Solar panels, also known as photovoltaic (PV) modules or solar modules, are the core elements of a photovoltaic system. They consist of several photovoltaic cells connected in parallel or in series. These cells produce energy from sunlight that is converted to current.
The exact denomination of solar panels depends on how their individual PV cells are constructed. These cells consist of a semiconductor material – either monocrystalline or polycrystalline. A monocrystalline cell is made from a single (therefore: mono) semiconductor crystal. Its artificial growth is complex, which is why monocrystalline cells are more expensive than polycrystalline cells. However, monocrystalline cells have a better efficiency. This means that they produce more electricity from the same amount of sunlight. Their maximum efficiency is at 22%. Polycrystalline cells on the other hand are made up of several (therefore: poly) crystals. They are cheaper in manufacturing, but have a lower efficiency than monocrystalline cells. Their maximum efficiency is at 20%. This difference may seem insignificant, but it can be important if the roof area for the photovoltaic system is limited.
In solar panels, cells are protected against environmental influences by a foil and an overlying glass pane facing the sun. Since these two layers are transparent, sunlight can pass through them unhindered and reach the cells. The back of the modules is also protected against environmental influences, either by a glass pane or a foil. These are referred to as glass-glass modules or glass-foil modules accordingly.
The yield, and thus the amount of electricity produced, can be increased by about 1% using PERC technology. PERC stands for passivated emitter and rear cell (often also: contact). Modules with this technology are called PERC modules. These differ from standard cells in their construction by two additional layers.
A further differentiator for PV modules is whether they are suitable for in-roof or on-roof mounting. Most solar systems are mounted on the roof with the help of a mounting system. This enables installation on almost any roof and allows adjustment of the angle for maximum yield. While in-roof systems may seem more appealing aesthetically, it’s not possible to adjust the angle of the modules, since the solar modules replace the roof tiles altogether.
Solar modules that are integrated into the building are also deemed very attractive, but cannot be used everywhere. They can be used, for example, as overhead glazing for a carport or veranda.