The German Photovoltaics Industry
The sun delivers more energy to the earth in just one hour than is used worldwide in one year. This energy can be utilised in many ways, for example with the help of photovoltaics (PV). Thanks to their many years of experience, German manufacturers supply superior quality PV systems and products that enjoy great demand worldwide. As well as being designed and built by Germany companies, ultra modern photovoltaic factories around the world are also fitted with German production equipment. The German quality standard is the key to the professional manufacture of cells, modules, systems and system parts.
Technologies and applications
Photovoltaic cells enable sunlight to be converted directly into electrical energy. In the solar cell, positive and negative charges are separated by radiation energy and collected for use at the two poles of the solar cell, the same as in a battery. In order to achieve greater capacities, many solar cells are combined and connected in one solar module.
- Functional diagram of a solar cell:
1) Negative electrode
2) Positive electrode
3) n-silicon
4) p-silicon
5) Barrier layer
Approximately 85 % of the solar cells in use around the world consist of crystalline silicon, which has proven itself over decades. In the future, there will also be an increase in the reliance on thin-film cells because these can be manufactured more cost-effectively due to their lower silicon requirements or because alternative semi-conductor technologies can be employed. However, they currently offer lower degrees of efficiency, meaning that in comparison with standard modules a greater installation area is required to achieve the same output capacity. When selecting appropriate photovoltaic modules, it is important to consider not only the basic module costs but also the performance cost or cost per kilowatt hour produced (production costs). German companies manufacture both crystalline solar cells and modules as well as thin-film modules of the highest quality in state-of-the-art factories around the world.
Photovoltaic systems also offer the option to generate and use electricity independently of existing power grids. The simplest method of doing this is the direct use of the direct current generated by the solar energy to operate electrical equipment. Photovoltaic cells can, how- ever, also be used to create off-grid island systems. The use of photovoltaic systems in island systems is recommended if the current electricity supply is unreliable. Island systems can be used to supply electricity to remote rural areas which have no access to the power grid. This does away with the high construction costs for building long-distance power grids. It may also be possible to cut back on the fuel (e. g. diesel) required for generating electricity which otherwise may have to be transported over great distances in rural areas.
- Free-standing solar power system
Small, decentralised power grids, so-called mini grids, can supply electricity to everything from individual buildings up to several small towns. In order to feed the supply into mini grids, the electricity must first be converted into alternating current using an inverter. In order to ensure that electricity is available whenever required, even during periods of insufficient solar energy, it is advisable that a storage module (e. g. batteries) is integrated into the mini-grid during construction. Battery-supported PV island systems also provide an un- interruptible power supply (UPS) for countries with unstable, overloaded power grids. A long-term, convenient and cost-effective version of an off-grid electricity supply via island systems is the combination of photovoltaic systems with wind farms and hydropower plants and, if necessary, generators powered by diesel or biofuels (hybrid systems).
The greatest growth worldwide is currently being experienced by grid-connected solar power systems wherein the solar power is converted into grid-compatible alternating current by means of inverters and then fed into the public power grid. Grid-connected photovoltaic systems are available in various power classes, ranging from small systems on apartment buildings with, for example, 1 kWp (kilowatt peak) and a solar module surface area of approximately 10 m2 up to large-scale, free-standing plants with outputs in excess of 10 MWp (megawatt peak) and a total solar module surface area greater than 100,000 m².
Small systems with a typical capacity of 3 - 4 kWp can be optimally integrated into existing buildings. Medium-sized systems producing approximately 30 to 50 kWp are often installed on factories, office buildings, agricultural buildings, schools, town halls and other public buildings.
As a rule, large-scale plants with capacities of several megawatts are constructed as free-standing systems. One of the largest systems in Germany was erected near Leipzig in 2008 and has a capacity of 40 MWp. Owing to Germany's many years of experience in the PV sector, thin-film modules produced solely in Germany were used in this system. The global radiation that has long reached an average of around 1,055 kWh/m² in the Leipzig area enables the power plant to feed approximately 40,000,000 kWh of PV electricity into the national grid every year. In Saxony, this volume of electricity is sufficient to supply around 16,200 households while helping to reduce CO2 emissions into the atmosphere by roughly 37,000 tonnes.