Monday, 18 January 2010

Well, it's over a year since the last update. I've changed quite a few things.
Homemade blades, and the big fibreglass set, have made way for secondhand commercial blades off of Windsave machines, bits that were bought off eBay. I may be paranoid about safety but there you are. These bladesets are about 1.75 m diameter and are designed to run between 100 and 800-900 RPM, apparently. I bought two sets, one for each turbine. The first uses the bicycle hub motor I used before (new bearings though), rated 400W 36V at 400RPM, and the second is a scooter hub motor with a channel for a tyre round it, also 400W 36V but because of the smaller diameter it's at 750 RPM.

I'm flying them temporarily at 12V while I build a new 24V controller (the old 24V controller died somehow and took two new 110Ah 12V leisure batteries from a not-so-bad 25.9V to 7.4V overnight).

The divert load consists of four 7A, 24V diesel glowplugs inserted into 22mm copper piping on a domestic central heating radiator, hung in the garage. Not pressurised - you might just be able to see the open expansion tank at the top.

If it's a roaring success I might make a wooden stand for it and move it into the kitchen. Waste not, want not, and something to point to. Best of all though it's put together as compression-fitted modules which I can reconfigure, so when I finally manage to move house I might be able to preheat my hot water and reduce my bills a bit.

Tuesday, 30 December 2008

Turbine 2 now up and waiting for wind.

This is a smaller one - the first was just too big for my setting.

Each blade is 30 inches of carved wood proofed with linseed oil, the hub was custom made for me from laminated and welded hardened aluminium (same engineering shop, I have confidence in it - they make things like jet engine cradles for Rolls Royce).

Alternator is a brushless permanent magnet electric bicycle hub motor rated at 36V, 400W at 400RPM. I'm running it at 12V so it ought to reach cut-in at around 160 to 180 RPM when the diode drops are taken into consideration - nice and slow.

Yaw bearing is an old Vauxhall Cavalier rear hub which doesn't have a hollow axle, so the wires are external to the tower. To stop them wrapping round the tower, I've limited the yaw to 180 degrees or so with a length of chain.

Now waiting for wind again, but MetCheck says that the next 2 weeks will be 4 or 5 mph winds from the East. C'est la vie.

Monday, 4 August 2008

Have replaced the dead controller with a custom-built OptixElectrics 150A solid state unit and added 400W of extra dump, consisting of 8 in number 50W downlighters hanging off a 1KW 24V inverter.
O Wind, Where Art Thou?

Monday, 23 June 2008

I got wind.
There I was staring glumly out the window at the prop barely turning. Had replaced the 3 x 35A bridges with a 110A 3 phase unit from RS Components; had replaced the Beewind 50A charge controller sensing across one of the 12V batteries with OptixElectrics' 70A one sensing from the same single 12v batt; and there the turbine was, fixed pointing due West but in the wind shadow of my and my neighbours' houses and doing sweet FA.

Wind shifts a few points, turbine comes out of wind shadow, and Bam! away it goes, and then some. This was the first opportunity to see my new CMS Magnetics 10ft 6 inch fibreglass prop in action, and boy, did that sucker move. Hardly any vibration too, fnar fnar.

Genny hits 24V at 220 RPM, didn't stop there, shot on up to 30V - in a 24V configuration too - and amps piled on and on to around 20A. Prop began to make a lot of noise at around 250 to 300RPM - combination of WhumWhumWhum and whistling like telegraph wires in a hurricane. Presumably it was self-stalling at that point.

New controller went Bzzzzzz...Phut, locked on and didn't let go when wind dropped and genny showing 15V.

Tapped box, nothing. Hit box, nothing. With extreme disgust, got ladder, propped against tower, climbed up and used hand on rotating genny body to slow down and stop the prop, strapped prop to tower, then went back down, took out new charge controller and replaced with the Beewind unit. Have shifted back to 12V from 24V, lower cutin, earlier stall - I hope. Will need to double the number of electric radiators I'm using for the dump of course to compensate for halving the volts.

Controller relay still showing continuity even though sitting on bench: looks like relay contacts welded. Ho Hum.

Note to self: Even though it is a proof of concept temporary design, need an emergency brake on the bloody thing.

Saturday, 24 May 2008

On the basis of only changing one thing at a time, have reinstated the fencepost tower and refixed the genny pointing West. It's now using the 10ft 6in prop, and we'll see how that does before thinking about changing to a swivelling mounting. The forecast shows reasonable winds - but from the East, which is typical. However, if I wait long enough.....

Thursday, 15 May 2008

Local engineering shop has done a very good job on the adaptor.
The original fitting (bottom left) is soft alloy, they recreated it in steel, with a big bolt , and counterbored to make a location for the hub prong. There's a transverse hole to take a spring pin (though I might use a bolt instead) to transmit the torque, and the nut at the end is held on with a split pin.
The hub had a tapered hole down the centre and a UNC or UNF thread at the end, they cut the thread off, bored the hole out and fitted a length of steel tube in there with a flat on the prong so it only slides into the adaptor one way.

Wednesday, 14 May 2008

After some gales, I hauled it down for a check and discovered that the 3 wooden blades were all split along their length. Oh dear. So I sent off to CMS Magnetics of Plano, Texas, for a set of their 10ft 6in reinforced fibreglass blades plus hub.

Here are the blades, which all balance at the same point along their length. However, one weighs 3020 grams, another 3042 grams and the heaviest comes in at 3055 grams.

My friendly local engineering shop is making an adaptor to mate the very substantial 3/16 inch steel hub to my 1KW stepper motor. Once I've mounted the blades, I'll see if I have unacceptable vibration when they are spinning. If so, I'll try adding weight to the appropriate blade at the hub end, and if that doesn't work I'll sand down the heavier ones (I need to clean up and sharpen the blunt edges and reshape the tips anyway).