• Energy Research

Abstract The mission of Renewable and Sustainable Energy Reviews (RSER) is to communicate the most significant and relevant critical thinking in renewable and sustainable energy research and development, bringing together the research community, the private sector and policy and decision-makers. The aim of the journal is to share problems, solutions, novel ideas and technologies that support the transition to a low-carbon future and achieve the global emissions targets as established by the United Nations Framework Convention on Climate Change (UNFCC). The Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES) 2018 conference brought together the following topics through interdisciplinary dialogue: (a) Process Integration for sustainable development; (b) Process analysis, modelling and optimisation; (c) Total Site Integration; (d) Heat transfer and heat exchangers; (e) Energy-saving and clean technologies; (f) Sustainable processing and production; (g) Renewable and high efficiency utility systems; (h) Footprint minimisation and mitigation; (i) Operations and supply chain management; (j) Waste minimisation, processing and management; (k) Batch process analysis and integration; (l) Process network dynamics, flexibility and control; (m) Industrial implementation and optimisation; (n) Numerical fluid flow and heat transfer simulation; (o) Sustainability and Process Integration teaching, learning and knowledge tools. This Virtual Special Issue (VSI) captures many of the most significant developments in renewable and sustainable energy research.

Integrated and combined cycles (ICC, CC) traditionally involve gas and steam turbines only. The paper analyses the further integration of high-temperature fuel cells (FC) having high electrical efficiency reaching up to 60% compared with 30–35% for most gas turbines. The previous research on FC hybrids indicates achieving high efficiencies and economic viability is possible. The ICC of various FC types—their performance and the potential for utilisation of renewables—are analysed considering also power generation capacity and site heat integration context. Further research and development with industrial relevance are outlined focusing on CO2 emissions reduction.

Fossil energy carriers cannot be totally replaced, especially if nuclear power stations are stopped and renewable energy is not available. To fulfill emission regulations, however, points such as emission sources should be addressed. Besides desulfurization, carbon capture and utilization have become increasingly important engineering activities. Oxyfuel technologies offer new options to reduce greenhouse gas emissions; however, the use of clean oxygen instead of air can be dangerous in the case of certain existing technologies. To replace the inert effect of nitrogen, carbon dioxide is mixed with oxygen gas in the case of such air combustion processes. In this work, the features of carbon capture in five different flue gases of air combustion and such oxyfuel combustion where additional carbon dioxide is mixed with clean oxygen are studied and compared. The five different flue gases originate from the gas-fired power plant, coal-fired power plant, coal-fired combined heat and power plant, the aluminum production industry, and the cement manufacturing industry. Monoethanolamine, which is an industrially preferred solvent for carbon dioxide capture from gas streams at low pressures, is selected as an absorbent, and the same amount of carbon dioxide is captured; that is, always that amount of carbon dioxide is captured, which is the result of the fossil combustion process. ASPEN Plus is used for mathematical modeling. The results show that the oxyfuel combustion cases need significantly less energy, especially at high carbon dioxide removal rates, e.g., higher than 90%, than that of the air combustion cases. The savings can even be as high as 84%. Moreover, 100% carbon capture was also be completed. This finding can be due to the fact that in the oxyfuel combustion cases, the carbon dioxide concentration is much higher than that of the air combustion cases because of the inert carbon dioxide and that higher carbon dioxide concentration results in a higher driving force for the mass transfer. The oxyfuel combustion processes also show another advantage over the air combustion processes since no nitrogen oxides are produced in the combustion process.

The feasibility and consequences of replacing nuclear power plants (NPP) in the Czech Republic with other energy sources are discussed. The NPP produced about one-third of electricity in the Czech Republic in 2017. Renewable energy sources such as hydropower, wind and solar power plants and biomass/biogas burning power plants produced about 11% of electricity in 2017. Due to the geographical and other constraints (intermittency, land footprint, and public acceptance), the renewables do not have the potential to entirely replace the capacity of the NPP. The only feasible technologies that could replace NPP in the Czech Republic in the near future are the power plants using fossil fuels. The combined cycle power plants running on natural gas (NGCC) are technically and environmentally fea-sible alternative for NPP at the moment. However, the natural gas imports would increase by two-thirds and the total greenhouse gas emissions would go up by about 10% if the power production of the NPP was entirely replaced by NGCC in the Czech Republic.

Abstract This special issue of Applied Energy contains articles developed from initial ideas related to the 17th Conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES 2014) held in Prague, Czech Republic, during 23–27 August 2014. The conference has been organised jointly with CHISA 2014. Both events have benefitted from the shared pool of participants as well as the expanded opportunities for exchanging ideas. From all contributions presented at the conference, high-quality ones suitable for Applied Energy, have been invited. Overall, 37 extended manuscripts have been invited as candidate articles. Of those, after a thorough review procedure, 11 articles have been selected to be published. The topics attained in the focus of this Special Issue include Process Integration and Energy Management, CO2 capture, and Green Energy Applications.

Abstract A problem when exploiting renewable energy sources, such as wind and solar radiation, is their fluctuating availability. In the presented work, the Heat Integration methodology for batch processes based on Time Slices has been extended to cover the integration of solar thermal energy, thus allowing for dealing with such variations. A procedure for identifying the number and durations of Time Slices for a problem featuring variable renewable energy supply has been formulated, and developed for solar energy utilisation. The main procedural steps involve partitioning of the measured/forecasted heat availability profile using a large number of candidate time boundaries, and then approximating it by a piecewise-constant profile using high-precision. The approximation profile is obtained by subjecting the candidate superset of time-boundaries to MILP optimisation, thus minimising integral inaccuracy compared to the forecasted availability profile. The Time Slice definitions are completed by approximating the heat loads within the Time Slices. The integration of solar thermal energy can be performed for the specified Time Slice, after the optimal number of Time Slices with approximated constant load has been selected. Using heat storage, the heat can be transferred between Time Slices.

Abstract Researchers and industrial engineers dealing with energy supply and processes, using energy and other resources, have been largely working on devising concepts and methods for improvement of the efficiency at all stages of energy sourcing, conversion and use. An intrinsic part of this effort is also the minimisation of Greenhouse Gas (GHG) emissions. The 19th Conference on Process Integration for Energy Saving and Pollution Reduction – PRES 2016, held in Prague 27–31 August 2016, followed by the selection and evolution of 16 high-quality manuscripts in the current Virtual Special Issue (VSI) of Applied Thermal Engineering, have been fully dedicated to advancing science regarding these issues. This article analyses the overall challenges, and research trends in energy saving and pollution reduction, showing how the papers in the current VSI, while fitting in seamlessly within the overall trends, substantially contribute to the state of the art, considering heat transfer, heat recovery networks, gas turbines, GHG emission minimisation, not the least applying innovative network targeting and design techniques for CO2 utilisation after capture, which provides much more stable storage compared to sequestration.

This Special Section provides introduction to the 15th Conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES 2012). In this editorial introduction, the editors are highlighting the individual articles included in this issue and discussing the main points. The main areas of this issue can be summarised as: Process Integration for Energy Saving, Integrating Renewable Energy Sources and Energy Optimisation issues.