My turbine was a x-marine, I no longer have the boat. The claim was it would produce at 15knt, (also the speed it started turning I used it for an anchor watch alarm). At that time it would produce down to 7knt. Remember that wind power increases with the square of wind speed. I believe that the blades were 56" span (dia). Also remember we don't want to anchor our boats in any high wind anyhow for the comfort of the ride.
Low speed wind turbines are in fact better for boat use for the above reason. The problem is having enough power in the wind to make the expenditure worth the money spent. Many of the turbines I saw in my travels hardly produced, but they did produce at lower wind speeds. The other problem is the square area that the turbine configuration takes up.
I was hove to one night with the Pacific current of 4.5knt to this was added the wind current for a total sol (speed over land) reading on my GPS of 8kts. I found myself calculating how far I was from land or obstruction so I knew how long I could sleep before running into trouble. The hull speed of the boat determined that I would have lost ground had I pointed into the wind and gone full bore into it. A sea anchor would have helped little because I needed the effect of the sail forcing the boat over to make sleeping a reality. The fully reefed main sail was sheeted in only enough to keep the sail from luffing. I estimated sail area may have been 4 square yards of windage but the boat was still healed over at about 7deg against 5000 to 6000lbs of lead.
2000w is less than 3hp and the maximum output for the vertical turbine you are looking at, or the one I saw. If your turbine is putting out 2000w you will have to correct for that 3hp push against the hull as well as an equivalent from the surface area of the hull and superstructure of the boat. and the wind pressure against the boat will be at least 20% higher than that against the turbine because the losses on the turbine will likely be the air that passes thru it. Understand that the percentage of 20% is likely way off because I just picked a number. It would be good for you to note that the NREL has done studies on best blade configuration for wind generators. They believe 3 blades reduce stress on the blades and offer enough space between the blades so one blade fails to fly into the other blades turbulence. This of course is design for high speed blades not low speed blades. My home grown setup uses 6 blades on a 60" dia. It is in pieces right now as I rebuild it with a larger generator as it requires over 2 hp to stall the blades to avoid over spin in heavy winds. I am working on a controller that upon the event that the larger 3 hp motor fails to stop her the controller will turn her out of the wind reducing windage as well. The rest of the control logic is for a complete system and behind closed doors.
On my old system once the initial resistance of cogging is overcome, it has little effect on power production. The major problem is overcoming the initial resistance cause by it, thus requiring higher wind speed to start the turbine. This problem has an easy cure. Remove all loads on the generator till it is producing, something they did with the controller on latter models, go figure.
Kevin Pemberton
On 11/10/2010 11:01 AM, Galstaf wrote:
Hey Kevin,
The units I mentioned are supposed to be able to withstand a hurricane according to the manufacturer.
They also claim that cogging effect is proportional to the power generated, so cogging resistance increases with load on typical generators.. not on theirs. (again.. their claims).
Can you post a picture of your turbine set up? What is the optimum output of your turbine? What is the size, weight, height of the setup for comparison?
-- Ubuntu10.04, Acer AspireOne, Virgin Mobile 3G Broadband2go. Doesn't get any better than this!
No comments:
Post a Comment