cc >> Cassie Immel: Hello, everyone
thank you for watching Wednesday Nite at the Lab.
I'm Cassie Immel. Tonight, I will introduce
our speaker, Mitch Bradt. During the years 2005 and 2009
the US Wind Energy Installations experienced a growth
in annual growth rates of 20%-45% capacity.
In his talk "The Wind Turbine Generators:
The Basics," Mitch will give a presentation on some
of the fundamental technical background on this
maturing energy source. This will include
mechanical and electrical slides of the energy
conversion process, a sample of energy production estimates
as well as the concept of the capacity factor.
He'll get into more of that with you.
So, I'd like you all to welcome him with me.
Mr. Mitch Bradt.
( applause )
Mitch Bradt: Thank you, Cassie.
It's really my pleasure to be here.
I bring a perspective. I enjoy coming here
and presenting here at the university.
I work here at the university. But I enjoy presenting to
crowds that are from outside the university as well.
Thank you for attending. This is a great crowd.
So, I'll talk to you today about wind
turbine generator basics. I'll also add on a little bonus
feature of a little tour. We're not actually going
to get up and walk out of here and get on a bus.
I'm going to actually take you on a picture tour, on how the
electrons move, once we've talked about how wind
turns into electricity. So we're going to talk about
some introductory material. We'll go through the mechanical
topics, then the electrical. So wind mechanical converts
to torque, torque converts to electricity.
And then we'll talk about what capacity means, and how do you
figure out how much energy you're going to get
on a yearly basis. Okay, this is a chart
of the wind resource in the United States.
It happens to have been made very famous by an oilman
from Texas named T. Boone Pickens, who created
the Pickens plan, signed up for 700 turbines from
General Electric, walked out and crashed the
wind turbine market.
(laughs)
As you see, it's been accurately described
in oilman terms, as the Saudi Arabia of wind.
In fact, there is a humongous potential of wind energy here.
It's primarily in that corridor of Minnesota to Montana
from the Canadian border down to Big Bend.
There's a great deal of wind. There are other places where
there's very, very good wind. In this, as you can see
if you can see in color, the dark red is quite good wind.
Now, looking at the installations that have gone
on, here we have a chart of the installed capacity
during the year, and also the cumulative one.
I know I've been asked not to wander
but I have to for this. Starting here in '95
we have about a gigawatt in the United States
about 1,000 megawatts. That's about, you know
about what a typical nuclear power plant
or a big coal power plant produces.
Portage has the Columbia Energy Center.
It's about that much. That's the entire
country of wind farm. Then we have these
little blue bars of increase. If you notice in 1999
there was kind of a pretty big step, right?
Then there was a drop. Then a step, then a drop.
Anyone guess why that got
stimulated, and then didn't? Sorry?
Tax incentives. Production tax credit.
Congress put it in then let it expire.
Then put it in and let it expire.
And in fact, the developers, really, you know, went
gangbusters to get into those tax credits
and then pulled back. Well, by 2005, they kind
of got wise in Washington and they approved a two-year
and then a three more year extension.
Now it's been extended for one more year to kind
of give a little bit of what I'll call stability
at least to the business. You can see it really took off
starting at about 2001, or so. We were having year
over year expansion in what we were doing.
I will tell you that 2010 the capacity built in 2010
and that's reflected by this multi-color one
was slightly less than 2009. We didn't build more than
we had in the previous year. In fact, it was supposed
to be slightly less but it was a drop of 70%.
So we still have more wind but we had a big crash
in the market. Anyone want to guess why
the crash happened? There's still all
these standards that you've got to meet.
You've still got customers paying for green credits.
Cheaper natural gas has an effect, but that wasn't
really the reason that caused the crash.
Bear Stearns, AIG. The banks crashed
nobody was lending money to anybody, so we had a
long period of time when you couldn't, kind of walk
into Chase or JP Morgan and get a $400 million loan.
They just weren't giving them out for a while.
So we're now at the end of a development cycle when it
hasn't increased as much. That isn't to say that it's
not going to keep growing. I mean, every expectation
in terms of order entries with the suppliers appears
to be going better. In fact, the world's largest
wind turbine manufacture a Danish company called Vestas
has big operations in Colorado and a research center
here in Madison. They announced that this
is the biggest year of sales in North America, ever.
So it's looking up again. But it may not be up
again until 2012, or so. Okay, a little bit
about power systems. How is a power system built?
How does energy move to your house?
Well, we start here, and I'm going to use this pointer.
I'll try to move it so it's easy to see.
We start here at a power plant. This could be
nuclear, coal, gas. This building could be a
representation of, you know 100 wind turbines put together.
The power comes out at some what we call medium voltage
15,000 volts would be a medium voltage.
Anything between 5,000 and 50,000 is what
we call medium voltage. It gets stepped up to
transmission where it's what we call high voltage.
The highest high voltage in the state of Wisconsin
is 345,000 volts. Places like Ohio and
West Virginia have 765,000. But these are the big towers
that you see when you're driving on the Interstate
and you see them running across the landscape - so
that's moving full power across the landscape either
from far distant power plants or mutual support
from one utility to another like oh, my nuclear power plant
has to go down for new fuel can I buy power from you
so the power moves across the transmission system.
So, it's moving across the transmission system.
It then goes to what we call a substation or station
is listed here. It may go to sub-transmission
which is more of the same. It's moving power
but at this point it's a lower voltage.
Because there are several feeders coming
off at sub-transmission there's less power
going different directions. Then it pops down here
at a substation, and you've probably seen these, too.
They look all gray. They're surrounded by a fence.
Sometimes they have signs saying "stay out," and that's
a really good thing. If there are any kids here
please stay out of these. They're really harmful.
Then it runs down the street on these poles you've seen
and probably have miscalled "telephone poles."
They're actually utility poles. The telephone company gets
to hook on to our poles. They're not their poles.
Anyway, along these "telephone poles," excuse me
then to your house or to your business.
That's the way electricity makes it's way to your house.
Okay, I want to take a sidebar with this slide here.
A number of the slides here are very general
and introductory. And a few of them, I've taken
out of my real technical stuff so if you see a lot
of equations and diagrams and so forth, just let it
wash over you, and just pay attention to what I'm saying.
In controlling a power system and keeping it stable
we need two things to happen. We need the frequency
which in this country is 60hz that means every second
the voltage goes from positive to negative 60 times.
We need that to stay at 60hz almost exactly.
We need the voltage that's at your house
and all over the grid to be about the same all the time.
