1. driver,making a material difference in energy

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Making a material difference in energy$,$$

David Driver ,1

Materials UK —Energy Materials Group

a r t i c l e i n f o

Available online 23 October 2008

Keywords:

Energy conservationTurbine materials

Fuel cells

a b s t r a c t

The extraction of fuels and their conversion into power requires an extensive range of materials. Energy

reserves are increasingly found deep underwater or far below the ground, and in severe locations.

The containment and use of energy resources imposes further constraints on structural materials, fromthe subzero conditions of liquefied gas containers to the containment of gas plasmas at several

thousand degrees in fusion reactors. Structural materials have been developed to meet many of these

requirements, but cheaper and longer-lasting alternatives are needed.

As intermittent distributed power becomes more common, new materials are needed for fuel cells,

combined heat and power, wind and wave power, and energy storage. As well as offering higher

efficiency, new materials will cut the cost of energy generation and storage. Fuel-efficient transport and

low-energy electrical equipment will also call for new materials, as will renewable energy and the

‘hydrogen economy’. The possible reinvigoration of nuclear power and the development of fusion will

also pose continuing challenges for materials science. Energy materials priorities are identified for each

of these important technology areas.

& 2008 Queen’s Printer and Controller of HMSO. Published by Elsevier Ltd. All rights reserved.

1. Materials priorities for energy

1. Materials for energy conservation

The Energy White Paper (EWP) states that ‘the cheapest,

cleanest and safest way to meet emission targets is to use

less energy’. Many of those energy savings will be achieved

through the use of ‘smart’ functional materials and low-

energy materials processing. Specific examples are given

later. Energy conservation is the No. 1 materials priority. By

2050 most energy consuming equipment will be monitored

and controlled with minimum human intervention.

2. Materials for turbine technology

There is strong materials synergy across high-temperatureturbine technology in areas such as condition monitoring,

durability and extended component lifetimes. Competitive ad-

vantage can be obtained from transferable materials solutions.

Information on high-integrity structural materials was

dispersed during electricity and nuclear divestment. That

valuable information should be collected and disseminated

within the UK Energy community. The Materials Foresight

Energy Group should act as facilitator and focus for UK and

international collaboration.

By 2050 UK experience on structural materials for turbine

technology should be widely exploited within the UK and in

developing nations, such as China and India, which hold a

quarter of current coal reserves.

Turbine technology for lower temperature wind and waveapplications is considered later, together with materials for

energy storage of such distributed intermittent power.

3. Materials for fuel cell technology [and hydrogen storage]

Fuel cells offer independent means of generating electricity

in a low-carbon economy and can be incorporated into

gasification plant to increase efficiency. New electrode and

membrane materials are needed for more efficient power

generation with solid-state hydrogen storage providing a

safe means of handling the new fuel. This third priority

complements energy conservation and clean coal.

4. Functional materials for energy generation and conservation

Functional/smart materials offer opportunities for direct

energy conversion [e.g. photovoltaic solar panels] or

ARTICLE IN PRESS

Contents lists available at ScienceDirect

journal homepage: w ww.elsevier.com/locate/enpol

Energy Policy

0301-4215/$- see front matter & 2008 Queen’s Printer and Controller of HMSO. Published by Elsevier Ltd. All rights reserved.doi:10.1016/j.enpol.2008.09.061

$While the Government Office for Science commissioned this review, the views

are those of the author(s), are independent of Government, and do not constituteGovernment policy.$$ Since this brief review was produced Materials UK (Mat.UK) has expanded

the discussion in a series of Materials UK Energy Review 2007 documents:

Report 1: Energy materials: strategic research agenda

Report 2: Fossil-fuelled power generation

Report 3: Nuclear energy materials

Report 4: Alternative energy technologies

Report 5: Energy transmission, distribution and storage

The reports are available via www.matuk.co.uk/energy.htm. Tel.: +44 1509843391.

E-mail address: [email protected] Home Address: 33 West End, Long Whatton, Loughborough, Leicestershire

LE12.5DW, UK.

