Introduction from a new member

[Chris Bibby]

Hi all,
Based in the midlands in the UK and currently building a VAWT to the Benesh profile (similar to savonius but not as clumsy!).
Dimensions are two 1m tall turbines connected end to end (with 90 degree rotation difference) with 450mm diameter blades.
Benesh to be mounted on side wall of my house (gets prevailing wind) with the trailing edge sheltered by the side of the house.
Planning to gear at about 1 to 4 and connect up to a commercial 24V 1.1kw generator (26W at 258rpm / 1142W at 490rpm).
Build so far is bearings (3 pillow bearings (ends and one in the middle)), 3 axles to match the bearings and take 10mm threaded bar that will form the main axle for the turbine, 6 disks with the benesh profile routed into them (top / bottom and middle of each turbine).
Still to go - make the top disk into a gear by adding larger disk top and bottom of it to act as belt guide / paint the wooden disks to weatherproof / source the material for the blades (planning to use the plastic sheets that estate agents boards are made of) / make the mounting frame / stick it all together! so lots realy.

Interested in any advice anyone can give and anyone who has actualy manged to get a savonius or benesh to work, as not found anyone yet!

Just found this forum today and hoping it is not as ridiculously controled as one of the others I was using (had posts deleted / moved / unhelpful comments etc etc), and as for the whole 'newbie' category (excuse the rant but it wound me up).

[Paul Bailey]

Hi Chris . Welcome to the group. Love to see the pics of your Vawt. lots of good stuff in this group ,just keep digging thru the posts. Lots of great ideas ,experiments, outside the box thinking to save energy or generate your own on all fronts. Paul:) Ontario ,Canada

[Mark Parsons]

Greetings Chris,

Welcome to the group. I am a fellow VAWT builder. You can see my macine at http://www.greenpowertalk.org/showthread.php?t=960

This machine has been flying at my cottage since April 2007. No maintenance issues other than some added bracing after a couple of good wind storms.

My blades are each 4' (1.2m) tall x 2 blades = 8' (2.4m) tall. The diameter of my machine is 34" (0.86m). I have only seen about 100 Watts from my machine during an unmeasured gust. I assume there has been higher output during wind storms in my absence. What are your wind speeds to lead you to use a 1.1kW generator? Perhaps you are planning on building a larger model and using the same generator?

Got any photos of your work in progress?

Regards,
Mark

[Chris Bibby]

Mark,

Similar idea, few thoughts I had to improve the efficiency of the benesh (spent ages going through his various patents), please chip in if i am off the mark with these thoughts:
Seems like the optimised profile he came up with is quite a bit better than a savonius and i believe the blade gap adds to that.
Mounting against a wall chanels the wind into one direction and acts to magnify the effect.
Covering half the blade with the wall reduces the drag effect.
Using the biggest possible diameter for the gears (the outer disk profile) gives the lowest gearing loss.

I have gone for the 1.1kw generator for no better reason than it offers the most power for the lowest rpm i can find with a choice of 4 different ones from Futurenergy (12 / 24 / 36 or 48V). I have made the whole thing modular, so if it hasen't got enough power I can screw another one on the bottom to make it 3m tall, but as I said, no idea if it will work or not, if it dosen't i will try something else with the generator, but i hope it will work as i do like the design of this turbine.

Should be good to compare my one with your's when I get it up on the wall, could be the first real comparison I have been able to find. Will keep you updated.

Haven't worked out how to post photos yet...

Regards
Chris

[Mark Parsons]

Similar idea, few thoughts I had to improve the efficiency of the benesh (spent ages going through his various patents), please chip in if i am off the mark with these thoughts:
Seems like the optimised profile he came up with is quite a bit better than a savonius and i believe the blade gap adds to that.
Mounting against a wall chanels the wind into one direction and acts to magnify the effect.
Covering half the blade with the wall reduces the drag effect.
Using the biggest possible diameter for the gears (the outer disk profile) gives the lowest gearing loss.


Greetings Chris,

Have you reviewed this work? - http://www.energy.ca.gov/2005publications/CEC-500-2005-084/CEC-500-2005-084.PDF
He comes up with a Savonius CFD optimized blade design that has better Cp than Benesh. Your comments?

I agree with the wall mount reducing drag. Wall mount also reduces wind direction options. Turbulence is also increased. I considered putting 4'x8' plywood sheet fixed deflectors off 3 compass rose points around my machine and measuring output for any benefit. I haven't done this yet. Will you be able to move your machine from wall mount to free standing location to measure output to determine if wall mount is a benefit?

I use the manage attachments (paperclip) function to insert photos when creating posts.

Regards,
Mark

[Chris Bibby]

Mark,

I had reviewed the document you attached in my data trawl, the profile they described is (i think) the same as benesh came up with in a later patent, that is the one i am using, he describes how to create the profile which is very useful.
In another patent benesh also describes optimising that design by use of a blocking device (part of where the idea to mount with half obscured by the wall came from), and also then describes further optimisation by mounting a wing to the outer edge of the turbine to speed the air past the blade, i am holding this bit in reserve if i need to speed it up as it is quite complex.
I can't post a link at the moment as i am in belgium, but when i get back i will attach a photo of my prototype.
When i wall mount it i will be stuck with that position, i spent some time walking around with a cane that had a bag stuck on the end to measure wind direction and strength (very intricate as you can imagine!) and i was surprised by the increased strength i was able to get by using the wall, i hope by mounting in the way i intend that if the wind is in completely the wrong direction i will still catch it with the other side of the house, but with less efficiency. I hope that the turbulance etc is much less of an issue with this type of vawt compared to a hawt.
regards
chris