High temperature heat pump and large ground-mounted solar PV array to minimise running costs

May 22, 2017
5 min read

New build Warwickshire country manor house uses a Daikin high temperature heat pump and large ground-mounted solar PV array to minimise running costs

This is a historic case study for work completed by Bright Green Renewables, which became a part of Green Building Renewables in 2022

The client purchased a nearly completed nine-bedroom, nine-bathroom country Manor House with a swimming pool, gymnasium, games room and media room. Rather than installing an 85KW LPG boiler and burying a large tank to store the fuel to run it, Bright Green Renewables undertook a 365 day simulation of the heat input required for the property and proved that the heating requirements could be provided by a single Daikin High Temperature heat pump with a small LPG boiler used to cover any shortfalls in capacity in the depths of winter.

The space heating and domestic hot water systems operate fully automatically and the heat pump system is eligible for 7-year, index-linked grants via the Government’s Renewable Heat Incentive (RHI) scheme. This will pay back the cost of the renewable energy installation and will also result in significantly reduced running costs.

Case Study

Having purchased an almost completed new-build country mansion in Warwickshire, our client asked Bright Green to install a 10KW, 32-panel ground-mounted Solar PV array to help support the electricity demands of such a large house.

During the installation, a tour of the property identified that UFH was installed throughout the ground floor and in all bathrooms. This was supplemented by 33 individual radiators on a separate circuit spanning three floors. The heating plant room was already being configured and the plan was to install an 85KW LPG boiler for the heating circuits. A 20KW LPG boiler had been temporarily connected into the UFH circuits to dry the concrete screed.

Bright Green commented that an 85KW LPG boiler appeared to be oversized and suggested installing a Renewable Energy heating system as a greener and far more cost-effective alternative. The customer was extremely sceptical at this proposition and Bright Green therefore offered to conduct a comprehensive room-by-room Heat Loss assessment to determine the thermal performance of the property.

The result was that at a design condition of -4DegC, and with all 39 rooms (including an indoor swimming pool) at their design temperature, the heat loss was actually only 21KW, i.e. the proposed LPG system was 400% oversized.

Bright Green offered to provide a no obligation design proposal to heat the whole house using a single 16KW High Temperature heat pump and to retain the small LPG boiler to provide additional capacity. In the resulting “bivalent” system the outputs from the heat pump and LPG boiler are combined and independently pumped into the UFH and radiator circuits. The renewable heat produced is measured by a heat meter.

Project Details

Bright Green were introduced to the project at a very late stage in the build. As such, we had to work around numerous tradesmen on site and consider their activities and the impact on these from our work.

The flooring company required the hardwood floors to be laid on a concrete screed that was totally dry. As such, Bright Green prioritised their work to ensure that the related UFH zones were commissioned first to facilitate the hardwood flooring works.

As part of Bright Green’s work scope, they also agreed to design and install the domestic hot water system. Shortly after work started it was clear that the kitchen and bathroom installers required “live” hot and cold supplies to every outlet to allow them to sign-off the 11 bathrooms, a huge kitchen/diner and the utility room. This was therefore prioritised next on Bright Green’s work schedule and completed in time for all of the bathrooms to be signed-off to schedule.

As the property sometimes had low occupancy, Bright Green proposed substituting the proposed 600L hot water cylinder with two 300L cylinders, and to configure the domestic hot water system so that one of the tanks could be turned off. This resulted in significant energy savings. The second “slave” tank can be activated with a single switch when additional capacity is required.

Throughout the design, installation and commissioning processes the customer was kept fully informed about progress – along with any ongoing specification changes that might improve system operation and functionality. As and when these were tabled and agreed to, e.g. independent time and temperature control for the radiator circuits on the 3 floors, the required changes were integrated seamlessly into the installation schedule with minimal disruption to the other trades.

Happy Customer

The heating system works perfectly providing stable temperatures around the property. The customer’s potential LPG consumption (and associated costs) has also been significantly reduced, with the 32-panel ground mounted Solar PV array providing a useful proportion of the power required to run the heat pump.

The Renewable Energy produced by the heat pump is measured by a heat meter and attracts payments of 7.63/KWh (scheduled to increase to 10.1p/KWh in mid 2017). This will result in substantial 7-year, index-linked revenues from the Government’s RHI (Renewable Heat Incentive) grant scheme.

In short, a very Happy Customer….!

Written By:

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Nicola Briscoe

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