dg wrote:
I noticed a wind turbine in B&Q, and it is nothing more than a motor,
on a pole with a propellor and some box of electronics.

Its a bit more than that, though not a huge amount. The motor has to be
a type that offers near zero starting torque, which rules most motors
out. It also has to be one where low speed can produce the wanted
output, which again rules many out. It also should preferably be PM
field to avoid losses, though there are some excited field gens around.


Standard PM field motors dont start effortlessly, so no off the shelf
motor satisfies all the requirements. However if you want to make a
no-cost compromise design, a car alternator is a fairly good choice.
The controllable field makes it more efficient at higher speeds, as you
can reduce excitation to reduce V_out. The downside is at low speeds a
significant amount of your output is simply supplying the field coils.


How are these valued at over £1500

theyre priced at 1500, the miniscule sales volume shows that theyre not
valued at 1500. The price comes from business costs, if you only sell
10 units a year you have to divide your total biz costs by 10 and add
that to the price of each unit sold.


when it seems it can be made for a
fraction of that? How much would the parts be?

£50 should cover it. Car alternator, wood or metal for the prop, steel
pole, brake drum for the rotating mount, some control electronics,
tailfin assembly, overspeed brake, service brake, and rotatable power
conductor. There are lots of plans around for making them from scrap.


NT