Solar Sahara Saves Earth?
King Edward VI School
About us…
We are a group of young women inspired by the current advances in engineering. We have chosen to study a
combination of AS Levels, including Physics, Maths and Design Technology.
The team consists of Danielle Clapcott, Ali Diaper, Emma Falconer, Hazel Webb and Olivia Wood- all students at King
Edwards VI School, Southampton.
Challenges of the 21st Century
As a group we discussed what
we thought were the main
problems that people of the
Earth face. We managed to
come up with these seven,
very broad, categories:

Energy

Transport

Climate change

Population

Resources

Medicine

Technology
The section which we feel is
most important for engineers to
address in the twenty first
century is Energy. It is such a
key problem due to the ever
expanding global population,
and one that young engineers
need to find a solution to. The
three areas of energy that
have to be considered, in
order to use the planet’s
scarce resources effectively to
produce power, are:
Production- “The action of
making or manufacturing from
components or raw materials,
or the process of being so
manufactured.”
Distribution- “The action of
sharing something out among
a number of recipients.”
Use- “Take, hold, or deploy
(something) as a means of
accomplishing or achieving
something; employ.”
The major problem when
considering energy production
in the 21st century is whether or
not the energy we are using is
sustainable; and what impacts
it will have upon local and
global environments.
So what is sustainability? It is
defined as meeting the needs
of today's population without
compromising the needs of
future
generations.
Today
sustainable development is
usually considered to include
environmental,
social
and
economic sustainability.
There are different types of
“green energy” that have
been discovered. As a team
we are choosing to investigate
the source of power which we
believe, through development
of technology, could solve the
energy crisis - Solar Power.
"The human race must finally
utilise direct sun power or revert
to barbarism,“
wrote Shuman in a letter to Scientific
American magazine
As Shuman has observed, Solar
power may be the solution that
will guarantee the survival of
the planet for future
generation.
The production of solar panels
has improved greatly since
their first design. However, the
distribution of the solar panels
themselves is inefficient. This
may be due to the fact that
little has been done to improve
the distribution of electricity
once it is obtained. With both
these factors in mind, it is no
wonder the cost of installation
is still rather high.
In this presentation, as a group,
we are going to investigate
how future engineers could
tackle the distribution aspect of
energy by using one of the
largest deserts in the world (The
Sahara) to site a vast number
of solar panels. This will mean
that there will be no shortage
of energy for the future
generations. In the long term, it
will ensure that every person on
the planet is given the right to
obtain
affordable
green
energy.
The case study we have
chosen to refer all calculations
and scenarios to is New York
City,
America.
We
have
chosen New York as it is
consumes huge amount of
energy daily and there is huge
dependence on the energy
sources of New York to provide
a reliable service. New York city
is around 6300km from the
Sahara, allowing us to consider
the problems that may occur in
the transportation of the
energy.
The Sahara
Background Information
The Sahara Desert, located in the
north of Africa, covers an area of
about 9,100,000 km2, making it the
third largest desert in the world
after the Arctic and Antarctica
(and the world’s largest hot
desert). The Sahara, which is
Arabic for "The Great Desert,"
engulfs most of North Africa
covering large sections of Algeria,
Chad,
Egypt,
Libya,
Mali,
Mauritania,
Morocco,
Niger,
Western Sahara, Sudan and
Tunisia.
Climate
The Sahara’s north-easterly winds
can reach hurricane level and
often give rise to sand storms and
dust devils. Half of the Sahara
receives less than an inch
of rain per year, and the rest
receives up to 4 inches per year.
The infrequent rain is usually
torrential. In addition to being
extremely dry, the Sahara is also
one of the hottest regions in the
world.
The average annual temperature
for the desert is 30°C but during
the hottest months temperatures
can exceed 50°C, with the highest
temperature ever recorded at
58°C in Aziziyah, Libya. However,
because the air is so dry and has
so few clouds, the temperature
drops
quickly
after
sunset.
Differences of as much as 28°C.
between day and night occur
regularly, and overnight freezes
are common during winter.
Geology
The Sahara might be famous for its
sandy dunes but, in fact, only 20%
