Hello, back to Energy 101. And today we are looking at electric power
plant capacity factor. This is another major characteristic we
need to study, and be aware of when we're dealing with utilization of electricity
from the grid. And essentially, I don't know, 99% or
more, of our electricity comes from the grid.
That's the, basically a pool that has many power plants feeding into it.
Renewable energy photovoltaics, renewable energy, wind generators hydroelectric
dams, nuclear coal plants, gas plants, they all feed into the same grid.
And then at the other end, we pull out some electricity and the, the power plants
are turned on and off, and up and down, to meet our demand.
So but the demand varies. And so, what does the demand that's placed
on the grid, that the utility servicing the grid, and managing the grid, has to
deal with. Well time of day is an obvious one.
It, the peak demands, peak electricity usage is during the day.
And the lowest is at night. Two, three o'clock in the morning, most
factories are closed down, office buildings are closed down, homes are
closed down, people are asleep, and so the electricity usage is low.
Temperatures are low, by the way, and therefore even air conditioners are, lower
than the daytime, in the South, for instance, summertime.
So the air conditioners are unloaded even. But they all, it also changes by day of
week, that you might not think of at first, because weekdays, Monday through
Wednesday, have a higher demand, and have a different profile than weekends,
Saturday and Sunday. So, the, utilities have to be prepared to
operate differently on Saturdays and Sundays, and weekend days, than during the
weekdays, Monday through Friday. But they also vary may, in another major
way, and that is over a longer term, by seasons.
The Winter and Summer, have a higher demand than the Fall and the Spring.
And of course the reason for that is, the Fall and the Spring have a low heating
need for the space heating, when the temperatures are, are 70 degrees, or the
are fairly comfortable outside, that we have to provide less space heating for our
buildings, and our homes, than we do in the Winter.
And in the Summers, we have to provide air conditioning, in the Summers, for space
conditioning. Fall and the Spring, we don't have to
supply as much air conditioning. So, you have variations, short term
variations, from hour to hour in the day, daily variations from day of week, and
seasonal variations with Winter, Summer, Fall, Spring.
So the su, utility managing the grid, has to deal with all of these ups and downs,
and be able to meet the highest demand that people ask for, when they turn
something on, and they also have to throttle things down, when the dam, demand
is low, because there's no electrical storage system.
Electrical storage is very expensive and it isn't commercially viable at this
point. Hopefully it will be in the future, but
electricity can, is, can only be generated if people use it.
So everything's gotta match up. Let's, talk, look at this a little more
closely, and before we do that, we need to look at some definitions.
Power capacity of a power plant, or a fleet of power plants, either way, is the
maximum steady power production capability.
Maximum being the running wide open as they're designed to do.
It's not like the car trying to run it wide open at a 120 miles per hour, and you
probably can't do that very long before you damage something in a lot of cars.
But these are, this is industrial equipment that is designed to operate with
maxium power, rated power, in a, steady state, for days, or months on end.
That's the maximum, capacity, or what we call the power capacity.
Now that's like speed on your speedometer. In other words, it's measured in Mega
Watts, which we denote by MW, and we or Kilo Watts, which is denoted by Kilo
Watts. Of course, a Mega Watt is a million Watts,
and Kilo Watt is a 1000 Watts. And that's the rate at which we're using
the energy. Like miles per hour on your, in your car.
And it's the, we denote the maximum capacity, that the power plant, or the
fleet of power plants, if it's to look at all of them feeding into the grid, we
denote that by MW, capacity, subcapacity, or Kilo Watts of capacity, just depending
on whether you want which units you want. Ones just a thousand different than the
other. So that's the power capacity that, and so
and, that needs to be of course higher, a little bit higher, than the maximum demand
that the system will ever see. Otherwise we have blackouts and brownouts,
and equipment gets overloaded and the system falls apart.
But, another definition, that we'd like to look at, is the electrical energy
production. That's comparable, using the speed analogy
on, in a car, to the miles analogy. If the power that we're using, times the
time we use it, that gives us the energy used, that determines how much fuel we've
got to put in and how long we have to run the plant, and how hard we have to run the
plant. So in other words, it's the electrical
energy used typically, we always say, over one hour.
