- [Instructor] In this video,
we're going to look at a solar furnace
and I'm gonna explain
to you how it functions
and some of the main
components within the system.
You can see now that we are right
in the middle of the solar furnace.
I'll actually just rotate
it slightly and zoom out.
We can see that we've got a plan overview
of a solar furnace operation.
These yellow lines are being used
to indicate the sun's rays.
And the sun's rays are actually a form
of electromagnetic radiation
but for this video,
we'll just refer to it as solar energy.
The sun's rays are coming down
and they are gonna impact
upon a plain flat surface.
This plain flat surface is
referred to as a heliostat
and it is essentially a plain
mirror, or a flat mirror.
What's special about heliostats is
that they're actually
able to move east to west
and north to south.
This is what refer to
as dual axis movement.
Now with this form of movement, it ensures
that the heliostat can
reflect the light continuously
to one specific focal point.
Now what we've actually got here is a bank
of approximately 15 heliostats
and they're all reflecting the sun's rays
not to one specific point,
they're actually reflecting the sun's rays
onto a parabolic mirror, or a
series of parabolic mirrors.
Parabolic mirrors are
curved shaped mirrors
and they are gonna be
used to focus the light
that is coming from the heliostats.
Unlike the heliostats,
the parabolic mirrors are
completely stationery.
So it is the job of the heliostats
to reflect the sun's rays
onto the parabolic mirrors
at specific points, and
those parabolic mirrors,
are then going to focus all of that energy
onto a specific points.
The specific points that
we're now focusing onto,
is known as the furnace.
The furnace itself sits
on top of the tower
and that is the reason these types
of solar power generation
are sometimes referred
to as power towers.
When the sun's rays are being
concentrated onto the furnace,
the temperature within the furnace
is gonna drastically increase
and we're gonna use this thermal energy
to heat up molten salt.
So let's now go and
find the starting point
of our molten salt system.
We can see in front of us now,
that we have a molten salt storage tank.
This storage tank is
actually what we refer
to as a cold storage tank.
It's not cold in the
sense of it being five
or ten degrees Celsius,
it's typically gonna be
anywhere between three
or 400 degrees Celsius.
The molten salt is gonna come out
of the cold storage tank along this pipe
and it is gonna go to the tower.
It's then gonna go up the
tower and into the furnace.
When it goes into the furnace,
it is gonna be heated up,
it's gonna absorb some
of that thermal energy
and the temperature of the
molten salt is gonna increase.
When it exits the furnace,
we can expect the temperature
to be anywhere between 600
to 1000 degrees Celsius,
although this depends upon
the system and the design.
We go around the furnace and the tower
we can actually see where
the molten salt exits.
So it has a hot molten salt
that is now coming out of the pipe,
along the pipe here and it is going
into another storage tank.
This, what we're gonna refer to
as a hot molten salt storage tank.
The reason we store the hot molten salt
is because we wanna be able
to generate electricity
when there is no sunlight available.
It's a lot cheaper to store a large amount
of thermal energy in a tank than it is
to try and store a large
amount of electricity.
So we will a large amount of
thermal energy in the tank
and we're gonna release this energy
to make steam and generate electricity
when more electricity is needed.
It's not unusual to be able
to generate electricity
for three to five hours
without having any available sunlight
although many plants are now trying
to increase this to 10 to 12 hours.
10 to 12 hours means that we can
consistently generate electricity
both during the daytime,
where there is an abundance of
sunlight, and the nighttime,
when he have an abundance
of stored thermal energy.
So let's follow a hot molten salt
as it comes out of the tank.
It's gonna be pumped along here
and it's gonna go into a pump.
Now this pump is very basic, obviously,
the pump has to deal with
very high temperatures
so it's gonna look slightly different
to the basic model we have here
but essentially the hot
molten salt is gonna come out.
It's gonna pass through a
pump or a series of pumps,
and then it is going to
go to a heat exchanger
or what we refer to as a steam generator.
So we can see it's coming in the end
of the heat exchanger
on the right hand side
and it's gonna pass
through the heat exchanger
and it's actually gonna come out almost
at the same point where it went it.
We just zoom in slightly so you can see,
the hot molten salt is
coming along this pipe here,
it goes in to the heat exchanger
or the steam generator,
and then it comes back out here
and along then to a cold
molten salt storage tank.
