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Performance data

Field testing

A 500W DC micro wind turbine prototype spent a number of months undergoing field testing at the SEEDA site at Chatham Maritime.

This yielded the following results:

Startup Wind Speed: 3.5m/s = 8.1mph or 13km/h or 7 Knots
4.2m/s (10mph) = 50 rpm producing 10VDC =130W
8.3m/s (19mph) = 100 rpm producing 20V DC = 260W
13.1m/s (30mph) = 150 rpm producing 28V DC = 360W
18.5m/s (42mph) = 200 rpm producing 36V DC = 470W
22 m/s to 35 m/s = (50 mph to 80 mph) producing 38V = 500W

Size of this model: 900mm wide; 1000mm tall

Weight (Including 1000mm mast): 65kg

Above: Field testing a prototype of the 500W DC silent wind turbine at Chatham Maritime.

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.

Above: The Silent Wind Turbine by Luethi Enterprises continues to produce maximum power even at high wind speeds, when other windmills have to be shut down.

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.

Field testing

As well as the wind tunnel testing, field testing in exposed positions has been taking place since 2006 and has proven the durability and capability to cope with extreme weather conditions.

One of the prototypes was left in situ for six months, during which there were numerous gales, strong enough to blow the chimney pots off a neighbouring house.

At the end of this period, the turbine was inspected for damage and wear and tear: none could be found. The silent wind turbine by Luethi Enterprises is durable and one of the few which can cope with high wind speeds – and continue to produce power.

Above: This prototype has been in situ since 2006 and is still going strong, despite several storms hitting the area.

Wind speed conversions

To convert	Into	Multiply by
Kilometres per hour	Miles per hour	0.6214
Miles per hour	Kilometres per hour	1.609
Kilometres per hour	Knots	0.5396
Knots	Kilometres per hour	1.853
Metres per second	Feet per second	3.281
Feet per second	Metres per second	0.3048
Miles per hour	Knots	0.869
Knots	Miles per hour	1.151
Feet per minute	Metres per second	0.005084
Metres per second	Feet per minute	196.85
Knots	Metres per second	0.515
Metres per second	Knots	1.944
Miles per hour	Metres per second	Divide by 2.23694

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.

Read about applications and installation examples here.

Creating new and alternative solutions in energy production

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

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