Hydrogen: Value Chain and its Challenges as a Future Fuel
Shikha Jain (JRF) 1, Sonal Singh (SRF) 1, Avanish K. Tiwari (Senior Principal Scientist) 1 and M R. Nouni (Scientist F/ Director) 2 1Centre for Alternate Energy Research, University of Petroleum and Energy Studies, 3rd Floor PHDCCI House, 4/2, Siri
Institutional Area, August Kranti Marg, New Delhi-110016, India 2Ministry of New and Renewable Energy, Govt. of India, Block No.14, CGO Complex, New Delhi-110003, India
Key words Hydrogen; Transport; Sustainable; Value-chain
1. Introduction
Increasing utilization of fossil fuels for meeting growing energy needs is rapidly impacting the environment adversely throughout the world. As the reserves of fossil energy resources (coal, gas and petroleum) get depleted, increasing trend of energy prices are witnessed, energy security concerns become serious and climatic change issues become paramount, the search for alternate fuels becomes critical and inevitable. Hydrogen, the most abundant element in the universe [1, 2] offers huge potential as a promising and sustainable alternate fuel because of its high energy content, environmental–friendly properties and its capability to ensure energy security. As a result interest in hydrogen energy system has been gaining significant attention world-wide. Hydrogen production, storage, safety, transport, delivery and end-use are components of the hydrogen value-chain. Increasing worldwide CO2 emission levels due to burning of fossil fuels requires a major restructuring of the energy system to reduce the risk of climate change. Along with economic and political crises, health concerns of humans, animals and plant life require major attention. Hydrogen as a clean, environmentally-benign and a sustainable energy carrier holds the potential to provide reliable supply of energy for meeting the growing energy needs of world’s economy while protecting the environment and ensuring energy security. Eventually it is envisaged that hydrogen will join electricity as the major energy carrier, supplying every end-use energy need in the economy, inclusive of transportation, electric power, portable power, and for industrial processes. Transport sector is undoubtedly one of the major consumers of energy utilizing about one quarter of the world total energy [3]. Hydrogen fuel cells have the potential to replace the internal combustion engine in vehicles and to provide power in stationary and portable power applications because they are energy-efficient, quiet, and fuel-flexible. The feasibility of the hydrogen economy depends on issues of energy sourcing, including fossil fuel use, climate change, and sustainable energy generation. In this chapter hydrogen value chain from production to end-use are discussed highlighting the challenges for every aspect that need to be overcome for attaining a viable hydrogen-economy. Fig 1 shows the elements of the hydrogen value chain.
Transition to Hydrogen Economy
Storage
Applications
Safety Code & Standards
Transport & Delivery
Production
Hydrogen: Value Chain
HYDROGEN ECONOMY
FUELWOOD COAL
OIL
HYDROGEN
Figure 1: Various components of the hydrogen value-chain
Source: Ref [4] (Modified)
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Hydrogen is abundantly available and accounts for three-fourths of the mass of the universe. It is mostly found chemically bound to other elements and is not available in free form in nature. Hydrogen can be extracted from almost any energy source – natural gas, methanol, coal, biomass and water, with renewable source being the most preferred. In the coming years, the impact of global climate change, energy scarcity and the need for improved energy utilization efficiency will promote hydrogen-based technologies creating new areas of opportunities for hydrogen. The factors that make hydrogen an attractive fuel are [5]-
1. Highly abundant in nature 2. Lightest element of all the elements known 3. Versatile, converts easily to other energy forms at the user end 4. High utilization efficiency when used in fuel cell 5. Environmentally compatible (zero- or low- emission) 6. It works well with fuel cells
Hydrogen has the highest heat content per unit mass of all the conventional fuels and provides energy yield of 122 kJ/g (kilojoule per gram), which is 2.75 times greater than hydrocarbon fuels like petroleum and coal [6]. Hydrogen is more energy efficient than gasoline as liquid hydrogen stores approximately 2.6 times more energy per unit mass than gasoline. The chemical energy per unit mass of hydrogen (142kJ gˉ¹) is at least three times larger than that of other chemical fuels (for example, the equivalent value for liquid hydrocarbons is 47 kJ gˉ¹) [7]. Hydrogen has higher heat of combustion when compared to other fuels like petroleum, paraffin, graphite (coal), castor oil, wood, which makes it a promising fuel [8]. Hydrogen engines can be operated more effectively on excessively lean mixtures than gasoline engines as hydrogen has a wide range of flammability when compared with other fuels. Hydrogen has very low ignition energy (0.02J), high flame speed, and high diffusivity which make it a good and safe fuel. Table 1 compares the three fuels (hydrogen, methane and gasoline) on the basis of various properties. Table 1 Properties of Hydrogen vs. other conventional fuels