So what we've essentially got is a loop,
let's see if we can have a
look at it from high above.
Now we're coming out of the tank,
we're going along here,
the molten salt is cold,
it's gonna be heated up in the furnace,
it is traveling further along the pipe,
it does then go back to the
hot molten salt storage tank
and it's coming out
again going to the pump
and then it is going along
here to a steam generator
and we're gonna pass it
through the heat exchanger
and back to the cold storage tank.
So that is the entire
circuit for a molten salt.
Let's now move on and have a look
at the water circuit
and the steam circuit.
What we're actually looking at now
is a pipe coming out
of the steam generator.
I'll zoom in so we can
have a better look at it.
This pipe comes out of the
steam generator here and down
and it is going then along all
the way to a steam turbine.
Just follow the pipe along here.
We can see it entering
into a steam turbine.
Steam turbine is this entire
piece here within the building.
And what we actually got is a
steam turbine and a condenser.
The condenser itself is
used for condensing all
of that steam back into
condensate or water.
But for now let's just follow the steam,
the steam goes into the turbine,
as the steam passes through
the rows of turbine blades,
the steam turbine is actually gonna rotate
and as the steam turbine rotates,
it is gonna rotate an alternator.
Zooming, we can see the alternator is
on the end of the steam turbine,
that is this section here,
and the alternator is then
gonna generate electricity.
Once we've generated electricity,
we're gonna distribute
it to some switch gear,
which is inside this building here.
The switch gear is a lot
like a circuit breaker
and we're gonna use that to
switch on or off the power.
Assuming the switch gear is closed,
we're gonna transfer the electricity
through the switch gear and
to a electrical transformer
and then through again
some more circuit breakers
through an open air switchyard
and into the National Grid,
which is represent by this
electrical pylon here.
At that point, we've finished the cycle.
So we're taking the sun's rays,
we focus them on a specific point,
we've created a source of thermal energy,
we've used that source
to heat up molten salt,
the molten salt, were then
used to heat up water,
and generate steam, and
the steam were then used
to rotate a turbine and an alternator
which has generated electricity.
So that is the entire cycle.
We go back a a little bit, we can see
what happens with the steam
after it was condensed.
The steam would've gone
into the steam turbine,
and then it will be
condensed in the bottom
of the steam turbine in the condenser,
and it will come into these two pipes
that we're looking at now.
These two pipes are going to
connect onto the main pipe here
and we're gonna pump the
condensate or the water
back to the steam generator.
Just see if I can line this
up with the correct angle.
So it comes out along this pipe,
condensate is then
delivered through a pump
and to the steam generator
where it will be heated up
again and turned to steam.
Now you might be wondering what is it
that is cooling down the steam
and enabling us to turn
it back into condensate.
Well it's actually normally
a large cooling tower
or a series of modular cooling towers.
We've got an idealized
example on the screen now.
We see this cooling tower is this item
in the center of the screen
and the cooling tower
connects to the condenser.
What's actually gonna happen is the water
from the cooling tower
which is relatively cold,
is gonna be pumped to the condenser,
and it is gonna cool down the
steam, turn it to condensate,
and then the cooling
water is gonna come back
along this pipe and we're
gonna distribute that heat
that we picked up from
the steam to the air.
So we are air cooling, cooling water,
and then we are using
the cooled cooling water
to cool down the steam
which turns the steam into condensate.
So that is essentially how
we generate electricity
using solar furnace.
What you might have realized is,
what we're actually doing
is transferring energy
from one form to another,
to another, to another,
until we get the form
that we can actually use,
or the form that we find most useful.
We originally started with the sun's rays,
or electromagnetic radiation,
we then focus this onto a specific point
in order to turn this
electromagnetic radiation
into thermal energy,
we then use the thermal
energy to heat up molten salt
and then we use this thermal
energy from the molten salt
to heat up water to generate steam.
The energy stored by the
steam, known as enthalpy,
was used to drive the steam turbine,
which in turn, drove an alternator
which generated electricity.
And this current can be distributed easily
across very large
distances and we can use it
to perform useful work
such as boiling a kettle
or rotating a motor in a washing machine,
or a pump in a dishwasher.
So there are many
applications for electricity
and that is the reason
for having this entire
power generation facility.
(gentle music)
