Thermoeconomics applied to building services.

Thermoeconomics is a blend of thermodynamics with economics. The thermodynamic analysis uses the second law and the concept of exergy, the measure of usefulness of energy. Economics involves costing exergy flows in life costing techniques. The objective of thermoeconomics is to minimise a cost function, talcing into account capital, maintenance and running costs. Most of these are expressed in terms of thermodynamic variables of the system. This will establish the most cost effective design parameters. This paper presents methods for applying a thermoeconomic analysis to a building services system, consisting of displacement ventilation air conditioning. The specific cost of indoor environment cooling is optimised in terms of system variables, such as water and air temperatures and mass flow rates. Firstly, certain system parameters are optimised, providing detailed exergy costing related to the plant capital and operating costs. Secondly, by analysing these, the most appropriate design modifications are implemented, and the system is again optimised. From the work presented, an improved thermal and economic design results, with a reduction in Life Cycle Cost of 21%.