A micro GT to compete with small diesels

The micro GT project, developed with funding from the Royal Australian Air Force and the South Australian government, aims to replace the mobile diesel generators typically used to provide electricity in the field.

The prototype unit (Figure 1) is only 10 % of the weight of a typical diesel or gas fired generator and can be configured to run on a range of liquid and gaseous fuels including propane, natural gas and diesel oil. It was demonstrated in a series of sessions with senior Defence personnel in the Australian capital Canberra in November. Military interest in the project, which has been active from the beginning, stems from unit’s possibilities for use in the field: the demonstration unit weighs only 48 kg, excluding the control system and the fuel tank, compared to 433 kg for a current military diesel generator. It is also about two-thirds the size of the diesel engine, measuring about 600 mm long and 250 mm wide. ecoJet received its funding at the beginning of this year to progress its concept design for a 20 kW micro gas turbine into a viable prototype unit.

It now plans to use its technology to develop a commercial product for households and industry, to complement existing technologies such as solar panels and battery storage.

Next steps

ecoJet co-director Alexander Wright said the mobility of the unit, the versatility of the fuel source and potential for more efficient electricity production were among the advantages of the system compared with traditional diesel generators. The demonstration unit, he said, already had flow rates comparable with current commercially available diesel generators.

“We have a lot of scope for improving our efficiencies above that in areas like heat recuperation, bearing advancements, the use of advanced materials such as ceramics and graphenes and multi-stage turbo machinery, which is uncommon for turbines of this scale.

“It is quite efficient and it’s not restrictive of other technologies, it can work quite well in parallel with solar and battery storage so it’s not a competitor to other products exclusively – it can complement other systems.”

The concept uses an unusual integrated design of compressor and turbine. “Our novel solution includes an integrated shaft assembly where the shaft that connects the turbine and the rotor has an integrated generator attached to it” said Wright.

Beginnings

The collaboration between Wright, James Kim and Warren Day that led to the formation of ecoJet Engineering began in 2015 with an Honours project at the University of Adelaide that achieved one of the world’s smallest ultra-micro gas turbines. (Figure 2).

Through further studies at the University of South Australia, the collaboration won a Venture Capitalist grant in 2016, which helped launch the company.

ecoJet Engineering pitched its ultra-micro gas turbine design at this year’s Land Forces event in Adelaide where it was named best innovation.

In February 2018 the EU funded a project to develop the 10 kW design into a radial micro GT tailored for environmentally friendly micro CHP applications for the residential sector. UK engineering company PCA joined the project with the task of optimising the flowpath for the gas-swept surfaces in the novel integrated design and in the understanding of the performance implications of this close-coupled, low cost approach.

Potential

Wright considers that the micro GT design also has potential as a domestic product to complement renewable technologies such as solar panels, and help households become independent from the electricity grid.

“A military product is a commercial product with a bunch of extra stuff on top so we can easily tweak it to suit both markets because we are very much looking to break into both areas,” Wright said. “We’re planning a fairly rapid development timeline and as part of this demonstration we’re looking for further investment from defence and government grants.”