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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.



I'm not sure if this will also change the power output profile of a fuel cell - PEMs usually operate most efficiently at low load, which is part of the reason that they are designed as hybrids, with the ~1 kWh battery there to provide peaking power for acceleration.

I take this, assuming it is satisfactory from a reliability POV, to mean that fuel cells are almost ready to take the next step up from the already excellent and fairly compact unit in the Honda, already a pretty good step up from the Toyota Mirai.

Things change fast in the world of fuel cells.


This could mean that future FCs equipped with this smaller volume compressor could also be much smaller for a given energy production.

Smaller, lighter FCs could leave more space for H2 tanks giving a further boast in total range and/or increased vehicle efficiency.

Improved FCEVs will soon reach 100 mpge or about 5X equivalent ICEVs. H2 at 4X the price of gasoline would then become effectively cheaper than gas..


One advantage of a fuel cell range extended EV is a smaller fuel cell with smaller balance of plant components.


It would be good if we had some energy density numbers for the flexible metallic organic framework storage mentioned here a couple of days ago.

Dimly perhaps but with increasing definition attractive future transport possibilities are hoving into view.


Honda has been quite vocal regarding the strategy to downsize their fuel cell so we'll see soon enough how well it stacks up to what has been done by others. Cost seems to be the main benefit as it reduces precious metal use and the improved packaging allows for platform sharing across other powertrains and economies of scale that follow. it is unclear if what Aeristech has done here is actually innovative or enabling as the marriage of turbomachinery and efficient high speed electric machines is hardly new.

Henry Gibson

INNAS NOAX has their Chiron fluid pumping diesel engine with no crankshaft to pump high pressure fluids for use with the ARTEMIS digital controlled rotary motor/pumps and gas-bladder-pressure tanks, and this combination can double the fuel efficiency or more even on motorways at costs far lower than fuel-cells and electric motors.

In many places water consumption is limited by law. Hydraulic hybrid technology is so cheap and efficient now that it should be required as are seat belts and crash bags. No improvements of standard engines can match the cost and energy advantages of digital hydraulics, Chiron is also digital with one major moving part. Two parts may be needed for balance.

Parry People movers have had efficient hydraulic rail passenger vehicles in commercial operation for many years. ..HG..

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