And based on the flow of power into and out of the system
we can control it. Now, if you switch on another
light bulb in your house more power is being drawn
out of the grid. So somewhere, energy has
to go into the grid. There's a lot of kind
of light storage, I'll call it. It's only good for just a few
milliseconds, that can handle powering a light bulb
for the first little bit of time that it's on.
Then eventually more natural gas has to get
into the turbine, or more coal has to be thrown in
or you know, the things that we can control
the power plants that we can dispatch, they have to raise.
They have to raise their output. Based on the control of power
in, we can keep the voltage stable and the frequency stable.
If either one of those goes unstable, we get what happened
in 2003 in New York and Ontario, and you know the great
blackout in the northeast. Okay, let's talk about
the mechanical side of wind turbine generators.
Here's a nice picture found in the New York Times that
explains it pretty well. We have basically four major
components that I'll point out. We have, of course, the blades.
We have three of them. That's a very standard design.
It's known as the Danish because the Danes
get credit for it. The Danish three-blade
upwind turbine. Upwind meaning the blades
are on the upwind side of the powerhouse.
Connecting the three blades together is the hub.
There's a shaft going into a box that sits on top of
the tower called the nacelle. That's a French word that
people who are not familiar with aerospace or wind have
not heard, N-A-C-E-L-L-E. The nacelle is basically an
enclosure that holds everything. Inside the nacelle, you'll have
various different equipment. Usually, you have a gear box
to raise the speed of the shaft. If you've seen those--
A show of hands. How many people here
driving along the highway have seen turbines?
Are they spinning fast or slow? Okay, anyone want to care
to venture a guess how fast the tip is moving on those?
Yeah? 130 miles an hour, almost.
(inaudible)
Right at 130? Okay.
A very efficient modern turbine will have speeds
of 150 to 225 miles per hour, typically.
But they're just humongous blades.
But they are moving at a very slow rpm, like 20 revolutions
per minute, or three per second. Did that work out?
No, it couldn't be three per second.
Three seconds per. Thanks, 15 years of math and
I can't even do that, sorry. So because the shaft speed is
so slow and the type of generators that would be
in this turbine example need a quite fast, you have them
running at 18 rpm, you need a gear box that will get you
up by a factor of 100 to get up to 1800 rpm.
That's typical generator speed. There are generators that
don't have gear boxes, they have really humongous,
weird looking generators. They're made by the Germans.
Very effective, very reliable, weird looking though.
And to give you a perspective, on the far right,
there's a turbine. That's the perspective of the
most common turbine in this country which
is the General Electric 1 1/2 megawatt machine and the
blades are about 77 meters in diameter and the height
might be about 80 or 90 meters. Yeah?
Are you also going to tell us about the blades that are
vertical and go around a vertical axis?
Bradt: I'll address it right now.
They were popular in the 80's when there was a great deal
of expansion into renewable energies and we thought, oh my
goodness, we have to respond to the air oil embargo so
let's research all kinds of different things.
The benefit of the vertical axis, the most common one looks
like an egg beater, is called the Darrieus turbine,
the benefit of that is that you don't need to change
directions from your turbine as the wind changes -
it'll take wind from any direction.
Okay? The downside of that turbine
is that they distort themselves essentially.
Now if you remember from high school physics about
waves and nodes, you probably remember an experiment or
something your teacher did, possibly took a chain or a rope
and they spun it around and you could see the wave
on the rope. So there were points on the
rope like you're holding the end of it, it's still
in space and you're spinning it, and then it's going
"woo, woo, woo," right? So, you've got this turbine
which is a huge shaft made of metal so it's flexible and
it's absolutely fixed in space on the bottom and
then it's doing this. Now to try to fix this
spot on top in space, they use guy-wires, okay?
They try to hold it in space. The problem is you've got all
that vibration going for years, the guy-wires are going
to loosen up and then the thing's going to fall apart.
So for big turbines, they got installed, the company
installed them, basically went broke trying to fix them and
they were abandoned. Now there are vertical turbines
used in small application like putting up top of your house.
They're easy to put up but in that case, you're talking
about such small forces, and it's really easy to build
the shaft so it's got way too much metal so it can
tolerate all that and last for ten or 20 years.
Beyond that discussion, I don't talk about them because
in the utility, in the 100-megawatt scale
and the power grid scale, nobody uses them.
Every once in a while, someone says, oh I made this
great new discovery! And it's just kind
of a reinvention of the same great idea that eventually
will have the same problems.
(laughs)
Okay, so, how does the turbine work?
First of all, the blade is an air-foil, it is just like
a propeller in an aircraft or a wing.
It's an air-foil. It has a different shape
on one side than on the other and notice here that this
edge here on the bottom is kind of short and
this edge on the top is a little bit longer.
It's very subtle but there's a difference in length there.
And then if we tilt this blade, see this dashed dot line here
going through the middle, we call that the cord.
If we point it a little bit up from the direction
the wind's going, we actually accentuate the differences
in distance that the air molecules have to go.
So, as wind is hitting that air foil from the front,
the air molecules coming in that are just slightly above,
they have to go a longer distance and they have to go
faster than the air molecules that are going underneath.
As a result, you get a development of low pressure
above the wind and high pressure above the wind--below the wind.
So, essentially, this airfoil is sucked upwards
by the aero dynamic forces. Now those a bunch of arrows
that are in a kind of all different directions,
that's sort of how the, at each different point,
where the forces are pointing, but we can take all those
forces and add them together into one aero dynamic force
which is going kind of this direction and then
we break those two forces down into two components,
one that is in the direction of the wind, that's the
bad one - it's called drag - and then the good one is
perpendicular because it's lift, it's lifting the aircraft
off the ground. Now, let's take that airfoil
and put it on a spar, attach that spar to a shaft,
okay? So it's now like a wind turbine
blade and let's let it spin, okay?
As this is moving forward in this circular arc here,
we have a artificial wind speed that just comes from the blade
moving through the air, right? And we also have
the wind coming. We add those two together
as a vector and we get the resultant wind.
Now, would you notice that this resultant wind and the
cord, the angle there, that angle right there,
is about, you know, roughly about the same as what
this one here called. So they're both the
angle of attack. So, now, we control--many
turbines have the ability to control the, what we call
the pitch of the blade a little bit and we can get
at the forces, the -- forces that we want for our
particular power setting. So we're creating that,
those lift and drag forces - now, the lift force, again,
that's perpendicular to the relative wind and it's
in this direction which is kind of weird.
We don't care about going sideways.
We have--we can take that and decompose it into two
directions, one that's in the direction that the
blade is spinning and one that's perpendicular to that.
So, this is what we call the lift that creates torque.
That's the really good stuff, that's what--that is the force
that is a result of us sucking energy out of the air.
