(Repeats Feb. 11 item; no changes to text)
By John Kemp
LONDON Feb 11 Finding a better way to store
electrical energy is the single biggest breakthrough needed to
tackle climate change. But the goal of developing batteries that
are lighter, as well as more compact, powerful and affordable
remains frustratingly elusive.
Virtually all usable energy on Earth originates from the
sun: wind, solar, wood, even fossil fuels. Oil, gas and coal are
simply the fossilised remains of organisms that lived in ancient
forests, lakes and seas, which relied on photosynthesis to
harness the sun's energy.
The amount of solar energy reaching Earth's surface every
year is many orders of magnitude greater than that needed to
meet all the needs of the planet's growing population.
Solar radiation reaching the planet's surface is equivalent
to more than 150 watts per square metre on average, according to
Roger Barry at the University of Colorado ("Atmosphere, weather
and climate", 2010).
The problem is how to store that energy in a usable form
available when and where needed. Solar panels are not useful at
night, or in the winter at high latitudes, or when the sun is
temporarily obscured by clouds. Solar energy ultimately drives
the wind too. But wind turbines are useless on a still day.
The ideal storage medium has a high energy content but is
light, compact and affordable. Liquid fuels refined from
petroleum, especially gasoline and diesel, have the best
combination of energy content, density and weight, which makes
them especially desirable in mobile applications like cars,
trucks and ships.
"Compared to gasoline and diesel, other options may have
more energy per unit weight, but none have more energy per unit
volume," the U.S. Energy Information Administration explained in
a recent note ("Few transportation fuels surpass the energy
densities of gasoline and diesel", Jan. 3, 2014).
Liquefied natural gas contains more energy per unit of
weight but takes up much more space. Ethanol is inferior in
weight and volume terms. Batteries are generally heavier and
need more space than gasoline or diesel. Most are also much more
Burning those fossil fuels, however, contributes to global
warming. The challenge is to develop more effective energy
storage that can compete with gasoline and diesel. Better
batteries are likely to prove the only realistic option.
GRID SCALE, VEHICLES
Improved storage is needed at two very different levels:
grid scale (for example to store solar electricity for use at
night) where it can be stationary, and on a smaller, more mobile
scale (to replace gasoline and diesel with electricity as the
source of power in cars, trucks and ships).
Various options have been developed for stationary
grid-scale storage - including pump hydro, flywheels and
compressed air systems. Better batteries are the most promising
technology for grid-scale applications, however, and probably
the only one for small-scale mobile applications.
Small-scale batteries are already used in electric vehicles
and plug-in hybrid electric vehicles. The main problem is the
high cost and weight.
For grid applications, some truly enormous batteries have
been built. The city of Fairbanks in Alaska has installed a
battery system weighing 1,300 tonnes and taking up 2,000 square
metres (21,000 square feet) in a warehouse capable of providing
40 megawatts of power for up to seven minutes in the event of a
power failure (Daily Telegraph, "World's biggest battery
switched on in Alaska" 2003).
Given Fairbanks' isolated location and winter temperatures
as much as 50 degrees Celsius below zero (minus 58 Fahrenheit),
a secure supply of electricity is vital. The battery is intended
to keep the lights on long enough to start up auxiliary diesel
Even bigger batteries have been built. In 2011, China's
State Grid Corporation commissioned a giant battery array that
can supply 20-36 megawatt-hours of electricity. The Zhangbei
National Energy Storage and Transmission Demonstration Project,
in Hebei province, is coupled with a wind farm and solar power
plant, and claims to be the largest battery array in the world.
Crucially, Zhangbei was intended to prove that wind and
solar can provide a reliable source of power on demand. But in
most cases, batteries are still too heavy, too large and too
expensive to offer an effective solution to grid-scale and
vehicle storage needs.
Developing smaller, lighter and more powerful batteries is
now one of the top research priorities for the U.S. Department
of Energy, the world's biggest funder of science research.
Most of the department's research focuses on more mature
Its Advanced Research Projects Agency-Energy (ARPA-E),
however, is a specialised unit that aims to catalyse the
development of less advanced technologies with transformational
potential by providing early-stage funding, technical assistance
and commercial expertise.
Established in 2007, ARPA-E was modelled on the Pentagon's
Defense Advanced Research Projects Agency, credited with helping
develop the global positioning system, the stealth fighter and
According to the U.S. National Academy of Science, ARPA-E
was designed to support "creative out-of-the-box
transformational generic energy research that industry by itself
cannot or will not support and in which the risk may be high but
success would provide dramatic benefits to the nation".
The agency has an annual budget of $275 million. Most of the
funding is allocated to 18 focus areas. Five of them concern
energy storage - more than any other area of energy technology.
The storage-related programmes are: Advanced Management and
Protection Energy Storage Devices (AMPED); Batteries for
Electrical Energy Storage in Transportation (BEEST); Grid-Scale
Rampable Intermittent Dispatchable Storage (GRIDS); High-Energy
Advanced Thermal Storage (HEATS); and Robust Affordable Next
Generation Energy Storage Systems (RANGE).
With the exception of HEATS, which focuses on nuclear and
solar thermal energy, all these programmes concentrate on
developing better batteries. Since 2010, ARPA-E has allocated
well over $100 million of funding to 47 battery-related
projects, according to the agency's website.
BEEST is funding research that explicitly aims to make
batteries comparable to gasoline and diesel. "To offer
performance comparable to gasoline-powered cars, electric
vehicles must be able to deliver the kind of power that will
make electric cars fast, responsive and exciting to drive,"
"They also must be able to travel at least 300 miles (480
km) on a single charge - the approximate driving range per tank
of gas - for a comparable cost. This would require batteries
with double the energy density and one-third the cost of today's
state-of-the-art lithium-ion battery packs."
ARPA-E is funding research to re-evaluate each component of
a battery (positive and negative electrodes as well as the
electrolyte) and the materials used to make them.
"BEEST projects are exploring a variety of potential
solutions including radical improvement of today's lithium-ion
technologies, designs using other metals such as magnesium,
sodium and zinc, and new ways of using lithium in lithium-sulfur
and lithium-air batteries," the agency explains.
At a much bigger scale, GRIDS is funding research into
technology that could be used to back up intermittent wind and
solar generation with storage anywhere on the electrical grid at
a capital cost of less than $100 per kilowatt-hour.
According to the agency: "The energy storage facilities that
exist today use pumped hydropower, which is only available in a
handful of locations. New, more flexible, large-scale energy
storage technologies would allow energy to be efficiently stored
and sent to any location in the country.
"Cost-effective grid-scale energy storage is critical for
increasing the use of renewable alternatives and reducing
greenhouse gas emissions from the electric energy sector."
A major breakthrough at either scale still appears some way
off. But nothing would do more to combat climate change, which
justifies ARPA-E's commitment to research on a new generation of
(Editing by Dale Hudson)