of it is sand, the rest of it is mostly
made up of bare rock. The largest
sandy desert is the Rub’ al Khali
situated in the middle of the Saudi
Peninsula. To put into perspective
how vast this area is, it is 1000 km
wide and 500 km long.
The highest peak in the Sahara is
the volcano Emi Koussi
3,415
meters in the Tibesti Mountains in
northern Chad. The lowest point
in the Sahara Desert is in Egypt's
Qattera Depression at -133 m
below sea level.
The Sahara
Inhabitants
How deep is the sand in the
Sahara?
How much
cause?
It’s actually quite difficult to
answer this question. We don’t
really know how deep the sand
goes before the bedrock starts.
The Sahara covers over 3.5 million
square miles and has only 2.5
million inhabitants. This is roughly 1
person per square mile. Most, if
not all, of the population are
Nomads.
One estimate gives the average
depth of the sand to be
approximately 150 metres while
the top of the dunes can reach a
height of 320 m from the bedrock
(170-180 m high measured from
‘sand-level’).
How much distance does the
sand travel?
Dunes behave very much like
ocean waves but in slow-motion.
Wind and rain cause the sand
surface to ripple. Crescentic
dunes in China were measured as
moving about 100 metres a year.
In sand storms dust (but not sand)
may be lifted as high as 6,100 m
high.
impact
would
it
This means there are no lasting
villages that solar panels would
disrupt as the nomads travel
around. Nomads would also not
live in the centre of the Sahara as
there is very limited vegetation
and water.
The Sahara hosts some 70 species
of mammals, 90 species of
resident birds, 100 species of
reptiles, and numerous species of
arthropods. If the solar panels
were in the centre of the Sahara,
the lack of vegetation and water
infers there is a lack of animals in
the very centre. This therefore
limits the disturbance caused.
How does a solar panel work?
Glass is required for
protection and as
Silicon doesn’t absorb
photons
Acts like a
diode so
current only
flows one way
P-type Silicon
layer doped
with boron
N-type Silicon layer
doped with
phosphorus
Photons in sunlight hit
the solar panel and are
absorbed by the silicon.
Electrons are knocked
loose from their atoms in the
N-type silicon, causing an
electric potential difference.
DC TO AC
INVERTER
Current
must then be
converted to
AC so it can
be used in
households
Current
starts
flowing through the
material to cancel
the voltage and this
electricity is captured
the in the P-type
Silicon
Problems
When considering to place a
number of solar panels in the Sahara
desert there are a few problems
that we will encounter. To ensure
the placement is viable we need to
think of all the difficulties, and how
engineers
and
scientist could
possibly solve them using current
and developing technologies and
ideas.,
Placing the solar panels.
The problem with attempting to
place solar panels in the dessert is
that the top surface of sand has the
tendency to travel great distances
over short periods of time.
Servicing the panels.
Due to the Sahara's climate it would
be very difficult for a human to
enter the location and work on the
parts for long time periods
Cleaning the panels
As the sands of the Sahara are
continually on the move there is the
risk of the surface of the cells to be
covered in sand causing a reduction
of energy generation.
Storing the Energy
Once the electricity has been
generated there is the question of
where to store it. If stored at source
and a problem occurs in transport a
city is potentially left with no power,
however not many large cities have
enough ground area to place
storage plants.
Transport of energy
As the wires will be at a high
temperatures the resistance of the
wires will also be high.
This is a
problem because the higher the
resistance, the higher the power loss.
Therefore a step-up transformer is
usually used, but they only work when
the electricity supply is in AC.
Electricity generated from solar
panels is DC. We have therefore
considered using invertors.
Costing
The start up cost would be
exceedingly
high
therefore
international
government
spending would have to occur
and with all the possible problems
there is no guarantee that the
panels would be profitable.
Ownership
There is a potential dilemma as to
who owns the panels, as they
could be spread across several
countries in Africa, So the United
Nations may have to be involved
with the process, elongating the
time of set up.
Placing solar panels.
As we found out earlier in the
investigation, the Sahara is not
made from all sand. However,
there is no way of placing the
panels on top of the sand
areas as the foundations are
not stable and the chance of
them being covered in sand is
increased.
This problem is faced when
drilling for Oil in the North sea.



