windy narrow ridge for tower

[Timbersawz]

First I want to thank you guys for giving me a few to many days worth of searching and following some epic threads, my head hurts. I wouldnt have believed it was possible to put up the height of towers that some of you guys have managed, I just wish I lived closer to do a workshop as im based in New Zealand. I have done alot of maths, kicked around scrapyards and the net for everything from pipes to batteries (brought a few of them already) and you have generally been a bad influence.

We are looking at building on a windy ridgeline off grid. I have a million things to do. I have been cutting a drive using my skidder, working out everything from rain catchment to concrete coverage.

Where im looking at erecting a turbine is on a narrow ridge which is about 10 yards wide along the top and on either side for every 10 yards horizonal it drops 7 vertically. The ridge runs at about 30 degrees heading. The site for the turbine is not the top of the ridgeline overall, the ridge continues to climb gradually at a 30 degree heading with 10 foot vertical gain for every 100 feet horizontal. after about 300 feet at that heading it  roughly levels for a further 100 feet then drops away.

 Majority of the winds in the area are directly from the north at 46% with the south accounting for 24% the NE at 8%, SE 5%, SW 4% NW 4%. Average wind speed at the local airport is 15mph. and the highest recorded was 154mph (in the 60's). Last year across the valley my mates place recorded a series of 90mph gusts although is questionable that the winds may have been higher. (we are forecast to get 80mph plus gusts today)
I have my own weather station up there, well I have had 2 mounted on a 15 foot pole. They have been broken by the winds a couple times each and I do question there accuracy of readings.

 Due to the wind speed im looking at using a 3.5kw windspot with 13.4 foot rotor diameter weighing 407lbs. they are able to take abuse and are available here. Im not confident I could build something dependable and survivable myself although I would like to try after seeing some of the beautiful and epic size rotors many of you have done.


The issue that im trying to work around is the fact that it seems the ridge would be to narrow to guy a very tall tower in 4 directions (especially considering the prevailing winds) yet its unlikely to have good enough access for a crane or simular unit or concrete trucks to easily put up a fixed tower.

One thought I had was to (somehow) get a 20ft shipping container up there, anchor and reinforce it  and install a 35-40 foot tower made from 10 inch pipe with .37 walls which hinges off the tope edge of the roof so when down the pole lies across the roof with 8 feet of pole being cantilevered past the pivot/hinge, but when erected the bottom 8 feet of the pole braces to the outside back wall of the container or to an anchor in the ground.

Is this at all feasible or am i missing something? Or are there other suggestions? excuse my conversions to imperial measurements, not always easy to do

[Mary B]

I have tilted up 40 foot free standing towers with the bucket of a tractor. Just get underneath it and keep moving forward with the bucket raised. Bucket slides along the tower and pushes it up. You could build a permanent gin pole behind the tower to raise it, a 40 foot tower isn't that tall. Question is what do you have available for materials, and what are your engineering skills to design a tower to take that load when raising and to take the thrust load of the wind turbine at 100mph. I had one of these towers with a pretty heavy load on it, 150 pounds total. Scary going up because everything creaks a lot but it works well



If you beefed up that design to handle your load requirements... it is a US tower MA-40. Manual can be found online.

[Timbersawz]

Thanks Mary B, im sure being under that on a tractor would have been a bit nerve tightening.

I have a light mig and inverter arc welder, but a mate of mines got his 7/11 ticket for welding if needed. I okay with working with steel, I make and modify various things but nothing to advanced. made trailers etc. Im not good at it, but I can do it! I also have a gasoline powered cement mixer, a baby one, but it gives me options.

I have pretty good options for lifting gear, my skidder has twin 3500kgs winches, I own pairs of grip hoists rated at 5000kgs (11000lbs) and 1600kgs. I have a harbegger chainsaw winch thats good for 1600kgs and a few capstan winches and blocks etc. A good mate has a 7t digger with various augers, he specialises in putting in ground anchors and drilling but its the lack of space on the ridge for the guys that has me head scratching and having to think about a design without guys.

