Hydrogen as the best choice for fuel
Sustainable development requires a supply of energy resources that is sustainable, available at reasonable cost and causes no or minimal negative effects. Fossil energy resources are finite, and thus lack the characteristics needed for stability and sustainability, while green energy sources are sustainable over the relatively long term (Dincer, & Rosen, 2004). Particularly, cost effective and environmentally benign green energy is the most essential means for increasing the sustainable technological development and industrial productivity as well as people’s living standard in a society.
Therefore, permanent and effective hydrogen energy strategies should be put forward to increase the use and application of hydrogen from non-fossil fuel sources and green energy based hydrogen technologies (Midilli et al, 2005). Hydrogen has been widely considered as a potentially viable alternative to fossil fuels for use in transportation. In addition to price competitiveness with fossil fuels, a key to its adoption will be public perceptions of hydrogen technologies and hydrogen fuel (Hickson et al, 2007).
According to Dunn (2002) three factors have driven the development of alternative fuels for use in transportation. These are reducing the undesirable effects of greenhouse gases on climate, decreasing dependence on fossil fuels, thereby increasing energy security, and reducing local air pollution. Efforts to develop alternative fuels have primarily focused on bio-fuels, such as methanol, ethanol and bio-diesel and the advancement of hydrogen technologies.
At the fuel production stage, both bio-fuels and hydrogen can be developed from renewable sources, the former through the refinement of products such as grains and oilseeds, and the latter through harnessing wind energy for electrolysis. While both groups of fuels provide for a reduction in greenhouse gas emissions, hydrogen is often considered the gold standard as the sole by-products of combustion are water and nitrogen oxides. Current energy chains deplete non-renewable resources and release harmful pollutants, producing waste and both local and global pollution.
A wider and long lasting development can exist only through realization of energy cycles using renewable energy sources and to achieve no impact on environment. Hydrogen is the simplest and most diffused chemical element, obtainable in many ways, with an efficient and clean use, and high calorific value represents the best storable energy vector to realize a global closed cycle of energy resources (CCER) (Orecchini and Bocci, 2007) . Hydrogen can be produced by using fossil fuels such as oil, coal and natural gas or renewable energy sources as water.
Hydrogen in high purity can be produced through the electrolysis of water. The required electrical power can be supplied by renewable energy resources such as solar, wind, wave, tide or hydraulics (Kahraman et al, 2006). Price competitiveness depends on the relative costs of hydrogen, bio-fuels and fossil fuel alternatives. The cost of producing hydrogen varies significantly by the type of technology and distribution channel. The United States National Research Council and National Academy of Engineering (2004) found that total costs of hydrogen ranged from $1.
91/kg for hydrogen made from coal and shipped by pipeline to $6. 58/kg for hydrogen made onsite from electrolysis. Given that future cost paths of these technologies are largely unknown, as are the prices of fossil fuels, the price competitiveness issue is not currently resolvable. The attributes of green energy based hydrogen energy system (e. g. , modularity, flexibility, low operating costs) differ considerably from those for traditional, fossil fuel based energy technologies (e. g. , large capital investments, long implementation lead times, operating cost uncertainties regarding future fuel costs).
Green energy based hydrogen energy system can provide cost-effective and environmentally beneficial alternatives to conventional energy systems. Moreover, for sustainable development, hydrogen energy and hydrogen energy system can play an important role in meeting energy requirements in both domestic and industrial applications. Green energy based hydrogen energy technologies now become a key component of hydrogen energy based stability and sustainability due to the fact that it is a renewable energy based, practically carbon free, and light gaseous alternative fuel.
The use of hydrogen as an alternative engine fuel fulfils certain basic criteria such as availability, high specific energy content, minimum pollution, easy and safety storage along with transportation. Hydrogen has proved its suitability over many fuels in these criteria. Hydrogen does not cause combustion problems such as vapor lock, cold wall quenching, inadequate vaporization or poor mixing, and does not produce toxic products. Its heating value is high on mass basis whereas low on volume basis.
Due to the above and other thermo-physical properties, hydrogen has unique and desirable heat transfer characteristics (Kahraman et al, 2006) The production of hydrogen energy favor system decentralization and local solutions that is somewhat independent of the national network, thus enhancing the flexibility of the system and providing economic benefits to small isolated populations. Also, the small scale of the equipment often reduces the time required from initial design to operation, providing greater adaptability in responding to unpredictable growth and/or changes in energy demand Midilli and Dincer, 2007).
Numerous stand-alone power systems (SAPS) have been installed around Europe. These systems provide power to technical installations and communities in areas that do not have access to the regional or national power grid. An increasing number of SAPS include renewable energy (RE) technologies (solar or wind power), often in combination with diesel generators and/or batteries for back-up power, but the majority of larger SAPS are still based on fossil fuel power production.
Replacing diesel generators and batteries by fuel cells (FC) running on locally produced hydrogen would diminish fossil fuel dependence, reduce environmental impact and potentially reduce operation and maintenance costs (Zoulias et al, 2006). The replacement of conventional technologies, namely diesel generators and/or batteries by hydrogen technologies including fuel cells in RE based stand-alone power systems is technologically feasible, reduces emissions, noise and fossil fuel dependence and increases RE penetration.
