Evaluating the use of primary and secondary
cells for portable applications
This diagram represents a fuel cell which is a device that converts
chemical energy into electrical energy, water and heat through
Fuel cell research and development has been
actively taking place since the 1950’s, resulting in many commercial
applications ranging from low cost portable systems for cell phone and laptops
to large power systems for buildings. The fuel cell principle was first
discovered by William Grove in 1839. The core of each fuel cell consists of an
electrolyte and two electrodes. At the negative anode, a fuel such as hydrogen
is being oxidized, while at the positive cathode, oxygen is reduced. Ions are
transported through the electrolyte from one side to the other. The voltage
generated by a single cell is usually rather small (less than 1 volt) so man
cells are connected in a series to create a useful voltage.
Gemini fuel cell section
The Gemini spacecraft consisted
of two hydrogen – oxygen fuel cell battery sections. The Gemini fuel cell
utilised liquid oxygen and liquid hydrogen to generate electricity. Every
battery section consisted of stacks of three fuels cells and every stack had 32
individual cells connected in a series. This generated around 23 to 26 volts.
The Gemini programme help assist in pioneering the usage of fuel cells in space
and subsequently, a similar technology was utilised in the Apollo and various
other space shuttle programmes.
Grove utilised four large cells
each containing hydrogen and oxygen to produce electrical power which then used
to split the water in the smaller upper cell. In 1955, general electric
chemist, Thomas Grubb modified the electrolytes within the cell while another
chemist, Leonard Niedrach added a catalyst to create what is the modern-day
fuel cell. The first successful application of this fuel cell was achieved with
space technology during the NASA Apollo space program.
Figure 2: The fuel cell model shown was taken
from the Apollo spacecraft and consisted of various individual fuel cells
along with plumbing and sensors needed to provide the cell with reactants
and subsequently maintain the temperature of the cell.
The Apollo spacecraft carried three hydrogen
– oxygen fuel cell within the service module. The main materials used in construction
was titanium, nickel and stainless steel. Every unit consisted of 31 separate
fuel cells which were all connected in series and operated at 27 to 31 volts. The reactants were placed and stored in individual
tanks in a liquid form so that they did not consume too much space. This meant
that oxygen was kept at -173oc and at a pressure of 63.26 pa/m2.
Additionally, the waste heat from the fuel cells was utilised in bringing the
reactants to a gaseous form before they entered the cell. The temperature at
which the Apollo fuel cell was functioning at was 206oc. The normal output was between 563 to 1420
watts with a maximum of 2300 watts.
Both Gemini and Apollo
spacecrafts attained electrical power from hydrogen – oxygen fuel cells. In
terms of space applications, fuel cells have a greater advantage over
conventional batteries in which they generate several times more energy per
equivalent unit of weight. When oxygen and hydrogen fuse to produce water,
energy is released due to the electrons within the water molecules being in a
much lower energy state than those within gas molecules. In a combustion
reaction, such as in a rocket engine, the energy appears as heat. However,
within fuel cells, around 50 to 60% is converted directly to electrical energy.
An intriguing fact to mention is that the water produced in those reactions was
used by the Apollo crew for drinking.
The voyager space probe utilised three
radioisotope thermoelectric generators that utilised a thermocouple. A
thermocouple is an electric device comprising of two dissimilar conductors. One
end of the thermocouple is located outside the probe, in extremely cold temperatures
while the other end is located within the probe in a much higher temperature.
The temperature difference between the two ends is what produces electrical
energy. Every generator is provided with 24 pressed plutonium – 238 oxide
spheres and are able to produce around 470 watts of electrical power.
Advancements within battery and fuel cell technology
Lithium – ion batteries represent
a landmark technology that has made the current generation of electric vehicles
possible. However, Lithium – ion chemistries have a certain maximum energy
density that are dictated by laws of physics and today’s batteries are not so
far from theoretical maximum. If drivers keep demanding longer ranges and
faster charging time, then subsequently better technology must be found.
