Photovoltaics is the process by which energy from the sun is converted into electrical energy. The term derives from the Ancient Greek word ‘phos’, meaning light, and ‘volt’, the unit of measurement for electrical voltage.
The sun’s potential as a source of energy is made clear by the following figures: Supposing that we could use 100% of the sun’s energy, roughly an hour of insolation on earth would be enough to cover the world’s annual energy requirements.
Electricity is generated in solar cells. These cells are often based on silicon, an element which is non-toxic and available in almost unlimited quantities. After oxygen, silicon is the second most common element on earth. The possibility of generating power using the photovoltaic effect was discovered as early as the 19th century, though photovoltaics first came into use at the end of 1950s in satellite technology. Now, photovoltaics is used worldwide to generate clean energy. Solar cells are also used every day in calculators, wristwatches and parking ticket machines. The power generated by solar cells is produced without noise and with zero emissions.

A photovoltaic plant is made up of several modules, which are connected together in what are known as strings. All solar modules connected together are known as a solar generator, and these modules are mounted on a support structure. An inverter converts direct current generated by the solar generator into alternating current that can be fed into the utility grid. In off-grid systems for on-site consumption, some of the energy generated is temporarily stored in a storage battery.

Solar cells are manufactured using various materials and have different properties and performance data. Solar cells are most often made from crystalline silicon extracted from quartz sand. Silicon is processed into mono or polycrystalline cells. There are also thin-film cells which are predominantly made using amorphous silicon, with some based on other materials such as copper indium selenide (CIS) and cadmium telluride (CdTe). Moreover, cells known as tandem cells exist, which are made using a combination of monocrystalline and amorphous silicon.

Simply put, a solar cell is made up of two semiconductor films. In the majority of cases, the semiconductor material used is silicon. The semiconductor films are electrically doped in different ways. This means that their electrical conductivity is influenced by introducing foreign atoms into the silicon. The current generated in the solar cells is collected using electrodes which are applied to the front and back of the solar cell. The whole of the cell rear is used for this purpose; a lattice electrode grid is positioned on the front of the cell to let as much sunlight through as possible. The front of the cell is also covered with an antireflection film to ensure that as little light as possible is reflected.

Monocrystalline solar cells are manufactured by placing a silicon seed crystal into the molten raw material and then slowly extracting this while constantly turning it. The molten silicon deposits itself onto the seed crystal and takes on its crystalline structure. This produces an ingot which is cut into thin slices known as wafers.
Polycrystalline solar cells are manufactured by casting molten silicon into blocks. An irregular crystal structure is formed as the material cools. These blocks, otherwise known as ingots, are divided into smaller parts, or bricks, and finally cut into wafers.
Thin-film cells are produced by vapour deposition of a solar cell coating onto glass or plastic. Silicon or other semiconductor materials can be used here.

When light strikes a solar cell, tiny particles of light, called photons, knock electrons out of the negatively doped semiconductor film facing the light. A positively charged hole is then formed where the electrons used to be. An electric field is formed at the junction between the differently doped semiconductor films. This electric field ensures that the charge carriers remain separated and migrate to the opposite sides of the solar cell, creating electrical voltage. Similar to a battery, a negative pole is created on the front of the solar cell and a positive pole on the rear. Current will flow as soon as a power consumer is connected to these cells.

A single silicon solar cell, 15,6 x 15,6 cm in size, produces an output of approximately 4 Watts at a voltage of approximately 0.5 volts. Standard modules consist of 36 to 72 solar cells.

The electricity generated from renewable energy sources is normally fed into the public grid and remunerated with a specific tariff depending on the capacity of the plant and when it was commissioned. Since 2009, plant operators have been able to use the power they generate themselves, either in part or in its entirety. The two-tier tariff for on-site consumption is linked to the grid feed-in tariff.

Degradation describes the aging process of solar cells and, thus, the decrease in their efficiency. This process is much less pronounced in crystalline cells than was previously assumed. Degradation is, however, more prominent in thin-film cells and particularly occurs within the first few months. Most manufacturers protect their solar cell yield with a performance guarantee. A performance guarantee of 90% for ten years and 80% for 20 years applies to all modules used by SunEnergy Europe.

Solar installations come in different sizes and can be installed on the roofs or façades of buildings, or on the ground. We plan and construct large-scale, ground-mounted solar power plants, PV plants for agricultural, industrial and trade buildings, and put together customised solutions for detached houses. Thanks to our kits, energy shed, solar carport roof, on-site consumption systems, large-scale plants and off-grid and storage systems, we have a wide range of products for anyone wishing to generate electricity from solar energy.

The amount of yield produced by a photovoltaic plant is influenced by a host of factors. The orientation and angle of inclination of the plant towards the sun, as well as potential shading at the site, play a huge role. The insolation conditions on the plant are subject to constant natural change during the course of the day and year. Throughout the year, the maximum insolation in Germany is attained on modules with a southerly orientation, inclined towards the sun at around a 30° angle. Horizontal surfaces produce considerably lower yields and are also more severely affected by performance losses caused by dirt, as this is less easily removed by rain water and wind. 
The best conditions are not often achieved in Germany. Nevertheless, slight variances from these have no serious effect on yield. Minimal shading of the plant and good rear ventilation of the solar modules are, however, important for achieving good yield, because modules become less efficient as their temperature increases.

Depending on the inclination of the module, natural cleaning from rain water will suffice. Nevertheless, it is wise to check the modules regularly for dirt and, when necessary, clean them with water to avoid the loss of yield.

A solar installation is able to produce electricity in cloudy conditions too. This is because the modules not only work under direct sunlight but also use what is known as the diffuse part of the light.