. 13
( 16)


to accomplishing this.
• Carbon dioxide emission reduction policies can help to avoid very signi¬cant
supply challenges. This is especially the case for transportation. In both sce-
narios, oil and gas demand is substantially below the Baseline level in 2050.
In the BLUE Map scenario, oil demand is 27% below the 2005 level. Fossil fuels,
with large-scale application of carbon capture and storage, remain a key ele-
ment of the world™s energy supply in 2050 in all scenarios.

Projections for energy investment
The International Energy Agency has also estimated the future ¬nancial invest-
ment in global energy that will be necessary between 2005 and 2050 under
their Reference or Baseline Scenario and the additional investment required to
achieve the ACT and the BLUE Map energy scenarios.7
The total cumulative energy investment needs for the Reference scenario
over this period is estimated to be about $US250 trillion (million million) or
about 6% of cumulative world GDP over the period. By far the largest propor-
tion of this relates to investments that consumers make in capital equipment
that consumes energy, from vehicles to light bulbs to steel plants. In fact
because of very large investment in vehicles, transport alone accounts for
84% of the total investment. For the enviromentally driven scenarios over this
period, the additional investment needs are estimated as $US17 trillion for
the ACT scenario and $US45 trillion for the BLUE Map scenario or increases
of 7% and 18% respectively over the Reference scenario. For the BLUE Map
scenario, this is just over 1% of cumulative world GDP “ a ¬gure similar to
that quoted in Chapter 9 for the likely mitigation cost of stabilising CO2e at
450 ppm.
The IEA also point out that, compared with the Reference scenario, the ACT
and BLUE Map scenarios will result in signi¬cant fuel savings over the period
2005 to 2050, amounting to about $US35 trillion and $US50 trillion respectively.
These are substantially larger than the additional investment needs mentioned
in the last paragraph and the differences are not wiped out even if signi¬cant
levels of discount are applied in working them out (see Chapter 9, page 279 for
a discussion of discounting).

Socolow and Pacalas™ Wedges
A simple presentation of the type of changes that will be required has been created by Professors Socolow
and Pacala of Princeton University.8 To counter the likely growth of global carbon dioxide emissions from
2005 to 2055, seven ˜wedges™ of reduction are proposed (Figure 11.5), each wedge amounting to 1 giga-
tonne of carbon per year (= 3.66 gigatonnes of carbon dioxide per year) in 2055 or 25 gigatonnes in the
period 2005“55. Many combinations of technologies can be proposed to ¬ll the wedges. Some of the
possible ones are the following. They illustrate the scale of what is necessary.

• Buildings ef¬ciency “ cut electricity use by 25%
• Double fuel economy of 2 billion cars “ 30 to 60 miles per gallon (˜10 to 5 litres per 100 km)
• Install carbon capture and storage (CCS) at 800 large coal-¬red power plants
• Install CCS at coal plants that produce hydrogen for 1.5 billion vehicles
• Wind power from 1 million 2 MWp windmills
Solar photovoltaic power from area (150 km)2

• Nuclear power “ add 700 GW = 2 — current capacity
• Biofuel production from 250 Mha of land
• Halve tropical deforestation.

Note that Socolow and Pacala proposed wedges only suf¬cient to counter the emissions growth to 2055.
To meet the reductions to below 2005 levels in 2055 as in Figure 11.4 (b) or (c) requires 13 Gt per year of
reduction in 2055 or 13 wedges.

Fossil fuel emissions (GtC yr “1)



10 Stabilisation


fossil fuel emissions

2000 2010 2020 2030 2040 2050 2060

Figure 11.5 Socolow and Pacalas™ Wedges illustrate the changes required to counter
the likely growth of global carbon dioxide emissions from 2005 to 2055. Seven
˜wedges™ of reduction are proposed, each wedge amounting to a reduction of
1 gigatonne of carbon per year in 2055 ( = 3.66 gigatonnes of carbon dioxide per
year) or 25 gigatonnes in the period 2005“55. Many combinations of technologies
can be proposed, to ¬ll the wedges.
336 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

A long-term energy strategy
Before presenting details of the implementation, I want to step back and consider
how the choices between the great variety of proposed solutions and potential
technologies are to be made. It is relatively easy to present paper solutions, but
how do we decide between them and ¬nd the best way forward? There is no one
solution to the problem and no obviously best technology; different solutions
will be appropriate in different countries or regions. Simplistic answers I have
often heard are: Leave it to the market to provide, or The three solutions are Technology,
Technology, and Technology. The market and technology are essential and effective
tools, but poor masters. Solutions need to be more carefully crafted than those
tools that provide on their own.
Let me take the analogy of a motor boat with the engine representing technol-
ogy, and the propeller market forces (Figure 11.6). But where is the boat head-
ing? Without a rudder and someone steering, the course will be arbitrary or
even disastrous. Every voyage needs a destination and a strategy to reach it.
Some of the components of the necessary energy strategy are listed in the box
on the following page.
Absolutely key is the relationship between the economy and the environment;
they must be addressed together. It has been said that the economy is a wholly
owned subsidiary of the environment a view echoed by Gordon Brown, then the
UK ™s Chancellor of the Exchequer, in a speech in 2005.9
Take the market. It responds overwhelmingly to price and the short term.
It has been effective in reducing energy prices over the last two decades. But
in its raw form it takes no account of environmental or other external factors.
Economists for many years have agreed the principle that such factors should
be internalised in the market, for instance, through carbon taxes or cap and
trade arrangements, but most governments have been slow to introduce such
measures. An example where it is working comes from Norway where a carbon
tax makes it economic to pump carbon dioxide back into the strata from where
gas is extracted (see page 327). Aviation presents a contrary example where the
absence of economic measures is allowing global aviation to expand at a highly
unsustainable rate.

Buildings: energy conservation and ef¬ciency
If we turn lights off in our homes when we do not need them, if we turn down
the thermostat by a degree or two so that we are less warm or less cool or if we
add more insulation to our home, we are conserving or indeed saving energy.


(including environmental, social values)

Figure 11.6 Where are we heading? “ the need for an energy strategy. The boat ¬‚ies national and UN ¬‚ags
to illustrate the need for national and international strategies.