Dumped excess energy is also reduced in such power systems (Zoulias and Lymberopoulos, 2007). The fuel cell running on hydrogen is the most attractive option for passenger cars. It eliminates emissions on the tank to wheel path, the fuel can be produced from many sources, and it provides very high average efficiencies. This is due to the fact that the fuel cell reaches highest its efficiency at part load. Passenger vehicles are mostly operated at part loads significantly below their rated power, so that the efficiency gain offered by fuel cells can be highest (Helmolt ; Eberle, 2007).
Research that is being done in the US shows that ammonia borane holds promise as a chemical compound to store and release hydrogen for use in vehicles powered by fuel cells and it also appears stable enough to offset some safety concerns. Study of potential safety issues associated with premature release of hydrogen gas when stored on board a vehicle at relatively high temperatures indicate that the stability of ammonia borane relates to its purity, and can remain stable for many days at high temperatures.
However, further research will help determine whether auxiliary cooling is required to minimize the inadvertent release of hydrogen in a tank and keep the vehicle safe. 1 1. Hydrogen storage material has potential, Fuel Cell Bulletin, Vol. 2006, issue 11, November, p. 11 One of the most promising and studied technologies for large storage of renewable energy in chemical forms is the production of hydrogen by water electrolysis, which can be stored and transported in compressed or liquid form.
Liquefaction is a high energy consuming process, but allows higher storage densities and can represent the appropriate solution when large scale hydrogen storage and long range transport is needed. Also it allows a zero net emission energy cycle when produced using RES electric energy with higher efficiency than other synthetic fuels like methanol (Weimer et al, 1996). Hydrogen can perform as a suitable storage and transmission vector for RES energy, allowing the utility to increase its flexibility in responding to fluctuations in wind or solar input or consumer demand.
Considering end user applications, hydrogen is a versatile fuel that can be substituted for traditional fuels, whether for stationary or transport applications (Peschka, 1992). The major obstacle involved however, to the introduction of hydrogen fuel cell vehicles (FCVs) is the absence of a hydrogen infrastructure. A full scale hydrogen infrastructure with production facilities, a distribution network and refueling stations is expensive to build. The venture of constructing a hydrogen refueling infrastructure constitutes a long term, capital intensive investment with great market uncertainties for FCVs.
Reducing the financial the financial risk is a major objective of any long term goal to build a hydrogen infrastructure (Knight et al, 2001). In order for hydrogen to become a future fuel of choice it must first overcome a variety of obstacles. Amongst the barriers outlined by McDowell and Eames (2006) are: • Price competitive with other fuel sources, • Lack of refueling infrastructure, • Technology immaturity, and • Overcoming negative public perceptions.
According to an optimistic hypothesis made by Marban and Solis (2007) hydrogen and FCs will be able to provide the global energy demand in transport far beyond 2050. In order to supply hydrogen to areas far from the general network, refueling stations will be required to be built by means of electrolysers fed by renewable energies (such as photovoltaic solar panels or windmills) or biomass reformers. However, most of the supply can be provided by a network of refueling stations in which hydrogen will be supplied by a piping system connected to large scale production plants (Marban and Solis, 2007).
Development and utilization of hydrogen energy system and strategies should be given a high priority for sustainable development in a country. The need for sustainable energy development is increasing rapidly in the world. Widespread use of green energy based hydrogen energy system can be important for achieving global stability and sustainability in both developing and industrialized countries. Thus, hydrogen energy and technologies are needed for global stability that ensures the global sustainability.
The relation between green energy based hydrogen energy system and sustainability is of great significance to the developed countries as well as developing and/or less developed countries. Moreover, examining the relations between hydrogen energy system and sustainability makes it clear that green technology is directly related to sustainable development. Therefore, attaining hydrogen energy based sustainable development requires that hydrogen energy from non-fossil fuel sources and hydrogen energy system be also used, and is assisted if hydrogen energy resources are used efficiently (midilli and Dincer, 2007).
Biomass hydrogen production has attractive features for the realization of closed cycle of energy resources (CCER), even if technical, energetic, economic, environmental, and social analyses of the specific production use system have to be made. Moreover, gasification/anaerobic digestion plus reforming seems to be already competitive and other technologies, like fast pyrolysis/reforming, are suitable even if in the development stage. Thus, hydrogen biomass can play an important role into the future world’s energy supply (Orecchini and Bocci, 2007).
Hydrogen produced through non-fossil fuel sources by using the different forms of sustainable energy sources, such as solar, hydropower, wind, nuclear, etc. (so-called green energy based hydrogen production), is considered to be a prime fuel in meeting energy supply and security, transition to hydrogen economy, environmental betterment, and social, societal, sectoral, technological, industrial, economical and governmental sustainabilities in a country. Thus, green energy based hydrogen system can be one of the best solutions for accelerating and ensuring global stability and sustainability.
Therefore, the production of hydrogen from non-fossil fuel sources and the development and application of green energy based hydrogen energy technologies become crucial in this century for better transition to hydrogen economy (Midilli, ; Dincer, 2007). As a clean fuel, hydrogen is expected to be one of the primary energy carriers in the 21st century. In order to achieve the object of using hydrogen not only as raw material for chemical engineering but also as energy, it is important for producing hydrogen with low cost and large scale, at the same time reducing CO2 emissions.
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