1.
Fixed
Platform,
Concrete/steel
legs,
Anchored
to
seabed,
<520m deep water.
2.
Compliant
Tower,
Slender, flexible, 370-910m
deep water.
3. Tension-Leg Platform
(TLP), Concrete/steel legs,
Floating
platform,
anchored
to
seabed,
<520m deep water


4. Spar Platform, Similar to
TLPs, although anchored
with more conventional
moorings, Has a large
counterweight at bottom
and doesn’t depend on
moorings to stay upright,
making it more stable than
TLPs. 500-2,500m deep
water
5.
Semi-Submersible
Platform,
Special
hulls
make it buoyant, but
weight keep it upright, 603,000m deep water.
1.
2.
3.
Fixed Plat forms
Adaptations for the Sahara
Out of these ideas, only
structures reminiscent of a fixed
platform would work in the
Sahara.
Sand does not act like water in
the respect that things cannot
float on it, due to its granular
solid nature. The resistance
needed to support structures
like those of semi-submersible,
spar and tension-leg platforms
and compliant towers would
not be provided by the sand
and air that the structures
would be surrounded by.
Therefore, only fixed platformlike
structures
would
be
practical for placement in the
Sahara.
5.
4.
•
Made of a mixture of steel and
concrete.
•
High Young’s Modulus.
•
Durable (as exemplified by use in
bridge construction)
•
Would be especially important in
Sahara with large potential erosion
factors such as sand and wind.
•
Durability of steel would be
increased with a Zinc-Aluminium
coating.
•
Fixed directly to bedrock beneath
sand, which is approximately 150m
below the level of the sand. Sand
dunes generally reach about 320m
above the bedrock, so the
platform will easily be able to rise
above the highest dunes.
•
Concrete lower down, near
bedrock, and only steel further
towards the top of the structure,
reducing weight needed near the
top, thus making the structure
more stable. A non-solid structure,
comprised mainly of triangular
framework would further increase
the stability of the structure.
Servicing the panels.
In the case of sandstorms sand may
get stuck on the solar panels and
effectively block photons from getting
through and act as if it was night time
If the solar panels were raised at an
angles, this will not only maximise the
amount of sunlight absorbed but also
sand will tend to fall off it.
There have also been recent
developments on cameras which
vibrate for dust to be removed. This
could also potentially be applied to
our panels.
The diagram to the right demonstrates
how we plan to overcome the issue of
sandstorms, which could potentially
damage the surface of the solar
panels. By raising them above the
highest level sand can reach., we
avoid this problem.
Fixed Platforms consist of a jacket (a
tall vertical section made of tubular
steel members supported by piles
driven into the seabed) with a deck
placed on top, providing space for
crew quarters, a drilling rig, and
production facilities. The fixed platform
is economically feasible for installation
in water depths up to 1,500 feet.
We would modify this model to rest on
land, not on water. There would,
however, be increased stress at the
bottom of the platform on land. Our
plan is to use a material with a very
high young’s modulus, and a high yield
strength. This will ensure that the force
of the weight of the platform on the
supports would not cause breakage or
rupture at the base.
Storing the Energy
One
of
the
distinctive
characteristics of the electric
power sector is that the
amount of electricity that can
be generated is relatively fixed
over short periods of time,
although
demand
for
electricity
fluctuates
throughout
the
day.
Developing
technology
to
store electrical energy so it can
be available to meet demand
whenever
needed
would
represent
a
major
breakthrough
in
electricity
distribution.
This could also be used as back
up energy if there was a fault in
getting the energy into New
York, as there would not be an
alternative method.
The most common way of
storing energy is to turn the
energy into heat which then
later is converted back into
electrical energy.
Previous Methods
Storing electric energy as heat
in a tank less than 100,000
cubic meters in volume—a
technique
called
pumped
heat
electricity
storage
(PHES)—could
be
done
practically anywhere.
PHES works by boiling a tank of
water by running electric
current
through
heatgenerating wires and then later
using the steam to turn a
turbine
and
generate
electricity.
Problem: You could only
recover about 20% of original
energy used to boil the water.
Solution: The electric current
powers a heat pump that
heats the water, rather than
using current to heat it directly.
A heat pump moves heat from
a colder place to a warmer
place, using a fraction of the
electricity needed to generate
the heat from scratch
Heat pumps are around 300%
efficient. This means that for
every unit of energy used by
the heat pump in operation,
three or more units of heat are
generated for use in a building.
As heat pumps work by
extracting available heat from
the outside air, they are far
more efficient than even the
most efficient fossil-fuel based
heating systems.
This plant would be best to be
stored outside of New York, on
the outskirts of the city. This
means that there is an
alternative if there is a fault in
getting electricity to the city.
This shows a pumped heat
electricity storage facility
that takes electricity from a
solar panel or wind farm and
uses it to run a heat pump
(building with red tanks).
Water heated by the heat
pump is stored in a large
tank (centre) and is later
sent to a heat engine (blue
tanks), where electricity is
produced. Expanding steam
pushes piston.
Transport of energy
Micro-Inverters verses
Solar Panels produce a DC current
with a high value. This can be
problem when transporting power,
as higher currents cause excess
energy loss through heat. To reduce
the current a step up transformer
can be used, which increases the
voltage, decreasing the current
(due to V=IR) However these
transformers
only
work
when
inducing an AC current.
Solar inverters use electromagnetic
induction to convert DC from
photovoltaic cells to AC. They are
usually 93-96% efficient. So using one
would be beneficial as the energy
loss from changing the current type
is significantly less than traveling
across wires in DC, with high currents.
Solar invertors work by alternating
the way current flows through a
transformer coil, thus inducing a
constantly changing current (AC).
Include Maximum Power Point
Tracking (MPPT) to maximise power
output.
Above: simplified diagram of an
inverter. The switch moves back and
forth, sending the current produced
by the solar panels alternating ways
through
the
transformer
coil,
inducing a current in the output coil
of the transformer.

