Recharge of the
light brigade
…plugging the energy gap with a
world first in electricity storage which could revolutionize the industry…
Identification of the Technology
Explanation and Profile of
Technology
Potential and Future Expectations
Identification of the Technology
Batteries are
an integral part of everyday life. They provide clean, dependable electrical
power for a multitude of devices, from cameras to pacemakers to computers to
cars.
Now, fuel cells are under construction that are large enough to power an entire town!
Financial Benefits:
More efficient use of existing power plants in generation,
transmission, and distribution
Technical Benefits:
Improved power system performance.
These fuel cell plants are based on an electro-chemical
process, operating like a giant rechargeable battery storing enough electricity
to power 10,000 homes for 24 hours… 15-megawatts / 120
megawatt-hours of on-line storage. The plants store electricity when demand is low and release it
when demand is high, eliminating “brown-outs” and limiting the need for new
power plant construction in order to satisfy peak power demands. The plants
also give a back-up supply should the main power plant go off line, and provide
main power plant with the power needed for re-starting after a grid failure.
The response time for power supply to the grid during a power outage is nearly
instantaneous, fast enough to keep computers and flight simulators at a nearby
Air Force Training Center operating without a glitch.
Two commercial scale demonstration plants are currently under construction and will be operational before the end of 2002.
Energy is unique among commodity products because it is difficult to store, either by the producer or the consumer.
Because instantaneous demand for electricity has to be
balanced by production capacity, electricity systems are built with sufficient
generating capacity to meet the maximum predicted demand plus a margin to
ensure security of supply. The demand
for electricity has considerable daily and seasonal variations, however, and
the maximum demand may only last for a few hours each year. Consequently some power stations are only
required to operate for very short periods each year. This is an inefficient use of an expensive power plant.
The average demand for electricity in a typical system is
about 60% of the maximum demand. To
ensure security of supply, a margin of capacity above the maximum demand is
also provided. In many locations, power
stations run near capacity for less than 50% of the year. This under-utilization is reflected in
higher prices for electricity paid by the consumer. When large-scale electrical
storage is available, only sufficient generating capacity to meet the average
demand for electricity is required instead of the peak demand. In theory, a
typical system could be operated with approximately 40% less generating
capacity than would otherwise be needed. The remaining generators would run
more efficiently with increased load factors and less cycling. The net effects are significant reductions
in capital investment and operating expenses.
Advantages and Challenges
Advantage: Utility Scale Energy Storage
The plant can be used for
arbitrage by “time shifting” energy, increasing utilization of base load plants
and reducing the need for a peaking plant.
Advantage: Emergency Power Capabilities
The plant has been designed for “Black Start”
capability. With Black Start, the plant
will supply the auxiliary load required to restart the fuel cell station and
its adjoining power station in the event of network interruption. It is in
effect an “embedded generator” in the power grid.
Advantage: Stabilizing Network Capabilities
The plant can be used to
stabilize transmission and distribution systems, cutting overload on lines and
reducing stress on substation equipment. Storage within the network aids
control of frequency and voltage providing a more stable and reliable power
system.
Advantage: Minimal Environmental Impact
The technology is
environmentally benign. The plant can store energy from renewable sources such
as solar and wind facilities, increasing flexibility and maximizing the value
of the renewable generation features.
The plant is nearly waste-free, with internal recycle of chemicals
approaching 100%. Waste products are
inert salts that may be sold for commercial use.
Advantage: Fast Response Time
The plant can provide instantly available standby support,
delivering a reliable power supply. It supplies real and reactive power and is
therefore suited to many different applications in a power system.
Advantage: Low Labor Requirements
While current operations
are sparingly manned, advances in monitoring technology may allow unmanned
operation in the near future.
Challenge: Delivery
Times
Full project time-scale from start of engineering to
completion of commissioning is currently approximately 18 months. Future energy
storage plants are expected to have shorter delivery times due to the current
modular, scalable design.
Challenge:
Energy Cost for Supply to Grid
Current costs are comparable but slightly higher than
competing technologies. For a first-of-a-kind plant, this is a significant
achievement. Future plants with similar
designs will have considerably reduced specific costs.
Explanation and Profile
of Technology
Science fiction becomes science fact through the operation of large-scale regenerative fuel cell plants….