But are such actions signi¬cant in overall energy terms? Is it realistic to plan for
really worthwhile savings in our use of energy?
To illustrate what might be possible, let us consider the ef¬ciency with which
energy is currently used. The energy available in the coal, oil, gas, uranium,
hydraulic or wind power is primary energy. It is either used directly, for instance
as heat, or it is transformed into motor power or electricity that in turn provides
for many uses. The process of energy conversion, transmission and transfor-
mation into its ¬nal useful form involves a proportion of the primary energy
being wasted. For example, to provide one unit of electrical power at the point
of use typically requires about three units of primary energy. An incandescent
light bulb is about 3% ef¬cient in converting primary energy into light energy;
unnecessary use of lighting reduces the overall ef¬ciency to perhaps no more
than 1%.12 Assessments have been carried out across all energy uses comparing
actual energy use with that which would be consumed by ideal devices provid-
ing the same services. Although it is not easy to de¬ne precisely the perform-
ance of such ˜ideal™ devices (see box below for a discussion of thermodynamic
ef¬ciencies), assessments of this kind conclude that there are large opportuni-
ties for improvement in average energy ef¬ciency, perhaps by a factor of 3 or
more.13 In this section we look at possibilities for energy saving in buildings; in
later sections we consider possible savings in transport and in industry.14
To be comfortable in buildings we heat them in winter and cool them in sum-
mer. In the United States, for instance, about 36% of the total use of energy is in
buildings (about two-thirds of this in electricity), including about 20% for their
heating (including water heating) and about 3% for cooling.16 Energy demand
338 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Where are we heading? Components of energy strategy
(1) Planning for the long term must be a priority. Long timescales up to 50 or 100 years are involved in
many factors that make up the climate change issue, for instance, the lifetime of carbon dioxide in the
atmosphere, the lag due to the ocean in the realisation of climate change or the typical life of energy
(2) Not all potential technologies are at the same stage of development. Promising technologies need
to be brought to the starting gate so that they can properly compete. This implies joint programmes
between government and industry, the provision of adequate resources for research and develop-
ment, the creation of demonstration projects, and suf¬cient support to see technologies through to
maturity.10 Tidal and wave energy in western Europe provides an example (see page 368).
(3) Consideration needs to be given to social and ˜quality of life™ implications arising from the way
energy is provided to a community. For instance, energy provision from small local plants with
community participation possesses very different social and community characteristics compared
with energy from large, central installations. The best urban solutions may not be appropriate in
rural locations. Addressing more than one problem at once is also part of this component of the
strategy. For instance, disposal of waste and generation of energy frequently go together. It has
been estimated that the potential energy value in agricultural and forestry wastes and residues
could, if realised, meet at least 10% of the world™s total energy requirement.11 Local energy provi-
sion supporting the development of local industries would prevent depopulation and enable rural
areas to ¬‚ourish.
(4) Energy security is frequently mentioned and must be part of the strategy. For instance, how safe are
gas pipelines crossing continents and how secure from political interference at the other end? Or how
safe are nuclear power stations from terrorist attack or nuclear material from proliferation to terrorist
groups? Diversity of source is clearly important. But thinking about security could be more integrated
and holistic; energy security should not be disconnected from world security. As I will mention in
Chapter 12, world security is dependent on solutions being found for dealing with the threats to
human communities from climate change.
(5) Partnerships of many kinds are required as is stated and implied in the 1992 Framework Convention
on Climate Change. All nations (developed and developing) need to work together with national,
international and multinational industries and corporations to craft sustainable and equitable solu-
tions. Large-scale technology transfer from developed to developing countries is vital if energy growth
in developing countries is to proceed sustainably.
(6) Attainable goals, targets and timescales must be set, at all levels of society “ international, national,
local and personal. Any commercial company understands the importance of targets for successful
business. Voluntary action alone will fail to bring change on the required scale.

in the buildings sector grew by about 3% per year averaged worldwide from 1970 to
1990 and, apart from countries with economies in transition, has been growing
during the last decade by about 2.5% per year. How can these trends be reversed?17
To achieve the greatly increased energy ef¬ciency required from the build-
ings sector it is essential that there be an effective programme for retro¬tting
existing buildings with adequate insulation so as to reduce the requirement
for heating in winter (see box) and cooling in summer. Many countries, includ-
ing the UK and the USA, still have relatively poor standards of building insula-
tion compared, for instance, with Scandinavian countries. It is also essential
that all new domestic and commercial buildings are designed and constructed
to the highest possible standards so as to require the minimum energy input
(i.e. with higher insulation standards than those listed in the box) and with
maximum use of passive solar design (see box on page 362).19 Large energy sav-
ings can also be made by improving the ef¬ciency of appliances (see box) and
through installing simple control technology (e.g. based on thermostats) to
avoid energy waste. The cost of these actions would be less than the cost saved
through the saving of energy. Electricity companies in some parts of the USA
and elsewhere are contracting to implement some of these energy-saving meas-
ures as an alternative to the installation of new capacity “ at signi¬cant pro¬t

Thermodynamic ef¬ciencies
When considering the ef¬ciency of energy use, it can be important to distinguish between ef¬ciency as
de¬ned by the First Law of Thermodynamics and ef¬ciency as de¬ned by the Second Law. The second
particularly applies when energy is used for heating.
A furnace used to heat a building may deliver say 80% of the energy released by full combustion of the
fuel, the rest being lost through the pipes, ¬‚ue, etc. That 80% is a First Law ef¬ciency. An ideal thermo-
dynamic device delivering 100 units of energy as heat to the inside of a building at a temperature of 20 °C
from the outside at a temperature of 0 °C would require only seven units of energy. So the Second Law
ef¬ciency of the furnace is less than 6%.
Heat pumps (refrigerators or air conditioners working in reverse) are devices that make use of the Second
Law and deliver more energy as heat than the electrical energy they use.15 Although typically their Second
Law ef¬ciencies are only about 30%, they are still able to deliver more heat energy than the primary
energy required to generate the electricity they use. Because of their comparatively high capital and
maintenance costs, however, heat pumps have not been widely used. An example of their substantial
use is their contribution to district heating in the city of Uppsala in Sweden where 4 MW of electricity is
employed to extract heat from the river and deliver 14 MW of heat energy.
340 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Ef¬ciency of appliances
There is large potential for reducing the electricity consumption from appliances used in domestic or
commercial buildings. If, in replacing appliances, everyone bought the most ef¬cient available, their total
electricity consumption could easily drop by more than half.
Take lighting for instance. One-¬fth of all electricity used in the United States goes directly into light-
ing. This can easily be reduced by the wider use of compact ¬‚uorescent light bulbs which are as bright as
ordinary light bulbs, but use a ¬fth of the electricity and last eight times as long before they have to be
replaced “ with signi¬cant economic savings to the user. For instance, a 20-W compact ¬‚uorescent bulb
(equivalent to a 100-W ordinary incandescent light bulb) costing £3 or less will use about £20 worth of
electricity over its lifetime of 12 years. To cover the same period eight ordinary bulbs would be needed
costing about £4 but using £100 worth of electricity. The net saving is therefore about £80. A further
large increase in the ef¬ciency of lighting will occur when light-emitting diodes (LEDs) giving out white
light become commonplace.18 The latest such device which is about 1 cm2 in size and consumes only 3 W
produces the same light as a 60-W incandescent bulb.
The average daily electricity use from the appliances in a home (cooker, washing machine, dishwasher,
refrigerator, freezer, TVs, lighting) for typical appliances bought in the early 1990s amounts to about 10
kWh per day. If these were replaced by the most ef¬cient available now, electricity use would fall by about
two-thirds. The extra cost of the purchase of ef¬cient appliances would soon be recovered in the savings
in running cost. Similar calculations can be carried out for other appliances.

both to the companies and its customers. Similar savings would be possible in
other developed countries. Major savings at least as large in percentage terms
could also be made in countries with economies in transition and in develop-
ing countries if existing plant and equipment were used more ef¬ciently.
Further large savings can be realised when buildings are being planned and
designed by the employment of integrated building design. When buildings are
designed, the systems for heating, air conditioning and ventilation are com-
monly developed separately from the main design. The value of integrated
building design is that energy-saving opportunities can be taken associated
with the synergies between many aspects of the overall design including the
sizing of the systems where much of the energy use occurs. Many examples
exist of buildings that take advantage of the many ways of increasing energy
ef¬ciency including integrated building design, that reduce energy use by
50% or more and that are often more acceptable and user-friendly than build-
ings designed in more traditional ways.20 Some recent examples demonstrate
the possibility of more radical building designs that aim at Zero Emission

Insulation of buildings
About 1500 million people live in cold climates where some heating in buildings is required. In most coun-
tries the energy demand of space heating in buildings is far greater than it need be if the buildings were
better insulated (Figure 11.7).
Table 11.1 provides as an example details of two houses, showing that the provision of insulation in the
roof, the walls and the windows can easily lead to the energy requirement for space heating being more
than halved (from 5.8 kW to 2.65 kW). The cost of the insulation is small and is quickly recovered through
the lower energy cost.
If a system for circulating air through the house is also installed, so that incoming air can exchange heat
with outgoing air, the total heating requirement is further reduced. In this case it is worthwhile to add more
insulation to reduce the heating requirement still further.

