LowEx: Heating and cooling with low exergy

High quality, exergy-rich energy is to remain reserved for high quality energy services, while low-exergy energy forms, such as environmental heat, can be activated for heating and cooling at room temperature level. This is the central premise of low-exergy systems.

A reduction of load is the key to an exergy-optimised design. Naturally, this applies to the building envelope, as described above, but also to the individual system components. If the temperatures of the heat supply system differ only slightly from the room temperature, only low-exergy energy is needed with low-temperature heat. If low-exergy heat transfer is supplied by means of a low-exergy heat generator, and possibly a renewable energy source, this is a complete "LowEx system". In the future, improvements and innovations in buildings' energy systems will have to measure up against the best possible efficient handling of energy quality.

Within LowEx, activities focus on different areas, such as heating and room ventilation technology, for example. Here, the spatial and temporal utilisation of low temperature potentials for purposes of heating and cooling in buildings is being examined. Spatial utilisation includes heat transfer between rooms, and from the building's interior to the facade, so that a thermal homogenisation of the building structure which takes variable room usage into account can be achieved. For the utilisation of temporal temperature potentials, latent heat storage systems are being examined. Materials with a phase-change temperature similar to the room air temperature can store energy without large exergetic losses. The storage system, which can be retrofitted, is connected to the room via capillary tube mats, and can be discharged via facade heat exchangers. Cooling loads which arise are completely or partially released in this manner with a time delay.

Other focal areas are heat transfer, heat storage, and active latent heat storage systems which can be systematically charged and discharged.