Power from sunlight
The sun delivers more energy to the earth in just one hour than is currently used worldwide in one year. With the help of photovoltaics, sunlight can be converted directly into electrical power for the most varied areas of application.
Technology and applications
If sunlight is incident on the cells of photovoltaic modules, positive and negative charges are separated, which collect at the two terminals of the solar cell, for use as in the case of a battery. The solar cells are connected electrically in order to obtain higher currents and voltages and are packaged weatherproof in solar modules to protect them against the influences of the weather.
There are two types of solar cells. More than 90 % of the solar cells currently employed worldwide consist of crystalline silicon chips. They are either cut from a single crystal rod or from a block with many crystals and are correspondingly called monocrystalline or multi-crystalline solar cells. Crystalline solar cells are approx. 0.2 millimeters thick. On the other hand, so-called thin-film solar cells are thinner than 0.01 millimeters and therefore require significantly less semiconducting material. Thin-film solar cells can be manufactured more cost-favourably in large production quantities, which is why their market share will probably increase in future. However, they indicate lower efficiencies than crystalline solar cells, which means that more exposure surface and material for the installation is required for a similar performance. A decisive factor for investors in the selection of the cells is the cost for a kW-hour of solar power.
There are two types of photovoltaic systems. Grid-connected systems (on-grid systems) are connected to the grid and inject the solar power into the grid. For this, the direct current of the solar modules is converted into a grid-compatible alternating current. However, solar power plants can also be operated without the grid and are then called island systems (off-grid systems).
More than 90 % of photovoltaic systems worldwide are currently implemented as grid-connected systems. As well as the solar modules, they have a power inverter which converts the solar power into a grid-compatible alternating current and injects the solar power into the grid. The power inverter also monitors the functioning of the system and the grid and switches off the system in case of faults.
There exist grid-connected photovoltaic systems in different power classes, dependent on the area of application. Systems between 1 kW and 5 kW power are typically installed on single-family houses, which during one year generate so much solar power that part of or the entire power requirement of the residents can be covered. 10 square metres of solar module area is required for 1 kW of power.
Photovoltaic systems can be built as large as desired. Systems between 10 kW and 100 kW power are mostly installed on schools, public buildings, office buildings, production halls, agricultural buildings etc. In Germany, the largest photovoltaic system installed on a roof has a power output of 5 megawatts (MW). The largest open area system currently constructed in Germany will indicate a performance of 40 MW on completion and a module surface of more than 400,000 square metres.
Grid-separated or island photovoltaic systems are employed in places where no grid exists.
Island systems come in very different sizes. Small plants are employed for the operation of rechargeable battery points, streetlamps, traffic control systems, parking ticket automatic systems etc.
Larger systems enable the structure of systems to be used as grid-separated power generators. Such mini-grids supply current to individual buildings and up to several small towns. For the feed into the mini-grids, the current is first converted into alternating current with a power inverter. In order to ensure a power supply around the clock, the combination of photovoltaic with wind and waterpower systems and/or diesel or biofuel driven current generators is also possible.
Photovoltaic mini-grids can, in certain circumstances, help save on fuel (e. g. diesel) required for electricity generation. In rural areas, fuel for generators must sometimes be transported over large distances. Remote, rural regions without grid access can be supplied with electricity via a mini-grid. This removes the high construction costs for long-distance grid connections.
Photovoltaic systems can also be used in order to ensure power supply in case of an unstable grid. With functioning power supply, the power inverter of the photovoltaic system injects into the grid, and if the power supply fails, the mains of the building are separated from the public grid and the power supply is taken over by the photovoltaic system and the battery.
Market developments in Germany and worldwide
German technology is used across the globe and reliably supplies electricity in both on-grid and off-grid applications. There are currently more than 430,000 solar electricity systems in Germany alone, with a total nominal output of 3,800 MW. The photovoltaic industry has grown dramatically over the past few years and these trends are expected to continue around the world in future years.
Based on long-standing experience and their close cooperation with research institutes, German solar producers offer high-quality, advanced and long-life products. German companies produce crystalline solar cells and modules, as well as thin-film modules, of the highest quality in modern, state of the art factories. You too can be provided with systems and products from German manufacturers which satisfy the highest demands for the production of solar cells. This is how the world’s most efficient inverter was developed and produced in Germany.
German research institutes are setting international standards. Throughout the world, highly modern photovoltaic factories are being fitted with German equipment and are being planned and constructed by German companies.
Favourable general conditions for the employment of photovoltaics
In previous years the introduction of photovoltaic technologies in Germany received strong encouragement in the form of attractive and reliable, government-backed framework conditions. Because of the extensive electricity network already in place in Europe, the key area of focus is on supplying existing networks with electricity generated by on-grid PV systems. In Germany, the Renewable Energy Sources Act (EEG) guarantees operators a fixed feed-in compensation for 20 years, making the investment secure and economically attractive. This investment security has lead to an enormous growth in the number of new workplaces in the sector. In order to secure investment for numerous on-grid systems, it is also necessary to provide clear regulations governing access to networks and feed-in of the generated electricity. Locations which are provided with higher concentrations of solar radiation increase profitability, i.e. returns on investments.
In order to profit from the advantages of solar power generation, it is recommended, on the basis of experience in Germany, to build up the photovoltaics market systematically. For this, grant programs are necessary which are in place and act continuously on a long-term basis, and which serve to liven up demand. Since the structure of a solar sector requires several years, this should be begun in good time. Experience in Germany indicates that a demand must first be created and then production follows, if a market exist.
Outlook
All forecasts expect a strongly increasing demand for photovoltaics worldwide, since solar power plants are becoming ever more cost-favourable and an increasingly strong requirement for environmentally-friendly, import-independent, price-stable and secure power supplies exists worldwide. Currently, German researchers and companies are developing processes to reduce the cost of modules and to increase yields. The key areas of focus lie in systems to position PV systems and the use of alternative materials in construction, in order to reduce the amount of silicon required. These new processes will result in sinking costs for electric power production with photovoltaics.
The experience of German companies with large plants forms the basis for an increasing worldwide use of photovoltaics for electric power production on a large scale, where energy supply security increases and there is more independence of oil-price variations. When integrated with other renewable energy technologies, PV systems can be made to perfectly meet the requirements of individual locations for mini-grid solutions, thus providing a decentralized, secure and cheap means of electricity supply suitable for many different sites.
For example, over the last few years, PV modules have started to become a design element in architecture. German modules can be perfectly integrated into buildings as part of their facade or, by clever positioning, help to shadow the interior of the building, thus reducing air conditioning costs.
The companies presented on the following pages have extensive experience in the production, engineering, project planning and marketing of photovoltaic systems and components and are interested in intensive international cooperation.
