Ventilation Storage Heater

A system for heat recovery with controlled room ventilation.

The Ventilation Storage Heater is an electrically powered sorption system designed to utilise the heat pump effect to provide air-conditioning in individual rooms in low-energy houses. In winter, it allows energy efficient heating, in the transition period it works as a conventional heat recovery system and in summer it is used as an air-conditioning system. The system sketched below consists of a adsorber-condenser-evaporator and a mixing chamber, which (together with the fans not included in the sketch) are housed in an enclosure. Valves are positioned between the absorber and condenser as well as between the condenser and evaporator. These are operated by means of a control device.

Winter Operation

For heating in winter, warm and used air is sucked in and piped out via the evaporator. This air passes on the majority of its perceivable and latent heat to the evaporator, making water evaporate inside the evaporator. When the valves V1 and V2 are open, the steam flows to the adsorber and is adsorbed by the zeolite, thereby giving off adsorption heat. Cold outside air is piped through the adsorber, which is then warmed as a result (heat pump effect). Once the adsorption process has been completed, desorption is started (with night-time off-peak electricity) with the valve V2 closed; the adsorber is heated with electricity. Steam then flows from the adsorber into the condenser, where it condenses and gives off condensation heat. After that, cold outside air is piped out of the mixing chamber via the condenser; it warms up and the available energy is utilised. An ice buffer can also be used in the evaporator during desorption (at night) to cool the exhaust air.

Summer Operation

During cooling in summer, air streams are reversed. As a result, adsorption and condensation heat are piped to the outside and the air piped in from the outside is cooled at the evaporator and piped into the room requiring cooling. Adsorption and desorption take place as in winter operation. Moreover, during the transition period, heat recovery is possible as shown in the sketch below.

Advantages of this system:

  • Night-time off-peak electricity can be used for cooling / air-conditioning during the day.
  • Thanks to heat transformation in winter operation, usable heat can still be gained (heat pump effect) even when temperatures are below zero (e.g. -5 °C; -10 °C).