Property Hydrogen Methane Gasoline Molecular weight (g/mol) 2.016 16.04 ~110 Mass density (kg/Nm3) at P =1 atm = 0.101 MPa, T = 0ᵒC
0.09 0.72 720-780 (liquid)
Mass density of liquid H2 at 20 K (kg/Nm3) 70.9 - - Boiling point (K) 20.2 111.6 310-478 Higher heating value (MJ/kg) (assumes water is produced)
142.0 55.5 47.3
Lower heating value (MJ/kg) (assumes steam is produced)
120.0 50.0 44.0
Flammability limits (% volume) 4.0-75.0 5.3-15.0 1.0-7.6 Detonability limits (% volume) 18.3-59.0 6.3-13.5 1.1-3.3 Diffusion velocity in air (m/s) 2.0 0.51 0.17 Ignition energy (mJ) – At stoichiometric mixture – At lower flammability limit
0.02 10
0.29 20
0.24 n/a
Flame velocity in air (cm/s) 265-325 37-45 37-43 Toxicity Non toxic Non toxic Toxic above 50 ppm Source: Ref[2]
The high energy content and its abundance in nature makes hydrogen a promising fuel for the future. It can be produced from a variety of technologies but only some are considered to be feasible economically as well as environmentally. Hydrogen production is currently dominated by steam methane reforming but there is a need to generate hydrogen from renewable energy sources and at low costs for achieving a viable hydrogen economy.
3. Sources and methods for hydrogen production
Hydrogen can be produced from a variety of sources, both renewable (solar, wind, tidal, hydro and biomass etc) and non-renewable (coal, oil and methane). The different hydrogen production sources and methods include:
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3.1.1 Natural gas/methane via Steam Methane Reforming (SMR): In this process natural gas is reacted with steam in the presence of a catalyst to produce hydrogen and carbon dioxide. Currently, this is the most common method for hydrogen production and almost half of the global supply of hydrogen is produced by this method [9-12]. This method has certain drawbacks associated with it. One being environmental concerns related with CO2 emissions secondly natural gas is a non-renewable source and increase in its demand would lead to fast depletion of its reserves and uneven distribution of this resource could lead to geo-political tension and unstable supplies. 3.1.2 Coal via Gasification: It is also known as the partial oxidation process. Coal is reacted with oxygen in less than stoichiometric ratio, yielding a mixture of hydrogen and carbon monoxide at high temperatures of 1250-1300ᵒC. This is also one of the major methods for hydrogen production and the constraints of using this method are similar as using natural gas. 3.1.3 Partial Oxidation: Partial Oxidation (POX) of hydrocarbons and Catalytic Partial Oxidation (CPOX) of hydrocarbons have been proposed for use in hydrogen production for automobile fuel cells and some commercial applications. The non-catalytic partial oxidation of hydrocarbons in the presence of oxygen typically occurs with flame temperature of 1300-1500oC. Catalysts can be added to the partial oxidation system to lower the operating temperatures [13]. 3.1.4 Auto-thermal Reforming: Auto-thermal reforming adds steam to catalytic partial oxidation. It consists of a thermal zone where POX or CPOX is used to generate the heat needed to drive the downstream steam reformation reactions in a catalytic zone [13]. Table 2 provides a comparison of reformation processes for production of hydrogen [13]. Table 2 Comparison of reformation processes for production of hydrogen
Most extensive industrial experience Oxygen not required Lowest process temperature Best H2/CO ratio for H2
production
Highest air emissions
Auto-thermal Reforming
Lower process temperature than POX Low methane slip
Limited commercial experience Requires air or oxygen
Partial Oxidation
Decreased desulfurization requirement No catalyst required Low methane slip
Low H2/CO ratio Very high processing temperatures Soot formation/handling adds process complexity
Source: Ref [13]
3.2 Water Splitting:
Water splitting can be divided into different categories such as electrolysis, thermolysis, and photo electrolysis [13]. 3.2.1 Electrolysis: It involves the splitting of water into oxygen and hydrogen molecules using electricity. Hydrogen can be produced via electrolysis of water from any electrical source, including utility grid power, solar photovoltaic (PV), wind power, hydropower, or nuclear power. This method produces high purity hydrogen. 3.2.2 Thermolysis: Heat is used to decompose water into oxygen and hydrogen molecules 3.2.3 Photoelectrolysis: Uses sunlight directly to decompose water into hydrogen and oxygen, and uses semiconductor materials similar to those used in photovoltaics [13].
