Investigation of the cumulative impact of alkaline electrolysers on electrical power systems

Hydrogen could be the best candidate fuel for our future, especially in the transportation sector. It could be generated using water electrolysers running with power from carbon-free, renewable resources, since this is zero emission at the point of use, and so can help transition from the energy infrastructure available today into an energy world with a growing renewable electricity supply.This work models a highly distributed electrolyser system e.g. an urban hydrogen filling station network, and explores the Demand Side Management (DSM) potential of these electrolysers to improve the performance of the power system operating under the impact of intermittent renewable power generation.A comprehensive literature review has been carried out on the hydrogen economy, electrolysers and the potential role of storage devices in power systems. Three main areas related to alkaline electrolysers working within power systems were identified for further exploration. - Potential role of electrolysers in the existing distribution networks to increase the integrated wind power capacity - Potential role of electrolysers to stabilise the frequency of the power system - Potential role of electrolysers to absorb any surplus, carbon free, generation within the UK electricity networkThe first item of archival value within this work is the identification, presentation and discussion of electrolyser characteristics which are relevant to the introduction of an acceptable control strategy to integrate such electrolyser loads within the power system and thus provide improved performance of the network when exposed to the highly time variable energy supply from renewable sources. Two types of electrolyser made by NEL Hydrogen are detailed: atmospheric and pressurised. Their characteristics are reported in this thesis using the results from experiments designed by the author. In addition, an experiment has also been carried out on a PEM electrolyser available at Strathclyde University to compare its results with the characteristics of the commercial alkaline units. Second, a novel algorithm for sizing, placing and control of electrolysis based hydrogen filling stations operating within radial distribution networks has been proposed and its performance is assessed using a United Kingdom Generic Distribution System (UKGDS) case study. The controller objective is to dispatch alkaline electrolysers appropriately to increase the amount of integrated wind power capacity and reduce the grid losses within the network while satisfying the network constraints and respecting the electrolyser characteristics.In addition, a MATLAB Simulink model has been developed to investigate the impact of alkaline electrolysers as dynamically controlled loads for the stabilisation of system frequency in the case of a sudden loss of generation and also when the power system has high penetrations of wind power. The electrolysers are controlled according to a droop control strategy. A novel approach to determine the aggregate nominal electrolysis demand for frequency stability purposes has also been proposed in this work, and the financial viability of the proposed strategy to control electrolysers has been assessed.Finally, several scenarios have been modelled to investigate the role of electrolysers to absorb surplus power and produce hydrogen for the fuel cell vehicles in the UK in the year 2050. Different wind, solar and nuclear power generation capacities have been considered. On the demand side, different penetration levels of electric vehicles and hydrogen fuel cell cars have been modelled. The results are discussed and analysed.Keywords: Alkaline electrolysers, Renewable power, Active Network Management, Distribution network, Power system stability, Hydrogen economy, Power system losses, Demand side management, Load Frequency Control, Energy storage.Hydrogen could be the best candidate fuel for our future, especially in the transportation sector. It could be generated using water electrolysers running with power from carbon-free, renewable resources, since this is zero emission at the point of use, and so can help transition from the energy infrastructure available today into an energy world with a growing renewable electricity supply.This work models a highly distributed electrolyser system e.g. an urban hydrogen filling station network, and explores the Demand Side Management (DSM) potential of these electrolysers to improve the performance of the power system operating under the impact of intermittent renewable power generation.A comprehensive literature review has been carried out on the hydrogen economy, electrolysers and the potential role of storage devices in power systems. Three main areas related to alkaline electrolysers working within power systems were identified for further exploration. - Potential role of electrolysers in the existing distribution networks to increase the integrated wind power capacity - Potential role of electrolysers to stabilise the frequency of the power system - Potential role of electrolysers to absorb any surplus, carbon free, generation within the UK electricity networkThe first item of archival value within this work is the identification, presentation and discussion of electrolyser characteristics which are relevant to the introduction of an acceptable control strategy to integrate such electrolyser loads within the power system and thus provide improved performance of the network when exposed to the highly time variable energy supply from renewable sources. Two types of electrolyser made by NEL Hydrogen are detailed: atmospheric and pressurised. Their characteristics are reported in this thesis using the results from experiments designed by the author. In addition, an experiment has also been carried out on a PEM electrolyser available at Strathclyde University to compare its results with the characteristics of the commercial alkaline units. Second, a novel algorithm for sizing, placing and control of electrolysis based hydrogen filling stations operating within radial distribution networks has been proposed and its performance is assessed using a United Kingdom Generic Distribution System (UKGDS) case study. The controller objective is to dispatch alkaline electrolysers appropriately to increase the amount of integrated wind power capacity and reduce the grid losses within the network while satisfying the network constraints and respecting the electrolyser characteristics.In addition, a MATLAB Simulink model has been developed to investigate the impact of alkaline electrolysers as dynamically controlled loads for the stabilisation of system frequency in the case of a sudden loss of generation and also when the power system has high penetrations of wind power. The electrolysers are controlled according to a droop control strategy. A novel approach to determine the aggregate nominal electrolysis demand for frequency stability purposes has also been proposed in this work, and the financial viability of the proposed strategy to control electrolysers has been assessed.Finally, several scenarios have been modelled to investigate the role of electrolysers to absorb surplus power and produce hydrogen for the fuel cell vehicles in the UK in the year 2050. Different wind, solar and nuclear power generation capacities have been considered. On the demand side, different penetration levels of electric vehicles and hydrogen fuel cell cars have been modelled. The results are discussed and analysed.Keywords: Alkaline electrolysers, Renewable power, Active Network Management, Distribution network, Power system stability, Hydrogen economy, Power system losses, Demand side management, Load Frequency Control, Energy storage