Heatstore: High Temperature Underground Thermal Energy Storage

Heatstore after one year

Heatstore is one of the nine projects under the European GEOTHERMICA – ERA NET COfund umbrella. It is partly funded by the Dutch Netherlands Enterprise Agency (RVO) and it has been up and running for a year now. The main objectives of the Heatstore project are to reduce costs and risks while improving the performance of underground thermal energy storage technologies at high temperatures (25–90°C). The study is also targeting the optimisation of the use of sustainable heat flows in heat networks with geothermal energy and heat storage. Alongside generic research looking at storage options, efficiency and thermal impact, Heatstore will also collect practical knowledge and data through six new demonstration projects and eight case studies of existing systems with different configurations of heat sources, heat storage types and heat utilisation approaches. The idea is that this practical knowledge will help to make technologies for the underground seasonal storage of sustainable heat ready for market uptake and to fulfil the maximum utilisation potential of geothermal heat production in the European energy transition.

KWR is working on the Dutch part of the project with TNO, the consultancy firm IF Technology and the Netherlands Institute for Ecology NIOO-KNAW. These partners are conducting two case studies, one at the horticulture company Koppert-Cress (KWR) and one at NIOO-KNAW (NIOO and IF). In the meantime, the first test drilling operations have been completed for the Wieringermeer Energy Combination (ECW) pilot project in North Holland (ECW and IF).

Monitoring at Koppert-Cress

Koppert-Cress is a horticulture company that needs relatively large heat supplies. An Aquifer Thermal Energy Storage (ATES) system was built in the past to heat and cool the greenhouses in a sustainable way. A few years ago, it was converted into a HT-ATES system in order to store higher temperatures (>25°C). Koppert-Cress was granted a provisional pilot permit for the HT-ATES system, which is being studied extensively to learn more about the behaviour of heat and groundwater at relatively high temperatures (up to 40°C) in shallow aquifers.

In order to increase our understanding of how heat stored underground is spread and to be able to measure the changes in water quality associated with changes in temperature, a monitoring well was drilled near one of the warm wells in the ATES system. We can take water samples around this well from the aquifer and then assess the changes in water quality in the laboratory. In addition, two additional Distributed Temperature Sensor (DTS) cables have been installed to measure the temperature distribution over the full depth of the aquifers used for heat storage down to 170 m below the surface.

Models benchmark

Most partners in the Heatstore project use public/private software packages that they have developed themselves to model heat storage and determine the efficiency and impact of storage systems of this kind. These software packages are often made for a specific purpose and they differ from each other. As a result, it is interesting to compare them in a benchmark study: all the parties will carry out a number of identical simulations and the results will be compared. That provides a picture of the accuracy of different simulation tools for different systems and ensures that important processes are simulated correctly in all models.

This study began last April with a workshop in Geneva attended by Martin Bloemendal and Stijn Beernink.

Heat storage linked to a heat network in Westland

A collective of market gardening firms in the Westland area, which also includes Koppert-Cress, is working on the development of a heat network fed by geothermal energy. The application for the grant (SDE+) for the construction of the geothermal energy source was submitted in 2018 and approved in 2019. Work is proceeding on the business case at the moment. A heat storage system may be part of the heat network being installed. KWR is exploring the options for a heat storage system in this area. That involves looking at several parameters, including the following:

  • heat production and demand during the year and therefore the potential for summer storage;
  • geohydrological suitability;
  • the estimated efficiency of the heat storage system.

Several geothermal projects are already in place in the Westland area (including Greenwell Westland, Geothermie De Lier, Aardwarmte Vogelaer, Nature’s Heat and Geopower Oudcamp).

Click here for more information about this initiative (in Dutch only).

In 2020, the Heatstore project will analyse the data from the case studies more closely and use them to calibrate heat storage models. There will also be generic research into the efficiency and impact of heat storage using various temperatures, volumes and aquifer types.