Environment-friendly Hydrogen gas as fuel in fuel cell and its challenges:

Environment-friendly Hydrogen gas as fuel in fuel cell and its challenges:

Hydrogen is the simplest and lightest element. Storage is one of the greatest problems for hydrogen. It leaks very easily from container meant for storage, no mater how strong and no matter how well insulated. Therefore, hydrogen in storage tanks always evaporates, at a rate of at least 1.7 percent per day.

Another important property of hydrogen is it is very reactive in nature. When hydrogen gas comes into contact with metal surfaces it decomposes into hydrogen atoms, which are so very small that they can penetrate metal. This causes structural changes that make the metal brittle.

One of the largest problems perhaps hydrogen fuel cell transportation has is its fuel tank size. In gaseous form of hydrogen, a volume of 238,000 litres gas is necessary to replace the same energy capacity of 20 gallons of petrol (gasoline). One option is to compress the gas. Because of gas’s low density property, compressed gas does not give a car as useful a as of gasoline as far as storage volume is concerned. Moreover, a compressed hydrogen fuel tank would be at risk of developing pressure leaks either through accidents or through normal wear and such leaks could result in dangerous explosions.

In case, the hydrogen is liquefied, the liquid hydrogen would give a density of 0.07 grams per cubic centimeter. In that case, it may require almost the four times volume of gasoline for a given amount of energy release. Besides, there are many difficulties in storing liquid hydrogen. Liquid hydrogen is cold enough to freeze air. Accidents may occur from pressure build-ups resulting from plugged valves. Besides, energy costs of liquefying the gas and refrigerating it also to be considered while calculating economy.

Other option may be considered is the use of powdered metals to store the hydrogen in the form of metal hydrides. The volume of stored metal hydrides would be little more than that of the metals themselves; but storing in this form, hydrogen would be far less reactive. However, the weight of the metals will make the storage tank very heavy.

As far as production of hydrogen is concerned, hydrogen does not freely occur in nature in useful quantities. Therefore hydrogen must be split from molecules, either molecules of methane derived from fossil fuels or from water. Currently, most hydrogen is produced by the treatment of methane with steam (the equation is CH4 (g) + H2O + e > 3H2(g) + CO(g)). The CO(g) in this equation is carbon monoxide gas, which is a byproduct of the reaction. Again the production of CO, which converts into CO2 is a greenhouse gas – not environment friendly option. Again, at present we do not have viable technology to obtain hydrogen from water, other than electrolysis – which is not energy saving option.

Therefore, as of now, it is a challenge before us to use hydrogen economically, efficiently and environment-friendly way. As lot research activities are going on in this field, very soon positive favorable result could be seen.

Principle of Hydrogen fuel cell:

The hydrogen fuel cell is an electrochemical energy conversion device. Hydrogen and oxygen are fed into opposite sides of a cell, which are separated by a membrane permeable to hydrogen ions but not electrons. Hydrogen gas molecules entering the anode side of the cell are ionized in the presence of a catalyst to form protons and electrons. The protons pass through the membrane to combine with the oxygen and electrons to produce water at the cathode. The electrons flow through an external circuit from the anode to the cathode, creating an electrical current, which powers an electric load such as a motor.

Options of various alternative fuels for motor vehicles:

Options of various alternative fuels for motor vehicles:

We discuss below various other fuels that can be used as alternative to fossil fuel for motor vehicles; some of the fuels discussed are renewable:

(a) Bio-diesel: Motor vehicles can be very efficiently run by bio-diesel. Internal combustion engines are common in motor vehicles and are traditionally fuelled by diesel derived from fossil fuels. Thankfully diesel is a compound which can be replaced with bio-diesel which is an organically based product and is renewable. It is relatively easily produced from plant and animal oils, fats and greases. Environmentally, bio-diesel run vehicles also gives benefits in reduction of pollution.

(b) Liquefied Petroleum Gas (LPG): LPG is an alternative to petrol (gasoline), it offers lower local pollution levels than normal fuels. This fuel is compatible with petrol and many vehicles can run on either (dual-fuel vehicles); so the limited distribution of LPG is not a problem. Its main claims to fame are its reduced local pollution and it is also cheaper to run. Unfortunately, it is not renewable as it is petroleum based product and does not qualify for tackling climate change.

