Research

Integration and optimization of a reversed Brayton cycle coupled with renewables and thermal storage in an oil refinery

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Abstract

As greenhouse gas emissions from fossil fuel combustion are one of the main factors for global warming, the EU has imposed policies and regulations on climate and energy [1]. In the 2030's climate and energy framework, the goal is set to 40% reduction in greenhouse gas emissions from the level of those in 1990 [2]. Denmark has even more ambitious targets. The Energy Strategy of 2050 aims at Denmark being completely independent from fossil fuels [3]. For that reason, continuous research is ongoing for the removal and replacement of fossil fuels. The share of renewable energy technologies in the energy mix has increased over the past years, mainly in electricity production. Society is gradually moving towards a future with electrified systems based on renewable sources. Concerning heat production, heat pumps are a highly attractive for electrification, which could substitute fossil fuels based boilers and furnaces. On an industrial level, there is a large demand in heat in high temperatures over 100 °C, which designates the potential of integration of High- Temperature Heat Pumps (HTHPs) [4]. Because of high temperature lifts accompanied with high temperature applications, the energetic performance of heat pumps deteriorates. Therefore, HTHPs could be considered in combination with large shares of renewable electricity sources. The renewables enable low levelized cost of electricity, which would improve the economic feasibility of the heat pump system. In this study, the potential of a HTHP project is evaluated from a technoeconomic perspective when coupled with renewable electricity sources and thermal storage. Through optimization, the capacities of the considered technologies are determined, and the project is compared with conventional combustion technologies and electric boilers [5]. The concept is applied to the case study of an oil refinery and conclusions were extracted for such an industry.