Case Studies

Calderdale Closed Loop Case Study

Closed-loop ground source heat pump viability assessment and borehole array design two listed public buildings, Yorkshire

Carbon Zero Consulting worked closely with Sweco UK and Calderdale Council to develop a GSHP concept and to provide GSHP borehole designs to progress the projects to full tender stage.

Calderdale Council are progressing a far-reaching project to replace oil and gas-fired boilers in a number of their large public buildings.

An initial viability assessment identified two listed properties as being candidates for installation of ground source heat pump (GSHP) renewable heating systems.

Carbon Zero Consulting were contracted to provide an assessment of whether an open-loop or closed-loop borehole system was better suited and to then take the design to a stage suitable for issue of tenders for detailed design and installation.

It was quickly established that within the timeframe available for the projects, open-loop was not a viable solution.

A detailed geological assessment was then made to support a closed-loop borehole array design model.

The geology beneath each site was assessed to be similar in that both required drilling through coal-measures and millstone grit formations.

The coal-measures had been mined nearby to each project and so the Coal Authority was consulted and drilling permits obtained.

A test borehole was designed and drilled at each site and a thermal response test (TRT) performed on each to measure the thermal conductivity of the drilled formations.

The results of the TRT were then utilised within a closed-loop design model to derive borehole array solutions. The resulting test results and geological appraisals were utilised within design-and-build tenders issued to candidate installers.

Results of one of the thermal response tests (TRT).

One of several model outputs for borehole array temperature and GSHP efficiency.

Possible closed-loop borehole array layouts for one of the projects.

Artesian groundwater flowing from the GSHP abstraction borehole during a geophysical survey.

The drilling rig in action on the GSHP abstraction borehole.

The finished hotel and spa with the GSHP abstraction borehole chamber and manhole in the foreground.

Grantley Hall Hotel and Spa, North Yorkshire

Ground source heat pump and borehole water supply

Carbon Zero Consulting worked closely with the Hotel owners and Wheatley M&E Services Ltd to develop the concept and to provide all designs, regulation and implementation for heating, cooling and water supply.

The stunning new hotel and spa was developed from an old manor house previously used as a training college. There was insufficient water supply and no gas connection for the new development. The client had a clear commitment to having no visible or audible plant for heating and cooling. A ground source heat pump (GSHP) system was recommended.

Carbon Zero Consulting established from an initial test borehole that a closed-loop borehole system was not viable as very strong artesian pressure was identified within the underlying rock formations of the millstone grit. Drilling of a large number of closed-loop boreholes was judged to be not technically possible. The concept of using groundwater in an open-loop GSHP system was developed in parallel with a third borehole to supply water for the hotel and spa facilities.

Carbon Zero Consulting worked with Drilcorp Ltd to drill and test two boreholes for the GSHP system and a third for water supply. Drilling in strongly artesian conditions (in excess of 6-bar pressure) was complex but was successfully completed using two ‘strings’ of steel casing, heavily weighted drilling mud and many years of relevant experience.

The GSHP abstraction and injection boreholes are separated by over 400m to greatly reduce the potential for thermal interaction. Test-pumping determined that a groundwater flow rate sufficient to provide the heating and cooling demand was available from one borehole, and despite the 6-bar over-pressure, re-injection of the water to the aquifer was found to be viable. Heating and cooling using the flow of groundwater is provided by a skid-mounted IFtech GSHP system located in the hotel plant room.

The system has been in operation successfully since 2019.

The largest Water Source Heat Pumps in England

Soft fruit growing season extended by use of renewable heating

Carbon Zero Consulting worked closely with two clients and Ebtech Energy Systems to design, install and provide regulatory compliance for England’s two largest Water Source Heat Pump (WSHP) systems.

The first WSHP has been operating on the river Loddon since autumn of 2020 and the second will be completed by the end of 2021 on the river Medway. Each uses renewable heat generated by the 8.8MW heat pump system, allowing the clients to produce soft fruit outside the normal growing season. Domestic production of soft fruit also greatly reduces ‘food- miles’ associated with imports from around the globe.

The process began with Carbon Zero Consulting assessing the viability of each river to be a reliable year-round energy source, which would ensure peak load heating during the coldest winter days. This required analysis of river flow, seasonal temperature and optimum locations for the abstraction and discharge structure. A wastewater treatment outflow to the river Loddon was utilised to boost system efficiency.

Prior to installation, the Environment Agency regulatory requirements were completed by Carbon Zero. These included an application for abstraction and discharge, a ‘Flood Risk Activity Permit’ and assessment of ecological impact for the peak 640 litres per second river abstraction. The thermal impact on either river was shown by computation to be negligible.

The system on the river Loddon operated through the winter/Spring of 2021 with peak load being maintained despite running through some of the coldest temperatures recorded in the last decade.

It is estimated that, over the next 20 years the plant will save 44,000 tonnes of carbon emissions when compared to gas heating.

A view of the GSHP plant room and pipework connecting to the river abstraction and discharge structure.

The abstraction and discharge structure on the River Loddon.

The location of the 8-borehole system and previously installed 1MW shallow ground array

Example of test pumping data during abstraction and re-injection

Ground Source Heat Pump Provides Multi-Mega-Watt Heating for Specialist Plant Grower

East Yorkshire

Carbon Zero Consulting, a part of RSK Environment Ltd, worked alongside Ebtech Ltd to develop the concept and to provide all borehole designs, management of all drilling and testing and EA regulatory requirements for this large ground source heating system.

The client is one of Europe’s largest independent specialist growers of ornamental plants located in East Yorkshire, UK. The client had a clear commitment to reducing fossil fuel consumption and to greatly improve their security of supply for heating. Their plant growing business relies entirely on a secure and continuous supply of heating, with a peak heating requirement of circa 1.5MW. A shallow (trenched) ground source heat pump (GSHP) system of 1MW capacity was installed as a separate project, and the client wished to add to this. A borehole-based GSHP system was considered as the best long-term solution.

Carbon Zero provided a detailed assessment of the viability of a GSHP system and reviewed the potential for either closed-loop or open-loop boreholes. Drilling of a very large number of closed-loop boreholes within the underlying chalk aquifer was judged to be not technically possible as the chalk is highly fractured and difficult to support while drilling. The concept of using an open-loop GSHP system was developed and initial applications made to the Environment Agency (EA).

Carbon Zero Consulting worked with an experienced drilling contractor to drill and test an initial two boreholes for the GSHP system. Results from these established that additional boreholes would be required. Computation and hydrogeological modelling were utilised to compute the position of additional boreholes.

In all, 4 abstraction and 4 injection boreholes were drilled to a nominal depth of 30m within the chalk aquifer. Test-pumping of the 8-borehole system was a highly complex undertaking, but successfully determined that a groundwater flow rate sufficient to provide the peak heating (and cooling if required) was available from the 4-borehole abstraction array.

The system was first licensed by the EA in early 2020 and has been in operation since this
The layout of the shallow, trench system and the 8 borehole open-loop system is shown below.