Tuesday, April 29, 2008

Motor madness

Bay-area buddy Simon Quellen Field (and well known fiddler of magnetic things) suggested that motors could turn the sails, instead of the 2:1 gear.  Of course they still turn at the same speed, in accordance with the 2:1 ratio - but no pulleys, chains or turning shafts.

As the main generator is making electricity, there is ample to power two smaller ones to turn the sails.  The two smaller motors would only be under modest load as there is little torque due to the sails being symmetrical around an axis. 

Its even possible that the whole contraption could recover adequately after the wind (or fluid flow) drops to zero.  As there is bound to be some movement causing a random rotation, to create some modest electricity to allow the sails to adjust to their optimal positions.

This would be the case even if the wind changed direction.

It may be that some local battery, capacitor or fly-wheel storage would be needed.  Or (or all things) a solar powered battery could be modestly sized.

Very clever Simon.

Friday, April 25, 2008

US Farming

I've just finished reading "Omnivore's Dilemma".  It's highly recommended.   There's a farmer Joel  Salatin, who is bucking the industrial agriculture trend.  His farm is not the main feature of the book, but its one of many narratives that stay with you.

I wonder how cows would react to a grid of  VAWTs above them.  They wouldn't mind the guy ropes, but would the rotating turbines disturb them?  You'd need transparent (plastic) sails of course so that the grass would continue to grow at full speed. 

Plowed fields couldn't be used of course as farm machinery and guy-ropes are incompatible.

Alternate Rig

In purple, a different rig that would allow the fixing point to move as tides rise and fall. It's shown as a circle, but it would more likely be a custom curve. Again under pressure from the flow the orange roller would find the right place on the curve to keep the turbine perfectly vertical.

Another side view

Given the contraption is pushed 'down stream' the tethering cables/ropes/etc (orange) could flexible apart from a bar (black, center) keeping them apart.

Wednesday, April 23, 2008

Side view of the underwater VAWT.

OK, so the sails are a different angle to previous pictures.  They are both reaching, but in different directions.  The floatation/buoy thing is visible breaking the (crude representation of) water surface.  The counter weight at the bottom is not resting on the sea/estuary/river/lake/lough bed.  In this design there is only one cable/rope/cord preventing the thing from floating downstream.  Also shown is a simple squared rig, that sets the direction of the contraption, and is a fixing to the cable/rope/cord/etc.

Tuesday, April 22, 2008

Underwater string of turbines.

I emailed José Antonio Pérez in Spain, congratulating him on the lego turbine he made and could drive with a hair drier. Hi José!

Meanwhile a turbine was installed in Northern Ireland to take advantage of a huge tidal flow ..

It's a classic design, that required a floating crane to be borrowed from Norway to install. The company website is http://www.seageneration.co.uk/ but search in Google for 'SeaGen Strangford Lough' for other articles starting in 2007 (it took a lot of planning to install).

Using the VAWT design, you could have a much lighter setup. It could float for one, and be anchored upstream using two tethered lines..

Illustrated are three VAWTs. A Buoy keeps it afloat, with a counter weight at the bottom keep it the right way up. There are two cables to anchor it upstream. They might have to be stays to prevent it fowling the blades, because at each change of tide, the contraption is going to relocate to the a new position slowly. This does not need a crane from Norway to install. Indeed it may well be easier to clean the inevitable lifeforms that attach themselves overtime, by floating it to the surface (still tethered, but now flat to the surface).

Whether a river or a tidal flow, the current is going to be strongest in the center of the channel. If not in a channel, then it doesn't really matter about the position of the blades to take advantage of greatest flow.

Unlike the the same VAWT design for wind farm, the device needs no constant orientation to the flow - underwater the tide flows in only two directions, and the VAWT will tune to that automatically.

Please forgive the crude graphical representation of a river bed / water etc.

Saturday, April 5, 2008

and another youtube video

it appears to be called a butler windmill

video of the same VAWT design

Someone else made one out of lego.  This is the first time i've seen the design on the internet

Nice work!

Turbines on the African Savanna, easy assembly

Two men, one flat bed truck, 5 windmills in one day. Well maybe ignoring the generator. The key here is that the support for the central spindle is relatively simple - just a plate on the solid ground, with spikes banged through. The windmills/turbines are erected as a large marquee tent would be - guy ropes, pulleys, strong arms and hopefully no wind.

What differentiates this from standard horizontal axis windmills is the construction.

With horizontal axis wind turbines (HAWT) on hillsides, and the flat, you need a decent foundation (concrete), and potentially a concrete tower to support the weight of the generator with most likely has to be bought in by helicopter. That's costly by anyone's standards.

Don't even mention the the maintenance cost of the HAWT. With this design of VAWT, you could just lower it to the ground with the ropes/cables again. It weight perhaps 1000 times less that the HAWT.

The likelihood is that the VAWT with sail cloth will be less fatal to birds. Potentially less interfering with radio signals too. Both of those are 'in theory'.

Lastly, the HAWT design requires a support more than half the length of the blades to stop them biting the ground. The VAWT design, being guy-roped can go much higher in the same square-footage on the ground.

Next up pictures of the Meccano model from 1991 that actually worked. If I can find the negatives.

Image thanks to Stargirl from flickr and drawingcoach

VAWT on hillside

The wind is coming over the hill towards us/the camera. Two sails are shown. The left one is coming towards us, and the right one is going away. The left adding to rotation, the right momentarily resisting it.

The sails shown in this design are solid.  If they were cloth and between two bars, then the sails could adopt a modest aerofoil shape and add to rotational force in multiple positions. Most notably, positions 4 & 6 in the previous blog entry.  As is with this solid sail design, positions 4, 5, and 6 are effectively drag.

Also, the gearing is shown as a chain and cogs here. That would be impractical due to chain sag. The real one that I built was used bevel gears that are also inefficient.

This illustration shows something that is a couple of hundred yards tall. It will keep going in low wind conditions and still perform in higher winds.

Next up, horizontal vs vertical axis wind turbines. 

Friday, April 4, 2008

My Windmill

I had the idea in 1984 or thereabouts, but did not attempt to patent until 1991.  Its a design for a vertical axis windmill.  The patent failed, because of prior art. Some that art goes back to the 1850's.  I used to have the failed patent application, with 1" of stapled relevant patents. I think I left it at a client site a couple of years ago.

A guy from 'the west country' of the England had been granted a patent on it some years before me.  He's still above and hoping to make some business from it with under-water turbines, but I think the best use is for wind.

How it works - view from above

So this diagram describes one sail and its rotation around a central axis under the influence of wind.  Eight freeze-frame images give a single rotation of the sail around a central axis.

Each sail has to run in two directions - the red dot shows that the sail after one revolution around the axis, would be facing in the other direction.  Meaning there is a 2:1 gear ratio between the (fixed) central spindle and the rotation of the sail around its own axis.

Directions of force are shown via small arrows. It's pretty obvious that all angles to the wind are helping the general rotation apart from frame 5.

You could make each sail as a sheet of sail-cloth between two vertical rods. In the case of my prototype, I made them out of cardboard.  With a sail-cloth form, you could get some aerofoil effect. 

Points of Sailing

Anyone familiar with yachting or dingy sailing will note that sailing positions to the wind guide the design for this turbine.  The novelty (and the thing I tried to patent) was the 2:1 gear ratio.

More in a follow up.