In Norway, over 40% of electricity consumption is used for heating and cooling, while the industry generates around 20 TWh of waste heat annually. Some of this, such as thermal energy from waste incineration, is utilized in, e.g., hydronic district heating systems. However, due to fluctuations in demand and limited systems for heat recovery, a significant amount of industrial heat energy goes to waste. Implementing flexible and large-scale storage systems for thermal energy can help balance supply and demand, thereby reducing national electricity demand, thereby reducing cost and emissions related to electricity production.
The subsurface offers an option for thermal storage that is in principle infinitely scalable. However, high development costs and large uncertainties related to subsurface properties often makes it challenging to justify investments. Digital optimization, monitoring and numerical simulation tools hold great potential to better understand the behavior of the subsurface, but these technologies need to be properly applied to industrial problems to drive down uncertainties and cost. How this can be achieved remains an open question, which the GHOST-DigiT project aims to address. Here, SINTEF and four industry partners within geoenergy, waste incineration, district heating and real estate aim to de-risk and realize the full potential of underground thermal energy storage by developing and adapting technologies that permits establishing "digital twins" of the geothermal plans and their environments. The goal is to provide real-time understanding, prediction capabilities and short- and long-term optimization of operations, thereby paving the ground for efficient use of the subsurface as an efficient "heat battery" and a key component of a future flexible and sustainable energy system.
Geological thermal energy storage is a concept where excess heat from industrial processes or other human activities is injected into the ground for later (long or short term) recovery and use, e.g. for district heating. The green shift of the energy sector will require rapid uptake of renewable energy sources of intermittent nature, which will require massive additions of energy storage. Considering that around half of EU energy consumption relates to heating and cooling, widespread use of geological thermal energy storage holds the potential to significantly reduce energy (including electricity) demand and balancing a future, more dynamic energy system.
While using the subsurface as a thermal battery is appealing for multiple reasons (flexibility, scalability, low environmental impact and footprint), efficient use of the subsurface can be very challenging due to a large number of uncertain factors and parameters. In the GHOST-DigiT project, SINTEF Digital together with five industry partners within geoenergy, waste incineration, district heating and real estate, aim to de-risk and realize the full potential of underground thermal energy storage as a key component of the future energy delivery system by developing enabling technologies for digital twins, a real-time subsurface monitoring/data assimilation and simulation framework providing an in-depth and real time understanding and forward prediction capabilities of the relevant underground processes, supporting short- and long-term optimization of operations, and paving the ground for cost reductions and efficient utilization and planning of the subsurface as a thermal energy storage resource. The industry is well represented in the project, with multiple financing partners and three real heat storage sites to use as case studies for developing, data collection and testing.