Energy Policy 36 (2008) 4302–4309

http://www.sciencedirect.com/science/journal/jepo

http://www.elsevier.com/locate/enpol

http://localhost/var/www/apps/conversion/tmp/scratch_2/dx.doi.org/10.1016/j.enpol.2008.09.061

http://www.matuk.co.uk/energy.htm


mailto:[email protected]

mailto:[email protected]


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energy-saving devices [e.g. light-emitting diodes (LEDs)

and liquid crystal displays]. They supplement but do not

supplant earlier technology.

By 2050 ‘smart’ functional materials will be used in

buildings, transport and equipment to sense, monitor and

control power requirements for domestic and industrial

needs. Such materials were discovered 50 years ago. In

another 50 years they will be all pervasive and verysophisticated. Current multi-billion dollar silicon wafer

processing technology may be replaced by alternative lower

cost coating technology. New nanostructured materials may

provide the base from which the functional revolution can

take place.

5. Nuclear fission and fusion materials

The nuclear sector is already designing fusion and Genera-

tion IV fission reactors. Materials development for these

structures illustrates the way to the future:

By 2050 there will be sufficient understanding of materials

properties and long-term degradation mechanisms to allow

computer-based analysis and prediction of behaviour from

an atomic level to full engineering structures. Computing

power will allow a range of design options to be considered,built, tested and operated in a virtual environment. Full

validation is needed but virtual design and manufacture

will allow several design iterations before an optimum

structure is chosen.

New processing routes for structural materials are likely to

include near-net-shape manufacture whereby material and

component are built up together. It is wasteful of material,

time and energy, to produce bulk commodity products from

which intricate shapes are then machined. Coatings and

particle processing [e.g. laser deposition] will be manufac-

turing routes of the future.

6. New material options for energy

Although much future structural materials development

will be incremental, there are potential ‘step change/

disruptive materials’ that may transform the future.

Nanostructures are such a family. Carbon nanotubes are

only a few nanometres in diameter [50,000 times smaller

than the width of a human hair] yet they are the world’s

strongest known material. They can be incorporated into

such diverse materials as concrete and polymer composites

to significantly increase strength. They can also be joined

together to form functional/semiconductor devices for solar

cells and can act as membranes for filtering CO2 emissions.

It would be fitting if this new carbon-based material could

provide the basis for a next-generation low-carbon econo-

my. Considerable material development is, however, needed

to overcome expensive processing routes and health and

safety issues.

2. Priority 1—conservation/optimised energy use

2.1. Energy White Paper 2003: [EWP, Para 1.10/18 and 1.40]

‘‘To reduce CO2 emissions by some 60% from current levels by

2050’’.

2.2. Lightweight structural materials for transportation

Transport accounts for 35% of total UK energy consumption

[EWP Chart 1.5]. Lightweight structures could greatly reducethat figure. Transporting a 0.1-ton human being in a 1.5-ton car is

not energy efficient. Composite body structures (Fig. 1) can halve

current fuel consumption. They should be more widely used.

Practical vehicles powered by fuel cell technology are expected

by 2010. A major issue is storage of hydrogen fuel [see later].

For safety reasons, metal hydrides are favoured. A hydride tank

is about 3 times larger and 4 times heavier than a petrol tank

with the same fuel energy. This weight disadvantage will affect

fuel consumption, even though emissions are environmentallyfriendly!

2.3. Green light on energy saving

The US has calculated that switching its 100 M traffic lights

from incandescent bulbs to LEDs (Fig. 2) would save $190 Mp/a

and reduce energy consumption by 3 billion KW/h. This is

equivalent to eliminating emissions from 443,000 cars each

year [http://optics.org]. UK could make similar savings from

LED lighting [traffic lights, warning signs, floodlighting, etc.]

In the energy-efficient world of 2050, most lighting will use

LEDs. Materials development will further improve efficiency.

Future success depends on effective product champions and a

responsible approach by all to energy conservation.

2.4. TV viewing

Individuals might choose energy-saving technology if better

informed. A 55 in. plasma TV costs nearly $150 p/a in energy

ARTICLE IN PRESS

Fig. 1. General Motors ultra-lite composite vehicle [www.scaled.com]

Fig. 2. Colour-specific light-emitting diodes.

