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Themeninfos – A compact guide to energy research

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© GLASSX, Gaston Wicky
Storing heat and cold in a compact and demand-oriented manner
Themeninfo I/2009
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Latent heat storage in buildings

Can heat – or cold – be stored directly in walls and ceilings? Can heat be stored at precisely the temperature level at which it is to be used later on? And can the heat storage effect be used in a controlled manner as regards time and intensity? The answer is a clear “yes” – using materials that store heat “latently”, using a process that occurs at a defined temperature level and delivers high “concentrations”. The term “phase change materials” – or “PCMs” for short – refers to the large number of materials for various temperature ranges that can be used in buildings to achieve heat management that is tailored to meet the specific requirements.

The topic of latent heat storage is in itself nothing new. Water at 0 °C is a standard latent heat storage medium that has been in use for many years in refrigeration technology. As an alternative to traditional hot water storage, latent heat storage devices were introduced into heating technology many years ago in order to significantly increase heat storage capacities. However, the idea of integrating phase change materials into the surfaces of walls and ceilings is new. Heat management and the desired stabilisation of room temperatures operate in a largely passive manner if night ventilation removes heat during the night. PCMs can also be integrated very easily into thermo-active building systems. This results in active systems that can be used to control heat management as desired. Because of the low temperature differences between heating and cooling, low-exergy systems can be implemented that stand out for their particularly efficient use of energy resources.

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Low-exergy systems and technologies are subject of LowEx, a focal point of the German Federal Ministry of Economics and Technology’s EnOB research initiative. As part of this work, systems for buildings, building services technology and energy supply are being developed that work with lowest possible temperature differences for heat generation and refrigeration and for the distribution of heating and cooling in rooms. Renewable energy sources can also be used in this manner, e.g. the natural low temperatures of the ground, or of ground water, can be used for cooling, and solar thermal energy for heating. Latent heat storage media or phase change materials are a key component in LowEx systems.

This Themeninfo will present the current state of the art in PCM technology, alongside current PCM products and their possible applications. Initial pilot projects are also scientifically investigated.

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