How it works Extreme weather

5 TOP Wind Nuclear Tidal Geothermal Hydro
FACTS
1 Wind is actually a form of solar 2 Nuclear reactors work by using 3 Tidal turbines (like under 4 Water that’s been turned into 5 From water wheels to massive
ALTERNATIVE energy caused by the Sun fission, the splitting of atoms water windmills), barrages or steam often escapes onto the dams, harnessing the energy
POWERS heating our atmosphere. Wind to produce energy. That wave turbines all use the surface of the Earth. of falling water is the basis of
farms simply use the wind to energy is used to create steam movement of the oceans or Geothermal power stations hydropower, making it the
drive a turbine that generates that drives a turbine to bodies of water to generate capture that steam and use it most efficient renewable
the electricity. produce electricity. their electricity. to drive turbines. energy source available.

DID YOU KNOW? Horace de Saussure built the first solar collector in 1776

Photovoltaic cells in action Whatgoesoninsideasolar
cell on an atomic level?

If the sun isn’t shining If the sun is shining

2x © Science Photo Library

1. Atoms are 2. Sunshine will excite 3. No electricity 1. Electrons 2. Some atoms will 3. A circuit is made
not excited the electrons is produced set free and electricity
remain attached
No sunlight means the Electrons will only break free Without free-moving Sunlight agitates the is produced
atoms remain at rest. when sunlight excites their electrons electricity can’t atoms until their Not all atoms
electrons are set free.
parent atoms. be generated. are dislodged to create The metal contacts make the

electricity. circuit thatilluminatesthe bulb.

How solar cells work

A layer-by-layer breakdown of what’s in a solar
cell and how the different parts work

Sun light Anti-reflection coating

The anti-reflection coating ensures
sunlight is absorbed by the
photovoltaic cell.

Upper metal contact

The electrical current flows
between each contact.

This photovoltaic barrier
was built in 2001 in
Freising, Germany

with ambitious plans to develop available solar cells, they’re only Glass cover Lower metal N-type (negative) silicon
more of their energy generation via around 18 per cent efficient. contact
solar power, while America is Photovoltaic cells Impure silicon is used to create the
planning to build the world’s largest However, this is still a massive need protection from Electrical current is captured negative part of the circuit.
solar power station. leap forward from the 3-5 per cent the weather. between the upper and
efficiency that early solar panels lower contacts. P-type (positive) silicon
All this talk of solar energy and could manage. The race is now on to Electron
the fact that the Sun delivers much develop more efficient photovoltaic transfer Silicon with boron impurities creates the
more energy than we need should cells to let us capture more of the positive component of the circuit.
be put into context – we don’t yet Sun’s precious energy. Current Sunlight frees
have highly efficient solar cells to research is looking at organic electrons from their
harness the free energy. If you photovoltaics, nanotechnology and parent atoms and
compare the output of your gas even the ability to print solar cells generates electricity.
boiler to that of the currently onto just about any surface.

151

THE WEATHER & US

Solar power

Solar Generating large amounts of power heliostats that track the movement of Some more advanced solar power
power needs more than a few panels. Solar the Sun and reflect its energy onto a stations also divert some of the steam
power stations generate electricity solar receiver on top of a tower at the generated and store this for future
by creating steam that drives a centre of the station. The tower use. This allows the power station to
turbine. The power to heat the water contains a boiler where the water is stay operational even at night, or
heated. Steam is then piped to steam when adverse weather conditions
stations comesfromtheSun. turbines that generate the electricity prevent the power station working at
Solar power stations use a series of fed into the grid for distribution. full capacity.
computer-controlled mirrors called

2. Solar receiver 1. Heliostats
track the sun
Solar energy is
collected and used to Mirrors move with the sun
generate power. to bounce the solar energy
onto the tower.
3. Heat storage
4. Steam turbine
Some power stations
store heat to allow Solar energy is used to
continuous electricity create steam that drives
generation. traditional turbines.

© Matanya 5. Power sent
to the grid
The mirrors track the
Electricity generated movement of the sun
by the solar farm is
distributed by the
electricity grid.

