A symbolic exergoeconomic study of a retrofitted heating and DHW facility

Thermoeconomic analysis of building energy supply systems are usually performed following the input-output approach, where the supply chain is divided into several subsystems directly related to each other. However, in this paper Symbolic Thermoeconomics has been applied and a dynamic analysis and comparison has been performed between the old and the retrofitted heating and DHW facility of four dwelling blocks located in Bilbao. Having obtained the heating and DHW demands, the corresponding exergy demands were calculated, both by the simplified and detailed method. Once the productive structure is defined, Symbolic Thermoeconomics is applied. The exergy analysis shows the improvement achieved with retrofitting, going from a 2.55% yearly average exergy efficiency of the old facility to a 4.01% value for the retrofitted. Then, exergy costs and exergoeconomic costs of the products of each component, particularly the costs of the final products, heating and DHW, are expressed as the amount of external resources required for obtaining them, either in energy or monetary units. As a result, those costs not including the investment costs, are reduced 32.71% for heating and 48.5% for DHW. Applying a general and rigorous mathematical approach, the thermodynamic nature of costs and their formation process are analysed.