Figure 11.7 An image of Aberdeen (Scotland, UK) from the air taken in the infrared in
the winter. Red buildings are warm as a result of poor insulation. Blue buildings are cool
showing they are well insulated. Red buildings include some of the older buildings near
the city centre but also some much more recent buildings in the outskirts.
342 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Table 11.1 Two assumptions (one poorly insulated, and one moderately well insulated)
regarding construction of a detached, two-storey house with ground ¬‚oor of size 8 m —
8 m, and the accompanying heat losses (U-values express the heat conduction of different
components in watts per square metre per °C)

Poorly insulated Moderately well insulated

Walls (150 m2 total area) Brick + cavity + block: Brick + cavity + block with
U-value 0.7 insulation in cavity of 75 mm
thickness: U-value 0.3
Roof (85 m2 area) Uninsulated: U-value 2.0 Covered with insulation of
thickness 150 mm: U-value 0.2
Floor (64 m2) Uninsulated: U-value 1.0 Includes insulation of thickness
50 mm: U-value 0.3
Windows (12 m2 total area) Single glazing: U-value 5.7 Double glazing with low emissivity
coating: U-value 2.0
Heat losses (in kW) with 10 °C
Roof 1.7 Roof 0.2
temperature difference from inside
to outside
Walls Walls
Windows Windows
1.1 0.45
0.7 0.2

Floor 0.7 Floor 0.2

Total heat loss (kW) 4.20 1.05
Add heat (in kW) needed for air 1.60 1.60
changes (1.5 per hour)
Total heating required (kW) 5.80 2.65

(fossil-fuel) Developments (ZED).21 The box illustrates a recent development in
the UK along these lines.
Ef¬ciency increases bringing cost savings sound very good in principle. In
practice, however, it is frequently found that much of the energy and cost saving
fails to materialise because of the increased comfort or convenience that comes
from increased energy use “ hence an increase in energy demand. Energy ef¬-
ciency measures need therefore to be associated with adequate public education
that explains the need for overall energy reductions.
Alongside the increases in energy ef¬ciency in buildings and appliances,
there need to be moves to carbon-free sources of energy supply to the buildings
sector. These will be addressed in later sections.

Example of a ZED (Zero Emission (fossil-fuel) Development)
BedZED (Figure 11.8) is a mixed development urban village constructed on a brown¬eld wasteland in the
London Borough of Sutton, providing 82 dwellings in a mixture of apartments, maisonettes and town
houses together with some work/of¬ce space and community facilities. 22 The combination of super-insu-
lation, a wind-driven ventilation system incorporating heat recovery, and passive solar gain stored within
each unit in thermally massive ¬‚oors and walls reduces the energy needs so that a 135 kW wood-fuelled
combined heat and power (CHP) plant is suf¬cient to meet the village™s energy requirements. A 109 kW
peak photovoltaic installation provides enough solar electricity to power 40 electric cars, some pool, some
taxi, some privately owned. The community has the capacity to lead a carbon-neutral lifestyle “ with all
energy for buildings and local transport being supplied from renewable sources.

Figure 11.8 The BEDZED development in south London, developed by the Peabody
Trust and designed by Bill Dunster Architects™.

Energy and carbon dioxide savings in transport
Transport is responsible for nearly one-quarter of greenhouse gas emissions
worldwide. It is also the sector where emissions are growing most rapidly
(Figure 11.9). Road transport accounts for the largest proportion of this, over
70%, shipping around 20% and air transport about 10%.23 The world population
344 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Figure 11.9 Historical and projected carbon 15
Historical data Estimated data (WBCSD)
dioxide emissions from transport by modes,
1970“2050. Projected data by the World
Business Council on Sustainable Development
(WBCSD) under a business-as-usual scenario;
historical data from the International Energy

Gt CO2 units
Agency. Air



1970 1980 1990 2000 2010 2020 2030 2040 2050

of light motor vehicles, currently around 750 million, is projected to rise by a
factor of 2 by 2030 and a factor of 3 by 2050, most of the growth occurring in
developing countries.24 This trend seems inevitable when account is taken of the
very large differences today in car ownership in different countries “ in terms
of persons per car, about 1.5 in the USA, 30 in China and 60 in India. Under
similar assumptions, by 2050 a growth in aviation is projected by a factor of 5,
again much of it in the developing world. Increased prosperity brings increased
demand for personal mobility and also increased movement of freight. In the
transport sector the achievement of reductions in carbon dioxide emissions will
be particularly challenging.
There are three types of action that can be taken to curb the rapidly growing
carbon dioxide emissions from motor transport (Figures 11.9 and 11.10). The
¬rst is to increase the ef¬ciency of energy and fuel use and to move to non-
fossil-fuel sources of energy. We cannot expect the average car to compete with
the vehicle which, in 1992, set a record by covering over 12 000 km on 1 gallon
of petrol “ a journey which serves to illustrate how inef¬ciently we use energy
for transport! However, it is estimated that the average fuel consumption of
the current ¬‚eet of motor cars could be halved through the use of existing
technology “ more ef¬cient engines, lightweight construction and low-air-re-
sistance design (see box on p. 346) “ while maintaining an adequate perform-
ance. Further, possibilities exist for the use of electric propulsion driven from
larger and more ef¬cient batteries or from fuel cells powered by hydrogen
fuel supplied from non-fossil-fuel sources. The second action is to plan cities
and other developments so as to lessen the need for transport and to make
personalised transport less necessary “ work, leisure and shopping should all


Latin America
150 Middle East
Energy consumption (EJ)

Water Other Asia
Eastern Europe
OECD Pacific
Freight trucks
OECD Europe
OECD N. America
Light duty vehicles
Bunker fuel
2000 2010 2020 2030 2040 2050 2000 2010 2020 2030 2040 2050
Year Year
Figure 11.10 Projected transport energy consumption by region and by mode projected by the World
Business Council on Sustainable Development (WBCSD) under a business-as-usual scenario.