The PS10 plant in Spain
has 624 heliostats

© Science Photo Library

© Nosferatu it

ON THE 3

MAP 1
2
Worldwide solar 5 4
power generators 6

1 UK: 17 GWh The panels come in all © spg solar
2 Spain: 2,562 GWh shapes, sizes and formations
3 Germany: 4,420 GWh
4 Japan: 2,251 GWh
5 USA: 1,572 GWh
6 China: 172 GWh

SOURCE: Gross Electrical
Generation – Photovoltaics - 2008

152

HEAD BIG 1. International BIGGER 2. Howbery BIGGEST 3. Sarnia Photovoltaic
Space Station Business Park Power Plant
2HEAD
The photovoltaic arrays As the UK’s largest array Covering a gigantic 966,000m2,
SOLAR PANEL connected to the American of solar panels, the 3,000- the 1.3 million solar modules can
TECHNOLOGY modules generate about panels generate up to generate 80 megawatts of output to
32kW over a surface area 682 MWh and saves 350 power 12,000 homes in Sarnia,
of 375m2. tonnes of CO2 each year. Ontario, Canada.
© NASA
© solarcentury.co.uk
© courtesy of Enbridge Inc

DID YOU KNOW? The Sun is 150 million km (93 million miles) away from the Earth. Sunlight takes eight minutes to reach us

How to make and sell INTERVIEW
your own electricity
DuPont Senior
One of the great things about installing solar sell to your electricity supplier at an agreed rate. In Research
panels at home is that you can sell any surplus the United Kingdom this is currently 3p per kWh Fellow
electricity you generate to your local electricity (kilowatt hour). Dr Bill Borland
supplier. The feed-in tariff, or FIT, enables anyone
to gain a minimum payment for the electricity The practical upshot of FIT for anyone who What is the state of the specifically with regards to
they generate. installs solar panels and produces any excess is solar power industry their efficiency?
that they will receive a payment from their today? And has its uptake Today’s six-inch
FIT works in two ways. Your local electricity electricity company on an annual basis. The in businesses and homes monocrystalline industrial
company knows you generate your own power, so photovoltaic system that you install works with a been continuing to solar cell comprises a textured
fixes the payments you make for the electricity meter that not only measures how much increase? and passivated front face,
you buy from them. The other part of FIT comes electricity you are using from the mains supply, The growth of solar power has screen-printed silver contacts
into play when your photovoltaic cells generate but also what you are generating. This is how the been very impressive over the and a complete metal
more power than you can use. Any extra you can electricity company can calculate your payments. last few years, but it still coverage at the back. The first
represents less than one per cell in 1953 had an efficiency
Creating your Solar power cent of global electricity of 4.5 per cent. In 1960, with
own solar power converted to electricity production. The adoption of the introduction of the front
solar power by homes and finger grid, efficiency leapt to
Photovoltaic cells An inverter converts solar-generated business is primarily driven by 14 per cent. Full metal
government subsidies. Being coverage of the back in 1972
The installed photovoltaic cells power into AC electricity. ‘green’ is an added attraction. and texturing in 1974 raised
convert the Sun’s light energy Europe, particularly Germany, the value to 17 per cent. In
into electricity. has had attractive subsidies in 1975 screen-printed contacts
the form of feed-in tariffs that became common. Wafer
Mains power is Keeping track of usage have promoted tremendous sizes, however, were 2-3
still available growth in homes and inches. Since 1975, effort on
A mains electricity meter will track businesses. Growth in other increasing wafer sizes to six
When the Sun isn’t mains power and exported electricity. nations, such as the USA, is inches, Silicon Nitride
shining mains power emerging primarily from passivation in 2002 and
can still be used. Main distribution box business rooftop installations. improved contacts have
created today’s 17.5-18 per
Generated power is drawn just as if Could you describe the cent efficient solar cell.
it were mains power. process of making solar
cells? Are there any upcoming
Living off the grid The fabrication of a technologies that will
conventional crystalline silicon improve the efficiency of
Life without the basic utilities might sound like electricity is available when the Sun is absent. solar cell starts with texturing solar cells?
a nightmare for some, but for an increasing As photovoltaic cells can be attached to just one side of a boron-doped The drive-to-grid parity
number of people, living ‘off the grid’ has about any structure or used free standing, they silicon wafer that will become demands improved
become a lifestyle choice. These people have offer anyone who wants to live off the grid a the front face. The wafer then efficiencies without increasing
not simply installed a solar panel or two, but readily available source of power. undergoes a high-temperature cost. This means changes to
chosen to remove themselves completely from phosphorus diffusion process the conventional solar cell.
the tether most us have to the grid and the © NASA to form the P/N junction. After Technologies like selective
other utility providers. removing phosphorus silicon emitters and rear surface
glass, a by-product of the passivation are expected to
As you would expect, compromises have to diffusion process, a silicon become mainstream and each
be made. The amount of electricity you can nitride anti-reflection coating can raise efficiency by up to
generate will be dependent on the sunshine is applied to the front face. one per cent. Technologies on
you receive, and of course there will be no long This is followed by screen- the horizon include the use of
showers, nor running massive fridges when printing silver paste on the N base cells instead of P base
you’re living off the grid. front and aluminium and silver cells. N base cells are more
tabbing pastes on the back. tolerant to impurities, making
The power that is generated is usually stored The silver and aluminium them resistant to light-induced
in batteries for later use, and to ensure some pastes are rapidly co-fired to degradation of efficiency.
form the completed cell. Other developments include
metal wrap through and all
How do current solar cell back contact cells, which
technologies differ from could deliver efficiencies
those used in the past, greater than 20 per cent.

