PROLONGING THE RUNNING TIME OF A LARGE SCALE SOLAR THERMAL SYSTEM BY EMPLOYING A HEAT PUMP

摘要

In 2009 a solar thermal system with a gross collector area of 3885 m~2 was installed in Graz, Austria, on the one hand to supply heat to the district heating network of Graz, especially in summer, and on the other hand to partly cover the heat demand of on-site buildings. In the time period that is evaluated in this article (May 2010 to April 2011) the solar fraction for the building's heat supply was 28 %. In order to reduce the auxiliary heat needed for the on-site buildings and to prolong the running time of the solar thermal system, a 150 kW heat pump that uses the solar collector loop as heat source was installed. As a first step dynamic system simulations of the installation without the heat pump were performed in TRNSYS to validate the simulation model. The heat pump model was then implemented in the simulation to evaluate the effect of the heat pump installation on the whole system and to estimate its benefit.