[upbeat music]
Good day and welcome to Big Bad Tech.
I'm your instructor Jim Pytel.
Today's topic of discussion is Energy and Power.
Our objective is to introduce
the two closely related concepts of energy and power.
We'll discuss the concepts they represent,
important differences between them,
the units used to quantify these properties,
and the means of calculating energy and power.
First and foremost, energy is not power,
and power is not energy.
If you continue to frequent this channel,
understand that I'm unusually firm about this distinction
so much so that one might say I'm a messianic jerk about it.
It will be of tremendous service
to keep this distinction in mind
because the misunderstanding
and misapplication of these two distinct
yet closely related concepts is unforgivable.
Although this lecture is introductory in nature,
I am blatantly and emphatically telling you to pay attention
as energy and power represent central concepts
for this lecture series,
and we'll come back to discuss these concepts
again and again and again.
One of the most effective ways
I've found to convey the distinction
between energy and power is using the analogy of money.
Money is energy.
If you've got a lot of money,
you can do a lot of things,
like buy a car, buy a house,
or pay a marching band to follow you around all day
and play songs that you request.
The same thing goes for energy.
If you got a lot of gas in your tank,
a fully charged bank of batteries
or a reservoir full of impounded water,
you could drive a long distance,
light a couple lights in your cabin,
or light up an entire city.
How you get that money or energy
is via one of two methods,
less powerful or more powerful means.
One, you could work a really poor-paying job
for a long, long time,
or, you could work a really well-paying job
for a short period of time and then just goof around
and take up an expensive hobby like horse riding.
If you take a look at the units, it all makes sense.
Your pay rate is power, and power is expressed
in dollars per hour or energy per unit time.
The units make sense.
To calculate how much money
you've earned at the end of the week,
multiply your pay rate by the number of hours you work.
Dollars per hour times hour yields dollars.
If you wish to calculate your pay rate following a task,
one would manipulate the same question
to solve for pay rate.
Take the sum of money you earned
and divide it by the time it took you to earn it.
Dollars divided by hours yields dollars per hour.
Finally, if you wish to calculate the number of hours
it would take to accumulate a certain amount of money,
you manipulate the same question to solve for time,
where dollars divided by dollars per hour yields hours.
What we've created is a very simple
three-variable relationship.
The concept of money is placed at the apex of our pyramid
as it should be for all good capitalist society
with pay rate and time side by side below it.
To solve for money, take pay rate and multiply it by time
because they're side by side.
To solve for pay rate, take money and divide it by time
because money is over time.
Finally, to solve for time,
take money and divide it by pay rate
because money is over pay rate.
This simple triangular
three-variable relationship is very handy,
and you'll find yourself using it over and over again
for a number of different concepts,
among them Ohm's law and Pascal's law,
two concepts that respectively govern
electrical and hydraulic systems
which we'll examine in great detail in the near future.
Let's now tie our monetary analogy
to our discussion of energy and power.
As with money and pay rate, the prime distinction
between energy and power is that of time.
Energy is the amount of work put into a system,
i.e., the amount of money you have in the bank.
Energy can take many forms,
among them mechanical, electrical,
chemical, and thermal.
Let's restrict ourselves to the analysis
of mechanical energy right now
where energy is measured in units of joules,
abbreviated with the capital J
where one joule is one newton of force
expressed for a distance of one meter.
Energy can be calculated as force times distance.
For example, 10 newtons of force
expressed for a distance of three meters
means 30 newton meters or 30 joules has been expended.
Power, in contrast, is pay rate.
Power is how fast energy leaves or comes into a system
or the time rate consumption or generation of energy.
Power is energy over time.
The SI unit of power is watt,
abbreviated with the capital W,
which is really one joule over one second,
i.e., a unit of energy consumed or generated per unit time.
The SI unit of time is the second
which hopefully doesn't necessitate explanation.
These definitions and units imply an important relationship.
If power is energy over time, energy is power times time.
I should remind you that the law of conversation of energy
states for any closed system,
energy can neither be created nor destroyed
and only changed in form,
therefore the terms consumed and generated
come attached with some important disclaimers.
