Exergy analysis of a low temperature radiant heating system

Abstract

The purpose of this study is to gain insight into the process of heating a room with a low-temperature radiant heating system and solar energy, considering energy conversion and heat transfer steps in the building (where heat is required), in the incident solar radiation (which supplies part of the heat required) and in the heating system (which provides for the additional heating needs, by using electricity from a gas-fired power plant to drive a heat pump). We applied a theoretical framework developed by Shukuya et al., to a dynamic simulation model and did numerical calculations for a room with an exterior wall, with and without a south-facing window, during a heating season in the Netherlands. The exergy analysis allows direct comparison between different energy types (e.g., heat, electricity, fuel) on a common basis, and the concept of exergy consumption is useful for expressing how and where energy is dispersed in the course of energy conversion and heat transfer steps. The results show that exergy consumption in the room (demand side) is relatively small compared to the supply side (fuel burned at the power plant and the sun reaching the ground and facade). The calculations also show that the total amount of exergy consumed during the heating season can be larger than the total amount of exergy supplied during the same period, as a result of heat storage in the building mass, and of changes in the outdoor temperature between the moment of heat storage and heat release.