3.3 Biomass:
The most important biomass energy sources are wood and wood wastes, agricultural crops and their waste byproducts, municipal solid waste (MSW), animal wastes, waste from food processing and aquatic plants and algae [14]. The methods for producing hydrogen from biomass can be broadly divided into two main categories: thermochemical and
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biological. The advantages of using biomass for hydrogen production are: biomass is a renewable source and could be developed sustainably in future, secondly there is no net release of CO2 and very low sulfur emissions and thirdly it reduces dependence on fossil fuels [14]. Pyrolysis, gasification and super critical water extraction are thermochemical methods whereas biophotolysis and fermentation are biological routes. Research in biohydrogen has received considerable attention over the last several years because of substantial focus to sustainable development and waste minimization [14].
3.4 Nuclear Energy:
Hydrogen can be produced from nuclear energy via nuclear thermal conversion of water using various chemical processes such as the sodium-iodine cycle, electrolysis of water using nuclear power, and high-temperature electrolysis that additionally would use nuclear system waste heat to lower the electricity required for electrolysis [15]. The concerns with using nuclear energy are related to the mining and processing of uranium, the potential for accidents, and the management and disposal of radioactive waste [16]. Table 3 shows the annual hydrogen production share by different sources. Table 3 Annual hydrogen production share by different sources
Source Bcm ͣ/ yr Share (%) Natural Gas 240 48 Oil 150 30 Coal 90 18 Electrolysis 20 4 Total 500 100 ͣ Bcm: Billion cubic metres Source: Ref [17]
4. Challenges to Hydrogen Production
Reducing cost is the major overarching technical challenge. Emerging production technologies with the long-term prospective require focused technical and financial support to achieve their full potential.
• System Efficiency- To compete with hydrogen produced from conventional steam methane reforming, production technologies like electrolysis and thermo-chemical biomass conversion will require improvements in system efficiency and integration. For example, direct water splitting technologies, which are at their early stage, require breakthrough in materials development for attaining improved efficiency.
• High production cost- Though abundantly available in combined form, hydrogen suffers from some technological constraints to produce it in free form making it expensive. For example, high capital and electricity costs for electrolytic technology limits its use for hydrogen production.
• Environmental concerns- Currently, majority of hydrogen is being produced from non-renewables (natural gas, coal) which leads to further increase in CO2 concentrations. Therefore, the need of the hour is to produce hydrogen from renewable sources (solar, wind, tidal, hydro, biomass) to make it environmentally compatible.
5. Hydrogen Storage
Hydrogen storage is a key enabling technology for the advancement of hydrogen and fuel cell power technologies in transportation, stationary, and portable applications. Manufacturing covers a broad range of components and systems related to hydrogen production and delivery, fuel cells, and hydrogen storage. Significant challenges must be overcome to move from today's components and systems, built using laboratory-scale fabrication technologies, to high-volume commercially manufactured products. Hydrogen storage involves various methods as depicted in Figure 2.
