Photovoltaic (PV) or solar modules are made up of solar cells that are connected in series. The most common commercial cells are made from purified Silicon (Si). The Silicon cell is essentially a p-n junction that utilises the energy from the sunlight to generate electron flow from the p-type Si (via an external resistance) to the n-type Si. A typical solar module comprises of 36 cells connected in series to produce an operating voltage of 12V.
PV systems often include a battery bank for energy storage, and a charge controller that regulates the power flow into and out of the battery bank. Battery banks are typically sized in order to provide energy during days of no or limited sunshine (cloudy/rainy days).
The following requirements are necessary for PV systems:
* High levels of sunlight. Areas where there is a prolonged presence of clouds or mist are not suitable for PV systems. However, South Africa has one of the highest solar irradiation levels in the world.
* Direct sunlight is required for the PV panels. This means that the site should be free of shading from trees, buildings, etc.
Maintenance on PV systems include checking and topping up of battery electrolyte, cleaning the PV panels to ensure exposure to direct sunlight, checking the charge controller operation, and ensuring that the wiring connections are secure. Typically user maintenance is performed every month and preventative/corrective maintenance visits to the site are performed every six months on larger systems.
Client usage options
The range of appliances that can be used on a PV system is as follows:
* Household and school lights
* Overhead projectors
* Microwave ovens
* Water pumps
The main benefit is access to inexpensive electric power in remote areas not connected to the national electricity supply network. Schools in remote areas in particular can make use of electronic media as a result of this technology.
Advantages: Solar power is renewable, clean and has no direct emissions. Solar panels can be used almost anywhere in South Africa and are suitable for low energy use such as lights and television.
Disadvantages: Without battery storage, the energy is not available all the time and the equipment is expensive.