Final Colloquium: Jasper Hoving
11.00 - 13.00
Maintaining ATES balance using continuous commissioning and model predictive
A rapidly growing amount of office buildings in the Netherlands is using an Aquifer Thermal Energy Storage (ATES) system. An ATES system uses two groundwater storage wells with different temperatures. During summer, a well pump extracts groundwater from the coldest well for building cooling. The returned (warmed) water is injected and stored in the warmest well. During winter this process is reversed to provide heating. An optimal functioning ATES system can significantly reduce energy use and CO2 emissions of an office building.
Office buildings typically store much more heat than cold, causing the entire underground slowly to heat up resulting in cooling capacity problems on the long term. To avoid this, a thermal energy balance of the system is an essential condition for optimal ATES operation. The ATES balance is corrected by cooling groundwater via cold outdoor air during the winter, called regeneration. (model-based) Continuous Commissioning (CC) is used to check if the intended amounts of energy are stored in the ATES system. Model Predictive Control (MPC) is used to control the amount of regenerated cold to maintain the ATES balance. Both methods use the same reference model to calculate the intended storage amounts (CC) and use as prediction model (MPC).
A reference model is developed for the Kropman Utrecht case-study building. The analysis of CC revealed a combination of hardware and software problems in the HVAC system. Around 30% of the generated cold is not stored in the ATES system, around 10% of the heat didn’t need to be stored in the ATES and the use of district heat can be reduced by 60%. As result, the building should generate a significant surplus of cold instead of heat. Using MPC it is possible to keep the ATES in balance over a simulated 20-years period. For the case-study building it can be concluded that the combination of CC and MPC, using the developed reference model, is capable of maintaining the ATES balance.