(c) Liquefied Natural Gas (LNG) and Compressed Natural Gas (CNG): In practice, LNG and CNG are replacements for petrol / diesel and suitable for heavier freight vehicles. Natural gas is intrinsically cleaner than petrol / diesel, but since it is a fossil fuel it is not renewable. It also contributes to global warming. At a local level it produces much less pollution than petrol or diesel and its use attracts financial incentives. The fuel tanks are specially designed for intense refrigeration (LNG) or high pressure (CNG) which makes them larger and heavier.

(d) Ethanol and Methanol: Can be used as alternatives or complements to petrol (gasoline) and can give less local pollution. If the raw source is petroleum then they are not renewable. Fortunately, they can be produced organically; e.g. from sugar cane etc., and then they can contribute in reducing climate change. Producing these alcohols organically can also bring economic benefits to rural developments by way of benefiting farmers.

(e) Hydrogen Fuel Cells: Fuel cells are not, strictly speaking, renewable or alternative energy, they are engines which convert energy; the energy source is actually hydrogen. Potentially this system can give clean and efficient energy. This technology is complex and research and development is needed to make them more feasible. The hydrogen fuel can be derived from a variety of sources. The hydrogen fuel cell is an electrochemical energy conversion device. Hydrogen and oxygen are fed into opposite sides of a cell, which are separated by a membrane permeable to hydrogen ions but not electrons. Hydrogen gas molecules entering the anode side of the cell are ionized in the presence of a catalyst to form protons and electrons. The protons pass through the membrane to combine with the oxygen and electrons to produce water at the cathode. The electrons flow through an external circuit from the anode to the cathode, creating an electrical current, which powers an electric load such as a motor. If the source of energy is renewable then we have a desirable situation but if it is petroleum derived, for example, and then it is not a renewable system. There are developments which indicate that fuel cells may provide an important source of energy in transport applications.

(f) Hybrid engine systems: This system uses internal combustion engines in tandem with battery-driven electric motors, to conserve energy. A few cars are now in production with this system. The batteries are charged from the kinetic energy of the vehicle (e.g., when braking). Manufacturers use Nickel-metal Hydride batteries (designed, it is claimed, to last as long as the car) and these are charged by the petrol power unit (via an alternator) during normal driving. Power is delivered to the wheels by either unit or both depending on the demands such as acceleration, during cruising or braking. Currently the vehicles are dearer, and this system only mitigates the problem of carbon emissions. It does not solve the emission problem. Nevertheless, the energy that is regenerated is truly green. One advantage of the electric system over the petrol engine is the torque available over a wide speed range; a normal car has several gears to narrow the speed range in use.

Benefits and shortcomings of Battery operated Electric Motor Vehicles:

Benefits and shortcomings of Battery operated Electric Motor Vehicles (EMV):

(A) Benefits of Battery operated electric motor vehicles are:

(i) Electric vehicles run on electricity generated from batteries do not emit air pollutants. Therefore, these vehicles are termed ‘zero emission vehicles’.

(ii) Within city, since most people drive vehicles less than 40 miles per day, electric cars are certainly practical for moving within a city.

(iii) Fossil fuel use in internal combustion engines give rise to various environmental problems and these problems may be solved by using battery operated electric vehicles.

(iv) Electric cars are more efficient than petrol / diesel driven vehicles in terms of performance per unit amount of money and yield better air quality.

(v) Decreased fuel costs for battery operated electric vehicles make them more cost-effective in the long run.

(vi) An electric car of today would only get better over time; as in near future the performance, cost and efficiency of batteries available would be much better.

(vii) In most of the case, driving an electric car is more smother and people feel very similar or better to driving a gasoline car.

(viii) Without the internal combustion engine, electric cars have the potential to be quieter and noise pollution is much less.

(ix) As the number of electric vehicle increases, number of recharging station will be more and drivers will be able to recharge their cars by plugging them in overnight to a recharging outlet or at home.

(x) Lot of research is going on for improving the battery size, battery life and recharging time for batteries; and in near future rapid developments could be seen in this respect.

(B) There are few shortcomings of electrically driven motor vehicles, which are mostly of battery related:

(i) While electric cars themselves are clean, but generating electricity to charge vehicle batteries produces air pollution and solid waste.

