Solar thermal collectors are modular and either ‘building integrated’, i.e. forming part of the cladding system, or ‘bolt on’. Arrays are typically pitched at about 30º and orientated between southeast and southwest, and it’s important that overshadowing is avoided. In Ireland heat exchangers are used to transfer the heat collected from the solar collector circuit to the hot water store or circuit. The two main types of solar collectors are flat plate and evacuated tubes. The main difference between the two technologies is that evacuated tubes while more expensive, are able to achieve higher efficiencies, requiring less space on a roof to achieve the same energy yield.
Solar Photovoltaic (PV) technology works on the principle that energy from the sun is converted to electricity. PV cells are used to convert solar radiation into Direct Current (DC) electricity. The DC electricity is then inverted to AC electricity for use in buildings or for export to the grid. A PV cell consists of one or two layers of a semiconducting material, usually silicon. When light shines on the cell an electric field is created across the layers, causing electricity to flow. The greater the intensity of the light is, the greater the flow of electricity. So even on cloudy days diffuse sunlight will produce electricity but less than on clear sunny days.