Photovoltaic: use solar power

The largest part of the electricity still originates in Germany central large power plantswhich are operated with fossil fuels such as coal, oil or natural gas, but also derive their power from natural resources such as reservoirs.

Photovoltaic: use solar power: photovoltaic

However, decentralized systems that produce electricity close to the user are becoming increasingly important. In private hands it is usually about Photovoltaic systemsThey use solar cells to generate electricity from sunlight and feed it into the home network, where it is consumed directly or passed on to the public grid.

Construction of a photovoltaic system

Photovoltaic: use solar power: photovoltaic

The most striking part of a solar power system are the too panels combined solar cells, They are usually mounted on pitched roofs, but also mounted on flat roofs with a frame that aligns them to the sun.

Since solar cells generate DC voltage, they first feed the energy into an inverter, which feeds them into the normal household AC voltage converts. The operating and control electronics also include devices for voltage stabilization and in many cases a device that allows the shutdown of the system and easily accessible places in the house.

Photovoltaic: use solar power: photovoltaic

Finally, the electricity flows to the house distribution, from where it enters the home network. Depending on the design of the system is also a Feed-in installed, which counts the proportion of solar power flowing into the public grid so that it can be remunerated.

In most cases, photovoltaic modules are mounted on sloping ceilings, which are favorably oriented towards the sun. The installation on flat roofs is also possible. For this, the modules are mounted with special brackets.

How does a solar cell work?

Solar cells usually consist mostly of silicon, Part of the silicon is deliberately contaminated, this is called "doped". The doping produces either gaps in the electrons or excess electrons. If the sun shines on the solar cell, electrons begin to migrate at the transition between the differently doped materials and electricity can be drawn from the system.

Photovoltaic: use solar power: power

Raw silicon - after oxygen it is the second most abundant element on earth. Silicon for solar cells is also out Recycled material won. The silicon crystallizes during production into long strands, from which slices (so-called wafers) are cut. Left polycrystalline, right monocrystalline silicon.

Switching a series of solar cells together to form a photovoltaic module increases the overall voltage to a useful value.

Photovoltaic: use solar power: photovoltaic

Photovoltaic: use solar power: electricity

The wafers are coated with a mostly blue protective lacquer and wired. This creates individual solar cells. Several solar cells together form a module, which is framed by a frame and provided with connections.

Which solar cells are there?

On house roofs are usually so-called Thick-film cells used. There are two types: polycrystalline cells are composed of a series of silicon crystals. They are relatively inexpensive and achieve a presentable energy yield with good supply of sunlight.

Photovoltaic: use solar power: photovoltaic

In less favorable situations one can monocrystalline cells use that consist of large single crystals. They achieve higher efficiency but are also more expensive.

If more space is available for the solar modules, such as a suitably aligned facade, then one can also use thin-film cells made of amorphous silicon. Here, the silicon is present in a largely disordered structure. This one thin film cells Although cheap, but also have a very low efficiency, you can actually use them only on large areas meaningful.

Photovoltaic: use solar power: photovoltaic

The most commonly used modules for mounting on pitched roofs have polycrystalline cells. If large areas are available, for example a complete façade, one can also use thin-layer cells made of amorphous silicon.

Power of photovoltaic systems

Size, orientation, installation angle, installation situation and sunshine determine the actual yield. If, as here, solar modules are integrated directly into the roof, ventilation must be provided so that the modules do not lose their power due to overheating.

Photovoltaic: use solar power: solar

When planning a system, the unit kWp is used for the expected output. This means "kilowatt peak" and stands for the maximum achievable in full sunlight, the peak value. Many manufacturers refer to this value as the "face value" because it makes the different plants comparable.

The actual performance achieved in practice is influenced by a few other factors. On the one hand, this includes the alignment of the cells - ideally they show at an angle of about 30 degrees erected south to south-southwest and shaded during the day neither of neighboring buildings or trees.

