Heat Recovery from Exhaust Air as a Thermal Storage Energy Source for Geothermal Energy Piles

In pursuit of EU directive 2010/31/EU energy performance targets towards design of nearly zero-energy buildings consideration of renewable energy sources in the design is expected. Application of ground-source heat pump (GSHP) and energy piles in cold climate conditions for utilization of renewable geothermal energy may results in GSHP plant high seasonal coefficient of performance (SCOP) as long as source of thermal storage is considered in plant design. This numerical study investigates exhaust air of air handling unit (AHU) as a source of thermal storage for geothermal plant with energy piles, that can be utilized via air-to-liquid heat exchanger installed at the exhaust side of AHU after the rotor heat exchanger and exhaust fan. Modelling is performed in dynamic whole year simulation environment Equa IDA-ICE, where reference commercial hall-type building model is coupled with detailed custom heat pump plant. Exhaust air thermal storage capacity in multiple energy piles field configurations with varying soil conditions, distance between piles and pile lengths is analyzed. Results revealed that exhaust air thermal storage appears to be highly cost effective solution. Graphical figures presented in this paper can be further applied for preliminary exhaust air thermal storage capacity assessment in buildings with energy piles.