D. Driver / Energy Policy 36 (2008) 4302–4309 4303

http://optics.org/

http://www.scaled.com/

http://www.scaled.com/

http://optics.org/



compared with o$15 p/a for current smaller liquid crystal

display (LCD) sets. [http://reviews.cnet.com]. Large plasma

screens consume as much power as an average freezer.

Freezers have an energy rating. TVs do not. LCD technology

is also suitable for larger screens. In October 2004, 40–45 in.

LCD TVs became widely available. In March 2005, Samsung

announced an 82in. panel [http://www.samsung.com]. These

large LCDs are much more energy efficient than plasmascreens. Materials development continues.

By 2050 such low-energy equipment will be common place.

Flexible polymers may have become the visual medium with

semiconductor pixels ink-jet printed onto the surface. This

technology is now being developed; it would allow moving

images on flexible display screens that could be hung on walls

or even worn in clothing! The future is bright thanks to

innovative materials technology.

2.5. Power to the people

Average UK housing stock has a life expectancy of well over

100 years. Installing best energy practice on all new buildings

would not significantly influence energy consumption for several

ARTICLE IN PRESS

Fig. 3. Plasma screen (L) and LCD (R) televisions.

Fig. 4. Coal-fired steam turbine power station.

D. Driver / Energy Policy 36 (2008) 4302–43094304

http://reviews.cnet.com/

http://www.samsung.com/

http://www.samsung.com/

http://reviews.cnet.com/



decades. Retrofitted energy-saving technology to mature proper-

ties is needed. ‘Smart’ structures that identify and reduce wasteful

energy usage, glass with controllable thermal transmittance, andpower management devices for optimised operation are available.

There are many materials options for energy conservation that

should be more widely used (Figs. 3–5).

3. Priority 2—turbine technology

3.1. Energy White Paper 2003

‘‘Coal fired power generation helps widen diversity of the

energy mix, provided ways can be found y to reduce carbon

emissions. We will ysupport research to develop y cleaner coal

technologies and carbon capture/storage’’ [EWP, Para 1.25].

Continued use of fossil fuels in electricity generation will

require the use of carbon capture and storage (CCS) to severelyrestrict CO2. DTI has developed a Carbon Abatement Technologies

(CAT) Strategy [DTI/Pub. URN 05/844] in which there are a range

of material challenges. These include new high-temperature

oxidation/corrosion-resistant materials to meet the changed

combustion environments from oxy-combustion or the need to

separate CO2 and hydrogen from gasification using functional

separation membranes [also see below]. The CAT Strategy high-

lights biomass co-firing, which will lead to more aggressive boiler

environments [e.g. superheater corrosion]. Gasification offers a

near-term route to hydrogen generation and to the future use

of chemical feedstocks for power.

3.2. Key material science advances

The Clean Coal Technology Review of October 2002 [Status

Report 18—Advanced Materials for Power Generation] has

called for an integrated R&D programme in 3 priority area-

s—high-temperature materials, protective systems and modelling .

The latest turbines use ultra-supercritical steam at up to

700 1C/375 bar for high thermal efficiency. Structural steels are

being developed via European collaboration while Japan is

pursuing an independent materials programme.

Continued materials R&D is needed to reduce emissions [SO x,

NO x and CO2] Feasible materials solutions are possible in

the short term for SO x and NO x. Carbon dioxide isolation

(sequestration) requires longer-term R&D. While improved

high-temperature turbine materials will be available by 2050

there is further scope for ambitious new high-temperatureblade/coating combinations and for less bulky integrally

bladed turbine discs/rings or even structural ceramic materi-

als. These options (and others) are being explored on aero-

engine gas turbines and could be transferred to power

turbines. Demonstration plant is needed to test both the

operating economics and the long-term effectiveness/structur-

al integrity of new systems. Europe and US programmes have

been introduced to build zero-emission coal-fired power plant

incorporating fuel cell technology to produce hydrogen andelectricity with carbon capture and storage to remove CO2.