be easily accessible by public transport, or by walking or cycling. Such planning
needs also to be linked with a recognition of the importance of ensuring that
public transport is reliable, convenient, affordable and safe. The third action is
to increase the energy ef¬ciency of freight transport by making maximum use
of the most energy-ef¬cient forms of freight transport, e.g. rail or water, rather
than road or air and by eliminating unnecessary journeys.
Air transport is growing even faster than motor transport. Global passenger air
travel, as measured in passenger-km, is projected to grow at about 5% per year over
the next decade or more and total aviation fuel use “ including passenger, freight
and military “ is projected to increase by about 3% per year, the difference being
due largely to increased fuel ef¬ciency.26 Further increases in fuel ef¬ciency are
expected but they are unlikely to keep up with the increase in the volume of air
transport. Biofuels as an alternative to kerosene are also being studied and are
assumed, for instance in the IEA BLUE Map scenario, to have replaced 30% of con-
ventional aviation fuel by 2050. Hydrogen has also been proposed as a long-term
possibility but the effect on the dry upper troposphere of injection of the resulting
water vapour has yet to be evaluated “ it would probably lead to an unacceptable
increase in cloud cover unless ¬‚ight altitudes were substantially lowered.
A further problem with air transport, mentioned in Chapter 3 page 63, is that
its carbon dioxide emissions are not the only contributor to global warming;
increased high cloudiness due to other emissions produce an effect of similar
or even greater magnitude. Operational changes to minimise this effect have
346 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Technologies for reducing carbon dioxide emissions from motor
An important recent development is that of the hybrid electric motor car that combines an internal
combustion engine with an electric drive train and battery.25 The gains in ef¬ciency and therefore fuel
economy achieved by hybrid vehicles are typically around 50%. They mainly arise from: (1) use of regen-
erative braking (with the motor used as a generator and captured electricity stored in the battery), (2)
running on the battery and electric traction only when in slow-moving or congested traf¬c, (3) avoiding
low-ef¬ciency modes of the internal combustion engine and (4) downsizing the internal combustion
engine through the use of the motor/battery as a power booster. Toyota and Honda were the ¬rst two
to introduce hybrid vehicles and other manufacturers are following. An imminent development is of the
plug-in hybrid which will enable the larger than normal car battery to be boosted by connecting with a
commercial electricity supply. For shorter journeys the plug-in hybrid could run only on the battery in
which case with fossil-fuel-free electricity, its carbon dioxide emissions would be eliminated.
Other signi¬cant ef¬ciency improvements are coming from the use of lower weight structural materials,
improvements in low-air-resistance design and the availability of direct injection diesel engines, long used
in heavy trucks, for automobiles and light trucks.
Developments are also occurring in battery technology that soon should enable more extensive employ-
ment of electric vehicles which will use electricity from wholly carbon-free sources. During the next few
years we will begin to see the introduction of vehicles driven by fuel cells (see Figure 11.24 below) based on
hydrogen fuel that can potentially be produced from renewable sources (see page 377). This new technol-
ogy has the potential eventually to revolutionise much of the transport sector.
Biofuels generated from crops can be employed to fuel motor vehicles thereby avoiding fossil fuel use.
For instance, ethanol has been extensively produced from sugar cane in Brazil. Biodiesel is also becoming
more widely available (see later section on biomass).

been proposed but more understanding of the mechanism is needed before seri-
ous work on its reduction can be carried out. Controlling the growing in¬‚uence
of aviation on the climate is probably the largest challenge to be solved in the
overall mitigation of climate change.

Energy and carbon dioxide savings in industry
Industry currently accounts for nearly one-third of worldwide primary energy
use and about one-quarter of carbon dioxide emissions of which 30% comes from
the iron and steel industry, 27% from non-metallic minerals (mainly cement)
and 16% from chemicals and petrochemicals production.27 Substantial oppor-
tunities exist for ef¬ciency savings in all these areas. The application of appro-
priate control technologies, other best-available technologies (BAT) and more
C A R B O N - F R E E E L E C T R I C I T Y S U P P LY

widespread combined heat and power (CHP) could bring 20“30% carbon dioxide
emissions reduction along with substantial net saving in cost “ such are known
as no-regrets actions. Other potential decreases in carbon dioxide emissions can
occur through the recycling of materials or waste (especially plastic waste), the
use of waste as an energy source and switching to biomass feedstocks or to less
carbon-intensive fuels.
Given appropriate incentives, substantial carbon dioxide savings can also
be realised in the petrochemical industry with signi¬cant savings in cost. For
instance, British Petroleum has set up a carbon emissions trading system within
the company that encourages the elimination of waste and leaks from their
operations and the application of technology to eliminate the venting of meth-
ane. In its ¬rst three years of operation, $US 600 million were saved and carbon
emissions reduced to 10% below 1990 levels.28
Carbon capture and storage (CCS “ see next section) is also an emerging
option for industry. It is most suited for large sources of off-gases with high car-
bon dioxide concentrations such as blast furnaces (iron and steel), cement kilns,
ammonia plants and also black liquor boilers or gasi¬ers (pulp and paper).
Industrial activity worldwide will increase substantially over the next few
decades especially in developing countries where there is large demand for
technology transfer that will enable the latest most ef¬cient technologies to
be employed. Because of this growth, in the absence of major actions to reduce
carbon dioxide emissions, they are bound to rise. However, the opportunities for
reductions are such that in the IEA BLUE Map scenario, emissions from industry
in 2050 fall to 22% below the 2005 level. The necessary policy instruments and
incentives to stimulate these reductions are discussed later in the chapter.

Carbon-free electricity supply
We have already noted that moving as rapidly as possible to carbon-free electric-
ity is key to achieving the level of overall reductions of carbon dioxide emissions
required by 2030 and 2050. Contributions to this movement can come in ¬ve
ways: (1) increases in ef¬ciency, (2) decreases in carbon intensity, (3) by widespread
deployment of carbon capture and storage, (4) by the use of nuclear energy, (5)
through the use of all possible renewable energies. From the long-term point of
view, (1) and (5) are the most important. I will now brie¬‚y address each in turn.
First, regarding energy ef¬ciency, the ef¬ciency of coal-¬red power sta-
tions, for instance, has improved from about 32%, a typical value of 20 or 30
years ago, to about 42% for a pressurised, ¬‚uidised-bed combustion plant of
today. Gas turbine technology has also improved providing ef¬ciency improve-
ments such that ef¬ciencies approaching 60% are reached by large modern
348 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

gas-turbine-combined cycle plants. Large gains in overall ef¬ciency are also
available by making sure that the large quantities of low-grade heat generated
by power stations is not wasted but utilised, for instance in CHP schemes. For
such co-generation, the ef¬ciencies attainable in the use of the energy from
combustion of the fuel are typically around 80%. The wider deployment there-
fore of CHP in building schemes or in industries where both heat and power
are required is an effective way of substantially increasing ef¬ciency at the
same time as producing savings in economic terms.29
Second, regarding carbon intensity, for a given production of energy, the
carbon dioxide emissions from natural gas are 25% less than those from oil and
40% less than those from coal. By switching fuel to gas, therefore, substantial
emissions savings can be made.
Third, an alternative to moving away from fossil fuel sources of energy is to
prevent the carbon dioxide from fossil fuel burning from entering the atmos-
phere by the employment of carbon capture and storage (CCS).30 Carbon
dioxide capture is arranged either by removing it from the ¬‚ue gases in a power
station, or the fossil fuel feedstock can, in a gasi¬cation plant, be converted
through the use of steam,31 to carbon dioxide and hydrogen (Figure 11.11). The
carbon dioxide is then relatively easy to remove and the hydrogen used as a ver-
satile fuel. The latter option will become more attractive when the technical
and logistic problems of the large-scale use of hydrogen in fuel cells to generate
electricity have been overcome “ this is mentioned again later in the chapter.
Various options are possible for the disposal (or sequestration) of the large
amounts of carbon dioxide that result. For instance, the carbon dioxide can
be pumped into spent oil or gas wells, into deep saline reservoirs or into
unminable coal seams. Other suggestions have also been made such as pump-
ing it into the deep ocean, but these are more speculative and need careful
research and assessment before they can be realistically put forward. In the
most favourable circumstances (for instance when power stations are close to
suitable reservoirs and when the extraction cost is relatively small), the cost
of removal, although signi¬cant, is only a small fraction of the total energy
cost. The IPCC has estimated a range of $US15“80 per tonne CO2 for the added
cost “ the cost of extraction being generally much larger than the cost of
The global potential for storage in geological formations is large and has
been estimated to be at least 2000 Gt carbon dioxide and possibly much larger.
The likely rate of leakage is believed to be very low although more research
is required into this rate and also into the risk of rapid release as a result, for
instance, of seismic activity.
C A R B O N - F R E E E L E C T R I C I T Y S U P P LY

Figure 11.11 Schematic of infrastructure for carbon dioxide Capture, transport and Storage. It illustrates
coal as the fuel, but it applies to oil- or gas-¬red power plants also or to any large concentrated source of
carbon dioxide.

