As a society and individually, we use energy every moment of our lives to improve our quality of life. Energy 101 will develop the big picture and connect the details of our energy use, technology, infrastructure, impact, and future.
Renewable Electric Power Technologies
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Energy 101: The Big Picture
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Electric Power Technologies
This module explores topics in Power Plant Technologies and Carbon Emissions
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Dr. Sam SheltonProfessor Emeritus
Woodruff School of Mechanical Engineering
Dr. Richard A. SimmonsSenior Research Engineer & Fellow
Strategic Energy Institute
Hello. We're on electric power technologies, and
we covered coal and natural gas and hydro. And now, we're looking at other renewable
electric power technologies other than hydro.
Hydro has been around for probably 100 years.
It has been around 100 years. So, now we're looking at other renewable
electric power technologies, mainly wind and solar.
So what about wind turbines as electrical renewable energy?
There the, they, of course the, they have a rotor that is rotated by the wind and
generates electricity, and we extract the kinetic energy from the wind.
There's been a tremendous growth in wind energy, and it makes up a, over, over a
between 1 and 2% of our current electrical needs.
All of the US wind farms are on land, such as is shown in, in this picture right
here. The, most of them are out in west Texas
and in the midwest out in the desolate areas of the US where and, where there's
great wind. It turns out that Europe has about 50
offshore wind farms that are out in the oceans, close to the shore.
So, I wanted to just mention those in passing.
There, there's a lot of potential there. But the first one in the US that's been
permitted is up in Nantucket Sound Massachusetts.
It's been about 10 years since the, the developer of that has been trying to get a
permit to build a wind farm out in the Nantucket Sound.
And it, that permit is now held by the developer.
There are also several proposed wind farms along the Atlantic coast off of New Jersey
and that area. Virginia also.
So it's, it's it, they, there's better wind off the shore than on land.
And significantly better, and it doesn't have to be much better in order to produce
a lot more power, as it turns out. And the other advantage to it is that it's
closer to the large electrical users, that being the large cities.
As I've said, most of the land wind farms are in the midwest, and there are not many
people living in the midwest, so they don't need much electricity out there.
So, they have to put transmissions lines in to get the power to the big cities like
Chicago. And, or, or Los Angeles in order to get it
to the user. The good thing about the offshore wind is
that they're close to the shore where the big cities, and New York City obviously,
the prime example is, that uses a lot of electricity.
Now, the cost. I mentioned is, the wind is better.
So that you get more power from a individual turbine.
But the cost to put it out there is higher because of the water and the insulation
and the maintenance issues with maintaining them offshore in the water
versus in, on, on the land. The major components of the turbines, of
course you have the rotor and over here that's turned by the wind.
And you have a gearbox and the gearbox to the shaft comes in, the rotating shaft
comes in. Comes in to the gearbox, the gearbox slows
the speed down and turns the generator to reduce the electricity.
The, the gearbox is a major component, a major cost component of the wind turbine.
And the reason for that is, is that the rotor only turns about 10 or 15 rpm's
revolutions per minute. You see that's, that's pretty slow that's
one time every 4 seconds or so. But if you turn the generator that slowly,
then you're going to have to have a very large generator.
The slower the generator is turns, then the bigger it has to be, to produce the
same amount of power. If you have a high-speed shaft and a
high-speed generator, then the size of the generator is smaller in order to generate
the same electrical power. So it, this is a major technology issue.
The, the speed comes in at about 1500 in R, 15 RPM and goes out at about 1800 RPM,
so the ratio is over 100 to 1 in general. And that, that's a major component that we
don't hear too much about. But as I mentioned, the wind causes the
rotor, or rotate the hub. And it's just like an airplane wing,
except in reverse rather than the propeller adding speed to the air coming
over the propeller it, it takes energy from the propeller.
Excuse me, from the air. And to, and turns the, the shaft.
The blades, actually, the, the pitch will twist.
So the blades twist. And, in order, depending on the wind speed
that's the main thing. The maximum efficiency and be able to
extract the most energy from the wind which the ideal pitch varies with the wind
speed in order to make the genera, make the rotor extraction of the kinetic energy
from the wind work it is optimum rate. So, it's a very sophisticated technology
and it's all automated. It senses the wind speed and decides for
what pitch it should need and what RPM it needs to be rotating at.
And bears it in order to stay on that optimum.
Moving to solar, there are basically two kinds of solar, photovoltaic
installations. One is the, what I classified as the
distributed, or example of the distributed solar power, that's generally located on
homes. And here's one, I believe we've seen this
picture before. The solar panels are located on the top,
roof and the sunlight hits it. And due to the solar state phenomena,
converts the solar energy to electricity. You've got to watch out for shading and
you got to point the, the modules in the southern direction and tilt it upward.
So that's one, one example of solar photo tags that we see a lot.
But another one is the central solar photovoltaic farm.
And in that farm, you, they're very large, it's exactly the same panels as are on the
roof, but there a lot more of them. And the as you scale things up, things can
get cheaper per unit. So, that generally is a little bit cheaper
per kilowatt of, of peak electricity that they can be generating.
Then on individual residences where the installation is more difficult, the wiring
is a lot more to each of these distributed systems.
So, they're pluses and minuses to each one of them.
And but they're getting to be more and more solar photovoltaic farms built by
utilities, since they like to add large centralized facilities like their power
plants. That's what they're used to and used to
building. This is another this thermal technology
that we just talked about, solar thermal. Excuse me, solar, photovoltaic, but this
technology is one that's been around awhile, and it is a trough, it's a
parabolic trough. It's linear and there's a pipe that runs
on the, right along the focal point where the, the sun that comes in and hits the
reflector is focused on. And concentrates it and generates a high
temperature in the fluid flowing through the pipe.
And carries it to a central boiler that is just like the coal boiler.
Except, again, the steam is boiled with a hot fluid coming from the, the fluid that
is heated by the solar energy. And this reflector rotates around with
time of day and depending on how high or low the sun is, and on the southern
hemisphere, if we're in the northern hemisphere of the world.
So, this is one that, that you don't hear too much about but there are significant
number of these out in the, out in the west and deserts.
Even in the US. This, this is a concentrating solar power
plant. It's the same principle as the trough
concept. Except in this case, we, we have mirrors,
hundreds of mirrors out here. And this covers like maybe as much as
hundreds of acres that's all, each one of these mir mirrors track the suns in a
manner so that it reflects the sunlight up to the, the tower.
And again, ste, water is pumped into this tower and all that solar energy is
concentrated on that. A tube that's carrying the water and it
boils the steam and goes through a steam power cycle just like the coal fired power
plant, except the heat source is not combusting in the coal, but the pipe
temperature is generated by the solar energy.
So it's a, it I think I covered all the points here that I have listed.
So, those are the solar power plants and the technologies that we have.
And we, that pretty well covers the general technology of the dominant
electric power technologies that we use to get all of our electric power.
Thank you.
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