Print PDF
Favorite
Email
Step 6Blades
Personally, I am not a very good carpenter. My woodworking skills are pretty basic and making your own blades requires some pretty good attention to detail. So I decided to save myself the time and effort of making blades and just buy a ready made set.
There are lots of guides and tutorials for blade-making online. Hugh Piggot even offers a nice table of useful figures for different blade diameters in Windpower Workshop.
Now, there is a lot to consider when buying blades. First and foremost, consider the power you are taking from the wind. This is based mostly on the diameter of your wind turbine blades. A wind turbine steals energy from the wind by slowing it down as it passes through the blades and makes the rotor turn. This is all laid out mathematically by the Betz' Limit. These calculations show the maximum amount of energy that is possible to be extracted from the wind, though they do not account for losses in generator efficiency... they also assume that you have infinite blades which all have no drag, and if you can hook me up with some of that, I'd be very interested :).
It isn't so simple as bigger blades equals more power, though! No, no, no. What is most important is that you match the blades to your generator. Generators are designed to start producing usable electricity (the voltage you want) at a certain RPM. This is where the Tip Speed Ratio comes in. Basically, you want to have blades that provide that RPM at the most typical wind speed you'll be experiencing. Sound complicated? It is, kind of. Usually the Tip Speed Ratio (TSR) is an indicator of efficiency, but beware of websites claiming abnormally high TSR's! I would recommend using it as a rule of thumb.
There really is a lot to blade making as well as blade theory, but that should give you some good general insight into what you're trying to accomplish. As for me, I bought my blades from a website called Magnet4less (no 's'). At first I actually bought the wrong size blades thinking I could get away with a bigger diameter, but alas, physics wins again (Some of the pictures may have these first blades in them). I eventually folded and bought the 6.8 ft. diameter blades. However, I would NOT recommend buying these blades again. They have terrible reviews from wind power people around the country and with my personal experience they look like the angle of attack just isn't enough to spin up high RPMs.
This is the part where I suggest another retailer but, to tell you the truth, I really don't know of one. Homebrew wind turbines enthusiasts seem to be mostly (but I could be corrected) out of luck for high quality universal blades with different diameters. I suppose you could use a pair of replacement blades from another commercial turbine assuming they are to your needs.
Other references!
For making wooden blades:
http://otherpower.com/blades.html
http://www.thebackshed.com/Windmill/PropellerBlades.asp
http://www.mindchallenger.com/wind/wgpage15.html
If you're interested in making blades out of PVC, I'd recommend using Google for instructions. I don't recommend PVC blades for a turbine like mine, though.
There are lots of guides and tutorials for blade-making online. Hugh Piggot even offers a nice table of useful figures for different blade diameters in Windpower Workshop.
Now, there is a lot to consider when buying blades. First and foremost, consider the power you are taking from the wind. This is based mostly on the diameter of your wind turbine blades. A wind turbine steals energy from the wind by slowing it down as it passes through the blades and makes the rotor turn. This is all laid out mathematically by the Betz' Limit. These calculations show the maximum amount of energy that is possible to be extracted from the wind, though they do not account for losses in generator efficiency... they also assume that you have infinite blades which all have no drag, and if you can hook me up with some of that, I'd be very interested :).
It isn't so simple as bigger blades equals more power, though! No, no, no. What is most important is that you match the blades to your generator. Generators are designed to start producing usable electricity (the voltage you want) at a certain RPM. This is where the Tip Speed Ratio comes in. Basically, you want to have blades that provide that RPM at the most typical wind speed you'll be experiencing. Sound complicated? It is, kind of. Usually the Tip Speed Ratio (TSR) is an indicator of efficiency, but beware of websites claiming abnormally high TSR's! I would recommend using it as a rule of thumb.
There really is a lot to blade making as well as blade theory, but that should give you some good general insight into what you're trying to accomplish. As for me, I bought my blades from a website called Magnet4less (no 's'). At first I actually bought the wrong size blades thinking I could get away with a bigger diameter, but alas, physics wins again (Some of the pictures may have these first blades in them). I eventually folded and bought the 6.8 ft. diameter blades. However, I would NOT recommend buying these blades again. They have terrible reviews from wind power people around the country and with my personal experience they look like the angle of attack just isn't enough to spin up high RPMs.
This is the part where I suggest another retailer but, to tell you the truth, I really don't know of one. Homebrew wind turbines enthusiasts seem to be mostly (but I could be corrected) out of luck for high quality universal blades with different diameters. I suppose you could use a pair of replacement blades from another commercial turbine assuming they are to your needs.
Other references!
For making wooden blades:
http://otherpower.com/blades.html
http://www.thebackshed.com/Windmill/PropellerBlades.asp
http://www.mindchallenger.com/wind/wgpage15.html
If you're interested in making blades out of PVC, I'd recommend using Google for instructions. I don't recommend PVC blades for a turbine like mine, though.
| « Previous Step | Download PDFView All Steps | Next Step » |
 |
Add Comment
|
