Memorandum 36
Submission from Royal Society of Chemistry
The current state of UK Research and Development
in, and the deployment of, renewable energy-generation technologies
including: offshore wind; photovoltaics; hydrogen and fuel cell
technologies; wave; tidal; bioenergy; ground source heat pumps:
and intelligent grid management and energy storage
Photovoltaics (solar power)
Solar power has the potential to provide a significant
proportion of the UK electricity needs. The chemical sciences
will be crucial in reducing the cost and increasing the efficiency
of solar technology through improvements to current design and
manufacture and through the development of the next generation
of technology, such as technology that takes advantage of biological
methods of harvesting and storing energy from light. The UK has
a strong research base in areas including understanding and mimicking
photosynthesis systems and also in dye-sensitised and organic
solar cells. Ideally it will become routine to integrate solar
power into buildings through the use of specialised construction
materials (for example roof tiles and windows) coupled to energy
storage and low energy demand devices.
Photovoltaic (PV) devices consist of a semi-conducting
material, currently most commonly silicon, which convert photons
into electrical current by means of the photoelectric effect.
They were developed in the 1950s to power space satellites, but
their potential for providing remote power for telecommunications,
water pumping and refrigeration rapidly increased demand for terrestrial
applications. The drawbacks of early photovoltaic technology also
became obvious, namely cost, low power density and intermittency
of operation.
Although prices are coming down PV systems currently
cost around 55 pence/kWh which is more than a factor of 10 greater
than current gas, coal and nuclear power plants. A number of different
technologies are at various stages of development to both reduce
the cost of solar modules and to increase their efficiency. Over
80% of modules are currently based on crystalline silicon. Silicon
is an excellent material for solar cell production since its technology
has become highly developed as a result of the global semiconductor
market. In addition, its supply is virtually inexhaustible and
it is non-toxic, although its manufacture is currently highly
coupled to semiconductor demand. In the late 1970s and early 1980s
thin films of inorganic semiconductors made from indium tin oxide
(ITO), cadmium selenide (CdSe), copper indium diselenide (CuInSe2),
amorphous silicon, thin film silicon and titanium oxide (TiO2)
were developed as potentially cheaper PV materials. Innovative
research on very thin (less than 20 atomic layers), high efficiency
silicon devices is now in progress.
One of the factors that keeps system costs high
for these technologies is the requirement of high temperature
processing of the semiconductor material. This, and the rapid
growth of the organic light emitting diode market, have resulted
in considerable research on PV materials based on molecular, polymeric
and nanocomposite materials. Although commercially viable efficiencies
have yet to be demonstrated, progress is rapid. In 2004 at least
two manufacturers claimed efficiencies of 5% for organic PV materials
that can be printed or sprayed on to a thin support, flexible
backing film, potentially offering considerable production cost
reductions.
Dye sensitised solar cells (DSCs) offer a near
market alterative system to silicon cells. These cells were invented
by Michael Grätzel and Brian O'Regan at the École
Polytechnique Fédérale de Lausanne in the 1990s.
DSCs currently have a sunlight conversion efficiency of 11%, which
is lower than that of silicon based solar cells, however, they
have a lower cost base which allows them to compete. There is
significant potential to improve the efficiency and further reduce
the cost of DSCs.
The growing number of uses for photovoltaic
devices, and the considerable improvements in reliability and
price have generated a market that is growing at about 25% per
annum. Although PV began by providing power to remote locations
that had no grid connection, over 50% of today's world market
is for building integrated photovoltaic (BIPV) devices that are
incorporated into the roofs and structures of buildings. Providing
governments continue to support the installation of BIPV and introduce
policies that allow net metering, by which consumers can sell
surplus electricity back to the grid, it is likely that the demand
for PV will continue to grow. As a result, many independent studies
suggest that the costs of PV will continue to fall and that it
is plausible to reduce module costs by a factor of seven or greater
by 2020—this would allow BIPV to provide electricity below
today's retail price in sunny areas of the world.
Useful amounts of electricity can also be generated
directly from infrared radiation using a process called thermophotovoltaics.
It is unlikely that the power of the sun will be harnessed directly
using this technology, but it is theoretically possible. It is
more likely that thermophotovoltaics will be used to generate
electricity from waste heat to boost the efficiency of conventional
thermal power generation technologies.
