words are in blue
is Christmas. Joe and Peter are happy - both have received gifts
from Santa Klaus. They are impatient to meet each other and to show
Joe receives many presents because he got good results at school. Among all
these gifts, he especially likes the construction kit with a small electric
motor to make a carousel. The carousel has to be constructed from a lot of
metallic parts and screws. In the box is also a small solar PV panel that will
provide the electricity to run the electric motor.
Peter opens a large package containing a Formula 1 loop and 2 small formula
1 cars with electric motors. The loop is made of plastic plates that provide
the speedway. Every plastic plate has two channels in the middle that assure
the guidance of the small cars on the loop. There are also two consoles for
two players that can remotely increase the speed of the cars on the loop…
both children, separately in their houses, are enjoying chocolate
bonbons and oranges, but tomorrow they will meet to play with the
new toys brought by Santa Klaus during last night. Both of them are
going to bed and dreaming about tomorrow.
is still dark outside, but the children are already awake. Each of
them waits with impatience for the day to start, to have breakfast
and to meet each other.
can I invite Peter to our home to build my construction kit now?
Mother: Peter’s already
called and proposed to meet in his house because he’s got
a very nice large Formula 1 loop with two racing cars. I told him
that you’d go to him after the breakfast. Joe is very
impatient to leave.
Peter has finished breakfast and has already started to put the loop plates
together on the carpet in his room when somebody is ringing at the door. Its
Joe - the construction kit in his right hand.
of them start to excitedly examine eachother's toys. Somebody is
ringing at the door. Its Paul who’s come to say hello to Peter’s
parents and is very glad to see the kids together. Joe and Peter
are keen to capture Paul to look at their toys. Paul apologises to
Peter's parents and goes with the kids.
Paul: What do we have here?
A Formula 1 race loop, and a construction kit with solar PV panel.
That’s extraordinary. We can make an interesting combination
because I also have in my pocket a solar PV panel of the same shape
and capacity as yours. Your loop is powered by electric batteries?
We can feed each racing car with solar PV panels.
Peter: Is it better to use
PV panels than electric batteries?
Joe: I believe that PV panels
are better than batteries because they are not discharging themselves
like the batteries.
Peter: What do we do if
there is no light, do the PV panels still produce electricity?
Joe: No. But you have lamps
in your room, so we can use those if there is no sunlight, for
Paul: Well done boys. Let’s
investigate more! Paul takes some electric accumulators
and electric batteries out of his pocket. He also takes out a small
PV panel exactly the same shape as the one in the construction
see how the PV panels and electric batteries work and, if you want,
we can talk a bit about electric accumulators.
The camera is focusing on the tools, the batteries, accumulators
and PV panels.
can see what is written on them. Some of them have a label indicating
that they are rechargeable. Yes! This makes the difference: the
accumulators can be recharged and the ordinary batteries get thrown
out after they are discharged.
Joe: I’ve seen a young
man throwing the discharged batteries from his Walkman on the ground
in the park. I told him that the batteries must be collected and
not disposed together with ordinary waste; because batteries are
Paul: The batteries are
producing electricity as result of a chemical reaction between
a base and the electrodes. The accumulators are somehow similar.
There are many types of accumulators - the oldest and the most
known one is the lead plates and acid accumulator.
A battery is a device that stores energy and makes it available in an electrical
form. Batteries consist of electrochemical devices such as one or more galvanic
cells (or, more recently, fuel cells). The first possible evidence of batteries
in history are the Baghdad Batteries from sometime between 250 BCE and 640
CE. The modern development of batteries started with the Voltaic pile developed
by the Italian physicist Alessandro Volta in 1800. The worldwide battery industry
generates 48 billion dollars in sales annually (2005 estimate).
Lead-acid batteries (or accumulators), invented in 1859 by French physicist
Gaston Planté, are a type of galvanic cell and are the most commonly
used rechargeable batteries today. They also represent the oldest design with
one of the worst energy-to-weight ratios, although the power-to-weight ratio
can be quite good. Also, the energy-to-volume ratio is good compared to other
types of batteries. They are cheap and can supply high surge currents needed
in starter motors. Every reasonably modern car uses a lead-acid battery for
this purpose. They are also used in vehicles such as forklifts, in which the
low energy-to-weight ratio may in fact be considered a benefit since the battery
can be used as a counterweight.
Lead-acid car batteries consist of six cells of 2 V nominal voltage. Each cell
contains (in the charged state) electrodes of lead metal (Pb) and lead (IV)
oxide (PbO2) in an electrolyte of about 37 % w/w sulphuric acid (H2SO4). Modern
designs have jellified electrolytes. In the discharged state both electrodes
turn into lead sulphate and the electrolyte turns into water. (This is why
discharged lead-acid batteries can freeze.)
But let’s see how the PV panel works.
Joe: a PV is made
of semiconductor materials that have the property of transforming
the light waves into electricity. Generally, to build solar PV
panel silicone crystals are used.
Paul: A solar cell, or photovoltaic
cell, is a semiconductor device consisting of a large-area p-n
junction diode, which in the presence of sunlight is capable of
generating usable electrical energy. This conversion is called
the photovoltaic effect. The photovoltaic effect was discovered
in 1839 by French experimental physicist Alexandre-Edmond Becquerel.
He observed that certain materials would produce a small current
when exposed to light. Light is comprised of packets of energy
called photons. When light hits the p-n junction of a semi-conductor
the absorbed photon energy releases an electron from the n-type
region and moves it to the p-type filling a hole and creating a
current. The field of research related to solar cells is known
Solar cells have many applications. They are particularly well suited to, and
historically used in, situations where electrical power from the grid is unavailable,
such as in remote area power systems, Earth orbiting satellites, handheld calculators,
remote radiotelephones and water pumping applications. Solar cells (in the
form of modules or solar panels) on building roofs can be connected through
an inverter to the electricity grid in a net metering arrangement.
it. So PV cells are producing electricity without any noise, vibration
or moving parts. They present a lot of advantages however the downside
is the very high costs. Generally, the PV panels (that are formed
by several solar cells) are used together with electric accumulators,
in order to store the electricity produced during the daytime.
This way the electricity can be used during the night.
we know the differences between electricity sources, what do you
say to feed our racers with electricity from solar PV panels?
Paul: We will need only
four pieces of insulated wire to make the connections between solar
PV panels and the racers.
The three people are making the connections and then they are testing the installation.
It works perfectly. The only thing to remember is not to stay between the light
source and the PV panels.
The boys start playing. They are glad and say that next summer they will play
outside with the Formula 1 racing loop. They really like the idea of a contest
of solar automobile builders in their school.