Utilisation of Heat Released During the Production of Green Hydrogen Using Alkaline Electrolysis

Abstract

To reduce greenhouse gas emissions and to limit global warming, fossil fuel based energy technologies need to be replaced by clean energy technologies. Renewable energy sources are dependent on weather conditions therefore security of energy supply is not ensured and the need for energy storage is growing. Hydrogen is considered a clean energy carrier that can be used for energy storage. Water electrolysis that uses renewable energy is a sustainable method for the production of green hydrogen. Water electrolysis is a process by which water is split into hydrogen and oxygen by using direct current to drive the reaction. During the production of green hydrogen heat is released to the environment. Little research has been conducted on the amount of heat released during green hydrogen production and on the temperature of the released heat. It is unclear if the released heat could be used.
This research serves to answer the question "Is it possible to use the heat released during the production of green hydrogen using alkaline water electrolysis?". To answer this question a model has been developed in ASPEN Plus. This model represents an alkaline electrolyser, consisting of an electrochemical model, a thermal model and a cooling system. To validate the output of the model, the hydrogen production output has been compared with an alkaline electrolyser developed by the company Nel hydrogen. The thermal efficiency of the model has been calculated with and without using the waste heat. To use the waste heat the system first needs to be cooled. To determine which heat exchanger is best to use for recovering the heat of the alkaline electrolyser, three different designs have been implemented in the ASPEN model. The designs have been analyzed and the best option is implemented in the model. The amount of heat that can be recovered has been investigated as well as the options for the use of the recovered heat. The results are discussed and recommendations are made for follow-up research.