It would be more appropriate to say that an electrical motor
does not consume electrical energy,
but rather converts electrical energy
into rotating mechanical energy minus losses.
Additionally it would be more appropriate to say
a wind turbine does not generate electrical energy
but rather converts the mechanical energy
of moving air particles
into electrical energy minus losses.
Regardless, the distinction between energy
being power expressed for a period of time,
and power being energy consumed or generated
per unit of time still holds true.
This important difference between energy and power
bounces off the skulls of many people,
and I consider it one of my highest responsibilities
as an instructor to force it through their skulls
with repeated aggressive hammering.
Power is energy per unit time,
and energy is power times time.
Graphically we can express this relationship
using our three-variable pyramid,
with energy at the apex
and power and time side by side forming the base.
To solve for energy in units of joules,
take power in units of watts
and multiply it by time in units of seconds.
If a watt is a joule per second,
units of seconds cancel,
and we're left with energy in units of joules.
To solve for power, take energy and divide it by time
because energy is over time.
Units of joules over units of seconds
yields joules per second or unit of watts.
Finally, to solve for time,
take energy and divide it by power.
Units of joules divided by units of joules per second
yields units of seconds.
For those of you with a calculus background,
you'll realize power is the differential
or rate of change of energy over time,
and energy the integral or area under the power curve.
For the purposes of this lecture series,
we'll mostly steer clear of differentials and integrals
and restrict our analysis
to the much simpler algebraic manipulations.
Let's try a couple simple illustrated examples.
Energy is power times time.
Let's say you use a 100-watt device
for a total of three minutes.
Three minutes is 180 seconds.
This device would have consumed 100 watts
or 100 joules per second times 180 seconds or 18,000,
or more appropriately 18 kilojoules of energy.
Power is energy over time.
Let's say 40 newtons of force
has been expressed the distance of five meters.
Energy is force times distance.
40 newtons times five meters equals 200 newton meters
or 200 joules of energy input into this system.
Let's say it took 10 seconds
to put the 200 joules into the system.
If power is energy over time,
this represents 200 joules per 10 seconds
or 20 watts of power.
Finally, time is energy over power.
Let's say a 500-watt heater has put 2,500 joules of energy,
or more appropriately 2.5 kilojoules
of heat energy into a system.
If time is energy over power,
this demonstrates that the heater
has been working for a total of five seconds.
The concepts and the units should make sense.
One great way of checking your work
for energy, power, and time calculations,
is to examine these relationships without numbers.
If energy is power times time,
if one had a device of fixed power
and increased the time span it was used,
the energy requirement should go up.
Conversely, if one had a device of fixed power
and decreased the span of time it were used,
the energy requirement should go down.
If your answers don't follow these observations
you're doing it wrong
and you need to perform a tactical retreat,
reassess your situation.
Let's try a couple more illustrated examples.
Consider a task that necessitates 500 newtons of force
be expressed a distance of two meters.
Consider a second task
which necessitates 250 newtons of force
be expressed a longer distance of four meters.
Which tasks requires more energy in joules to complete?
Energy is force times distance.
The first task necessitates 500 newtons of force
be expressed a distance of two meters.
500 newtons times two meters yields 1,000 newton meters
or 1,000 joules or more appropriately one kilojoule.
Similarly the second task necessitates 250 newtons of force
be expressed a distance of four meters.
250 newtons times four meters
also yields 1,000 newton meters or 1,000 joules
or more appropriately one kilojoules.
These calculations imply both tasks necessitate
the expenditure of equal amounts of energy,
which if you think about it, makes perfect sense.
Which task would tire you out more?
Carrying twice the weight half the distance
or carrying half the weight twice the distance?
Theoretically these tasks would be equivalent.
Let's now examine the various methods we could use
to accomplish a task necessitating one kilojoule of energy
of which we have three options.
Option one, a 500-watt machine,
option two, a human working at a moderate pace
capable of generating 100 watts of power,
and option three, a 20-watt sloth.
