GEOGRAPHY AS LEVEL
1. Explain what a photothermal solar panel is.
Using photothermal solar panels is a relatively new invention;
however the concept of using the suns power to heat homes is
not. For example the centauries ago south facing homes were
built to increase the temperature in homes. They were built to
maximise the heat in the homes especially in winter when the
sun is low and the climate becomes harsher, and to avoid most
of the solar radiation in the summer to keep the homes cooler.
The rooftop solar water heater was created based on the ideas
that the ancient Romans used. The Romans found that by
putting glass in windows the solar radiation is trapped in the
room so the warm temperatures stay for a longer period of
time. The rooftop solar water heater traps the suns rays in a
glass collector which then heats up water located inside
insulating glass pipes.
This water is then sent along pipes towards a heat exchanger.
The heat exchanger is located in the hot water tank It is shaped
like a coil, the boiling water moves along it heating up the cold
water in the tank, which is then used to heat the home or
provide hot water.
When the water comes out of the heat exchanger it is then
passed along the pipes. This time the water is quicker to heat
up, because it is still warm from the last cycle. There is usually a
black insulating material covering these panels to protect it from
the weather. New tubes have a glass outer case and a vacuum
to take out the air in and around the pipes because heat is lost
at a fast rate through the air.
2. Outline features of modern photothermal solar panels that
make them highly effective at capturing the sun’s energy.
They are light and durable to they are not badly affected or
damaged by the weather.
Vacuums are being added to them to take out air surrounding
the pipes so none of the heat produced is lost through the air.
No extra space on the ground is needed so they can be situated
in rural and urban areas.
This technology is not 70% cheaper than it was in the 1970s
3. Why are these panels so unpopular in the UK? (there are a
number of reasons)
These solar panels are only thought to work very effectively
between the months of March and October.
Even during the summer months a home would only be able to
provide 70% of its hot water need. This is excluding central
4. What is a heliostat and how does it work?
A heliostat is an piece of machinery that is able to track the
movement of the sun across the sky. They are used to position
mirrors to reflect the suns rays continuously throughout the day
Concentrated Solar Power
1. What is the correct name for the mirrors that direct the sun’s
rays towards the target?
2. Produce a mini case study of the impressive new power plant
near Seville. (Location, how it works, output, future
Enough sunlight falls on the earth every minute to meet the
world’s energy needs for a year. Seville has tapped into this
renewable abundant energy resource. Building a power plant
in the Andalusian countryside was a good location because the
sun shines on this area for over 200 days a year. They built a
large solar complex which has been operating since 2007. The
large tower in the centre of the complex has been called the
“Solar tower of power” and is 40 storeys high.
This tower collects the concentrated solar waves from 624
mirrors, and produces electricity for approximately 6000 homes.
These mirrors are able to rotate to track the suns movement
across the sky, to maximise the amount of energy absorbed.
These concentrated rays are reflected towards one point of the
tower called the receiver. They concentrate to heat up by about
1000 times to try and generate 500°c + to turn the water
behind the receiver into steam.
Behind the receiver there are pipes full of water which are
turned into steam. This steam then stored in a chamber like a
boiler until it is ready to be used. It is then send along a series
of pipes which turns a turbine and then a generator which
The success of the first plant encouraged engineers and
scientists to construct another power station next to it to
increase the amount of electricity that can be generated. This
second tower is said to be able to produce twice as much power
as the first.
The complete construction of the combined power plants it on
course to be completed in 2013. The total cost of this project is
€1,200 million, and should produce 300MW of electricity to
power 180,000 homes. These power plants should reduce the
amount of CO2 by 600,000 tonnes.
The original power plant generates 24.3GW/hr per year of clean
energy. All of the heliostats cover a surface area of 120m². The
hot water is stored in tanks that can reach temperatures of
250-255°c. If they used salt to store the heat the temperature
would increase to about 600°c.
The second power plant will have 1000 sun tracking heliostats
which will drive 120m² mirrors, which will send their
concentrated rays to a tower 165 metres tall. This plant will
produce 1.2MW of electricity from 154 silicon plate heliostats.
They are also testing another solar energy system, parabolic
trough collectors. These work as the sun is concentrated onto
mirrors which are shaped in a parabolic form so they are able to
move into an upright position towards the sun.
The suns rays are then concentrated onto an absorbing pipe
which contains synthetic oil. The absorbing pipe is found at the
mirrors focal point. This oil is the heated up to temperature
about 400°c. The oil is then pumped through a series of heat
exchangers to produce steam.
This plant is designed to supply 25000 homes with electricity,
and currently produces more electricity than the tower.
However researchers believe that in time the tower might prove
to be the most efficient out of the two options.
Unfortunately both systems have the same fault. They are not
designed to operate when the sun sets. To overcome this,
scientists found a way to store the heat in water in the tank
though the heat will only be stored for up to an hour.
Eventually they found that they could use salt to store the heat
at temperatures reaching beyond 220°c. This will cause the salt
to melt and become completely clear resembling water. The
molten salt can be heated to a much higher than water without
boiling so it is easier to store heat in.
With this plant in full operation they believe that it can provide
200,000 homes with electricity. And they are hoping that in the
future they can build a power plant like this one large enough to
produce between 700 and 800MW of electricity.