Because of the rapid increase during the last few years in the number of new
coal-¬red power stations constructed globally (for instance, China is currently
adding capacity of 2 GW per week), the need for CCS technology has become
more acute. A substantial number of demonstration plants employing CCS need
to be built before 2015 in the USA, Europe, China, Australia and other countries
where coal remains a major source of power generation.32 Rapid deployment of
CCS to all new coal-¬red power stations would enable continuing use of fossil
fuels without the deleterious effects of carbon dioxide emissions.
A fourth source of carbon-free energy is nuclear energy.33 It has consider-
able attractiveness from the point of view of sustainable development because
it does not produce greenhouse gas emissions (apart from the relatively small
amount associated with the materials employed in nuclear power station con-
struction) and because the rate at which it uses up resources of radioactive
350 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

material is small compared to the total resource available. It is most ef¬ciently
generated in large units, so is suitable for supplying power to national grids
or to large urban conurbations, but not for small, more localised supplies. An
advantage of nuclear energy installations is that the technology is known; they
can be built now and therefore contribute to the reduction of carbon dioxide
emissions in the short term. The cost of nuclear energy compared with energy
from fossil fuel sources is often a subject of debate; exactly where it falls in rela-
tion to the others depends on the return expected on the upfront capital cost
and on the cost of decommissioning spent power stations (including the cost
of nuclear waste disposal), which represent a signi¬cant element of the total.
Recent estimates are that the cost of nuclear electricity is similar to the cost of
electricity from natural gas when the additional cost of capture and sequestra-
tion of carbon dioxide is added.
The continued importance of nuclear energy is recognised in the IEA energy
scenarios, which assume growth in this energy source in the twenty-¬rst cen-
tury. How much growth is limited in the short term by the shortage of per-
sonnel with the necessary skills for design and construction of nuclear power
systems and by the limited facilities available for building key components. In
the longer term, the amount of growth realised will depend on how well the
nuclear industry is able to satisfy the general public of the safety of its opera-
tions; in particular that the risk of accidents from new installations is negli-
gible, that nuclear waste can be safely disposed of and that dangerous nuclear
material can be effectively controlled and prevented from getting into the
wrong hands. Despite the substantial safeguards that are in place internation-
ally, this last possibility of the proliferation of dangerous nuclear material is
the one that, in my view, presents the strongest argument for questioning the
widespread growth of nuclear energy.34 However, proposals are now being pur-
sued for a fourth generation of nuclear power plants based on more advanced
reactors that promise to be safer, less productive of radioactive waste and with
much less danger of leading to nuclear proliferation. None of these, however,
are likely to be built before 2020 and maybe 2030.
A further nuclear energy source with great potential in the more distant
future depends on fusion rather than ¬ssion (see box below p. 377).
The ¬fth source of carbon-free energy is from the variety of renewable ener-
gies that have been identi¬ed and that are available. To put renewable energy
in context it is relevant to realise that the energy incident on the Earth from
the Sun amounts to about 180 000 million million watts (or 180 000 terawatts,
1 TW = 1012 W). This is about 12 000 times the world™s average energy use of
about 15 million million watts (15 TW). As much energy arrives at the Earth
from the Sun in 40 minutes as we use in a whole year. So, providing we can

harness it satisfactorily and economically, there is plenty of renewable energy
coming in from the Sun to provide for all the demands human society can con-
ceivably make.
There are many ways in which solar energy is converted into forms that we
can use; it is instructive to look at the ef¬ciencies of these conversions. If the
solar energy is concentrated, by mirrors for instance, almost all of it can be
made available as heat energy. Between 1% and 2% of solar energy is converted
through atmospheric circulation into wind energy, which although concen-
trated in windy places is still distributed through the whole atmosphere.
About 20% of solar energy is used in evaporating water from the Earth™s surface
which eventually falls as precipitation, giving the possibility of hydropower.
Living material turns sunlight into energy through photosynthesis with an
ef¬ciency of around 1% for the best crops. Finally, photovoltaic (PV) cells con-
vert sunlight into electricity with an ef¬ciency that for the best modern cells
can be over 20%.
Around the year 1900, very early in the production of commercial electricity,
water power was an obvious source and from the beginning made an important
contribution. Hydroelectric schemes now supply about 18% of the world™s elec-
tricity. Other renewable sources of electricity, however, have been dependent
on recent technology for their implementation. In 2005, only about 4% of the
world™s electricity came from renewable sources other than large hydro (these
are often collectively known as ˜new renewables™).35 Over half of this was from
˜modern™ biomass (called ˜modern™ when it contributes to commercial energy to
distinguish it from traditional biomass), the rest being shared between solar,
wind energy, geothermal, small hydro and marine sources.
Under the IEA BLUE Map scenario (Figure 11.12), all renewable sources will
be contributing by 2050 45% of total electricity production. The main growth
expected is in energy from ˜modern™ biomass and from solar and wind energy
sources. In the following paragraphs, the main renewable sources are described
in turn and their possibilities for growth considered. Most of them are employed
for the production of electricity through mechanical means (for hydro and
wind power), through heat engines (for biomass and solar thermal) and through
direct conversion from sunlight (solar PV). In the case of biomass, liquid or gase-
ous fuels can also be produced.

Hydropower, the oldest form of renewable energy, is well established and is com-
petitive economically with electricity generated by other means. Some hydro-
electric schemes are extremely large. The world™s largest, the Three Gorges
352 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Renewable power generation (TWh yr “1)
20 000
18 000
16 000
14 000
12 000 waste
10 000
solar power
6000 photovoltaic
4000 Wind
2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050

Figure 11.12 Growth of renewable power generation in the IEA BLUE Map energy
scenario, 2000“2050.

project on the Yangtze River in China, generates about 18 GW of electricity.
Two other large schemes, each of over 10 GW capacity, are in South America at
Guri in Venezuela and at Itaipu on the borders of Brazil and Paraguay. It is esti-
mated36 that there is potential for further exploitation of hydroelectric capac-
ity to two or three times the amount that has currently been developed, much
of this undeveloped potential being in Africa, Asia and Latin America. Large
schemes, however, can have signi¬cant social impact (such as the movement of
population from the reservoir site), environmental consequences (for example,
loss of land, of species and of sedimentation to the lower reaches of the river),
and problems of their own such as silting up, which have to be thoroughly
addressed before they can be undertaken.
But hydroelectric schemes do not have to be large; small hydroelectric sources
are increasingly providing an important resource. Many units exist that gener-
ate a few kilowatts only to supply one farm or a small village. The attractiveness
of small schemes is that they provide a locally based supply at modest cost.
Substantial growth in ˜small hydro™ “ much of it designed to run in-river “ has
occurred during the last decade or so, but only about 5% of the global potential
resource of 150 or 200 GW has yet been exploited.
An important facility provided by some hydro schemes is that of pumped
storage. Using surplus electricity available in off-peak hours, water can be
pumped from a lower reservoir to a higher one. Then, at other times, by revers-
ing the process, electricity can be generated to meet periods of peak demand.
The ef¬ciency of conversion can be as high as 80% and the response time a few
seconds, so reducing the need to keep other generating capacity in reserve.
Currently about 100 GW of pumped storage capacity is available worldwide but
the potential is considered to be at least ten times that ¬gure.