Researchers around the world are working on beyond lithium projects, and over
the past year, there has been several significant breakthroughs. One latest
advancement that has been getting a tremendous amount of attention from
researchers is the solid – state battery. This type of battery utilised a solid
electrolyte instead of liquid electrolyte which is used in today’s
manufacturing. Solis – state batteries could theoretically have double the
energy density of current batteries and last several times longer. They also
consist of a non – flammable electrolyte which is usually glass, polymer or a
combination of either and therefore this would eliminate any safety issues that
plague Li – ion cells.
One major car company which has
taken the initiative to focus on solid state battery advancements are Toyota.
The car maker has quoted that it’s near a breakthrough in engineering
production and this could really help it advance into the production of
electric vehicle by 2020. The improved battery technology would make it
possible to create smaller, more lightweight lithium – ion batteries for
utilisation in electric vehicles and it could potentially boost the total
charge capacity, resulting in longer – range vehicles. Additionally, another
advancement would be that this type of battery would have a much longer useable
life, making it possible to use it in the vehicles their installed in for a
much longer period of time. Batteries
remain a key limiting factor for electric design and the move to solid state
batteries would help make room for more gains in terms of charge capacity
attained while also helping to push further existing efficiencies through the use
of ultra – light materials.
In most recent years, the growing
market for electric cars has increased dramatically and the technology behind
fuel cells has become more and more evident. As you may know, Hydrogen –
powered fuel cells are a green alternative to internal combustion engines
because they generate power through electrochemical reactions, leaving no
pollution behind. The latest breakthrough in fuel cell technology comes when Hyundai
released their latest model called the Nexo. This state of the art car has been
installed with a hydrogen fuel cell that promises greater efficiencies than
various other fuel cells that are out there in today’s market. Additionally,
the fuel cell used in this new model has been said to improve the range to 370
miles that can top off its fuel in just under five minutes. This is said to be
a marked improvement over various other models like the Tuscon FCEV, Tesla
model 3 and the Chevrolet Bolt.
Another major breakthrough comes as a team of
engineers at the University of Delaware has developed a technology that could
make fuel cells cheaper and more durable. Materials known as catalysts spur
these electrochemical reactions and platinum is the most common catalyst in the
type of fuel cells used in vehicles. A disadvantage found is that platinum can
be expensive and the metal costs around £20,000 per kilogram. Instead, the team
of engineers formed a catalyst of tungsten carbide which goes around for £100
per kilogram. The researchers made tungsten carbide nanoparticles by utilising
a number of processes such as hydrothermal treatment, separation, reduction and
carburization. The group of researchers then incorporated the tungsten carbide
nanoparticles into the membrane of a fuel cell. Automotive fuel cells which are
referred to as proton exchange membrane fuel cells consist of a polymeric
This type of membrane wears down
over time, especially if it undergoes too many wet or dry cycles. When tungsten
carbide is incorporated into the fuel cell membrane, it humidifies the membrane
at a level that optimises performance. It has tested to be up to 60% more
efficient than standard hydrogen fuel cells. The tungsten carbide catalyst also
improves the waste management of water of fuel cells and also captures damaging
free radicals before they can degrade the fuel cell membrane. As a result,
membranes with tungsten carbide nanoparticles last much longer that standard
ones. The low – cost catalyst developed can be incorporated within the membrane
to improve performance and power density. As a result, the physical size of the
fuel cell stack can be reduced for the same power, making it lighter and
cheaper. Furthermore, the catalyst is able to deliver high performance without
sacrificing durability which is a major advancement in the future of fuel
In conclusion, both battery and
fuel cell technologies are increasingly advancing as we speak of and is
changing the way we get our source of energy more efficiently. The technology
being developed has the potential of changing current fuel technologies but it
is still undergoing various kinds of research and experimentation in order to
ensure it is much more efficient and reliable for consumers to utilise.