Aeristech developing turbomachine-type electric air compressors for fuel cells; claims potential doubling of output
UK-based Aeristech, a provider of electrically driven pressure charging solutions (earlier post), is developing electric air compressor technology that the company says could double the output from a hydrogen fuel cell. The electric compressor would enable vehicle manufacturers to increase performance or to specify a considerably more compact fuel cell, improving packaging and weight.
The Aeristech fuel cell compressor uses an aluminium, turbomachine-type compressor with volume automotive manufacturing tolerances, direct-coupled to a variable high-speed motor with no transmission. This represents a significant change from roots- and screw-type compressors.
Funding from Innovate UK (formerly the Technology Strategy Board) has contributed to the development of a 10kW fuel cell air compressor; other project partners included Imperial College, which will provided a compressor design capable of constant boost across a range of mass flows and Intelligent Energy, which integrated the electric booster into its fuel cell and fuel cell controller for performance testing.
|Aeristech says that its electric compressor technology could double the power output of a hydrogen fuel cell. Click to enlarge.|
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 The hydrogen is already at high pressure, having evaporated from the liquid state, but air is usually pressurized 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.—Aeristech CEO Bryn Richards
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 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. 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.—Bryn Richards
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.
Aeristech was founded around an innovative permanent magnetic switching architecture that has enabled Aeristech to produce that it says is the most power-dense electric motor of its type currently available. Aeristech’s motor control strategy separates commutation and power control. This approach reduces the cost of many key switching components while ensuring accurate high-transient speed control.
This core technology forms the basis of the company’s range of products, which now include an electric supercharger, full electric turbocharger, fuel cell air compressor and turbine generator.
Aeristech designs, tests and develops every aspect of the system, from the bearings to the compressor wheel.