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Figure 2: Flow Chart showing various hydrogen storage methods
5.1 Compression
Compression is one of the simplest ways to store hydrogen. Compressed hydrogen is stored in metallic cylinders or composite cylinders at pressure up to 70 MPa. Due to low energy density, hydrogen needs to be compressed at a very high pressure before filling into cylinders. This is done to maximize the tank capacities. About four times higher pressure is needed to meet the driving purpose, however, such industrial cylinders have not been commercially available. The hydrogen density as such is remarkably lower than the cryoadsorption method, and the high cost of compression and the cylinder might hinder the method to be accepted commercially compression of hydrogen the densely populated regions. However, this does not result to be an energy efficient method as compressing hydrogen results in 30% power usage of total output and also the high costs related with compression and cylinders. So this method is not appropriate for the commercial application. Nevertheless, this is the most preferred method for on-board storage of hydrogen in transport vehicles. Advances in compression technologies are also required to improve efficiencies and reduce the cost of producing high-pressure hydrogen. Issues with compressed hydrogen gas tanks revolve around high pressure, weight, volume, conformability and cost.
5.2 Liquefaction
The energy density of hydrogen can be improved by storing hydrogen in a liquid state. Liquefaction of gases is physical conversion of a gas into a liquid state. The reason why gases are converted into liquids is that the storage of these gases is more economic and versatile in their liquid form. Liquid hydrogen (LH2) tanks can store more hydrogen in a given volume than compressed gas tanks. The volumetric capacity of liquid hydrogen is 0.07 kg/L, compared to 0.030 kg/L for 10,000 psi gas tanks. The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressure and very low temperature. Gasification of liquid hydrogen inside the cryogenic vessel is an inevitable loss even with a perfect insulation technique. The theoretical process referred to as ideal liquefaction uses a reversible expansion to reduce the energy required for liquefaction. It consists of an isothermal compressor, followed by an isentropic expansion to cool the gas and produce a liquid. It is used as a theoretical basis for the amount of energy required for liquefaction, or ideal work of liquefaction, and is used to compare liquefaction processes. The challenges associated with this method are efficiency of the liquefaction process, boil-off of the liquid, the energy required for hydrogen liquefaction, volume, weight, and tank cost. The energy requirement for hydrogen liquefaction is high. Therefore, it is preferred to store liquid hydrogen in an open system as the pressure in a closed system becomes considerably high at room temperature. The boil-off of liquid results in the emission of H2 into the atmosphere. These two constraints i.e. relatively large amount of energy necessary for liquefaction and the continuous boil-off of liquid limits the commercial use of this storage system. New approaches that can lower these energy requirements and thus the cost of liquefaction are needed.
Hydrogen Storage
Gaseous and liquid storage
Compressed hydrogen gas tanks
Liquid hydrogen tanks
Materials-based hydrogen storage Absorption
Adsorption
Chemical reactionMetal Hydrides
Chemical hydrogen storage Hydrolysis reaction
Hydrogenation/ dehydrogenation reactions
New chemical approaches
Carbon-based materials, High surface area sorbents and new
materials and concepts
Materials and processes for energy: communicating current research and technological developments (A. Méndez-Vilas, Ed.)____________________________________________________________________________________________________
5.3.1 Absorption- Hydrogen is absorbed directly into the bulk of the material in this method. Absorption takes place by the incorporation of atomic hydrogen into interstitial sites in the crystallographic lattice structure in simple crystalline metal hydrides. 5.3.2 Adsorption- Based on the energetics of the adsorption mechanism, Physisorption and Chemisorption are the two ways by which hydrogen gets adsorbed onto a material. Sorptive processes typically require highly porous materials to maximize the surface area available for hydrogen sorption to occur, and to allow for easy uptake and release of hydrogen from the material. Physiosorption Physiosorption is the mechanism when materials adsorb the gases on their surface through some chemical bonding. Adsorption mechanism depends upon the geometry of the adsorbent and the temperature of adsorption. As the temperature increases, there is an exponential decrease of adsorption. Here, nanotechnology has a major role to play. When the pore sizes of the material varies in between 2 nm to 50 nm, capillary condensation takes place which leads to multilayer mechanism functions. Adsorption in a pore larger than 50 nm is the same as