New Vanadium Batteries -- A Breakthrough Solution for Electricity Storage
R.H.B. Exell, P.M. Spaziante and
P. Kanchanadul
1. The Joint Graduate School of Energy And Environment, King Mongkut's University of Technology, Thonburi,
Bangkok 10140, Thailand.
2. Cellennium Company Limited, Bangkok, 10400, Thailand.
Abstract
A vanadium battery consists of vanadium salt electrolytes flowing through
electrochemical cells. The storage capacity (kilowatthours) is determined by the quantity of
electrolytes used. The power rating (kilowatts) is determined by the active area of the
electrochemical cells. These two parameters can be sized independently over wide ranges (watts
to megawatts). Vanadium batteries are more durable than leadacid batteries because they have
no liquidsolid phase changes to cause the electrodes to deteriorate. The durability and wide
design options of vanadium batteries promise large markets for many applications, such as load
leveling, storage in renewable energy systems (e.g. wind and solar), uninterruptable power
supplies and for mobile power supplies (e.g. land vehicles and boats).
The Cellennium Company Limited has recently launched a program to commercialize
new designs of regenerative fuel cells using vanadium salts as electrolytes. The technology has
been licensed from Squirrel Holdings Limited, which owns the rights to the patents. The new
vanadium batteries are working successfully in the laboratory, and are giving excellent results.
Among the technology's key advantages are:
- A negligible amount of energy is used to pump the electrolytes.
- Shunt or bypass current losses are practically nil..
- More than 100 cells per stack are possible in a compact design which allows easy
assembly and easy transportation.
- The battery is easily scalable to megawatt size.
Introduction
Electricity is useful only if it is available when needed in a usable form. Without the
capability to timeshift and level the supply of energy via efficient and affordable storage, prime
movers that generate electricity from fossil fuels along with transmission and distribution
infrastructure will continue to operate wastefully. All of the most promising renewable energy
sources, such as solar radiation and wind, occur intermittently and can never be harnessed to their
full potential unless proper energy storage systems are developed.
The currently preferred energy storage solution, notably the leadacid battery, has not
really changed since its first invention over one hundred years ago. There have been
improvements in efficiency of the leadacid batteries and commendable developments in some
advanced batteries. Nevertheless, there has been no major leap in performance and cost of energy
storage required to minimize this weakness in our electricity infrastructure. Given the history of
electricity storage technology, there is great need for some breakthrough to occur.
The redox flow battery using vanadium salts as electrolytes has been identified within the
scientific community as having good likelihood of becoming a commercial breakthrough solution
in stationary energy storage. The technology appears elegantly simple in theory, and holds much
promise as an ideal energy storage medium. Certain technical limitations as observed in the
designs of the major players in the industry, however, remain as major obstacles in the
technology's road map.
This paper presents a novel, design architecture of a new vanadium battery, which
apparently solves many of the problems inherent in the currently practiced design of the
vanadium battery. The novel technology has the potential to make the vanadium redox chemistry
more commercially viable as energy storage systems and products.
Background
The original patent related to the vanadium battery technology was granted in 1978 to
Pellegri and Spaziante [1]. Unisearch (University of New South Wales, Australia) further
developed a similar battery technology in 1985, exploring various applications. Various
organizations have been licensed to use the Unisearch technology, including Thai Gypsum
Products Public Company Limited (1992), the Mitsubishi Corporation (1993), Federation
Resources Plc. (1998) and the Sumitomo Electric Corporation (1999). Mitsubishi, via its affiliate
Osaki Kansai electric power station, tested a vanadium battery over 12,000 deep charge
discharge cycles until October 1995. Following successful testing of smaller prototypes
Mitsubishi constructed and tested the first 20 kilowatt prototype module in 1996 at its Kashima
Kita Power Station. In 1997, the company constructed and operated a large battery (200 kW, 400
kWh).
Pinnacle VRB acquired in 1997 the Unisearch vanadium battery technology and added
Sumitomo Electric Corporation as another licensee of the technology in 1999. Sumitomo has
been actively developing the vanadium battery for load leveling and peak shaving applications
for office buildings in Japan [2]. System sizes have been in the range of 200 kW to 500 kW.
In all of the abovementioned applications, the vanadium batteries have the components,
including plastic frames, membrane, electrodes, etc., stacked together and bolted in a ``filter
press'' configuration. Electrolytes are pumped through the cell stack flowing in a parallel
geometry, and are distributed to each cell by channels in the plastic frame typical of a filter press.
The current is collected at the side of the stack by exposed copper plates.
Although the vanadium battery is an inherently simple battery with great potential for low
manufacturing cost, very long life and high efficiency, achieving this potential will be very
difficult to realize with the existing design of the technology. A better solution is required.