Okay, this thrust--this is the structural engineer's nightmare.
Because what that's doing is as the blade is moving,
you know, it's being pulled this way by the torque
but it's being pushed backwards by the thrust.
They kind of have to make sure that the blade doesn't swing
down and strike the tower because then turbines fall over.
So they actually have to design these turbines
with advanced deposits and so forth to make sure that
they don't flex too much. Now, once we have the blades
on here and I've chosen to show a two-blader turbine,
not because that's the common turbine anymore but
because it's easy to draw. And as you're moving, as
you're spinning, we're going to have that torque going
into the nacelle on the shaft and I want you to think
of a topical to tip speed. We mentioned it
130 miles per hour, 150, that tip speed is going
to be the rotational speed so the 18 rpm times the
distance of the blade so in my equations that's
omega times r. Omega is the rotational speed.
Okay, there's a few equations-- these are the last equations
I'm going to explain to you, the rest I'm going to pass
through quickly. Back to high school physics
again, kinetic energy - that's the energy of the flowing air -
we learned that it's 1/2 times mass times velocity squared.
So a bigger mass has more energy, a faster object has
much more energy, right? Now, we also know that the
flow of the air, the flow of the mass is equal to its
density times its speed times its velocity times the area,
okay, so the turbine is going to spin in a circle and you've
got this pancake shaped piece of air coming through it
at any given second. So if we took--take that m,
there's a little dot over it, over the m, that means the
change of mass in time - cool little Calculus thing.
If you drop that m dot into n, okay so it's mass per second
now, so then that equation, which is e dot
is actually power. You know the difference
between energy and power - energy is an amount of energy
to do some work, power is how much energy you need
to move in a given second. So, power, remember
we had that row? We have the row,
that's the air density. Higher air density is good
and we had a v squared up in the first equation and a v
in the second equation so now we've got v cubed.
And we have an area, so if you make your turbine bigger,
we get more power. If you site your turbine at a
place that has better wind as in faster wind, you get much,
much more power. In fact, twice the wind,
eight times the power. So now, the weakened state
you know, a turbine is just not going to be able
to take all the energy out of the wind and convert
it to useful work. So we're going to define a
coefficient of performance - cp. Now, Professor Betz lived
in Germany and he did his work in the 1920's and I remember
of a movie--this makes me think of a movie in the 80's called
"Bill and Ted's Excellent Adventure"
and they're trying to figure out, you know, how to study
for their history test and so who is this guy named Socrates
and they come up with a answer which is, he's a dead dude.
(laughter)
He happened to be a dead Greek dude.
So who's Betz? Betz is a dead German dude.
He happens to be the father of the knowledge of how to
make the aero dynamics of turbines work.
He showed through some Calculus that if you took the
air upstream and you slowed it down so that it was one-third
the speed, so say 9 meters per second down to three meters
per second, if you did that, you got the most possible energy
you could get out of it. If you tried to slow it down
more, you'd actually get less energy and I won't go
into the derivation but basically the theoretical limit
he came up with, we've never been able to achieve is 59.3%.
Now, on this chart, I'm trying to show what you can
practically get out of a turbine and compare
two or three or four or five different turbine types.
So, on this chart, on the vertical axis we have a
coefficient of performance and that is how much energy can I
get out versus how much energy is there.
And here, on the horizontal axis, I've got the variable
is tip-speed ratio. Remember I talked about
tip-speed, how fast the tip was going, it was a ratio
of how fast the tip speed is going verse how fast
the wind is going and I won't get into the mechanical and
aeronautical details as why that matters but it works out
that that is a significant variable and everything
varies around that. So, up here on the dash line
that's the Betz limit. This curved line here is the
Stynmet limit. Who's Stynmet?
Well, he's another German dead dude.
He came up with figuring out how to--seeing how much
energy was lost from weight rotation.
But I won't get into those details.
(inaudible)
You're right, he was a dead American dude.
So, now looking at the various different turbine types
we have here, here's the Darrieus turbine you asked
about, here's the Western American wind grows, about
45 million of these got built between 1850 and 1950
and installed. They're mostly now just sort
of for aesthetics. The original turbines or the
very early ones, the Dutch stock mills, so built
in the 17th century - that's there, and can anyone
tell me why the three-bladed turbine won, looking at this
chart, why everyone's building three-bladed turbines?
It gets the best energy harvest. There's no other turbine
that can achieve as high as it can get.
And it shows here that it gets up to, I don't know,
what is that, maybe 47% and I'm sure every wind turbine
manufacturer salesman will tell you, oh we do that one better!
But in fact, very rarely can they even get to that number.
Just, you lose energy from bugs that have smashed themselves
on your surface and dirt and wake rotation -
there's all kinds of things that are working against you
at getting that work out. That's about what they can get -
a little less than half of the energy.
Okay, so the electrical type and this is where I'm going
to ask you to let the slides wash over you because I do
kind of go super geeked out with some of the slides
and I'll just kind of talk past them.
So we're going to talk about the two kinds
of generators that matter - a synchronous generator and
an induction generator and then we're going to talk about
the types of wind turbines - there are four of them
based on speed control. We categorize them
on speed control. Okay, so the synchronous machine
- this machine generates 99.95% of all the electricity that's
ever been manufactured. This is what is running in
hall plants, nukes, gas fire, hydro, everything you can
think of that are big power plants and including
some wind turbines. It is simply a big
electromagnet - it spins and you've got all these conductors
on the outside - they see these magnetic fields whirring
past them and voilą! Electricity comes out.
And there are three conductor sets, there's
A here, B here, and C here. And because they're
separated by 120 degrees around the circle,
we get three different phases of electricity and that's
what we're seeing here. We've got the sign waves
and you get three of them. Now in your home, you get--you
only get one of those phases and the reason is the
power company runs the line - it's a three phase line -
into the neighborhood and then splits one this way,
that way and that way to go to different houses.
So you only get single phase in your home.
Businesses almost always get three phase to run really
big motors and stuff. Okay, I'm going to skip this
because I don't want you to have to follow my derivation
but there's a lot of math involved and this is kind of
why electrical engineers study so much math.
Same with this one. Okay, sorry.
There we go. What I want to show with this
is that any machine that has a connection between torque
and electricity can do both. If you run it in one mode,
it can generate electricity. Generation is just torque
goes in, electricity goes out. Or it can motor.
You put electricity in and you spin it.
And there are ways to control how much you're getting in
and out based on that electromagnet, controlling
that electromagnet, being more magnetic or less or by
how you connect it to the grid. There are ways to get
more power out of it. And that goes back to when
I was talking about the power system that we control
the power to keep it stable, we do it by using
synchronous machines often. There are other methods too.
