While everyone is talking about photovoltaic systems as part of the energy transition, thermal solar systems also offer the possibility of high savings in the areas of hot water and heating. Compared to PV systems, solar thermal scores with a smaller roof area and easy integration with existing heating systems. The advantages of a thermal solar system and the types of collectors are presented here in more detail.
1. What is a solar thermal system?
With a solar thermal system, hot water or household heating is heated by solar energy. As a result, the heating is needed less often and less oil, gas or wood is used. In summer, you can often do without the heating completely, and the thermal solar system also reduces the heating requirement in spring, autumn or winter when the sun is shining.
The most important components of a solar thermal system are the solar collectors, a solar pump and a solar storage tank, which are connected to one another by pipes. A solar fluid circulates in the pipes, which is heated by the collectors and transported to the storage tank by the pump. There, the heat is transferred to the water in the storage tank via a heat exchanger and the cooled liquid is routed back to the collectors as part of the circuit.
2. The advantages of a solar thermal system
2.1. Lower costs for hot water and heating
Installing solar collectors on your roof allows you to save large amounts on heating costs every year. On average, a degree of coverage of around 60 percent for a hot water system or 30 percent for a hot water/heating system is calculated. With the current prices for oil, gas or wood, large amounts can be saved every year if a large proportion of hot water and heating is covered by the solar collectors.
2.2. Less roof area required than with PV systems
One advantage of thermal solar systems compared to photovoltaic systems is the smaller space requirement. With a PV system, you have to calculate with 5 to 8 square meters per kilowatt peak (kWp), depending on the structure of the system, which corresponds to an area of 30 to 48 square meters for a single-family house with 6 kWp. Solar thermal for water from 5 square meters or a system for hot water and heating from 8 square meters would require significantly less space on the roof of a family home.
3. How to choose the right solar thermal system for your home
3.1. What types of solar thermal systems are there?
With the solar thermal systems available on the market, you can choose between flat-plate and evacuated tube collectors. To the Advantages of flat-plate collectors include a low price and easy installation on the roof. As a result, the flat-plate collectors are particularly popular for hot water systems to relieve existing gas or oil heating systems. However, the disadvantages of the collector type are in terms of efficiency, which results in lower performance on days with little sun.
Evacuated tube collectors, on the other hand, are more expensive but are characterized by better efficiency. The tube collectors heat up faster, which is a clear advantage, especially in months with limited hours of sunshine. Likewise, a smaller area is required for the equipment with the tubes than with the flat-plate collectors. Even installation on the facade of the house is possible, which is not worthwhile with flat-plate collectors.
3.2. How big should the solar thermal system be?
The roof area required for solar thermal energy depends on the heat requirement in the household and the type of collector. For a pure hot water system, a required area per person of approx. 1 m² for evacuated tube collectors or 1.5 m² for flat-plate collectors is assumed. Common sizes for single-family homes are 5 to 7 m². If the solar thermal system is also to be used for heating, the required area per person increases to almost 2 m² for tube collectors and 3 m² for flat-plate collectors. With these systems, many companies install sizes from 8 to 15 m² on the roof.
3.3. Very good ecological balance
Similar to photovoltaic systems, the environmental balance for solar thermal energy is very good due to the focus on renewable energies. Current tube or flat-plate collectors have a service life of more than 20 years, so you can benefit from the system for a long time. However, regular maintenance of the system is important to ensure its service life. Heating hot water or heating with solar energy reduces the consumption of fossil fuels such as oil or gas, thereby protecting the environment. With renewable energies such as solar thermal energy, the Dependence on Russian gas imports decrease significantly in the coming years.
3.4. Cost of installing a solar thermal system
For the cost of a solar thermal system, you have to consider the components such as collectors or the storage tank as well as the installation. When used exclusively for hot water, flat-plate collectors are recommended due to the lower price, which cost around 800 to 1,200 euros per square meter in the entire package. Evacuated tube collectors are more expensive, with a hot water system costing between 1,500 and 2,200 euros.
The costs per square meter are lower if the solar collectors are to supply energy for hot water and heating. For larger systems, the prices per square meter fall on average, since installation or storage accounts for a large proportion of the costs in small systems. With flat-plate collectors, you have to reckon with prices of 600 euros to around 1,000 euros per square meter for hot water and heating, while with tube collectors you have to expect costs of around 1,200 to 2,000 euros per square meter.
Average costs for collectors, storage and installation for solar thermal energy:
| type of collectors | hot water | hot water and heating |
|---|---|---|
| flat collectors | 800-1,200 € per m² | €600-1,000 per m² |
| tube collectors | €1,500-2,200 per m² | €1,200-2,000 per m² |
4. What to consider when installing a solar thermal system
4.1. Utilize government funding programs
Solar thermal is an important part of renewable energy programs to stop climate change. That is why state funding is not only available for photovoltaic systems, but also for solar thermal energy. One point of contact for cheap loans is the Reconstruction Loan Corporation (KfW), where you can use the 261 “Residential Buildings – Loan” to be able to use. A favorable development loan with an additional repayment subsidy is available there if you carry out a refurbishment to an efficiency house of level 85 or better. However, note the precise requirements as to whether you can benefit from the program for your solar thermal system.
In addition to the development bank, you can also apply to the Federal Office of Economics and Export Control (Bafa) for funding for solar thermal energy. Doing so will be loud Funding overview of the Ministry for solar thermal systems with a subsidy rate of 25%. However, you must also observe the requirements for funding with this program. Funding from KfW and Bafa at the same time is usually excluded from the programs.
4.2. What are the requirements for the installation of solar thermal energy?
A building permit is only required for the construction of a solar thermal system on the roof in very few cases. This could only be the case with large solar collectors that significantly change the appearance of the facade. You can read about the respective specifications for solar thermal energy in the state building code of your federal state or ask the responsible authorities.