HVAC systems are the most energy consuming devices among building components. Therefore, to achieve the global aims in energy reduction, the efficiency of HVAC systems has to improve significantly. Thermally driven air conditioning systems are a possible way to reduce the dependency on traditional vapor compression cycles and to lower the primary energy consumption. Due to the separation of dehumidification and cooling, natural heat sources, e.g. solar thermal energy, and natural heat sinks, e.g. shallow geothermal energy, can be used or, when combined with a traditional vapor compression cycle, the temperature level of the heat sink can be increased. With the separation of cooling and ventilation the overall efficiency can be increased even more. This paper introduces a pilot installation of a solar thermal and geothermal assisted air conditioning system located in Hamburg, Germany. The combination of a desiccant assisted air conditioning system with radiant heat exchanger enables a highly efficient HVAC system. Due to the strong influence of outdoor air conditions, a system model is built to evaluate the performance of this system at different climate conditions worldwide. This paper presents an energy and economic evaluation of a highly efficient HVAC system at different geographical locations. (C) 2013 Elsevier Ltd. All rights reserved.