153

THE WEATHER & US

Solar Power Facility

Ivanpah Solar
Power Facility

See how the most advanced solar-powered
energy generation site produces electricity

The Ivanpah Solar Power receiver towers. This steam is then used
Facility is a brand-new solar directly to power electricity-producing
thermal power site located in turbines (see ‘Ivanpah step-by-step’
the Mojave Desert in western USA. The below to follow the process).
facility, which consists of three state-of-
the-art thermal power plants lies 64 Construction of the Ivanpah project
kilometres (40 miles) south-west of Las began in October 2010 and is to officially
Vegas and has a total capacity of 392 open in the latter part of 2013, with the
megawatts, making it one of the largest site set to contribute to California’s
of its kind in the world. existing electricity grid.
Ivanpah achieves this energy with
over 170,000 Sun-tracking heliostats However, the project has been seen
(mirrored panels), which receive a vast by some environmentalist
quantity of direct sunlight over the organisations as controversial due to its
1,415-hectare (3,500-acre) site and construction over an established
redirect it onto steam-producing ecosystem. In particular over 200 desert
thermal boilers mounted on top of three tortoises needed to be relocated during
the build, with a cost of $55,000 per
tortoise needed for the move.

Ivanpah step-by-step

From heliostat to energy grid, how does Ivanpah deliver so much power?

2. Receiver 5. Grid

A boiler at the top of Electricity is fed into
the tower is heated by the energy grid where
sunrays, converting it can be distributed
water into steam. around the region.

4. Storage

The spinning turbines
generate electricity,
while any excess heat
is stored in tanks.

1. Heliostat 3. Turbine

Software-controlled mirrors redirect the Steam from the boiler is
sunlight and focus it onto the receiver tower. then directed to a series
of turbines below.

154

2 REDUCTION IN

CO (TONS/YR)
THE 173,500 14.2km 400,000HELIOSTATS
LAND AREA
2

THERMAL
PLANTS
STATS MAXIMUM
392MW 1,079,232MWh 3IVANPAH FACILITY CAPACITY
ANNUAL POWER
GENERATION

DID YOU KNOW? The Ivanpah Solar Power Facility cost in the region of £1.4 billion ($2.2 billion) to build

© Ivanpah Solar

155

THE WEATHER & US

Power from the oceans

Great for surfing,
and for creating

electricity!

© Misty 07

Power from 1. Hot water throttle
the oceans
Warm surface water – between
Ocean thermal energy is the latest in 15-20°C (59-82°F) – is pumped
sustainable energy, here’s how it works through a collection tube and into
a heat exchanger.
The world’s oceans aren’t engineers are constructing the first large- But it doesn’t stop there. A second heat
separate bodies of water, but scale ‘energy island’ that will convert the exchanger pumps cold water from the 2. Heat to
one vast sea connected by potential energy of the ocean into a clean, depths to convert the ammonia vapour energy
global currents. As warm tropical inexhaustible source of electricity. back to a fluid state, ready to be reused in
currents reach high latitudes, the the closed-cycle system. No fuel is burned The heat exchanger
cooling water sinks and turns southward. The technology is called ocean thermal and zero emissions are produced. The captures the thermal
In certain tropical locations around the energy conversion (OTEC) and it’s nothing floating power plant can run 24 hours a energy of the warm
globe, the steamy surface currents short of revolutionary. The theory behind it day, 365 days a year exclusively on the heat water and uses it to
and deep icy flows cross paths, sees warm surface water pumped through differential of the ocean. boil ammonia, a fluid
creating tremendous temperature a heat exchanger, which pulls out the that turns to vapour at
differentials between the shallows and stored energy and uses it to boil an The pilot OTEC plant in Hawaii will -33°C (-28°F).
1,000 metres below. excitable fluid like ammonia. The forceful generate a constant ten megawatts of
Off the coast of Hawaii, where the steam produced by the evaporating electrical power, but commercial OTEC How
temperature gap between shallow and ammonia is funnelled into a generator, plants of the near future will easily reach OTEC
deep waters is a constant 20°C (36°F), where it rotates a sequence of turbine the 100-megawatt mark, enough to power a works
blades, generating electricity. small city.
How we get the energy
from the sea

