Hydrogen - a colourless, odourless gas is increasingly gaining attention as a future source of energy free from environmental pollution. Its new use has been found in the automobile and power generation sector. The biggest advantage with hydrogen is that it has the highest energy content per unit mass among known fuels and it burns to produce water as a by-product. It is, therefore, not only an efficient energy carrier but also an environmentally benign fuel as well. In fact, the Ministry of New and Renewable Energy have been supporting a broad based research, development and demonstration (RD&D) programme on different aspects of hydrogen energy for over two decades.
Consequently, a National Hydrogen Energy Road Map was prepared in 2005 which provides for various pathways for development of hydrogen energy i.e. production, storage, transport, safety, delivery and applications. However, the current technologies for use of hydrogen are yet to be optimized and commercialized but efforts for the same have already started.
Hydrogen Production
Hydrogen is found only in combined state on earth and therefore its production involves the process of its isolation from its compounds, a process which itself requires energy.
Globally, about 96% of hydrogen is produced presently using hydrocarbons. About 4% hydrogen is produced through electrolysis of water.
Refineries and fertilizer plants are major in-situ producers and consumers of hydrogen in India. It is also produced as a by-product in chloro-alkali industry.
Hydrogen production falls into three categories: thermal process, electrolytic processes and photolytic processes.
- Some thermal processes use energy resources while in others heat is used in combination with closed chemical cycles to produce hydrogen from feed-stocks such as water. These are known as “thermo-chemical” processes. But this technology is in early stages of development. Steam Methane Reformation, gasification of coal and gasification of biomass are other processes of production of hydrogen. The advantage with coal and biomass is that both are locally available resources and biomass is a renewable resource too.
- Electrolytic processes use electricity to split water into hydrogen and oxygen and can even reduce the emission of green house gases emission if the source of electricity is ‘clean’.
Hydrogen Storage
- Hydrogen storage for transportation is one of the most technically challenging barriers to widespread commercialization of this technology.
- The most common method of storage is in gaseous state in pressurized cylinders, however, it being the lightest element requires high pressures.
- It can be stored in liquid form in cryogenic systems but would require high amounts of energy.
- It is also possible to store it in solid state in the form of metal hydrides, liquid organic hydrides, carbon nanostructures and in chemicals.
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Applications
Apart from using it as a chemical feedstock in industry, it can also be used as a clean fuel in automobile and also for power generation through internal combustion engines and fuel cells.
In the field of hydrogen in internal combustion engines, R&D projects for using hydrogen blended compressed natural gas and diesel and development of hydrogen fuelled vehicles are being implemented in India.
Hydrogen fuelled motorcycles and three wheelers have been developed and demonstrated in the country. Catalytic combustion cookers using hydrogen as fuel have also been developed.
The Banaras Hindu University, BHU has modified commercially available motorcycles and three wheelers to operate on hydrogen as fuel.
With a view to provide hydrogen blended compressed natural gas as an automotive fuel, a dispensing station for the same has been set up at Dwarka in New Delhi with partial financial support from the Ministry. This facility provides CNG fuel blended with hydrogen up to 20% in volume in demonstration and test vehicles.
A development cum demonstration project for use of H-CNG as fuel in select vehicles (buses, cars and 3-wheelers) is also under implementation. Besides, hydrogen fuelled generator set is being developed by BHU and IIT, Delhi.
Another application of hydrogen energy is the fuel cell, an electrochemical device converting chemical energy of hydrogen directly into electricity without combustion. It is a clean and efficient process of electricity generation. It can be used in UPS systems, replacing batteries and diesel generators.
In view of the relevance of fuel cells in automobiles and power generation, several organizations globally are pursuing RD&D activities in this field. Portable applications are also being developed. The present efforts in these fuel cells are focused on reducing its cost and improving its durability. The focus of the Fuel Cell programme of the Ministry of New and Renewable Energy has been on supporting RD&D activities on different types of fuel cells.
