Compact hydrogen fuel cell gives higher performance

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Compressor for improved fuel cell output

Aeristech has reduced the mass of its air compressor technology to enable higher efficiencies and continuous boost pressure for its hydrogen fuel cell.

Aeristech has developed a breakthrough in electric compressor technology that could double the output from a hydrogen fuel cell. It enables vehicle manufacturers to significantly increase performance or specify a considerably more compact fuel cell, improving packaging and weight.

“The power output of a fuel cell is limited by the rate at which air can be supplied to sustain the reaction between hydrogen and oxygen,” explained Aeristech CEO Bryn Richards. “The hydrogen is already at high pressure, having evaporated from the liquid state, but air is usually pressurised using a blower. Our proprietary high speed motor and control technology allows us to deliver air at a much higher pressure increasing the rate at which the oxygen passes through the permeable membrane; no other motor control arrangement is able to deliver at this pressure with such a high efficiency.”

The output voltage from a fuel cell fluctuates, so a conventional electric compressor requires an intermediate voltage regulation to provide constant pressure, adding system losses. Aeristech’s unique motor control technology delivers constant torque and therefore air pressure, independent of air volume or variation in input voltage, so can be powered directly from the fuel cell.

“Using our patented motor control technology we are the first company to deliver motors that are sufficiently cost-effective for use in electric compressor applications,” said Richards. “Compared to a competing electric compressor providing the same boost pressure, Aeristech’s compressor saves 70% mass on a full system basis including control unit, motor and compressor. The more usual switched reluctance type high-speed motor would be unable to operate continuously at such high continuous power levels because of thermal management issues. This is why competitors tend to use heavy low-speed permanent magnet motors with step-up transmissions to run their compressors, creating a bulky system.”

Funding from Innovate UK (formerly the Technology Strategy Board) has contributed to the development of a 10kW fuel cell air compressor which is presently being tested on fuel cell stacks with a customer. The results from these tests should be available by the end of the year.

Aeristech is also able to supply a 20kW compressor, with a performance map and 400V control architecture tailored to the needs of a fuel cell powered vehicle, for testing and demonstration purposes.

Hydrogen as a vehicle fuel

Hydrogen is the most common fuel used in fuel cell-powered vehicles because of its high energy density and because the only emission it produces is water. In the fuel cell, hydrogen reacts with oxygen in a process that releases electrons as a source of electrical energy. The hydrogen is stored as a liquid while atmospheric air is used to supply the oxygen.

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