Extracting and utilising heat from an hydrogen production plant

Abstract

In order to reach the climate goals the use of fossil fuels needs to decrease and green solution need to provide the energy of the future. Wind and solar will probably supply a large fraction of our electrical power need in the future. Because of the nature of these sources the demand for electrical power will not always be balanced with the supply. Industrial companies are responsible for a large portion of the total greenhouse emissions. Some of the emissions are process related, but most are due to the demand for high temperatures in the process. Today fossil fuels like coal and gas are used to achieve these high temperatures. Hydrogen provides a solution for the problems as it can be used as a storage medium and as an energy source to achieve high temperatures. In order to provide the world with sufficient hydrogen needed for the transformation to greener solu­ tions the production of hydrogen needs to increase. Hydrogen can be made from fossil fuels, but to achieve our goals the production of green hydrogen is needed. Green hydrogen is made using green electricity and the electrolysis process. In this thesis the alkaline electrolysis process is reviewed. During the production of hydrogen using the alkaline electrolysis process, a large fraction of the electri­ cal energy is converted to thermal energy. The aim of this research is to gain insight into the possibility of extracting the thermal energy form the process so it can be used in a district heating network. Based on the thermal demand form the heating district and the power supply to the hydrogen plant four case studies are evaluated. Using a pinch analysis, a process flow diagram is designed for each case study after which every design is modelled. Using a heat pump and thermal storage the supply of thermal energy and the demand from the district heating network are balanced in order to reach a high overall efficiency.