Citation: Singla, M.K.; Gupta, J.; Nijhawan, P.; Oberoi, A.S.; Alsharif, M.H.; Jahid, A. Role of a Unitized Regenerative Fuel Cell in Remote Area Power Supply: A Review. Energies 2023, 16, 5761. https:// doi.org/10.3390/en16155761 Received: 9 June 2023 Revised: 21 July 2023 Accepted: 31 July 2023 Published: 2 August 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Review Role of a Unitized Regenerative Fuel Cell in Remote Area Power Supply: A Review Manish Kumar Singla 1 , Jyoti Gupta 2 , Parag Nijhawan 3 , Amandeep Singh Oberoi 4 , Mohammed H. Alsharif 5, * and Abu Jahid 6, * 1 Department of Interdisciplinary Courses in Engineering, Chitkara University Institute of Engineering & Technology, Chitkara University, Rajpura 140401, India 2 Department of Computer Science, Shree Guru Gobind Singh Tricentenary University, Gurugram 122505, India 3 Electrical and Instrumentation Engineering Department, Thapar Institue of Engineering and Technology, Patiala 147004, India 4 Mechanical Engineering Department, Thapar Institue of Engineering and Technology, Patiala 147004, India 5 Department of Electrical Engineering, College of Electronics and Information Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Republic of Korea 6 School of Electrical Engineering and Computer Science, University of Ottawa, 25 Templeton St., Ottawa, ON K1N 6N5, Canada * Correspondence: malsharif@sejong.ac.kr (M.H.A.); ajahi011@uottawa.ca (A.J.) Abstract: This manuscript presents a thorough review of unitized regenerative fuel cells (URFCs) and their importance in Remote Area Power Supply (RAPS). In RAPS systems that utilize solar and hydrogen power, which typically include photovoltaic modules, a proton exchange membrane (PEM) electrolyzer, hydrogen gas storage, and PEM fuel cells, the cost of these systems is currently higher compared to conventional RAPS systems that employ diesel generators or batteries. URFCs offer a potential solution to reduce the expenses of solar hydrogen renewable energy systems in RAPS by combining the functionalities of the electrolyzer and fuel cell into a single unit, thereby eliminating the need to purchase separate and costly electrolyzer and fuel cell units. URFCs are particularly well-suited for RAPS applications because the electrolyzer and fuel cell do not need to operate simultaneously. In electrolyzer mode, URFCs function similarly to stand-alone electrolyzers. However, in fuel cell mode, the performance of URFCs is inferior to that of stand-alone fuel cells. The presented review summarizes the past, present, and future of URFCs with details on the operating modes of URFCs, limitations and technical challenges, and applications. Solar hydrogen renewable energy applications in RAPS and challenges facing solar hydrogen renewable energy in the RAPS is discussed in detail. Keywords: fuel cells; hydrogen energy; URFC; remote area power supply; hybrid systems 1. Introduction A significant portion of the world’s energy is reliant on unexplored fossil fuel reserves. The continued growth of the world population and economy drives the extensive usage of fossil fuels [1,2]. Global oil production is predicted to peak in 2021 and be depleted within 15 years, according to the US Department of Energy. Some claim that peak oil output has already occurred [3]. Oil prices are under tremendous pressure as demand for oil continues to rise while supply stays stable. However, within the scientific community, there is a consensus that the escalating levels of greenhouse gases and resulting climate change are directly linked to human activities, which have caused global warming. The burning of fossil fuels is a primary contributor to these activities and leads to increased greenhouse gas emissions. Therefore, it is of utmost importance to shift towards alternative energy sources and move away from fossil fuels in the coming decades. The adoption of renewable energy sources like solar and wind power plays a crucial role in establishing a sustainable energy strategy and facilitating the shift away from Energies 2023, 16, 5761. https://doi.org/10.3390/en16155761 https://www.mdpi.com/journal/energies