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Holle, Champions of servant leadership, science, technology, engineering, math, all coming up right now on Alabama STEM Explorers.

Hi.

Welcome to Alabama STEM Explorers.

I'm Mitch, and I'm here today at TVA natural gas plant with my new friend, Mr. Mark.

So tell me, what are we going to be doing today?

Well, Mitch, today we're going to learn how a natural gas plant operates, generates and makes electricity for the valley.

Awesome.

Well, let's start with what's going on in this room.

What are all these computer screens for?

That's a good question, Mitch.

So if you would look at these displays, these are called human machine interfaces.

Okay.

And there are what the operators use to control the natural gas plant.

They monitor temperatures, pressures and electricity, which is the units of measure or megawatts.

Okay.

So just tell me more about all that.

So at the Tennessee Valley Authority, this is the Colbert combustion plant.

We have 11 units, 11 natural gas producing units that generate electricity.

We're called a peaking facility.

So the peaking facility, we operate at peak times when the load demand is the most.

We have three of the newest, most efficient units in the Tennessee Valley right now, units nine, ten and 11.

They were commissioned on July the 27th of 2023.

So when the operators are operating these machines, they need to know what pressure I'm operating at, what temperature am operating it, what the natural gas pressure is and what the megawatt output is.

So all these parameters are fed into this HMO, the human machine interface, and the operator uses that information to make adjustments as necessary.

Okay.

So tell me about like how like the operator would make adjustments or how the operator would manipulate anything.

And so the entire system is controlled from the balancing authority, which is located in Chattanooga.

So in the balancing authority request that Colbert states nine through 11 come on line, they make a phone call to the dispatch line we have here at the site and the operators begin to start the units.

And it's important to monitor these temperatures, pressures megawatt outputs to ensure that the the unit is operating within the design parameters.

And this is for safety reasons and also for efficiency reasons.

The operator can make adjustments to either one of those pressures, temperatures as needed.

But for most of the park it is controlled by a control system we call the Mark 60.

Okay.

And it's very simplified.

The operators are there to respond.

If something were to go wrong in the March 60, such as an alarm coming in, a unit failed to start a pump, failed to operate.

They can see all that from the HMI and they would make those adjustments as necessary.

It would basically let them know that, hey, there's a condition out in the plant.

You need to go out there and respond to it.

So what exactly is the mark 60?

The mark 60 is General Electric.

That is our main supplier here at this side of gas turbines.

And it's their control platform.

You would you might equate it to a very advanced PLC Programable logical controller.

So what is the advantage of like a natural gas plant, a natural gas plant such as this one here, carbon combustion turbines, There's two primary managers.

One of them is we are a fast start site.

We can be online producing electricity in 11 minutes under emergency conditions.

We generally start the plant in 17 minute profiles.

The other advantage to a natural gas plant is the cleanliness of the exhaust Our emissions.

Natural gas burns very clean and our emissions are much better for the atmosphere than some other types of technology that are used to produce electricity.

So explain to me exactly how the natural gas plant creates the energy That's the great.

Let's go take a look at that.

All right.

All right, Mitch, before we go on our tour, the first thing we need to talk about is safety.

I'd like to give you some personal protective equipment.

There's a hardhat for your head in case we bump into anything while we're out there.

But we're not going to.

We're going to keep our eyes on our path.

Safety.

Safety glasses are always required when we're out in the plant and also like to issue some hearing protection, protect us while we're out there.

Okay.

Sounds good.

So tell me about, like, what kind of jobs you have here and what kind of stuff that people do.

That's a good question, Mitch.

This plant was commissioned in July of the 27th of 2023.

During that construction process, we had a labor shortage.

We didn't actually have enough qualified people.

We made it through the job and we met our schedule on time.

But one thing we found out is we needed more people in the field of we needed more electricians, we needed more machinist, boilermakers, pipefitters, ironworkers.

A lot of people aren't aware that these skilled jobs are available not only in the Tennessee Valley, but all across America.

And they pay very well.

Some of those jobs pay in excess of $100,000 a year.

So I would very strongly encourage someone to get involved in those craft skills.

Yes, we use managers.

Yes, we use engineers, but a lot of people are unaware of the other types of skill sets that are available and can work at a gas turbine.

So what are some of those jobs at this plant?

They're called combustion turbine technicians and they all have a background of an electrical background, an operations background.

Their college education qualified them to enter into these training programs.

We also have machinist, we have pipefitters, we have electricians, we have engineers.

And all of those jobs have a specific responsibility here at the plant.

Awesome.

So you want to go have a look?

Yeah, sure.

Let's go.

All right, Mitch, this is where the natural gas comes into the planet.

Carbon combustion turbines.

You see over here.

These are inlet filters.

