COMPARISSON OF HYDROGEN APPLICATIONS FOR STORAGE AND ENERGY VECTOR

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1 Proceedings of the 13 th International Conference of Environmental Science and Technology Athens, Greece, 5-7 September 2013 COMPARISSON OF HYDROGEN APPLICATIONS FOR STORAGE AND ENERGY VECTOR C. FUNEZ GUERRA 1, M. MONTES PONCE DE LEON 1 and C. CLEMENTE-JUL 2 1 National Centre on Hydrogen and Fuel Cell Technology Experimentation, Puertollano Ciudad Real. 2 Department of Chemical Engineering and Fuels, Technical School of Mining Engineers. Technical University of Madrid (UPM).Rios Rosas 21, Madrid. carmen.clemente@upm.es EXTENDED ABSTRACT Global energy needs, essential to the maintenance of life on our planet, are leading to a remarkable wear of non-renewable energy sources such as coal, oil, natural gas, or uranium. Until now the humanity has been devoted almost exclusively to consume the huge deposits of coal and oil generated over millions of years, thereby disrupting the cycle of carbon dioxide (CO 2) and thereby contributing to the global warming, derived from the greenhouse effect whose consequences begin to manifest themselves. In a period of time for the tiny hope of life on Earth, estimated at about a billion years, these sources will be sold out; even the alternative resources, such as the oil shale and tar sands will have suffered the same fate. It is conceivable that before that is consumed this exhaustion, humanity will have resolved the problem of energy supply, as for example making it feasible nuclear fusion, which, at the moment, is too elusive to current techniques. In the meantime, the potential effects of climate change that we are living are very serious and, most importantly, irreversible. The world and Europe in general and Spain in particular, cannot afford to wait any longer and must pursue the ideal of a sustainable energy system and free of harmful emissions. While reaching the state of scientific and technical development necessary for a stable supply from nuclear fusion and bearing in mind that, with or without pollution, will be used in one form or another until the last gram of fossil fuel or nuclear, mankind is facing the problem of energy supply universal and clean. With the degree of current knowledge, the renewable energies can be the solution to the problem. The need to adjust the energy supply to the demand in general requires a stage of energy storage. This requirement is more evident than in the case of renewable energy from solar or wind power due to its nature of flashing caused by local weather conditions. The hydrogen is profiled in these moments as the most likely solution to the energy storage. This item is not a primary source of energy such as coal, oil or natural gas. Not found free in nature. This is a "conveyor of energy", such as electricity, so that, as she has to be produced from other forms of energy. Both electricity and hydrogen, are called "vectors" energy. Are forms of "noble" energy, and complementary: you can transform a in another, and take advantage of the benefits of each one of them over the other in the issues of storage, transport, production and use. Different applications of hydrogen for storage and energy vector has been compared to conclude that among the various options for energy storage, hydrogen is emerging right now as the most likely solution to energy storage, with great opportunities and capabilities. Keywords: hydrogen, energy storage, renewable energy

2 1. INTRODUCTION The concept of energy vector applies to those substances or devices that store energy, so that it can later be released in a controlled manner. One of the vectors of greatest interest is the hydrogen, due mainly because of their projections in different applications such as for example its use as a fuel in the automotive industry (Rinfking, J 2002). Many environmental associations defend the use of hydrogen as a clean fuel, however, given the nature of energy vector, can only be considered if it comes from clean to its time of clean and renewable sources of energy (Larminie et al 2003). Its importance lies in the fact that hydrogen as an energy carrier, is inherent in an amount of energy, which can be electrical if fed with the fuel cell. (Fúnez et al 2011). This would allow "accumulate or store" electricity in the form of hydrogen and, among other things, would be released to the enormous amount of electrical power from renewable sources of energy that is lost when not be synchronized supply and demand for electrical energy (Fúnez C., 2012). 2. ELECTRICAL ENERGY STORAGE The storage of electricity as well as technological development comes in response to the need to synchronize supply and demand of a good that, without such systems of accumulation, it would have to be produced and consumed in an instant. The technology involved is diverse, both in how to proceed with the energy storage (in the form of chemical energy, gravitational, electrical, thermal ) as in regard to the characteristics of the storage system itself (power, energy, weight, size, efficiency, speed of loading and unloading, half-life ). On the other hand, within the storage systems, you can distinguish between large and small systems, stationary and mobile systems. To be considered, mainly, stationary systems, since they are the more interest that imply on the rest of technologies discussed. You can also distinguish between systems in terms of the role to play. Although some systems may operate in all the functional categories, the restrictions are given in terms of costs. Well, we can distinguish between: System power quality improvement: only operate in sub-second times to ensure the stability of the power supplied. System power bridge: operate at intervals of seconds to minutes to ensure continuity of service when switching from energy generation source. System power management: are used to decouple generation and consumption of electricity. A typical application is the equalization of the load, which involves loading of the storage system as the cost of energy is to be used when low cost is high. In this way, you can define different applications within the electrical systems in function of the power required and the time in which it is to respond the storage drive. Thus, the systems with low storage capacity and power are used to improve the quality of the power in the network, while larger powers are used to ensure the stability of the transport system. With increased storage capacity and response are the systems that allow a greater penetration of the renewable sources not manageable in the mains, as well as those that help to control the frequency and voltage of the network. (Funez C. 2012). Within stationary systems dedicated to the storage of electrical energy, there are a variety of systems (lead-acid batteries, batteries metal-air batteries, sodium sulphide, vanadium redox batteries, lithium ion battery, ZnBr batteries, NiMH batteries, compressed air, flywheels, superconductors, electrochemical supercapacitors, power plants of reversible