[gww]

I find pictures hard to post here cause you need to reduce the picture data to below 100 kb.  Can you post a pickture or two of the site?
gww

[Timbersawz]

I find pictures hard to post here cause you need to reduce the picture data to below 100 kb.  Can you post a pickture or two of the site?
gww

unfortunately I dont have any useful pics of that part of the site, but this is a picuture of the ridgeline from across the gully looking at 330 degrees from about 22000 feet away. From the old poles there are old cuts in the bush heading up the hill. the site is likely to be where the ridge starts to become horizontal and the last noon sun is lighting up the very top edge

it does give some idea how steep the ground is below the ridgeline

I will get some pics next time im up there.

The large hill behind is some 1000 feet further north of the site.




Another image, my little skidder, with busted hydraulic line stuck until I can hike more tools up.

[thirteen]

The soil looks lik every little rock. I would look closely at the side of the ridge there maybe an area that could sluff off and cause problems later after you have the tower up. Your tower hiight will be a big question. To work on it I would biuld a suppott stand up the ridge making it easier to raise and lower. You might haver a long guy cable on the dominate wind direction  but the othe three might be able to be put on the ridge over the sides. Best of luck . Side note how high will it have to be. You might put some flags on a ballon string and send it up to see where the wind is going at a certain hieght.Ten feet may make a difference. It may help to see if you are in any flight path. Pilots seem to get upset when they fly into unknown wires. Or tell anyone who has planes near you about your tower as a nice guy thing. Just a few thoughts. 13

[Mary B]

a 40 foot tower should have guys spaced 32 feet out but reduced guying can be used if you beef up the tower and the guy lines, you can go to 60% of tower height so 24 feet. if the sides aren't to steep(hard to tell from a picture just set the guys down the slope a ways. You can 3 way guy and tilt a tower up, just a bit tricky. I have done it many times.so that could fit the guys close to or on top of the ridge for the most part.

Doesn't look like a lot of trees to get over so a 30 foot tower would really reduce the guy footprint, at normal 80% of tower height 24 feet, reduced at 60% 18 feet. If you can locate it Rohn 45 or 55 tower would work, maybe rohn 25 even(I would need to find top loading specs for tilting up). Rohn ships towers worldwide so you might find some used from a cell phone installer.

[Timbersawz]

The soil looks lik every little rock. I would look closely at the side of the ridge there maybe an area that could sluff off and cause problems later after you have the tower up. Your tower hiight will be a big question. To work on it I would biuld a suppott stand up the ridge making it easier to raise and lower. You might haver a long guy cable on the dominate wind direction  but the othe three might be able to be put on the ridge over the sides. Best of luck . Side note how high will it have to be. You might put some flags on a ballon string and send it up to see where the wind is going at a certain hieght.Ten feet may make a difference. It may help to see if you are in any flight path. Pilots seem to get upset when they fly into unknown wires. Or tell anyone who has planes near you about your tower as a nice guy thing. Just a few thoughts. 13

The soil is mostly clay with a few areas of rotten rock. Its very slippery, the skidder has nearly slid off the side of the ridge all to often, thankfully the winches are able to drag its butt from the edge.

With the steepness of the ridge, I doubt the guys can be run downhill partly due to the angle but mostly due to the difficulty of physically putting anchors into ground that steep. its crumbly ground and very hard to access. although maybe theres a way.....you have me thinking.

Im thinking that the tower will need to be between 30 and 40 feet, although without decent guying, im going to have to work on that. Might try doing tests using multiple wind meters at different heights to test the wind a bit closer, and see how short a tower I can get away with. the trees up there are bascially just scrub, its to windy for anything else to survive. Not much grows over 8 feet up there.