They should be extended for other fuel options [oil gas, waste].

3.2.1. High-temperature power generation materials

Developments are required in:

New alloys for ultra-supercritical conditions.

Alloy development specifically for industrial gas turbines to

improve alloy stability, corrosion resistance and reduce costs

through higher yields.

Advanced manufacturing methods and joining techniques toreduce costs and offer greater structural integrity.

High strength rotor discs with improved processing, NDT and

life prediction

Advanced alloys and [ceramic] composites specifically for

power generation

Ceramic and metallic hot gas filters for clean gasification and

combustion.

Metallic membrane development for CO2 separation in coal-

fired plant.

Carbon nanotubes are being developed for membrane applica-

tions. Nanostructure filters with over a trillion microscopic pores

per square inch allow gases and liquids to flow rapidly but block

larger molecules. Such filters have potential application indesalination plant and for removing CO2 from emissions.

3.2.2. Coatings technology

Coating technology has been identified as a critical area for

future materials development and includes thermal/corrosion

barriers for protection of combustion components in biomass and

waste-to-energy. Nano- and smart coatings that respond to their

environment are examples of coating trends. Many coating

compositions can be applied today. Further developments are

anticipated.

3.2.3. Computer modelling By 2050, materials development and structural design options

for zero-emissions will be undertaken by computer modelling.

UK has considerable experience in this area. That knowledge

should be used to competitive advantage.

3.2.4. Oil, gas, biomass and waste incineration

Materials issues for oil, gas, biomass and waste are similar

to coal technology. Gas mixtures are, however, more complex and

corrosion attack is more severe. Emissions control is needed,

particularly for undifferentiated waste, but economics preclude

sophisticated treatments. Specific material options are available

for particular fuels. The choice is between new alloys for high

corrosion resistance or ‘like-for-like’ replacement with low-costmaterials. Currently the tendency is for cheap replacement.

ARTICLE IN PRESS

Fig. 5. A solid oxide fuel cell (SOFC) stack [www.ikts.fraunhoffer.de ].


http://www.ikts.fraunhoffer.de/

http://www.ikts.fraunhoffer.de/



4. Priority 3—fuel cell technology

4.1. Fuel cell types

Portable hydrogen-powered proton exchange membrane

or polymer electrolyte membrane fuel cells (PEMFC) have

potential for use in cars and power packs [e.g. cameras, mobile

phones]. Water management, CO2 poisoning, cooling, andhydrogen storage are operational issues. Material options are

discussed below.

Direct methanol fuel cells (DMFC) use methanol, rather than

hydrogen to feed the fuel cell. Storage of liquid methanol is

easier than gaseous hydrogen and energy density is also orders

of magnitude greater. Efficiency is, however, low and methanol

is poisonous. Oxidation at the catalytic layer produces

unwanted CO2. The cell also requires the presence of water,

which limits energy density.

Solid oxide fuel cells (SOFC) are intended mainly for combined

heat and power (CHP) for domestic and industrial use. They

currently operate at high temperatures (up to 10001C) but

lower temperature (600 1C) versions are being developed,

which will allow use of metallic components with bettermechanical properties and thermal conductivity than the solid

oxide electrolyte. SOFC operate on a wide range of fuels but

require long start-up times (typically 8 h.). Newer [micro-

tubular] designs promise faster start-up. Cost reduction is

critical.

4.2. Key materials science advances

Durable membranes and improved catalysts are needed for

lower temperature cells. Solid oxide fuel cells (SOFC) require

ceramics with improved thermal and mechanical stability.

Durability depends on application. Portable battery pack fuelcells require 3-year lifetimes, whereas motor vehicles need

5–10 years. Power station fuel cells require lives up to 20 years.

Component sintering conditions, membrane failure, corrosion,

fuel contaminants, etc. all limit material durability.

By 2050, materials development will enable the fuel cell

market to use less expensive electrode materials [than

platinum/palladium] and highly efficient gas flow materials

[e.g. carbon nanotubes] and membranes. Material develop-

ment will provide more cost-effective and power-efficient

devices that operate over a wider range of operating tempera-

tures.

