Designing a solar PV module for powering an electrolyzer

Abstract

The rapid depletion of fossil fuels, rise in the cost and demand for energy, greenhouse gas emissions, and global warming have collectively led to the requirement of generating clean energy through renewable energy sources. Among all renewable resources, solar energy proves to be of the highest potential owing to its abundant and inexhaustible nature. Solar power capacity in India has increased from 6.7 GW to 40 GW as of March 2021. The use of solar energy can partially address the issue. The reduction of greenhouse emissions is a major concern and can be addressed only by finding an alternative to fossil fuels. One possible alternative is hydrogen which turns out to be a green and clean energy carrier if produced via electrolysis. Further, the electrolyzer should be integrated with a solar photovoltaic system to make it fully sustainable [1].

Solar energy is ubiquitous, making it a viable contender for coupling with electrolyzers. Solar PV systems can be combined with a dual-functional electrolyzer, producing hydrogen by electrolysis and removing the waste heat by active cooling. When compared to a stand-alone electrolyzer at an ambient temperature, it is seen that this system has an energy efficiency of 56-59%, and integrating the electrolyzer to the PV module results in the increase of hydrogen production by almost 2.5 folds. Hence, to enhance the application of solar PV technologies, coupling with electrolyzers proves to be a significant approach. Solar PV arrays can be directly coupled with PEM electrolyzers to improve the system efficiency as shown in fig. 1A. Power transfer efficiency close to 99% can be achieved by connecting electrolyzer cells in series or parallel and by matching the PV systems’ curve connecting MPPs and different irradiation levels to the electrolyzer polarization curve [3]. A PV-Electrolysis system with an InGaP/GaAs/GaInNAsSb triple-junctional solar cell with two PEM electrolyzers in series, achieving a 48-h solar-to-hydrogen (STH) efficiency of 30%, is depicted in fig. 1B [4]. 

A challenge in coupling a solar PV system with an electrolyzer is that there can be a mismatch between the Maximum Power Point of the solar cell and I-V characteristics of the electrolyzer due to variation in solar irradiation during the day, to resolve which a DC/DC regulator can be added. The PV-Electrolyzer Systems’ I-V Characteristics have to be accurately predicted for constructing and optimizing the system. Moreover, the solar resource is intermittent, available only during the day, and subject to fluctuations. Hence there is a requirement for a storage system, which, however, adds to the life cycle cost of the system. Overcoming these challenges can lead to the successful integration of solar PV systems with electrolyzers, thereby enhancing the production of Green Hydrogen, a recent ally to a carbon-neutral future.