Centralised systems

Large office buildings require only a small amount of transmission heat resulting from the current Energy Saving Ordinance. Inner heat sources, like people, computers, light and other devices emit so much heat that even in winter normally no or only a low heating output is needed to bring the temperature to a comfortable temperature of 20°C or 21°C. The additional demand for ventilation heat plays a key role here. The people working in the building need approx. 40 m³/h outdoor air (IDA2 according to DIN EN 13779) for good indoor air quality. The demand for ventilation heat is drastically reduced if the entire outdoor air is preheated by the exhaust air by means of a heat recovery system like this is required by the Energy Saving Act. During winter time and transitional periods, excessive heat has got to be dissipated to the outdoor air and destroyed by doing so. Centralised PCM storage systems that are incorporated in the building ventilation system can solve this problem. The exhaust air is led through a heat exchange system in which a number of individual PCM storage panels are fixed in the direct air flow.

Ideally, the heat emitted from other sources, like IT systems or chilled warehouses for example, is included in this flow of exhaust air. The latently stored heat can be brought into the flow of cold outside air the next day and not only preheat the outdoor air but also heat the building.

As an alternative, the storage system can be used to cool the building in summer if the phase transition temperature (melting point / melting range) is appropriately chosen. The storage is frozen in cool summer nights and used to cool down the sucked in air the next day.

The following typical circuit (company AGN, Ibbenbüren/Germany) shows the incorporation of a centralised PCM storage that is both used for cooling in summer and for heating a building in winter – and for precooling or preheating the outdoor air.