The term photovoltaics is made up of the Greek words phonton (sun) and voltaik (tension). It is used to describe the conversion of solar energy into electricity. The chemical element silicon plays a key role in this. It is obtained from normal sand and has a conductive function when irradiated by the sun. It is the main component of a solar cell. Phosphorus is a additionally applied to the top surface and boron to the bottom, resulting in an imbalance of electrons (five on the top compared with three underneath). Because the electrons endeavour to achieve a balance with four electrons on each surface, a voltage is built up, and because silicon has four electrons, it is the ideal transporting medium (semi-conductor).
The basic unit of a photovoltaic system is the PV module or panel, in which a certain number of solar cells are electrically connected to each other. Several modules linked to one another then from a solar generator. The direct current (DC) they produce is conveyed via suitable wiring systems to the inverter, which converts it into alternating current (AC). As a result, the electricity generated by a PV unit can be fed via a meter into the public grid and utilized in the normal way.
The average service life of a PV system is 30 - 40 years, while the module manufacturers give a guarantee of between 10 and 25 years. Generally speaking, a PV unit requires little maintenance and has minimum susceptibility to malfunctions or breakdowns.
As a rule of thumb, we can say that, at our latitudes, between 800 and 1,000 kWh of electricity is produced per kWp of installed capacity. A 3 kWp unit generates in a year about the same amount of electricity as is needed annually by a 3-4 person household with a moderate electricity consumption.
We recommend insuring the system against elementary damage such as storm, hail etc. Such damage can usually be insurance, but the insurance company needs to be informed. The increase in the value of the building could lead to a higher premium. Higher insurance cover is offered by all-risk insurance contracts that also cover theft, lightning, excess voltage, loss of income etc.
Every inverter is secure against atmospheric damage through thermally controlled voltage-dependent resistors, also called "varistors". These varistors are triggered if lightning strike something nearby. The inverter can only be insured against a direct lightning strike through special insurance cover.
For this, an additional meter is installed alongside the normal electricity meter. On the other hand, if there is still a free place in the meter unit, it may be possible to use this if the electricity supplier is in agreement. Otherwise, a small additional meter box (h = 95 cm, b = 30 cm ) is installed.
An automatic device for this is integrated in the inverters. Through this so-called ENS system, the electricity input is interrupted within a very short time if the grid is switched off. With a nominal inverter output above 30 kW, additional protective devices are, however, needed.
Where is the PV unit is connected to the public grid, the usual method (because of the attractive reimbursement price) is to feed the entire solar electricity produced into the grid and sell it to the grid operator. For captive use, green electricity can, for example, be purchased on the open market. In addition, solar electricity can be used in places where there is no connection to the electricity grid e.g. for solar-powered garden lamps, solar pond pumps or small electronic units.
You will need a site plan, a layout plan of the solar unit with the nominal data of the individual components, a description of the protective devices with information on the type, make, circuit and function, a declaration of conformity for the inverters, details of the short-circuit resistance of the switch elements, an application for a meter and a certificate from the company installing the unit.