Cocktail provides idea to increase heat storage capacity of wooden houses


In contrast to houses in timber construction, classic solid houses are said to have a higher heat storage capacity of the building envelope and thus generate a greater "feel-good climate". Scientists at the CeMOS Competence Center at Mannheim University of Applied Sciences, in cooperation with the company Willi Mayer Holzbau GmbH & Co. KG have developed a material that, under the right conditions, has 10 times the heat storage capacity of concrete. They have taken as their model the cooling effect of a melting ice cube in a cocktail.

These so-called phase change materials (PCMs) require a comparatively high amount of energy during the phase change from solid to liquid (melting). This energy is extracted from the environment in the form of heat. The special feature, however, is that PCM does not change its temperature until the phase change is complete. This means that a large amount of heat can be stored exactly at the melting temperature of the corresponding substance. Conversely, heat is released when the PCM cools down and solidifies again.

The scientists have now developed a special mixture of salt hydrates whose melting temperature corresponds exactly to a desired room temperature of 21 - 22 °C. The material is stored in containers made of salt hydrates. The material is packaged in polyethylene containers, each with a capacity of one liter. The encapsulations, which are reminiscent of cold packs, must then be integrated into the building envelope in such a way as to ensure the highest possible thermal contact with the indoor air. This allows the material to make a good contribution to the air conditioning of a room.

For the project, a small building with a total area of just under 18 m² was constructed and divided into two identical rooms separated by a small corridor. In one of the rooms, the encapsulated PCM was installed in two ventilated layers within the walls. The other remained empty. This allowed a total of 992 kg of the material to be installed. An 87-day test phase clearly confirmed expectations. The storage material was able to noticeably absorb temperature peaks and lower the room temperature. When it crystallizes, as happens, for example, during ventilation at night or in winter when the room temperature drops below 21 degrees, heat can be released and thus support heating capacity.

The scientists' conclusion is clear: This technology is trend-setting and has the potential to significantly improve the living climate, especially in lightweight houses. The system is currently being further optimized in further studies, for example to minimize the space required or to integrate the encapsulation as a modern and at the same time sound-absorbing element in the room. Furthermore, work is being carried out under high pressure to also accommodate the material in a central storage unit in order to realize the phase changes by means of controlled forced ventilation, which could be combined with the installed ventilation and heat recovery system, for example.

Project partners:

As a leading center for mass spectrometry and optical spectroscopy, the CeMOS competence center headed by Prof. Dr. Matthias Rädle and Prof. Dr. Carsten Hopf is involved in many industry-focused projects and is recognized as a partner of international research consortia. CeMOS is increasingly profiling itself as a provider of complete solutions, i.e. as a device, application and IT developer. The diverse core competencies are in the areas of biomedicine, process measurement technology and bio-pharma analytics, in the fields of "Data Science", image processing and chemometrics/multivariate statistics, as well as in optical device development and measurement technology-based material development.

The company Willi Mayer Holzbau GmbH & Co. KG is a manufacturer and general contractor of modern, future-oriented timber buildings. From single-family houses to multi-storey wooden buildings, the buildings are individually adapted and implemented to the wishes of the client.