Energy piles are an efficient renewable energy source. The advantage of these heat capacity systems is the use of already necessary infrastructure for structural support to extract heat from the ground. In this project a numerical finite element model of two interacting energy piles in COMSOL Multiphysics® is used to evaluate the influence of different parameter variations on the system performance. The evaluation is based on the temperature profile of the soil after a certain heating period. The parametric analysis has shown that the pipe configuration, as well as the spacing have the greatest impact on the thermal interaction between the piles. The flowrate of the fluid in the pipes, the heat pump power and the variation of the pile diameter only have a smaller influence on the thermal interaction. In a further part of the project, the environmental impact of refrigerants is evaluated, with focus on replacement of conventional refrigerants with more environmental friendly refrigerants. Based on the evaluation of the parametric analysis and the evaluation of the environmental impact of the refrigerants, general guidelines are formulated.