How does photovoltaics work

How the photovoltaic system works

Photovoltaic system: how does it actually work?

With photovoltaic systems, solar radiation can be converted directly into electrical energy. So far, so well known. When asked about how it works, many of them have to fit. However, basic knowledge is essential when purchasing, operating or even installing such a system yourself indispensable and useful. Therefore, in the following, we present the concept in an understandable form - as briefly as possible, as long as necessary.

The term photovoltaics is made up of the Greek word for light and the surname of the physicist Alessandro Volta. He is considered to be the inventor of the electric battery. In his honor, the unit of measurement for electrical voltage was named as volt in the 19th century. The photoelectric effect, The basis of every PV system, was later discovered by Alexandre Edmond Becquerel and only described by Albert Einstein in the 20th century.

Together they are strong

A large number of solar cells are built into the solar modules, which are known, for example, from house roofs. These in turn can be connected to other modules in order to increase the energy yield, depending on the needs and size of the house. What happens inside the solar cell requires in-depth basic physical knowledge. Put simply, an electric field is generated by two silicon layers with different conductivity. When light hits it, its charge properties change. This creates a voltage at the contacts of the solar cell. "The solar cell thus represents an electric mini-power plant," explains the Federal Association of Energy and Water Management.

However, with limited efficiency: depending on the type of solar module, it is a maximum of 20 to 25 percent. This means that a large part of the solar energy is lost unused. Research is working on more efficient solutions however, no significant increase in modules on the mass market is to be expected in the foreseeable future. On the one hand, this is regrettable, but not tragic, since the connection of several modules in series to form a so-called string can still lead to a sufficient and worthwhile yield. On the other hand, it makes the arithmetic tasks when planning a PV system trickier, because more attention must be paid to When and under what conditions the investment in a PV system is worthwhile. Over the years, the performance of the cells can decrease and thus their efficiency decrease.

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Besides is also Allow for a certain loss for the inverter. Since solar modules generate direct current, a photovoltaic system needs this in order to convert the direct current into alternating current. If the electricity is to be fed into the public grid - i.e. if it is a grid-connected system - it must also be ensured that the properties of the electricity, for example in terms of voltage, match them. The inverter also takes on this task.

Nowadays, the vast majority of PV systems are grid-connected. So-called island systems that are not connected to the public power grid can be justified, for example in remote regions. But they have to be planned differently. For example, they cannot compensate for electricity demand in "bad times" when there is no sunshine by drawing on mains electricity.

Good to know: Solar modules are repeatedly criticized for the fact that their manufacture is very energy-intensive. This cannot be completely dismissed, but another aspect is usually forgotten: They work due to a physical effect, so neither mechanical wear parts are stressed, nor do they need any environmentally harmful catalytic converters to get going. Light on - spot on.


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Lots of sun, lots of electricity

The more light hits the solar modules, the more electricity is generated. This is the reason why unshaded and sunlit locations are recommended for setting up a PV system. Thomas Seltmann warns in his book "Photovoltaik" from the Stiftung Warentest that solar cells an electrical voltage is already present, even if they are not yet connected - similar to a battery: "Therefore, special safety instructions must be observed when handling."

The electricity consumption of the users usually does not correspond to the energy that is currently being obtained. In addition to the possibility of feeding this into the public grid, battery storage systems, which make the generated electricity available even when it is dark outside, can be a good alternative. Due to the sharply falling feed-in tariff, it is often advisable to consume as much of the solar power as possible yourself. Battery storage systems could at least double self-consumption. The catch: "They still cost several thousand euros." In order for it to be worthwhile, it should be cheap and last a long time.

In addition to these main components of a photovoltaic system, there are also smaller components that cannot be used. This includes the cabling, which differs for direct current (route from the module to the inverter) and alternating current (route from the inverter to the point of use or feed-in). In addition, there are fuses, which are usually in one Generator connection box find their place. The entirety of the solar modules connected in series is called a solar generator. It also helps with the commissioning and maintenance of the system because it can literally serve as a control center. If the electricity from the PV system is not only used for personal use, a feed-in meter is also required in order to be able to precisely measure and bill possible feed-in tariffs.

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Tags:Photovoltaics, photovoltaic technology