Hydrogen and fuel cell technologies
The hydrogen economy is the name given to an
economy based on hydrogen rather than carbon based fuels. The
transition to the hydrogen economy represents the biggest infrastructure
project of the 21st Century. A sustainable hydrogen economy would
offer enormous economic, social and environmental benefits and
this justifies the significant investment of resources and capital.
When hydrogen (H2) is burned or used as fuel
to generate electricity in a fuel cell, the major by-product is
water. Whilst hydrogen is abundant on Earth, it is not abundant
in the form H2 and must be produced in a way that uses energy.
Therefore, H2 is potentially a significant fuel source and the
key challenges are to minimise the energy used in producing H2
and ultimately to produce H2 from sustainable sources.
There are technical barriers throughout the
supply chain of the hydrogen economy, and the key challenges for
the chemical sciences are highlighted in the following sections.
Hydrogen production
Energy is required to produce hydrogen and therefore
as a fuel it is only as clean as the process that produced it
in the first place. Currently the most common method is steam
reforming of natural gas in two-step catalytic process, producing
a mixture of H2 and CO2. There are concerns over the economics
of the process and over the release of CO2. In the future it will
be possible to employ carbon capture and storage (CCS) technology
to safely store the CO2, however, this will add to the cost of
the hydrogen production and the energy required. There are a number
of medium and long-term options for producing hydrogen:
— Coal and oil residues or biomass
gasification. The high temperature of the process and the need
to separate nitrogen from air (presumably cryogenically) are barriers
which add to the cost of this process.
— Using electricity (preferably
from renewables) to split water via electrolysis can be seen a
method of storing (renewable) power. Further work is still needed
to develop improved electrode surfaces for electrolysers and also
the materials of construction. Uses for the by-product O2 also
need to found.
— Thermochemical splitting of
water in the next generation of high temperature nuclear reactors
or concentrating solar power plants. There is a need for new materials
and an understanding of the fundamental high temperature kinetics
and thermodynamics in order to achieve this.
— Biochemical hydrogen generation.
Green algae and cyanobacteria utilise light to split water, producing
both H2 and O2. Currently O2 concentration in the system and the
rate of reaction are limiting factors. New natural microorganisms
and genetically modified organisms may hold to key to increased
efficiency.
— Photocatalytic water electrolysis
is where the energy of sunlight is used to split water into H2
and O2. The system, and current R&D priorities, are focussed
on two basic principles. Firstly, the light harvesting system
must have suitable energetics to drive the electrolysis. Secondly
the system must be stable in an aqueous environment.
Hydrogen storage and distribution
Hydrogen is the lightest element and occupies
a larger volume than other fuels. Currently, in prototype vehicles,
compressed hydrogen is used, but this is relatively bulky. Liquid
hydrogen would be a more efficient way to store H2 (850 times
denser than gaseous H2) but with a boiling point of -253°C
it is very energy intensive to maintain the very low temperature
required to store hydrogen in this form. Finding mechanisms to
store hydrogen in a form that is safe, suitable for intended use
and regenerable (if applicable) is therefore a key research priority
that the chemical sciences must rise to meet. Some of the key
technologies and issues are summarised below:
— High surface area nanostructured
materials, such as carbon nanotubes, have been shown to be able
to store and release significant quantities of H2. Such materials
are as yet unproven and much scientific endeavour is required
to fully assess their potential.
— Certain metal complexes absorb
H2 reversibly to form metal hydrides. Numerous compounds have
been and continue to be studied. Key requirements of a suitable
metal hydride include, high H2 content, low cost, favourable kinetics,
resistance to poisoning and the materials should not ignite in
air.
— There are a number of options
for chemical carriers of H2; this means that the H2 is bound into
the chemical structure of the carrier. Organic liquids, such as
cyclohexane and methanol, inorganic complex hydrides such as 3Na[AlH6]
and chemical hydrides such as NaBH4 all have potential to carry
H2. Key challenges include the mechanism of releasing H2, recharging
the materials, H2 density and cost. R&D programmes continue
to explore these issues.
There are a number of worldwide examples of
pipeline networks for safely moving pressurised hydrogen, thus
demonstrating that a larger scale network is possible. However,
there is an issue of compatibility of H2 with existing natural
gas infrastructures both in terms of the materials employed (potential
for leakage) and the need for a faster flow rate (requiring more
energy). The chemical sciences have a key role to play in material
design for hydrogen carrying infrastructures.
