Hi,

Wednesday, May 25
We had a fairly relaxing day today.  It was very hot here at over 100 degrees, so we did not have the outdoor games that had originally been planned.  It was much more comfortable to stay inside with our air conditioners.

We had our pot luck as planned.  It was much cooler by 6:00 and was really quite pleasant.  As with most pot luck dinners I have seen, the food was excellent and no one left hungry.  After dinner we played a couple games of 3 - 13, moving around to several of our rigs as the games progressed.

Thursday, May 26
Today was the day for our windmill farm tour.  We loaded into 4 cars and headed to Mojave, just next to Tehachapi, about a 45 minute drive. We pulled into the office area of Oak Creek Energy Systems. 

Oak Creek Energy is a privately held company with about 40 stockholders.  Edward Duggan, the VP of Operations gave us our tour.  He was very knowledgeable, having been in the wind energy business for a number of years, and having pursued wind energy in college. 

He started by addressing us all in the office.  The earliest serious attempts at wind turbine electrical generation was in the '80's.  Government tax credits and regulations requiring the power companies to buy the power generated spurred the development.  Unfortunately, many of the original installations were with machines which were quickly put together by companies who needed to have something to sell, and the performance and reliability left a lot to be desired.  The initial machines had the propellers downwind of the supports and merely pivoted to align with the wind.  Being downwind of the tower meant the air was interrupted by the tower as the propeller went around and made for very noisy operation.  The power output of these early machines was around 40 kilowatts.  Virtually all the initial machines were made in the United States.
 

	This posed shot in the parking lot includes most of our group.
This older, smaller turbine is mounted on a "lattice" tower.

The first truly practical machines were made in Norway and included upwind propellers and active (motor driven) alignment mechanisms.  All the newer turbines are built on these principles.  While the older windmills were built on towers assembled from steel angles and channels (he called them lattice towers), all the newer ones are built on round steel tubes.  These are much more attractive and offer less wind resistance and disturbance to other turbines downwind.  The second generation turbines were about 10 times as powerful as the original ones at 400 to 600 kilowatts.

The state of the art turbines today range from 1000 to 1500 kilowatts (1 to 1.5 megawatts) with the power increasing steadily.

Oak Creek has about 240 turbines installed.  There are still over 100 of the old style 40 to 60 kw units.  Many of the original ones have been "re-powered", their term for removing old inefficient turbines and replacing them with modern high-efficiency ones.  They have sold and installed a number of their smaller turbines to farms and industry, and would like very much to see more "distributed power".

The crown jewel of their farm is their newest turbine, a 1.5 megawatt unit with 3 blades, each of which is 115 feet long, mounted at the top of a tower which is about 200 feet high.  It cost about $2,000,000!  This is the turbine Edward took us up to see.  It is very impressive!

One of the first things I noticed as I approached the base was the concrete foundation with the base of the tower fastened to it with literally hundreds of large bolts into the foundations.  It turns out that the foundation is 30 feet deep, and that the bolts are not cast into the concrete, but go clear through it.  There is a steel ring on the bottom through which the bolts pass, then up in separate tubes through the 30 foot thick concrete, through the tower base flange and are fastened by nuts there.  The nuts are not torqued to tighten them, but each bolt is stretched to about an 80,000 pound tension and the nuts are spun into contact with the tower base before the tension is released.  There is a ring containing these bolts every few inches all around the outside, and another one around the inside of the tower.
 

	Our guide is showing us the 1.5 megawatt turbine. Note the many hold down bolts around the outside of the base.  There is another ring inside the tower.
A view up 200 feet to the 115 foot long blades is deceptive.  They do not look nearly that large.

