The installation of a 180kW Stiebel ground source heat pump system with bore hole heat collector.
The project: Complex of several blocks of contemporary red brick student accommodation at a world leading university, located in a city centre. The buildings were heated with electricity which was costly and outdated. The college wished to use zero carbon technologies to not only reduce their carbon footprint and energy consumption, but also to provide more attractive facilities for the building users.
The challenge: The ground heat collector and header pipe work were to be installed a considerable distance from the newly constructed energy centre. The rugby pitch selected as the most suitable place for the bore holes was 200m from the energy centre with a cricket pitch and tennis courts in between.
A further complication was several sewers, including the main city sewer, running beneath the sports fields! A desk top geological survey suggested the presence of artesial brine at an expected depth of 80m. Releasing this brine would have led to a major environmental incident.
As an educational facility works had to be kept to holiday periods and exam timetables respected.
The solution and benefits: A thorough utility survey was undertaken to inform the system design. As the bore holes were kept shallow to avoid the artesial water, a larger number were needed to create an efficient, long term ground heat collector. Hydraulic modelling supported pipe sizing and collector layout design.
Moling was used to trench beneath the cricket pitch and tennis courts meaning these were playable throughout the installation works.
Given the high level of the water table, an added benefit was the installation of a water bore hole to enable irrigation of the sports fields during dry weather.
Rugby Pitch: The rugby pitch needed to be safe to use and operational the following season. The top soil was stripped, the bore holes drilled and an extensive network of trenches dug to connect them to the 5 manifold chambers.
The trenches were backfilled and compacted in layers which ensured there was no future settling across the pitch. The top soil was reinstated and seeded, which produced an excellent playing surface.
Ground Heat Collector: The 50 bore holes of the ground heat collector were installed in 5 arrays of 10; each connected to a subterranean manifold chamber. These were positioned off the playing area and were specified to bear the weight of mowing and maintenance machinery.
Once the bore holes had been drilled and the U-tubes installed these were flow and pressure tested. Header pipe work was then laid, welded and pressure tested. After the whole ground array had passed its pressure test it was filled with environmentally friendly low toxicity heat transfer fluid.
Energy Centre: Orangehouse Renewables engineers completed Energy Centre installation of 2 Stiebel Eltron WPE-I87 ground source heat pumps with a 1500 litre buffer tank and ancillary items and commissioned the system. The newbuild energy centre was sited in the grounds of the student accommodation blocks with highly efficient pre-insulated pipework installed to supply heating water for newly installed wet radiator systems and pre-heat the hot water cylinders.
Project Outcomes:
The system performed well throughout it’s first winter. The rugby pitch is hosting fixtures. The project has been entered for various awards. Running costs and performance are being assessed and we’ll update this case study once we receive the results.
