Paper Conference

Proceedings of BSA Conference 2015: Second Conference of IBPSA-Italy


Comparison between hourly simulation and bin-method for the seasonal performance evaluation of electric air-source heat pumps for heating

Claudia Naldi, Matteo Dongellini, Gian Luca Morini, Enzo Zanchini

Abstract: Air-source heat pumps in heating mode are characterized by performances strongly dependent on the value of the outdoor air temperature. The Italian standard UNI/TS 11300-4 indicates, for the evaluation of a heat pump seasonal efficiency, a method based on the local bin distribution of the external air temperature. The aim of this paper is to test the bin-method proposed by UNI/TS 11300-4 by comparing the results obtained through this method with the results deducted by using a more accurate dynamic simulation of the system. The heat pump Seasonal Coefficient Of Performance (SCOP) is calculated by means of a dynamic simulation code, written in MATLAB, in which hourly climate data distributions defined by CTI for different Italian towns are introduced as input data together with the thermal characteristics of the building. The thermal winter behaviour of the building is introduced in the models by using the Building Energy Signature. In the paper the values of the seasonal indexes SCOPon and SCOPnet obtained by means of the bin-method and the dynamic hourly simulation, both for mono-compressor and inverter-driven heat pumps, in the service of several buildings placed in different Italian climates, are evaluated and compared to each other. Different buildings and different climate data are used in order to highlight the main conditions which are responsible for the difference between the predictions obtained with the bin-method and the results obtained by using the dynamic hourly simulation. The results presented in this paper show that the predictions of the bin-method tend to be in agreement with the results of the dynamic simulations based on the Test Reference Year only in particular conditions. The observed discrepancies in terms of SCOP between these two approaches can reach 23%, varying with the climate data and with the type of heat pump considered.
Pages: 255 - 262