The Regenesysâ
plant consists of:
·
two large storage tanks holding electrolytes that store
electrical energy
·
a bank of regenerative fuel cells that charge and discharge
the electrolytes
·
a power conversion system to supply stored power to the
commercial grid
The two electrolytes are
pumped through regenerative fuel cells in individual circuits separated by an
ion exchange membrane. When storing
energy, the electrolytes convert to a charged state that can be discharged to
release energy. The conversion of electrical to stored chemical energy can
be repeated indefinitely, and with high efficiency.
The plant bears more resemblance to a small chemical
processing plant than to a traditional power station, since it’s technology
consists of special pipes and pumps rather than large rotating electrical
machinery. A delicate and precise
balance is maintained between gravity, friction, and electromotive forces to
optimize power generation from each cell. The only waste products are hydrogen
gas and an inert inorganic salt. There is no
wastewater. There are no air emissions.
The Regenesysâ system
uses electrolytes of concentrated solutions of sodium bromide and sodium
polysulfide. The electrolytes circulate in two separate electrolyte circuits. The
regenerative fuel cell plant stores or releases electrical energy by means of a
reversible electrochemical reaction between the electrolytes. The
regenerative fuel cells have inert electrodes that act only as an electron
transfer surface. The electrodes do not
take part in the electrochemical process and so do not limit the energy storage
capacity of the fuel cell. This approach allows the complete separation of power
(determined by the module’s electrode area) and energy (determined by the
storage tank volume).
The heart of the Regenesysâ
plant is
the Power Conversion System (PCS) designed by ABB. The PCS provides the interface between the power
grid’s AC network electrical supply the variable operating voltage of the Regenesysâ DC modules. This
control system is an “intelligent” four quadrant converter designed to transfer
both reactive and real power simultaneously and independently from each
other. This unique control system
allows flexibility to provide slow draw or peak outputs from the battery’s
electrical storage reservoir in response to demand from the grid. The plant normally
runs unmanned, with controls monitored via fiber optic connections to a master
control facility several miles away.
Low labor costs add to the economies of the operation.
Recent Applications
A pilot
plant is currently in operation at the development facility
in the UK.
One commercial-scale plant is
currently in the process of starting up in Little Barford, UK. Operation at full capacity should be
completed prior to the end of 2001.
This plant was built alongside the 680MW Combined Cycle Gas Turbine
power station in the city. It will
provide emergency power in the event of (frequent!) blackouts of the city’s
power supplies, and also provide peak power leveling capabilities. The Little Barford system will Black Start
itself and the standard power station in the event of a blackout.
One commercial-scale plant
is currently under construction in Columbus,Tennessee, US. Operation at
full capacity should be completed prior to the end of 2002. The Columbus Tennessee system will provide
UPS power for the Air Force flight simulators, preventing costly shutdowns and
lengthy rebooting of control systems in the event of (frequent!) power
disruptions in the TVA power grid.
Potential and Future Expectations
Larger Power Storage Capabilities
Design of a larger power plant is underway that will deliver
over 60-megawatts of on-line storage as well as provide emergency backup power
supplies to one of the southeast’s largest chemical plants.
Environmental “Green” Applications
By coupling non-polluting renewable energy sources (such as
solar and wind energy) with a large scale electrochemical battery for storage
of off-peak power generated, dependable and environmentally sound “green” power
generation can be achieved.
Marine Applications
Bulk energy storage can be adapted for marine operations,
allowing the naturally occurring energy fields found at sea to be harnessed for
assisting the operation of ocean-going vessels and offshore oil platforms.
Proton Exchange Membrane Fuel Cells
A second generation of electrochemical fuel cells are under
development using Proton Exchange Membrane technology. These cells are more efficient and cost
effective than cells currently used in the plants.
Currently, only one company is licensed with
the technology:
Innogy plc is an integrated energy company,
focused on energy generation, trading and retail.
The energy storage business is managed by Innogy
Technology Ventures Limited, a subsidiary company of Innogy plc.
Contact information:
Marketing Manager
Innogy Technology Ventures Limited
Harwell International Business Centre
Harwell
Didcot
OXON, OX11 0QA
+44 (0) 1235 444 999
e-mail: regenesys@innogy.com