GECCO2 'Energy Efficient Project of the Year 2009' Runner-up

This high-profile Ground Source Heat Pump project involved GECCO sinking a large number of 125m deep boreholes, penetrating difficult ground conditions, including coal measures bedrock.  The boreholes were required to provide 130kW peak heating capacity, necessary to heat the six-lane pool, whilst also bringing the benefits of low carbon emissions going forward.

                 Mansfield image 2             Mansfield image 1

In February 2009, a £4.5m major refurbishment commenced at Sherwood Baths in Mansfield, the place where Olympic sensation Rebecca Adlington learnt to swim, ultimately becoming a state-of-the-art leisure facility, renamed 'The Rebecca Adlington Baths'.

Problem

The scope of works included the replacement of all mechanical and electrical services installations, as well as the provision of new Biomass boilers together with high and low temperature low loss mixing headers with a Geothermal Ground Source Heat Pump as the primary heat source, all of which, would significantly reduce the facility's carbon footprint as well as the long term energy costs.

Solution

GECCO was responsible for the design and installation of the ground source heat pump package.  Due to a shortage in land space and existing high voltage power cables, it was essential that the number of geothermal boreholes was kept to a minimum. For this reason, a horizontal loop system was ruled out as unsuitable and it became apparent early on that a vertical closed loop system would be the most appropriate option to maintain a sustainable system. The design solution involved 2No. Ground Source Heat Pumps, providing a peak heating duty of 130kW.

During the initial design of the system, GECCO, due to site constraints had to reduce the specified scope of works from 28 No. 100m length closed loop boreholes, down to 22No 100m length closed loop boreholes, which gave the client considerable financial and programme savings.

At contract stage, it became apparent that space on site was of an absolute premium and the Main Contractor, G F Tomlinson required clear access to be maintained at all times. In order to facilitate their requirements, GECCO  redesigned the Geo-Exchange, extending all boreholes to a depth of 125m, therefore reducing the number of boreholes, whilst maintaining the overall installed meterage .

In order to confirm the adequacy of the revised design, testing was carried out on site using GECCO's own bespoke, self sufficient Thermal Response Testing facility. The data collected demonstrated that the results verified the initial design assumptions, however, prepared for all eventualities, GECCO allowed for the possibility that the target depth of 125m may not have been reached in every bore due to possible voids within the Coal Measures bedrock.  Working with the client, GECCO managed this risk of additional borehole positions by way of programming the drilling and header work around the client's access requirements.

The boreholes were installed using a Casagrande Rotary Drilling Rig, all reached the target depth of 125m, therefore, 18No. boreholes were installed achieving a significant programme saving, allowing the Main Contractor the space needed to keep the access and egress clear.

Following the drilling of the boreholes and installation of the Geo loops and grouting operation, the digging out of the required trenches for the header work was commenced, the high density polyethylene pipes were laid, and connected using a combination of electro-fusion and butt-fusion welding where appropriate.  Following flushing and pressure testing of the completed system, the system was dosed with a 25% antifreeze solution to provide the necessary protection, as the peak fluid temperatures within the Geo-Exchange could reach as low as -5oC.

The Ground Source Heat Pumps were connected directly into the low temperature low loss header from where hot water was then circulated to the under floor heating manifolds and to the swimming pool heat exchanger.

The Rebecca Adlington Swimming Pool is on schedule to reopen in January 2010.