Which of these available options
will accomplish the one kilojoule task in less time?
It should be obvious that 500-watt machine
will be capable of delivering
the required one kilojoule of energy in far less time
since its power rating or energy per unit time
it's capable of delivering,
is much greater than the other two options.
Calculations support this supposition.
Time is energy divided by power.
One kilojoule divided by 500 watts or 500 joules per seconds
demonstrates the 500-watt machine is capable of delivering
the necessary one kilojoule of energy
in the span of two seconds.
Let's examine the other last powerful options.
Consider the 100-watt human times energy divided power.
One kilojoule divided by 100 watts, 100 joules per second
demonstrates the 100-watt human is capable of delivering
the necessary one kilojoule of energy
over a longer span of 10 seconds.
Consider the 20-watt sloth times energy divided by power,
one kilojoule divided by 20 watts or 20 joules per second
demonstrates the 20-watt sloth is capable of delivering
the necessary one kilojoule of energy
over a much longer span of 50 seconds.
Compare and contrast these results.
A more powerful device
accomplished the same task in less time.
A less powerful device
accomplished the same task in more time.
It makes sense.
In keeping with this observation,
consider the energy of a triple A battery,
a nine-millimeter bullet.
Which do you think has more energy?
Surprisingly a typical triple A battery
has much, much more energy than a nine-millimeter bullet.
Specifications may vary,
however, a typical triple A battery
might contain around 6,000 joules of energy,
whereas a nine-millimeter bullet
depending on your proximity of the muzzle
might contain only around 500 joules of energy.
Gun nuts chill out.
I am well aware of the differences
between full metal jackets, soft-points, hollow-points,
and fragmentation, frangible variance
and their associated lethality index and stopping power,
but just go with this 500-joule figure for now.
The difference between these two devices
is obviously associated with their power
or their rate of energy transfer.
Let's say the triple A battery delivers this energy
over a long period of one hour or 3,600 seconds
whereas the nine-millimeter bullet
delivers its packet of energy
over a much, much more rapid time span.
For the sake of argument,
let's say the bullet does so over 100 milliseconds.
Again gun nuts, chill out.
It's just an example problem in electronics class,
not a technical discussion in a Bass Pro parking lot,
so you have to forgive any ballistic inaccuracies
in the interest of forward progress.
Power is energy over time.
For the triple A battery,
it's capable of delivering 6,000 joules
over one hour or 60 minutes or 3,600 seconds.
This yields a relatively low power rating
of roughly 1.7 joules per second or 1.7 watts.
A respectively large quantity of energy
is slowly and steadily delivered over a long time.
The battery would be a suitable means
of powering a low-power device
like your calculator for a long, long time.
Let's now consider the nine-millimeter bullet.
It is capable of delivering 500 joules in 100 milliseconds.
500 joules over 100 milliseconds or .1 seconds
yields a much higher power rating
of 5,000 joules per second or five kilowatts.
No wonder bullets cause a trauma on impact.
A packet of energy is delivered very, very quickly.
This explains why it's a recommended practice
to power your calculator with a triple A battery
rather than shooting it,
although at times I'm certain you are tempted to do so.
Moving on, let's now examine other units
commonly employed in the discussion of power and energy,
namely the horsepower and the kilowatt hour.
First, let's examine the horsepower.
In addition to watts,
power can also be quantified in units of horsepower,
sometimes abbreviated as hp
where one horsepower equals 746 watts.
In the US customary system of units,
a horsepower also equals 550 foot pounds force per second.
As antiquated as this unit may be,
I still have the tendency to think in terms of horsepower
'cause it gives me an idea
if one can stop a device with your hand,
with two hands and a little sweating,
or if something will just rip your balls
out of your sockets if you ever get tangled up in it.
Long story short, anything stronger than a horse
could probably kill you,
and even a quarter of a horse
stands a reasonable chance of doing so
if it kicks you in a critical portion of your anatomy.
Let's try some basic unit conversions.
Consider a quarter horsepower of motor.
