Wednesday, January 20, 2010

Ross Island Wind Farm, lots of technical info...

I actually wrote most of this several days ago and was waiting to get some better pictures to go along with everything so that is why things seem out of sequence when I say "Yesterday" or talk about days now in the past in the future tense, so sorry for that.

I suppose I should share some basic info such as what life is like here, so I will try.

It is very warm here now with lots of sunshine and temperatures right around freezing. It feels much warmer than that outside as long as the wind is not blowingm but even if there is only a small amount of wind it feels MUCH colder very quickly. It snowed a bit yesterday durring the power testing and was very windy with the turbines producing about 80% of their peak output at times. The food is quite impressive here considering we are thousands of miles away from anything that people normally eat, so that is a plus! They serve 4 meals a day with the normal 3 meals and then one at midnight which serves as lunch for the workers who work overnight. Reportedly there have been mechanical problems with the C17 in Christchurch so those flights have not been happening. I will try to get some pictures of when that flight is scheduled to come in tonight. Everyone has roomates and people have very different schedules, some work at night, some have to get up at 2am to cook breakfast, etc. My roomates are a painter and a cook (who has to go to sleep at 6 or 7 to wake up at 2am so I have to stumble around in the room in the dark when I get back at night and try not to wake him.) Everyone has to go through training to be able to travel off site, my training is on Friday and Saturday. There are some nice hikes around the base but for the longer ones you have to have a radio and go with at least one other person.

The two day training process is known as "Happy Camper" and the idea is to train people to use the survival gear that is usially contained in vehicles. These survival packs contain dried meals, a whisperlite stove, about a leiter of fuel, some sleeping bags, sleeping pads, a tent, tent steaks, a hammer, etc. For the class we are given an extra sleeping pad, a flece liner for the sleeping bag, and we really have to have our ECW clothing. That clothing consists of a massive parka (red in color, so everyone calls them Big Red), bib overalls, bunny boots (really warm boots, hats, three pairs of gloves, a wind breaker, lots of long underware, etc.

So we did some classroom stuff on risk assesment then got our gear together and headed out to the field. We set up camp which consisted of 1 Scott tent and 4 four season tents incase people who thought the snow caves would be comfy wanted to sleep in a tent at some point durring the night. We dug a hole for the kitchen which makes things nice since you are then a bit more out of the wind and you have counters to cook on!

Here is a better picture of the kitchen.

Some of us decided to build snow caves or snow ditches whose purpose is to shield one from the elements and to provide some insulation as snow can be insulative. These were normally about 4-5 feet deep and about 20 inches wide. The simplest form is just a ditch with a flat bottom over which you build a roof from whatever you have or snow blocks to provide some insulation. Below is an example.

Myself and a few others decided to dig two parallel trenches about 10 feet appart then tunnel in perpendicular to the trenches to make a cave in an H shape with the middle of the H beign the cave in which we would sleep. This was just a faster way of digging a cave of this size. In the picture below we closed off one end where the silver shovel is. We fit 3 people in there and it was quite nice and comfortable!

The view from our trench... of an ice axe!

So it was a balmy 10 degrees F above 0 that night with 20mph winds. We were fine in the snow cave but all worried about what the experience would ahve been like without the extra gear we had been given and if it was -60 outside and blowing 50mph... Very sobering. Thoughts of the early explorers doing thie every day under much worse conditions in the wet with no modern materials for clothing, tents, etc were very common and only made my respect for them increase that much more.

So the next morning we struck camp and had a few lessons on how to use an old Vietnam era HF radio which was quite interesting, having to tune the antenna by changing the conductor length, and havign to aim it! These longer wavelength signals can bounce off layers of the atmosphere, the ground, etc and reach all the way around the world! We called the South Pole and asked them what the temperature was there just to make sure everythign worked. It was -17F at the pole.

Below you can see the antenna which consists of two spools of bare wire that have clips that you can use to change the length of the cable without having to change the spacing of the poles. The poles are used to keep the wire off the ground as if the wire touches the ground much of the signal is absorbed by thr ground. The longest wavelengths (or some fraction thereof, I can't remember if it was 1/2 or 1/4 for this radio), with each length of cable being 20 feet roughly.

The next activity was wonderful. I will talk more about this later. It involved wearing a bucket on my head.

I have been meaning to show some maps of the area, so here is a link.

Ross Island

So I have been working too much here already (at work by 5am, not finished till about 9pm) but there are so many awesome people to learn from! I spent most of Jan 19th working with the wind farm controller designers testing the response of the whole electrical grid to fluctuations that could likely occur.

A little background on the power system at McMurdo and Scott Base in general... Scott base opperates (like most of the world) with AC power at a frequency of 50hz where as McMurdo opperates at 60hz. This makes things complicated as the power that now comes from the turbines and large diesel generators at McMurdo has to be converted from 60hz to 50hz. This is fairly simple as either one can rectify the 60hz AC power to DC, then from DC back to 50hz AC or use a rotary converter wich basically has a AC motor that is synchronized with the grid frequency which is mechanically coupled to a AC generator that will generate the other AC frequency as it is turned by the AC motor.

