How Solar Photovoltaics Generate Power

Solar power works by converting energy in sunlight into an electrical charge or current. When sunlight hits an object this energy is typically converted into heat and light. When directed or captured by a solar panel (photovoltaic) this energy is captured by the photovoltaic material which may be silicon or copper-indium-gallium-selenide. Solar panels are designed to reach as high an efficiency as possible are coated to reduce glare with an anti-reflective coating.

The way in which a solar panel turns sunlight into electricity is through these crystals and what’s known as the photoelectric effect (discovered by Albert Einstein in the early 1900s). This is what causes the crystals to absorb photons of light and release electrons. When these free electrons are captured, an electric current is produced which can be used as electricity.

For solar cells, a thin semi-conductor wafer is specially treated to form an electric field, positive on one side and negative on the other. Electrical conductors are attached to both sides to form an electric circuit. This electricity can then be used to power a load such as a light or tool. If the system is large enough it can be used to power a whole building and can be fed back into the mains utility transmission system (if permitted in a particular country and if the correct equipment is installed to comply with regulation). The electric current produced is proportionate to how much light strikes the panel. A photovoltaic module (solar panel) is comprised of a number of solar cells, electrically connected and mounted in a support structure or frame. Multiple panels can be wired together to form an array. In general, the larger the surface area of an array, the more electricity it will produce. They can be connected in both series and parallel electrical arrangements to produce any required voltage or current combination.

In explaining how solar works, we need to mention electric current. The electricity generated by a solar system is direct current (dc) so an inverter has to be installed to convert it into alternating current (ac), which most electrical appliances and equipment can use. Other hardware that makes up a solar energy system are wiring, junction boxes, grounding and earthing equipment, overload protection, ac and dc disconnects and so on. Electrical codes must be followed and in many countries the installation has to be carried out by a qualified and licensed electrician.

Solar panels that are typically found on a domestic house are around 20% efficient. Some can be as low as 10% and some (although not the ones generally used domestically) as high as 50%. Inefficiency in domestic solar installations has been addressed most recently with the introduction of multi-junction cells (also known as cascade or tandem cells), which can achieve higher total conversion efficiency by converting more light to electricity. Typically, the efficiency of a cascade or tandem cell is around 35%.

Often, during daylight hours, a solar system will collect more energy than is needed to be used straight away so, some kind of energy storage may be attached and this can be in the form of batteries. More often these days, solar owners are connecting to the utility grid so that they can sell back whatever surplus power they don’t use to help pay for the solar installation. Given the right conditions, this type of renewable power system set up usually pays back the cost of installing the solar panels within 10-15 years.