Opportunities of waste heat recovery from various sources: Review of technologies and implementation

Waste heat recovery (WHR) using conventional technologies can provide appreciable amounts of useful energy from waste heat (WH) sources, thus reducing the overall energy consumption of systems for economic purposes, as well as ameliorating the impact of fossil fuel-based CO₂ emissions on the environment. In the literature survey, WHR technologies and techniques, classifications and applications are considered and adequately discussed. The barriers affecting the development and utilization of systems of WHR, as well as possible solutions are presented. Available techniques of WHR are also discussed extensively, with a particular interest in their progressive improvements, prospects, and challenges. The economic viability of various WHR techniques is also taken into account considering their payback period (PBP), especially in the food industry. A novel research area wherein the recovered WH of flue gases from heavy-duty electric generators was utilized for agro-products drying has been identified, which may be useful in the agro-food processing industries. Furthermore, an in-depth discussion on the appropriateness and applicability of WHR technology in the maritime sector is given a prominent touch. In many review works involving WHR, different areas such as WHR sources, methods, technologies, or applications were discussed, albeit not in a comprehensive way touching on all-important aspects of this branch of knowledge. However, in this paper, a more holistic approach is followed. Furthermore, many recently published articles in different areas of WHR have been carefully examined and the recent findings provided are presented in this work. The recovery of waste energy and its utilization is capable of significantly dropping the level of production costs in the industrial sector and harmful emissions to the environment. Some of the benefits derivable from the application of WHR in the industries may include a reduction in energy, capital, and operating costs, which translate to reduced cost of finished products, and the mitigation of environmental degradation through the reduction of the emission of air pollutants and greenhouse gases. Future perspectives on the development and implementation of WHR technologies are presented in the conclusions section.