In units of watts, this motor would have a power rating
of 746 divided by four or 186.5 watts.
Consider a motor that delivers 560 watts.
In units of horsepower, this motor has a power rating
of 560 over 746 or roughly .75 horsepower.
Most likely this is a three-quarter motor horsepower.
Let's now try an energy, power, and time example
necessitating some intermediate unit conversion.
Consider a two-horsepower motor
being used for a span of three hours.
How much energy in units of joules will it deliver?
A two-horsepower motor would have a power rating
of two times 746 watts or 1,492 watts
or roughly 1.5 kilowatts.
Three hours represents a span
of three times 60 times 60 or 10,800 seconds.
Energy is power times time.
1,492 watts times 10,800 seconds yields 16,113,600 joules
or roughly 16.1 megajoules.
You'll note that for applications like this,
joules are tiny, tiny, annoying, and unwieldy units.
For this reason, numerous applications
make use of a far more convenient unit of energy,
the kilowatt hour.
Pay special attention to the kilowatt hour
since in my experience,
it presents one of the biggest sources of confusion
for those with difficulties distinguishing
between the concepts of energy and power.
The kilowatt hour is a unit of energy.
It is not a unit of power.
I know it has a kilowatt in there which is a unit of power,
but look at it, it is kilowatts times hour
or power times time.
I say again that kilowatt-hour is a unit of energy.
It is not a unit of power.
If you don't believe me,
unwrap each piece of the kilowatt hour
one by one and prove it to yourself.
If one k equals 1,000,
one kilowatt hour equals 1,000 watt hours.
If one watt equals one joule per second,
one watt hour equals 1,000 joules per second times one hour.
If one hour equals 60 minutes,
and one minute equals 60 seconds,
one kilowatt hour is 1,000 joules per second
times 3,600 seconds or 3,600,000 joules.
In summary the kilowatt hour is a unit of energy.
It is a unit of power, the kilowatt,
times the unit of time, the hour.
Energy is power times time.
The simplicity of expressing energy
in units of kilowatt hours cannot be overstated.
Consider a four-kilowatt solar ray being exposed
to peak sunlight for a period of four hours.
How much energy does this solar ray produce
in units of kilowatt hours?
Energy is power times time.
Rather than converting hours to seconds as we did
when calculating energy using units of joules.
We simply multiply the power in units of kilowatts
times the time in units of hours.
Four kilowatts times four hours yields 16 kilowatt hours.
It really is that easy.
If you wanted to go to the trouble,
which I have no idea why you would,
you could convert this to joules
where one kilowatt hour equals 3.6 megajoules,
and 16 kilowatt hours would equal 57.6 megajoules.
You know calculating energy
in units of kilowatt hours is astoundingly easy.
Oftentimes the wattage or power of a particular device
is directly specified in the device's nameplate.
All you need to do to determine
the energies of a particular device
is the number of hours you plan on using it.
For example, considering an 800-watt air conditioner.
To calculate the daily energy consumption
of this air conditioner,
simply multiply the wattage rating
by the number of hours you use it everyday.
An 800-watt air conditioner used for eight hours a day
uses 800 times eight or 6,400 watt hours of energy
or 6.4 kilowatt hours of energy.
If however you left the 800-watt
air conditioner on all day or 24 hours,
you'd be billed for 800 times 24 or 19,200 watt hours
or 19.2 kilowatt hours of energy.
Consider a 100-watt incandescent bulb
used for eight hours a day.
This bulb uses 100 times eight or 800 watt hours of energy
or .8 kilowatt hours of energy.
If you were lazy and you left it on all day or for 24 hours,
you'd be billed for 100 watts times 24 hours
or 2,400 watt hours or 2.4 kilowatt hours of energy.
Consider a more efficient 20-watt LED light bulb
used for eight hours a day.
This bulb would use 20 watts times eight hours
or 160 watt hours of energy or .16 kilowatt hours of energy.
If you left it on all day or for 24 hours,
you'd be billed for 20 watts times 24 hours
or 480 watt hours of .48 kilowatt hours of energy.
