Experimental Identification of the Energy Cogeneration Process of a Miniature Hybrid System with a Wind Turbine and a Reversible PEM Fuel Cell – the Sankey Diagram

The article addresses the key operation problem of complex power systems based on renewable energy sources – their irregular availability. This impels the need to search for effective methods of storing the energy generated in this way in various types of hybrid systems. One of the proposed solutions to this problem is presented in relation to wind energy, especially offshore, in which excess wind energy is used to produce, store and reuse hydrogen in a hybrid system with a reversible PEM fuel cell. The configuration of a laboratory test bed for such a system, built on a miniature scale, is presented, along with a developed physical model of the cogeneration process of various forms of energy worked out in it. It was the basis for designing and building a measurement and recording system for the observed standard parameters, which allows for experimental identification of the places where the greatest energy losses occur in the hybrid system under consideration. Based on the conducted model tests of the energy cogeneration process in steady-state operation, the streams of transmitted and transformed energy in the system were determined, using a calculation algorithm especially developed for this purpose. The elaborated Sankey diagram stands for the graphical interpretation and synthesis of the obtained calculation results. It distinguishes energy flow bands for the implemented basic (working) and additional (accompanying) processes. On the one hand, it is a useful tool for verifying the correctness of the selection of individual functional modules of the designed power system, and on the other hand, it supports the process of diagnostic reasoning about their technical health.