(ii) Potential health or safety risks associated with widespread use of electric vehicles have not yet been fully evaluated.

(iii) Many vehicle batteries contain toxic elements or produce toxic emissions which could make battery production, transport, use, and disposal a significant solid waste risks. We should try to use environment-friendly batteries.

(iv) People must consider how safely to dispose of or recycle these batteries. As current batteries are large and heavy, battery occupies large space leaving less room for cargo and passengers.

Factors to be considered for development of alternative fuel systems for motor vehicles:

Factors to be considered for development of alternative & renewable fuel systems for motor vehicles:

It is known facts that, motor vehicle contribute adversely towards environment and causes significantly to increase greenhouse gasses. This picture is continuing alarmingly gloomier by the rise of petrol, diesel and kerosene vehicles. Not only do vehicles contribute net carbon gases, mainly CO and CO2, into the atmosphere which contribute to global warming and climate change but the products of combustion also produce additional local pollution causing many physical problems. Besides, the emission of nitrogen oxides, sulfur and carbon particulates (soot) can be very detrimental to health.

We now intend to discuss some imminent developments in running motor vehicles using renewable fuels / systems: We know that, fossil oil and gas are hidden treasures found in the earth crust. Therefore, these fuels are intrinsically cheap, requiring only the costs of finding and extraction from ground. There are three other features that make petroleum based fossil fuels such as petrol, diesel and kerosene uniquely attractive – (a) their very high energy densities, (b) the speed of recharging and (c) the existing world-wide distribution network.

(a) Energy densities are of prime important factor in choosing a particular system of energy-source in motor vehicles. To understand the system, let's take few alternatives of new clean energy sources: (i) rechargeable electric batteries of lead-acid based; (ii) Lithium batteries; (iii) hydrogen gas and Fuel Cells (batteries energized by some form of hydrogen).

(i) Rechargeable batteries are relatively expensive and heavy (due to their low energy densities). Therefore, currently, they are not at all practicable in most of the cases. If we take a comparison between the energy stored per unit weight of petrol and lead-acid batteries the ratio would be about 500:1; even with nickel-metal hydride batteries (another possible contender), the ratio approaches 300:1.

(ii) Lithium batteries are emerging as a practical solution for commercial energy storage device for use in motor vehicles. It has an energy density some 30% to 60% higher than Nickel-Metal hydride, but the supply of Lithium batteries can make the system uneconomic.

(iii) Pure Hydrogen would be ideal, if it is derived in a sustainable way. Unfortunately, this is a gas we would be dealing with and so by definition it has a very low density. Extreme compression or cryogenic temperatures are needed to overcome this problem which poses lot of technological problems to be dealt with, and also the safety aspects. Fuel Cell technology is based on hydrogen, but experts say, liquid compounds containing hydrogen can be used instead of pure hydrogen. Such a system can, theoretically, match energy densities to those of the conventional combustion engine. Again, if using hydrogen means using petroleum compounds then its main advantage is lost.

(b) Speed of recharging is again a very important factor in selecting alternatives. The comparisons regarding speed of charging can be made very easily. How much time does a system take to recharge the vehicle in question in comparison to the time to fill the tank with petrol?

(c) A distribution network of conventional oil-based fuels is established world-wide as far the present system is concerned. For any alternative fuels it might take a longer time to build up such infrastructure for distribution.

Pollution from Motor vehicles and its control measures:

Pollution from Motor vehicles and its control measures:

Pollution from motor vehicle is the single largest source of air pollution emissions. Motor vehicle exhaust is a complex mixture, composition of which depends on fuel used, and type and operating condition of the engine – whether it uses any pollution control devices.

At present, motor fuels consists of Petrol, Diesel, LPG (mostly Butane) and CNG. In recent times, people have been very much successful in reducing motor vehicle pollutants; but due to enormous growth in population of vehicles on urban roads, the effectiveness of the new technology in reducing pollution is not very much relevant and practicable. Over the year, engine efficiency has also gradually improved with progress in Electronic ignition, Fuel injection systems and Electronic control unit; and so, the emission standards. The major constituents of motor vehicle pollutants are 74% Carbon monoxide (CO), 16% hydrocarbon (hc), 8.5% nitrogen oxides (NOx), 0.8% particulate matter and 0.6% sulfur oxide (SOx).