that on open surfaces. It has been observed that when the surface is completely covered with a layer of adsorbate, more gas molecules get adsorbed over the first layer due to the interaction between the same species of adsorbate molecules forming the second layer, and so on for the subsequent layers. Hydrogen storage in carbon materials occurs via physiosorption. The total storage capacity in a porous solid is, however, not only the adsorption capacity, but also the sum of contributions due to adsorption on solid surface and that due to compression in the void space [18]. Hydrogen storage in nanostructure carbons Major challenge today is to increase the storage capacity of hydrogen and thus an energy efficient method is to be found to solve the on-board hydrogen storage problem. The first report on hydrogen storage in carbon nano-tubes triggered a world-wide tide of research on carbon nanotubes [19, 20]. Nanostructures have very high hydrogen storage (wt %) and energy utilized for storage is also very low. They have very high aspect ratio i.e. large surface to volume ratio. This property of nano materials help them to absorb more onto their surfaces which results in higher storage of gases. The first report on hydrogen storage using nanostructures was in carbon nanotubes. Single walled carbon nanotubes have high hydrogen storage capacity. Even alkali metal nanoparticles have large surface area and therefore these can be used to store good wt% hydrogen on their surface for commercial applications. A metal-organic framework of Zn4O3 (1,4- benzenedicarboxylate) was proposed as hydrogen storage material [21], which might trigger another research tide on storing hydrogen in this group of compounds.
Chemisorption The chemical reaction route for hydrogen storage involves displacive chemical reactions for both hydrogen generation and hydrogen storage. For reactions that may be reversible on-board a vehicle, hydrogen generation and hydrogen storage take place by a simple reversal of the chemical reaction as a result of modest changes in the temperature and pressure. Sodium alanate-based complex metal hydrides are an example.
5.4 Metallic and Complex hydrides
The property of metals to absorb hydrogen and form hydrides (metallic hydrides and complex hydrides) makes them suitable for hydrogen storage. Some metals readily absorb gaseous hydrogen under conditions of pressure and moderate temperature to form metal hydrides. The reversible metallic hydrides are Intermetallic (alloy) types instead of singular metal. Since hydrogen is released from the hydride for use at low pressure, hydrides are the most intrinsically safe of all methods of storing hydrogen. Hydrogen is released from the alloy hydride when heat is applied. An alloy hydride tank is considered to be a very safe fuel system in the event of a collision because the loss of pressure in a punctured tank will cool down the metal hydride, which will then cease to release hydrogen. Though hydrides have good volumetric efficiency of hydrogen storage, they have poor gravimetric storage capacity. This results in weight penalty for hydrides [4]. Metal hydrides store hydrogen by chemically bonding the hydrogen to metal or metalloid elements and alloys [22]. Hydrides are unique because some can adsorb hydrogen at or below atmospheric pressure, then release the hydrogen at significantly higher pressures when heated—the higher the temperature, the higher the pressure. There is a wide operating range of temperatures and pressures for hydrides depending on the alloy chosen [22]. Each alloy has different performance characteristics, such as cycle life and heat of reaction. Hydrogen is stored in the form of so-called “metal hydride”. Most metals or alloys can react with hydrogen to form new compounds, which are named as metal hydrides. The formation of metal hydride is an exothermic process associated with heat releasing. With sufficient heat supply, hydrogen can be released from the as-formed metal hydride. Such a reversible reaction process can be expressed as follows:
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2/nM + H2 = 2/nMHn +ΔH Where: M-metal or alloy; MHn-metal hydride; ΔH-thermal effect associated with the reaction. Pressure and temperature changed, the reaction will take place alternatively and hydrogen will be absorbed or desorbed. Complex hydrides consist of elements mainly from Group I, II, and III, e.g. Li, Mg, B, Al, and form a variety of metal–hydrogen complexes. The number of hydrogen atoms per metal atom is 2 in many cases. These complexes show the highest volumetric density and the highest gravimetric density at room temperature but the low dynamics of hydrogen releasing process is a major problem. Hydrogen in complex hydrides is released via cascade decompositions, unlike metallic hydrides, and therefore the step reactions call for different conditions and hence there is a large difference between the theoretical and the practically attainable hydrogen capacities. NaAlH4, which can reversibly absorb/desorb hydrogen at moderate temperatures has received much attention [23, 24].