3 cycles, hydrogen, etc.,) but this article focuses on hydrogen as energy storage and vector (see Figure 1). Figure 1. Energy storage: Many jobs to do, many solutions. Source: Electricity Storage Association ASSESSSMENT OF HYDROGEN APPLICATIONS FOR STORAGE ANDENERGY VECTOR The main uses of hydrogen as an energy carrier store and can highlight the following: Uses of hydrogen for manageability of renewable energy facilities. Uses hydrogen to provide stability to the grid. Uses hydrogen as fuel. Uses of hydrogen injected into the natural gas network, Hydricity concept. 3.1 Uses of hydrogen for manageability of renewable energy facilities One possible way to store electrical energy generated in excess of renewable energy plants, is to transform it into hydrogen. The surplus electricity to store is diverted into an electrolyzer, which is a device in which the step of the current dissociates water into its two components: oxygen (O 2) and hydrogen (H 2) as the reaction H 2O -> H 2 + ½ O 2. The H 2 obtained is compressed for easier storage in a smaller volume, whereas O 2, which has no energy content is released to the atmosphere, the component that is already but could be stored for reuse for the electrochemical reaction taking place in the fuel cell (Appleby, A.J. 1996). The H 2 is kept stored in pressure containers until the time that should be used to generate electricity or demand situations management. H 2 is used as the principal reactant in the electrochemical reaction takes place in a fuel cell is a device that combines the oxygen (O 2) or air in the electrolysis previously generated and hydrogen (H 2) according to the reaction H 2 + ½O 2 -> H 2O heat electricity or as fuel for power generation group whose engine is similar to natural gas to hydrogen adapted to generate electricity and thus make manageable the installation of renewable energy (see Figure 2).

4 Figure 2. Sotavento Project. Spain. Gas Natural. Source: Hydrogenics. ( Uses of hydrogen to provide stability to the grid. Due to the model of centralized generation that currently exists in most countries, in which there is great centralized generation centers are usually located away from consumers, with transport distances, there are certain moments in instabilities (current, voltage, etc.,) in the electrical network which can cause problems in the management of the electricity networks mentioned above. (Larminie et al., 2003). The hydrogen, can be used to bring stability to the mains at those points where there may be those stability problems discussed above using electrolysis to generate hydrogen and fuel cell or internal combustion engines to transform the hydrogen back to electricity and heat. (see Figure 3). Figure 3. Frequency regulation on Ontario grid. Source: Hydrogenics. ( Uses hydrogen as fuel Taking advantage of the surplus of renewable energies, as has been mentioned in paragraph 2.1 of this document, you can generate hydrogen and that hydrogen can be

5 used to transform it and inject it into the network such as electricity or as fuel for electric vehicles based on fuel cells. In this way, with the surplus of energy, in addition to storing energy may be building the necessary fuel for transport, getting in this way reduce the energy consumption of the sector and is therefore of the fossil fuels (see Figure 4) (Barbir, R, et al., 1999). Figure 4. Hybrid power plant. Source: Enertrag ( 3.4 Uses of hydrogen injected into the natural gas network, Hydricity concept. The term "hydricity" is used to describe a new energy system in which the hydrogen and electricity are used interchangeably as energy carriers interchangeable. The surplus energy can be used to electrolyze water into its basic constituents H 2 and O 2, and H 2 stored can then be used to generate electricity again, as fuel in natural gas grid and transportation of compressed natural gas vehicles (see Figure 5) (Srinivasan, S. 2006).

6 Figure 5: Hydricity concept. Source AEH 2 ( 4. CONCLUSIONS The current energy system based on fossil fuels and centralized generation has to change in a relatively short period of time to an energy system based on renewable energy and distributed generation. The need to adjust the energy supply to the demand in general requires a stage of storage of energy, this being most important storage in some of the renewable energy due to its nature of flashing caused by local weather conditions. Within the various alternatives for energy storage, hydrogen is profiled in these moments as the most likely solution to the energy storage, with great opportunities and capabilities, giving coverage to a large number of applications. Hydrogen is an energy carrier, like the electricity, that is to say, that it is necessary to use a source of energy to get it. However, hydrogen presents the advantage compared to the electricity to be stored. REFERENCES 1. Funez C Energy Storage Conference Energy Foundation Community of Madrid ( 2. Appleby, A.J Fuel Cell Technology: Status and Future Prospects, ENERGY, vol. 21, no 7/8. 3. Larminie, J., DIicks, A Fuel Cell Systems Explained. John Whiley and sons. 4. Barbir, R, M. Nadal, and M. Fuchs, Fuel Cell Powered Utility Vehicles, in Buchi, F. (editor), Proc. of the Portable Fuel Cell Conference, pp Srinivasan, S Fuel Cells: From Fundamentals to Applications. New York Springer. 6. Fúnez Guerra, C. Garcia Torres, F ISSN: Energy & Mines No. 9.. "Different ways of generating hydrogen. 7. Rifking, J The Economy of Hydrogen. Barcelona, Paidos