Hi Hugh…its all a question of balance…the tip speed it the key. The Thermodyne converted alternators require rpm to make power. You are right a big 3 blade will generate huge torque…but at a lower speed. The Termodyne latest blades 880mm KT Pantera blades with a squared off tip..promote everything tip speed. The trick with these turbines is not to get an early stall….so you need a load curve that allows the shaft speed to get over 200 rpm or more…beyond that you can start to load the turbine. Many installations of this turbine just start spinning up then stall….as they are subject to too much load. 400 to 450w in a moderate wind for a 28 magnet dual pma is very realistic….and actually quite good. There are also many reports that these turbines can withstand 80mph gales with no curling or damage…
Hi Richard,
To get the maximum swept area and maximum rpm you need to have a high tip-speed-ratio. If you study blade design you will find that this means fewer blades (and also the correct blade angle etc). By reducing the number of blades you can achieve a trade off giving larger diameter. So if you go for example from five blades to three then you will run fast in a given windspeed and you can use a larger diameter to achieve the same rpm.
When I started out (in the 1970s) I used two blades for this reason and they ran very fast. Nowadays I use 3 because they run more smoothly. I see no advantage to using five blades. I use low speed alternators that are specially designed for wind so they start up easily and have good efficiency at low power. They are also heavy enough to cope with high power.
As for handling high winds without damage I know a guy in the western isles who tried out a Hornet recently and it only lasted a couple of days. Your man Les was unhelpful and abusive. The design is really too lightweight to deliver the ridiculous outputs it claims to be capable of and unfortunately it is very easily burned out.
Sorry to be negative but this was a bad experience for my friend and it has lowered my opinion of the product and the supplier.
cheers
Hugh
Hornet wind turbines are very good, easy to fit, make tower strong and fit inline fuse,
also fit a dump relay to a battery bank,
And also allot of the designs of the multi blade was first made by windgenerator.org.uk
and later copied by, other USA company’s
The UK dealer is very good to deal with,
How have you got on with the hornet? Is the “Affordability” worth it and how may blades did you get. Also, I have a low wind speed site, is more blades better for earlier start up?
the hornet belongs to a neighbour. It is still working. I think this is due to the furling tail since it would have been destroyed by the gales without that. It has 8 blades. Having more blades gives more torque for an early start but usually means less speed once it is turning so I am not sure how big an advantage it would be. The logic of having so many very short blades is hard to understand when you can get a lot more torque and power using just 3 longer blades.
cheers
Hugh
Hi Hugh…its all a question of balance…the tip speed it the key. The Thermodyne converted alternators require rpm to make power. You are right a big 3 blade will generate huge torque…but at a lower speed. The Termodyne latest blades 880mm KT Pantera blades with a squared off tip..promote everything tip speed. The trick with these turbines is not to get an early stall….so you need a load curve that allows the shaft speed to get over 200 rpm or more…beyond that you can start to load the turbine. Many installations of this turbine just start spinning up then stall….as they are subject to too much load. 400 to 450w in a moderate wind for a 28 magnet dual pma is very realistic….and actually quite good. There are also many reports that these turbines can withstand 80mph gales with no curling or damage…
Hi Richard,
To get the maximum swept area and maximum rpm you need to have a high tip-speed-ratio. If you study blade design you will find that this means fewer blades (and also the correct blade angle etc). By reducing the number of blades you can achieve a trade off giving larger diameter. So if you go for example from five blades to three then you will run fast in a given windspeed and you can use a larger diameter to achieve the same rpm.
When I started out (in the 1970s) I used two blades for this reason and they ran very fast. Nowadays I use 3 because they run more smoothly. I see no advantage to using five blades. I use low speed alternators that are specially designed for wind so they start up easily and have good efficiency at low power. They are also heavy enough to cope with high power.
As for handling high winds without damage I know a guy in the western isles who tried out a Hornet recently and it only lasted a couple of days. Your man Les was unhelpful and abusive. The design is really too lightweight to deliver the ridiculous outputs it claims to be capable of and unfortunately it is very easily burned out.
Sorry to be negative but this was a bad experience for my friend and it has lowered my opinion of the product and the supplier.
cheers
Hugh
Hornet wind turbines are very good, easy to fit, make tower strong and fit inline fuse,
also fit a dump relay to a battery bank,
And also allot of the designs of the multi blade was first made by windgenerator.org.uk
and later copied by, other USA company’s
The UK dealer is very good to deal with,
How have you got on with the hornet? Is the “Affordability” worth it and how may blades did you get. Also, I have a low wind speed site, is more blades better for earlier start up?
hi Mark,
the hornet belongs to a neighbour. It is still working. I think this is due to the furling tail since it would have been destroyed by the gales without that. It has 8 blades. Having more blades gives more torque for an early start but usually means less speed once it is turning so I am not sure how big an advantage it would be. The logic of having so many very short blades is hard to understand when you can get a lot more torque and power using just 3 longer blades.
cheers
Hugh