5. Hydrogen storage


‘‘The aim is to reduce CO2 emissions by 60% by 2050. This

target is best met by increased use of hydrogen fuel.’’ [EWP, Para

1.10/1.18]

5.2. Current status

Hydrogen storage is important for long-term exploitation of

fuel cells. In the short term, hydrogen will be extracted from

hydrocarbon fuels using steam reforming, combined with CO2

sequestration. Containment/transport of the gases is difficult

Liquefied hydrogen containers and high-pressure gas cylinders

will initially be used for hydrogen storage but solid-statehydrogen storage would be preferable. Materials options for all

types of containment are being developed.


Solid-state hydrogen storage is possible using metal hydrides

and carbon nanostructures (Fig. 6). Both options are being

investigated as part of the UK EPSRC SUPERGEN Initiative. Hydride

systems tend to be too bulky and heavy for efficient storage

[see lightweighting], while nanostructures have health and safety

issues

6. Renewables


‘‘Government recognises that specific measures are requiredy

to achieve the target of supplying 10% of UK electricity from

renewable energy by 2010’’ [EWP, Para 1.21].

ARTICLE IN PRESS

Fig. 6. Structure of carbon C564 ‘buckeyball’ and nanotube.




Any major shift in primary fuel sources will require consider-

able investment in hardware and extensive R&D [particularly

for alternative fuels].

A major challenge facing the materials community is the sheer

diversity of renewable energy sources and consequent material

implications. Because of this diversity, materials R&D tends to

be fragmented. Greater focus is needed.

7. Solar energy —photovoltaics (PVs)

The Sun generates nearly a trillion, trillion kW of power2 and

has done so at virtually the same rate for over 3 billon years.

In half an hour, enough of the Sun’s energy reaches the Earth’s

surface to meet the World’s energy demand for a year

[www.ecocentre.org.uk/solar-electricity].

To waste that energy seems careless!


Solar PV and wave/tidal power are areas in which increased

investment is likely to lead to step change breakthroughs.’’ [EWP

2003, Para 4.15]

7.2. Current material status

Solar cells with large-area single-crystal wafers (Fig. 7) are

efficient but expensive. Polycrystalline/ribbon silicon is cheaper to

produce but has reduced efficiency. Durable, low-cost/high-

efficiency PV materials and processes are being developed.


A range of functional materials are being developed. These

devices will always provide secondary power in the UK

because of unreliable weather, but the EWP is correct in its

assertion that solar PV offers considerable potential for step

change breakthroughs. Examples include:J dye-sensitised photochemical cells [e.g. nanocrystalline

titanium dioxide];J quantum dot solar cells [CdSe semiconductor absorbers in

polymer/C60 composite].

This ‘buckyball’ structure has potential for low-cost, large-

area fabrication.J Nanostructured oxide polymer composites.J Thin film inorganics—CdTe, GaAs, polycrystalline silicon.J Supercapacitors based on nanostructured materials.J Ultra-thin, anti-reflective and electrical conducting coatings.

By 2050 several of these materials should have achieved

production status.

8. Wind power (Fig. 8)

8.1. Key materials science advances

Polymer composite wind turbines are relatively lightweight

and corrosion-resistant making them ideal in hostile and

inaccessible locations. Sensors incorporated into the structures

during manufacture could enable service loads and damage

accumulation to be monitored. The aim is to ‘fit and forget’

such devices.

Energy storage and transmission remain critical issues.

By 2050 composite structures could exhibit the following

characteristics:

J Appreciably higher strength. Carbon nanotubes added topolymer composites can increase stiffness and strength

ARTICLE IN PRESS

Fig. 7. Assembly of solar-powered photovoltaic cells.

2 41023 kW, http://ircamera.as.arizona.edu/.


http://www.ecocentre.org.uk/solar-electricity

http://ircamera.as.arizona.edu/

http://ircamera.as.arizona.edu/

http://www.ecocentre.org.uk/solar-electricity



tenfold but contamination and health and safety issues

remain. Cost-effective production routes are also needed.J Composite structures designed to respond to aerodynamic

forces [aeroelastic tailoring] and changing shape [morphing]

to optimise performance.