Now, the other machine that exists is the induction machine.
This is the machine Nikolas Teslay invented
and I said 99.95% of electricity is generated by
synchronous machines. 90 something percent of
all motors in the world are this machine.
They're simple, they're rugged, they're built
like a Timex watch if you remember that commercial
- it takes a lickin' and keeps on tickin'.
You can beat the hell out of them and they'll keep running.
They are a little more difficult to control and
they're a little more--harder to understand in terms
of the theory. But you plug them in and they
run is what good's about them. And I'll point out that the
very first wind turbines were these types of machines.
And what was weird about that is that nothing else was
generating power with electricity in a big way.
And often what they have is instead of an electromagnetic
on the rotor, they have this cage that we call a
squirrel cage and to me, it looks like the cage I used
to have as a kid for my gerbil but the industry has selected
the term squirrel cage and that's what--that's
all the rotor is. So it's really simple.
Going past, this is just to tell you that the induction
machine can be a rotor or a generator as well.
So, comparing the different machine types - I talked to
you about the synchronous machine and the induction
machine - the other--the motor in the middle, the
machine in the middle is called a permanent magnet machine.
It's a synchronous machine, you don't need an electromagnet,
it has magnets and it's becoming very popular because
it can be really small and they can be really compact
and they're even better than the induction machine.
Although there are some that would argue with me,
I'd taken a lickin' and keep on tickin'.
In fact, they are what are in hybrid cars.
That they're all that right now. So the third type of turbine,
like I said the very first one is very simple - it's--you've
got blades, goes through a gear box into an induction
generator, electricity goes out onto the grid.
Now, the blades may be able to pitch a little bit
for control - all they can do is basically control so that
the turbine is no longer spinning or so that
it is spinning. They can't actually control
their speed because of the motor that they're connected
to--the generator they're connected to.
It is fixed. It has to run at the speed
that the electrical grid is running at.
Remember the sixty hertz has to be maintained - it has
to be spinning at the same speed all the time.
And so then there are some other accoutrements of equipment
that we might install, including capacitor banks
to help with startup--I'm sorry, capacitor banks to help
with the current and soft starter and I won't get
into those details. So the type two wind turbine,
same machine as we saw before, however we can actually get
at the currents that are in that rotor, the part
that's moving and we can add extra little resistors in.
And that changes the characteristic so we can start
changing the speed and we can only change the speed by 10%.
We can make it go 10% faster, which, remember that curve
that showed all the turbines compared with each other and
they had this shape like this - there's an optimum tip speed
ratio that you want to be at so that means if the wind speed
increases, you'd like to spin a little faster.
So this is the beginnings of being able to change your
speed a little bit. Now the type three turbine,
this is currently the state of the art.
We've now taken, where that resistors were, and we've
been kind of adjusting-- messing with the currents
on the rotor and we're putting in a power supply.
Basically these things I'm showing, these boxes on
the bottom- they're basically like a variable speed drive
that might run fans in a building or something like that.
But what it's doing is it's taking power off the grid
and circulating it into the machine to the
technical term is to funk with the magnetics in the
machine and adjust where the voltage is going.
It also allows you because you cannot only adjust
the voltage, you can adjust the frequency, you can make
the machine go slower or faster, a bunch slower and
a bunch faster. Theoretically,
plus to minus 50% speed difference, often the
manufacturers only build it with a plus to minus 30%
or thereabouts. So, as your wind speed changes,
you can really try to optimize it to the most efficient
rotational speed. When it's operating
above synchronous speed, it's spinning extra fast.
What will happen is power will come out of the machine,
out of the starter, it will come out this way and power
will also come out--a little power will come
out of the rotor. And when it does that, you get
a net power, you know - a great deal more.
That makes sense - high wind speed, high
spinning, lots of power. When you're operating
below synchronous speed, you actually have to take some
of the power that's coming out of the machine--
primary terminals and you have to circulate it back.
And the reason is to basically keep the voltage set so
it doesn't cause a collapse or anything like that.
Now, in net, you get less power out but you're
getting power out. Whereas other machines would be
able to get it, not only can you optimize to better speeds,
you can get power out at wind speeds that other
turbines cannot. >> Isn't the induction generator
generator self produced? >> Bradt: They are.
But if you bring slipperings to get the currents from the
rotors out, you can connect these power supply devices
- they're called inverters - onto it.
(inaudible)
Well they can self induce from the stater side or you
can control what's on the rotor from the rotor side.
You have both effects happening at the same time.
Okay, the type four, the kind of the last step that's been
taken in development is you take essentially those two
power supplies and you put the machine behind that and
the grid on the other side. The result is, is that the
machine puts out its power, it goes through one of the
power converters, and you'll notice between the two power
converters, there's this little device here -
that's a capacitor - it'll hold a DC voltage.
So this AC here from the machine gets converted to DC
and then this converter puts it back to AC.
So you can control this converter to always give you
exactly sixty hertz, okay? Now, over here, we don't care
what the frequency is here because we are going to convert
it to DC anyways and then reinvert it back to 60 hertz.
So we can run that machine at any speed, so the speed
variation now becomes very, very wide.
It becomes as big as you want to build it,
economic considerations aside. One of the other benefits
is that you can whack that gear box.
Gear boxes - heavy, it's expensive, and it's often
considered the biggest problem for reliability.
It breaks a lot and when it breaks, they're big and heavy
and it's hard to fix. So, there are some manufacturers
of turbines that have decided to go that route and they
have what I described as the really weird turbines.
(inaudible)
Well typically, you're going to have about--Sorry?
Can you repeat the question?
Bradt: Oh okay. He was asking to compare the efficiency
overall of a machine that has a gear box and a
conventional method of putting the electricity out
versus a machine that you whack the gear box and
you push everything through these converters.
So, the first approach, which is a gear box,
you're going to lose 15 to 20% of your energy immediately
and you have humongous cooling systems to get rid
of all that waste heat. Mechanical engineers
are just not as good as electrical engineers, so.
(laughter)
Then you're going to have about 98% of efficiency
on your motor, on your generator and then you're probably going
to have about 95% efficiency. So, 20% loss and then 2% loss
and then 5% loss, so you're probably coming out -
what's the math? - about 80% of the power.
If you whack the gear box, of course, you're removing
a big heat source but you're also pushing a lot more
power through the silicon. So your losses go up.
In general you're going to get more through this.
But here's the thing, it kind of doesn't matter if you're
in a good wind zone what your efficiency is so it's not---
that's not the reason why people would decide to use it.
They would decide based on predicted reliability.
