Solar cells convert sunlight directly into electricity. The heart of every solar cell is a semiconductor, which is mostly silicon and uses the “photoelectric effect”: in some superimposed semiconductor layers, light (photons) generate free charges that can escape as electrons through the electrical conductor. The resulting DC current can be used directly to operate electrical devices or stored in batteries. If converted to alternating current, it can also be fed into the public grid. This is the most common way to use solar energy today.
In Germany, grid-connected photovoltaic systems make a significant contribution to the electricity supply. They consist of a real solar system that supplies direct current in the event of direct or indirect irradiation, and an inverter system in which the direct current can be converted to alternating current and then used directly by household appliances or fed into the grid. The use of onshore wind energy and photovoltaic energy are important pillars of energy supply in Germany today and in the future, as they represent the most cost-effective expansion potential in renewable energy in the short to medium term. Grid-connected photovoltaic systems are funded by the Renewable Energy Law.
In addition, as part of a fuel-independent and low-maintenance system, photovoltaic systems are often a cost-effective solution for autonomous power supply. In countries where electricity networks are scarcely developed, photovoltaic systems are used to supply individual houses, villages or pumps. Typically, a battery and a charge controller are required to overcome radiation fluctuations or to provide solar power when the sun is not shining, such as B. at night.
Solar thermal power plants
In solar thermal power plants, the sun’s rays are combined with focusing mirrors, the so-called concentrating mirror systems. They heat the fluid, which then drives a conventional turbine. Thus, these power plants consist of an innovative part for solar heat production and a traditional part for electricity production. The systems can be used exclusively for power generation or for combined heat and power production, that is, for the generation of electricity and process heat.
Sun-rich areas of the earth are mainly suitable for placing solar thermal power plants, since only part of the solar energy can be used. Only direct radiation can be coupled. The high proportion of scattered radiation and the overall low level of radiation make it difficult to use economically in countries such as Germany.
Solar heating systems, solar panels
Solar collectors convert solar radiation into heat to heat water for daily use or heat buildings. Solar thermal systems are suitable for heating drinking water and for treating hot water for a heating system. Solar thermal systems can also generate cold and process heat. There is great potential in storing solar heat in summer for winter and in distributing hot water to local heating networks.
On January 1, 2009, the Renewable Energy Sources Act came into force. For new buildings, an obligation is introduced to use renewable energy sources in heat supply. This can also be achieved by generating heat from solar energy. Small solar systems are standard in the heating and specialty trade program. Solar energy can also be harnessed, for example, with our own solar collectors or through local or district heating in combination with a large solar central heating system.
Solar heating systems, both small and large, are being promoted through a market incentive program.