A Multiple Load Aggregation Algorithm for Annual Hourly Simulations of GCHP Systems

This article presents a technique to aggregate heating/cooling loads when using the cylindrical heat source method (CHS) to perform annual hourly energy simulations of ground-coupled heat pump (GCHP) systems. The technique, referred to as “multiple load aggregation algorithm” (or MLAA), uses two major thermal history periods, referred to as “past” and “immediate.” In addition, the MLAA accounts for thermal interference among boreholes by numerically solving the two-dimensional temperature field in the borefield. Results of a comparison between the MLAA and the duct storage (DST) model are presented. Several cases are examined with two different borefields and several load profiles. Results obtained for one- and ten-year simulations show that the MLAA is in very good agreement with the DST model. In the worst case, the maximum difference in fluid temperature is of the order of 2 K (3.6°F). This level of precision is more than adequate to perform accurate hourly simulations of GCHP systems.