Hydrogen may potentially be stored in large
quantities in depleted oil and gas fields and aquifers. There
is a significant parallel here with work being carried in the
field of carbon capture and storage.
There have been concerns over release of molecular
hydrogen into the lower atmosphere, for example through leakage.
The presence of H2 may lead to a reduction in the levels of hydroxy
radicals ( OH), and as OH is a sink of methane (CH4) it may lead
to an increased level of CH4 in the atmosphere. Clearly it is
important that the role of H2 in the atmosphere is better understood.
Hydrogen use
Aside from direct combustion, fuels cells are
the main method for obtaining energy from hydrogen. Fuel cells
(FCs) fall broadly into three categories:
(i) Low Temperature (50-150°C): alkaline
(AFC), proton-exchange membrane (PEMFC) and direct methanol (DMFC)
fuel cells;
(ii) Medium Temperature (around 200°C):
phosphoric acid fuels cell (PAFC);
(iii) High temperature (600-1,000°C):
molten carbonate (MCFC) and solid oxide (SOFC) fuel cells.
The DMFC differs from the other FCs because
it uses methanol as fuel, rather than H2. Each of the six systems
has preferred uses (for example stationary and mobile power generation),
advantages and disadvantages and specific research priorities
that need to be addressed. For chemical scientists there are numerous
technical challenges to be overcome including:
— materials for construction;
— understanding the fundamental
thermodynamics and kinetics;
— tolerance to impurities;
— electrocatalyst design;
On-board storage of hydrogen is posing significant
obstacles to delivering hydrogen-powered vehicles. The development
of materials for hydrogen storage is a key challenge for chemical
scientists.
The cost of fuel cells versus that of the internal
combustion engine is also a problem, with the latter typically
costing $50 for each kilowatt of power it produces while fuel
cells cost a hundred times more. Technical challenges such as
making fuel cells rugged enough to withstand the stress of driving,
reducing their size and weight while increasing power density,
fuel flexibility and fuel cell poisoning still exist.
The RSC believes that for the hydrogen economy
to become a reality, major scientific and engineering challenges
need to be addressed in terms of the generation of hydrogen on
a large scale, storage, cost-effective safe transportation and
the next generation of materials and technology for hydrogen fuel
cells. We recommend that the Government supports the science and
engineering research that will ultimately deliver a sustainable
hydrogen economy at a level where the UK is in competitive position
in a world perspective.
Bioenergy
The RSC has recently submitted evidence to two
relevant inquiries, the EFRA Committee inquiry into bioenergy
(appendix A) and the Royal Society inquiry into biofuels (Appendix
B). Both documents are attached to this submission as appendices.
Energy Storage—Batteries
Rechargeable batteries offer the most direct
means of storing electrical energy and as a result are highly
efficient.
Lithium-ion batteries represent the most important
development in rechargeable battery technology for a hundred years.
They have three times the energy density of conventional rechargeable
batteries and have had a major impact in consumer electronics.
A lithium-ion battery occupying some 10m3 could store 4.5 MWh
of energy and with a charge/discharge efficiency of over 99.9%.
This technology is already the storage solution of choice in a
number of energy research centres around the world.
Lithium-ion technology presents one of the greatest
challenges for chemists. Scale up to larger batteries requires:
— fundamental advances in new
cheaper, safer electrode and solid polymer electrolyte materials
with better performance; and
— new non-flammable liquid electrolytes
or ionic liquids.
Moreover, Li-ion batteries for vehicles are
comprised of hundreds of cells, if any of these fails the whole
system is compromised.
Cobalt oxide is a key material for producing
lithium ion batteries. The world estimated cobalt reserves are
relatively small; less than a tenth of that of nickel and just
over a hundredth of that of copper. Cobalt accounts for a quarter
of the mass of lithium ion batteries. If 30 million battery packs
capable of powering electric vehicles were made annually the world
cobalt reserves would be depleted in six years (provided the global
estimates are accurate). The majority of cobalt reserves are located
in politically unstable regions—the top three sources of
cobalt are Congo, Cuba and Zambia. This could raise a major security
of supply issue. To address this electrodes based on cheaper more
abundant materials must be synthesised.
A further possible driver for the development
of novel battery technology at the smaller scale end of battery
technology is regulation. In the EU, measures have already been
taken to limit the mercury content of batteries. Further regulation
will aim to reduce other heavy metals, including cadmium, nickel
and lead. Also options for disposal of batteries will be limited
to encourage collection and recycling.