6. Storage Challenges
The key challenges include: • Weight, Volume and Cost- A major challenge for hydrogen utilisation is its on-board storage. For on-board
energy storage, vehicles need compact, light, safe and affordable containment but because of low density of hydrogen as compared to petrol this aspect still remains as a huge challenge. The weight, volume and cost of hydrogen storage systems are presently too high, resulting in inadequate vehicle range compared to conventional petroleum fueled vehicles.
• Efficiency- Energy efficiency remains a challenge for all hydrogen storage approaches. For example Byproduct regenerated in chemical hydride storage method decreases its life cycle energy efficiency and hence is a limitation. Advances in compression and liquefaction technologies are also required to improve efficiencies.
• Codes & Standards- Lack of proper codes and standards for hydrogen storage systems and interface technologies is a drawback in hydrogen storage.
7. Hydrogen Transport and Delivery
Hydrogen must be transported from the point of production to the point of use. It also must be safely compressed, stored and dispensed at refueling stations or stationary power facilities. Hydrogen transport and delivery need an infrastructure to deliver it from the point of production to dispensing point [25]. The transportation mode is mainly decided by the physical state of hydrogen (gaseous or liquid). The gaseous form of hydrogen is primarily transported over a network of pipelines. This pipeline system could be similar to the way natural gas is distributed. This requires the gas to be compressed to a very high pressure to maximize the tank capacity, but this becomes expensive to handle and transport. The compressed gas can also be transported by high pressure cylinders, tube trailers or cryogenic tankers. Hydrogen pipeline transport is used to transport hydrogen from the point of production or delivery to the point of demand. Pipelines, which are owned by hydrogen producers, are limited to small areas where large hydrogen refineries and chemical plants are concentrated. A large pipeline system dedicated to transporting large volumes of hydrogen does not yet exist. It commonly apply to extend range of 100-200 miles from production sites. Therefore pipeline transportation is considered to be one of the most cost effective method, but due to its limitation of delivery range, is not much efficient. Hydrogen has problems with both hydrogen embrittlement and corrosion. For this reason, hydrogen pipes have to resist corrosion. The problem is compounded because hydrogen can easily migrate into the crystal structure of most metals. For metal piping at pressures up to 7,000 psi (48 MPa), high-purity stainless steel piping with a maximum hardness of 80 HRB is preferred [26]. The different materials used for making composite pipes are: carbon fiber structure with fiberglass overlay, perfluoroalkoxy (PFA, MFA), polytetrafluoroethylene (PTFE) fluorinated ethylene propylene (FEP), carbon-fiber-reinforced polymers (FRP). The construction project of pipeline network building, not only covers the civil work to lay the pipeline and build the pump/compressor stations, but also covers all the work related to the installation of the field devices that will support remote operation. Various steps are involved such as Surveying of route, Clearing the route, Trenching - Main Route and Crossings (roads, rail, other pipes, etc.), Installing the pipe, Installing valves, intersections, etc., Covering the pipe and trench. Once construction is completed, the new pipeline is subjected to tests to ensure its structural integrity. These may include hydrostatic testing and line packing. The liquid form of hydrogen could be transported via many forms such as trucks, railcars or ships. This method could be expensive and difficult as it would take many tanker trucks of hydrogen to carry the equivalent of one gasoline tanker because hydrogen has a low density. But this becomes useful when the distance is upto 200 miles or less. Liquefaction is done by cooling a gas to form a liquid. To achieve the desired cooling in liquefaction processes a combination of compressors, heat exchangers, expansion engines, and throttle valves is used [27]. In this process, the gas is compressed at ambient pressure then cooled in a heat exchanger before passing through a throttle, producing some liquid. This liquid is removed and the cool gas is returned to the compressor via the heat exchanger. A major concern in liquid hydrogen storage is minimizing hydrogen losses from liquid boil-off. Because liquid hydrogen is
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stored as a cryogenic liquid that is at its boiling point, any heat transfer to the liquid causes some hydrogen to evaporate. Any evaporation will result in a net loss in system efficiency, because work went into liquefying the hydrogen, but there will be an even greater loss if the hydrogen is released to the atmosphere instead of being recovered. Cryogenic containers, or dewars, are designed to minimize conductive, convective, and radiant heat transfer from the outer container wall to the liquid. To eliminate heat transfer from convection and conduction, all cryogenic containers are equipped with doublewall construction and the space between the walls is evacuated. To prevent radiant heat transfer, multiple layers (30-100) of reflective, low-emittance heat shielding, usually aluminized plastic Mylar, are put between the inner and outer walls of the vessel. Cryogenic liquefaction allows hydrogen to be transported more efficiently over longer distances by truck, railcar, ship, or barge compared with using high-pressure tube trailers, although the liquefaction process is expensive. Transporting, storing, and delivering hydrogen to the point of end-use is more expensive than gasoline because it contains less energy per unit volume.
