Hydrogen fuel cell regulation and testing solutions
Hydrogen fuel cells are a clean, environmentally friendly alternative to traditional combustion processes. While they show tremendous promise, process efficiency needs to be improved for them to become truly viable as an alternative energy source.
Precise and adaptive regulation of system pressures and the mass flow of gas lines can make all the difference in developing an efficient hydrogen fuel cell system. In this article, we cover the various sensing technologies in fuel cell applications and discuss how mass flow and pressure devices are used to optimize these technologies.
Application 1: Hydrogen generation – Electrolyzer system testing and regulation
Electrolysis is a promising method of green hydrogen generation, which breaks down water molecules with hydrogen and oxygen. But there are a few challenges presented by the current electrolysis process, from varying power input of renewable energy sources to the continuous drive for cost reductions.
The low flow rates and high water temperatures used in electrolysis make precise system testing and regulation difficult. Using mass flow technologies that measure low flow with high accuracy in high temperature conditions can ensure the success of your process. Coriolis mass flow instruments are capable of measuring and controlling mass flow rates as low as 0.08 g/h at temperatures up to 70°C.
Ensuring electrolysis efficiency also requires fast and responsive pressure control to maintain the differential or balanced pressures between oxygen and hydrogen. Depending on the scale of the process and methods used, factors such as high temperatures, pressures, and gas humidity can make this a bit tricky. But a multi-orifice back pressure regulator is able to regulate electrolyzer system pressure over a wide range (10,000:1 turndown) while remaining unaffected by moisture.
Application 2: Hydrogen fuel cell testing
Fast and accurate instruments throughout the fuel cell system make life much easier when conducting PEM fuel cell testing and diagnosis, and large turndown ratios allow processes to be easily scaled through the development process.
Regulating oxidant and reactant ratios and distributions across gas diffusion layers of stacks is key to maintaining the efficiency of hydrogen fuel cell technology, making reliable and fast responding flow regulation an invaluable asset to fuel cell test benches. When process conditions include high pressures and low flow rates, a Coriolis mass flow controller is a reliable, high-accuracy option. For higher flow rates of mainline inputs and outputs, a differential pressure mass flow controller can be used to monitor both pressure and mass flow simultaneously over a wide range of flow rates. It is also important to maintain tight back pressure control, which can be difficult in environments with high temperature, high humidity, and moisture. Like in electrolysis, a multi-orifice back pressure regulator is well suited to maintain ideal reaction conditions in fuel cell systems, allowing pressure regulation down to 0.0001 PSIG in most testing conditions. We also offer stainless steel differential pressure mass flow meters that provide fast and accurate mass flow readings, unaffected by moisture passing through the unit.
Yet another challenge is regulating temperature across the stack to maintain a consistent rate of power distribution. Improper regulation can cause efficiency losses and even damage to the stack elements. This challenge becomes increasingly more difficult as the number of cells increase. Incorporating differential pressure mass flow controllers with <50 ms response times and 10,000:1 turndown ratios can ensure fast, stable temperature regulation.
Humidification is equally important to ensure efficient proton conductivity across the electrolyte layer as an excess or deficit of water can greatly impact fuel cell efficiency.
Application 3: Fuel cell test stations – Leak checks and membrane permeability tests
Leak checking fuel cell systems – especially membrane leak and permeability testing – is vital for ensuring consistent flow rates, maintaining process efficiency, and minimizing loss of reactants such as high value heavy metals in the catalyst layers of membrane electrode assemblies. This can be particularly challenging in larger volume fuel cell systems where testing multi-stage processes can lead to flow spikes during the test process.
Leak check stations are typically composed of two components. The first is a dual valve pressure controller which makes measurements every 30 ms and ensures the element under test remains at a set pressure while minimizing He usage. Meanwhile, highly sensitive PID tuning and setpoint ramping functionality help protect the membrane from flow spikes during testing. This is combined with a low pressure drop mass flow meter to characterize the slightest leaks, with a pressure drop as low as 0.07 PSID across the unit. These two instruments can be controlled from a single computer/PLC using an array of communication protocols for easy automation and data analysis.
Application 4: Hydrogen fuel cell regulation
Once optimal gas ratios, flow rates, pressure, and temperatures have been established, Alicat solutions can be used to regulate and monitor your finished fuel cell systems.
Pressure regulation units can be used in combination with external sensors to regulate pressure upstream of the sensor position. In high temperature, high humidity lines, remote sensors and valves can also be employed for pressure regulation. Fast response times and turndown ratios of up to 10,000:1 ensure that pressure and mass flow controllers can precisely control hydrogen flow into pre-heating systems and maintain fuel cell system efficiency. Meanwhile, a multi-orifice back pressure regulator maintains exhaust gas output.
Solutions for other areas of fuel cell research
For the many other processes and tests that are required in areas relating to hydrogen fuel cell system R&D (e.g. catalyst verification and electrode testing) we have a range of custom mass flow and pressure solutions using a variety of technologies.
If you have any questions about solutions for testing and regulation of hydrogen fuel cell technologies, you can contact our applications engineers and they will help find a solution for your process needs.