Turbines on the bean canes

Absolute beginner-level front-page-of-google answers to the questions I asked myself, as an absolute beginner, when I first started thinking about using wind to power some aspects of yurt life:

Can people just buy turbines ready to power consumer goods?

Well, the first page of Google for ‘home wind turbine UK’ was all advertising and domains that were clearly set up to be shops while passing as independent advice blogs, so I’m going to call that a yes. This one feels like an actual advice blog: https://www.homebuilding.co.uk/wind-turbines-guide/ and good lord no I don’t call twenty grand a consumer purchase, get stuffed! I was picturing more, like, a whirligig on a telescopic stick with a thingy to convert it to mains-like current at the bottom with a mains plug out. It feels like that would total under £100. I must be missing something about how complicated the conversion parts are.

Name the parts, from blade to output.

  • Moving fluid (could be wind, chimney output, falling water, river water)
  • Hits a curved surface that moves out of the way of the fluid because it is attached to
  • An axle mounted loosely enough on
  • Some sort of framework which holds a
  • Coil in which a current is induced by the movement of the axle, which connects outwards by two wires to form a
  • potential difference in a circuit which you can then use for whatever.

How do you convert AC to DC?

For the moment, the answer is ‘you buy a rectifier’.

When do you want DC?

This page is charming: https://engineering.mit.edu/engage/ask-an-engineer/whats-the-difference-between-ac-and-dc/
Anything I’m powering by USB is using DC. To charge a battery, I want DC.
Note to self: USB power is in the single digits of watts.

How do you convert DC to AC?

For the moment, the answer is ‘you buy an inverter’.

When do you want AC?

AC is easier to transform the voltage up or down, and high voltages are more efficient over distance. It’s looking like I only want AC if I’m going to connect a three pin mains-looking socket out, which I’m beginning to think I don’t – I’m not hoping to power the PC or the fridge off turbines, only LED fairy lights and power banks.

Find a homemade turbine tutorial to follow.

I read a dozen, but they’re all using very heavy plastic or metal pipe for the blades and the gantry. I pictured more, you know, halved plastic cola bottles hot-glued between two old CDs. I would rather worry about the turbine lifting off and blowing across the yard than worry about the turbine falling over and denting the path. And they all end with ‘connect it to a generator you bought’ which, yes, love, that’s the part I was hoping you’d… oh, never mind.

It seems that the type of turbine I visualised at the top of the bean canes is called a vertical axis wind turbine. The weight of it presses down through the axle.

Dr DrunkenDwarf, what haven’t I thought of, and what have I underestimated?

Effectively you’ve got the idea. All that’s required to generate power is a magnet spinning within a coil. I had a student once build a little turbine he could blow on about 4 inches tall out of lego, it was successful, in that it produced a blip on an oscilliscope. The problem is generating enough power to be usable. The more useful you want the turbine to be, the bigger the coil needs to be (and by extension the magnet) and the faster the magnet needs to spin. To increase eaither of these you need more force from the wind, so, as big a turbine blade as possible. While you can do it with coke bottles and a CD, I doubt it would power a single fairy light reliably. Quadcopter blades might be an interesting idea, they’re designed perfectly for air movement and they’re cheap because they break so easily in a drone crash.

The most important part is what to DO with the energy once you’re generating enough to be usable. Obviously we’re not going to feed it into a generator, but into our central energy store may be worthwhile. If we do any other type of renewable energy like solar, we will need an energy store (a stack of a few 12v lead acid batteries), and this will require a ‘charge controller‘ to clean the energy coming in from say, solar panels, and make sure it can efficiently and safely charge the batteries. Adding homemade turbines to this charge controller cleans the power frequency for us, and puts the energy in a convenient central space, giving us nice clean 12V DC which you can use to charge your phone and blog more!

Dr DrunkenDwarf

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