Photovoltaic: use solar power: photovoltaic

Another factor is the actual solar radiation, which can be estimated for each location based on the average number of hours of sunshine per year.

And finally, the installation situation is also one of the factors: modules that are permanently installed in the roof cladding, for example, are heated to a greater degree than specimens mounted at a distance from the roof, and the efficiency of the cells decreases as the temperature rises.

Types of photovoltaic systems

Island plants

Photovoltaic: use solar power: photovoltaic

Photovoltaic systems without connection to the grid can serve very different purposes. Also conceivable is the use as Solar filling station for the electric car.

In the simplest form of a solar system, a single panel is mounted to provide power to local consumers. This can for example be the case in a garage or a carport, but also in outbuildings in the garden. For example, the module feeds the lighting or a water feature in the garden. For the night or for periods of low sunshine, the electricity is stored temporarily in a rechargeable battery.

New perspectives are also opening up for electric cars. They can be refueled at a sufficiently dimensioned island system. At the same time they offer through their big battery packs the possibility to save electricity.

Grid connected systems

This is the most common form of the solar system described at the beginning, in which the photovoltaic modules are connected via an inverter to the home network and, if necessary, to the public grid.

Cost-effectiveness of photovoltaics

At the beginning of the solar power era was clear how private operators one Photovoltaic system The electricity generated was exclusively fed into the public grid and had to be paid by the suppliers for a legally guaranteed price for 20 years. With this guaranteed feed-in tariff the plant could be paid off. At times even self-consumption from subsidies was remunerated.

Meanwhile, the remuneration has melted significantly and the Internal consumption Compensation there is not any longer; At the same time, however, solar modules have become noticeably cheaper and the electricity consumed by utilities has become significantly more expensive. As a result, self-generated electricity has become cheaper than that of the utility and the feed-in is no longer worthwhile as it was in the past. Therefore, today the economic operation of the plant is regularly achieved by consuming the self-generated electricity to the highest possible extent and feeding only the remaining quantity into the grid.

In order to synchronize the times of the highest yield of the photovoltaic with the highest consumption, there are different strategies. For example, it is possible to start electricity hungry consumers such as washing machines or dishwashers when the sun is shining intensely. This can be achieved, for example, with an electronic control unit, which detects the solar radiation by sensor and then switches the corresponding devices.

A good possibility is also to cover, for example, the operating current of a heat pump heating with photovoltaic. If the heater has a large buffer, you can put it in sunny times heat up and then has a hot water supply for heating or showering available.

Save electricity

Photovoltaic: use solar power: electricity

Rechargeable batteries with lithium-ion technology can be built very compact and take up much less space than lead batteries.

Even if the home automation, so what you today as "Smart Home" In many cases, there are many ways to shift consumption to productive times, but in many cases there is no way around saving at least part of the electricity generated with photovoltaics. This is possible with different solutions. If you have a lot of space, you can use traditional lead-acid batteries as storage, which are technically related to car batteries. Their energy density is not intoxicating, but they are comparatively cheap to have. More expensive, but less space consuming Storage solutions with lithium-ion cells.

Protect photovoltaic system in the long term

Still are Solar power systems expensive. They therefore only pay off if they supply electricity for several decades. During this time, the system must therefore run as trouble-free as possible.

To ensure that, for one thing Durability and functional warranties of the manufacturer and the installer of the system. Although one can never predict whether a manufacturer will still exist in twenty years, a long-term guarantee is better than none.

It is also useful to insure the photovoltaic system, which pays for example in natural phenomena such as lightning strikes. Make sure that the insurance not only replaces the damaged technology, but is also responsible for the lost revenue during the repair.

Incidentally, even if the plant is economically profitable only after a long time, for the environment, it is very soon a gain: In general, it has produced after just a few years as much energy as was spent on their production and installation. Thereafter, it will continue to save fossil fuels and avoid CO2.

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