When [brokengun] decided to build a 7 ft diameter wind turbine, he had no idea how to even start, so he did as most of us would do and read some books on the topic. His design criteria was that it would be simple to construct and use as many recycled parts as possible. This wind turbine charges a 12 volt battery which can then be used to power a variety of gadgets.
Although made from recycled components, this isn’t a thrown together wind turbine. A lot of thought went into the design and build. [brokengun] discusses matching the blade size to that of the generator in order to maximize power and efficiency. The design also incorporates a feature that will turn the turbine perpendicular to the wind if the wind-speed gets to high. Doing this prevents the turbine from being damaged by strong gusts.
For the main support/hub assembly, a Volvo 340 strut was used because they are widely available, cheap and known for being long-lasting. The tail boom is made from electrical conduit and it’s length is determined by the size of the main fan rotor. The tail vane is made from steel sheet metal and its surface area is also dependent on the fan rotor size to ensure that the turbine functions properly. The blades are made from wood but instead of making them himself, [brokengun] felt these were worth ponying up some cash. [brokengun] also scored a 30 ft high lattice tower an airport was getting rid of. This worked out great as it’s just the right height for a turbine of this size.
If you like DIY wind turbines, we’ve seen them made from 55 gallon drums, PVC pipe, and many other materials.
The info is a bit inaccurate. There is no such thing as a 12 volt or 24 volt stator, because the voltage produced by a permanent magnet generator is a product of speed and magnetic flux density through the coils. Any coil can be used to generate any voltage by varying the strenght of the magnetic field and rotational speed.
One of the problems with the windmill loading is that your generator power is linearily dependent on your rotor speed, but the available wind power scales at the cube of the wind speed, so you actually have to dynamically increase your load to brake the turbine down, or as done here, use a tail vane to bring it gradually out of the wind to stop it from overspeeding.
Another trick you can do with the knowledge that the generator voltage is dependent on the magnetic flux density through the coils is, that you put the rotor on an axial spring that allows the rotor disc to be pushed closer to the stator by the wind drag of the turbine. As the gap is narrowed, the magnetic flux increases and the generator voltage goes up. When connected to a simple load like a battery, the increase in generator source voltage actually shows up as increase in charging current and the turbine load goes up.
Otherwise, you simply oversize your generator based on your top wind speed and use an electronic limiter or MPPT circuit to draw less power at lower speeds to match the actual power curve of your turbine. All said and done, you should be able to at least double the energy output relative to simply furling the windmill.
Yup. I used to modify a standard alternator to generate 120-150 volts AC. He also should have went to otherpower’s website as they have designs that do exactly what you are talking about.
I suspect someone has hi-jacked ff’s login, as the above comment lacks the usual “sneering” tone and actually adds value to the discussion. B^)
Hey don’t discourage him!
this looks great, but…
why do none of these projects talk about the slip ring system to get the current from the generator down to the ground?
Your slip ring system will make or break a unit like this, I never see that bit covered in any detail, if at all.
The folks at otherpower.com find that a long length of stranded cable tends to work out just fine if you untwist it every few months, hence no need for slip rings.
da fuq I’ve just read?
A 30 foot length of stranded cable going down the center of the tower will in most cases be fine for months or years. Prevailing wind direction changes tend to balance out over time except for particularly turbulent sites.
+1 for the otherpower.com reference.
Of course, that problem could be solved entirely by using a vertical-axis design instead of a horizontal-axis design.
Most vertical axis designs often do not self start and having them furl to prevent over speeding is an issue as well. A slip ring is probably simpler. Of course you could always just have the generator power an magnetron and aim it at a rectifier for wireless transmission.Or use an induction system…
Yes I am kidding.
Probably a typo, that strut is probably from a Volvo 240…. 340’s weren’t sold in North America at all.
pretty clever use of the hub and strut.
When I first read about the “brake drum” construction method, that preceded using disk brake spindle use, I thought I’d use spindle off the rear axle a 3/4 ton pickup. With new bearings and fitted with a metal to metal precision oil seal, it should last forever. Later on Learned that some builders in Canada where use parts of that sort of axle.
So how high will this turbine fit into the wind turbine tower?