What are solar modules?Solar modules, also referred to as solar panels or PV modules, are an elementary component of photovoltaic systems. They have the task to transform incident solar rays into electrical energy. In order to achieve this, solar modules are made up of several layers. Inside the panel are the solar cells. In each solar cell is a semiconductor, which is responsible for the conversion of sunlight into usable energy. Semiconductors have substances that develop electrical conductivity in light and heat, whilst having an insulating effect during cold weather. The semiconductors used in solar cells are doped differently. That is, various chemical elements have been added to them so that they are either positively or negatively charged. One speaks of p-type semiconductor layers and n-type semiconductor layers. If two differently charged semiconductor layers meet, a so-called p-n junction is formed at the interface. Here an inner electric field is formed. In the case of solar radiation, electrical voltage is produced and delivered to connected consumer devices.
On the cell layer is a layer of EVA (ethylene vinyl acetate) or cast resin. It protects the sensitive semiconductor against weathering, moisture and corrosion. There is also a protective layer below the solar module. This stabilizes the module structure and prevents stored heat loss. In order for the solar energy to be efficiently used, at least one of these layers must be slightly-permeable. A special solar glass plate is installed on top of the EVA layer. In order to achieve efficient energy production, these special requirements must be met: The glass must be thick enough to withstand wind and weather effects, and at the same time the incident light must not be absorbed and stored by the panel itself.
How are solar modules manufactured?The production of solar modules and solar cells are based on the synthesis of silicon. Silicon is a component of sand or quartz and is therefore one of the most abundant substances on earth. With a degree of purity of well over 90 percent, silicon is considered a particularly pure substance. There are basically three types of solar modules: monocrystalline solar modules, polycrystalline solar modules and amorphous solar modules. These are different cell types and their differences can be traced back to the respective production methods.
Monocrystalline solar modulesIn order to produce monocrystalline solar cells, the silicon oxide, which naturally occurs in the sand, is chemically reduced by the addition of carbon. This process takes place in a so-called arc furnace at a temperature of about 1.410 degrees Celsius. The result of this melt is a thin crystal rod, which is also referred to as a single crystal or monocrystal. The monocrystal is cut into very thin slices: with a thickness of 0.4 micrometers, the square slices are thinner than a human hair. The cut plate is called a "Wafer". After the wafer has been chemically cleaned, the doping takes place: At temperatures of 800 to 1,000 degrees Celsius, silicon atoms are replaced by atoms with a different valence. This increases the conductivity and thus the efficiency of the wafer.
Monocrystals are easily recognizable due to their dark appearance and rounded corners and have a particularly high efficiency due to their purity. Under ideal conditions this can be about 20 percent. Critics criticize the high energy expenditure required by the production of monocrystalline solar cells. Only after several years, such photovoltaic modules have a positive energy balance.