Carbon monoxide (CO): a product of incomplete combustion. Carbon monoxide reduces the human blood's ability to carry oxygen and is dangerous to people with heart diseases.

Carbon dioxide (CO2): It is well known that, carbon dioxide has very prominent role in global warming as a greenhouse gas.

Hydrocarbons (HC): This is generated due to unburned or partially burned fuel and is a major contributor to urban toxic smog. They may cause lunge, liver damage and cancer to human being.

Nitrogen oxides (NOx): These are generated when nitrogen in the air reacts with oxygen under the high temperature and pressure conditions inside the engine. NOx emissions contribute to both smog and acid rain.

Sulfur oxides (SOx): Produced by combustion of petrol or diesel.

Evaporative emissions: These are produced from the evaporation of fuel, and are largely contributor to urban smog, as these heavier molecules stay closer to ground level.

Thus, Motor vehicles contribute significantly to greenhouse gases but nevertheless the rise and rise of petrol, diesel and kerosene vehicles continues at an alarming rate. Experts say, if all vehicles were tuned correctly there would be up to:

(a) 16 per cent less tailpipe hydrocarbon emissions;

(b) 26 per cent less tailpipe carbon monoxide emissions;

(c) 9 per cent less nitrogen oxides emissions.

The expert study also revealed that, on an average, maintenance to polluting vehicles does not require the replacement of major or expensive parts. Tuning is mainly limited to the following: (a) replacing points and air filter; (b) replacing fuel filter (if necessary); (c) replacing oil and oil filter; (d) checking spark plug condition and gap—adjusting or replacing as necessary; (e) checking distributor condition and operation and adjusting as necessary; (f) checking and adjusting idle mix and speed; (g) checking and replacing spark plug and distributor leads as necessary; (h) checking and replacing hoses and other minor items in fuel/electrical/emission control system as necessary; (i) examining vehicle diagnostics and replacing faulty components.

Additional technologically advanced incorporated emission control systems may be used, such as: (i) Emissions control systems for engines using diesel, ultra-low sulfur diesel, bio-diesel, natural gas, or propane fuels; (ii) Selective Catalytic Reduction (SCR) technology to reduce NOx with the SCR Catalyst – mostly for stationary IC engines; (iii) Catalyzed diesel particulate filters to reduce Particulate Matters, CO and HC from diesel engines; (iv) Oxidation catalysts to reduce CO and HC emissions; (v) Three-way catalysts to reduce NOx , CO and HC emissions.

Engine Technology Emissions reductions can be achieved by improving engine technology or using alternative fuels or reformulated gasoline. Among engine improvements, the catalytic converter, which extracts pollution from exhaust, has made the largest contribution to reduce vehicles emissions in recent years. A catalytic converter does not operate effectively, however, until it reaches its operating temperature after a car has been running for a few minutes. High sulfur content in fuel has been shown to reduce the effectiveness of the catalytic converter. To reduce these emissions, a low sulfur fuel has been introduced by many Govt. Authorities. Researchers are exploring ways to reduce the time needed to heat the catalytic converter.

Global warming and greenhouse gasses:

Global warming and greenhouse gasses:

The earth is surrounded by a cover of gasses as atmosphere. This atmosphere allows most of the light to pass through, which reaches the surface of earth. This light from sun is absorbed by the earth surface and converts into heat energy. This heat energy is re-emitted by the surface of the earth during night. Due excessive presence of some gasses in the atmosphere, this escape of heat from earth surface is prevented, resulting in heating of earth called ‘global warming’. The gasses which are responsible for causing global warming are called ‘greenhouse gasses’.

The harmful effects of presence of greenhouse gasses in atmosphere are global warming, climate change, ozone depletion, sea level rise, adverse effects on biodiversity etc. One way or another these adverse impacts are all directly or directly related to the presence of greenhouse gases in the atmosphere. A number of human activities, processes and consumptions produce waste gasses or greenhouse gasses that are harmful to the environment. They include:

(a) Fuel combustion
(b) Energy industries
(c) Manufacturing industries and construction
(d) Vehicle Transport and automobiles
(e) Fugitive emissions from fuels
(f) Burning of solid fuels
(g) Use of oil and natural gas
(h) Mineral products
(i) Chemical industry
(j) Metal production
(k) Production of halocarbons and sulfur hexafluoride
(l) Consumption of halocarbons and sulfur hexafluoride
(m) Solvent and other product use
(n) Enteric fermentation
(o) Manure management
(p) Rice cultivation
(q) Agricultural soils
( r) Prescribed burning of savannas
(s) Field burning of agricultural residues
(t) Solid waste disposal on land
(u) Wastewater handling
(v) Waste incineration

Much of these harmful gases are produced either naturally or by various human activities; which we should reduce. Brief description and effects of six important greenhouse gases are given below:

Carbon dioxide (CO2) - A naturally occurring gas produced by living organisms and fermentation. It is a normal component of the breath we exhale; it is hazardous in concentrated volumes. Large quantity of carbon dioxide is produced by the combustion of carbonaceous fuels. Carbon dioxide emissions from fuel burning, responsible for about 87 percent of global warming, have increased by about 27 percent since the industrial revolution.

Nitrogen oxides (NOx) – Nitrogen oxides are naturally occurring from microbial action in soil. NOx is also produced by fuel burning. Scientists say its production is increased by the use of nitrogen based fertilizers in agriculture, as well as by the use of catalytic converters in automobiles.

Methane (CH4) – Methane is a naturally occurring, in-flammable gas. Methane is produced by geological coal formations and by the decomposition of organic matters. Leading man-related sources of methane are landfills; livestock digestive processes and waste, especially ruminants (cud-chewing animals); and wetland rice cultivation.

Hydroflurocarbon gasses (HFCs) - Chlorofluorocarbons (CFC), the coolant, cleaning, and propellant gases were blacklisted internationally due to its ozone-eating characteristics. HFCs do contribute to global warming. Global warming potential of HFCs is 4,000 to 10,000 times that of CO2.

Perfluorocarbons (PFC), or perflurocompounds - Man-made replacement gases for CFCs but result also as a by-product of aluminium smelting. PFCs also used as a purging agent for semi-conductor manufacture and small amounts are produced during uranium enrichment processes. Global warming potential of Perfluorocarbons (PFC), or perflurocompounds is 6,000 to 10,000 that of CO2.

Sulfur hexafluoride (SF6) - Very low atmospheric concentration makes it an ideal test gas for gas concentration monitors. Principle uses: insulating material for high-voltage equipment like circuit breakers at utilities. Also used in water leak detection for cable cooling systems. SF6 is a man-made gas.

Environmental impact of mixed fertilizer plant:

Environmental impact of mixed fertilizer plant:

Mixed fertilizers contain two or more of the elements of nitrogen, phosphorus, and potassium (NPK), which are essential for good plant growth and high yields.

Ammonium phosphates are produced by mixing phosphoric acid and anhydrous ammonia in a reactor to produce slurry. This is the mixed-acid route for producing NPK fertilizers; potassium and other salts are added during the process. The principal pollutants from the production of Monoammonium phosphate (MAP) and Diammonium phosphate (DAP) are ammonia and fluorides. Fluorides and dust are released from materials-handling operations.

Control measures:

(i) Materials handling and milling of phosphate rock should be carried out in closed buildings. Fugitive emissions can be controlled by with capture of the dust in fabric filiters.

(ii) In the ammonium phosphate plant, the gas streams from the reactor, granulator, dryer, and cooler should be passed through cyclones and scrubbers, using phosphoric acid as the scrubbing liquid, to recover particulates, ammonia, and other materials for recycling.

(iii) In the nitrophosphate plant, nitrogen oxide (NOx) emissions should be avoided by adding urea to the digestion stage.

(iv) Fluoride emissions should be prevented by scrubbing the gases with water.

(v) Ammonia should be removed by scrubbing. Phosphoric acid may be used for scrubbing where the ammonia load is high.

(vi) The process-water system should be balanced, if necessary, by the use of holding tanks to avoid the discharge of an effluent.

The key production and control practices that leads to compliance with emissions requirements are:

• Maximize product recovery and minimize air emissions by appropriate maintenance and operation of scrubbers and baghouses.

• Eliminate effluent discharges by operating a balanced process water system.

• Prepare and implement an emergency preparedness and response plan. Such a plan is required because of the large quantities of ammonia and other hazardous materials stored and handled on site.