Am I going to have to replace my silicon parts more often
or my gear box? Okay, this is an example
of one of those. This is manufactured in Iowa,
called "Clipper," California company.
They have a drive train where it has one slow shaft and it
actually has four high speed shafts so they have four
different generators on there. And the benefit of that is if
one of the generators blows, take it out of service really
quick, run a guy up the tower or a gal up the tower, pull
the one off, toss it down so you can get another one.
Put the thing back in service with three of them and run
it the graded operation. This is kind of an
interesting design that they took.
Here's another one: remember I said weird?
This is weird, this is what I mean.
Instead of it looking sleek and narrow than this cell,
so the wind can get around it, because this generator--this
generator down here has no gear box, it's not
going to spin at 1800 rpm, it's going to spin at 18, and
so it has to be huge, it has to be like a huge pancake.
And, as a result, then this cell is a very funny egg shape.
It is kind of odd looking but they have their
efficiency advantages and their reliability issues.
Okay, so I'm going to talk about capacity and
energy production. So capacity, if you think
about it, that's the nameplate of what the machine can do.
So, a GE one and a half wind turbine has a capacity
of one and a half megawatts. It can produce
one and a half million watts. If it runs continuously like
say a nuclear power plant, which that's going to be a
1,000 megawatts, you're going to get a full capacity factor.
Now, using this one and a half megawatt example, you have
8,760 hours in a year, except leap years, and if you multiply
that out, you could get out of that machine 13,000
something megawatt hours or 13 gigawatt hours.
That's a lot of power. Okay, here's the deal.
The wind doesn't blow all the time and it doesn't blow fast
enough all the time. So, it's not going to get
the 13 gigawatts. So let's look at what
a turbine can produce. Here's that GE turbine.
This is the kind of the performance curve and I want
to point out three different wind speeds of significance.
First one is the cut-in, that means below the cut-in,
which is typically about three meters per second,
you get no power out. Once you get above three,
you start getting some power but you don't get very much.
You're not getting one and a half megawatts.
The next speed is the rate-in, typically 11, 12, 13.
Once you get to that, you got full power.
And to stay at full power without like overheating the
machine, the blades start pitching and spilling wind
as you get too fast, they're just letting some
of the energy go by because they don't have the electric--
magnetic capability to convert all that.
And then the final speed is the cut-out speed,
this is usually about 25 meters per second which
is about--it's above 60 miles per hour and that's gale force
wind at that point. So you have very severe storms
Turbines shut down, furls its blade so it can't
catch any of the wind that is coming and then sometimes
if it's really extended time will actually turn sideways,
okay? And just stay out of the wind
and just try to stand up. They can usually withstand
quite high winds, they cannot, there's no turbine built that
can withstand a direct hit from a tornado.
But there are turbines that are considered hurricane safe.
Not category five but like maybe up to three, I think.
Okay, so capacity factor is the ratio of
annual energy produced - right, remember we're not
going to get that 13 gigawatt hours because we're on that
slope some of the time, we're not always getting
the full-out. And so, okay, capacity factor
depends mostly on the wind resource - you locate
in North Dakota, you've got great wind.
If you locate in Georgia, you have terrible wind, okay?
You're going to have very low capacity factor.
It can be enhanced by selecting the particular
turbine that may do a little better than the others.
So, let's consider a contrived chart, and this is something
that the assessment people do for a one and a
half megawatt turbine. And so, if you know what your
average annual wind speed is down here, there's a,
you know, data to tell you how much energy you're going
to get out per year. So let's do this location and
I just picked a spot in Wisconsin, a random spot,
that had an average speed of seven.
Now at seven I'm going to get, if you can read off this chart
- it's a little hard to see - it's 3,500 megawatt hours,
so 3.5 gigawatt hours. So divide 3,500 by 13,000,
you get 26, 26% and that's pretty typical for Wisconsin.
You can get about 26% capacity. And if you go West from here,
you can get better. I've heard claims of 45.
Some people made claims of 50% but I have yet to have that
proven to me that that's actually occurred.
Okay, so, wind sight assessment, how do we come up with the
assessment of how much energy we're going to produce
in a year? Well, first thing you do
is you go out and put a bunch of anemometers - those are
those cup things that whirl around and tell you the speed.
You can also do it with sound. They have sodar which is a
big huge horn, it bellows, and then it waits and listens
for the sound to be reflected and it can use Doppler.
Same stuff that the cops use to bust you on speeding
with their radar. They're using with light.
You can also do a light detection so they shoot
lasers up and detect what the speed is.
Anyways, you detect for one, two years and you get--you get
all the wind over those time and you drop them into bins.
How much of the time during that year are you at zero?
How much are you at one? How much are you at two?
How much are you at 25? And we just create a
distribution chart here, okay? So I'm going to pick an example
there at nine meters per second. At nine meters per second
at this location--we're there at nine meters per second,
just a little bit less than 5% of the time, 4.76% of the time.
So that's 417 hours per year it's at that speed.
There's the curve of a particular turbine.
This is not the GE 1.5, it happens to be a Vestus V47,
an older turbine which produce 660 kilowatts,
so .66 instead of 1.5. And that's what it performs
per wind speed. You notice there's quite a few
wind speeds in the beginning that nothing comes out.
Now, at nine meters per second, it's producing 362 out of 660
possible kilowatts and so then if we multiply the top black
square with the middle black square, we get that
black square, okay? So at nine meters per second
at this location with that wind speed profile,
you're going to get 150, 151 kilowatt hours per year.
You do that for every wind speed, you go bump, bump,
bump, you add them all up, and you get how much wind--how
much energy you should be able to extract.
That is the key point of a wind site assessment
that's done for two or three years ahead of time.
The banks do not want you to ask for money until you can
tell them and prove it that you're going to get
that much energy. And because they have
all the money, they control what gets built.
(laughter)
Okay, so here are a few little resources, I wanted
to just make a plug for my own department, we run short
courses for people in industry, three and four day courses
for people to spin up in an industry and it's the
Department of Engineering Professional Development.
I'll leave you with that. Okay, so this is the tour
I was talking about. We're going to have a picture
of the balance of plant. The balance of plant--
what's the balance of plant? It's everything that's
not the turbine. So, wow there's a big
engineering drawing with a lot of lines on it.
Every little box, this is a pretty big wind farm,
this is schematic diagram. Every little box
here with the text - there's one, there's one,
there's three together, that's a turbine.
That's a single turbine. And all of these lines that
run in between them - da da da da - and so forth,
that's the collector, the feeder, that's where
all the electricty comes collected together.
And then each group of turbines - there's a group,
there's a group, and so on - all make their way on what
we call home run feeders back to substation and
into circuit breakers. So they get laid out and
bunched into little groups based on where they're located.
