Solar thermal collectors - Bringing you free energy from the sun

Using solar energy with Viessmann Vitosol

Harnessing the sun's energy – that's what the collectors in the Viessmann Vitosol product range make possible. They are used either just for DHW heating or additionally to back up the existing boilers in providing central heating. In this way, you can use up to 60 percent less energy for DHW heating, or reduce the total heat demand by up to 35 percent if DHW and heating water are heated together.

When installing a new heating system as part of a new build or modernisation project, the Vitosol solar collectors should always be factored in at the planning stage. This investment pays off not only through the energy savings. It is also supported by public subsidies. What's more, it is a big plus for the environment. This is because the collectors convert solar energy into heat without any carbon dioxide emissions. CO₂ neutral heating is the motto here.

Vitosol flat-plate and tube collectors

There are essentially two types of solar collectors – flat-plate collectors and tube collectors. Both convert solar energy into thermal energy with the help of an absorber. However, they differ in the way the details work. Tube collectors, for example, consist of the tubes that give them their name. The absorber is located inside the tube, surrounded by a heat-insulating vacuum. The heat transfer medium does not flow directly through the tubes. This is because the Viessmann tube collectors work according to the heat pipe principle. The heat transfer fluid runs through the heat exchanger, also called the header. The process medium evaporates inside the heat pipe and transfers the heat to the heat transfer medium via the Duotec double pipe heat exchanger. This guarantees optimum heat transfer. The absorbers in the flat-plate collector, on the other hand, are copper or aluminium sheets that absorb the sun's rays. Pipes connected to these absorbers guide the liquid through the collector.

The collectors are only one part of a solar thermal system. In addition to the pipework, heat exchangers and pumps, DHW cylinders are key to efficient solar backup in the provision of heating and hot water. With the help of a cylinder, the energy that is not currently required can be temporarily stored for later use. Viessmann offers a special product package for this purpose: Vitosol 141-FM – consisting of two Vitosol 100-FM flat-plate collectors and a 250 litre Vitocell cylinder.

Special feature of Viessmann Vitosol products: ThermProtect

To ensure high operational reliability and a long service life, Viessmann has developed ThermProtect – an automatic overheating protection system. It means that the collectors switch off when a certain temperature limit is reached. This occurs independently of the system configuration, the control settings and the installation position of the collectors. Due to the distinct technical requirements, overheating protection works differently for flat-plate and tube collectors.

For example, the crystalline absorber coating of the Vitosol 200-FM and 100-FM changes as soon as the temperature limit is exceeded. When the temperatures fall again, the crystal structure returns to its initial state. This process is reversible and permanently available.

With tube collectors, on the other hand, the heat pipe principle ensures the temperature-dependent shutdown. The solar energy evaporates the medium in the heat pipe, which liquefies again in the condenser. The resulting thermal energy is transferred to the system. ThermProtect here means that the medium can no longer condense at a temperature of 120 degrees Celsius.