Sankey
An exergy sankey diagram showing the conversion of raw materials to final products

Chemical Exergy Calculator

Exergy as An Efficiency Metric

The use of energy and materials in modern society is associated with greenhouse gas (GHG) emissions that exacerbate climate change. To reduce emissions, a combined energy and material efficiency approach is needed. Using exergy as a metric for quantifying energy and materials, we can discover the true thermodynamic value of these resources. Exergy acts as a measure for both a resource’s quantity and quality, reflecting how pure, hot or pressurised a resource is.

Chemical Exergy

While the exergy value of a material depends on several factors including chemical composition, temperature, pressure, height and others, this calculator focuses on building a tool to procure values for the chemical exergy of a material. This is the exergy component that is dependent on the chemical composition and purity of the material and reflects its usefulness either as a raw material, or as a potential source of energy through mechanisms like combustion and pyrolysis. Correlations for estimating other exergy components from physical properties are readily available in literature. However, chemical exergy methods are more complex and fractured: several different correlations have been developed for different types of materials and they are not collected together for ease of reference. While other exergy components have established literature and correlations for estimating them from other physical properties are easily available and relatively simple, chemical exergy calculations are more complex: there are several tabulated values for different materials, calculation methods depend on the type of material and different correlations exist for the same type.

The Calculator

This calculator aims to combine all this literature and disparate correlations into a single tool where a user can search for their desired material and return a material exergy value. The tool provides a list of potential materials from which the user can pick.. The results for all materials include different correlation methods and are neatly summarised in minimum, average and maximum values to give the user an idea about the spread of the chemical exergy value.

Instructions

You need to register an account with the calculator host website to be able to access it. In accordance with GDPR regulations we will not use your email address for any commercial or other purposes and not pass it on to any other organisation. We will only your email address for (very) infrequent emails about updates to the calculator. Upon registration you’ll receive a confirmation email with a login link which you’ll use to access the calculator. The landing page shows a list of material types. You can find your desired material through the filter function at the top (e.g. ‘Wood’ or ‘Steel’). The calculator returns the result(s) with a spread of exergy values for this material type. For more accuracy you can click on the result and sub-categories of the material and their exergy range will appear (e.g. ‘Pine bark’, ‘Bamboo’). Clicking on these sub-categories will give the chemical exergy results returned by different methods applicable to this material as well as additional information for the material such as the proximate and ultimate analysis or its composition, along with the reference used for this particular material exergy calculation. The exergy values are given in kJ/kg.

Citation

The theoretical foundation on which this calculator rests is outlined in a paper submitted to the Journal of Industrial Ecology under the title of ‘Calculating the Chemical Exergy of Materials’ by Michalakakis, Fouillou, Lupton, Gonzalez Hernandez and Cullen (2020) (under review). Please cite this paper when using this calculator, and include the license details below:

CC BY-NC-ND License

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Related papers

The following journal papers use the calculator or earlier versions of the database:
  • Gonzalez Hernandez, A., Lupton, R., Williams, C., & Cullen, J. (2018). Control data, Sankey diagrams, and exergy: Assessing the resource efficiency of industrial plants. Applied Energy, 218 232-245
  • Michalakakis, C., Cullen, J., Gonzalez Hernandez, A., Hallmark, B. (2019). Exergy and network analysis of chemical sites. Sustainable Production and Consumption. 270-288