Analysis of component operation in power-to-gas-to-power installations

This article presents results of research into hydrogen generators and fuel cells (basic elements in Power-to-Gas-to-Power systems) together with an economic analysis of this installation type. A hydrogen generator containing two AEM (Anion Exchange Membrane) alkaline electrolyzers with a performance of 0.5 Nm3 H2/h and a PEM fuel cell with an electrical power of 0.72 kW were tested. A methodology is presented for determining gross and net efficiency characteristics of the tested devices using measurement results. These operations allowed assessment of the efficiency characteristics as a function of electrical power and identification of the power needs of a hydrogen generator and a fuel cell system. This is important because in P2G2P installations integrated with renewable energy sources these devices operate with variable loads. For a nominal power value, the efficiency of the hydrogen generator was 63% and the efficiency of the fuel cell system was about 40%. For an energy storage system in hydrogen form, a simplified methodology for determining the price ratio of the electric energy sales to the purchase price of the electricity was determined, in order to discover whether the system could be economically efficient. This allowed the determination of the components of this relationship related to the efficiency of the installation and the investment costs of each element. Economic analyses assumed the installation operated with nominal power for a certain period of time throughout the day, strictly connected to the valley and peak of electricity demand. Analysis results are presented as a function of P2G2P system efficiency and working time of hydrogen generators and fuel cells during twenty-four hours. Studies and analyses were performed for P2G2P installations with the most commonly considered elements in energy storage systems. These are considered a very promising solution to the energy balance process, for connecting a high amount of power from renewable energy sources to the power grid.