Performance data

Wind tunnel testing

The silent vertical axis wind turbine (VAWT) underwent wind tunnel testing at Kingston University London from October 2006 to April 2007.

This initial testing proves that out silent wind turbine performs as expected – and in some aspects, even exceeded expectations.

Key findings

§         Low start up speed: the silent wind turbine by Luethi Enterprises needs less wind to start up than most competing designs. The start up wind speed is approximately 3.6 metres per second (8.1 mph; 13 kph; 7 knots).

§         No cut out speed: the wind turbine can cope with high wind speeds and does not need to be shut down.

§         No loss of power at high winds: the turbine continues to produce optimum power at high wind speeds.

§         Turbine calibration: the silent wind turbine by Luethi Enterprises can be calibrated according to the prevailing wind conditions where it’s installed. With less weight the turbine blades close much earlier and do not exceed a given maximum rpm (revolutions per minute). So in a low wind area more weight could be installed in the regulating mechanism in order to open the blades and get as much wind as possible into the turbine. Conversely in high wind areas less weight would be installed in the regulating mechanism to regulate the output and also protect the turbine from excess wear and tear.

§         Blade configuration: the optimum number of blades was identified for the silent wind turbine.

These tests were financed by a POCKET Loan from Finance Southeast. Funded by the UK Government and the EU via SEEDA (South East England Development Agency), these loans have stringent application criteria and can only be obtained when working in partnership with a university.

Wind speed conversions

For example:

1 m/s = 2.2 mph = 3.6 kph = 1.9 knots

5 m/s = 11.2 mph = 18 kph = 9.7 knots

About performance curves for wind turbines

There are many variables in how test data is obtained: location, altitude, wind tunnels, truck tests, and so on: there is no set standards that manufacturers must comply with. Consequently this leads to differences in data accuracy, with many manufacturers opting to publish their “potential” data rather than average results. Which is why so many people who have invested in a small wind turbine have been disappointed with the performance.

Luethi Enterprises publishes the average results, that is, what you can expect to obtain from our silent wind turbine: we want you to be delighted with our product.

All power curves assume that wind is from a consistent direction, as in a wind tunnel. In reality wind oscillates constantly: this does not affect the silent wind turbine by Luethi Enterprises, as the blades are always facing the wind. However, it does affect horizontal axis wind turbines as they lose power as they reposition themselves, and it takes a little time for the turbine to produce optimal power once more.

Another difference between this power curve and that of most other turbines, is that the other turbines have a cut-off speed: ironically, they cannot operate in extremely windy conditions. The silent wind turbine by Luethi Enterprises continues to produce optimal power even in extreme winds, with the feathered blades protecting the turbine.

What’s the next step?

Additional testing is required once the electronic system (dynamo motor and inverter) has been built, and the shape of the blades will also be refined for maximum efficiency.

This test data will provide us with the finalised power curves to enable us to commercialise the silent wind turbine and put it into production, along with the necessary health and safety certification.

The materials used for the construction will also be tested and selected.

If you’d like to get involved, please see the opportunities and contact us.

Read about applications and installation examples here.

Luethi Enterprises Limited       Email: info@silentwindturbine.com        Phone: +44 (0) 1634 711 179

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