Now, that's really neat and they're all kind
of lined up in lines. They're not actually
laid out like that. That's the physical plan
of how they'd be laid out. And the way they're laid out
has been partly been where the ridges, where's the
best wind, and where's Farmer Brown who wants you
to put turbines on his site because he's going to get
10 grand a year and where's Farmer Smith that
doesn't like wind turbines. So you've got to work around it.
So I think here is lucky Farmer Brown and there's
obstinate Farmer Smith is basically how it comes out.
So, general layout of a collector - you have
the turbine and up inside the turbine, you have this is
a symbol for generator and some converters and breakers
and protection, you know, all the equipment that's up
in the tower. Then you have the cables
running down the tower, then you have a transformer
that's usually just outside the turbine on the floor--
on the ground, I'm sorry, that then connects to the
collector system through some switchings.
Now it is possible that the pad-mounted transformer will
be up above in the nacelle but this is typical.
So that's what the turbine step-up transformer looks like.
If you ever get to go to a wind farm, you'll see
here's the entranceway and then there's this--they're
almost always green, this green box sitting out.
That's what takes the voltages, you know, in GE's case,
from 575 volts up to 34,000 volts is what we generally
collect at. It's possible to have a
transformer located up in the nacelle basically if
you have really heavy parts up at the front of the nacelle,
it's a good idea to have a really heavy part
in the back of the nacelle. The transformer's nothing but
a big hunk of steel wrapped with some heavy copper.
Okay, so then it makes it down, it's gone through the
transformer and it drops into the ground and here are
the cables running away from a turbine towards
their next site. They're very typical - dig
a trench, four feet deep, that actually doesn't look
four feet but I think they have lowered the soil.
They'll put it in, put the backfill in,
a very special backfill and then they'll reclaim
the land - they'll put more on it so then you can plant
grass and all that kind of stuff back on there.
Gets laid out on the trench and there's guidelines as
to how that's done, powers running down the side of
this road to the next site -- this is more than I wanted
to give you but that's what a conductor looks like,
you've got this outer jacket, you've got some protection,
the insulation to make sure that the 34,000 volts doesn't
hurt, harm anyone. And then you've got actually
the aluminum or sometimes copper conductor in the middle.
Okay, occasionally we will use overhead lines,
the so-called telephone pole type lines.
It's uncommon, farmers don't want it to cross their land
because they have to run their, you know, their tractors
around it. There are times when you
get the landscape like creek crossings or a lot
of granite or something like that where it's just impractical
to go underground. You'd have to do some blasting
or something like that. But they'll just pop up out
of the ground and they'll run overhead, usually for a
very short distance, for aesthetic reasons,
they prefer not to use this. But they do get done.
And then you've made it all the way back, you've gone past
all these various turbines and collected all the current,
all the power together and you go into the substation.
When the cable pops up and it's hard to see but the
cables are coming out of a pipe right here out of
a conduit right here and they're splitting three ways.
There's one, there's two, and there's three and then
the conductors go up to a bus and that's how the electricity
kind of gets distributed within the substation.
And that then pops down into these four gray boxes,
there's a fifth one also, that are called
the circuit breakers. A circuit breaker is a device
that if current is flowing and there's way too much of it
because you have someone that's dug in with a
caterpillar and the sparking, narking, and there's 50,000
ants when there should be like 400, the circuit breaker
senses that and, poo!, trips. You hear a big bang, bang!
And but it stops the current. The additional breaker is
to protect the next device, I'll show you, which is
the transformer, another transformer.
We had one that went from 575 to 35 KV, this transformer
then goes 35 KV up to 345. And now that the power has
moved from here through this transformer and out onto
the much higher voltage lines, it's now on the grid
and it can make its way to other substations and
into your home. And often there are other
devices that get put into the substation to help
control the power flow, control the voltage there.
We call react developments, capacitors, and the other
device is called a reactor. And then there's what
a capacitor bank looks like is boxes.
And here's what reactors look like, they're usually
like donuts stacked one on top of another.
And then there are special, expensive, but very capable
elements that work like the converters and turbine
to push the voltage around. And I bring those up because
the two biggest competitors for that are both
Wisconsin companies. This one happens to be
Essence C Electric which is in Franklin, a suburb of
Milwaukee, and the other one is American Superconductor
which is here in Middleton and also in Waukesha.
So, that's--this is one of the examples where
wind installations generate a lot of work, particularly
locally here in Wisconsin. So, are there any questions?
You've been asking them throughout which is great
but any...yeah? >> Lots of them are stocked.
It looks to me like 25% of them are stocked.
What's going on there? >> Well it would be speculation
as to what exactly is going on but what could go on with
that is that there could be a problem with one of the feeders
or they could have to work on due maintenance on one
of those breakers. So remember how I told you how
they all get brought in in their different groups?
Maybe they're working on that feeder and they had to drop
it out and if--there's nowhere for the energy to go,
they don't let the turbines turn.
If you ever see a farm that--a wind farm that you drive past
and it's a really blustery day, there should be a lot of energy,
and all the turbines are off, either the wind farm hasn't
been commissioned yet - it just got built - or that
main power transformer, the one place the power gets up
onto the grid, that's out of service.
That's happened before - it happened at the--it happened
right at the wind farm shortly after commissioning
that's right near the wildlife refuge.
And people were driving by for several weeks going,
you put up this thing, it was super controversial,
why aren't they turning? And they had a problem
with their transformer. So there was nowhere for any
of the energy to go so they turned it off. Yeah?
What is the role of so-called rare minerals
in the action of the turbine? There's a line about Chinese
virtual monopoly on the mining of such minerals.
That is a really good issue. As we moved into the type
four turbines, particularly the most advanced ones that
had the most speed control, and also for the motors that
are used in hybrid cars for example, it really became
valuable to use the permanent magnet machines.
Let me give you a little history.
So, permanent magnets were kind of starting to be used
in the '50's with some material called alnico.
They didn't work that great and they're pretty expensive
but then it got a new material called sonarium cobalt.
Worked a little better, still pretty expensive.