Okay?

These one filters.

And that's the whole thing.

The filters are the taller canisters over there.

You can see them.

They clean the gas, remove any impurities, remove any solids.

It's a pretty clean gas already, but it comes in through those initial filters.

Those are initial filter separators.

There's any moisture or non condensable in that gas.

It removes it also.

So before we move on, tell me a little bit about like where the gas comes from and that kind of stuff.

So this gas is supplied by our area supplier, Black Bear, natural gas.

Okay.

Black Bear natural gas owns this territory.

They supply TVA and they receive their natural gas from a network of suppliers, one of them being East Tennessee Gas.

There are network of suppliers all over America.

They receive natural gas from the Gulf, from the Plains and from the Northeast.

So tell me more about this machine over here.

Okay.

So what you have here is your inlet filter separators.

The natural gas comes through the inlet filter separators.

There's some regulating valves.

It comes in at 700 lbs per square inch.

That's the pressure, the regulating valves regulate it down to 500 lbs per square inch.

It comes through this single header over here to these gas heaters.

These gas heaters keep the gas at a temperature that is most efficient for combustion and for reduction of emissions.

They add to the overall efficiency of the plant through the combustion turbine process.

So on the gas heaters, there's actually a bath of water inside that heater.

And there's also it's a shell and tube design.

And so as the natural gas moves through those shell and tubes, that water is heated to a certain temperature and it heats in turn heats the gas and safely heats the gas.

So what temperature would that be?

It's 135 degrees Fahrenheit, and that's what the natural gas we'd like to maintain it.

So once it has that gas, like, what is the purpose of turning that into gas instead of just keeping it as water if you know your hot water heater?

Yeah.

So we're using the water as a medium to transfer heat in and there's a bunch of tubes in there.

That's what the natural gas flows through is those tubes, it flows into this top header, flows through those tubes, goes through that water bath is heated up, and then comes out this header here and goes over to the unit.

Okay?

So it's like, yeah, so it's less about the steam and more about the heat.

Right?

Right.

Okay.

Sounds good.

This is just a means of heating up the natural gas just and that adds to efficiency over here in the conversion process.

Okay, that makes sense.

Yeah.

Tell me more about that.

So let's go talk about how electricity actually reaches the 400,000 homes of the Tennessee Valley that this plant can serve.

Sounds awesome.

So behind me here, Mitch, is what we call main transformer number nine.

Okay.

The purpose of this transformer is after the natural gas is converted to heat energy, after the natural gas is converted to mechanical energy, after it's converted to electrical energy, it comes over to the main transformer that is 6.9 thousand volts coming into the low side of this transformer and 161,000 volts are going out the high side of this transformer.

It goes off here to the Switchyard where it feeds those 400,000 homes that I talked about, that this plant can serve.

That's crazy.

So tell me more about like the actual process of how that works.

Okay.

So how's electricity?

How's a step transformer stepped up Inside this transformer are copper coals.

Okay.

There's different sized copper coals on each side of this transformer and they're separated by insulating oil.

Okay, So on the low side, we'll call that 6000, 6900 volts.

Right on the high side, we've got 161,000 volts.

So so the electricity on the low side is induced through that all onto the coals of the high side the coals on the high side are much larger and they're capable of inducing a lot more current on the high side.

So that's why it's called a step up step down transformer.

So what are the purpose of all the fans?

So that's a very good question, Mitch.

I'm glad you asked that.

So as the transformer is generating electricity, especially in the summertime, this transfer from one coal to the other produces some heat.

And so as the transformer heats up, those fans are designed to kick on and keep it cool, cool it back down to its design parameters.

So a few minutes ago you talked about like three different types of energy coming into this area.

What's the point of having all of these different types of energy instead of just in a more a larger abundance of just one type?

Well, you're talking about our natural resources that we use to produce energy.

We have we have coal, we have natural gas, we have nuclear, wind and solar.

And so science has determined it's best to have a good collection of all of those different types of energy producing devices.

It's better for the environment if you rely on one.

When you lose that one, then that puts yourself in the position of not having enough available energy from that resource, because then you can completely, completely lose all of it.

That's correct.

So do they all go into the same area and then go into this machine over here, like this system over here?

Or does it all go in separately?

So the natural gas here, there are three different units, Unit nine, Unit ten and Unit 11.

And that's just the way that General Electric is our supplier for these gas turbines.

That's just the way they designed it.

Okay.

This is probably their most efficient design of this particular model that we have here on site and what makes it efficient.

The efficiency is tied into the combustion process.

And so I think now would be a good time.

We go over here and let's talk about how the natural gas is actually converted to natural gas, converted to heat energy, mechanical energy and electrical energy.

So.

All right, Mitch.