What? Inverters

connected to
individual solar panels,
which are in parallel
What? One inverter to
service many solar
panels, which are in
series

In non-shaded areas 
(like Sahara) they
increase efficiency by 
5-20%
Cheaper

This is calculated by I^2 R

There are two factors we can
minimise to decrease heat loss:
current and resistance.

We have investigated both of
these factors: the step up
transformer decreases current.
Resistance is addressed in the
next slide.
If one fails, only one
panel affected and
therefore more
convenient to
replace.

Cheaper and safer to 
install

Adjust to individual
panels’ resistances
etc.

Lower efficiency in
non-shaded areas
significant enough?
$0.40 per Watt
(October 2010)
Solution: Dual MicroInverters

Heat loss in power lines

String Inverters
What? A microinverter that services a
pair of panels

Halves expense
compared to normal
micro-inverters (only
half the number
needed)

But still has all the pros
of micro-inverters
$0.52 per Watt
(October 2010)
Transport of energy
One of the main problems we
face is the temperature of the
Sahara and the effect this will
cause on the resistance of the
wires. The low at night is -6’C and
the high in the day is 58’C –
clearly temperature fluctuation
and extremes will need to
considered
At such high temperatures our
resistance would be too high for a
current to flow due to the atoms
in the wire being given too much
energy and thus there being too
many collisions for a current to
flow.
There is however a possible
solution...Super conductors.
Super Conductors
The dictionary describes the
effect within super Conductors as:
“The flow of electric current without
resistance in certain metals, alloys, and
ceramics at temperatures near absolute
zero, and in some cases at temperatures
hundreds of degrees above absolute
zero.”
Super Conductors are our
solution to the resistance
problem.
When
the
temperature
of
superconductors are lowered
to
a
specifically
low
temperature they lose all
resistancethis
property
provides us with the ability to
transport the electricity we
obtain from the solar panels
through wires in the Sahara
with no resistance providing we
can lower the temperature of
the wires substantially .
Superconductors
have
conductivity of 108 in their
Super Conductive state. It must
be
noted
that
Superconductors leave their
superconductive
state
if
exposed to a magnetic field
(electricity), depending entirely
on their specific tolerance,
therefore magnetic fields may
be a possible problem.
The Josephson effect should be
noted. This is where current can
flow
between
two super
conducting material with nonsuper conductor or insulator in
between.
We could perhaps use this to
our advantage as we are
transporting the electricity over
such huge distances.
Ti-Ba-Cu-O or Yttrium Barium
Copper Oxide
This is a brittle ceramic material
but
it
reaches
its
superconductive state at 125
Kelvin, this is the highest of any
of the known superconductors.
We can reach this temperature
by use of liquid nitrogen (77
Kelvin).
The only problem we may
encounter in using this material
is that it does not have the
highest tolerance to magnetic
fields
Liquid Nitrogen
We can use a machine that will
compress nitrogen from 12 to
3,000 pound(p.s.i). The nitrogen
is compressed, cooled to room
temperature
and
then
expanded.
We could devise a system with
stations along the length of
wire pumping liquid nitrogen
into a tunnel within and around
the
superconductor
wire
maintaining
its
superconductive state and
regular
distance
intervals.
Compression due to sea water
weight to reduce energy use?
Niobium Titanium
Niobium Titanium would be our
second
option
of
superconductor. This material
reaches its superconductive
state at 10 kelvin ( which is
relatively lower that the Ti-BaCu-O).
Unlike Ti-Ba-Cu-O, however, it
can
withstand
greater
magnetic fields which would
be to our benefit considering
what we are dealing with is
electricity so large magnetic
fields will be present…
What properties does the wire
need to reduce resistance?
We can reduce resistance by:
a)
Increasing the diameter
of our cable, as G∞A
b)
Make the length of our
wire as short as possible,
as R∞L
Ownership
As the placement of the solar
panels could potentially be
placed over several countries
in Africa, there is the problem
of
which
country
would
effectively own the solar panel
plant.
If we use our case study of New
York, it would be ‘owned’ by
the United States of America
government.
However
this
would mean that there is no
security of there power supply.
This could cause some political
issues as is it fair for the US
government to ‘take’ land of
there use when many people
in Africa can not get any of the
supply their land is giving
people in the western world.
To resolve this the US could
agree to give some of the
energy to the countries whose
land has been used as well as
paying for the deeds of the
land.
However the country may not
have much needs or use for
the
energy,
there
an
agreement could be made
along the lines that the
government of the united
states will make an investment
in the countries education on
medical
systems,
thus
improving the state of living.
This will be beneficial as most of
the countries in Africa which
would receive this choice of
‘payment’ are LEDC’s.
Costing
The cheapest solar technology still works out
at $160 per megawatt hour (MWh),
compared with just $60 per MWh for
electricity produced by coal-fired power
stations and $80 per MWh for the most
efficient gas-fired power stations.
Case Study
Could we really power the world?