Then General Electric and also a Japanese company
called Sumitomo got--dually got patents in 1983 for
something called neodymium iron boron
which is a mouthful. In the industry,
we just call it neo. And they - it was much better,
both in the magnetic capabilities and the fact
that it was--it could heat up. And they started charging
quite a lot for it even though it was less expensive than
the previous materials because they knew it was more valuable
and they would trade off selling less of it for
making much more profit. Well, the Chinese came to the
rescue and they're doing the same thing again but we won't
call it coming to the rescue. They took the material and
they didn't care that these two companies happened to have
a patent on the stuff and they just started selling it
on the market at much lower prices and they crashed
the price about 80% so then it became really affordable
and everybody started using it and then they realized how
valuable this stuff was and now the Chinese have sort of
recognized that, we could sell you this stuff that comes out
of the ground or we could take it out of the ground,
we could smelt it, we could turn it into a product,
we could build motors with it - wait, we could build a
full wind turbine for you and we could capture all that
value at and all that labor. I'd rather sell you a turbine
for three million dollars than the ore that would go into
it a turbine for, you know, handfuls of thousands.
And that's what's going on. That's essentially the
history of it. What's the role?
Where is it going from now? There's a political side
to that that I can't answer. The technical side is that
designers of this sort of equipment, both the hybrid
vehicles and the turbine generators are concerned.
They don't need to use permanent magnets, they can use other
machines but it will take a big step in innovations
to make other types of machines work as well.
So, that work is beginning. So, yeah.
You were next, sorry. >> There's been a certain amount
of concern about infrasound generated by these
wind turbines. Some people have even claimed
that there is something called vibroacoustic syndrome
which affects the human body if you're exposed over very
long periods of time. What's the status of that and
are there design attempts that are made to try and
avoid this problem? >> Okay, preface to my answer:
I'm not a physician and I am parodying reports that I've
read and I'll also provide the disclaimer that my source
of information is all from the American Wind
Energy Association, who is a proponent of wind.
But what is claimed to be independent analyses by both
sound engineers and doctors working together is that the
final conclusion when you get through that VBAS syndrome
and so forth is that, first off, there's about two or three
percent of the human population that's very sensitive to noise.
And there are about that same percentage of people
who are sensitive to wind turbine noise.
So the conclusion I'd draw is if you're really sensitive
to noise, you're going to be really sensitive
to wind turbine noise, or train noise,
or traffic, or whatever. As far as that syndrome goes,
I do understand the American Medical Association
or whatever bodies exist to formally recognize the
existence of a syndrome so the diagnosis can be made
have roundly refuted it. And it's proposed by one
doctor in New York, I can't remember her name, that's it.
Dr. Nina. And she's got all kinds
of what I am told by biology type people
is whack-job science.
(laughter)
That's, I think that's a technical term, I don't know
if the medical community uses that but it's just--she's
roundly, I don't know if she's discredited, just not
believed in her science. She spends more time talking
to lawyers than other physicians is what I understand.
Yes? >> What is the comparative cost
for this system compared to another cost such as coal?
Oh boy. Okay, cost.
Well there's two ways to look at that and that is installed
cost - what's it cost to build it?
and cost of energy, okay? Installed cost for wind turbines
varies around, at one point, it was as low as $1,000
per kilowatt or $1,000,000 per megawatt - megawatt is
about the scale of a turbine. Coal right now, and it has gone
up as high as $3,000, and that was really in 2007
and '08 when there was a real commodities bubble and
concrete was more expensive, steel was more expensive, and
copper was way more expensive. Coal right now is
being quoted at $5,000 for installed capacity.
So, coal is very expensive to install right now.
A lot of that has to do with permits and a lot
of the environmental, I don't want to call it
remediation, but what you have to do with the flu gas, okay.
Cost of energy, I don't mean to pun, but coal is dirt cheap.
And you almost can't beat it for price.
I mean, nuclear can beat coal because uranium is even more
dirt cheap, I think you'd call that rock cheap.
(laughter)
But you know wind can, and the factor of what wind
costs is how much you spend and how much can you get out.
The cost of energy for one and a half megawatt turbine or
say a farm of 100 of those in Wisconsin could be a whole
lot higher than here in Wisconsin than it would be
in North Dakota, because you're getting maybe 80% more
energy out of it for that same investment.
One of the things about renewables is that -
this is a little hyperbole - but all the money is up front,
not all of it - there's a little bit of it,
operation maintenance costs for spare parts and having guys
climb up--or gals, climb up and torque the bolts every,
you know, year. Stuff like that.
Respond to trouble. But basically once you've
spent the money up front, you're paying your debt service
and so forth. It, you know, it's free energy
after that so really a tradeoff on how you finance things.
I'm not sure who's next. I'll point to you and then
I'll get to you next, okay. >> We've got about ten years
of experience now with wind turbines.
Do we have any idea how long they will last that it's
estimated lifetime, 40 years, 60 years?
The kind of the warranty claim by most of the turbine
manufacturers is somewhere in the order of 20, 25 years.
We actually have 30 years of experience with wind
turbines, not the megawatt-- multi-megawatt scale,
but I mean I've been up in San Gorgonio by Palm Springs
and I actually went up to the wind farm there, because I'm
kind of a wind geek, climbed the mountain, saw them,
and they're up grinding away and they're running
after 30 years. Some of them aren't but
they're lasting quite a while. And I have to say, I think that
the designs are considerably evolved from 1980 so I'd say
25 years is a very safe bet and perhaps longer. Yes?
I noticed a wind farm that's on East West tollway
in Illinois, that's between the -- and 39.
Okay?
(inaudible)
I don't know. I know it has Vestus turbines
but I don't know who owns it. Sorry. There was someone back
there, I said you'd get next. There you go, I'm sorry.
It's sort of a financial motivation question.
In the nuclear power plants, the township around the plants
has no property taxes, so there's real motivation.
There's a story about a Danish island some years ago
that had resistance with turbines until surrounding
folks all had a financial benefit from it.
Is there a movement or a thought in the U.S.
to rather just have that farmer perceived income than
everyone in that area receive income from it?
Well, let me summarize. The question is:
does money make problems go away?
(laughter)
Here in the United States, we have less planning to
our economy than in Europe and so, you know, that sort
of socialized benefit and socialized cost is more common
there whereas--you know, this country is really 50
different countries in terms of rules and so forth and
developers here and utilities will do whatever they can get,
you know, if we can get Farmer Brown to take it and
Farmer Smith doesn't like it but he's not going to cause
trouble, then he doesn't get any money.
Now the township will get payment in lieu of taxes
because there is property and they do claim to have the
authority to take tax on property.
So they do get some revenue in lieu of property taxes,
that happens. I'm not sure how I could
compare it--wind farm to nuclear power plant.
I could tell you that the revenue stream on a 1,000
megawatt power plant--nuclear power plant is going to be
enormously bigger than on any wind farm
that's been built yet. So there's more money
to throw around essentially. So that's my kind of answer,
non-answer, sorry. Please.
How noisy would one of these things be in my backyard?