8. Challenges
• Infrastructure- Hydrogen transmission and distribution would require an entirely new infrastructure entailing huge cost input which further restricts its commercial use.
• Cost- Production and delivery systems will need to be integrated to minimize cost and take advantage of site-specific situations.
• Efficiency- Due to its relatively low volumetric energy density, transportation, storage and final delivery to the point of use can be one of the significant costs and energy inefficiencies associated with using hydrogen as an energy carrier.
9. End Use Applications
Hydrogen finds use in every part of man’s life be it industrial, domestic or space. Hydrogen may be used as fuel in almost any application where fossil fuels are used today—particularly for motorising the vehicles which would offer immediate benefits in terms of reduced pollution and cleaner environment [28]. The few are categorized as below- Hydrogen finds various industrial uses. It is used in petroleum refineries, oil and fat hydrogenation, in fertilizers production, in metallurgical industry. It is also used as a fuel primarily in aerospace industry. A mixture of hydrogen and oxygen has been used as a propellant for many years. It is also used as a fuel in automobiles. There are two possible routes for hydrogen application in vehicles. These are (a) direct use of hydrogen in IC engine leading to Internal Combustion Engine Vehicle (ICEV), and (b) indirect use of hydrogen through fuel cells where electricity is produced first, which then drives the vehicle through electric motors (FCV). One limiting factor of the hydrogen fuel cell vehicles is their current high cost which makes it difficult for consumers to afford them. Fuel cells can also be used for stationary power applications and in portable devices like laptops and camcorders [4]. According to Dupont, out of the total 500 Bm3 of hydrogen, ammonia production consumes 250 Bm3 followed by production of other chemical products which consume 65 Bm3, and petrochemistry consume 185 Bm3 of hydrogen, accounting for 50%, 13% and 37% respectively [2, 29]. In future, hydrogen from metal hydrides can be used for domestic power requirements, as a cooking fuel [8]. Keeping energy security and environment protection in mind the applications of hydrogen as an energy carrier can be broadly categorized into
• Vehicular Applications (hydrogen alone in either fuel cell vehicles or in IC engine based vehicles or as a blended fuel with CNG in IC engine based vehicles)
• Stationary Applications [Spark ignition engines using hydrogen and Compression ignition dual fuel (diesel and hydrogen) engines]
• Use in portable devices like laptops, camcorders
The table 4 shows the application of hydrogen, Internal Combustion(IC) and Fuel Cells
Materials and processes for energy: communicating current research and technological developments (A. Méndez-Vilas, Ed.)____________________________________________________________________________________________________
Table 4 Application of hydrogen, IC and fuel cells
Combustion Fuel cells
Vehicular applications Direct fuel in IC engines Blending with fossil fuels
Vehicular applications Fuel cell cars, buses etc
Stationary power generation Spark ignition engines using hydrogen Compression ignition dual fuel (diesel and hydrogen engines)
Stationary power generation (centralized or distributed/ on site)
Other emerging applications of hydrogen for cooking, heating etc.
Portable devices (Laptops, camcorders, phones, digital diaries, palmtops etc.)