Compare and contrast these last two examples.
The 100-watt incandescent bulb
used five times as much energy
as the 20-watt LED light bulb
even though they operated for the same length of time.
It makes sense.
More power times the same time necessitates more energy
even though they are producing the same functional product,
namely light of a given intensity.
Be aware that I'm not so naive to suggest
that an LED will be sufficient for all tasks
requiring light of a certain quality,
let's say painting a picture
or some alone time with your imaginary girlfriend,
but I'm confident enough to say
that if you simply require light
in its most basic form,
let's say task lighting in a factory
or to light up your front steps
so you don't bust your ass falling down them,
it'd be foolish to use an incandescent bulb to do so
principally 'cause the long-term energy cost.
Additionally compare and contrast the usage patterns.
Any appliance regardless of type used for 24 hours a day
necessitates more energy than an identical device
used for only eight hours a day.
It makes sense.
Same power more time necessitates more energy.
This explains why it's a good economic practice to, one,
use efficient devices, i.e., devices that accomplish
the same task using less power,
and two, use these devices only when it's necessary,
i.e, don't leave a light on if you don't need it.
When you get right down to it, energy is money.
The more energy you use, the more you pay.
Nationally, price per kilowatt hour of energy
varies depending upon your location
from a low of around eight cents per kilowatt hour
in regions of the Pacific Northwest,
to a high of around 35 cents per kilowatt hour in Hawaii,
with a national average of around 12 cents per kilowatt hour
at the time of this recording.
An average house might consume
around 30-kilowatt hours of energy daily,
although daily energy consumption patterns vary widely
from the seven-bedroom McMansions of Salt Lake City
chugging 100 kilowatt hours a day,
whereas an efficient well-designed modern house
with a reasonable number of ecologically
and economical conscious people
might consume only 10 kilowatt hours.
Also if you're on a region characterized
by cold winters and temperate summers
like Maine or Wisconsin,
you might expect larger daily energy consumption
in the winter and less in the summer.
Conversely, if you're in a region characterized
by extremely hot summers and temperate winters
like Arizona or Southern Cali,
you might expect larger daily energy consumption
in the summer and less in the winter.
Let's just go with this average daily energy consumption
of 30 kilowatt hours per day.
Given this average price per kilowatt hour
and the average amount of kilowatt hours used per day,
it's easy to determine the average cost of energy per day.
12 cents per kilowatt hour times 30 kilowatt hours per day
yields an average daily cost of $3.60
and an annual cost of 360 times 365 or $1,314 per year.
Given this average daily energy consumption,
let's now take a look at the average
power consumption of a typical home.
If power is energy over time,
you might be tempted to think
that a house would steadily draw
30 kilowatt hours divided by 24 hours or 1.25 kilowatts,
but you would be absolutely wrong.
Some periods of a day necessitate
massive consumption of power.
For example in the morning when everyone's waking up,
taking a shower, cooking breakfast,
and getting ready for the day.
This brief period of high power consumption
is followed by a longer period of lower power consumption
when everyone's at work or school.
This period is then followed
by another burst of high power consumption
when everyone gets home and air conditioners,
stoves, washers and dryers
start chugging power in massive quantities.
Finally the day draws to a close
and the occupants of the house go to sleep,
only the water heater and refrigerator
continue to draw power.
Instantaneous power demand peaks and valleys
and peaks and valleys,
yet we can say there exists some average power demand
which happens to be around 1.25 kilowatts
such that over the course of a 24-hour period,
the house ultimately consumes 30 kilowatt hours of energy.
Those of you with a calculus background
will realize that the energy is the integral
or area under the power curve, i.e., power times time.
The instantaneous power curve
can be a little tricky to calculate,
so that's why the average is used.
If you squinch your eyes just right,
you'll note the overrepresented areas
in the early morning and late evening
are counterbalanced by the under-representation
or morning and afternoon.
If you multiply the average power figure
of 1.25 kilowatts by 24 hours,
you realize the energy or area under the power curve
is 1.25 times 24 or 30 kilowatt hours.