He opened the access door in the base of the tower and we all went in.  It easily held all of us.  He showed us the computerized control panel and the heavy 600 volt wiring down from the generating head, which is raised to 12,000 volts by a transformer at the base of the tower.  There is a steel ladder which allows service personnel to climb all the way to the turbine head inside the tower, while wearing the required safety equipment, of course.  This particular turbine is only the 2nd one like this ever made, and it was used for quite a bit of performance testing.  It had a ring of strain gauges most of the way around the inside of the tower about 15 feet up.  These helped determine the wind loading on the tower.  The wind vs. power curves for this model line were developed on this unit.  Every few minutes there was a bang coming from the top of the tower.  He told us that was the rotation motors re-positioning the head to align with the wind.
 

A view straight up inside the tower allows you to see to the first bulkhead. The heavy power cables run down next to the access ladder.

All of their turbines are constant speed units.  The propeller turns at somewhere around 50 to 55 revolutions per minute.  This is increased in a gearbox to either 1200 or 1800 rpm.  These speeds produce 60 Hz. power depending on the construction of the generator.  It is impossible to tell by looking whether a turbine is in very low winds producing no power, running in moderate winds producing part power, or being pushed by high winds which allow full power to be produced.  The speed is the same for all.  The generator always keeps the propeller from over speeding, and the harder it is being pushed, the more power is generated.

There are turbines now hitting the market that are not constant speed units.  Some of the newest, highest power units produce DC power which is then converted to AC by large high-power electronics.  This allows the computerized controls to always run the propellers at the most efficient speed for the current wind conditions.  It is a very expensive technology, but with the ultra high power (and cost) units it is proving practical.

I was quite surprised to learn that the 1.5 mw turbine is the only one they have with variable pitch propellers.  All the smaller ones are stall limited.  The blade design is such that when the wind becomes excessive, the airfoil of the blade stalls out, starting at the root and working itself out to the tips as the wind speed increases.
 

The original prop hub had some problems and was replaced.  This picture helps show just how huge it really is.  The holes where the blades attach are over 6 feet in diameter!

As he was concluding the tour he was asked why so many turbines are not running much of the time.  One reason is that the contracts with the power companies specify the maximum rate of power they will accept under different conditons, and they pick and choose which turbines to run to most efficiently meet these power flows.  Another reason is the power lines to Palmdale, about 40 miles away are quite limited in capacity, and the power companies do not want to spend the money to accept more power they really do not want to buy, but are forced to by the government.

 He was also asked about the various subsidies.  He said that these are mostly in the form of tax credits.  They originally were based on purchase price and a lot of the original problems were from units that were rushed to market with poor efficiency, poor reliability, and poor installation.   The early salesmen and company engineers were not very knowledgeable about the best wind locations, and many towers were installed where they produced less than half the power they would a few hundred feet away.  Now the credits are based on power actually generated, so there is a lot of incentive to create and sell high performance systems.  He would like to see all the incentives dropped and let the free market forces control the market, but that would require ALL subsidies be dropped on petroleum, coal, natural gas, solar, nuclear, and all other energy sources.  Then there would be a level playing field and wind power would do very well.
 

A more distant view of the 1.5 megawatt turbine shows how it dwarfs the much smaller units in the foreground. (The horizontal lines are the defrosting strips in the rear car window through which this picture was taken.)

This has been a very interesting tour and it was given by a man who obviously truly loves his work!

After the tour we returned to camp, where I was able to write this report before I forgot everything I saw and heard.  There were no handouts here to help me remember the salient points.

We again headed over to the Muroc Club for dinner.  This is the same restaurant where some of us ate on Monday night.  I had another of the 7 meals for under $7 dinners.  I had the chicken kabob.

Tomorrow morning we all head for home.

Friday, May 27
I left Edwards AFB this morning at 6:15, and after an uneventful trip arrived home at about 1:45.

This has been an excellent campout.  I had a few days with good friends, including 6 brand new ones, had wonderful meals, and had several very informative and enjoyable tours.

Normally I would not have written any reports on a short trip like this, but with the quality of the tours we took this time, I hoped you would gain at least a portion of the enjoyment from them that I did.

Till next time,

Dick

You can see this and my other reports on-line on my web site at:

http://myweb.cableone.net/rsmason