How pinch analysis techniques can be used to optimise decarbonisation techniques
CLIMATE change has emerged as a major environmental issue for the international community. According to a recent report by the Intergovernmental Panel on Climate Change1, net global emissions of CO2 and other greenhouse gases (GHGs) need to be cut to zero by mid-century in order to safely stabilise global warming to about 1.5˚C by 2100. Such reductions can only be achieved by large-scale deployment of decarbonisation techniques, including supply- and demand-side energy efficiency enhancement, fuel switching, increased use of renewables and nuclear energy, and commercialisation of carbon capture, storage and utilisation (CCUS) technologies. Given the potentially difficult choices that need to be made in large-scale decarbonisation programmes, policy makers can benefit from techniques to estimate, visualise and communicate how deep GHG emissions cuts can be achieved.
Within the chemical engineering community, we now have some established tools that can be used for planning the above decarbonisation techniques. This includes the various forms of process integration techniques (including pinch analysis and mathematical optimisation), which were originally developed in the 1970s for minimising energy requirements in industrial plants. The methodology has since been extended to address various problems involving minimisation of resource use and waste generation. One of the more recently-developed branches of process integration is carbon emission pinch analysis (CEPA), which determines optimal allocation of energy in carbon-constrained systems. This article looks at some of the established CEPA techniques.
The original CEPA methodology is based on a graphical pinch analysis technique known as the energy planning pinch diagram (EPPD), which the authors originally proposed for high-level planning of carbon-constrained energy systems.2 The method has since been widely used by researchers to analyse problems in six different continents.3
CEPA methodology deals with the two-fold problem of determining the minimum amount of zero- or low-carbon energy source needed to meet the energy requirements and emissions constraints of a system; and determining the allocation of energy sources in order to satisfy both energy requirements and carbon constraints within the system. Here we assume the methodology applies only to electricity, so that other than the carbon footprint factors, different power sources are practically interchangeable with each other. The main steps of the procedure are:
Other than the graphical approach described here, CEPA can also be implemented algebraically with the aid of spreadsheets or using automated targeting models (ATM) in optimisation software. The alternative approaches are mathematically equivalent, but carry advantages and disadvantages. Further details of CEPA methodology are described fully, along with sample applications in different countries, in a forthcoming book.3
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