Photovoltaic system Photovoltaic systems convert the electromagnetic spectrum of our sun "directly" into electrical current using semiconductor layers that in some cases are incredibly thin. The core elements in these systems are solar cells (bundled together in modules) which use the incidental photons from solar radiation to generate separate positive and negative charges. If a conductive connection is then set up between these charge zones, a current will flow.
The power that is generated in this way can either be used directly, stored in solar batteries or even fed into a power network or the public grid using inverters. Nowadays, systems are being built and operated that can achieve a peak output of several megawatts.
A solar cell or a photovoltaic cell is an electrical component that converts short-wave radiation energy, generally sunlight, directly into electrical power. The application of solar cells is known as photovoltaics. The physical principle for the conversion is called the photovoltaic effect, which is a special case of the internal photoelectric effect.
This is the fundamental difference between solar cells and other types of regenerative electricity generation, in which only the drive power for the generator is created in a non-conventional fashion.
Sometimes, elements of a solar collector are also described as a solar cell, but they only generate process heat and not electrical current, and so may replace hot-water boilers, for example.
Remuneration New remuneration categories:
From April 2012, there are now only three remuneration levels in Germany:
up to 10 kWp
from 10 kWp to 1,000 kWp
from 1,000 kWp to 10,000 kWp.
No funding is provided above this level. There is no longer any differentiation between interior systems and open-air systems with regard to the level of remuneration. Remuneration is no longer made for the entire generated solar current. In order to strengthen the incentive for internal consumption and independent marketing, the following will be remunerated from April 2012:
 * In systems up to 10 kWp, now only 80% of the system output
 * In systems from 10 kWp to 1,000 kWp, now only 90% of the system output. The difference must either be consumed internally or marketed independently.
 Given a system output of 1,000 kWp to 10,000 kWp, 100% of the generated solar current is still remunerated.

Solar radiation in Europe  

In Germany, the annual solar radiation amounts to approximately 1,000 kilowatt-hours (kWh) per square metre. The radiation is five times higher in the summer than in the winter. The level of solar radiation depends on the cloud cover, the number of daylight hours and the altitude above sea level. Moreover, the position of the sun, which is determined by the various seasons and the geographical latitude, influences the
intensity of the sun and so the output of the photovoltaic system. The annual number of daylight hours in Germany stands at about 1,300 to 1,900 hours. By comparison, a year has 8,760 hours in total. Daylight hours refers to the annual number of hours in which sunlight falls directly on the Earth's surface without being blocked by clouds. The precise values for your region, including figures referring to solar radiation, can be found on the website of the German weather service (Deutscher Wetterdienst).
It is impossible to precisely determine the number of daylight hours from which a photovoltaic system is worthwhile. Several factors such as the nominal power of the system, the roof inclination, the roof alignment and the amount of shading influence the yield of the photovoltaic system. In principle, though, the solar radiation and the number of daylight hours in Germany are sufficient to generate a profit with a photovoltaic system.
Financing First and foremost, loans for solar funding are available at an attractive rate from the KfW Bank (Kreditanstalt für Wiederaufbau). From as long ago as 1999, photovoltaic systems have been supported with government funds in the form of low-interest loans. Nowadays, however, several other banks are also offering special loans for financing photovoltaic systems. Please consult your own bank.
It is possible to finance a photovoltaic system even without any capital. Umweltbank, GLS Bank, DKB and the KfW offer PV financing as a classic interest-only loan.
Building societies also finance PV systems via immediate mortgages with a subsequent savings contract.
Insurance The insurance for a photovoltaic system should be selected carefully. Frequently, photovoltaic systems are financed and the remuneration for the current sold is available for interest and amortisation payments. For this reason, it is important, besides property insurance cover, also to check whether a so-called business interruption insurance would be advisable. Detailed information about insurance is available from your insurance company.
From April 2012, internal consumption will no longer be remunerated separately, as the average current price is higher than the feed-in price. Therefore, the higher the proportion of internally consumed solar current, the more profitable the system.
Internal current consumption in solar systems. From April 2012, internal consumption will no longer be remunerated separately, as the average current price is higher than the feed-in price. Therefore, the higher the proportion of internally consumed solar current, the more profitable the system.
Solar Thermie