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Schlagwörter:
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Zusammenfassung:
The European project PUSH-IT’s ambition is to overcome the seasonal mismatch between heat
demand and heat generation from sustainable sources using Underground Thermal Energy
Storage (UTES) at high temperatures, i.e. up to 90°C (https://www.push-it-thermalstorage.eu).
PUSH-IT showcases three UTES technologies at six pilot sites: Aquifer Thermal Energy Storage
(ATES) in the Netherlands and Germany, Mine Thermal Energy Storage (MTES) in Germany and the
UK, and Borehole Thermal Energy Storage (BTES) in Germany and the Czech Republic.
Water quality issues represent technical challenges for viable long-term thermal energy storage,
whatever the technology. These include:
Biogeochemical perturbations in the storage reservoir: the temperature gradient influences the
chemical composition of the fluids that may lead to (bio)clogging in near-wells and loss of
injectivity/productivity, notably for ATES;
Corrosion and scaling in the wells and facilities;
Shallower aquifer perturbation by temperature increase and saline brines from deeper
aquifers.
The lessons learnt over decades of geothermal exploitation and low temperature thermal energy
storage provide a solid basis for anticipating, monitoring, managing and remediating these issues
in a variety of geological contexts. However, for increasing the temperatures of thermal energy
storage in geothermal reservoirs several specificities have not been thoroughly investigated, such
as the thermal storage at high temperature, the need to use reversible wells, reversible fluxes in
the reservoir, temperature and pressure cycling. Furthermore, the role of microbiology has often
been neglected and is anticipated to be more sensitive in storage applications.
At the current stage of the project, the main concerns for each site have been mapped. The
modelling and monitoring works are at different stages of progress depending on the sites.
Significant methodological work is being carried out on microbiological phenomena and on the
elaboration of monitoring protocols.
The project will go beyond the simple feedback on the experience from pilot sites by providing
recommendations to anticipate and deal with water quality issues for future sites. We will provide
guidelines to assist decision-makers in identifying the main issues, in implementing the necessary
modelling, in sizing and adjusting the monitoring plan, in assessing possible water treatment
benefit vs. environmental impact. Anticipating and managing water-related issues as far as
possible is the best way of making the right choices, guaranteeing the performance and longevity
of operations, limiting environmental impact and encouraging society engagement and support.
