Gas-Fired Heat Pumps - Transforming the UK's Domestic Heating Sector

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IntroductionThe technology being developed is that of adsorption cycle heat pumps. Adsorption cycles may be used as the basis of heat driven refrigerators, air conditioners or heat pumps. The high temperature heat used to power the machines can be from waste heat, solar thermal heat or, as in this application, combustion of a fossil fuel. They rely upon the periodic heating and cooling of adsorbent within reactors referred to as sorption generators. The specific application (product) that we intend to commercialise is a gas-fired heat pump that could provide space heating and domestic hot water to a house using one third less gas than the best condensing boiler.Previous fundingProf Critoph's group at Warwick has received funding from both the EU and EPSRC over many years, culminating in EP/C013808/1; Plate-type generators for super compact adsorption heat pumps (PLATEX). At the time of writing the proposal it was possible to show that gas-fired heat pumps could be made to the efficiency needed. The problem was that using conventional heat and mass transfer technology in the adsorption generators would result in systems that were unrealistically large and correspondingly costly. The stated aim was 'to develop and evaluate new types of adsorption generator that are up to two orders of magnitude more compact than existing technology, thereby enabling the introduction of a range of energy saving products.' PLATEX has been successful in that we have both patented and demonstrated systems in the laboratory that are 30 times more compact than commercially available equipment.Technical and commercial potentialWe have proved that our generators work as designed and have simulated their performance in domestic gas fired heat pumps Heat pumps may use the outside air, water or ground as a source of low temperature heat. Suitable water sources are comparatively rare and ground sources (vertical bore-holes or horizontal tubes), whilst energy efficient, are so expensive to install at present that we have to rule them out as systems that could be installed by the million in the UK. An air source machine can be used in almost all locations and may be conveniently packaged for easy installation. Our simulations based on annual data for the Midlands show that we can achieve a COP (Coefficient of Performance = Heat output to house / Gas input based on Gross calorific value) of 1.3 to 1.4. This represents a saving on gas bills of about one third compared to the best condensing boilers. Were the technology able to replace all domestic boilers in the UK, CO2 emissions would drop by about 26 M tonnes or 4.8 % of total UK CO2 emissions. This is a massive potential for a single technology substitution, although of course 100% replacement is not practicable. Regarding feasible market penetration, there are in excess of 1 million replacement gas boilers sold every year and even a 10% share would be enough to support economies of scale. There is also expected to be a significant market in the rest of the EU, particularly Germany, where at least four HVAC (Heating Ventilating and Air Conditioning) companies are active in R&D.The whole system of air source evaporator, gas burner, heat pump etc will be housed in a single package that will be outside the house against an external wall. The only connections to be made through the wall are a gas supply, electricity for ancillaries and hot/cold water pipes. The system uses a 'natural' environmentally friendly refrigerant and the adsorbent is an active carbon supplied by a UK based company. The total volume is less than 0.4 cubic metres.