We are living in a world that is quickly losing its conventional energy resources. If we look at the state of the conventional fossil fuels such as oil and gas, we see that their prices have been highly volatile in the past few decades. The use of such fossil fuels also causes some serious environmental issues that include global warming, ozone layer depletion and acid rains. The development of renewable source of energy such as solar, wind, biomass and geothermal sources will help in the reduction of consumption of petroleum products and will lead to fulfilling the energy requirements of the world. In order to develop a sustained alternate energy source, it is important to develop a suitable energy carrier which can store, transport and distribute energy.
Hydrogen as an energy carrier
Hydrogen is one of the most popular carriers of renewable energy. One of the best examples of utilizing hydrogen as an energy carrier is the ocean energy. The ocean energy generates electricity, which is then electrolyzed to produce hydrogen. Hydrogen is then further converted into electricity and transported to the end user with the help of fuel cells and other devices. Hydrogen is recognized as clean energy carrier and is comparable to the energy that is produced by conventional fossil fuel. If we talk about the conventional method of producing hydrogen, it will involve reformation of fossil fuels.
An alternative way of producing hydrogen involves converting organic pollutants into hydrogen, instead of methane. Hydrogen is considered to be one of the best alternatives to fossil fuels because it has a wide range of industrial applications, and it is utilized for the hydrogenation of petroleum, coal and shale oil.
Biohydrogen is one of the most promising forms of next generation fuel. At this point, there are four processes for producing Biohydrogen. First is the biophotolysis of water with the presence of algae/ cyanobacteria. Second is the photodecomposition of organic compounds using photosynthetic bacteria. Third is the fermentative hydrogen evolution using anaerobic bacteria and fourth is the combination of fermentative and photosynthetic methods. Apart from the above methods, hydrogen can also be produced from the waste waters of food processing industries, chemical industries, paper mill industries and distillation industries.
Cryogen (Liquid Nitrogen) as an energy carrier
The cryogen is produced by the help an air separation process by which the cryogenic engine coolers liquefy the major components of air by the help of Joule- Thomson effect. Since electricity conversion process is not required in case of cryogen production, it is considered to be more competitive and cost effective when compared to hydrogen production. Moreover, the extraction of energy is much simpler in case of cryogen, when compared to hydrogen. Liquid nitrogen is heated, and it then expands to produce power.
However, if we look at the energy efficiency of cryogen, we find that it is about 40% as the majority of energy is wasted in form of cold during the heating process. However, the efficiency of cryogen can be increased further by superheating the working fluid with the help of other forms of renewable energy source.
Conclusion and Recommendations
In order to develop alternate sources of energy, it is very important to choose the right energy carrier. In this case, we compared the efficiencies of two energy carriers, hydrogen and liquid nitrogen. Although hydrogen is a viable energy carrier option due to its industrial applications and technique of producing hydrogen from waste water is moving forward, it is a cryogen that would be preferred over hydrogen because cryogen production has few technical limitations. Also, cryogen is cheaper to produce, and its efficiency can be increased by using low grade heat for cryogen energy extraction.
Although hydrogen is more popular and regarded as a clean carrier for energy, liquid nitrogen can be produced when air is used as an oxidant. Since there is no chemical transformation in case of production of cryogen, it is more environment- friendly when compared to hydrogen. A solar- cryogen hybrid energy system must be developed and effectively utilized by businesses to produce clean and alternate energy, which can be a great alternative to the expensive conventional fossil fuels.
- Price of fossil fuels has been highly volatile.
- A pressing need to develop alternative sources of energy.
- Alternate sources of energy to reduce consumption of fossil fuels.
- Hydrogen is regarded as one of the most popular carriers of renewable energy
- Hydrogen can also be produced from the waste waters of food processing industries, chemical industries, paper mill industries and distillation industries
- Bio hydrogen is one of the most promising forms of next generation fuel.
- Cryogen is another popular energy carrier.
- Cryogen is more competitive and cheaper than hydrogen as an energy carrier.
- Cryogen efficiency can be further increased by superheating with solar energy.
- Cryogen must be preferred over hydrogen as an efficient carrier option for producing alternate energy.
- Cryogen is more environment- friendly when we compare it with hydrogen.
- A solar-cryogen hybrid energy system must be developed and marketed globally.
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Kothari, R., Singh, D.P., Tyagi, V.V & Tyagi, S.K. (2012) Fermentative hydrogen production- An Alternative clean energy source. Renewable and Sustainable Energy Reviews. Print.