Biomass energy
Second in current importance as a renewable energy source is the use of bio-
mass.37 The annual global primary production of biomass of all kinds expressed
in energy units is about 4500 EJ (= 107 Gtoe). About 1% of this is currently turned
into energy mostly in developing countries “ we have labelled it ˜traditional bio-
mass™. It has been estimated that about 6% of the total could become available
from energy crops taking into account the economics of production and the
availability of suitable land.38 The energy so generated would represent about
75% of current world energy consumption, so in principle a large contribution
from biomass could be made towards global energy needs. It is a genuinely
renewable resource in that the carbon dioxide that is emitted when the biomass
is burnt is turned back into carbon, through the process of photosynthesis, in
the renewed biomass when it is grown again. The word biomass not only covers
crops of all kinds but also domestic, industrial and agricultural dry waste mate-
rial and wet waste material, all of which can be used as fuel for heating and to
power electricity generators; some are also appropriate to use for the manufac-
ture of liquid or gaseous fuels (see next section). Since biomass is widely distrib-
uted, it is particularly appropriate as a distributed energy source suitable for
rural areas. For instance, in Upper Austria, with a population of 1.5 million, in
2003 14% of their total energy came from local biomass “ planned to increase to
30% by 2010 and to continue to grow substantially thereafter.
In much of the developing world, most of the population live in areas where
there is no access to modern or on-grid energy. They rely on ˜traditional bio-
mass™ (fuelwood, dung, rice husks and other forms of biomass) to satisfy their
needs for cooking and heating. About 10% of world energy originates from these
sources, supplying over one-third of the world™s population. Although these
sources are in principle renewable, it is still important that they are employed
ef¬ciently, and a great deal of room for increased ef¬ciency exists. For instance,
a large proportion of each day is often spent in collecting ¬rewood especially by
the women, increasingly far a¬eld from their homes.
The burning of biomass in homes causes serious health problems and has
been identi¬ed by the World Health Organization as one of the most serious
causes of illness and mortality especially amongst children. For instance, much
cooking is still carried out on open ¬res with their associated indoor pollution
and where only about 5% of the heat reaches the inside of the cooking pot. The
introduction of a simple stove can increase this to 20% or with a little elabora-
tion to 50%.39 An urgent need exists for the large-scale provision of stoves using
simple technology that is sustainable “ although there is often considerable
consumer resistance to their introduction. Other means of reducing fuelwood
demand are to encourage alternatives such as the use of fuel from crop wastes,
354 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

of methane from sewage or other waste material, or of solar cookers (mentioned
again later on). From the existing consumption of ˜traditional biomass™ there
is the potential to produce sustainable ˜modern™ energy services with much
greater ef¬ciency and much less pollution for the 2 billion or so people who
currently rely on this basic energy source. A particular challenge is to set up
appropriate management and infrastructure for the provision of these services
in rural areas in developing countries (see box below).
Consider for instance the use of waste.40 There is considerable public aware-
ness of the vast amount of waste produced in modern society. The UK, for exam-
ple, produces each year somewhat over 30 million tonnes of domestic solid
waste, or about half a tonne for every citizen “ a typical value for a country
in the developed world. Even with major programmes for recycling some of it,
large quantities would still remain. If it were all incinerated for power genera-
tion (modern technology enables this to be done with negligible air pollution)
nearly 2 GW could be generated, about 5% of the UK™s electricity requirement.41
Uppsala in Sweden is an example of a city with a comprehensive district heating
system, for which, before 1980, over 90% of the energy was provided from oil. A
decision was then made to move to renewable energy and by 1993 energy from
waste incineration and from other biomass fuel sources provided nearly 80% of
what is required for the city™s heating.

Biomass projects in rural areas in the developing world
In much of the developing world, most of the population live in areas where there is little or no access to
electricity or modern energy services. There is large potential for creating local biomass projects to provide
such services. Figure 11.13 shows a schematic of a modern biogas plant and examples are given of pilot
projects,42 all of which could be replicated many times.

Rural power production, India
India, still a predominantly agriculture-based country, produces approximately 400 million tonnes of agro
waste every year. A fraction of this is used for cooking purposes and the balance is either burned or left to
decompose. India also imports large quantities of fossil-fuel-based furnace oil to supply power and heat to
millions of small-to large-scale urban/rural industrial units.
Linus Strategic Energy Solutions, an Indian company, are producing environmentally sustainable bri-
quettes from agro waste suitable for use as a fuel in these industrial units. In addition to the reduction in
costly and environmentally damaging fossil fuel use and the cash savings generated by the user, this cycle
also has the potential to generate new sources of income for farmers supplying the biomass, new business
opportunities for rural entrepreneurs processing and selling the briquettes and additional rural employ-
ment in the collection and processing of the agro waste.
Also in India, Decentralised Energy Systems India Private Limited are piloting the ¬rst independent
power projects of around 100 kW capacity in rural India owned and operated by village community

co-operatives. An example is a small co-operative in Baharwari, Bihar State, where a biomass gasi¬cation
power plant is used as a source of electricity for local enterprises, for instance for pumping water in the
dry season. Local income is thereby generated that enables villagers to expand their micro-industries and
create more jobs “ all of which in turn increases the ability of people to pay for improved energy services.
A ˜mutuality of interest™ is created between biomass fuel suppliers, electricity users and plant operators.

Integrated biogas systems, Yunnan, China
The South“North Institute for Sustainable Development has introduced a novel integrated biogas system
in the Baima Snow Mountains Nature Reserve, Yunnan Province. The system links a biogas digester, pig-
sty, toilet and greenhouse. The biogas generated is used for cooking and replaces the burning of natural
¬rewood, the ˜greenhouse™ pigsty increases the ef¬ciency of pig-raising, the toilet improves rural environ-
mental hygiene, and vegetables and fruits planted in the greenhouse increase the income of local inhabit-
ants. Manure and other organic waste from the pigsty and toilet are used as the raw material for biogas
generation which delivers about 10 kWh per day of useful energy (cf Figure 11.13). The operation of 50
such systems has considerably reduced local ¬rewood consumption.

Biomass power generation and coconut oil pressing, the Philippines
The Community Power Corporation (CPC) has developed a modular biopower unit that can run on waste
residue or biomass crops and can enable village-level production of coconut oil. CPC and local partners
are using the modular biopower unit fuelled by the waste coconut shells to provide electricity to a low-cost
mini-coconut-oil-mill (developed by the Philippines Coconut Authority and the University of Philippines),
16 of which are now operating in various Philippine villages. Furthermore, the biopower unit generates
waste heat which is essential for drying the coconuts prior to pressing.