3. Where else in the world can we find similar power plants?
1. Explain what a photovoltaic solar panel is.
The word photovoltaic literally means light electricity.
These cells are made from semiconductors such as silicon.
They work, as a photon (a particle of light) comes into contact
with the photovoltaic cell, which takes a fraction of the energy
collected by the semiconductor. Photons energy is purely kinetic
so it can be transferred to the semiconductor material. This
energy causes electrons in the particles to become “knocked
off”. Enabling them to flow freely. The photovoltaic cells use an
electrical field, which forces the electrons to g in a specific
direction, creating an electrical current.
This current has a voltage which leads to power. Power can be
calculated by using the equation P=IV. To stop the photons
being reflected off the silicon have an anti-reflective material
attached to them. Thought only 15-25% of the energy is
absorbed. The electricity created will flow along the systems in
your house, and any excess will go onto the national grid.
A major problem with this is that you can’t store electricity so a
large proportion of the solar energy is lost.
Amorphous cells are les efficient versions of these cells but they
are cheaper so a large percentage of people use these. The
alternative is to use crystalline cells which are very efficient but
are very expensive.
Now scientists are trying to build integrated photovoltaic solar
panels. These will be built into roofs, windows and possibly
paint. This should drive down the cost of solar electricity even
further, because you are not buying the panels and the
2. Why are these panels so unpopular in the UK? (there are a
number of reasons)
These panels are so unpopular in the UK because they are very
expensive. Costing 2-5 times the typical grid power. Though if
you make more electricity than you need you can sell the excess
energy to the national grid for a premium.
3. Why might these panels be more useful and more popular in
These solar panels may be more useful in
LEDCs because they tend to be in areas with a
hotter climate with more exposure to the sun.
This map shows that the majority of Africa
would be a good place to build solar panels.
They are also more popular with these
communities because they can create solar
cookers either buy purchasing them or creating
ne themselves cheaply.
4. These are arguably the greenest way of producing electricity –
what evidence is there to support this?
Solar power systems provide an environmental friendly source
of energy, and produce almost no emissions. Most of the
emissions produced are produced during the construction of the
power plant. Furthermore the plant consumes no other fuel
other than the light from the sun so no fossil fuels are being
used. The only problems are that these power plants take up a
large amount of space. Though the difference I the sizes of this
power plant and fossil fuel power plants is minimal because
fossil fuel power plants take up a lot of space for mining and
exploration to find the raw materials that they need to use.
5. Which country has invested heavily in photovoltaics?
Germany has started to use a lot of photovoltaic cells to provide
electricity. They are being built along the sides of roads and on
the top of buildings and on the tops of walls. Germanys PV
capacity has risen from 100MW in 2000 to 4150MW in 2007.
Passive Solar Heating
1. Explain how this process works?
Glass allows light in but traps heat. This is known as the
“Greenhouse effect”. Sunlight coming through a window can
heat up any room. This is good in winter but bad in summer.
Poorly designed windows can cause more bad heat transfer on
winter nights and summer days than the good solar ain that
they allow in on sunny winter days. Thermal modelling is
The solution is to have “isolated solar gain” through a
greenhouse/solarium/sunroom/conservatory. This will create a
“buffer zone” between the interior and exterior glass (there will
be a window on the outside of the solarium and one between
the solarium and the living area itself.
The sun room is located on the equator side of the house. If you
are in the Northern Hemisphere this room will face south, and if
you are in the southern hemisphere it will face north.
Glass is maximised on the equator side to allow in the abundant
day light in. Glass is minimised on the other side of the house.
A solarium can be integrated into a low-cost near-zero-energy
home. We have known how to do this since the 1978 solar
energy tax credits in America.
In a 1980 New England Salt Box home the south side is high to
let in the abundant sunlight. The North side is lower to block
cold winter wind.
Sunspace creativity can be used in both single and two storey
homes. They can be used for tropical plants, or even a spa or
swimming pool. The year round conditions are tropical. This
heat can also be used to heat water in the room which will
contribute to the thermal mass of the home
What scientists are trying to find solutions to is how to send the
temperature trapped in the sunny south facing rooms to the
north facing rooms. The solution that they feel is the best is to
design the houses that it has a natural convectional air current
This is where warm air rises because of its decreasing density in
the solarium and cold air falls in the north facing rooms. This
creates a circular air flow path that will continuously transfer
heat between rooms while the sun is shining. This is a self
regulating temperature balancing system.
In hot humid climates a process called cooling with sunshine.
This is where large roof vents are open and all air flow is
upwards. The thermal buffer zone is kept cooler than outside
air. The temperature of the Earth is used to cool and dehumidify
the temperature at the base of the building.
What we have to remember is never use roof angle glass or
skylights, because in the summer these create a solar furnace,
and has uncontrollable harsh glare. And in winter air rises,
leading to major heat loss at night through the glass. Roof angle
glass leaks and hail can smash it.
2. Why is it not suitable for everybody’s home?
This is not suitable for everyone’s home because if you have a
large house the heat will take longer to heat all of the rooms
and so the chances of the owners having to use electricity is
The construction of the house will be affected, and after it is
built the cost of cleaning the windows will be very high.
They are not very child friendly, because they might fall through
This table shows the
different forms of
collecting solar power.