VODASUN Glossary - The solar lexicon

Semiconductors play a central role in the photovoltaic industry. They are the basis of solar cells, the smallest components of photovoltaic systems. Semiconductors are materials that are neither good conductors nor good insulators. Their electrical conductivity lies between that of metals and non-metals. Solar cells utilise the photoelectric effect to convert light energy into electrical energy. This effect means that electrons in a semiconductor can be triggered when they are irradiated with sunlight.

There are two layers of semiconductor material in a solar cell: an n-layer and a p-layer. The n-layer has a surplus of electrons, while the p-layer has a shortage of electrons. When light hits the solar cell, electrons are triggered in the n-layer. These electrons can then flow into the p-layer and generate a current there.

A series connection in photovoltaics describes the connection of solar modules one behind the other, i.e. in series.

In a series connection, the total voltage increases while the total current remains constant. This makes it possible to generate higher voltages, which is particularly necessary in applications where a higher voltage is required, for example when charging batteries or operating inverters to convert direct current into alternating current.

Shading, also known as shadowing, plays an important role in the field of photovoltaics, as it can impair the performance of individual solar cells within a system.

If a solar cell is exposed to shade, this can disrupt the electrical flow and increase the resistance in the affected cells. The result? These cells either no longer produce any electricity at all or only a fraction of what they could produce under optimum conditions. This effect can have a negative impact on the overall yield of the system, as even slight shadows lead to a noticeable drop in output.

Shading can be divided into two types: that which depends on the season and that which does not. Seasonal shading is caused by the changing position of the sun, which explains why solar systems often generate more energy in summer than in winter. Non-seasonal shading changes throughout the day and is caused by objects such as trees, chimneys or buildings, which cast different shadows depending on the time of day.

How can shading be reduced?
For homeowners, this means analysing the geographical location and optimum alignment of the solar panels in advance. An effective method of minimising the effects of shading is the use of bypass diodes. These clever little components conduct the current around the shaded areas and thus help to maintain the flow of energy through the remaining cells.

The short-circuit current is an important parameter in photovoltaics that indicates the maximum current that can flow through a photovoltaic module when it is short-circuited. In a short-circuited state, the connections of the module are directly connected to each other so that the current can flow unhindered.

The short-circuit current is often considered together with other parameters such as the open-circuit voltage and the maximum power point of a PV module in order to assess its performance and suitability for certain applications.

The snow load refers to the weight and load that snow exerts on solar modules and the associated mounting systems. The amount and type of snow as well as the pitch of the roof influence the snow load.

The effects of snow load on a roof depend on various factors, including the roof pitch, geographical location and type of snow. Fresh snow is lighter than compacted old snow, while wet snow has the highest weight. However, when wet snow compacts into ice at the edge of the roof, an additional load is created that is parallel to the roof surface.

It is important that photovoltaic systems and their mountings are designed to withstand regional snow loads in order to minimise damage and safety risks. Regional building regulations and standards often specify the minimum requirements for the design of photovoltaic systems with regard to snow load.

A solar collectoris a Part of the photovoltaic system that is used to convert sunlight into electrical energy. In photovoltaics, solar collectors usually consist of solar cells or photovoltaic modules made of semiconductor materials. These materials generate electrical currents when they are hit by sunlight, resulting in a direct conversion of light energy into electrical energy.

Solar energy refers to the energy obtained from the conversion of sunlight into electrical or thermal energy.

This is achieved by utilising solar cells in photovoltaic systems. Solar energy is a sustainable and renewable resource that helps to promote environmentally friendly energy sources. It offers a clean alternative to conventional energy sources and helps to reduce greenhouse gas emissions.

Solar thermal energy is a technology that utilises the thermal energy of the sun to heat water or heat rooms. In contrast to photovoltaics, which converts sunlight directly into electrical energy, solar thermal energy focuses on converting solar energy into thermal energy.

In solar thermal systems, solar collectors are used to capture sunlight and absorb the heat it contains. This heat is then used to heat water, which in turn is used in heating systems or to heat water. Solar thermal energy is used in private households as well as in commercial and industrial environments to reduce the need for conventional heating and hot water systems and to utilise a more sustainable energy source.

The solar yield of a PV system refers to the average annual amount of solar power generated by the system. The financial return, especially in the area of photovoltaics, is centred on income from feed-in tariffs and electricity cost savings. These can be determined using a photovoltaic calculator or by making enquiries.

The yield depends on various factors such as the orientation of the PV system, the efficiency of the modules, the quality and efficiency of the components and the regional solar conditions. The intensity of solar radiation is primarily determined by the geographical location of a place, its altitude above sea level and the distance to the equator.

Yields from years with high and low solar radiation balance each other out over the service life of a photovoltaic system.

The surface load describes the load per unit area that a solar system exerts on the roof. It depends on various factors, such as the module and roof type, inclination and additional loads due to snow, wind and the mounting frame. The surface load is particularly important for flat roofs, as stronger wind forces occur here, which require heavier anchoring.

Before installing a solar system, the stability and statics of the roof should be checked, especially in older houses.