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Types of Solar Installation, Their Benefits, and How They Work

There are two fundamentally different approaches to creating a solar installation capable of harnessing energy from the sun. It is important to understand the difference between them, as one of these options is somewhat limited in terms of what it is designed to deliver.

The first and simpler of the two options, and the one that was the first to be utilised in a commercial application leverages a principle with which most young children become acquainted during their early years at school. Focus the sun’s rays with a magnifying glass onto a piece of paper, and it will smoke, then smoulder, and finally burst into flames. Apply this treatment to water in a test tube, and it will steadily get hotter. A thermal solar installation, as it is known, utilises radiant energy in the infrared region of the sun’s rays to produce heat.

The heat is absorbed via a non-reflective collector and passed to a heat transfer medium, such as air, water, or antifreeze, whereupon it can be used directly to provide heating for residential and commercial buildings. On an industrial scale, gas, oil, or molten salt is used as the transfer fluid to create temperatures high enough to boil water and release steam to drive turbines, indirectly providing the mechanical energy required to drive a generator and produce an electric current. In desert areas where sunlight is intense and the ambient temperature is consistently high, mirrors are used to focus the sunlight, intensifying the production of steam and, subsequently, of electricity.

However, the type of solar installation with which South Africans are more likely to be familiar relies not on the thermal energy contained in its invisible wavelengths, but on the physicochemical properties of radiation predominately in the visible region of its spectrum. The process involved is known as the photovoltaic (PV) effect, and it amounts to a means of converting light directly into electricity, without the need for any intermediary assistance from steam-driven turbines or any other form of mechanical energy.

A PV solar installation relies on the interaction between photons in the sun’s rays and electrons in a semiconducting material, which also acts as the collector. Known as a solar cell, the latter is made from two layers of different, doped semiconductors. The upper, collecting layer is modified to contain an excess of electrons, which can then be readily displaced by incoming photons and conveyed via a wire to the lower layer, which readily absorbs them because it has an electron deficit. The resulting flow of electrons generates an opposing flow of current, which can then be used to perform work.

A single PV cell has an output of approximately 0.5 volts, and so, in order to create a 12-volt supply, it requires 36 of these connected in series to form a panel. For a PV solar installation to provide sufficient electricity to be viable for domestic purposes the individual panels must also be wired together, so as to form an array, typically consisting of about four panels with a combined output of about 48 volts, peaking at a little over 60 volts. Because that output is in the form of direct current, it requires an inverter to convert it to the alternating current at 240 volts required to power standard lighting and electrical appliances in South Africa.

The benefits of leveraging the sun’s energy are manifold. Not only is it essentially inexhaustible and free, but enough of it strikes the earth in a single hour to meet the needs of the entire planet for a year. Accumulated during the hours of daylight, electricity obtained from a PV solar installation may be stored in batteries and used when and if required. In addition to offering home and business owners substantial savings on their monthly bills, panels produce clean energy and require little maintenance.