RECOIN - Real-time control and tuning of borehole heat exchanger fields for optimal integration in heating and cooling systems

Borehole heat exchanger (BHE) fields combine many individual BHEs for the supply and storage of heat and cold. The worldwide installed capacity of the currently more than 100,000 fields in operation is estimated to be 1.5 GW with expected market growth rates of nearly 10% in Europe. The fields are usually designed based on standardized layout concepts that rely on deterministic assumptions of the ground conditions, of the technological performance and of the energy demand that needs to be fulfilled. Considering that BHE fields run for a lifetime of decades, however, any uncertainty in these assumptions results in suboptimal operation in the long term. In fact, uncertainty always exists. This compromises the economic and environmental advantage of any installation, and in the most extreme case even causes failure, which ultimately hampers the reputation of shallow geothermal systems as reliable and robust renewable energy technologies. In the RECOIN project, a new type of control system is being developed that monitors the thus far largely uncontrolled operation of such fields, regulates individual BHEs in a smart way and continuously adapts them for optimal overall system efficiency. The most important development of the project is a flexible modeling, prediction and control procedure that will be integrated into a new device for model predictive control. The technology will leverage operational data, physical modeling and machine learning. It will adapt the ground-load dynamically for individual BHEs based on monitoring the thermal conditions in the field while accounting for expected energy needs that should be satisfied by the installation in the future. This way, BHE fields will be operable at optimal performance while integrating current and expected future in-situ conditions, capacity and demand to arrive at a highly reliable and resilient implementation. Based on the theoretical results from preliminary studies, control of a BHE field without individual BHE tuning can already reach more than 20% savings of total CO2 emissions. Therefore, the economic and environmental improvement potential by the proposed RECOIN device is expected to be substantial. The project will be carried out by an interdisciplinary and intersectoral consortium from Germany, Sweden and Switzerland involving partners from academia, authorities and private enterprises. The focus of the research work is on the setup, construction and calibration of the novel real-time controller device and the experimental testing of the control system. It will be applied by the partners as a prototype to a highly monitored field site in Switzerland. Through synchronized application to demonstration fields in Berlin and Stockholm, the basis for flexible practical utilization is established.