Small smart sustainable systems for future domestic hot water (4S-DHW)


Funder: RCUK/EPSRC
Duration: 01 March 2016 to 28 February 2019
Staff Involved: Professor NJ Hewitt

The purpose of the proposed research programme is to address the challenge of providing domestic hot water (DHW) using low carbon heat pump technology given the overwhelming trend away from conventional hot water tanks in homes and the inability of present heat pumps to provide instant hot water.

We intend to develop a suite of heat pump / storage / control technologies, using either electricity or gas that function without conventional storage cylinders and can deliver energy efficient affordable hot water to a wide range of dwellings well into the future.

Ulster will use a novel compressor being developed by industrial partner Emerson that has an exceptional range of running speeds, enabling the same device to either deliver e.g. 25 kW for instantaneous hot water or 10 kW or less for space heating. This would be used in conjunction with a small buffer store to overcome the delay in start-up before hot water is available.

Present gas fired heat pumps (both commercial and under development at Warwick) are easier to modulate but are physically large if delivering 20 or 30 kW and also have a long start up time (5 minutes). The Warwick goal is to use new composite adsorbent heat exchangers to reduce start up time to one minute, even when meeting a 25 kW load and to reduce key component sizes to achieve a compact system.

Thermal storage is a vital part of DHW provision by heat pumps. A small buffer store may be needed to overcome starting transients, or a large capacity store might be needed to provide a bath-full of water quickly. An intermediate capacity store might work together with a heat pump to meet peak loads. Our research will encompass buffers, compact PCM stores that could be sited in unused spaces such as corners in kitchens and 'flat' stores using vacuum or aerogel insulation that could fit under kitchen cabinets or other available unused spaces.

To bring this all together into a range of integrated systems suited to different housing types etc there needs to be both an understanding of the consumer's needs and preferences plus a smart adaptive control system. In addition to data in the literature we have access to data from detailed monitoring studies previously carried out by Loughborough. Consumer preferences will be investigated by the use of surveys carried out by the User Centred Design Research Group at Loughborough Design School.

Ulster will assume overall responsibility for sensor choice, control hardware and software. They will devise a system controller that adapts to and meets consumer needs in an optimal way. In the long term this will be part of a house-wide wirelessly linked system including 'wet' appliances such as dishwashers and washing machines and 'smart taps' that communicate with the DHW system so that it responds optimally to the size and type of load demanded.