Parametric study and simulation-based exergy optimization for energy retrofits in buildings

The undertaking of building energy retrofits is essential for the reduction of energy use and carbon emissions at a national level. Nowadays, a number of construction methods and energy technologies that are available to practitioners require that the appropriate retrofit solution is identified to ensure long-term project success. A significant limitation of conventional methods that may be used to examine this (e.g. scenario by scenario) is that only a limited number of design scenarios can be evaluated which limits the potential for identifying the “best” designs. Furthermore, while the building sector has a large thermodynamic potential where most of the buildings' energy demands (especially space conditioning) can be met by low-grade sources, the associated exergy analysis method is rarely used in architectural practice. The following paper presents a simulation-based exergy optimization model, which aims to assess the impact of a diverse range of retrofit measures. Two non-domestic UK archetype case studies (a typical office and a primary school) are used to test the feasibility of the proposed framework. The objective optimization functions in this study are building energy use, exergy destructions throughout the building energy supply chain, and improvement of occupants’ thermal comfort levels. Different measures combinations based on retrofitting the insulation levels of the envelope and the application of different HVAC systems configurations (VAV, VRF, ground-source heat pump, air-source heat pump, district heating/cooling systems) are assessed. A large range of optimal solutions were achieved highlighting the framework capabilities. This approach can be extended by using the outputs in cost-benefit analysis and in thermoeconomic optimization.