Garcia Kerdan, I; (2017) Optimisation of building energy retrofit strategies using dynamic exergy analysis and exergoeconomics. Doctoral thesis , UCL (University College London).

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Abstract

Existing buildings represent one of the most energy intensive sectors in today’s society, where comprehensive building energy retrofit (BER) strategies play a major role in achieving national reduction targets. Despite the efforts made in recent decades through policies and programmes to improve building energy efficiency, the building sector (which proportionally has the highest demand for heat) has the lowest thermodynamic efficiency among all UK economic sectors. As other sectors have shown, exergy and exergoeconomic analyses can be indispensable tools for the design and optimisation of energy systems. Therefore, there is a need for modification of existing BER methods in order to include thermodynamic analysis with the aim improve true efficiency of buildings and minimise its environmental impact. However, a paradigm shift represents a big challenge to common building practice as traditional methods have prioritised typical energy and economic objectives. The aim of this thesis is to develop a methodological framework for the evaluation of BER strategies under exergy analysis and exergoeconomic accounting supported with the integration of the calculation framework into a typical dynamic building simulation tool. There are two original contributions to the knowledge of this research. First, the techno-economic appraisal of BER strategies, based on the typical energy-efficient and cost-benefit method, is enhanced by adding a whole-building exergy analysis combined with an exergoeconomic method (SPECO). Second, ExRET-Opt, a retrofit-oriented simulation tool based on dynamic exergy calculations and exergoeconomic analysis combined with a comprehensive and robust retrofit database, is developed and implemented for this research. In addition, a multi-objective optimisation module based on genetic algorithms is included within the simulation framework in order to improve BER design under different thermodynamic and non-thermodynamic conflicting cost objective functions. Three UK non-domestic case studies implementing a wide range of active and passive retrofit strategies are presented. Results suggest that under identical economic and technical constraints, the inclusion of exergy/exergoeconomic indicators as objective functions into the optimisation procedure has resulted in buildings with similar energy and thermal comfort performance as traditional First Law methods; while providing solutions with better thermodynamic performance and less environmental impact. The approach also demonstrates to provide BER designs with an appropriate balance between active and passive measures, while consistently accounting of irreversibilities and its costs along every subsystem in the building energy system. The developed framework/tool seems like a promising approach to introduce the Second Law into typical building energy practice and for the development of policies, incentives, and taxes based on exergy destruction footprints. Such policies could help highly thermodynamically-efficient or low exergy BER designs to become widely available.

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