Solar energy is safe and environmentally friendly due to the lack of emissions. The sun is the source or “fuel”.
But how do those solar panels on roofs create electrical power? They are the first component in a complex network that utilises the sun’s energy to deliver electricity to the building underneath.
How solar power works
Each solar panel is made of a metal frame, a layer of silicon cells, a glass casing surrounded by a special film and wiring. The solar cells are known as photovoltaic cells and absorb sunlight during daylight hours. Panels are grouped together for maximum effect and placed on rooftops or in large outdoor spaces into an ordered series.
In each photovoltaic cell is a thin semiconductor wafer made from two layers of silicon – one positively charged, and the other negatively charged to form an electric field. As light energy from the sun strikes the photovoltaic cell, it energises it and causes electrons to ‘come loose’ from atoms in the semiconductor wafer. The electric field surrounding the wafer set the loose electrons into motion which creates an electrical current.
A typical solar module comprises 36 cells connected in series to produce an operating voltage of 12V.
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Solar panels transform sunlight into direct current (or DC) electricity, but the type of electricity that powers homes is alternating current (or AC) electricity, hence DC electricity is changed into AC electricity by an inverter, which, in modern solar systems, can be configured as one inverter for the entire system or individual microinverters attached behind the panels.
Once the solar energy is converted from DC to AC electricity, it runs through an electrical panel and is distributed within the home to power appliances, exactly the same way electrical power is generated through the grid.
On cloudy days and overnight, solar panels may not be able to capture enough sunlight to use, while in the middle of the day they may collect surplus energy, therefore 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.
The following requirements are necessary for PV systems:
- High levels of direct sunlight. Areas where there is a prolonged presence of mist or clouds are not suitable and a site should be free of shading from trees, buildings, etc.
- Maintenance requirements on PV systems include checking and topping up of battery electrolyte, cleaning PV panels to ensure optimum exposure to sunlight, checking the charge controller operation and confirming that wiring connections are secure.
The range of appliances that can be used on a PV system include household and school lights, televisions, overhead projectors, radios, microwave ovens, computers, water pumps and refrigerators.
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Advantages of solar power
- Access to inexpensive electric power in remote areas not connected to the national electricity supply network.
- 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 of solar power
- The only real disadvantage is that the energy is not available all the time. Battery storage is needed, and such equipment is expensive.
The way today’s photovoltaic technology can capture the power of the sun to create electricity can be utilised successfully in South Africa since most areas of the country average more than 2 500 hours of sunshine per year, and average solar-radiation levels range between 4.5 and 6.5kWh/m2 in one day.
For more information, visit Livestainable’s website: https://www.livestainable.co.za/.
