This study examines the technical, logistical, contractual and economic feasibility of installing a Deep Geothermal Single Well (DGSW) system at the new site of the Aberdeen Exhibition and Conference Centre (AECC). The site offers a unique opportunity for installing a DGSW as it can be used in four ways:
1. To supply low carbon heat to a commercial development (AECC)
2. To supply low carbon heat to nearby residential units using an innovative low temperature heat network
3. Act as a catalyst for deep geothermal energy in Scotland by using the AECC as a showcase project as well as an educational tool for increasing public awareness of the sub-surface
4. Develop cross-over skills with the established oil and gas industry
The DGSW has been developed by Geothermal Engineering Ltd (GEL) to overcome some of the barriers that have hindered the deep geothermal industry in the United Kingdom. The system has been designed to reduce the geological risk, the project delivery time and the cost of delivering deep geothermal heat to buildings. Further, the system does not require 'fracking' or hydraulic stimulation in any form. It is therefore more likely to be acceptable to the public than geothermal projects that involve some form of 'stimulation' techniques. This has recently been demonstrated at an urban site near Crewe where a DGSW project achieved the necessary planning permission and permitting to drill within 3 months and received unanimous public support.
The DGSW consists of a 2km vertical well that is drilled and cased with standard oil and gas equipment. A small submersible pump and an insulated central pipe extending to the base of the well are installed in the centre of the well. Hot water is drawn up through the pipe from the bottom of the well and the heat extracted from the water via a heat exchanger for distribution in the building. The cooler water is then rejected back to the top of the well and descends to the bottom of the well via gravity, heating up on the way before being circulated again. The system has been successfully proven in a field trial in 2014 (funded by the Department of Energy and Climate Change) and delivered 40kW of heat for every 1kW of electricity used in the pump, i.e. an "efficiency" of 4000%. Peak heat outputs from each DGSW are between 400 and 600kW or enough to supply heating to around 200 homes. It is a simple system that, once installed, has no visual impact and can be sited near to the buildings or plant that require heating.
Unlike other types of deep geothermal systems, the DGSW is not overly constrained by the underlying geology and does not rely on the presence of a high permeability, high enthalpy resource. The lack of geological constraint means that the DGSW could be replicated across Scotland. It therefore offers the most realistic method of kick starting the commercial development of a deep geothermal heat sector in Scotland and beyond.
In Scotland, the deep geothermal resource at a depth of between 2 and 3km is sufficient to provide more than enough heat than is realistically possible to deploy in the next 20 years. We therefore believe that limitations to the deployment of deep geothermal heat systems will not be resource constrained but by logistics such as sufficient heat demands at the surface, presence of a network, procurement constraints (buildings in public ownership), drilling rig access, finance and public acceptance.
As the DGSW is vertical, there are no third party ownership issues caused by drilling under other landowners (i.e. no requirements for directional drilling). This is very important in the United Kingdom, as there is no legislation regarding heat ownership and therefore no geothermal licensing framework.
As a demonstration site for the technology, the new AECC development is an exciting location. The site has significant space for drilling, good road access, a good heat demand match and can serve as an international showcase for the technology (and other renewable energy sources) for visitors to the new exhibition and conference centre. As part of the innovative use of renewable sources at the site, it is proposed that the DGSW provides the base heat requirement for the on site anaerobic digester. This would remove the need for an on-site CHP unit and the need to import gas. The return heat flow from the digester will then be used to provide heat for a number of nearby residential dwellings using a low temperature heat network. Therefore, with one demonstrator unit, two sustainable heating uses (commercial and domestic) can be demonstrated simultaneously. We also suggest in this report that the new AECC site could offer the potential of being an interactive 'Deep Geothermal Energy Exhibition' to improve public perception and understanding of the subsurface but also provide a major outreach opportunity for school children to become interested in geoscience and sustainable geo-energy.
The proximity of the new AECC to Aberdeen also means that there is the opportunity to develop a technical and commercial skills crossover with the established oil and gas industry. This report argues that, due to the existing oil and gas skills in Aberdeen, Scotland is in a unique position to be the first mover in the UK in the development of a deep geothermal energy industry and to roll out a commercial and technical deep geothermal supply chain.
We have explored the permitting that would be required for the DGSW at the new AECC site with both the Scottish Environment Protection Agency and Aberdeen City Council and have shared the documentation that we developed for a recent DGSW project at Crewe as guidance. We have also included a section on contracts and insurance, as we believe that these will be important aspects of delivering a successful deep geothermal project on time and on budget.
A financial model and a Lifetime Carbon Assessment (LCA) have also been completed. The LCA shows that, over the lifetime of the plant, the CO2 savings compared to a conventional gas boiler are 22,170 tCO2e. It is considered that, due to the very high overall efficiency of the system, the commercial roll out of the DGSW could make a significant contribution to aim of decarbonising Scotland's heat supply.
The capital costs for the project are well understood due to recent experience of a similar development in England. Further, they can be well constrained due to the structure of the drilling contracts that would be used on the project. The total cost of delivering the demonstration project at the AECC will be £2.3m.
The commercial appeal of the DGSW is aided by the fact that the system can typically be installed in under 24 months (including planning and permitting). This is significantly shorter than traditional deep geothermal systems. The cost data for the DGSW highlight that compared to traditional deep geothermal systems (which would require directional drilling and more than one well) that it is the lowest cost option available.
The next stage in the development of the project will be to move forward with the permitting and drilling of the well at the site. This would represent a major step forward in the development of deep geothermal heat resources in Scotland and, due to the high profile of the new AECC, attract significant public interest.
Drilling and developing a DGSW at the AECC site will offer a number of benefits:
- Demonstrate that deep geothermal heat can be provided at low risk in Scotland
- Provide a high profile showcase site for deep geothermal heat supply to commercial and domestic users
- Offer the opportunity for the creation of a deep geothermal exhibition and education centre.
- Benefit the immediate local community via return flow heating to dwellings
- Provide much needed temperature and geological data from deep on-shore drilling
- Develop a system that does not require fracking or "stimulation". This will be important for ensuring that the local community are on side
- The commercial opportunity for the DGSW and deep geothermal energy in general can be showcased to the widest possible audience
- The location can help to establish cross over and supply chain links between the deep geothermal industry and the oil and gas industry in Aberdeen
Email: Johann MacDougall
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