Project : Clifton Campus, Nottingham Trent University

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The Clifton Campus of Nottingham Trent University, home to the University's Schools of Arts & Humanities, Education, and Science & Technology, was to be further expanded with the introduction of a new three storey structure known as the VRGC Bio-Med 2 Scheme  which would house laboratory and office facilities. (Nottingham Trent University, recently named the UK's most environmentally friendly university in a national league table by the Planet Green League), had thier commitment to environmental management and performance in mind when designing the new building.

 

Problem

The University aimed to reduce carbon emissions by installing a closed loop ground source heat pump system which would meet a 10% contribution to the buildings' annual energy demand through low carbon technology. The maximum capacity required was 55kW of peak heating and 47kW of peak cooling and a base load of 120,000kWh annual base load.

 

Solution

Due to budget constraints, the client specified 8no boreholes to 100m. For a system capacity of 55kW peak heating load and 47kW peak cooling load, 3No water to water heat pumps rated 20kW were initially planned. This would provide 33.3% of the required duty on each pump.  Using 3No. pumps to achieve the peak load as opposed to using a single pump, would mean an increase in the flexibility of the system to provide heating and cooling.

However, as the design process was taken over by GECCO, it became apparent that the initial design would not meet the required annual base load of 120,000 kWh, which was essential if the client was to meet the 10% renewable energy target. GECCO  led the design process in conjunction with the Engineer for the Ground Source Heat Pump system to maximise the potential of the 8No. boreholes.

It was imperative that the number of boreholes did not increase due to both space and cost constraints and so GECCO produced a revised design solution incorporating the maximum of 8No. boreholes whilst using 2No. twin compressor 20kW heat pumps providing a peak capacity of around 40kW, whilst still maintaining the flexibility of a multi pump system. Despite this solution providing a slightly lower peak capacity than initially planned, it meant a higher annual base load would be returned, as well as reduced cost savings on plant  which were then passed back on to the client.

In order to ensure this was a viable design solution, GECCO carried out Thermal Response testing on site to check that the thermal conductivity of the ground would provide the return required. The results were positive and both the Engineer and the Client were enthusiastic about the new design.

The site was very confined and surrounded on 3 sides by the existing university and so logistical and construction issues needed to be carefully managed, meaning close liason with the Main Contractor and other Subcontractors was essential.

The target period for the works was 3 weeks, drilling of the boreholes began on the 20th August 2009 and was carried out using a hydraulic track mounted drilling rig with a static weight of approximately 12 tonne. A 40mm single geo-loop of 100m in length was then installed in each borehole.

Drilling, grouting and loop installation took less than 2 weeks in total with an additional 2 days to install the header works, meaning the project was delivered well within programme and budget, and that the site was cleared early alleviating congestion on site.

Completion of the VRGC Bio-Med 2 building is due in January 2010.