Friday, July 14, 2017

Quilt Block Wind Farm in Darlington, WI

Taking a little break from the log cabin project to post some details on the Quilt Block Wind Farm being built here in Darlington, WI. Pretty big deal for a small town of just 2500 people. This project has been in the works on and off again for the past 10 - 15 years. EDP (Energies de Portugal) North America is the company backing the project. Forty nine 2 MW Vestas wind generators! Being interested in renewable energy and having a wind generator myself for over 15 years I have a keen interest in learning as much as I can about the process from the ground up. And I mean UP. Here are some facts about the project:

49 two MW Vestas wind generators
$3 to $4 million each installed
Total weight a whopping 380 tons each

Normal rotor speed 19 RPM
Cut-in speed 9 mph
Cut-out speed 56 mph
Nacelle 18' x 34' x 12'  weighs 68 tons

3 Carbon fiber blades 160' long wt. 40 tons

300 foot tower 275 tons

Gravity Spread Base  40 - 60 feet diameter
40 tons of steel reinforcing bars
450 cu yd concrete

Step One The BASE

Here the concrete is being poured into the base. The form shape looks like the bottom of a wine glass. One down 48 to go...

Here you can see the mounting rings that hold and align the 140 - 1.5" diameter bolts that will secure the tower to the base. The bolts run thru the concrete to the bottom of the base.

When it is back filled this is all you see. The conduit for running power cables and communications wiring are in the center. There must be a spacer ring that is grouted and leveled placed on these bolts first as I have seen the base ring on one of the tower sections and it is only about 3" thick. Will have to check on this.

Step Two The TOWER

A small er 150' crane is used to set the first two sections of tower. The sections are bolted together by rings on the inside. They look be be 3/4" bolts and they appear to be placed every 6" on center around the ring inside. There is a built-in  platform at each level for workers to stand when they install the bolts. I suspect that each year as a form of PM the bolts are checked for tightness.

With the first two sections in place it is time to bring in and carefully stage the rest of the components that will make up the generator. The Nacelle, the Nose Cone, the Blades and the final two tower sections.

At the base of the tower a level pad made of 8 x 10 timbers for the BIG crane has been laid. To the left are the final two tower sections. In the middle are the Nacelle and Nose Cone. To the right are the three blades. This arrangement is critical as the crane base will not move once the assembly process begins.

To get some appreciation for just how BIG these things are you need something to compare them to. Above you can see my wife standing next to one of the 160 foot long blades. Below I have parked my  Mitsubishi MiEV electric car. Inside this Nacelle are the guts of the drive shaft, generator, gearbox, electronics and cooling units to keep the hydraulics cool. This weighs in at about 68 tons. My car weighs a little over 1.5 tons.

Above you can see the third of four sections being lifted. Notice the top of this crane has been rigged to handle the weight with a braced tip extension. Also the crane cable has been ran through a four pulley block and from that four cables go to the top of the tower section. It takes about 15 minutes to raise the piece to the top.

Step Three Generator Assembly

The Nose Cone is bolted to the Nacelle and the assemble is mounted as a unit. The Nose Cone holds the three massive ring bearings where that the blades will be attached. The back of the Nose Cone is bolted to a massive plate that is connected to the main drive shaft supported in a pillow block type bearing. The shaft must be 10" to 12" in diameter I am guessing. This is connected to a complex gear box to increase the RPM and then the generator is connected.

This assembly is then lifted to the top and secured with massive blocks and bolts. There is ring gear at the top and four hydraulic motors that can yaw the nacelle so as to point the blades into the wind for full power or out of the wind for maintenance and/or shut down. Again this unit is about the size of a school bus and weighs 68 tons!

Blades are the last piece of the puzzle. A specialized carrier (the size of a semi trailer) is used to hold and position each 160 foot long blade. Considerable thought goes into the placement of the blade in this carrier to insure balance and control during the process. It is hard to see in the picture but sticking out of the mounting end of each blade are what has to be 50 to 60 bolts that will be nutted up to secure the blade to its bearing race. Another item to note is the white rope below the blade. There are two of these and they are control ropes that are stretched out to the right and held by two skid steer loaders.

The Nose Cone has been rotated to horizontal and the ground ropes can be used to control the blade and with the crane operator this blade can be aligned just right (like threading the needle 300 feet in the air). It is a wonder to watch such precision and control of such massive weights. There is a crew of assemblers waiting in the Nose Cone. You can see the hatch opening. Also you can see a rope that is attached to the end of the blade and the carrier (sort of a loop). The assembler will use this rope to pull the blade the final inch or so into the mating ring of holes. If you have ever changed a tire and tried to line up 5 lug bolts with a 75 pound tire in your hands you can appreciate what is really going on here.

It took about an hour to get the blade on and unclamp the carrier.

If you look closely at these two photos you can see that the blade has been rotated 90 degrees. At this point you could hear the sound of more impact drivers tightening more bolts. My guess is that the best tightening takes place on the bottom half due to the weight of the blade and also would put the bolts at a more reachable height. Will have to ask more about this procedure. Each of the blades has a hydraulic ram attached to it that is used to control the pitch of it for efficient use of different wind speeds.

With the first blade attached the Nose Cone is rotated and the process repeated two more times. Lift, attach, rotate, repeat! Pretty well oiled operation. You could tell this was not their first time doing this.

And then it was complete and the giant crane moved off over the access road to another pre-stagged 
 location to do another one. One down 48 to go! The crane moved at a snails pace but it was rock solid. The more that six foot diameter block at cables end never even swung.

I welcome any and all questions and will do my best to seek out the answers. The more we know and understand this technology the sooner more will get on board. The renewable energy train has left the station in Darlington, Wisconsin. 53530


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