Comparison of Multiple Load Aggregation Algorithms for annual hourly simulations of geothermal heat pumps

In most geothermal heat pumps installations, the vertical ground heat exchangers (BHE) represent the most important cost item and a careful analysis is needed to assure a long time performance together with the economical sustainability of the project. The most efficient way to predict the temperature evolution in time and space of a ground volume in contact with a system of BHE, is the recursive calculation of basic temperature response factors. Furthermore hourly load simulations along multiyear periods are considered the most reliable approach for simulating the thermal interaction between the ground and a system of BHEs. In this paper the Multiple Load Aggregation Algorithm is considered. In particular a detailed comparison with 5 year non aggregated data and an optimization analysis are performed in order to test and possibly enhance the original procedure. The proposal of enhancement is based on the introduction of an additional term, able to improve the accuracy of the aggregation method especially in case of non continuous building (and ground) heat load profiles, when the heat pump system is not operating for weeks or months.