Photovoltaics

Larger photovoltaic installations currently provide electricity for homes and commercial buildings, but there is also an increasing tendency to use smaller systems to provide electricity for pumps, road signs, telephone boxes and streetlights. An innovative approach to their use and rapidly developing technology will be the key to its success.

At a simple level, photovoltaic cells convert sunlight directly into electricity by the interaction of photons and electrons within a semiconductor material. To create a photovoltaic cell, a material such as silicon is doped with atoms from an element with one more or less electrons than occurs in its matching substrate (e.g., silicon). A thin layer of each material is joined to form a junction. Photons, striking the cell, cause this mismatched electron to be dislodged, creating a current as it moves across the junction. Through a grid of physical connections, the current is gathered. Various currents and voltages can be supplied through series and parallel arrays of cells.

Solar Thermal

Solar Thermal systems collect the heat from sunlight to produce hot water, heat, or electric power. Solar Thermal differs from Passive Solar in that a mechanical device distributes the heated water or air throughout the building.

Solar Power water heating systems are the most popular form of solar energy. Low-temperature systems are installed on roofs which are preferably south facing and the system is then connected to the hot water system. Medium temperature systems heat either air or liquid as a heating conductor and are used to provide space, water, and process heating. These usually consist of flat-plate collectors: large, flat boxes that are dark inside, with one or more glass covers.