Energy consumption per year= 0.24 TWh

In the Sahara unpopulated land- 9 million km2

Sarah Solar panel- produce 126*10^18 Wh-electric /km²/year

This means a total of 1260000 TWh-electric/year.

This is over 15 times the earths demands!

Any one solar panel in the could catch on average – 12hrs of sun
New York?

New York uses 11000 MW per hour of electricity on average each day

Therefore only 16 km2 of Solar panels would power New York at any given moment

( not adjusted for energy loss during transmission, Double this area (32km^2) would make up for the 12 hours the desert spends in
the dark.) See calculation slide for workings.
Sources
http://www.livescience.com/23140-sahara-desert.html
https://engineering.purdue.edu/ME/Research/Areas/Mechanics/index.html
http://www.desertusa.com/du_sahara_life.html
http://online.unitconverterpro.com/conversion-tables/convert-group/factors.php?cat=energy&unit=10&val=10
http://cleantechnica.com/2011/12/14/solar-energy-from-the-sahara-desert-could-power-the-world-but-will-it/
www.luxuryloft.com
http://www.opb.org/news/blog/ecotrope/5-ways-to-store-renewable-energy/
http://physics.aps.org/articles/v6/100
http://energy.gov/oe/technology-development/energy-storage
http://www.daikin.co.uk/about-daikin/leading-technologies/heat-pump/
http://cdn.physorg.com/newman/gfx/news/2012/worldslonges.jpg
http://www.desertec.org/downloads/deserts_en.pdf
Calculations
The present global annual demand for primary energy arrives as solar energy in the deserts within 5.7 hours of sun shine. According to site
selection studies by DLR using satellite data the deserts in the MENA region would allow for production of electricity of 630,000 TWh/year,
about 40 times the present world electricity demand.
Calculations
Solar panels in the Sahara- 0.24 TWh-electric /km²/year.
New York uses 11000 MW hrs of electricity per day (luxury loft.com)
In the desert- 9 million km2 of uninhabited land cc (http://www.desertec.org/downloads/deserts_en.pdf)
Earths current consumption (2008): 26.164 Perrawatt hours per day (wikipedia)
Using all this land…How much energy could be produced per Year in the Sahara?
0.24*9000000= 2.16*10^18 Wh-electric/year.
Earths consumption
143.851 (petawatt hour)= 144*1015 watt-hours = 144*10^3 TWh
Ignoring resistance for now, the Sararah could produce…
2160000
144*10^3
= 15 times the Eaths energy demands!
Case Study
New York = 11000 MW hrs per day = 4015000 MW hrs per year
Solar panels in the Sahara- 0.24 TWh-electric /km²/year
4015000 MWh = 16 km of desert would be needed to supply energy to New York
0.24 TWh
The desert has an average of 12hrs sun therefore
2*16= 32 km needed