So it's measured in Mega Watt hours, MW hours, or Kilo Watt hours, KW hours.
And that gives us the amount of energy that is used over some period of time.
And for, pow, Capacity factor, we generally look at a whole year.
And so the, the annual load factors determined by the looking at the annual
electrical energy production over years, denoted by Mega Watt hours per year, or
Kilo Watt hours per year. Typically Mega Watt hours per year,
because there are a lot of Kilo Watt hours that are produced over a year, even by one
power plant. So those are the basic definitions.
Moving, further on definitions, what are the, the capacity factor, which is the
whole point here, in discussing, is to find, as the Mega Watt hours that is
produced in one year, and this is for one power plant, if you looked at the capacity
factor of a power plant, or through a whole fleet of power plants feeding into
the grid. You can do it nationally, you can do it
for just a, a region or one utility that and, one part of the grid that has, is
under control by one utility. Then that is divided by the Mega Watts
capacity, that, that, that the power, power, plants are capable of, pro,
producing, if they run wide open, times 8760 hours.
Now whats the 8760 hours? Well, 807, 8760 hours, is the number of
hours in a year. So, in other words, if the plant, the
denominator, is the number of Mega Watt hours that the power plant, or fleet of
power plants, could produce if they ran wide open, to, at rated maximum capacity,
for every hour of the year. So that's what the denominator is.
The numerator is, of course, the actual amount that is produced.
So that, the number is always less than one, due to the fact that the capacity has
got to be equal to the maximum demand put on the system, over the entire year.
And that many period, most periods of the year, and hours of the year, the demand is
going to be less than that. So, it's not producing, fully, every hour
of the year, so the numerator was going to be less than the denominator.
So, it measures electricity produced as a fraction of the electrical energy it could
have produced by running maximum, output every hour of the year.
So that's the definition of the capacity factor.
By the way, let me note here, that there's also a term that you, some of you might be
familiar with, called the load factor. And, in the load factor definition, the,
there's a small difference, hopefully small.
In most cases the meh, denominator is not Mega Watt capacity, but the peak load seen
throughout the year. And the power plant capacity needs to be
slightly greater than the maximum load at the system, or power plant ever sees
during the year in order to stay 10% higher.
In order to maintain control of the, and be able to keep from going unstable, for
stability purposes. So some nuances there.
But capacity factor, and load factor, are very similar, except the capacity factor
will always be a little bit lower than the load factor, because the used Mega Watt
peak demand during the year Rather than the Mega Watt capacity of the system.
So, let's look at an example there. Well, let's take a nuclear power plant.
Nuclear power plants, I picked that one because that one has the, largest,
highest, capacity factor. And take a large, two unit, typically,
they're built in thousand Mega Watt units, and if you take a two unit nuclear plant,
that has the capability of producing 2,000 Mega Watts on a continuous basis, that's
the capacity. And let's assume that they, you measure
the actual output over, of that plant over the year, and it was 15 million Mega Watt
hours. That's the actual energy is produced.
But it could produce how much? It could produce 2,000 Mega Watts times,
times 8,760 hours. That's the, what it could have done, but
it actually did 15 million. Well if you run the numbers out I believe
you get an 86% capacity factor. Well that's a high capacity factor, but in
fact, nuclear plants typically run about 90%.
And there's several reasons for that but that's, well number one it shows the
reliability, the maintianance. They're down for maintenance, around 1% of
the time. And that's scheduled maintenance.
You hopefully don't have unscheduled maintenance, particularly in a nuclear
plant, but you may have. As any plant may have some unscheduled
maintenance where something goes wrong, and that you weren't prepared for and
didn't expect. If you expected it, you replaced that
part, or did the maintenance during the annual maintenance period, when you take
the plant down for maintenance. So nuclear plants are pretty well
base-loaded. The fuel cost is very low compared to
fossil fuels. And therefore they can run them if you're,
they already got them built and they want to run them rather than running a coal
fired or gas plant, where they have to buy fuel for it.
So, but if you look at the US fleet as a whole, if you take the entire capacity, of
all power plants in the US, and add them together, and divide it and divide that
into the annual Mega Watt hours that are produced and used in the country, then you
come out with a 40 to 50% capacity factor. Now, what that means is, and this is my
whole point here, is that only about less than half of the US power plant capacity
is used at any one point in time. On, on the, on the average, excuse me, on
the average. Over the average of a year, we're
utilizing half of the, or less, of the power plant capacity.
