Monday, July 1, 2013

Keep the anemometer flying!

Our 40 meter tower in process of removal from the Dexter site. Photo Ben Holt, SEM '14.
(Click on any picture to see an enlarged, slide show version.)

Regular readers will know that I run one of two State o' Maine sponsored research programs to measure and analyze the wind patterns over Maine's land surface, producing basic science knowledge for Maine renewable energy generation.

(The other is run by University of Maine School of Engineering Technology Associate Professor Paul Villeneuve.)

Our own program's funding comes to an end on September 31st. Accordingly, we're dismantling our large anemometer sites, securing final data pulls and getting ready to write the final reports. I hired a small crew of Unity students to help with this, the third and smallest of Unity College's summer students research crews. (The others are the HEMS crew and the Bear Study.)

Because I have federally-sourced funding, from USDA and DoE, even though the money is "washed" through Efficiency Maine and I'm essentially the subcontractor, all my jobs must be open to all members of the public to apply. We've had some wonderful people and interesting characters become members of the Wind Crew before, but in this case the small number of hours available, likely less than eighty hours per worker for the summer, meant that only our own students applied, for which I was grateful, because of course, these are our students, from our own program and they are already trained and competent.

This years hires are Jake McGinley '14 and Ben Holt '14, both Sustainable Energy Management majors, both of whom were available because they are serving internships with local renewable energy firms for the summer. Ben is with Vaughan Woodruff at Insource Renewables. Vaughan also teaches at Kennebec Valley Community College, our main local partners in renewable energy technology education. Ben is with Chuck Piper at Sundog Solar Store.

What a great summer of practical experience these guys will have!

We had our first three work days last week, dodging thunderstorms (which are not good for Wind Crew workers).

(Our towers are all thoroughly grounded and double-grounded, but a foot tall metal pole stuck on top of a Maine hilltop is not a good place to be if there's thunder. We made a hasty exit from our site the first day, but the next day was dry and calm enough, so down the tower came.)

These NRG Systems Inc. towers, of which we have 30, 40, 50 and 60 meter models available, are not, as NRG Systems technical representative Welly Cobden says, "for the faint of heart." This is science on a large scale, using some serious engineering, and a lot of trigonometry and basic Newtonian mechanics is involved in raising and lowering the towers and generally keeping the anemometers flying.

NRG towers are the standard in the industry, and Unity College is pleased and proud to have received a lot of support from NRG over the years.

The crew must raise and lower the towers using a "gin pole" and a winch. This technique is used for many other kinds of towers all around the world, but particularly for small wind turbines, such as the popular Bergey "Excel" models, so the experience gained working on the Wind Crew is multi-purpose, and good for SEM majors in general.

We have a small 30 foot "training" tower facility located on campus, and so Ben and Jake were previously checked out on that equipment during various of their classes, but the real thing is a lot bigger and scarier, and can be dangerous. I'm very big on safety for wind crew workers. Unfortunately, Ben didn't take any pictures of use wearing our hard hats (which we put on, once the overhead danger was established -- as the tower was coming down.)

Here are some pictures Ben took:

Jake and I assemble the winch to the winch anchor, which in this site is a 2-inch eyebolt drilled into the solid rock. We hired a compressor for the purpose, two years ago when the tower was raised.

Shackling the gin pole. many shackles are used to connect to the four levels of guy wires that are needed to keep the tower straight while it's being lowered. All operate, as gin poles must by definition, at a mechanical disadvantage. An awareness of operating loads and Newtonian mechanics is a must-have qualification for a Wind Crew worker.

The fully assembled tower in vertical position.

Coming down! What goes up....

I always wonder what passers-by on rural roads must think when they see this sight -- the tower that was vertical now at a steep angle. Luckily, no-one ever drives up to find out -- or we'd have to shoo them off for their own safety.

A little bit at a time, so as not to overheat the winch.

The tower almost down. The point of maximum strain on the winch and winch anchor is when the tower is almost parallel to the ground but not yet on the ground. If the winch is going to break, or the winch anchor give way, this is the moment.

Here I'm checking the tension on the gin pole ropes, temporary guys that keep the gin vertical as the tower comes down. This is a key part of the process -- making sure the tension is distributed evenly throughout the system as the tower comes down. There's enough leverage with a big long stick like a 40 meter NRG tower to pull most ground anchors right out of the ground, or bend and snap the tower, if you allow any one guy to take too much strain.

The tower comes to a rest on blocks and sawhorses....

...then the gin pole too has to be lowered.

We use steps to catch the gin pole wire before it gets too close to the ground, because the leverage at that point would be severe.

 Detail of the tower head with anemometers

Everything safely on the ground. The hard hats can come off now, but not the gloves and safety glasses.

Another one bites the dust!

Now the hard work begins, dismantling all that steel and wire. It took a couple more hours' work to clear the site. These towers and the electronic equipment will be stored until the state decides it needs to know more about Maine's winds. 

And, a good time was had by all!

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