DWHR at the kitchen drain in Penrhyn castle, Wales

 
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Temperature monitoring of the drain water from the kitchen at Penrhyn castle has shown temperatures of up to 50°C, showing a clear waste of heat through the drain. Using 2 heat exchangers this demonstration site aims at showing direct heat recovery methods from kitchen drain water, and is testing different configurations of the drain water heat recovery (DWHR) system.

Proposed system

The first configuration is the simplest one, simply preheating the incoming water. This low-cost and uncomplicated solution has the disadvantage of being very vulnerable to mismatches between drain water heat availability and kitchen hot water demand.

The second configuration attempts to counteract those mismatches by recirculating the preheated water, from a holding tank, through the heat exchanger in the drain. This has the advantage of ensuring that at every moment water flows through the drain (part of the) heat will be recovered. The disadvantage is the increased complexity of the system, and additional consumption in the circulation pumps.

 3rd configuration of the DWHR system, preheating  and recirculating mains water

3rd configuration of the DWHR system, preheating  and recirculating mains water

 First configuration of the DWHR system, preheating the mains water

First configuration of the DWHR system, preheating the mains water

 

The third configuration, combining both systems, is expected to recover the largest amount of heat. However, it’s the most complex solution. The demonstrator will be used to make a trade-off between this increased complexity and the benefit of increased heat recovery, and observe the operation of such systems in real-world applications.

Objectives of the demonstrator

The system, regardless of its configuration is expected to provide about 25% of the heat consumption of the kitchen. This heat is currently provided by a main heating loop, where the heat is generated in a biomass boiler house, and then pumped to the rooms in the castle. The savings are thus expected to be twofold, not only will the pellet consumption of the boiler be reduced, but, more importantly, the electricity consumption, used for driving the pumps, will decrease as well. Expected greenhouse gas emission savings are in the range of 2-3 tons, annually.

In the press

Castle Pioneers waste-water heat capture technology
Wales-Ireland joint project explores energy efficient water solutions
Engineers trial new tech to stop energy going down the drain