Improving the robustness of exergy accounting: from primary energy to energy services
Authors: Tânia Sousa, Jonathan Cullen, André Cabrera Serrenho, Paul Brockway, Tiago Domingos
Abstract: Reducing demand for energy remains a large-scale and cost-effective means to reduce carbon emissions and mitigate climate change. Yet, estimating the potential for reducing societal energy demand has proved challenging because current methods do not use consistent definitions of efficiencies and often fail to consider maximum efficiency limits. This paper sets out to improve the robustness of societal exergy accounting and explore practical efficiency limits across the energy supply chain. The first section examines the methodological issues regarding the consistent definition of efficiencies in performing exergy analysis from primary exergy to final exergy and final exergy to useful work (e.g. heat, motion, light). It also discusses the metrics that can be developed to effectively measure the conversion of useful work to energy services (transport, thermal comfort). The second section of the paper discusses the definition and implications of practical efficiency limits for conversion devices and passive systems on exergy analysis.
Measuring EROI (energy return on investment) on a national level – links to exergy and useful work analysis?
Authors: Tim Foxon, Lina Brand, Paul Brockway, Claire Carter, Charles Hall, Jessica Lambert, Peter Taylor
Abstract: Concerns have been raised that declining EROI (energy return on energy investment) from fossil fuel and alternative energy inputs could constrain the ability of economies to continue to deliver economic growth and improvements in social wellbeing. This paper contributes to understanding of physical constraints on economic growth by relating EROI analysis to exergy-based analysis of economic growth, by addressing: (1) What are the remaining conceptual and methodological issues relating to defining EROI (or related measures of net energy) for a national economy? (2) How can we synthesise aggregated and individual process based energy estimates? (3) How would this new measure of EROI relate to analyses of efficiency of conversion of exergy inputs to useful work? (4) What further data collection would be needed to measure EROI at a national levels? (5) How would this measure of EROI relate to analyses of efficiency of conversion of exergy inputs to useful work?
Investigating the Coupling Between Useful Exergy and GDP
Authors: Tiago Domingos, André Cabrera Serrenho, Tânia Sousa, Paul Brockway, Benjamin Warr
Abstract: The last decade has seen increasing interest in relating energy and the economy considering the useful exergy (useful work) metric. Here, we classify energy uses according to the three stages of the economic process in which energy is used: (1) production of capital goods; (2) production of other goods; (3) direct energy use by final consumers. High temperature heat uses are mostly associated to (1). The uses in (3) are not directly associated to the creation of economic value and vary significantly with income for the same country and with climate between different countries. We hypothesize that, if we remove the effects of (1) and (3), useful exergy intensity is roughly constant and equal between countries. We discuss the empirical basis for this result, analyse the implications regarding trends in primary energy and final energy intensities, and outline a research plan for further testing, analysis and interpretation of this hypothesis.
Modelling Economic Growth with Exergy-augmented Production Functions
Authors: Tiago Domingos, João Santos, Paul Brockway, Matthew Heun, Julia Steinberger, Marco Sakai
Abstract: We review and discuss the inclusion of energy inputs in a macroeconomic production function framework, in order to fit past economic growth for several countries. We argue that an energy-augmented production function is better capable of tracing production relations over time. It will follow that energy is more important than indicated by its cost-share. Assumptions regarding factors of production, choice of production function and the appropriate measure for energy (exergy) inputs are carefully addressed. Using OLS regressions and resampling techniques (bootstrapping), we empirically test possible exergy-augmented production functions (Cobb-Douglas, Constant Elasticity of Substitution, Linear Exponential) in terms of goodness-of-fit to economic growth, total factor productivity (TFP), factor substitution and output elasticities. We compare results obtained considering measures of energy inputs at distinct stages of exergy flows (primary, final and useful). All exergy-augmented production functions are also compared against analogously fitted functions considering only capital and labor inputs.