HYDROGEN AS A SOURCE
OF ENERGY
Science has unlimited potential in every
field. It can find solutions in every problem area not visualised
before. What would one say on being told that hydrogen is now being
promoted as a clean fuel and energy storage medium for various applications?
Hydrogen can be produced through biological
conversion of various organic effluents from industries like distillery,
starch and sugar processing. It can also be produced through electrolysis
of water using renewable energy. The by-product hydrogen gas, which
is available from several chemical processes, plants or industries,
can also be utilised as a fuel. Hydrogen can as well be used in
homes, industries, transport and commercial and agriculture sectors
alike. The use of hydrogen could be an important means of reducing
greenhouse gas emissions and improve air quality, especially in
the highly congested urban areas, besides substituting fossil fuels.
The Ministry of Non-conventional
Energy Sources(MNES) is supporting a number of research, development
and demonstration projects on various aspects of hydrogen including
production, storage and utilisation of hydrogen as a fuel. Various
research, scientific and educational institutions, laboratories,
universities and industries are involved in implementing the projects.
Hydrogen is produced
on a commercial scale by steam reformation or partial oxidation
of such hydrocarbon fuels as natural gas and naphtha. It can also
be produced using environment-friendly technologies and renewable
energy sources. Electrolysis of water is a well-established an
environmentally safe technology for producing hydrogen. Moreover,
it is based on non-fossil energy. Hydrogen can be produced through
direct heat, thermo-chemical and electrolytic and photolytic methods
from water and solar energy. In the electrolytic method, hydrogen
can also be produced through electrolysis of water by supplying
direct current electricity to the cell electrodes. Solar cells
and photo electrochemical cells can be used as a source of direct
current electricity, if found feasible, for producing hydrogen
on a small scale.
Methods
MNES is funding R&D
projects to produce hydrogen using renewable energy sources. A
project for pilot scale production of hydrogen by photo catalytic
decomposition of water using semiconductor photo catalyst, which
can be activated by solar radiation, was sanctioned to the Banaras
Hindu University (BHU), Varanasi. For commercial production of
hydrogen using this technology, it is necessary to develop suitable
catalysts, which are active, cheap and durable. Work carried out
under this project had shown that platinum-cadmium sulphide dispersed
on alumina is highly active and durable photo catalyst for the
reaction when suitable electrolytes are present in water. Catalysts
prepared by different techniques were characterised and further
work is in progress for increasing the activity of the photocatalysts
and also to establish the kinetics of the reaction.
The method of biophotolysis
utilises living systems or materials derived from such systems
to split water into hydrogen and oxygen by sunlight. Oxygen is
evolved from the green plant but hydrogen and electrons are removed
by interaction with carbon dioxide from the air to produce simple
sugars. Certain single cells called green algae are able to make
the enzyme hydrogenase. In these algae, eliminating carbon dioxide
can circumvent the second stage of photosynthesis. Then hydrogen
ions and electrons in the presence of hydrogenase form the hydrogen
gas. Thus the exposure of these algae to sunlight and water mixed
with essential mineral salts yields a mixture of oxygen and hydrogen
gases that can be separated in various ways.
One of the main objectives
of research on the decomposition of water by sunlight is the efficient
simulation of biological process with or without using biological
materials. Under the MNES-funded project, Shri AMM Murugappa Research
Centre (MCRC), Chennai has demonstrated the production of hydrogen
from industrial wastes using defined co-culture of bacteria (10,000-litres
capacity per day). MNES has now sanctioned a project to MCRC for
setting up a larger capacity photo bioreactor (75,000 litres a
day capacity) for producing hydrogen from industrial effluents
and bacteria in Tamil Nadu.
Storage Techniques
Special storage systems
are required for safe handling of hydrogen gas at the site of
its application, thus avoiding the need for long distance transportation.
The most common storage modes are - gaseous, liquid and solid
state. However, the gaseous storage mode, a well-established technology,
can be used for stationary applications. Storage of hydrogen in
the form of gas requires large volumes. Pressurised gaseous storage
of hydrogen requires special attention and safety storage equipment.
Storage of hydrogen in liquid form is somewhat better than that
of gaseous storage because of better volume efficiency. The liquid
storage mode can be used for some specialised use only such as
for propulsion of rockets in the space.
For the use of hydrogen
for mobile applications, it is necessary to select an appropriate
storage system. Storage of hydrogen in metal hydrides has many
distinct advantages over gaseous or liquid hydrogen storage. This
type of storage is considered safe especially for portable applications.
For more efficient storage at reduced weight of the storage system,
lightweight hydrides are also under development. Waste heat of
the vehicle engine or combustion process is used to release hydrogen
contained in metal hydrides. Research groups at BHU, Varanasi;
Defence Metallurgical Research Laboratory, Hyderabad; CECRI, Karaikudi
and IIT Madras are working on metal hydride storage materials
and methods.
The research group
at BHU is developing hydrogen storage materials and systems for
vehicular propulsion and other applications. Hydrogen-powered
two-wheelers have been operated and road-tested, using metal hydride
storage. BHU was able to achieve the range of the two-wheeler
up to 60 km. Efforts resulted in improving the overall performance
of the vehicles.
The Ministry has
sanctioned a project of BHU for demonstration of 50 hydrogen-fueled
motorcycles. As part of this project, the production of hydrogen
using water and solar energy will also be demonstrated. Hydrogen
will be stored as reversible solid state mischmetal type hydrides.
The possibility of using graphite nano-fibres as new hydrogen
storage materials in the two-wheelers will be explored.
Utility
The use of hydrogen
has been demonstrated in fuel cells for stationary, portable and
automotive applications. Hydrogen is the primary fuel for fuel
cells. Under the MNES-funded projects, the hydrogen-fueled two-wheelers
have been developed and tested on road conditions. Small prototypes
of hydrogen-based gen-sets and catalytic burners for domestic
and industrial applications have also been developed. Under an
R&D project sanctioned by MNES, the research group at IIT
Delhi is working on a low-polluting hydrogen-diesel dual fuel
engine. The existing diesel engine will be run on hydrogen using
specially designed fuel injection system.The performance, exhaust
emission characteristics of the hydrogen-diesel dual fuel engine
and the extent of substitution of diesel by hydrogen will also
be studied under this project.
The University of
Rajasthan, Jaipur, under an MNES-sponsored project had demonstrated
the application of hydrogen for water pumping on an experimental
basis. The reaction involved in the formation and decomposition
of hydrogen liberated from the metal hydrides runs the pump. In
this experiment, a bulk hydride bed was used to run a small pump
for lifting water. Alternatively, heating and cooling the hydride
bed using hot and cold water achieved the pumping action.
Research is going
on all over the world on hydrogen energy technologies and projects.
Electrolysers in different sizes have been developed in Germany
for production of hydrogen from water splitting. Hydrogen filling
stations to fuel buses and cars have been set up in Hamburg and
Munich.(PIB Features)
Contributed
by Smt. Swatantra Radhakrishnan, Information Officer, PIB, New
Delhi.