Don't get too stressed about the details
of this particular example just yet,
but rather think of the large point I'm trying to make.
Power is instantaneous whereas energy is consumed over time.
Power is the instantaneous rate of change of energy
whereas energy is power consumed over time.
Let's try an illustrated example of this concept,
focusing in on a single household appliance.
Consider a water heater
that over the course of one year or 365 days
is known to consume 4,380 kilowatt hours of energy,
given the price of 12 cents per kilowatt hour,
what's the annual cost of using this water heater?
Additionally what's the average power consumption
of this water heater?
Calculating the annual cost is easy.
4,380 kilowatt hours times 12 cents per kilowatt hour
yields an annual cost of $525.60.
Average power should be easy too.
Power is energy over time.
One year is 365 days, one day is 24 hours,
so one year is 8,760 hours.
4,380 kilowatt hours over 8,060 hours
use a power rating of .5 kilowatts
or more appropriately 500 watts.
You might reasonably think a water heater
continuously steadily draws 500 watts of power
and could be powered by a 500-watt generator.
This, however, is an average power figure only,
and totally misrepresents how an actual water heater works.
Water heater don't heat water continuously
but rather in bursts.
As a simplified explanation,
if water in the tank falls below a certain low value,
but heater is applied at full blast
until water in the tank
has risen above a certain high value,
after which the heater is completely turned off
and the tank's insulation, thermal inertia of the water,
temporarily hold it inside a specified range.
The result is a periodic full-on, full-off,
bang-bang style control that only on average
consumes 500 watts.
In reality we might expect the water heater
to briefly consume massive amounts of power
during the heat phase,
and then simply turn off during the rest phase
until the temperature in the tank
falls below the reset value.
Obviously water usage patterns
would influence this periodic cycling.
As a simplified illustration of this process,
let's say a four-kilowatt water heater
operates in a 12 1/2% duty cycle
where for 12 1/2% of 60 minutes or 7 1/2 minutes,
the four-kilowatt heater runs at full blast,
and the remaining 87.5% of 60 minutes of 52.5 minutes,
the heater is completely off.
What you'd experience over the day
is regular burst of four-kilowatt power demand
followed by an idle state.
If you summate the on times for a 24-day,
i.e., 24 times 7 1/2 minutes or 180 minutes or there hours,
it means a four-kilowatt device
has been used for a total of three hours
or a daily consumption of four kilowatts times three hours
or 12 kilowatt hours.
If the water heater did this everyday for 365 days,
it would consume 365 times 12 kilowatt hours
or 4,380 kilowatt hours of energy annually.
Additionally you'd need that minimum
of four-kilowatt generator
to power this water heater when it was on.
That generator only working 12 1/2% of the time,
and the other time it would sit idle.
Again those of you with a calculus background
will realize energy is the area under the power curve.
Rather than using instantaneous
periodic power burst however,
it's perhaps easier to simply use
the average power figure of 500 watts
over the 24-hour period
which yields 12 kilowatt hours of energy per day.
Moving on, returning to our discussion
of units employed when quantifying energy,
the kilowatt hour makes a handy unit
for most small scale residential applications.
However, if the application is smaller in nature
like a portable electronics device or sometimes batteries,
you might alternatively see units of energy
represented in watt seconds or watt hours.
Watt second is simply a stupid way of writing a joule
because one watt times one second
is one joule per second times a second which yields joules.
And a watt hour is a larger packet of joules.
If one hour equals 3,600 seconds,
a watt hour is 3,600 joules,
or more appropriately 3.6 kilojoules.
For example consider a storage battery
known to have an energy capacity of 600 watt hours,
theoretically this battery could power
a 600-watt device for one full hour
or 300-watt device for two hours
or 1.2-kilowatt device for 30 minutes
or any other combination of power and time
that ultimately yields a product
of 600 watt hours of energy.
This, by the way, is theoretical capacity only,
and isn't entirely true especially for high power demands.
