All about solar thermal systems

Sustainable heating systems and solar make a perfect pairing. However, a few fundamental points need to be clarified before installation.
We would like to answer the most frequently asked questions for you here.

With a solar thermal system, you are contributing actively and significantly to climate protection.
For example: A solar thermal system with a collector area of 6 m² and a 300 litre solar cylinder generates some 60,000 kWh of energy for domestic hot water heating over the course of 25 years. This spares the environment of approx. 1000 kg CO2 emissions per year compared to an oil boiler. With a collector area of 15 m² and a 1000 litre solar cylinder, some 120,000 kWh of energy for domestic hot water and room heating is generated over the course of 25 years. The environment benefits from approx. 2 tonnes less CO2 emissions per year. This corresponds to the emissions from one year’s driving (12,000 km with a medium-sized car).

With solar collectors, you are not only doing something good for the environment, you are also significantly relieving the burden on your household budget, because you are heating with free energy from the sun.
The Federal Office of Economics and Export Control (BAFA) grants subsidies for converting to solar power. If this is combined with a pellet boiler, then additional bonuses can be applied for.

Yes. Compared to a sunny day, up to 80 percent of the radiation is available to the solar thermal system on a cloudy day in summer, because the system also utilises diffuse radiation (reflected from the clouds). On a cloudy winter’s day, this still amounts to 25 percent of the radiation of a sunny day.

The water heated by solar power is collected in a cylinder that can hold twice the daily domestic hot water requirements of a whole family.
If the heat from solar irradiation is no longer sufficient to meet demand, a sensor connects the pellet boiler.

The solar thermal system generally provides around 70 percent of your domestic hot water with the help of the sun. It requires approximately 1.5 m² of collector area per person in the household. The exact size depends on your individual domestic hot water consumption, i.e. whether you prefer to shower, take baths or even own a hot tub. If the solar thermal system is designed with a larger collector area, you can also use the sun for central heating in spring and summer.

A solar thermal system can provide up to 70 percent of a household’s annual domestic hot water requirements from solar power.
Depending on the thermal insulation standard of the building and the design of the solar thermal system, some 30 percent of the annual space heating energy requirements can also be met. The only prerequisite is a south-facing roof or façade. The remaining energy demand is met by the boiler in the basement. A solar thermal system can be combined particularly well with a pellet boiler. The required buffer cylinder is used by both systems, thereby improving the overall efficiency of the heating system.

In principle, a solar thermal system can be used in any existing building.
Every roof surface that is unshaded all year round and faces a direction between south east and south west is generally suitable for solar panels. South-facing façades are also well-suited as a surface for mounting solar panels.

No. The heating engineer sets up the controller professionally during commissioning and no further interventions are required thereafter. The system runs completely automatically.

A standardised solar thermal system can be fully installed in a new building in one day.
Collectors, cylinders and solar circuit components are generally included in the kit. This is more cost-effective and makes the installer’s work easier. It also means that practically no errors can be made during installation.

Two special, thermally insulated pipes are laid from the collector field to the boiler room. If they are installed at a later date, they are routed either through a free chimney, an air duct or a “rain downpipe” on the outside wall.

The solar thermal system should be checked for frost resistance every three years.
At the same time, the pH value of the solar fluid is checked to ensure the longest possible system service life. Ideally this work should be carried out in conjunction with the periodic inspection of the heating system.

All marketable collectors are equipped with high-strength solar glass, which also withstands heavy hail. To protect them from lightning strike, the collectors should be connected to the building’s lightning protection system.
If the collectors have been subjected to a quality test as per European Norm EN 12975-2, they are mostly tested to a pressure of at least 1000 Pa, equivalent to approx. 10 to 25 cm of fresh wet snow on the collector. Most collectors withstand many times this pressure, and only when the snow depth reaches a metre or more is there any risk of glass breakage.

No. Register the solar thermal system immediately with your home insurance provider to ensure its inclusion in the insurance cover (indirect lightning strike; primarily affects the electronic controller and glass breakage). No increase in premium is required for most insurance policies.

In a new heating system, a modern buffer cylinder is usually installed as an energy centre that performs all tasks. If a solar thermal system is installed at a later date, it could well be advantageous to integrate the existing hot water tank into the solar circuit.