Projects

A newly constructed visitor’s centre at Bishop’s Palace, a splendid medieval palace that has been the home of the Bishops of Bath and Wells for 800 years, now sources its renewable energy from a moat that surrounds the palace.

Award-winning renewable energy specialist Ecovision has designed and installed many closed-loop water source systems, but Bishop’s Palace provided an especially complex challenge, as it was not possible to drain the loop area prior to installation.

An array of ground loops were designed on loop support frames and an Ecovision diver then guided the loop array into the final position before lowering it under the water. The array sits on the moat bed but is lifted by weighting blocks which keep it in position and hold the bottom of the loops 200mm off the moat bed.

Neil Otter, Ecovision’s operations director, commented: “We have installed many closed-loop water source systems using the same loop layout strategy. However, in the past we have had the luxury of a dry surface to construct them on. The challenge at Bishop’s Palace was to get the loop set in exactly the right position by floating it from the launch area on the bank into the final sunken location.

“Calculations were made to ensure the loops, weighting blocks and frame would float into position and remain in position when filled and operational. It was a challenging part of the installation, but with accurate planning it was plain sailing.”

The closed-loop water source system comprises six 100m coils headed into one larger flow and return which penetrates the moat wall adjacent to the plant room.

The heat pump was the Dimplex SIH 20TE. The output of this heat pump is 22kW and it can achieve a maximum flow temperature of 70ºC. The heat pump will supply all of the heating and the hot water for the centre.

Ecovision estimates the average temperature of the moat during the heating season to be approximately 7ºC. The underfloor heating has been designed to operate effectively at the lowest possible flow temperatures. With this delta t across the system, the average coefficient of performance of the heat pump system will be approximately 5.2. Ecovision says that the system will be approximately 20% more efficient over the year than an equivalent ground-source heat pump system.

The return from the Renewable Heat Incentive will be in the region of £1,700 per annum, compared to a cost of approximately £2,900 per annum to heat the building using an alternative conventional oil system. The heat pump will cost approx £1,200 per year to run, giving an annual saving on heating costs of £1,700. Combined annual financial benefit is £3,400. The project received funding from the Heritage Lottery Fund and Church Commissioners for England.

www.ecovision.co.uk