Purification of Process Media for Fuel Cells
Development of a Water Cycle to Supply Solid Oxide Fuel Cells (SOFC) in the E2P2 Project
The consortium of seven companies - Equinix, Infraprime, RISE, Snam, Solidpower, Tec4fuels and Vertiv - is exploring a novel integration of solid oxide fuel cells (SOFC) with uninterruptible power supply (UPS) and lithium-ion batteries to provide reliable and clean primary energy to data centers and other critical infrastructure. The introduction of natural gas SOFC as a main power application is expected to pave the way for the use of green hydrogen for fuel cells, both for back-up and main power systems.
Alternative power supply for data centers
Fuel cell power is also considered a cleaner and quieter power solution for data centers that can relieve pressure on public power grids. They can be deployed on a data center campus and are suitable for operation with natural gas, biogas, liquefied petroleum gas or green hydrogen. Their transport and distribution are possible via existing gas grids.
"Tec4Fuels contributes its know-how in the supply and purification of the process media gas and water for the operation of the fuel cells," explains Klaus Lucka, managing director of Tec4fuels. "For this, we provide the necessary peripherals in the project and integrate them into the system." Purification of the process water is a relatively new component in the development of fuel cell systems. To ensure the safe operation and optimal service life of fuel cells, the continuous supply of fresh water for system processes is the norm. As an alternative, the company is developing a water circuit for the fuel cell process water supply in which the water is continuously purified by an ion exchanger. The purification process must be adapted to the contaminants occurring in the circuit. Analyses of water samples from an SOFC fuel cell operation show that, in addition to silicon dioxide, metal ions such as nickel and copper are also present as contaminants.
Purification of process water and natural gas
"SOFC fuel cells are very sensitive to impurities and can degrade quickly. As the fuel cells degrade during operation, the amount of metal ions in the process water increases. With a total of 16 fuel cell stacks in the demonstrator and around 400 m3 of water per year as the total volume to be purified in the process water circuit, purification is an important aspect of extending the service life of the stacks," explains Klaus Lucka.
During fluid condition monitoring, online monitoring of the electrical conductivity of the water is planned, with which the total proportion of metal ions in the water can be determined. One of the central measuring points is to be located downstream of the ion exchanger so that its saturation can be detected at an early stage and maintenance can be initiated. Furthermore, it is important to continuously monitor the CO2 content in the water because of an increasing CO2 content reduces the exchange potential of the ion exchangers. It is envisaged to keep the content constant through an intermediate tank by measuring the ph value and adding an acidity regulator. Degassing technologies are not an option in this application because of the associated technical effort and cost.
In addition to process water purification, gas treatment is also required in the overall system because demonstrator operation with natural gas, which contains sulfur as an odorant, was initially planned. Since sulfur components in the natural gas would lead to rapid degradation of the fuel cells, three activated carbon filters are used for complete desulfurization. As soon as the system can be operated reliably with natural gas, it was planned to add successively increasing proportions of hydrogen. When operating with pure hydrogen, gas treatment is unnecessary.
Standardized systems available on the market are used for the peripheral systems water purification, process water system, exhaust gas system and gas treatment. One challenge is to integrate the peripherals into the overall system of fuel cell stacks, power electronics and uninterruptible power supply in such a way that they fit into the intended compact installation space of the demonstrator. This consists of a special housing for the power supply of small data centers.
Both the cooling water system and the gas treatment system are designed with redundancy. Ideally, one string of each of the two systems is running. The purification systems are designed for a service life of around 8,000 hours, which corresponds to an operating time of just under one year. Thanks to the redundancy, the ion exchangers and the activated carbon cartridges can be easily replaced during operation.
The key challenge in the E2P2 project is to test existing technologies and systems for their functionality and cost-effectiveness, and to assemble and adapt them so that they function safely and reliably in the compact installation space of the demonstrator. Since there are no standards yet for on-site power generation in data centers, the consortium aims to develop an authoritative open standard. This could pave the way for the commercialization of fuel cell power for data centers in Europe and demonstrate the industry's potential role in meeting EU CO2 reduction targets. The European Commission is supporting the research project with EUR 2.5 million.
This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under Grant Agreement No 101007219. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research.”