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Abstract: One of the first passive energy standard office buildings in Europe was extensively monitored over 3 years to analyse the summer performance of highly insulated, well sun-shaded and mechanically ventilated buildings. During typical German summer conditions with less than 160 hours ambient air temperatures above 25 C, these buildings perform excellently during summer, even if the internal loads are rather high with 200–400 Wh m−2 day−1. If ambient air temperatures are significantly higher like in summer 2003 with more than 3 K higher average temperatures than usual, nearly 10% of all office hours are above 26 C. Detailed measurements showed that the night discharging of heavy thermal masses such as the concrete ceiling was not always effective under free convection conditions. Room air temperature decreased by 2–3 K only although measured night air changes were always above 5 h−1. The measured air change rates contained not only cool ambient air but also backflow of warmer air from the corridors, which could be shown by flow visualisation in the rooms and by simulation studies. Improvements to the night ventilation performance can be achieved, if early evening ventilation with high heat gains can be reduced and if fans support the air exchange in the cooler morning hours. Three year measurements and simulation of the earth heat exchanger showed that excellent performance is achieved with COP’s between 35 and 50. Due to the limited fresh air volume flow in such buildings, the earth heat exchanger only removes a fraction of the loads, here about 18% of the total internal loads. [Copyright &y& Elsevier]

Abstract: The paper presents a new desiccant cooling cycle to be integrated in residential mechanical ventilation systems. The process shifts the air treatment completely to the return air side, so that the supply air can be cooled by a heat exchanger. Purely sensible cooling is an essential requirement for residential buildings with no maintenance guarantee for supply air humidifiers. As the cooling power is generated on the exhaust air side, the dehumidification process needs to be highly efficient to provide low supply air temperatures. Solid rotating desiccant wheels have been experimentally compared with liquid sorption systems using contact matrix absorbers and cross flow heat exchangers. The best dehumidification performance at no temperature increase was obtained in an evaporatively cooled heat exchanger with sprayed lithium chloride solution. Up to 7gkg−1 dehumidification could be reached in an isothermal process, although the surface wetting of the first prototype was low. The process then provides inlet air conditions below 20°C for the summer design conditions of 32°C, 40% relative humidity. With air volume flow rates of 200m3 h−1 the system can provide 886W of cooling power. A theoretical model for both the contact absorber and the cross flow system has been developed and validated against experimental data for a wide range of operating conditions. A simulation study identified the optimisation potential of the system, if for example the surface wetting of the liquid desiccant can be improved. [Copyright &y& Elsevier]