Sometimes, it's 20, 30 percent. Other times, or a few hours, normally,
it's, like, 90%. But over average, so we had, it was only
40 to 50. So we got a lot of excess capacity, except
during the peak hours in the year. Which normally occurs during the hottest
afternoons, late afternoons, in the summer.
When there's a very large air conditioning demand.
That's generally when your annual peak will occur.
So, let's look at power plant dispatchings.
So, how do you, how does the utility that has this fleet of powerplants that they
can turn up and down, like throttle, like your accelerator on your car, which ones
do they throttle back, and which ones do they turn on and turn off when they don't,
don't need them? You got a big choice there.
So which half do you use, and which half on average do you throttle down, or turn
off. Well you turn on generating facilities
that are the cheapest to operate, in terms of dollars per, per Mega Watt hour.
In other words the, in, which, you already paid for the capital costs, and so you got
to amortize the capital costs over the year, whether it's running or not.
That's the fixed cost, it's fixed. The capital cost is fixed, so the, the
incremental costs in dispatching, if, if it gets about what the plant costs to
build, because you've already got money invested, and so you now deciding whether
to run it, or run plant, power plant one, or power plant two.
And, so in both cases you crank, you look at the dollars per Mega Watt hour to turn
it on, versus let it sit there and do nothing and, and that's the, basically the
fuel cost. So, typically the plants that are turned
on first, and turned off last, will be the ones with the lowest fuel cost.
Well, it's pretty obvious that the ones with the lowest fuel costs are the
renewable energy, because that's energy's free.
So, the wind, solar and hydro is used anytime it's available.
And that's, I mean, all you gotta do is, is look at the reality, and that is
typically what happens. There are a few isolated cases where
there's some grid limitations, and some contracts, that happened out in the
northwest a couple summers ago, I believe, where the grid became overloaded.
And coming from a certain region, and due to contractual obligations, they actually
turned off some wind farms, but that's a very unusual situation.
Basically in that same category, though, is nuclear, because, not only is the fuel
cost from nuclear very low, but also they're much more difficult to turn on and
off. You have to turn, turn them up and down
very slowly. It takes days to crank up a nuclear plant,
and turn it, turn it down, and turn it off.
So, you have to consider that. Another factor, by the way, and these are
second and third order effects, but the other factors that come into play is water
usage. In some cases, the minimum, they got
minimum water flows that the plant uses, and maximum water flows and things.
And depending on what's going on in the river, where they're dumping their, their
heat, if they are, then that can come into play.
But basically, the renewable energy in the nuclear run all the time.
It's what we call base load. Next come coal.
Because coal has normally been cheaper than gas.
And next comes natural gas plants. Now that's recently, in this year, that
has changed for the first time, in my 35, 40 year history.
That natural gas plants have been cheaper, or as cheap to run as coal plants.
And so they have actually shut down some coal plants before shutting down gas
plants. But, they, that probably won't last too
long, because gas prices are already headed back up, and coal is fairly stable
at this point. So, we expect it, that the old rule that
gas plants, or the natural gas plants are the first ones to turn off or turn down,
will, will be the, is has been, generally in the past, except in some unique periods
or in situations, and probably will continue over, over the, future.
So that's how we dispatch, our, the plants.
The coal an, the note, the coal and gas have switched depending on relative price,
and need to note that, because, you can, you can find examples right now that, that
is not the case. But in general, it's not, that, that is
the sequence used. And that, that covers the dispatching.
And the one reason that I wanted to do that is regarding, where do we get our
incremental load from? And it's a major characteristic of
electrical power that's fed into the grid, and we're going to discuss the, emissions
from electric cars, and so you need, you need to know something about where that
electricity will come from as you put in, put on one car additional electric car for
recharging onto the grid, or put a million of them if you got a, trying to determine
how much impact a tax credit will give for our subsidy to get a lot of, a million new
electric cars out there on the system and whatever.
So, that gives us the background, and one more important characteristic of the
electrical power plants, that we operate, and utilize, and depend on every day.
Thank you.