New Vanadium Batteries
Following the science of the original vanadium battery technology patented by Pellegri
and Spaziante in 1978, a team of European scientists, with long history in academic and
industrial research and development, working since 1996, has achieved a major breakthrough in
creating a novel design architecture of the vanadium battery. As a result of this achievement, the
prospects are much better for realizing very lowcost manufacturing methods to produce
vanadium batteries that will be significantly more durable and more efficient than the best lead
acid batteries available in the market today. Moreover, economical production is possible for
vanadium batteries in modular sizes as small as 3 to 5 kilowatts, thus potentially enabling wide
spread use of energy storage for small, distributed applications. The technology of the new
vanadium batteries is also easily scalable to megawatt sizes.
This novel technology is now owned by Squirrel Holdings Limited, and Cellennium
Company Limited has acquired from Squirrel the rights of the use and development of the new
vanadium batteries in Thailand.
How a vanadium battery works
A vanadium battery consists of vanadium sulfate electrolytes, which store and deliver
electricity by means of reductionoxidation reactions in electrochemical cells. In the design of
vanadium batteries the electrical storage capacity (kilowatthours) and the electrical power rating
(kilowatts) can be chosen independently over wide ranges (watts to megawatts). This is because
the storage capacity is determined by the quantity of liquid electrolytes used, and the power
rating is determined by the area of the membranes in the electrochemical cells.
The battery consists of two electrolyte tanks with the electrolytes of V2+/ V3+ and
V4+/V5+ in a weak acid solution, pumps and a cell stack. The two electrolytes are pumped into
the stack where they are separated by an ionic membrane. The electron exchange in the aqueous
phase takes place at carbon electrodes with corresponding changes in oxidation states according
to the following illustrations (Figures 1a and 1b):
Figures 1a and 1b: Changes in
Oxidation States of Vanadium Ions During Charge and Discharge Cycles of the Battery.
One advantage of the vanadiumvanadium battery over other redox flow batteries is that
cross contamination of the electrolytes does not damage the system since the metal ions are of the
same element. Mixing of the electrolytes creates only heat, and does not destroy the usefulness of
the electrolytes. Electrolyte service life is thus indefinite.
Unique features of the New Vanadium Battery
The unique features developed by Squirrel Holdings Limited are as follows:
- The electrolytes are fed through a stack of cells in series instead of in parallel as in
other designs.
- The cells in a stack consist of pairs of high precision molded structural
components designed for speedy "LEGO style" errorfree assembly with oring
sealing to prevent leaks.
- The electrodes, sandwiched between novel glassy carbon bipolar plates and the
cell membranes, consist of carbon fiber mats permeated by a system of fine
channels to distribute the electrolyte through the whole area with very small flow
resistance.
- The cells are placed horizontally in a vertical stack to make a compact and
structurally stable unit.
- A novel hydraulic feature within the system allows the battery to be ``black
started'' from a state of total inactivity without the need for priming of the
electrolytes from outside sources.
- Production of the electrolytes can be done modularly and electrochemically,
operating at room temperature, without the addition of chemicals.
The following figures show a prototype 1kW cell stack (Figure 3), and a schematic
illustration of the new vanadium battery system (Figure 4):
Figure 3: ``Squirrel 200'' prototype
cell stack, 1 kW. Figure 4: New Vanadium Battery
Advantages of the New Vanadium Battery Features
- The series flow pattern eliminates electrical losses suffered by other designs where
a short circuit current flows through pipes feeding electrolytes to the cells in
parallel.
- The series flow pattern ensures that every cell receives the same amount of
electrolyte and no cell can become dry while the battery is operating. In designs
with parallel flow an undetected blockage in one cell during charging will cause
the evolution of hydrogen and oxygen gases, a large pressure difference across the
membrane, and an explosion if the membrane breaks and the gases are ignited
electrically. In the new vanadium battery volumetric pumps keep all the cells
clear of blockages, but charging is stopped automatically by a pressure switch if a
blockage is not cleared at once.
- Vertical stacking of the cells in the new vanadium battery with the electrolyte
flowing upwards allows any unwanted hydrogen and oxygen gas to be flushed
safely to the top and removed.
- In the new vanadium battery, because of the low resistance to flow in the carbon
fiber electrodes and the impossibility of single cell blockages, only 1% of the total
power rating is needed to pump the electrolytes at the optimum rate. Other
designs have twenty times the necessary minimum flow in order to guard against
cell blockages, and at least 10% of the total power is needed for pumping.
- In the new vanadium battery the total voltage across the stack remains constant
equal to the average of the charged and uncharged voltages. This is because the
series flow pattern and slow pumping speed allow the electrolytes to enter a stack
of cells in the uncharged state and exit the stack fully charged during charging, or
vice versa during discharging. In parallel flow designs the total voltage varies
widely during repeated recirculation of the electrolytes (1.1 V to 1.6 V per cell).
