Sawston Medical Centre is energy self-sustainable
Sawston Medical Centre has been built on a brownfield site, to replace a decaying structure where the medical practice has been based for a number of years, located within the heart of the village of Sawston.
The consultant engineers Mansfield Ravenhall were appointed to design a self-sustainable building securing the practice’s energy supply, by having the building create its own energy. The ambitious project incorporates a number of renewable technologies including solar thermal, solar PV & a ground source heat pump system.
At Sawston, Solartwin provided a complete Turnkey solution from initial design through to onsite project management.
Solartwin together with Mansfield Ravenhall, calculated that the total domestic hot water (DHW) demand for the new medical centre would be approx. 82,000 kWh/pa. After consulting the client we opted to design a solar water heating system that would contribute a 30% solar fraction of the total DHW usage in the centre, which equated to 24 PV pumped Solartwin systems (67.2 sqm), delivering approx. 24,000 kWh/pa (net).
We installed two 1800 litre thermal storage calorifiers, designed to preheat the mains cold water feed to a gas fired Andrews Water Heater. Each calorifier has 12 Solartwin collectors connected directly to it, with panels being easily isolated in banks of 3, without the need to decommission the entire array if maintenance is required. The project M&E contractor, Mowlem, have installed a Legionella pump set on a timer which purges the thermal store coils to ensure the system is operating within NHS and HSE standards.
The 24 Solartwin panels were fixed to the roof using the InterSole system, this spreads the load of the collectors across timber battens below the HDPE plastic sheets. Our silicone rubber microbore pipes are ducted in soil pipes , keeping flow and returns separate. Ducts penetrate through 300mm cowlings at the upper most point of the array and are sealed to avoid water penetrating into the structure.
The Solartwin system at Sawston Medical Centre contributes a CO2 reduction of 6 tonnes per annum. As the Solartwin system uses PV powered pumps, there is no CO2 claw-back, which is found in mains electricity pumped systems, usually negating CO2 savings by approx. 20%.
Technology Datasheet
Renewable energy type: Solar Thermal
Pump type: 24V variable speed
Application: Domestic hot water
Power supply: 5 Watt PV cell (x24)
Number of collectors: 24
Calorifiers: 1800 litre thermal store (x2)
Orientation: South West
Backup fuel: Gas
Angle of tilt: 20 degrees
Target annual solar fraction: 30%
Collector total aperture: 67.2 sqm
Global warming target: Save 6000Kg CO2 pa
Panel type: Freeze tolerant
Manufactured in: England
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