156

5 TOP Seas of energy Sun sponge Limitless potential Squeaky clean New hope
FACTS
1 The belt of tropical waters 2 An incredible 80 per cent of 3 If we could capture even 4 A conventional coal-fired 5 Potential locations for OTEC
OTEC circling the planet stores 1,000 the solar energy that reaches one-tenth of one per cent of power plant for a small city sites include nations like
times more heat the Earth’s surface is then the energy stored in ocean coughs up millions of tons of Australia, but also third-world
than the Earth’s atmosphere, absorbed by the vast oceans waters, it will equal the daily CO2 per year. An OTEC plant countries like Haiti, where
a great potential source that cover every corner of electricity consumption of the powering the same city would clean OTEC power could
of energy. the globe. United States, times 20. produce zero. revitalise economies.

DID YOU KNOW? Every day, tropical waters absorb enough solar energy to equal heat generated by 250 billion barrels of oil

Fringe benefits toHHeaedad
of using OTEC
HYDROPOWER
During 35 years of OTEC research, Authority (NELHA), for example, are
engineers and scientists have discovered cooled year-round by deep seawater. DAMS
several other important, energy-saving Instead of refrigerating fresh water to
uses for OTEC technology. The offices of circulate through its air conditioning 1. Tidal power
the National Energy Laboratory of Hawaii system, NELHA pumps in 6°C (43°F)
seawater, saving $4,000 a month on its Hydroelectric power is commonly
Image © Lockheed Martin Image © Lockheed Martin electric bill. A luxury eco-resort in Bora generated by building a dam (or
Bora does the same thing. barrage) across an estuary to
store water in a reservoir. The
Fresh, desalinated drinking water is ebb and flow of the tides can
another valuable byproduct of OTEC be used to turn a turbine to
technology. Instead of using ammonia as produce electricity. The difference
a propellant, an ‘open-cycle’ OTEC in height between high tide and
system vaporises warm surface water in low tide can also be used to
a near vacuum to power the turbines. By collect the store of water to
condensing the water vapour with a blast be released.
of deep-sea air, you’re left with pure H2O.
WAVES
The electricity and fresh water created
by the open-cycle OTEC process can also 2. Wave power
be used to produce pure hydrogen, the
essential component of zero-emission The movement of waves over the
hydrogen fuel cells. Using a device called surface of the ocean can be
an electrolyzer, it’s possible to split fresh turned into electricity. Waves
water into hydrogen and oxygen. The travel as crests and troughs, and
precious hydrogen could then be shipped an object floating on the surface
to shore or around the world. will rise and fall accordingly. This
motion can be converted into
3. Steam engine electricity in a chamber at a wave
power station. The rising and
The intense flow of steam created by falling water causes air to be
the boiling ammonia is used to turn forced in and out of a hole in the
turbine blades inside a generator. top of the chamber. This air can
be used to power a turbine that
can generate electricity.

CURRENTS

4. Energy to electricity

The generator, using a simple magnetic
field, converts the rotation of the turbines
into electrical current.

7. Closed system 6. Cool condensation 5. Deep freeze Image © Lockheed Martin 3. The power of
the currents
The ammonia is pumped back The second heat exchanger captures the cooling Meanwhile, ice-cold
to the first heat exchanger, power of the deep seawater to convert the seawater – near 0°C The power of water can also be
where it is boiled again. No ammonia vapour back to a fluid state. (32°F) – from as deep harnessed using the oceans’
as 1,000 metres is currents. Installing large
y ammonia is burned and no fuel pumped into a second underwater turbines with rotors
is wasted. heat exchanger. capable of turning with the
surging movement of ocean
currents rushing past can be
used to generate clean electricity
to nearby coastal areas. The
main problem with this form of
energy is that the currents need
to be strong and the seabed
needs to be both shallow and near
to the coast.

