Wind. It's something many of us are obsessed and fascinated about (particularly those who look at this blog). With a passion for both wind itself and renewable energy, my buddy Craig and I jumped on an opportunity to scale one of the new 2.3MW Siemens beasts in the TransAlta Wolfe Island Wind Farm.
Tower 80 was our destination. The nacelle is located a mere 80m up from the ground, and unfortunately there is no escalator or 'beam-me-up-Scotty' style hardware, so it's a long climb. My arms, long since retired from any rock and ice climbing, were definitely feeling noodley and useless. Dividing the long climb up are about 5 different platforms, strung together with probably about 250 ladder rungs and a 1/2" steel fall-arrest cable. As you start to climb this beast, you notice a few things. First off, it is moving. The blades were tilted out of the wind and the generator was shut down for our climb up, but the thing still wobbles, and that was in a mere 10kts. Second, you start to notice the little things. There are these small little plastic pieces on every 15th or so ladder rung. Apparently, those are required so that the steel fall arrest cable doesn't wear through the aluminum ladder rungs as it swings a bit with the movement of the tower and rubs against the ladder. You can just see one in the photo above.
It's a long shlog up, but fun... As we approach the nacelle, we come to an upper platform with a junction box. The j-box here receives 12 power cables from the nacelle (3 phases with 4 cables each). When you look up, you see they are exposed and dangling here with some slack. This is to permit the rotation of the nacelle relative to the tower and allow twisting of the cables over a length of about 10-15m. Once the cables are twisted up a maximum of three rotations, a simple switch device automatically powers down the generator, rotates the nacelle 3 times to unwind the cables, and then fires back up. Did I mention those cables are damn fat!? Probably about wrist-diameter, roughly.
We then enter the nacelle. And sure enough, there is a bar fridge and a party going on! Er, well, not quite, but we were pretty high just being up there, it was incredible. Our guide throws a few switches and two large overhead compartment doors open right up wide to the sky. So long as we are clipped in with our fall arrest, we can pretty much romp around as we please. It was a perfectly beautiful sunny day, some larger clouds off in the distance to give some more variation to the horizon all around us. We could see all the other 85 turbines up there, with a clear view to Kingston, Reeds & Big Sandy Bay, down to the States, and even all the way out to the Main Duck Islands. Stunning. With the hatches wide open, we got to enjoy the ride. Our guide first rotated the nacelle around so we could have an easy view and photo shoot of anywhere we wanted, with out even moving our asses.
I was quite surprised in fact how much room there was in the nacelle. I don't find it looks that big from down below. Contained within the nacelle is a large gearbox and a generator. The gearbox has a 90:1 ratio, so for every full 360° rotation of the hub and blades, the generator is spun 90 times. We could view a little display up there that showed windspeed, blade pitch, yaw, direction, rotation, power generation, etc... Then, with the compartment doors wide open, our guide let the beast fire up. Here we are totally exposed to the universe and we get to see this wind turbine do its thing. The blades slowly twist and expose their faces to the wind, and it begins to spin, faster and faster. You cannot believe how quickly that thing spins... When you're looking at them from a distance, it appears as a pretty slow lumbering rotation. From up top, I can assure you that when you glance over the edge of the nacelle and watch the tips of the blades as they swing past the earth, you realize - holy shit, those blade tips are trucking. I guess I could try to figure it out mathematically, but I forget all those silly rotational equations... Needless to say, I figure the blade tips were moving over 200km/hr.
Looking back towards the tail of the nacelle, there are two styles of anemometer on the rear. There is your pretty conventional three-cup hemispherical cup anemometer, with a separate vane to track direction, and there is also an ultrasonic style, which measures both direction and velocity. Interestingly enough, the older technology gets the nod and it is the data acquired from the cup anemometer and wind vane that control the blades and direction of the nacelle.
Sometimes when I have been sailing on the lake, I have seen the turbines shut down, in winds surprisingly light (light 15-20kts). It turns out, that the turbines shut down for a number of reasons. First, if there is wind that exceeds roughly 97km/hr, the turbines will auto-depower by rotating their blades out of the wind. Also, if wind speed or direction are highly variable, the electronics have a hard time deciphering how to rotate, or how to pitch the blades, so the units will shut down. I think, in retrospect, the times I witnessed the turbines shut down was when there were thunderstorms approaching. This brings us to a third reason for shut down, which is the reported proximity of lightning strikes. I believe our guide said that if there is reported lightning strikes within 25miles, the units shut themselves down.
There are also a couple of other neat things in the nacelle that we did not get to play with, including i) a small crane (for hauling materials, supplies and beers up from the ground), and ii) an emergency descent hatch. I forget what our guide called it - an 'Oh-shit' hatch or something like that, but apparently you harness yourself into an emergency lowering device, climb out through a small door and that thing will zip you down in about 27 seconds.
All in all an amazing experience. As my buddy Craig said, he felt like a little kid again and I agree. It was a blast to be up there, and even better that it wasn't windy enough to be sailing! ;) As we were driving away basking in the glow of our experience, I did a quick calculation. Thank you to TransAlta for the downtime of Tower 80 that amounted to a loss of about $34 in revenue. I would have easily paid more than that for the luxury of this experience!
All photos by Craig.