Alternative fuels:
(a) Alcohols: These include methanol (methyl alcohol), ethanol (ethyl alcohol), propanol (propyl alcohol), butanol (butyl alcohol) as compounds
-The OH group which replaces one of the H atoms in an alkane, gives these compounds their characteristic properties
-Specific heating value is lower than gasoline (42 – 43 MJ/kg)
methanol (19.7 MJ/kg) and ethanol (26.8 MJ/kg)
-For air-fuel mixture SHV is comperable with gasoline (MJ/kg-mixture at stoichiometric mixtures)
-Other alcohol groups such as dihydric and trihydric alcohols are not used as a fuel in IC engines
(i) Methanol
-Can be obtained from natural gas – has near and long-term potential
-Has high octane quality (130 RON, 95 MON)
-Can be used in low-concentration (5-15 %) in gasoline to increase octane number of the mixture
Problems;
-Poor solubility in gasoline, toxicity, low energy content (about half of gasoline), high latent heat of vaporization and oxygen content
-Contribute to poor driveability, incompatibility with some metals
(ii) Ethanol
-Produced from biomass
-It is made from the sugars found in grains, such as: Corn, Sorghum, and Barley
Other sources of sugars to produce ethanol include: Potato skins, Rice, Sugar cane, Sugar beets, Yard clippings, Bark, Switch grass etc.
-Has high octane number – can be used in low–concentrations in gasoline
-Most of the ethanol used in the United States today is distilled from corn
-Scientists are working on cheaper ways to make ethanol by using all parts of plants and trees rather than just the grain.
-About 99% of the ethanol produced in the United States is used to make "E10" or "gasohol," a mixture of 10% ethanol and 90% gasoline.
-Any gasoline powered engine can use E10, but only specially made vehicles can run on E85, a fuel that is 85% ethanol and 15% gasoline
(b) Biodiesel:
-It is methyl or ethyl ester of a fatty acid produced from vegetable oil of edible or non edible types or animal fat or algae, by transesterification process using catalysts. -Has better lubricating properties and much higher cetane ratings than today's low sulfur diesel fuels. -Its addition reduces the fuel system wear. -Can be used in the pure form (B100), or may be blended with petroleum diesel in any concentration in most diesel engines for transportation purpose. -But, the engine may face problems, such as low temperature operation, less durability and drop in power. New diesel fuel injection systems, such as common rail systems are equipped with materials that are compatible with biodiesel (B100). -Biodiesel offers a substantial reduction in particulate matter (25%-50%) and a marginal increase of NOx (1%-6% when it is used as an alternative fuel in a CI engine. -The major problems associated with biodiesel are (i) poor oxidation stability, (ii) higher viscosity and density, (iii) lower calorific value, and (iv) cold flow property. -Blends of 20% and lower biodiesel can be used in diesel engines with no, or only minor modifications.
(c) Biogas:
-Produced by the anaerobic decomposition of organic materials such as cow dung and other waste such as cornhusks, leaves, straw, garbage, flesh of car cusses, poultry droppings, pig dung, human excreta, sewage and the plants specially grown for this purpose like water hyacinth, algae, certain types of grasses. Also any cellulosic organic material of animal or plant origin which is easily bio-degradable is a potential raw material for biogas production. -Also produced by pyrolysis and hydrogasification methods
-Contains a mixture of methane (50-60% vol), CO2 (30-45%), hydrogen (5-10%), nitrogen (0.5-7%) and small traces of other gases such as hydrogen sulphide and oxygen
-It is a clean, but slow burning gas and having value between 5000 to 5500 kcal/kg or 38131 kJ/m3
-The octane rating of biogas is 130 and ignition temperature is 650 °C
-Can be used to operate both compression ignition (diesel) and spark ignition (petrol) engines. CI engines can operate on dual-fuel (biogas+diesel) operation and pilot injection operation in which small quantity of diesel is required for igniting the mixture of air and biogas
-80% saving of diesel oil can be achieved
-Drawback of biogas is present of CO2. The engine performance can be improved by reducing the CO2 content in biogas.
(d) Hydrogen:
-Clean burning fuel and has the highest energy content per unit mass of any chemical fuels which can reduce the dependency on hydrocarbon based fuels
Production:
Most common method of producing hydrogen involves splitting water (H2O) into its component parts of hydrogen (H2) and oxygen (O). There are different methods to produce hydrogen-
i. Steam reformation or partial oxidation of hydrocarbons such as natural gas, naphtha or crude oil. It converts methane into hydrogen and carbon monoxide by reaction with steam over a nickel catalyst.
ii. Coal gasification- Hydrogen made from coal can probably be justified as a fuel for special applications where the unique characteristics of hydrogen can be put to advantage such as its weight or its non-polluting characteristics.
iii. Electrolysis- it uses electrical current to split water into hydrogen at the cathode (+) and oxygen at anode (-) [3].
iv. Thermo chemical method- it utilizes heat to achieve the chemical splitting of water to its elements without the need for intermediate electricity generation and without the need to use the extremity high temperature of 2500 °C or more.
v. Photo-electrolysis- it uses sunlight and catalysts to split water. In this method, a current is generated by exposing on or both electrodes to sunlight. Hydrogen and oxygen gases are liberated at the 2 electrodes by the decomposition of water. A catalyst may be included to facilitate the electrode process.
vi. Biological and photo-biological water splitting use sunlight and biological organisms to split water.
vii. Thermal water splitting uses a very high temperature (approximately 1000 °C) to split water.
viii. Biomass gasification uses selected microbes to break down a variety of biomass feed stocks into hydrogen.
