ISIE-ISSST 2017: Science in Support of Sustainable and

ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25th 29th June 2017 Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale Samuel Cooper, Jonathan Norman, Geoff Hammond University of Bath, Bath UK [email protected] EPRSC grant: EP/N022645/1 Data available at: https://doi.org/10.15125/BATH-00378 Exergy and Improvement Potential

Energy cant be destroyed but it can be degraded Exergy is a measure that takes this into account. It is the work that can theoretically be done by that energy. Improvement potential gives theoretical limit to improvement that could be achieved Application in analysis of energetic systems. Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25 th 29th June 2017

What about large scale? Two questions examined empirically: 1. Has the Improvement Potential of sectors been a good indicator of the efficiency improvement that actually then took place? 2. How sensitive are results to the selection of boundaries and definitions? Comparing exergy efficiency and exergy productivity. How can exergy be usefully applied, where might there be problems in over-relying on it? Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25 th 29th June 2017 Improvement Potential and actual improvement Compared exergy efficiency of industrial sectors in EU-15* to efficiency improvement that took place in following 15 years.

Was energy or exergy a better predictor? * Based on methodology in: A. C. Serrenho, T. Sousa, B. Warr, R. U. Ayres, and T. Domingos, Decomposition of useful work intensity: The EU (European Union)-15 countries from 1960 to 2009, Energy, vol. 76, pp. 704715, 2014. Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25 th 29th June 2017 Improvement Potential and actual improvement Varied results for both metrics variation between sectors and with time. Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25 th 29th June 2017 Comparing exergy efficiency and productivity

Sectoral output typically cant be defined objectively as energy (i.e. a product exergy content) Useful exergy is used as a proxy. E.g. high temperature heat supplied to a process or motive power supplied to car tyres. However, this is not entirely objective there is a balance between having a meaningful exergy content and this exergy being related to the desired output of the sector. Transport example:

> > > > To assess whether the points for measuring useful exergy are consistent, we would ideally compare to the minimum theoretical exergy content of the desired product / output but this isnt generally feasible so we compare exergy efficiency to exergy productivity.

Exergy efficiency = Useful exergy used by sector / Exergy inputs to sector Exergy productivity = Monetary value of sector outputs / Exergy inputs to sector Consistent ratio implies strong correlation between value and product exergy AND useful exergy well correlated with product exergy. Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25 th 29th June 2017 Comparing exergy efficiency and productivity

Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25 th 29th June 2017 Comparing exergy efficiency and productivity Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25 th 29th June 2017 Conclusions Exergy analysis can be useful at the macro scale

It should not be exclusively relied on. Energy analysis and other metrics specific to research questions are also relevant. There are many factors influencing improvement in energy and exergy efficiency. The exergetic (and energetic) improvement potential is one of these but other constraints and technological limits apply. System boundary issues still exist surrounding the measurement of useful exergy. Care must be taken so that focus on exergy does not underplay options such as resource efficiency or more intelligent use of energy. Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25 th 29th June 2017 ISIE-ISSST 2017: Science in Support of Sustainable and Resilient Communities, 25th 29th June 2017

Energy versus exergy: An empirical analysis of thermodynamic metrics at the macro scale Samuel Cooper, Jonathan Norman, Geoff Hammond University of Bath, Bath UK [email protected] EPRSC grant: EP/N022645/1 Data available at: https://doi.org/10.15125/BATH-00378

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