Well, you wouldn't want to put one of these
in your backyard because even though it's very, very rare
for them to fall down, they fall, they're, you know,
500 feet tall and with the right, you know,
angle and wind and stuff, they might hit 750 feet away.
So you'd want it a little ways away from your house.
Having said that, we know that sound is
inverse square so the farther you are--double the distance,
one-fourth the sound pressure. So, typical sound level
requirements at people's homes is 50 decibels, sometimes 55.
That's actually softer than my voice right now.
However, it seems that the sound issue and this is a
technical issue, although I'm not an expert, is really
coming into somewhat of the frequencies of the sound but
the tones of the sound, not just the sound pressure,
not just the power of this sound.
And we've worked very hard to make the power of this sound
- somebody asked earlier are turbines doing--are wind turbine
generators doing anything to mitigate that?
And the answer is yes. There are ways of controlling
it so that you spin the blades a little bit slower in a
given wind and you make it less noisy but you're
giving up energy. So it's possible to program
a turbine to - and you can do it on the fly,
as the turbines are working. You might change to a sound
reducing mode in the winter, you know, at night time
because the sound travels easier or you might do it
at one sight where there's a couple of homeowners
that are really upset. So you might say, well,
I'll make them happy, I'll spill energy, and make less
wind and hope that that helps. So that does exist
with turbine manufacturers. Also, I will say that part
of the siting prior to doing design is studying not only
how much wind can you get but then all the impact issues.
What's the visual impact? What's the sound impact,
you know? There's the birds thing -
I call it the birds non-issue. But go ahead, one more--was
there someone else back here? I'm sorry, it was
you and then you. >> I read that in Sunday's
paper, that the Governor is proposing that the distance
between towers be quadrupled from what the law currently is.
What's the reason for increasing distance?
Well, actually the proposal is to--well, increasing the
distance between turbines is not what's being proposed.
The distance between turbines is set by the planners that
know how packed they can put it before they start to
interfere with each other. What the proposal is,
is to--is the setback from a property line.
So, if we're going to build on your property and your
neighbor is over here and there's a line right here,
we have to be 1800 feet away, which is quite a bit more
than it used to be. I don't have any technical
reason why that should happen. Rob and then you?
Two part question. One is there's been some recent
reports about climate change and changes in worldwide
wind speed and I'm curious if there's any forecasting on
that in terms of the impact of the built base?
The other question, unrelated, is airplanes have pretty much
moved to wind-tipped vortices almost universally,
even small, small airjet type of things.
And I'm curious, I have yet to see one of these guys
with those and I'm wondering why that isn't beneficial.
Second part first. It has happened,
on small turbines. They have tried doing that and
it, you know, it adds some performance coefficient.
The reason it isn't happening on a large scale on all turbines
is primarily a cost issue. The structure of the blade
is really built around making sure that that thrust force
doesn't force the blade backwards so that it
hits the tower. That's how all the real
structure is being built now. If you add that tip out there,
you really change some of the force dynamics.
You can improve efficiency but, you know, it's a tradeoff.
The first part was when people are doing wind assessments,
they're looking at two years of data that's in the past.
They're predicting into the future for 30 years
for the benefit of a bank who cares only, really,
about the first seven years. So, I don't think, you know,
in a project by project, you know, I'm talking about
a wind farm project, I don't think that's being considered.
I think the climate scientists are really looking at that.
And I don't mean to make light of that at all.
I just, you know, pragmatically,
that's not something that you can really--what is this
climate change going to affect me in ten years
or not and the answer is who knows?
There was over here, sorry. And then you're next.
What's the maximum height you can get a tower and
can you have more than one blade apart?
Maximum height of a tower? How much money you got?
(laughter)
As towers get higher, they end up having to be
a considerably stronger which means thicker.
And so the second part of your question is can you put two
blades on the top? You know, like put a tower,
put a blade, put a tower and another one.
And it's never been done and I think it's partly because you
know we already have a system that works well.
You know, put one up, put one up, put one up.
The other thing is I don't think that it's
really well known to--really well known what the dynamics
would be of two blades swinging at once.
You've got this tower that's being pushed back by the wind,
you know, and the wind, so it's got this going on.
And then you got this, this gyroscope that's trying
to twist it and maybe moving this way.
Now add another one and it just gets more complex.
I'm not saying it can't be done, but I think that they've
looked at that as a barrier that's kind of not yet
worth producing--not yet worth pursuing.
And frankly, in the places that there's wind - all that
red that I showed - you got a lot of land.
If you want more turbines, you just talk to
the next farmer over. Or if you can be lucky and
get in West Texas you talk to one farmer who has
a million acres.
(laughter)
(inaudible)
How many turbines would you need to satisfy
all the Americans demand? I don't really know and it
depends on what turbines there would be but I can tell you
that while turbines are good in that they're creating
clean energy and then, you know, there's the whole
creating jobs locally and all that, there are some
electrical characteristics of turbines that make them--
presents challenges to the grid control.
So the kind of conventional wisdom is that maybe we can
get to 20% wind. Quite frankly, I think that
it'll be a challenge to get to 10% wind but much above
the 20% wind and you go into wild power swings.
This happens in Denmark when they're quite literally
at 150% wind. They're producing more
power than they use. The only way that they,
their power systems survive is Germany.
So they're just pumping out lots of power to Germany
and Germany is providing the support, the real solid grid,
so if Denmark were cut off, it would go in that state
and all the lights would go out - and on, nothing on, and then
out, you know, it'd be kind of crazy.
Where was the next one, I said. You, thanks.
Is there a significant sound difference between
the two bladed turbine and the three bladed turbine?
Yes. Two blades louder. And the very few number of
one bladed turbines that got built, some Italian company,
were really, really loud and it's basically because the tip
is spinning so much faster. Okay, one more question.
I saw this hand over here and we can talk afterwards
if you want. Yeah?
If there is enough wind to make the turbine go around,
do they sometimes shut them down because there isn't enough wind
and then use energy to get them up to speed again or is that
only some types of turbines? >> There used to be turbines
that required power to start. Turbines aren't manufactured
now, that I know of, that do that.
When wind speeds drop off, they control down,
they coast to a stop, they sit there,
they turn their blade into the most aero dynamically
efficient angle so that they can catch the winds available.
They will--they essentially won't start moving.
They can't overcome the torque that the machine naturally has
until they get up to that three or four
meters per second. They slowly spin up, they're
being driven by the wind - they're not being driven by
a motor and then the system synchronizes and clunk,
the circuit breaker closes and power's coming out.
Only a little bit, but that's how it is.
I'm told that we're out of time and that's
all the questions. If--I'll stay for
a little while longer if you want to talk.
(applause)