Integrated renewables for listed building

Monday, 16 February 2009

Solar heating, heat pumps and a special thermal storage vessel

Renovation of the north wing of a Grade II listed Hall in Northumberland is making use of Hoval's SolKit solar heating, Thermalia ground source heat pumps and the innovative CombiSol thermal storage vessel.

The solar panels, heat pumps and a back-up oil-fired boiler all feed to the CombiSol thermal storage vessel, which has been specially designed to enable renewable and conventional heat sources to be used and controlled together. A 1200 litre capacity vessel has been used, with an internal 300 litre stainless steel sphere for domestic hot water (DHW).

"As well as increasing energy efficiency and reducing environmental impact, we wanted to ensure the system had a high degree of resilience," explained Bob Gelley of main contractor Orbis Eco. "The combination of various heat sources, operating on a cascading principle utilising, when available, solar followed by tandem heat pumps and ultimately an oil boiler for peak load demands - all using the CombiSol and TopTronic controls to make them work efficiently together - ensures that we've achieved that," he added.

Making effective use of thermal stratification, the CombiSol ensures that water at the top of the vessel is at the required temperature and that DHW is maintained at 55ºC. Where solar energy is able to meet this requirement the hot water is fed to the top of the vessel. When less solar energy is available, the lower grade heat is fed to the bottom of the vessel to pre-heat the water and act as a thermal battery.

There are two ground source heat pump circuits, one providing high grade heat to the top of the vessel, the other supplying low grade heat to the bottom of the vessel. Any surplus heat is transferred into a low temperature underfloor heating system in the refurbished North wing and also to the South wing to pre-heat water serving the conventional two pipe radiator system.

It is anticipated that the oil boiler will only be used during the coldest times of the year.

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