3<\/sup> per hour from one well from around 2.5km deep and reinjected into the same underground reservoir via a second well after thermal energy is extracted. The return temperature governs the heating power, and this will be maximised when heat demand is high via a large heat pump.<\/p>\nResearch focuses on the behaviour of the subsurface and resource utilisation. The key questions are: how can we best understand the fluid and heat flow behaviour in the subsurface, and how does this influence the project lifetime and any unwanted impacts? A major societal concern is whether seismicity could occur. As fluid is reinjected (unlike in gas extraction projects), there is a limited influence from the fluid pressure, but as the reservoir rocks cool, they also contract. However, there has not been measured seismicity in geothermal projects in this geological setting; therefore, it is a key question why not. To investigate the key questions, we are installing fibreoptic cables to measure the temperature, pressure, and acoustic emissions in both wells, taking extensive rock cores and installing a local seismic monitoring station (see Fig. 3). In addition, we will install a dedicated monitoring and exploration borehole, which will be equipped with electromagnetic geophysical instruments (and other instrumentation) to around 4.5km deep. This is targeted to allow a 3D image of the hot and cold fluid in the reservoir, allowing key insights into how geothermal fluids move in such a reservoir \u2013 one which was created by millions of years of river meanders. The research infrastructure is funded by the Dutch Research Council (NWO) via two main projects (EPOS-NL and EPOS-eNLarge).<\/p>\n
Heat storage<\/h3>\n Geothermal energy projects can provide energy 24 hours per day, 365 days per year, and as a result, there is a heat surplus in summer, while capacities are usually insufficient to provide peak demand in winter. Seasonally storing thermal energy at temperatures ranging from 50-90\u00b0C in constructed storage systems such as tanks is problematic, as they would take up a lot of space (order of magnitude for the TU Delft campus: 250 Olympic swimming pools) and are therefore expensive, especially in large urban areas. Hence, High Temperature Aquifer Thermal Energy Storage (HT-ATES), where thermal energy is stored in the subsurface (in aquifers, which are permeable subsurface layers) has large potential, as they are relatively cheap to tap into and require negligible space at surface.<\/p>\nFig. 3: Photo of the installation of the local seismic monitoring station and sampling taken during installation (photos by P Vardon and S Beernink)<\/figcaption><\/figure>\nHowever, storing heat in natural aquifers at temperature levels greater than 50\u00b0C comes with many challenges regarding material use, recovery efficiency, groundwater quality, system integration, and societal engagement. At TU Delft, a HT-ATES system will be installed and operated in conjunction with the geothermal well. The installation, demonstration and research is partially performed by the PUSH-IT project funded by the European Commission. The HT-ATES system will be extensively monitored and used to optimise performance and minimise GHG emissions of the entire system. Key elements in the research and developments of the HT-ATES system are mapping the subsurface characteristics, which are highly variable due to them being a natural system (see the results of a downhole log and CT-scans of sampled material in Fig. 4) and impact on the heat distribution in the subsurface. In addition, key aspects of societal engagement, policy and permitting, and societal perceptions will be investigated.<\/p>\n
TU Delft has its own district heating network (DHN). It consists of five different tracks and provides heating to the old buildings on campus. Originally, in the 1950s, a coal-fired boiler provided heat to these buildings. Currently, a combined heat and power plant and gas-fired boilers feed the DHN, but these will be largely replaced by the geothermal energy well and HT-ATES, and only run for peak supply and back-up. This will have the consequence of reducing the supply temperature of DHN. These conditions are representative of many other cities\/buildings, where old buildings need to be retrofitted to be able to utilise lower temperature heating. Together with the large heat pump, the different tracks allow for experimenting with different optimisation approaches regarding insulation measures, control strategies and demand side management.<\/p>\nFig. 4: Detailed logging and coring analysis, to obtain comprehensive and detailed insight into the subsurface composition and characteristics (provided by S Beernink)<\/figcaption><\/figure>\nOutlook<\/h3>\n With the Delft Subsurface Urban Energy Laboratory, the TU Delft community is ready to investigate resource efficiency during the entire operational life of the geothermal energy production and heat storage facility. With the deep well, we also create the ability to explore geothermal energy potential at increased depth. With core analysis providing ground truth information and geophysical monitoring providing information on changes in the temperature distribution over time, we aim to understand the heterogeneity of the geothermal reservoir, the existence of preferential flow paths, and possibly on the (re-)activation of presently undetected but existing faults.<\/p>\n