(a) Alcohols: These include methanol (methyl alcohol), ethanol (ethyl alcohol), propanol (propyl alcohol), butanol (butyl alcohol) as compounds
-The OH group which replaces one of the H atoms in an alkane, gives these compounds their characteristic properties
-Specific heating value is lower than gasoline (42 – 43 MJ/kg)
methanol (19.7 MJ/kg) and ethanol (26.8 MJ/kg)
-For air-fuel mixture SHV is comperable with gasoline (MJ/kg-mixture at stoichiometric mixtures)
-Other alcohol groups such as dihydric and trihydric alcohols are not used as a fuel in IC engines
(i) Methanol
-Can be obtained from natural gas – has near and long-term potential
-Has high octane quality (130 RON, 95 MON)
-Can be used in low-concentration (5-15 %) in gasoline to increase octane number of the mixture
Problems;
-Poor solubility in gasoline, toxicity, low energy content (about half of gasoline), high latent heat of vaporization and oxygen content
-Contribute to poor driveability, incompatibility with some metals
(ii) Ethanol
-Produced from biomass
-It is made from the sugars found in grains, such as: Corn, Sorghum, and Barley
Other sources of sugars to produce ethanol include: Potato skins, Rice, Sugar cane, Sugar beets, Yard clippings, Bark, Switch grass etc.
-Has high octane number – can be used in low–concentrations in gasoline
-Most of the ethanol used in the United States today is distilled from corn
-Scientists are working on cheaper ways to make ethanol by using all parts of plants and trees rather than just the grain.
-About 99% of the ethanol produced in the United States is used to make "E10" or "gasohol," a mixture of 10% ethanol and 90% gasoline.
-Any gasoline powered engine can use E10, but only specially made vehicles can run on E85, a fuel that is 85% ethanol and 15% gasoline
(b) Biodiesel:
-It is methyl or ethyl ester of a fatty acid produced from vegetable oil of edible or non edible types or animal fat or algae, by transesterification process using catalysts. -Has better lubricating properties and much higher cetane ratings than today's low sulfur diesel fuels. -Its addition reduces the fuel system wear. -Can be used in the pure form (B100), or may be blended with petroleum diesel in any concentration in most diesel engines for transportation purpose. -But, the engine may face problems, such as low temperature operation, less durability and drop in power. New diesel fuel injection systems, such as common rail systems are equipped with materials that are compatible with biodiesel (B100). -Biodiesel offers a substantial reduction in particulate matter (25%-50%) and a marginal increase of NOx (1%-6% when it is used as an alternative fuel in a CI engine. -The major problems associated with biodiesel are (i) poor oxidation stability, (ii) higher viscosity and density, (iii) lower calorific value, and (iv) cold flow property. -Blends of 20% and lower biodiesel can be used in diesel engines with no, or only minor modifications.
(c) Biogas:
-Produced by the anaerobic decomposition of organic materials such as cow dung and other waste such as cornhusks, leaves, straw, garbage, flesh of car cusses, poultry droppings, pig dung, human excreta, sewage and the plants specially grown for this purpose like water hyacinth, algae, certain types of grasses. Also any cellulosic organic material of animal or plant origin which is easily bio-degradable is a potential raw material for biogas production. -Also produced by pyrolysis and hydrogasification methods
-Contains a mixture of methane (50-60% vol), CO2 (30-45%), hydrogen (5-10%), nitrogen (0.5-7%) and small traces of other gases such as hydrogen sulphide and oxygen
-It is a clean, but slow burning gas and having value between 5000 to 5500 kcal/kg or 38131 kJ/m3
-The octane rating of biogas is 130 and ignition temperature is 650 °C
-Can be used to operate both compression ignition (diesel) and spark ignition (petrol) engines. CI engines can operate on dual-fuel (biogas+diesel) operation and pilot injection operation in which small quantity of diesel is required for igniting the mixture of air and biogas
-80% saving of diesel oil can be achieved
-Drawback of biogas is present of CO2. The engine performance can be improved by reducing the CO2 content in biogas.
(d) Hydrogen:
-Clean burning fuel and has the highest energy content per unit mass of any chemical fuels which can reduce the dependency on hydrocarbon based fuels
Production:
Most common method of producing hydrogen involves splitting water (H2O) into its component parts of hydrogen (H2) and oxygen (O). There are different methods to produce hydrogen-
i. Steam reformation or partial oxidation of hydrocarbons such as natural gas, naphtha or crude oil. It converts methane into hydrogen and carbon monoxide by reaction with steam over a nickel catalyst.
ii. Coal gasification- Hydrogen made from coal can probably be justified as a fuel for special applications where the unique characteristics of hydrogen can be put to advantage such as its weight or its non-polluting characteristics.
iii. Electrolysis- it uses electrical current to split water into hydrogen at the cathode (+) and oxygen at anode (-) [3].
iv. Thermo chemical method- it utilizes heat to achieve the chemical splitting of water to its elements without the need for intermediate electricity generation and without the need to use the extremity high temperature of 2500 °C or more.
v. Photo-electrolysis- it uses sunlight and catalysts to split water. In this method, a current is generated by exposing on or both electrodes to sunlight. Hydrogen and oxygen gases are liberated at the 2 electrodes by the decomposition of water. A catalyst may be included to facilitate the electrode process.
vi. Biological and photo-biological water splitting use sunlight and biological organisms to split water.
vii. Thermal water splitting uses a very high temperature (approximately 1000 °C) to split water.
viii. Biomass gasification uses selected microbes to break down a variety of biomass feed stocks into hydrogen.
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