or off-grid) solar power system always combined by solar modules, solar controller(regulator), and batteries. If alternating current(AC) 220V or 110V needed, there also will be an inverter.
The function for each parts:
1.Solar modules: many pieces of solar cells assembled together to create a solar module, this solar module is the hard-core of a solar power system, also the most cost parts. The solar modules absorb sunlight and convert to electricity to store in battery or power the loads.
2.Solar controller (or solar regulator): controlling the working state of whole solar power system, also Protect the battries from over charge and over dis-charge. A good controller also have a temperature compensate function when used in the area with big temperature difference. Also there are other optional function such as timer and photoswithch.
3.Batteries: commonly used the Lead Acid batteries, in the mini systems, also used the NI-Mh, Ni-Cd or lithium battery. It’s function was store the electricity generated by solar modules when there was sunlights, and release it when needed.
4.Inverter, there are only DC 12V/24V 48V from the batteries and solar panels, to power the 220V/110V AC appliance, it is need to converte the DC power into AC power by inverter.
Factors for designing a solar power system:
1. where to use the solar system, how about the solar irradiation condition in the area.
2. Total loading power(KW), and daily consumption(KWH).
3. what will be the system output voltate, AC or DC required?
4. Working time on each day for the solar system.
5. system Backup days in continuous raining and cloudy condition.