The heat storage facility on the TU Delft campus allows us to monitor the efficiency and safety of operation and provide knowledge on how to deal with large fluctuations in the storage and production cycles. Finally, groundwater protection is an important topic of investigation. Producing hot water through shallow aquifers, as well as operating a HT-ATES system, will have an impact on the surroundings. Shallow subsurface monitoring of thermally induced flows, changes in geochemical reactions and biological activities will inform on how to protect the environment, deemed essential for public health and biodiversity. These aspects are all critical for upscaling the use of geothermal energy from a niche energy source to a major contributor to the energy system.<\/p>\n
The research and facilities discussed in this article are used and implemented in our education. TU Delft offers various online courses, which are open to anybody in the world. In our on-campus education, an example is the heat-track in the Masters programme \u2018Sustainable Energy Technology\u2019.<\/p>\n
Acknowledgements<\/h3>\n This sort of facility cannot be realised without extensive work by a large group of colleagues and partners, of whom there are too many to list here. Key funding partners for the scientific part are the Dutch Research Council (NWO) via the EPOS-NL and EPOS-eNLarge projects, the European Commission Horizon Europe via funding of the PUSH-IT project, and commercial partners who invest in the infrastructure (Aardyn, EBN and Shell Geothermal). Within TU Delft, a wide variety of departments have contributed: the Faculty of Civil Engineering and Geosciences, Campus Real Estate, the Urban Energy and Powerweb institutes, and the Innovation & Impact Centre. Key colleagues within the Faculty of Civil Engineering and Geosciences are Susanne Laumann, Hemmo Abels, Guy Drijkoningen, Auke Barnhoorn, Denis Voskov, Liliana Vargas Meleza, Anne Pluymakers, Alexandros Daniilidis, Sebastian Geiger, and the implementation team. Key research partners are Utrecht University, KNMI and TNO from the EPOS-NL\/eNLarge consortium and 19 partners from around Europe from the PUSH-IT consortium.<\/p>\n
References<\/h4>\n\nGoldstein, B., G. Hiriart, R. Bertani, C. Bromley, L. Guti\u00e9rrez-Negr\u00edn, E. Huenges, H. Muraoka, A. Ragnarsson, J. Tester, V. Zui (2011): Geothermal Energy. In IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation [O. Edenhofer, R. Pichs-Madruga, Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel, P. Eickemeier, G. Hansen, S. Schl\u00f6mer, C. von Stechow (eds)], Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA<\/li>\n IRENA, IEA and REN21 (2020), Renewable Energy Policies in a Time of Transition: Heating and Cooling, International Renewable Energy Agency, International Energy Agency and Renewable Energy Policy Network for the 21st Century, www.irena.org\/publications\/2020\/Nov\/Renewable-energy-policies-in-a-time-of- transition-Heating-and-cooling<\/li>\n Stringfellow, W. T. and Dobson, P. F. (2021), \u201cTechnology for lithium extraction in the context of hybrid geothermal power\u201d, Proceedings of the 46 th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, 15-17 February 2021, https:\/\/pangea.stanford.edu\/ERE\/pdf\/IGAstandard\/SGW\/2021\/Stringfellow.pdf<\/li>\n Sanjuan, B., Gourcerol, B., Millot, R., Rettenmaier, D., Jeandel, E. and Rombaut, A. (2022), \u201cLithium-rich geothermal brines in Europe: An up-date about geochemical characteristics and implications for potential Li resources\u201d, Geothermics, Vol. 101\/May, https:\/\/doi.org\/10.1016\/j.geothermics.2022.102385<\/li>\n IRENA and IGA (2023), Global geothermal market and technology assessment, International Renewable Energy.Agency, Abu Dhabi; International Geothermal Association, The Hague. ISBN: 978-92-9260-495-0<\/li>\n https:\/\/iea.blob.core.windows.net\/assets\/ada7af90-e280-46c4-a577-df2e4fb44254\/Renewables2022.pdf<\/li>\n<\/ol>\nPlease note, this article will also appear in the fourteenth edition of our\u00a0quarterly publication<\/a>.<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"Learn about how recent discoveries of geothermal energy have the potential to help power the renewable energy transition.<\/p>\n","protected":false},"author":22,"featured_media":32726,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[24204],"tags":[529,628,24495],"acf":[],"yoast_head":"\n
Producing geothermal energy in the Delft Subsurface Urban Energy Lab<\/title>\n \n \n \n \n \n \n \n \n \n \n \n \n \n\t \n\t \n\t \n \n \n \n \n \n\t \n\t \n\t \n