One of the most important actions to limit climate change is to decrease worldwide CO2 emissions. A large contributor to worldwide CO2 emissions is the production of heat. Therefore, the recently started transition from fossil based fuels to renewable heat sources is of great importance. Renewable heat sources like geothermal and solar energy often exhibit a temporal mismatch between the availability and demand of heat. Excess heat is available in summer while the heat demand cannot be fulfilled in winter. A solution for this problem is to use heat storage facilities that are able to bridge the gap between winter and summer. Given the needed storage capacity for these systems, high temperature aquifer thermal energy storage (HT-ATES) is one of the best options to do so. At the TU Delft, a combined geothermal well with a HT-ATES installation is currently being prepared. The system is designed to provide the district heating network of the university and possibly a part of the city with renewable heat, and, is set up as a research facility to foster future research.
The performance and feasibility of HT-ATES systems is affected by many factors as previous research showed. Understanding which factors are important, and how these factors impact the project feasibility, would provide a solid basis for future HT-ATES feasibility studies and foster the future use of HT-ATES systems, ultimately resulting in are more rapid reduction of CO2 emissions. However, while low temperature ATES systems are regarded a mature technique, only limited experience is available with HT-ATES. Higher storage temperature and larger storage capacity cause technical challenges and variable performance, resulting in an uncertain business case.
Therefore, we determined the most important conditions that influence the feasibility of HT-ATES and performed a feasibility study for the TU Delft HT-ATES project. Our study shows that the integration of HT-ATES together with a geothermal well on the TU Delft campus is feasible, both technically and financially. Most importantly, the use of HT-ATES leads to twice as much CO2 savings compared to the stand alone geothermal well.
At this moment, the project is in the next, more detailed phase, of the feasibility study to optimize the HT-ATES design and decrease project uncertainty. The feasibility of the project is strongly linked to the performance of the HT-ATES system, which is unclear because of uncertainties regarding the characteristics of the subsurface. Therefore, we are currently working on subsurface characterization by means of drilling, sampling and logging activities and aim to determine which layer(s) are most suitable for placement of well screens for the and determine appropriate, generic, methods for subsurface characterization for HT-ATES systems. In this presentation we will discuss the learning outcomes of the feasibility study for future studies and present our current effort in developing the HT-ATES project.
Stijn Beernink1,2, Martin Bloemendal1,2, Phil Vardon1, Auke Barnhoorn1, Niels Hartog2
1Delft University of Technology (TUD); 2KWR Water Research Institute