Source: Ref [4] Table 5 gives advantages and disadvantages of Hydrogen Internal Combustion Engines (HICE) vehicles and fuel cell vehicles Table 5 Advantages and disadvantages of hydrogen internal combustion engines (HICE) vehicles and fuel cell vehicles
Vehicle Type
Advantages Disadvantages
Hydrogen Internal Combustion Engine Vehicles
Well-understood technology NOx control and after treatment required
Existing engine hardware/technology
Lower efficiency
Existing manufacturing facilities Thermal management Power density
Fuel Cell Vehicle
Substantial fuel economy benefit over HICE (and a smaller but still significant advantage over hybrid HICE)
Vehicle/power-train weight
Zero tailpipe emissions Vehicle/power-train cost Zero tailpipe emissions Thermal management Availability of power for electric systems and auxiliary units
Water management in cell
Possible government incentives for development
Precious metal supply/cost System life Servicing cost, complexity & infrastructure Operation in hot/cold climates Start up time Requirement for hybrid application (to achieve good transient response
Source: Ref [30]
10. Safety Codes and Standards
Safety Codes and Standards aims at standardizing and authenticating test procedures for safety and operational performance of hydrogen value chain. The lack of safety information on hydrogen components and systems and limited availability of uniform international codes and standards remains a fundamental challenge for the commercialization of hydrogen energy technologies. There is a need to harmonize codes and standards for hydrogen and fuel cells on an
Materials and processes for energy: communicating current research and technological developments (A. Méndez-Vilas, Ed.)____________________________________________________________________________________________________
international level which will be the basis for the economies of scale necessary to commercialize new and innovative hydrogen and fuel cell technology. International organizations like International Standards Organization (ISO) and International Electrotechnical Commission (IEC) have been working on the development of standards and codes relevant to use of hydrogen energy and fuel cells [4]. Regulations and codes for safe handling of hydrogen in India are governed by the rules published & administered by the Chief Controller of Explosives, Petroleum and Explosive Safety Organization (PESO), Nagpur. To enhance the safety in oil and gas industry in India, Oil Industry Safety Directorate (OISD) has formulated and coordinated implementation of a series of self-regulatory measures. Existing standards and codes need to be reviewed with the necessity of new ones to be developed, keeping in view the use of hydrogen by the common man and its storage in non-industrial areas.
11. Merits
Hydrogen has various merits over conventional fuels which make it a potential future fuel. It can be produced locally, centrally or onsite, from several sources, reducing dependence on petroleum imports. Producing hydrogen from renewable energy sources (solar, wind, tidal, hydro and biomass etc) makes it an environment-friendly fuel option. It is a clean fuel emitting no air pollutants or greenhouse gases when used in fuel cells and produces only nitrogen oxides (NOx) when burnt in ICEs. When combined with oxygen in a fuel cell it produces energy in the form of electricity which can be used to power vehicles, as a heat source and for many other uses [31].
12. Conclusion
To implement a successful "hydrogen economy" the technical and economic challenges need to be fully addressed. These include difficulties associated with hydrogen production, transportation, storage, safety, distribution and end use. Finding viable solutions to solve all of these problems could take some time but increasing oil costs, poor alternatives and improvements in technology offer promising future making hydrogen the most economical and feasible energy storage medium for all uses. Hydrogen use would require the alteration of industry and transport on a scale never seen before in history. However, it is believed that future oil costs, poor alternatives and improvements in technology may make the transition economically viable in the future. Hydrogen advocates promote hydrogen as a potential fuel for motive power (including cars and boats), the energy needs of buildings and portable electronics. The feasibility of a hydrogen economy depends on issues of energy sourcing, including fossil fuel use, climate change, and sustainable energy generation. Public awareness and capacity building are the key components, if hydrogen energy technologies are to be widely used by the common man in vehicles, homes and other places in India. Therefore, it is essential that from the early stages of development, the public is kept aware about the benefits of the technology. Further, it will be essential to develop institutional arrangements to impart education, training, maintaining database, coordination, and information dissemination and also to conduct research on different aspects of the technology.
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