New test methodologies to analyse direct expansion solar assisted heat pumps for domestic hot water

Abstract

Since there are not specific standards for testing direct expansion solar assisted heat pumps for domestic hot water, new testing methodologies are proposed supported by laboratory experiments. Two methodologies were developed for performance measurement: modified BIN method and long term performance prediction with a TRNSYS model validated with specific experimental conditions. The long term performance prediction is a methodology similar to the already obtained for solar thermal systems. A system was tested in Lisbon during one year, covering almost all possible local weather conditions. The hot water tapping test cycle used was in agreement with recent standards EN16147:2011 or EN15316-3-1:2007. The influence of average daily air temperature, dew point temperature and solar irradiation was analysed. The seasonal performance factor was calculated for two cities in Portugal (Lisbon and Porto) and for additional four cities in Europe (Davos, Athens, Helsinki and Strasburg). The establishment of a procedure to calculate the seasonal performance of this kind of systems is very important according to the directive 2009/28/EC of the European Parliament and of the Council.