18 May 2017

O.2.7.2 Model predictive control to Maintain ATES balance using heat pump

A rapidly growing amount of sustainable office buildings in the Netherlands is using an Aquifer Thermal Energy Storage (ATES) system. An ATES system uses a well pump to extract cold groundwater for cooling with the use of a heat pump if necessary. An essential condition for optimal ATES operation is the thermal balance of the system. Office buildings typically store much more heat than cold, causing the entire underground slowly to heat up and causing cooling capacity problems on the long term. This is compensated by using cold outdoor air to store additional cold during the winter, called regeneration. Model Predictive Control (MPC) is used to control the amount of regenerated cold to maintain the ATES balance. The key element in the method is the reference model built from Big Data learning by the Building Energy Management System, to calculate the expected behaviour of the system and use it as model for MPC for the heat pump. Using MPC it was possible to keep the ATES in balance over a simulated 20 years period. By using a slight cold surplus as target, the effect of exceptionally warm winters is minimal and extraction temperatures are very constant. For the case study building it can be concluded that MPC, using the developed reference model, is capable of automatically controlling the heat pump and maintaining the ATES balance. Because the case study building type and size is comparable to the majority of the new Dutch office buildings, it is expected that large parts of the method are universally applicable.