ABSTRACT: In today’s developing world the need
for energy is growing exponentially on the other hand it’s environmental
effects are attracting our attention. Researchers believe that increasing
levels of greenhouse gas emissions are changing the climate around the globe.
Fulfilling the growing energy needs and solving environmental problems at
present would be a big investment for our future. Although renewable energy
sources can provide superior environmental performance but for long term,
incremental investments in a new domestic energy source infrastructure is
necessary for the next century. Trend in energy use from the past indicates a
slow transition from fuels with high carbon content, starting from wood to
fuels with more hydrogen. Hydrogen is the most suitable fuel for fuel cells
because of excellent electrochemical reactivity as well as zero emission
characteristics. Fuel cells were used in the past in the space program to
provide electricity and drinking water for the astronauts. In future, the combination of high efficiency
fuel cells and fuels from renewable energy sources would nearly eliminate
greenhouse gas emissions. The early transition to lower carbon based fuels will
begin to create cleaner air and will satisfy the growing energy needs. In this
paper analysis of developing Fuel cell Technology is carried out and is
presented for different applications.
Keywords: Clean fuels, Fuel Cell, Power Generation, Renewable
Energy.
INTRODUCTION
World is witnessing a worsening
global warming situation as generation is continuously being increased
throughout the world using fossil fuels. Higher energy generation through
fossil fuel imparts environmental degradation and is now a matter of concern
globally. The balance of evidence suggests that there is a discernible human
influence on global climate. This calls for optimization of generation of
energy through well-known sources and also for conservation in the utilization
front as short term measure. The long-term measure really calls for search of
new sources, preferably renewable energy for commercial exploitation. In comparison to other renewable sources fuel
cells have a distinct advantage that it can produce continuous power as long as
they are supplied with a constant supply of hydrogen (Appleby and Foulkes, 1989;
Fuel Cell Handbook, 2000; USDOE, 1998). This ability to deliver uninterruptible
electrical energy makes fuel cells well suited for various applications such as
for security application. However, the use of fuel cell is limited due to high
cost of manufacturing of it’s components. Now due to better technology and bulk
requirements fuel cells are finally coming into the market (Wayne , 2001).
In principle, a fuel cell operates
like a battery but it does not run out or require recharging. It will produce energy
in the form of electricity and heat as long as fuel is supplied. A fuel cell
consists of two electrodes sandwiched around an electrolyte. Oxygen passes over
one electrode and hydrogen over the other, generating electricity, water and
heat. Hydrogen fuel is fed into the anode of the fuel cell. Air (or oxygen)
enters the fuel cell through the cathode. Encouraged by the catalyst hydrogen
atom splits into proton and electron, which takes different paths towards the
cathode. The proton passes through the electrolyte. The electrons create a
separate current that can be utilized before they return to the cathode, to be
reunited with the hydrogen and oxygen in a molecule of water. A fuel cell
system which includes a “fuel reformer” can utilize the hydrogen from any
hydrocarbon fuel like from natural gas to methanol, and even gasoline. Since
the fuel cell relies on chemistry and not on combustion, emissions from this
type of a system would still be much smaller than emissions from the cleanest
fuel combustion processes available (Gerlach , 2002; Twidel,1986).
FUEL CELLS
A fuel cell is an electrochemical
device used to generate electricity. The fuel cell stack is just one component
of the overall fuel cell system. The system has three basic sub-systems: the
fuel processor, the fuel cell stack, and the power conditioner. “Balance of
plant” components include pumps, compressors, heat exchangers, motors,
controllers and batteries. In many cases, standard “off-the-shelf” components
are just not suitable for use in a fuel cell system, and specialized components
must be designed and manufactured. The fuel cell stack utilizes a hydrogen rich
gas stream, and there are several approaches to supplying the hydrogen on-board
the vehicle. Hydrogen can be stored as a cryogenic liquid at -423ºF, held as a
gas in pressurized tanks, or contained with metal or chemical hydrides (which
employ chemical reactions to store and release hydrogen). Or, the hydrogen can
be extracted or “reformed” from liquid fuels such as gasoline, synthetic
hydrocarbon fuels, methanol and ethanol, that act as hydrogen carriers. Fuel
cells are direct current (DC) power generators. In some fuel cell vehicle
applications the fuel cell’s DC power is converted to alternating current (AC)
to run AC induction motors, requiring the use of AC motor controllers (Bose,
2000). In other cases, DC motors are used, governed by DC motor control
systems. Much of the of work and resources committed to the development of
battery electric vehicle drive trains in recent decades is being applied to
fuel cell vehicle applications.
Fuel cells have a distinct
advantage over other clean generators such as wind turbines and Photovoltaic
that it can produce continuous power as long as it is supplied with a constant
supply of hydrogen (Tyagi, 2005; Ellis, 2001). This ability to produce
continuous power makes fuel cells well suited for supporting critical loads for
security applications. The power output of fuel cells is also of high quality
in that it is clean and provides computer grade power free from voltage
disturbances such as sags, spikes or transients. Distributed power is a new
approach utility companies are beginning to implement by locating small,
energy-saving power generators closer to where the need is. Because fuel cells are
modular in design and highly efficient, these small units can be placed on-site
(Tyagi, 2005). Installation is less of a financial risk for utility planners
and modules can be added as demand increases. Utility systems are currently
being designed to use regenerative fuel cell technology and renewable sources
of electricity.
