Forschungsgruppe-NET - Hochschule Offenburg

Solar Heat

Thermal Baths and Wellness Center Waldbronn

The thermal baths and wellness center Waldbronn is run by Waldbronn city council’s department of health and leisure. Initially designed and built as a standard indoor swimming pool in 1976, the bath was refurbished twice (1988 and 1996) and eventually turned into a therapy spa with leisure swimming pools. The entrance hall was fully remodelled in 2003.

Today, the bath and wellness center Waldbronn features a pool area with three indoor pools and one outdoor pool as well as different spa attractions. The details of the different pools are:


Indoor pool



Fun pool



Therapy pool



Outdoor pool



The pools’ temperatures remain constant throughout the year.

The bath and wellness center Waldbronn is located within a residential area close to the spa therapy center Waldbronn. The catchment area is about 70 km. The bath and wellness center Waldbronn is open year round; it is visited by about 270 000 people per year.

Two gas boilers (2 x 1.2 MW) dating from 1976, supply the heat for water heating. They were renovated and equipped with new burners in 1999. 

The pools are filled with thermal water; the tanks for the showers are filled with potable water from the city’s system. Each shower area draws water from a different water tank.

Shower Area

Tank Size

Shower Entrance

2 500 ltrs

Showers Sauna

2 500 ltrs

Showers Organic Sauna

500 ltrs

Showers Therapy Pools

500 ltrs

Each individual tank can be reheated by a separate heat exchanger.

A preliminary water tank with a capacity of 2500 ltrs is connected before those four. It serves as buffer storage for the water heated by solar power.

In order to support the heating of the pool water and the shower water with solar power, collectors were mounted on the flat roof of the building at a height of about 7.5 m. They cover an area of 234 m2; the azimuth of the entire field lies at 15° West at an inclination angle of 30°. The flat roof sits on a wooden beam frame and it is covered with gravel. For reasons of space, the collector field was subdivided into two parallel fields. The collectors are fixed on metal trays, which were placed on the flat roof and additionally secured with the weight of the gravel. 

The bath and wellness center Waldbronn was chosen for the program Solarthermie 2000 for several reasons. First the expectation of a steady consumption of warm water throughout the day and the expected low buffer storage volume, second the good condition of the roof and the neat impression of the bath and its surroundings and third, the good demonstration effect of having a model system that combines the heating of the shower and pool water of a public bath. The efficiency of the system is expected to be very high since two thirds of the energy requirements stay at low level for heating the pool water. Together with a cost-effective setup of the solar thermal system, this accounted for the estimation that the heat production costs would remain below 0,11 €/kWh.


Project Partners


Kurverwaltungsgesellschaft mbH Waldbronn
Bergstraße 32
76337 Waldbronn
phone +49 (0) 7243 5657-0


Albtherme Waldbronn
Bergstraße 30
76337 Waldbronn
Hartmut Karle (Head of Engineering)
phone +49 (0)7243 5657-78


ist EnergiePlan GmbH
Hauptstelle Kandern
Bibelisgasse 5
79400 Kandern
Dipl.-Ing. Till Bethe (Managing Director)
Dipl.-Ing.(FH) Peter Müller (Managing Director)
phone +49 (0)7626 9721-0
Fax +49 (0)7626 9721-11


SET Solar Energie-Technik GmbH
Peter-Henlein-Strasse 2-4
27472 Cuxhaven
phone +49 (0)4721 718-817
Fax +49 (0)4721/718-818


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Project Management Jülich on behalf of the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety
Berlin Office
Breite Straße 3
10178 Berlin
Dr. Peter Donat
phone + 49 (0) 30 20199-427

Scientific and Technical Assistance

University of Applied Sciences Offenburg
Badstraße 24
77652 Offenburg
Professor Elmar Bollin
Dipl.-Ing. (FH) Klaus Huber
phone +49 (0)781 205-294

Program Monitoring

ZfS Rationelle Energietechnik GmbH
Verbindungsstraße 19
40723 Hilden
Dr. Felix Peuser
Dipl.-Ing. Reiner Croy
phone +49 (0) 2103 2444-0