Animal Village
barns home
Conveyor holder
Gas Reformer
Heat to scrubber
holding tank
Digester Lights
Liquid Stove Refrigerator
Fuel cell
fertiliser Village
fertiliser Cooling coils
Compost Hot water
industrial heat sinks

Figure 11.13 Schematic of digester for biogas plant for local supply (not to scale). The fuel cell for generating
electricity anticipates the availability of more advanced fuel cells. In the meantime the reformer and fuel cell
could be replaced by an internal combustion gas engine and a generating set.
356 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

But what about the greenhouse gas generation from waste incineration?
Carbon dioxide is of course produced from it, which contributes to the green-
house effect (see question 4 Chapter 3). However, the alternative method of
disposal is land¬ll (most of the waste in the UK currently is disposed of by
land¬ll). Decay of the waste over time produces carbon dioxide and methane
in roughly equal quantities. Some of the methane can be collected and used
as a fuel for power generation. However, only a fraction of it can be captured;
the rest leaks away. Because methane is a much more effective greenhouse
gas, molecule for molecule, than carbon dioxide, the leaked methane makes a
substantial contribution to the greenhouse effect. Detailed calculations show
that if all UK domestic waste were incinerated for power generation rather
than land¬lled, the net saving per year in greenhouse gas emissions would be
equivalent to about 10 million tonnes of carbon as carbon dioxide.43 Since this
is about 5% of the total UK greenhouse gas emissions, we can infer that power
generation from waste could be a signi¬cant contribution to the reduction in
overall emissions.
Other wastes resulting from human or agricultural activity are wet wastes
such as sewage sludge and farm slurries and manures. Bacterial fermentation
in the absence of oxygen (anaerobic digestion) of these wastes produces biogas,
which is mostly methane and which can be used as a fuel to produce energy
(Figure 11.13) There is room for an increasing contribution from these sources.
If the potential for power generation from agricultural and industrial waste
was taken into account, the savings in emissions arising from domestic waste
already mentioned could be approximately doubled.
Turning now to the use of crops as a fuel, the potential is large. Many different
crops can be employed as biomass for energy production. However, because of
the relatively low ef¬ciency of conversion of solar energy to biomass, the amount
of land required for signi¬cant energy production by this means is large “ and
it is important that land is not taken over that is required for food production.
An ideal energy crop should have high yields with low inputs. In energy terms,
inputs, for instance from fertilisers, crop management or transport, must be
no more than a small fraction of energy output. These characteristics tend to
rule out annual grasses such as maize but rule in, for instance, short-rotation
coppice willow from a list of woody species and Miscanthus (˜elephant grass™)
from a list of perennial grasses (Figure 11.14). Grasses like Miscanthus can also be
grown successfully on relatively poor land only marginally useful for agricul-
ture. Because biomass is bulky implying high transport costs, it is best used to
provide local energy or additional feed to large power stations.

In the IEA BLUE Map scenario, global biomass use (including biofuels, see
below) increases nearly fourfold by 2050 accounting for nearly one-quarter
of total world primary energy. It is then by far the most important renewa-
ble energy source. About half of this will come from crop and forest residues
and other waste, the other half from purpose-grown energy crops. These will
require a land area equivalent to about half the land area currently under agri-
culture in Africa or 10% of the world™s total.

Biofuels are currently produced from starch, sugar and oil feedstocks that
include wheat, maize, sugar cane, palm oil and oilseed rape. The best-known
example of their use comes from Brazil where since the 1970s large plantations
of sugar cane have produced ethanol for use as a fuel mainly in transport, gen-
erating, incidentally, much less local pollution than petrol or diesel fuel from
fossil sources. Residues from ethanol or sugar production are used to gener-
ate electricity to power the factories and to export to the grid, ensuring good
ef¬ciency for the total process both in terms of energy and of saving carbon
Decisions about the large-scale production of biofuels must be guided by thor-
ough and comprehensive assessments that address their overall ef¬ciency and
overall contribution to the reduction of carbon emissions.44 Also requiring care-
ful assessment is the degree to which their use of land is competing with food
crops (as for instance with the use of maize) or adding to deforestation of tropi-
cal forests (as for instance with some palm oil plantations) that itself contrib-
utes substantially to greenhouse gas emissions. Examples have recently come to
light of adverse consequences (for instance on world food prices) arising from a
lack of adequate assessment.
Energy is also available in cellulosic biomass “ as is evident from a cattle™s
rumen which turns grass into energy. On a laboratory scale, this process can
be replicated and biofuels produced from lignocellulose from grasses or woody
material or from the residue from cereal or other crops. A strong focus of
recent work is turning this into commercial large-scale production of biofuels
especially from woody wastes or from grasses such as Miscanthus grown on
marginal land where it is not competing with food crops. Already this is begin-
ning to happen and the scenarios I have presented assume that these second-
generation biofuels, as they are called, can be successfully developed on the
scale required.45
358 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Figure 11.14 Miscanthus
and willow growing at the
Institute for Grassland and
Environmental Research
(IGER), Aberystwyth

Wind energy
Energy from the wind is not new. Two hundred years ago windmills were a com-
mon feature of the European landscape; for example, in 1800 there were over
10 000 working windmills in Britain. During the past few years they have again
become familiar on the skyline especially in countries in Western Europe (for
instance, Denmark, Germany, UK and Spain) and in western North America.
Slim, tall, sleek objects silhouetted against the sky, they do not have the rustic
elegance of the old windmills, but they are much more ef¬cient. A typical wind
energy generator installed during the last decade will have three-bladed propel-
ler about 50 m in diameter and a rate of power generation in a wind speed of
12 m s“1 (43 km h“1, 27 mph or Beaufort Force 6), of about 700 kW. On a site with
an average wind speed of about 7.5 m s“1 (an average value for exposed places
in many western regions of Europe) it will generate an average power of about
250 kW. The generators are often sited close to each other in wind farms that
may include several dozen such devices. The size of the largest generators has
grown steadily, roughly doubling every ¬ve years, the largest now being 5 MW
to 6 MW units with rotor diameters of around 120 metres.
From the point of view of the electricity generating companies the dif¬culty
with the generation of electrical power from wind is that it is intermittent.
There are substantial periods with no generation at all. The generating compa-
nies can cope with this in the context of a national electricity grid that pools
electrical power from different sources providing that the proportion from
intermittent sources is not too large.46 Some public concern about wind farms

Wind turbines.

arises because of loss of visual amenity. Offshore sites, that are not seen to pos-
sess the same amenity disadvantage and that generally provide stronger and
steadier winds, are being increasingly used for large wind farms.
Rapid growth has occurred in many countries in the installation of wind
generators for electricity generation over the past decade “ a growth that con-
tinues unabated. Over 100 GW peak operating capacity has now (2008) been
installed worldwide providing about 1% of global electricity supply. With this
large growth, economies of scale have brought down the cost of the electric-
ity generated so that it is competitive with the cost of electricity from fossil
fuels. Because the power generated from the wind depends on the cube of the
wind speed (a wind speed of 12.5 m s“1 is twice as effective as one of 10 m s“1) it
makes sense to build wind farms on the windiest sites available. Some of these
are to be found in Western Europe where rapid growth in wind generation is
occurring. In Denmark, for instance, nearly 20% of electricity is now generated
by wind “ increasingly from wind farms being built offshore. Substantial off-
shore wind energy generation is also planned for the UK. Developing countries
are also making increased use of wind energy. For instance, India with 8 GW
360 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Wind power on Fair Isle
A good example of a site where wind power has been put to good effect is Fair Isle, an isolated island in
the North Sea north of the Scottish mainland.48 Until recently, the population of 70 people depended on
coal and oil for heat, petrol for vehicles and diesel for electricity generation. A 50-kW wind generator was
installed in 1982 to generate electricity from the persistent strong winds of average speed over 8 m s“1
(29 km h “1 or 18 mph). The electricity is available for a wide variety of purposes; at a relatively high price
for lighting and electronic devices and at a lower price controlled amounts are available (wind permitting)
for comfort heat and water heating. At the frequent periods of excessive wind further heat is available for
heating glasshouses and a small swimming pool. Electronic control coupled with rapid switching enables
loads to be matched to the available supply. An electric vehicle has been charged from the system to illus-
trate a further use for the energy.
With the installation of the wind generator, which now supplies over 90% of the island™s electricity,
electricity consumption has risen about fourfold and the average electricity costs have fallen from 13p per
kWh to 4p per kWh. A second wind turbine of 100 kW capacity was installed in 1996/7 to meet increasing
demand and to improve wind capture.

