HEAT PUMPS 1 SORPTION TECHNOLOGY
generators (the sections that generate the ammonia vapour) that form a sub-assembly consisting of the generators, ammonia check valves that connect to the evaporator and condenser, and the mass recovery solenoid valves. The schematic for a two-bed package
shows the operation that allows the active carbon beds to adsorb and desorb in sequence (see Figure 3). Although still in prototype, the whole system has been visually modelled to fit in a compact, externally mounted casing with gas, electricity and water connections being made from inside the residence. It is designed for a typical UK house that had been retrofitted with good insulation to the point that the heat pump needed to deliver 7 kW of heat. The predicted operation of the systems
would have roughly the same carbon emissions as traditional electrically driven vapour compression heat pumps at low (30C) output temperatures, but at higher temperatures (50C) it is expected that this new system would save around 14% carbon. Since the system is heat driven (with gas) the energy cost savings are likely
to be more dramatic (see Figure 4). The control mechanisms within the unit
are relatively complex, but Critoph’s team has a fully working prototype that is being
tested to EU standards. This prototype has: l A system using gas fuel; l Four beds for higher efficiency; and l Nominal heating power of 7 kW
(continuous) for space heating and hot water. The modelling predicts a seasonal
space-heating COP of 1.4, using radiators – which suggests a 36% drop in fuel use compared with a 90% efficient condensing boiler. The team hopes that the prototype will lead to a production design that will reduce the component complexity.
This work described above was undertaken as part of the CALEBRE (Consumer Appealing Low Energy Technology for Building Retrofit) programme funded by the UK’s Engineering, Physics and Science research Council and EO.N Work; it was carried out by the University of Warwick and is the subject of further development by Sorption Energy Ltd. A presentation of the findings was made at a CIBSE seminar on heat pumps in May.
It is hoped the prototype will lead to a production design that will reduce down the component complexity
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