The sun is an inexhaustible source of energy. Photovoltaic systems use the sun and transform its radiation into energy via solar cells: direct, clean, emission-free, noiselessly. They require energy only in their production. Thereafter photovoltaic systems produce electricity for free. A photovoltaic system can be mounted easily on a roof or facade.

• The radiation of the sun at the earth’s surface on a clear day attains 1000 watts per square meter; on a cloudy winter day some 20 W/m². 
• Seasonal fluctuation is great. 
• Before deciding on a thermal or photovoltaic system, determine how much solar energy is available at the planned site.

Solar cells

• Solar cells are the core components of a photovoltaic system. 
• They transform radiant solar energy directly into electrical energy. 
• There are mono- and polycrystalline as well as amorphous cells. 
• Solar systems consisting of monocrystalline cells energetically amortize in ca. 85 months; amorphous cells in only 30 months. 
• The lifetime of a solar module at today’s state of the art is 20 years.

Solar modules and solar generators

• A single solar cell provides an electrical voltage of about 0.6 V and a maximum current of about 3 A. 
• To achieve higher currents, individual cells are combined to solar modules. 
• 36 solar cells are switched in series in a common frame behind special hardened glass. 
• A solar generator consists of multiple such solar modules.

Autonomous photovoltaic systems (isolated systems)

• Autonomous operation involves the supplying of devices and properties without a grid connection. 
• A constant autonomous energy supply is achieved with batteries, which supply power at times when solar energy does not suffice (night, cloudy, foggy). 
• Decentralized power supply for properties is economically possible today with photovoltaic systems (alpine huts, broadcast stations, etc.).

Photovoltaic systems with grid connection

• You can generate power for your own needs on your roof with a solar plant. 
• The grid is used as a buffer. 
• Unneeded solar electricity is fed into the grid. 
• At night or during bad weather, you can draw power from the grid. 
• Today many companies offer the main components of grid-connected photovoltaic systems as standard packages, whereby the heart is an inverter that converts the DC current of the solar module into AC.