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Dig deep for geothermal heat

Boreholes, solar panels and rain harvesting are just some of our practice’s green features, says Dr Steve Tavaré

Moving to new premises is a great opportunity to make green features integral to the building. While this was not top of our priorities list seven years ago, our move to the brand new Sawston Medical Centre last summer was to a building that is truly state-of-the-art in terms of environmental friendliness.

Our practice has around 13,000 patients and the eight GP partners share the medical centre with community clinical staff employed by Cambridgeshire PCT.

Over the years we considered 14 potential sites but the most suitable was part of an underused allotment area.

We worked closely with the architects West Hart Partnership and the PCT on the design for the new building.

The design included features to ensure cooler temperatures in the summer without resorting to air conditioning.

These were deep eaves and brises soleil (sun breaks) to shade windows; darkened glass to reduce solar gain; and an emphasis on the use of natural ventilation.

Rainwater utilised
To their credit, it was our developer, Primary Asset, and their design team who suggested including some less commonly used environmental features. These include geothermal heating and cooling and harvesting rainwater to flush the toilets. They became part of the design after the district valuer approved them.

The solar panels on our roof provide energy all year round to our hot water supply. On another roof section there is an array of photovoltaic panels (semiconductor devices that convert the energy of sunlight into electric energy). In the summer months we anticipate producing surplus electricity, which we can sell to the National Grid.

Around 40 per cent of water used in a building like ours is for flushing toilets. Our system for rainwater harvesting channels rainwater from the roof into a tank the size of a minibus beneath the car park. The water is then pumped to a header tank.

Even more remarkable is our geothermal heating and cooling system. Beneath another section of the car park, there are 50 boreholes that were drilled to a depth of 76m. These allow water to be pumped through pipes in a closed loop. All year round, the temperature is a constant 12ºC at 76m underground.

The water coming up is also 12ºC. It passes through a heat exchanger, where it releases energy and falls to 8ºC before returning to the bottom of the loop. The energy released heats a separate circuit of water to around 45ºC.

Heating the practice
This supplies warmth to the building through traditional radiators and, in the waiting areas, under-floor heating.

The lower temperature of our radiators (compared to typically 75ºC in homes) is more than enough to heat the medical centre because it is highly insulated.

For each kilowatt of electricity used to operate the various pumps in the water circuit and the heat exchanger, the geothermal system generates four kilowatts of heat. This is an efficiency rating of 400 per cent.

After we moved in last July, there was a prolonged spell of hot weather. The heat exchanger went into reverse to provide cooled water to the under-floor pipes in the waiting areas.

This created a pleasant chill to the air at a fraction of the cost of conventional air conditioning. Unfortunately, we cannot pass cooled water through radiators. The total cost of installing these systems was approximately £300,000.

The gas, electricity and water providers’ bills have been delayed so we do not yet have precise savings figures but they are estimated to be around £10,000 a year.

In real terms, future savings are likely to be significantly greater if, as predicted, fuel costs escalate.

Although we did not receive any special grants they are likely to become more readily available in the future. One scheme that practices may obtain funding from is the Department of Trade and Industry’s Low-Carbon Building Programme (www.lowcarbonbuildings.org.uk).

Our medical centre, which cost around £3.7 million to build, is a pleasant, restful environment for patients.

To make progress on building ‘green’ surgeries, our practice believes that from the outset of projects, the design team needs to include architects, engineers and developers who are committed to the construction of low-energy buildings, and have a keen eye for cost.  

Dr Tavaré is a GP in Cambridgeshire. He and his partners lease Sawston Medical Centre

Architects: West Hart Partnership, (01827) 67123; Developer: Primary Asset, www.primaryasset.co.uk 

Our medical centre’s green features 

  • Deep eaves and brises soleil (sun breaks) to shade windows.
  • Darkened glass to reduce solar gain.
  • Solar panels for hot water to taps.
  • Photovoltaic panels (semiconductor devices that convert the energy of sunlight into electric energy).
  • Rainwater harvesting for flushing the lavatories.
  • Geothermal system for heating — full details in the main text. This can be ‘reversed’ to provide cooling via under-floor pipes in the patient waiting areas.
  • Building insulated to a very high standard. 

For more about green issues and resources for your practice visit Healthcare Republic at www.healthcarerepublic.com/greengp







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