So as we start talking about how the conversion process takes place between natural gas and electricity, the first thing we want to talk about is this inlet system I have standing above us.

Behind us.

Okay, This is where air enters the gas turbine inside that housing that's actually called the inlet filter house.

There are hundreds of filters inside that filter house which clean the air as it enters and goes into the gas turbine.

So what exactly is like a filter do and what like how does it like filter air?

You know what I mean?

A filter is just like a filter on your air conditioner.

Or if you've got an icemaker with a filter on it, you got filters on all of your car.

This filter just traps debris as it moves across that filter and clean air goes out on the other side.

Wow.

Very good.

So are they all different levels or is that just one big like room that it's hundreds of filters at different levels all the way through there.

Wow.

We have to change those out on a regular basis as they become dirty.

So can they enter through any one of those little steps?

Yeah, we enter the inlet filter house.

We use this stairwell, we enter the different sections.

There's a one, two, three, four or five sections that we enter there and then can be like, Where does the air actually enter from into into the air.

So if you see these silver louvers, okay, that's where Inland Air's entering into the, it's underneath that each one of those silver louvers is where air enters the inlet.

Okay.

Wow.

That's, that's, that's crazy.

So after the air gets processed and that happens, where does it go and how does it get there?

So that's a good question.

So the air is used for the combustion process.

In order to have the combustion process, you need to have air fuel and an ignition source.

So the air is used for the combustion process in a natural gas fired turbine.

So it'd be good if we walked over here.

Let's talk a little bit more about how it goes from gas energy to thermal energy to mechanical energy in electrical.

So, Mitch, here's where all the magic happens.

All right?

Here's where natural gas becomes electricity.

Wow.

So I'll try to star stop and ask me any questions if you have.

All right.

Sounds good.

So behind us is a generator and that that big blue thing, the big oil thing, but it's also a starter.

Okay.

So right now the gas turbine is setting on turning here, meaning it's sitting there rolling real slow.

There's a turning here that's turning it real slow.

And what does the turbine actually look like?

Is it like a little windmill kind of thing?

It is like a job when we.

Okay, Yeah.

If you're picturing blades on a windmill, picture them gigantic and a whole lot of them.

That's what the gas turbine looks like.

Made of metal.

Wow.

The generator.

It can be used as a motor.

And so while this turbine is sitting here slowly spinning or what we call turning and we decide that the system needs to make electricity, we give it a start.

Command.

Okay?

When we give it a start command, this motor starts turning.

It's all in one shaft.

There's a shaft.

It goes from this in all the way to the other end.

Okay?

So it starts turning it and it gets it up to what we call firing speed.

Okay, How fast is that firing speed?

So these turbines, the maximum speed on these turbines is 3600 RPMs, and they fire down at a much lower speed of 500 R.P.M..

Okay.

So the purpose of the turning of the starting motor is to get it up to that firing speed of 500 R.P.M..

It can't get there through the combustion process alone, so the generator acts as a starter.

Now how big is the starting motor?

That's it, That's it.

Oh, the whole thing is the story That is the starting.

Wow.

It's out.

There are humongous coils of copper.

It's a giant motor electric motor.

So it's turning the gas turbine up to firing speed and it gets up to 500 R.P.M.. Then we start injecting natural gas into the combustion cans, which we have a picture of, which shows you earlier.

Yeah, I want to show you again.

So natural gas is fed into those combustion cans and there's an ignition source called spark plugs.

Okay.

And when the I told you about the Mach 60, which is the brains behind all this, when the marks exceed the control system, sees 500 r.p.m.

it and it sees fuel flow, it tells those spark plugs to ignite and they ignite the gas in those combustion cans.

So the natural gas is B is flowing in there.

And we also got combustion there from the intake, which I showed you earlier, which has all those filters in there.

So how exactly does the spark plug ignite, like with it, like a fire or as what is it if you've ever ignited a gas grill?

Yeah, it's got that little plunger you click and it makes a spark.

That's exactly the same thing that's used inside there.

Now, with that, like create like an explosion or is it like that's exactly what takes place inside of a combustion can is an explosion and are they, like constantly creating these little explosions or is it only like this continuous as long as gas is being fed, each one of those combustion cans, the this this combustion process, what you're describing as an explosion, which actually is what it is, this continuous, nonstop.

Okay.

And so the pressure built up from that explosion flows out of that combustion can into the turbine and that gas escaping that combustion process, because when something explodes or ignites, it builds up pressure inside that can.

Yeah.

And so now you've got this gas flowing through the gas turbine.

Okay.

The gas turbine starts spinning.

The starting motor is helping it continue to spin.

And then eventually it will get to a point where it's self-sustaining combustion.

The combustion process can actually keep this gas turbine spinning on its own.