Energy Storage—Superconductors
In superconducting magnetic energy storage devices
(SMES), energy is stored in the magnetic field of a coil within
which a current flows. The device consists of a superconducting
coil, typically made of niobium with titanium or tin, in a copper
matrix, a power conditioning system (PCS), a refrigeration system
for cooling the coil and a cryostat vacuum vessel. Efficiency
losses are mainly due to the cryogenic system, which has to keep
the coil below the critical superconducting temperature of around
-268°C.
Chemists are needed to address the identification
and development of new superconducting materials with higher critical
temperatures, preferably room temperature, and with suitable mechanical
properties for processing into coils and wires.
Wind, tidal and wave power
Advances in materials science to develop high
strength, lightweight materials for turbine blades and towers
are required in order to facilitate the construction and continued
operation of large wind and tidal power turbines. Long lasting
protective coatings will also be required to reduce maintenance
costs and prolong the operating life of wave and tidal energy
devices.
The feasibility, costs, timescales and progress
in commercialising renewable technologies as well as their reliability
and associated carbon footprints
No comment.
The UK Government's role in funding research and
development for renewable energy-generation technologies and providing
incentives for technology transfer and industrial research and
development
It is important that there are sufficient trained
and committed scientists and engineers to do carry out the research,
development, demonstration and deployment of renewable energy-generating
technologies. It is also important that the Research Councils
and DTI ensure that there are collaborative funding mechanisms
throughout the technology development pathway that allow scientists,
engineers and technologists to work together to bring basic research
through to developed products. The RSC is hopeful that the new
Energy Research Institute should address this issue and be a true
multi-disciplinary centre to address the technology challenges.
The RSC has recently submitted responses, relevant
to this inquiry, to the Sainsbury review of science and technology
consultation (Appendix C) and the EPSRC knowledge transfer and
economic impact consultation (Appendix D)—these are attached
as appendices.
Other possible technologies for renewable energy-generation
Artificial photosynthesis
Artificial photosynthesis is a research field
that attempts to replicate the natural process of photosynthesis,
converting sunlight, water and carbon dioxide into carbohydrates
and oxygen. The process essentially comprises two steps one involving
a light reaction and other a dark reaction. In the first step
light is captured and the energy used to split water into oxygen
and hydrogen. In the second "dark" step hydrogen is
combined with carbon dioxide to make carbohydrates (or possibly
other products). The potential of artificial photosynthesis is
huge as it offers a route to sustainable hydrogen production and
also potentially to a process that removes carbon dioxide from
the atmosphere and creates useful products. The scientific and
technical challenges, however, are equally large—in essence
this is because the natural process is incredibly complex and
comprises of numerous interlinked processes. Artificial photosynthesis
will require a number of years of research and development before
a commercial process is envisaged.
At a recent RSC policy seminar (Harnessing Light)
Professor Tony Harriman and Professor Jim Barber gave presentations
on this subject. In addition to the scientific challenges it was
noted that there is worrying trend in expertise loss—partly
through retirement and partly through losing researchers to the
competitive field of molecular photonics.
Blue energy
A significant potential to obtain clean energy
exists from mixing water streams with different salt concentrations.
This salinity-gradient energy, also called blue energy, is available
worldwide at estuaries where fresh water streams flow into the
sea. The global energy output from estuaries is estimated at 2.6TW,
which represents approximately 20% of the present worldwide energy
demand. Large amounts of blue energy can also be made available
from natural or industrial salt brines.
Blue energy can work either on the principle
of osmosis (the movement of water from a low salt concentration
to a high salt concentration) or electrodialysis (the movement
of salt from a highly concentrated solution to a low concentrated
solution) where the saline water and fresh water be separated
by a selectively permeable membrane. In the osmosis process water
pressure is created that can drive a turbine. In the electrodialysis
case the movement of ions creates the electricity. The by-product
of blue energy is brackish water. Brackish water is simply a combination
of fresh and salt water which naturally occurs in an estuary.
Though the technology of blue energy has been
understood for quite sometime, manufacturing the membranes was
far too expensive for this to become a practical energy alternative.
Recently, more economical membranes have been developed which
will allow blue energy technology to begin being implemented in
suitable environments. Further developments that reduced the cost
or improved the efficiency of membranes would significantly improve
the economics of this process. Currently blue energy is being
used successfully in the Netherlands.
July 2007
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