Simulation and implementation of heat load shifting in a low carbon building

A predictive load shifting control system for a heat pump has been developed and installed in a low carbon test house located at the BRE Innovation Park, Motherwell, near Glasgow. The house features an exhaust-air source heat pump supplying an under floor heating system. The controller predicted the day-ahead space heating requirements for the house, based on forecast air temperatures and solar radiation levels and then automatically set the heat pump’s start and stop times for the following day. The heat pump’s operation was restricted where possible to off-peak electricity tariff periods (00:00-07:00). The controller’s operating parameters were pre-set using a calibrated building simulation model. After installation, the controller’s performance was monitored during September 2015 and analysis of test data showed that the predictive control maintained indoor air temperatures between 18-23oC for around 87% of notional occupied hours between 07:00-22:00; this was better than predicted by simulation. However, the energy performance of the heat pump was extremely poor as it did not function well under intermittent load-shifting operation, with the majority of the heat was delivered primarily by an auxiliary immersion coil rather than the heat pump itself. The paper concludes with suggestions for refinements to the controller and further work.