The new vanadium battery will not suffer the serious difficulties created in many
applications by this voltage variation.
- The unique design of the components in the stack of cells ensures that only a small
percentage of the valuable membrane area is wasted to hold the membrane in
place.
- The compact stacks of cells in the new vanadium battery occupy only 20% of the
space used by the current vanadium battery with the same power rating.
- The power efficiency of the new vanadium battery is expected to reach 90%
overall, as compared with 70%80%, not taking into account the pumping power,
of other designs.
- The electrolytes can be produced anywhere on a justintime basis without the
need for longdistance transportation of water, which comprises over 50% of the
electrolyte's weight and volume.
Conclusions
Just as the system of water storage tank and filtration can provide availability of clean
water for the homeowner, so too can a proper battery storage system enhance the reliability and
quality of electricity for its stakeholders. With efficient, durable and affordable storage of
electricity, both suppliers of electricity, namely generation, transmission and distribution
companies, and end users, namely offices, factories and even residential customers, will benefit.
On the supply side, the electrical utilities benefit from the ability to level the load of their
generators, allowing these prime movers to run closer to the average rather than the peak level of
electricity demand. The end results would be the saving of valuable fuel and the deferral of
investment to build more power plants. Additionally, the transmission and distribution companies
benefit from the effectively increased capacity of their installed infrastructure.
On the demand side, end users benefit from the reliable and highquality power, even
when the electricity coming off the grid is poor and intermittent. In fact, with proper storage, the
end user can even choose not to be gridconnected, opting instead for his own smallscale
generation, whether it be from micro turbines, hydrogen fuel cells, biomass, solar PV or wind
turbines.
Just imagine a city like Bangkok without the ubiquitous household water tanks. In the
morning rush to take baths and showers, the nightmare would become apparent for the public
water works authorities whose piping network is all but woefully undersized, and for the city's
residents who are left high and dry. With technologies such as the new vanadium batteries,
affordable electricity storage, properly sized for the end users, may become just as indispensable
to the developing world's population as the ubiquitous water tanks of Bangkok are to that city's
residents.
References
- [1] Pellegri A. and Spaziante P.M., UK Patent GB 2 030 349 A 10, July 1978.
- [2] Takefumi I., Takashi K., Atsuo I., Kouhei K. and Hara T. and Nobuyuki T., ``Development
of Vanadium Redox Flow Battery System'', Proceedings of the Society of Automotive Engineers,
Inc. (1999) 1999012616.
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quick and dirty HTML-version by Norbert Haley Date: Sat 16.12.00 Time: 05:15:45
A few words of my own (don't read it, its terribly trite) ...
... of course you realise that a battery is the last thing the corporations want.
A battery that is good (and has long life) will make you independent from them,
and that is bad for business. Therefore, when you ask the private-power
they will always shrug their shoulders and say something
like 'it can't be done' .. 'we tried, but it was no good' ...
They are
only too happy if people make overly great claims as to the benefits
of this invention for all.
As these are always part of a dream, they will call you a dreamer.
They like dreamers, because they use them to discredit the serious people
(like the ones above) and their attempts at making people more independent.
Corporations have managed to get huge chunks of public infrastructure
privatised, and make enormous profits at the expense of the public.
Public schools and public kindergardens are not important to them,
the well-off can pay always pay for private ones. Running vital infrastructure to them
is the best business. It has assured customers, and with only a few
major players, prices can be fixed and markets squeezed
Private power hates government and all regulation of their
power. They largely succeed in telling the public that government
is wasteful and corrupt. We all believe it now. Never mind that
we set it up ourselves and we originally wanted to be a fair
and peaceful society. For corporations, war and death can be
very profitable. Dick Cheney's company runs a military air-base in Turkey.
And the USA tax-payer foots the bill.
The amount of money spent on propaganda for their aims in
the last century is staggering. And they have won the
battle for the minds of the people, as the example of USA shows.
People there even vote against their own interests, so confusing
are their media in their coreographed dance around simple truths.
.. and now sports.
Who is this guy? I am not much different from you. I just happen
to publish web-pages and I listen to (and read)
Noam Chomsky and I find
that his statements pertain to political reality much more that anything
else that I read of hear in the media. He makes a lot of sense to me.
Listen to him, just type the word Chomsky into
this search-thing.
You will read the paper differently tomorrow. And if you are
a woman, keep reading woman's weekly and cosmopolitan.
Chomsky is nothing for you, you can't handle the truth as you don't believe
that there is such a thing. Also your power over men is best exerted
in private. Don't even think about organising in groups and try
to participate in a meaningful way. Go here now.