Materials developments that address energy storage and

transmission issues include:

J Superconducting cablesJ Supercapacitors based on nanostructured materials for

short-term storageJ Batteries with near-instantaneous charging and high-

capacity discharge [e.g. Toshiba lithium capacitors reported

in 2005]J Insulation and phase change materials for heat stores.

9. Water power (Fig. 9)


‘‘Solar PV & wave/tidal power are areas in which increasedinvestment is likely to lead to step change breakthroughs’’. [EWP,

Para 4.15]

9.2. Current materials status

Materials exist for water turbines and wave power. Because of

salt-corrosion and heavy seas, designers tend to over-engineer

wave devices with resulting performance penalties. Corrosion,

erosion and cavitation remain material issues.


Existing materials need optimising for wave technology, with

more robust design criteria and improved life prediction

methods. Composite materials offer higher corrosion resis-

tance and condition monitoring [as for wind power]. Materials

knowledge for water turbines may be transferable from marine

technology.

Most relevant materials technology is already available.

10. Nuclear fusion and advanced nuclear fission

10.1. Energy White Paper 2003: [EWP, Para 1.24 and 1.38]

‘‘Nuclear power is an important source of carbon-free

electricity. Current economics make it unattractive [and] there

are important issues of nuclear waste’’.

‘‘Strong backing is given for international development of

fusion power’’.

10.2. Nuclear fission

10.2.1. Key material science advances

Power generation structures use bcc steels with ‘low-activity’

alloying additions. Previous typical materials issues have been

environmentally induced cracking, thermal fatigue and ageing;

loss of toughness caused by irradiation, wear, etc. Condition

monitoring for such degradation mechanisms would be

valuable.

ARTICLE IN PRESS

Fig. 8. Composite wind turbines.

Fig. 9. Wave power machines [top L: Pelamis; bottom L: LIMPET].




Alternative encapsulants to borosilicate glass are being

investigated for plutonium waste. Because of extended life-

times, materials R&D and waste management rely heavily on

computer modelling. Charged particle beams are used to

approximate neutron irradiation for model validation pur-

poses. Risk-management and non-destructive evaluation

(NDE) are also considered at the design stage.

Generation IV reactor designs are being evaluated and may

enter service beyond 2030. Specialist steels will be needed for

exotic Generation IV coolants [e.g. liquid sodium, lead].

10.3. Nuclear fusion

Nuclear fusion is a long-term candidate for future power

generation beyond 2050. Fusion is achievable only at very high

temperatures [e.g. the Sun is a fusion reactor].

10.3.1. Key material science advances

The hot gases of the fusion reaction are confined within a

strong electrostatic or magnetic field. Materials science is

released from the task of developing a containment material

but the issue of a plasma-facing material remains ( Fig. 10).

Graphite erodes rapidly. If tungsten is chosen, impurities can

impair the plasma. Beryllium is currently the favoured

containment material but health and safety issues remain.

Compared with hot plasma containment, the material devel-

opments for hot gas transfer and turbine power components

seem relatively straightforward! Large flux levels of high-

energy neutrons [100 times more than in pressurised water

reactors (PWR)] make structures radioactive. Low activation

alloys [e.g. vanadium] with half-lives of tens, rather than

thousands of years [as for fissile materials] make this problem

less serious. Complex new alloy compositions are, however,

still needed.

There are some strong synergies between fusion and Generation

IV fission materials. Both will use similar candidate materials

[bcc and oxide-dispersion-strengthened steels] and operate

under conditions that require high temperature, long life alloys

capable of withstanding neutron bombardment. Both use similar

theoretical modelling and neutron source experimental valida-

tion, for optimised alloy design and share similar damage-driven

mechanisms [i.e. creation of defects and transmutant gases]. A

materials testing facility is planned to evaluate fusion materials.

This is currently at the design stage.

ARTICLE IN PRESS

Fig. 10. Split image of JET tokamak fusion reactor [hot plasma on right].


1. driver,making a material difference in energy

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