The evidence from both the Energy Savings Trust research and from the recently published Department of Energy & Climate Change metering programme shows very clearly that the selection of installation partner for all renewable technologies is key to a successful outcome. With the most appropriate partner on board, the core elements of design excellence, high quality product selection and professional execution will follow. The client is placing very basic quality of life essentials, heating and hot water, into the hands of the installer and a trust that the initial delivery and the ongoing support will meet expectations is vital.
The same applies when selecting a drilling sub-contract partner. Very few ground-source heat pump installers have drilling capability in-house, but the Microgeneration Certification Scheme (MCS) requires the installer to take responsibility for the design of the borehole array if drilling is required to provide the energy resource. Whilst the ultimate sub-contract for the drilling may be placed direct between the client and the driller thereby avoiding an additional layer of cost mark-up, it is the relationship between the MCS certified installer and the driller that is core to the seamless integration between the natural energy resource and the plant room. An equivalent trust needs to be in place.
Once drilling is complete and the probes are installed and grouted, it is extremely difficult for an installer to check the quality of the installation. The trust that the driller has delivered the depths and the quality of probe has to be robust. In an earlier article on Groundworks as Infrastructure, it was demonstrated that drilled ground-source heat pump collectors are an investment in infrastructure with a design life of up to 120 years. Of course, this is only going to be the case if the drilling sub-contractor is capable of, and can be trusted to deliver the contract quality necessary to deliver this longevity.
Going underground to depths which may typically be 120m-180m below ground level is always a risky operation. Whilst all the appropriate care can be taken to research the geology before cutting ground, the underlying bedrock in the UK is a complex structure and, occasionally, the conditions may be significantly different to those reported by even the most exacting desktop study. In such instances, the drilling sub-contractor needs to be technically capable of dealing with any eventuality and, ideally, needs to have taken all the appropriate steps to allow for such eventualities in both how the drilling proceeds to still deliver the energy resource required, and in how any additional costs incurred are managed.
As mentioned earlier, whilst the MCS Standard for heat pump system design places the burden of borehole array design on the installer, there are elements of the drilling process that are the expertise of the driller and that should be protected through the contractor holding their own Professional Indemnity insurance. Once on the ground, a high quality driller will record and provide the drilling log so that the reality on the site can be checked against the desktop expectation; again, this is an MCS requirement. In the case of small to medium drilling requirements, it is rarely economically viable to carry out a formal thermal response test, so this ratification step is essential. Finally, once the drilling is complete, an accurate record of drilling depths is required to aid the installer in balancing the array for optimised energy harvesting that will be sustainable over the design life of this valuable infrastructure.
Taking all the above into account, it is clear that the expectations placed on a drilling sub-contractor are very significant. The energy resource which the driller delivers has to meet the design requirement and the contract has to be fulfilled professionally and in such a way as to minimise site disruption, albeit that drilling is a messy business. The delivered service needs to be evidenced through the provision of drilling logs, flow and pressure certificates and site mapping to the required resolution. Only with all these elements in place can the trust between driller and installer be maintained for the ultimate benefit of the site owner. Whilst cost is an essential factor in any sub-contract, with this particular service, where so much of the delivery is buried and out of visual inspection, value, as measured in quality and cost, is more important.
Over the last five years, isoenergy has built up a trusted partner relationship with a small number of drilling contractors. Chief amongst them is Synergy Boreholes based in Wallingford. Synergy Boreholes has invested in some start-of-the-art drilling equipment and yet maintains an entirely realistic approach to providing value for money. As a sub-contractor, this firm has completely embraced the isoenergy belief that all borehole probes should be RC material and understands that the technical agility to deal with any unexpected geological conditions is an essential element of the service delivery. In addition, Synergy will provide the full package required to assist the installer and client in pre-contract budgeting and in the interpretation of geological studies whether drawn from the British Geological Survey (BGS) or from independent geology consultants such as Tim Baker of B.A. Hydro Solutions. The ultimate test is, of course, the activity on the ground. In this respect, Synergy Boreholes also demonstrate an understanding of what it takes to develop and build the ground-source sector in the UK. If drilling conditions and geological surprises are encountered, Synergy will work with the installer to identify appropriate solutions and to deploy them with minimal delay and with minimal additional costs which are only applied if absolutely unavoidable.
Ground-source heat pump technology is ideally suited to the UK climate and, whilst relatively new to the mainstream in this country, is a tried and proven technology in Europe and the USA. If executed well, the efficiencies of ground-source systems do and will contribute very significantly to the reduction of harmful carbon emissions and will reduce operational costs for the longer term benefit of the building owners. The partnerships between the client, the MCS certified installer and the drilling sub-contractor all contribute absolutely to the quality of the outcome and have to be built on trust. In this, the installer has to support both the client and the driller in the provision of advice on contractor selection and in building the trust, largely by conveying their own trust and carrying this across to the client.
