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Abstract: Energy efficient HVAC solutions may be obtained by combining different energy sources – fossil and renewable – into single hybrid systems. This leads to a variety of system concepts with specific boundary conditions. As a consequence, the definition of a unique representation method and a standardized performance evaluation procedure is a challenging task. Currently, two international projects promoted by the IEA are dealing with the representation and the performance calculation of a particular category of hybrid systems, i.e. integrated solar assisted systems. The HPP Annex 34 “Thermally Driven Heat Pumps for Heating and Cooling”, whose goal is to reduce the environmental impact of heating and cooling by the use of thermally driven heat pumps, has solar cooling as one of the systems under investigation. The joint project between SHC and HPP Task 44/Annex 38 “Solar and Heat Pump Systems” is focused on different system combinations of solar thermal collectors and heat pumps. The scope of the present paper is to show a systematic methodology to represent and evaluate the energy performance of complex hybrid systems. The proposed approach is a joint effort of the on-going IEA activities and will be discussed regarding the mentioned solar hybrid systems. However, the final goal of the work is to provide a basis for a simple, fair and transparent comparison of all systems for heating and cooling, regardless of the technology. [Copyright &y& Elsevier]

Abstract: Ground-source heat pump (GSHP) is a renewable energy technology with the advantages of energy saving and environmental friendliness. This paper focuses on the energy efficiency of air-conditioning systems in public buildings in Tianjin. Three public buildings are chosen as case studies with different forms of cold & heat sources. A building with ground-source heat pump for heating and cooling, a building with electricity-driven refrigerating unit for cooling and centralized heat-supply network for heating, a building with direct-fired Li-Br absorption refrigerating and heating unit for heating and cooling are selected. Attempt is made to analyze the actual operating performance of air-conditioning system and evaluate the system energy efficiency in different buildings. The results show that ground-source heat pump air-conditioning system without adequate design and management is not always better than other traditional air-conditioning systems. [Copyright &y& Elsevier]