One of the project goals was to provide an optimum catalyst, which has sufficient activity, durability and is robust and insensitive to harmful compounds (CO, sulphur compounds, etc.) that can potentially be found in the input gas. First, a set of commercially available catalysts was evaluated and later, the new catalyst was developed and tested. Besides, several procedures for catalyst regeneration were proposed and tested. Regeneration is needed to recover the catalyst activity after being exposed to harmful gas compounds for a longer period. Part of the conducted research was submitted and accepted for publication in scientific paper: C. Jackson, L. Raymakers, M. Mulder, A. Kucernak. Electrochemical Hydrogen Pumps for Hydrogen Purification and Compression: Characterisation of Electrocatalyst Performance. Applied Catalysis B: Environmental.
Another important component are bipolar plates. Their purpose is electric connection of neighbouring cells and distribution of gases and cooling media over the cell membranes. The initial idea was to fabricate bipolar plates by the technology of hydroforming, which allows mass production at demanding configurations in a cost-efficient way. Samples have been made and a number of steel types and coatings have been tested to evaluate corrosion resistance and forming ability. The technology was presented by partner Borit at two fairs: FC Expo 2019, Tokyo, Japan and Hannovermesse, Hannover, Germany, both in 2019. Unfortunately, testing revealed that hydroformed bipolar plates were not able to sustain the planned 200 bar pressure, so their use is for now limited to low pressure purification.
To optimize the EHP process, it is necessary to understand, how bipolar plates distribute the gases and humidity over the EHP membrane and what is the effect of channel configuration and shape. Physical experimentation and in-situ measurement are technically almost impossible, so modelling and simulation is a primary tool for analysis. Within the project, a computational fluid dynamic (CFD) model for the EHP stack was developed and presented in journal paper: U. Reimer, D. Froning, G. Nelissen, L. F. J. M. Raymakers, S. Zhang, S. B. Beale, W. Lehnert. An Engineering Toolbox for the Evaluation of Metallic Flow Field Plates. ChemEngineering (2019) 3, 85.
For autonomous operation of EHP system balance of plant sub-systems are needed: a control system for automatic operation, and diagnostic and condition monitoring to detect process irregularities. This requires the algorithms (software) and electronic equipment (hardware). Voltage monitor and power supply electronic units were developed in modular way, addressing the specific needs of the EHP system of various sizes. A comprehensive documentation was prepared for knowledge transfer. Control algorithms for the control of EHP systems (gas delivery, humification, preheating, cooling, mass and energy balance supervision) were developed and tested. Novel type of condition monitoring algorithm was developed, which is based on electrochemical impedance spectroscopy and pseudo random binary excitation signal resulting in much shorter testing duration. For now, this method was presented on the conference: G. Nusev, G. Dolanc, D. Juričić, P. Boškoski. Detection of membrane drying at electrochemical hydrogen compressors. 54th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST), June 27-29, 2019.
The geometry and catalyst material of the EHP stack were continuously improved to achieve long-term stable operation and to meet target parameters (energy efficiency, OPEX, production costs, CAPEX, resistance against harmful compounds of the input gas). The iterative development and testing results in the GEN3 stack with its best performance: energy demand 6.4 kWh/kg H2 at an 83% recovery rate or a 41.3% recovery rate at a 4.6 kWh/kg H2 energy demand. This is an improved result, however still not meeting the target for the recovery rate of 95% and the energy demand of the EHP stack of 3 kWh/kg H2. One of the important results is also 3-month testing of the sub-sized EHP stack proving the stability of the performance. The properties and potential of EHP technology were presented on fairs and conferences, e.g.: L. Raymakers. Electrochemical Hydrogen Compression in the Hydrogen Fuel Chain. F-Cell Conference. Stuttgart, Germany, Sept. 10-11, 2019.
Economic aspects of EHP system were analysed. It was shown that the electrochemical cell itself is the main driver for the costs of the system. There is trade-off between investment and operating costs. For a given hydrogen purification rate, large EHP systems with low current density lead to high investment and low running costs. On the other hand, small EHP system with high current density lead to low investment and high running costs. Considering long term operation (20 years), large systems are the preferred solution, since savings due to the reduced OPEX are larger than savings due to lower CAPEX.
A comprehensive market exploitation plan was prepared. Several possible market applications were identified. The two main applications are: the purification of hydrogen in reformate gas and the extraction of hydrogen from a natural gas grid with admixed green hydrogen. In both cases extracted and purified hydrogen is to be used for local (residential) FC CHP units and/or local fuelling stations for FC vehicles. Market potential is estimated on the basis of predicted evolution of FC CHP units and FC vehicles.
