Bi-directional turbines for converting acoustic wave power into electricity
Bi-directional turbines for the conversion of acoustic power into electricity as they were introduced by Aster early 2012, has turned out be a successful approach both in scaling up in power levels and in reduction of complexity and manufacturing cost.
To demonstrate the simplicity of the concept you may have a look at the video below, which shows a small bi-directional turbine plus generator, driven by the periodic acoustic flow from a loudspeaker.
What is interesting to see, is that the electric output (light) is hardly dependent of the acoustic frequency. This is an additional benefit of the bi-directional turbine concept because of the oscillation frequency of thermoacoustic engines varies with temperature which in case of resonant linear alternators could lead to detuning and performance degradation.
Since the first experiments a lot of progress is made in the understanding, design, modelling and construction(e.g. 3D-printing) of this type of A-E conversion and at present a full scale bi-directional turbine operating in 3.6 MPa helium is under construction to be applied in a 14kWe thermoacoustic power generator.
Last year some details and intermediate results on this A-E conversion concept were presented during the 9th International Pamir conference and Summer School, both held on June 16-20,2014 in Riga, Latvia. The paper and presentation may be viewed here.