So the real problem with integrating large amounts of wind power onto a small grid such as this one is that the wind obviously is a very volitile resource, meaning that wind speed and thus the power output from the wind turbines fluctuates quite a bit. As an example while we were testing over a period of 10 minutes the output from the turbiens varied over 50% just due to the change in wind speed. Thus one can imagine that if the electrical load that the diesel generator(s) and wind generators are fluctuates a small amount and the output from the turbines fluctuates a significantly larger amount the diesel generator will have to make up the difference between the constantly changing electrical load and the constantly changing wind turbine output.

This is further complicated by the fact that if your wind turbines are contributing a significant percentage of the total electrical load, the generator will have to make up a larger relative difference to fill in these fluctuations in power demand because of the variation in power delivered by the turbines. Thus the response of the diesel generators is critical to ensuring small voltage and frequency fluctuations. Obviously there are some limitations asto how fast the doesels can respond and there are soem constraints such as the fact that if you operate a diesel generator at less than approximately 30% of its continously rated load for extended periods of time parts of the engines fuel system and internals wear faster and require more maintanance and downtime for maintanace.

So one solution to this problem is to have the wind turbines try to not always produce as much energy as they are capable of producing (by pitching the blades, changing the angle of attack and thus changing the amount of lift generated by the blade wihch changes the amount of power that the turbine produces... now is a good time to ask Dr. Dering how lift really works!). If we do this and have good controls on our wind turbines we can limit their output fairly well but then we are not using as much wind energy as we could, thus making us burn more diesel or fuel than we really need to. If you are on your toes you would ask "Why not just store the extra energy untill you need it, thus utilizing all the wind energy that you create and thus saving you the most fuel?" Storing energy is one of the largest problems that man has in all of the world in my opinion. If we could store electrical energy in the same density as gasoline or diesel and could recharge these storage devices as fast as fueling a car we would not use fossil fuels to power our vehicles. Ask Mr. Roberts or Mr. Dering about Racoon Mountain and go look at it on Wikipedia. Maybe suggest a field trip to them ;)

The solution that was chosen for this project is actually an energy storage device which is directly connected to the grid which is a flywheel connected to a generator. If you think of a flywheel as just a giant disk that has some moment of inertia "I" and some rotational speed "w", you should know that the amount of energy you can store is directly proportional the the moment of inertia and exponentially (squared) with the speed of rotation. Thus your equation looks like stored rotational energy = I*w^2. Thus if you want to store a large amount of energy would you rather make the moment of inertia larger and keep the speed of rotation the smae or increase the speed and keep the inertia the same? Well, it all comes down to the speeds you are operating at, the materials available, and the amount of energy you want to store. However, the point is if you want to store twice as much energy you would have to either double the moment of inertia of the flywheel or only increase the speed of the flywheels rotation by a factor of the square root of 2, or about a 41% increase in the rotational speed ofthe flywheel. Thus if you double the speed of the flywheel you have stored four times the energy.

The flywheel used in this system is sold by Power Corp and called a Powerstore which spins at about 3600 rpm max. This flywheel is actually constructed of steel and has a positive pressure of pure Helium inside the sealed container. Other systems utilize carbon fiber for the flywheel which has a much lower density than steel but these systems can store much more energy for a given size due to the fact that they can withstand much higher rotational speeds (which are proportional to the stress in the material for a given geometry). However, this makes the frictional fluid losses much higher if you have to spin the flywheel very fast inside a container that has a gas inside it, so most of these systems try to use vacuumes to reduce these losses.

Now is a good time to ask again about energy and power as this unit can store 18 megawatt seconds of energy but can only import and export power at a rate of 500 killowatts. How long should it be able to export power at a rate of 500kw assuming it is fully charged to 18 megawatt seconds? As Dr. Dering, Dr. Taylor and Mr. Roberts would say, SHOW YOUR WORK!!!! Why does the unit not last as long as the algebra says it should? What happens if you loose grid power and there is no power to keep the flywheel rotating?

So this things job is to absorb and export energy to and from the grid as the wind turbines output fluctuates to match the load or demand placed on the grid by people or systems using electricity. Now for a very tricky question, what % of the total energy storage capacity of the flywheel would you operate the flywheel at assuming there is 1. lots of wind and 2. only a small amount of wind? Hint, try to figure out what the different components in the system are doing and how they respond to each other.

Ok, I will write more later. Here is a link to the pictures i na slideshow, I still have to add a lot of pictures!

1 comment:

  1. Dear Owen. I can't believe you slept in a snow ditch. I would have died. Glad you had fun.
    Love, ML