As we demonstrated, triple A battery
is ordinarily limited to an extremely
slow rate of energy transfer per unit time, i.e., low power,
and can't be expected to deliver a high power burst
as with a bullet.
I suppose you could throw a battery at an aggressor's head
but I suspect that might only make them mad.
We'll examine battery performance characteristics
in greater details in later lectures.
If the application is considerably larger,
for example the daily and annual energy output
of a large generation facility,
you'll sometimes see figures
in the megawatt hour or gigawatt hour range.
Given your understanding of engineering prefixes,
you will note that 1,000 watt hours
equals one kilowatt hour.
1,000 kilowatt hours equals one megawatt hour.
And finally 1,000 megawatt hours equals one gigawatt hour.
Consider a single 50-megawatt turbine
inside a larger hydroelectric dam
that runs at full capacity for 24 hours.
How much energy does this turbine produce in one day?
Energy is power times time.
50 megawatts times 24 hours yields 1,200 megawatt hours,
or more appropriately 1.2 gigawatt hours.
If you wanted to put this in terms of kilowatt hours,
this would be equal to 1,200,000 kilowatt hours.
Consider a two-megawatt wind turbine
that runs at full capacity for only eight hours a day.
How much energy does it produce?
Energy is power times time.
Two megawatts times eight hours yield 16 megawatt hours,
which if you want to put it in terms of kilowatt hours,
would equal 16,000 kilowatt hours.
If you were to sell each kilowatt hour
at a wholesale price of five cents per kilowatt hour,
this means the turbine would produce 16,000 kilowatt hours
times five cents per kilowatt hour or $800,
meaning the turbine is effectively generating $100 an hour
every hour it's in full production.
No wonder such a high priority is placed
on the efficient operation, maintenance,
and timely repair of these machines.
Other questions I'm frequently asked about wind turbines,
why are they so big?
Why are they so tall?
Why are they painted white?
How many houses can a turbine power?
I think the last one deserves some comment
in this particular lecture.
The average dunderpate beebopping down the street
does not understand the difference between energy and power
and often uses these two concepts interchangeably.
You, however, understand the difference.
To make this a solvable problem,
let's assume the following.
We're using a two-megawatt wind turbine
that operates at full capacity for eight hours a day.
As we demonstrated,
it would produce 16,000 kilowatt hours per day.
The average daily energy consumption
of a typical house is 30 kilowatt hours.
And finally, each house does in fact steadily consumed
a flat rate power figure of 1.25 kilowatts.
We know this last point isn't true
because of our earlier discussions
about instantaneous power demand
at particular points in a day,
however, let's just say the instantaneous demands
of all the houses we're really considering
does average out to a steady state draw
of 1.25 kilowatts each.
For example, not everybody is popping
a load of wet clothes in their dryer,
vacuuming the floor, and making a smoothie at the same time,
but rather these events occur out of sync with one another
such that it makes it appear as if each house
draws an average 1.25 kilowatts of power.
Given the original phrasing of this question,
let's answer this question.
How many houses can a two-megawatt turbine power
given an average power consumption of 1.25 kilowatts each?
This two-megawatt turbine could theoretically power
two megawatts or 2,000 kilowatts
divided by 1.25 kilowatts per house
or 1,600 houses or can it?
You'll note a major flaw in this assumption.
Notably this community would only be powered
when the wind was blowing,
meaning for the remainder 16 hours of the day
when the turbine was not operating,
the houses would be dark.
This is to suggest that in order to continuously
and reliably power this community on a 24-hour basis,
a mix of energy sources like wind, water, solar,
coal-fired power plants, and natural gas turbines
need to work together.
Not only are renewable resources
like wind and solar intermittent in nature,
they're also unschedulable.
Intermittent and unschedulable by the way
doesn't mean unpredictable.
For example, if this community
knew the wind forecast in advance,
they could turn off the gas turbines
and turn on the wind turbine when it was windy
and turn on the gas turbine
and turn off the wind turbine when it wasn't.
What's the advantage of this mixed approach?
Easy, you're not burning expensive gas
when the free wind is blowing.