157

THE WEATHER & US

Flood barriers

How flood
barriers work

A closer look at how these mechanical defences
are able to hold back great surges of water

Flood barriers are employed all over As tends to be the case with all the best Stormy waters
the world to prevent a sudden deluge engineering designs, the Thames Barrier is
of water from damaging property and based on a very simple concept. Each gate is The 1953 North Sea Flood was one
potentially taking lives. A few sandbags lining radial, using hollow cylinders that rotate the of the worst natural disasters to
the floor of a porch will be an effective defence barrier through 90 degrees according to happen in the UK in recorded
against a small flash flood, but something a whether they’re in open, flood control or history. It occurred when a high
little more robust is required to hold back the maintenance positions. Four central gates over spring tide combined with a
mighty swell of London’s Thames River. 20 metres (65 feet) high and weighing 3,300 tons severe storm over the North Sea,
In 1953, London and the surrounding area each span the middle section of the barrier, sending a swell that was
was badly hit by a flood that claimed 307 lives with two smaller gates next to them and four magnified in the narrow estuarine
and caused millions of pounds’ worth of non-navigable radial gates that sit above the channels along the coast. In places
damage. It prompted the creation of the river during normal flow. it reached up to 3.2 kilometres
Thames Barrier, an impressive feat of (two miles) inland, destroying
engineering that took eight years to build and When a potential storm is forecast to hit the 24,000 properties, 1,600
cost £534 million ($839 million) by the time it Thames Estuary, the barrier flood defence can kilometres (994 miles) of coastline
was completed in 1982. It stretches across 520 be erected in around 90 minutes. Two hydraulic and flooding 1,000 square
metres (1,706 feet) of the Thames near Woolwich cylinders move rocking beams that shift the kilometres (386 square miles).
and comprises ten separate gates on pivots gate into the closed position. Here, the Thames
supported by concrete piers that house the Barrier can hold back the downstream tide The Netherlands – parts of
machinery for operation of the gates. until it’s level with upstream again and safe which lie below sea level – was
to be opened once more. even worse hit: the country’s sea
defences buckled under the
pressure and killed 1,835 people,
30,000 animals and caused over a
billion Dutch guilders (about £360
million/$570 million) of damage.

158

STRANGE Seesaw Britain
BUT TRUE
Britain is actually tilting, with the northern and western regions like
BRITAIN’S TILTING Scotland and Wales rising, while southern and eastern parts of England
are sinking into the sea by 33 centimetres (13 inches) every century.

DID YOU KNOW? The Thames Barrier was hit by a dredger in thick fog in 1997, causing £13bn ($20.6bn) of damage

The Thames Barrier in action Downstream

Explore London’s impressive flood defence The river flows away
in both its open and closed positions from the barrier

downstream, except
when the tide comes in.

Gate

These are hollow and
the main gates can

withstand up to 9,000
tons of pressure.

Tidal flows

Open River flow
position River bed

Rocking beams Foundation

These rotate the cylinders The gates rest in these
on either side into position. recesses when they are

in the open position.

Surge

A potential storm flood will
flow from downstream
against the gate.

Closed River flow
position River bed

The Thames Flood Barrier The biggest barrier Upstream © v; Thinkstock; Rens Jacobs; John Webber
has been in operation
The Oosterscheldekering is the largest movable flood barrier in the world. Like The Thames flows into the
since 1982 and protects the Thames Barrier, this Dutch feat of engineering was built in response to the barrier from upstream.
125km2 (48mi2) of central 1953 North Sea Flood. It’s actually part of 13 dams known as Delta Works and is
London from tidal surges nine kilometres (5.6 miles) long, four kilometres (2.5 miles) of which include 159
huge sluice-gate doors that are normally open, but can be closed in the event of
a tidal surge. It comprises 65 concrete pillars weighing 18,000 tons each, with
62 steel doors, each 42 metres (138 feet) wide. Dutch engineers created an
artificial island in the centre of the estuary to facilitate the construction of the
structure and, unlike the Thames Barrier, which is estimated to be effective until
around 2030, Oosterscheldekering has a predicted lifetime of 200 years.

trialSpofefcieral

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BOOK OF

AND THE SCIENCE BEHIND EARTH’S FORCES OF NATURE

026 027 070 071 092 093

DEADLY WEATHER FORCES OF NATURE SPACE WEATHER

Master the skills needed to survive Witness how extreme weather Explore the otherworldly weather
killer weather events like megafloods, impacts our natural environment, from systems that emerge and exist within

heatwaves, cyclones and more... submarine volcanoes to acid rain our Solar System

SCIENCE OF WEATHER THE WEATHER & US

Discover the science behind the Take a look at the ways we attempt to
powerful natural phenomena that affect overcome, predict and exploit these

and shape life on planet Earth unstoppable forces of nature