Rohn towers are not common in these parts, but im looking! Next time im up ther I will take photos and take better measurements

[gww]

One thing to consider.  That is a heavy turbine and thirteen foot rotor is a lot of force.  If you lean the tower against a building, It may create different stresses on the tower then desired.  I have did so twice and both times within a year the poles were bent in two.  I know that 1&1/2 inche pole was to small but the turbine was only 8' above the building.  The biggest turbine I have flew is 8'.  I have two towers now,  one is 80' and one is 40'.  Both are on compleatly flat ground.  40 foot one is a utility pole and is only guyed at the top.  The 80' one has guys every 20' and is 4" outside round pipe.  Both are raised with gen poles about 1/3rd the lenght of the towers.  You have very rough ground to work with.  Also from the looks of it you may have to run some distance to where you plan on using the power.  The cost of wire to control voltage drop may need to be considered depending on system voltage. 

Have to looked at the forum host (projects) on this web site?  Are you talking of placing the tower on the very top or the ridge line (flat area) or some where only near the top?

Man that is some rough ground.
gww

[Timbersawz]

One thing to consider.  That is a heavy turbine and thirteen foot rotor is a lot of force.  If you lean the tower against a building, It may create different stresses on the tower then desired.  I have did so twice and both times within a year the poles were bent in two.  I know that 1&1/2 inche pole was to small but the turbine was only 8' above the building.  The biggest turbine I have flew is 8'.  I have two towers now,  one is 80' and one is 40'.  Both are on compleatly flat ground.  40 foot one is a utility pole and is only guyed at the top.  The 80' one has guys every 20' and is 4" outside round pipe.  Both are raised with gen poles about 1/3rd the lenght of the towers.  You have very rough ground to work with.  Also from the looks of it you may have to run some distance to where you plan on using the power.  The cost of wire to control voltage drop may need to be considered depending on system voltage. 

Have to looked at the forum host (projects) on this web site?  Are you talking of placing the tower on the very top or the ridge line (flat area) or some where only near the top?

Man that is some rough ground.


gww

Excellent points, thanks!

I guess im going to have to find out what kind of thickness and diameter of steel would take the force unguided. I think I worked out a few months ago using a theorem I found that the tower has to withstand up to 4000kgs forces with 130mph + winds.(okay I got my brother to do it, im terrible with maths) Darn I will have to see if I still have that bit of paper hanging around and recheck.

If it wasnt so rough and inaccessible and generally a PITA to attempt to build on, we couldnt have afforded it!

 The ridge runs at about 30 degrees heading. The site for the turbine is not the top of the ridgeline overall, the ridge continues to climb gradually at a 30 degree heading with 10 foot vertical gain for every 100 feet horizontal. after about 300 feet at that heading it  roughly levels for a further 100 feet then drops away.
 Where the ridge levels and widens some 300 feet away, is where the house is going to be, and there isnt much spare room around there! But thats how far we will have to run the power cable to the turbine.

The other issue that slipped my mind to mention is that running parallel to to the ridgeline (on the opposite side to what the photo shows) about 15 feet down is where the driveway will run through. At this point its a rough track and I have to cut it a few more feet down. My tallest truck is about 130 inches high so running  guy over the tops not likely. But since theres access from that side maybe an anchor pole could be installed.......more homework I feel.

heres a pic of the track and that ridge side, its not very helpful but better than my discription! you can see remains of a fence on the LHS that runs along the length of ridge and is placed right before the ground drops away. (Our 3 year old has a thing for collecting sticks)





 

[gww]

Three hundred feet wouldn't be that bad if you go with a 48 volt system maby. 

I went 200 feet with my solar and to keep the drop below 3 % at 90 volts I used 4/0 aluminum direct burial wire and used a trencher.   

100 feet ridge gives you a bit of ground to work with on such a short tower.  If the turbine wasn't so big,  clay holds guy anchors very well. 

If you were building a turbine, member Chris olsen says he gets the kind of power you are looking for with his turbines and an mppt charge controller which might allow higher voltages and smaller wire. 

I never do math but find the utility pole for short towers to be strong enough that I only guyed it at the top.  I would think it you buried something heavy enough for the guy anchor and used heavy enough guy wire that a 15 foot distance from a 40 foot tower woud be enough.  expecially if you used 6 inch or more pipe or maby a utility pole.

 Wait for people that are smarter then me comment before trying though.  Just cause I would try something doesn't mean it would work as I have tore up plenty with my expermints.
Good luck
gww