of installed capacity ranks as fourth in the world in wind generation. By 2050
under the IEA BLUE Map scenario, 12% of global electricity is projected to be
provided from wind energy.
Wind energy is also particularly suitable for the generation of electricity at
isolated sites to which the transmission costs of electricity from other sources
would be unacceptable. Because of the wind™s intermittency, some storage of
electricity or some back-up means of generation has to be provided as well. The
installation on Fair Isle (see box) is a good example of an ef¬cient and versatile
system. Small wind turbines also provide an ideal means for charging batteries
in isolated locations; for instance, about 100 000 are in use by Mongolian herds-
men. Wind energy is often also an ideal source for water pumps “ over 1 million
small wind machines are used for this purpose worldwide.47
In the longer term it can be envisaged that wind generation could expand into
areas remote from direct electrical connection providing an effective means
for energy storage can be developed (for instance, using hydrogen; more of that
possibility later in the chapter).

Energy from the Sun: solar heating
The simplest way of making use of energy from the Sun is to turn it into heat. A
black surface directly facing full sunlight can absorb about 1 kW for each square
metre of surface. In countries with a high incidence of sunshine it is an effec-
tive and cheap means of providing domestic hot water, extensively employed

Solar water heating
The essential components of a solar water heater (Figure 11.15) are a set of tubes in which the water ¬‚ows
embedded in a black plate insulated from behind and covered with a glass plate on the side facing the Sun.
A storage tank for the hot water is also required. A more ef¬cient (though more expensive) design is to
surround the black tubes with a vacuum to provide more complete insulation. Over 10 million households
worldwide have solar hot water systems.49
Figure 11.15 Design of a solar
water heater: a solar collector
connected to a storage tank
through a circulating pump.
Alternatively, if the storage is
above the collector, the hot
water will collect through
gravity ¬‚ow.


Pump storage

in countries such as Australia, Israel, Japan and the southern states of the USA
(see box). In tropical countries, a solar cooking stove can provide an ef¬cient
alternative to stoves burning wood and other traditional fuels. Thermal energy
from the Sun can also be employed effectively in buildings (it is called passive
solar design), in order to provide a modest boost towards heating the building
in winter and, more importantly, to provide for a greater degree of comfort and
a more pleasant environment (see box).

Energy from the Sun: concentrating solar power
Solar energy can be converted into electricity either through its heat energy
focused on to a boiler, for instance, to produce steam “ known as concentrating
solar power (CSP) “ or by means of photovoltaic (PV) solar cells (see box). It is
widely agreed that both possess the potential to be large contributors to glo-
bal renewable energy. For instance, the current electricity needs of the United
362 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

Solar energy in building design
All buildings bene¬t from unplanned gains of solar energy through windows and, to a lesser extent, through
the warming of walls and roofs. This is called ˜passive solar gain™; for a typical house in the UK it will con-
tribute about 15% of the annual space heating requirements. With ˜passive solar design™ this can relatively
easily and inexpensively be increased to around 30% while increasing the overall degree of comfort and
amenity. The main features of such design are to place, so far as is possible, the principal living rooms with
their large windows on the south side of the house in the Northern hemisphere, with the cooler areas
such as corridors, stairs, cupboards and garages with the minimum of window area arranged to provide a
buffer on the north side. Conservatories can also
be strategically placed to trap some solar heat in
the winter.
The wall of a building can be designed speci¬-
cally to act as a passive solar collector, in which
case it is known as ˜solar wall™ (Figure 11.16).50
Flap to control reverse Its construction enables sunlight, after passing
flow at night
through a double-glazed window, to heat the sur-
face of a wall of heavy building blocks that retain
the heat and slowly conduct it into the building. A
retractable re¬‚ective blind can be placed in front
Thermal storage wall of the thermal wall at night or during the summer
when heating of the building is not required. A
set of residences for 376 students at Strathclyde
University in Glasgow in southwest Scotland has
been built with a ˜solar wall™ on its south-facing
Opening to permit air flow
side. Even under the comparatively unfavourable
conditions during winter in Glasgow (the average
duration of bright sunshine in January is only just
Figure 11.16 Construction of a ˜solar wall™, sometimes
called a Trombe wall. over one hour per day) there is a signi¬cant net
gain of heat from the wall to the building.

States could be generated from the solar energy falling on PV cells over an area
of 400 km square or on CSP installations covering a somewhat smaller area.
However, at the present time for large-scale electricity provision, neither is com-
petitive in cost with conventional energy sources or with wind energy. Both
require suf¬cient injection of investment for research and development to grow
the economies of scale required to bring costs down to acceptable levels. I will
address CSP and PV in turn.


Stirling engine

Cold piston

Hot piston


Cooler Heat in



Heat out

Figure 11.17 A concentrating solar power (CSP) system for electricity generation, that consists of a solar
thermal array of a number of dish-shaped mirrors each focusing radiation on a receiver attached to a Stirling
engine (see bottom left) that converts heat into electricity.
364 E N E RG Y A N D T R A N S P O R T F O R T H E F U T U R E

The photovoltaic solar cell
The silicon photovoltaic (PV) solar cell 51 consists of a thin slice of silicon into which appropriate impu-
rities have been introduced to create what is known as a p“n junction. The most ef¬cient cells are
sophisticated constructions using crystalline silicon as the basic material; they possess ef¬ ciencies for
conversion of solar energy into electricity typically of 15% to 20%; experimental cells have been
produced with ef¬ciencies well over 20%. Single crystal silicon is less convenient for mass production
than amorphous silicon (for which the conversion ef¬ ciency is around 10%), which can be deposited
in a continuous process onto thin ¬ lms. Other alloys (such as cadmium telluride and copper indium
diselenide) with similar photovoltaic properties can also be deposited in this way and, because they
have higher ef¬ciencies than amorphous silicon, are likely to compete with silicon for the thin-¬ lm mar-
ket.52 However, since typically about half the cost of a solar PV installation is installation cost, the high
ef¬ciency of single crystal silicon, which means a smaller size, remains an important factor. A number
of new PV materials or devices are also under intensive investigation some of which are beginning to
compete in terms of ef¬ ciency or cost.
Cost is of critical importance if PV solar cells are going to make a signi¬cant contribution to energy sup-
ply. This has been coming down rapidly. More ef¬cient methods and larger-scale production are bringing
the cost of solar electricity down to levels where it can compete with other sources. The decline in cost
with increase in installed capacity over the last 25 years and a projection for the next 5 years is illustrated
in Figure 11.18.
PV module cost ($ per watt-peak)




1 10 100 1000 10 000 100 000
Cumulative installed capacity (in MW)
Figure 11.18 The increase in installed capacity and the falling cost of PV
modules over the last 25 years and (dashed) projected into the future (data
from 1982“2002 from Shell Renewables and from 2002“2007 from Energy
Technology Perspectives, International Energy Agency 2008).

In CSP, to produce a suf¬ciently high temperature at the boiler, the solar
energy has to be concentrated using mirrors (Figure 11.17). One arrangement
employs trough-shaped mirrors aligned east“west which focus the Sun on to an


. 13
( 16)