Wow.

So it must.

So wait, the like the combustion is actually spinning the gas out of the road eventually, without even the start?

That's correct.

Okay.

I get what you're saying.

So here's the question.

Why does the starting motor have to be so large?

Because of the mass of the machine.

It takes a lot of horsepower to turn something this big.

This this gas turbine is really large.

It's extremely heavy several tons.

And so that's why the starting motor has to be so large.

It takes a lot of current to turn that motor and to turn the gas turbine.

And it's like electricity that flows through the motor.

So where does the electricity come from?

The motor.

So, you know, when we looked at the main transformer earlier and we told you that the main transformer when this unit is generating is generating 6900 votes, okay, That's 6900 votes goes to the main transformer.

Attached to that main transformer is what we call auxiliary circuits.

And auxiliary circuits are what we use out here in the plant to run motors, to run fans, to run for parts and to run this starting motor.

Okay.

So it's being fed from that main transformer.

There's also this building behind me as an electrical distribution building.

Okay, So what does that do?

And that electrical distribution building distributes electricity to all different portions of the plant through what we call breakers.

This starting motor has its own breaker, which controls it in the breaker opens or closes the control, the current going to it.

So you're you're right on money and how this is starting to work so okay so I'm starting to understand what's going on here.

So it goes to the starting motor which kicks up the fan, and then the combustion eventually will be able to make it run all by itself.

So where does the gas after it goes through that?

Like what is it called?

A gas turbine after it goes through the turbine, where does it go and what does it do that?

So the what we're gaining from this natural gas science has determined that it has a certain heating value.

And I know you use natural gas to heat your home.

You use natural gas on a charcoal grill.

So we know fast has proven that natural gas has a heating value.

So what we're wanting to extract from that natural gas is its heat content that's available.

So when it combust, it's at about 2000 degrees in the combustion heat, thousand degrees Fahrenheit.

That's that's a lot of pressure in that combustion can leaves it flows through the turbine, spins the turbine and there's actually a thousand degrees of heat loss across that gas turbine.

So how does that how does that happen?

That's through pressure loss as as the pressure starts decreasing.

And this mechanical rotation is also absorbing that heat energy.

It's we're converting the heat content of gas into heat energy and then the turbine converts it to mechanical energy, that exhaust gas.

Then when it's finished and it's used as much as there's much usable energy, potential energy, the finished, it goes through the exhaust.

Again, that big stack behind us.

Oh, that exhaust.

So while that's happening, this turbine is accelerating to what we call 100% speed.

Okay.

Remember, firing temperature was down here about 20% speed, and we wanted it to go to 100% speed.

So as it gets close to 100% speed, around 95% speed, they're starting motor kicks off.

Okay.

And it now is used as a generator.

So what is the point of having a like a type of energy that is more sustainable and is more better for the inverter, for the environment?

So TVA is extremely concerned about the environment.

Yeah, that's one of the benefits of having a diversified portfolio.

You are different types of plants that use different types of fuel to produce electricity.

Number one, we're not depleting our natural resources.

We're using a little bit of each one.

Number two, we're putting the most emphasis on one of the most cleanest forms of energy, producing natural resources, such as natural gas.

We even use solar, we use wind and also nuclear.

And those are both all good for the environment.

And that's one thing that the TVA is extremely heavily involved in.

That's one thing that's one of our commitments to the public also.

So one more question Where does this energy like where does it go to like Is it only in Alabama, in Tennessee, or is it in other states as well?

So it goes to what we would call the correct technical term is the grid.

The grid, all electricity from all power plants go to the grid.

The grid has changed a lot in recent years, mainly because of efficiency in your home.

We're using LED lighting now.

Your heating, ventilation and air conditioning systems are more efficient than they were 50 years ago.

Many electrical appliances are more efficient than they were 50 years ago.

Yeah.

So you're seeing an extreme change in the grid from, let's say, morning to evening because of these efficiencies that we've created.

When people come home and they start turning on their appliances.

Yeah, TVA has to respond to that drastic change in electrical need.

Plants such as these are what TVA uses to accomplish that they can be on line in 11 minutes.

They can start generating full load in 11 minutes.

That's right.

Thank you so much today for showing me all of this.

I've learned so much about natural gas.

Well, you welcome, Mitch.

It was good to have you.

I enjoyed the dialog we had.

If you got any questions, feel free to reach out and any time.

Thank you so much.

Come back whenever you like.

Awesome.

Thank you.

I'll see you next week on Alabama STEM Explorers.

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Alabama STEM explores is made possible by the generous support of the Holle Family Foundation established to honor the legacy of Brigadier General Everett Holle and his parents, Evelyn and Fred Holle.

Champions of servant leadership.