 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Windmills : low windspeed startup
| Author | Message | ||||
GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
I had the opportunity of seeing my old AxFx windmill start turning, from being stopped tonight. My DAVIS weather station anemometer would just start to turn and then slow down and stop. The windspeed was between 0 and 1 kph. My windmill started to turn and was spinning quite freely at about 10rpm. Not enough to make useful power, but still it was trying. BTW the 10min windspeed was 0kph, and the recorded maximum was 1kph in that interval. The bearings have been in service for 15 years, so there is still some service in them. I run a wet type, moly bicycle chain lubricant, instead of grease. Just thought readers would be interested in what is possible with a home made mill. The lack of iron, high precision bearings, and the low mass, and low inertia contribute to make it possible. Gordon. become more energy aware |
||||
Perry Senior Member Joined: 19/11/2009 Location: Posts: 190 |
I am always perplexed how some vendors publish wind speeds that a mill starts turning at and then a cut in wind speed at some rpm above it. The VAWT guys are notorious for this. As if it matters that it turns at low wind speed. All this is doing is putting more cycles on the bearings and producing no power. I would prefer that the mill not really turn until it is ready to make power. Big turbines aren't allowed to turn until there is ample windspeed to reach cut in and above as a way to extend the life of the machine. This is just a random thought and not a flame of your post or all the good work that you share here Gordon. Perry |
||||
fillm Guru  Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Hi Perry , My Ax Fx does exactly the same as Gordons , if there is even a sniff of wind it is turning while the F&P dual needs 8 ~ 9 klm to get it going , but the point here is when that little puff of breeze comes through the Ax is producing power at almost that instant , when the F&P does reach cut in , and only if the puff of wind allows it to reach cut in the Ax has been making power for the whole time , and most of the times the F&P doesn't get there and stops again . I live in a low wind area and these little differences can add up to a 50 ~ 100 W/hr difference in a day with small turbines . If I had big ones then I would not want them to turn unless they were making profit , the logistics and costs involved to replace wearing parts would dictate this . As for bearing cycles , with slow turning well lubricated small bearings it is neither here or there in regards to bearing life and most will change their bearings well before their service life has been reached , as the cost is minimal . Finnaly worked out your avatar pic , standing on the nose cone of one of those big boys must be a real buzz , you must have wealth of info and pics that I and others on this site would love to here about and see , and I for one am always interested in your profesional point of view . PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
||||
| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Most big turbines are induction motor type generators. These need to operate at a certain speed to generate, otherwise they are motors. The fact that they have to turn them OFF in low winds is related to them operating as a motor and consuming power that they are supposed to be providing. Servicing is also a problem though and reducing the run time will extend the time between service. I would imagine that bearings would last at least as long as the blades though. Lubrication of the turbine would be part of a sheduled service, and would not require disassembly. The losses in the drivetrain of the large machines must equate to approx 5% of the output power. This would be considerable for a MW mill, so it would be better to keep the mill OFF until there is enough wind to achieve breakeven. We don't see these issues on a smaller windmill. Gordon. become more energy aware |
||||
| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
I have just run the specs for my 2m windmill through Alton's online wind calculator. It seems that the wind energy available to start my windmill is around 0.5W I know that following a service, the startup energy needed is up to 4W, so bearing resistance is pretty low. In this case 1/8 of the drag caused by oil. This to me is a good indication that it is time for a windmill service. Gordon. become more energy aware |
||||
 Print this page |
 |
The Back Shed's forum code is written, and hosted, in Australia. | © JAQ Software 2025 |
