Engineers from the University Otto von Guericke of Magdeburg are developing intelligent turbines for green energy from tidal waterpower.
This new tidal waterpower system ensures that during each revolution, the blades adjust optimally to the water flow, and thus avoid the dangerous stall condition – the separation of flow away from the surface of turbine blades. This leads to a loss of efficiency, and over longer periods of time, to material failures and fatigue fractures in the turbine rotors.
Fluid engineer Dr Stefan Hoerner from the Institute of Fluid Dynamics and Thermodynamics said: “Until now, those stresses had to be compensated for with stronger components, using more or high-performance materials. From the economic and ecological points of view, both are rather expensive. With the new technology, it should become possible to actively control the flow around the blades and as a result design turbine to be lighter, more durable and thus more efficient.”
Through the movement of the blades, the integrated drives are able to influence and optimise the flow in such a way that they achieve maximum efficiency with minimum strain. Hoerner added: “This translates in higher electrical output, and at the same time the structure can be designed to be more slender. In turn this helps to save materials and to increase the lifespan of the turbines in sustainable tidal or run-of-river power plants.”
The drives are being designed and integrated into the turbine blades by the interdisciplinary team led by Hoerner and Professor Roberto Leidhold from the Institute of Electrical Energy Systems in the university’s Faculty of Electrical Engineering and Information Technology.
Hoerner explained: “In fluid mechanics terms this is useful, as in this way they do not generate any additional drag. In the model that we intend to test in our flow channel, it will be an additional challenge to design the motors so that they are very small and yet still strong enough. At their thickest point the blades are only a little thicker than a centimetre.”
Testing the reduced-weight turbine model
The design and stability of the reduced-weight turbine model will be tested with computer simulations before the practical test takes place in the water channel. Hoerner said: “If this undesirable effect—blade stall—can be controlled and we are able to significantly increase the efficiency and lifespan of the turbines, we anticipate great interest in a broad industrial application of the technology in the pioneering industry of tidal energy.
“The ecosystems of the seacoasts and rivers are already very heavily exploited by man. For this reason, every additional square metre on which we build must be utilised as well, and at the same time as sustainably, as possible. This will help to combat climate change and to sustainably use a source of renewable energy—hydropower—that until now has only be used to a limited extent.”
Until now, conventional hydropower has not truly been sustainable, since dam systems have great potential for ecological and social harm, such as loss of biodiversity, injuries to fish, disruption of sediment transport, and land loss. Hoerner added: “This is why we are working on an unconventional technology that functions more like a wind turbine and is therefore considerably more sustainable.”