Let's answer this question
from a different perspective, that of energy.
Let me rephrase the question ever so slightly.
How many houses' daily energy needs
can a two-megawatt turbine
operating at full capacity for eight hours satisfy
given each house consumes
30 kilowatt hours of energy everyday?
As we demonstrated, a two-megawatt turbine
operating at full capacity for eight hours
produces 16,000 kilowatt hours.
Given each house consumes 30 kilowatt hours each day,
this means this turbine can satisfy the daily energy needs
of 16,000 divided by 30 or roughly 533 houses or does it?
The problem again is matching
the instantaneous power requirements of a house
with the instantaneous power output of the turbine.
The turbine produces way more power
than instantaneous needs of 533 houses for eight hours,
and then just goes dark when the wind stops.
There is a workable solution to this problem too.
Consider letting the wind turbine operate
intermittently throughout the day
and dump excess overproduction into a battery bank
to be withdrawn when the wind dies.
What's the advantage of this approach?
Easy, you're not burning any gas at all.
Other techniques that could allow the transition
to an all-renewable grid might be the grid itself.
Consider several communities each consisting of 533 houses
and a two-megawatt wind turbine linked to each other
via a transmission grid.
Granted it may not be windy in regions A and C,
but in region C where it is windy,
the output of this turbine can be directed to A, B, and C
matching the instantaneous power output of the turbine
with the instantaneous power demands
for all three communities.
When weather patterns shift
and it's windy in region A, and not B and C,
the output of this community's turbine
is directed to A, B, and C.
Add to this transmission scheme
localized battery storage in regions A, B, and C.
When it's windy in two or more regions,
any excess power stored in these battery banks
to account for the inevitable day
when the wind refuses to blow in any of these regions.
Keep in mind energy storage needn't be limited
to electrochemical means as in batteries
but can also take the form of pumped hydro storage
when in the event of excess power production,
water is pumped uphill,
and in the event of need,
it's allowed to run downhill
and turn a hydroelectric turbine.
Add to this simplistic wind generation scheme,
additional supporting renewable sources
like solar, biofuels, and geothermal.
This scheme is not as farfetched as you might think.
We have the technology, we have solar panels,
wind turbines, batteries, and a transmission grid.
To make this a reality,
we need political will and economic muscle to overcome
the significant technical challenges this presents.
This will not be easy nor inexpensive by any measure.
Intermittent and unschedulable renewable resources
like solar and wind necessitates a sufficiently large
population of distributed generation sites.
Batteries and reservoirs must be constructed
with sufficient scale,
and the transmission grid needs to be upgraded
to handle this level of coordination.
Vocal detractors are quick to point out
the complexity and cost of such a future.
Listen, I never said it was going to be cheap and easy.
In fact I'm telling you upfront the switch to renewables
would be the most expensive
and most complicated leap we've ever made.
However, the future of business as usual
is horrifying to consider.
Think of a world with more and more and more people
and less and less resources.
You do the math.
I don't mean to end this lecture on a down note,
but I do want to emphasize
that society needs energy to function.
All forms of energy extraction come at a price.
The way I see it we can pay this cost
via two radically different approaches.
One, the hard and dirty way.
Fighting increasingly frequent conflicts
to ensure our continued access
to limited petroleum supplies,
or two, the soft and clean way,
make our own energy inside our own communities
using abundant renewable resources.
My intention in publishing these lectures
is to give you the skills necessary
to contribute towards solving a complex challenge
that has lasting implications for our nations future.
In conclusion this lecture examined energy and power
at an introductory level.
We learned power is energy per unit time,
and energy is power times time.
We introduced units used to measure energy,
namely the joule and the kilowatt hour,
and learned to convert power measurements
expressed in units of horsepower and watts.
Remember to review these concepts
as often as you need to really drive it home.
Imagine how well lab will go if you know what you're doing.
Thank you very much for your attention and interest.
And we'll see you again
during the next lecture of our series.
Remember to tell your lazy lab partner about this resource,
be sure to check out the Big Bad Tech channel
for additional resources and updates.
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