biomass has always been an important energy source

Biomass has been one of the main energy sources for the mankind ever since the dawn of civilisation, although its importance dwindled after the expansion in use of oil and coal in the late 19th century. There has been a resurgence of interest in the recent years in biomass energy in many countries considering the benefits it offers. It is renewable, widely available, and carbon-neutral and has the potential to provide significant productive employment in the rural areas. Biomass is also capable of providing firm energy. Estimates have indicated that 15% - 50% of the world?s primary energy use could come from biomass by the year 2050. Currently, about 11% of the world?s primary energy is estimated to be met with biomass.

For India, biomass has always been an important energy source. Although the energy scenario in India today indicates a growing dependence on the conventional forms of energy, about 32% of the total primary energy use in the country is still derived from biomass and more than 70% of the country?s population depends upon it for its energy needs.

India produces a huge quantity of biomass material in its agricultural, agro-industrial and forestry operations. According to some estimates, over 500 million tonnes of agricultural and agro-industrial residue alone is generated every year. This quantity, in terms of heat content, is equivalent to about 175 million tonnes of oil. A portion of these materials is used for fodder and fuel in the rural economy. However, studies have indicated that at least 150-200 million tonnes of this biomass material does not find much productive use, and can be made available for alternative uses at an economical cost. These materials include a variety of husks and straws. This quantity of biomass is sufficient to generate 15 000-25 000 MW of electrical power at typically prevalent plant

Biomass Gasification

Biomass gasification is the process through which solid biomass material is subjected to partial combustion in the presence of a limited supply of air. In what is known as a gasifier, solid fuel is convertedm by a series of thermo-chemical processes like drying, pyrolysis, oxidation, and reduction to a gaseous fuel called producer gas. The ultimate product is a combustible gas mixture known as ?producer gas?. If atmospheric air is used as the gasification agent, which is the normal practice, the producer gas consists mainly of carbon monoxide, hydrogen, and nitrogen. A typical composition of the gas obtained from wood gasification, on volumetric basis, is as follows:

Carbon monoxide 18 ? 22%

Hydrogen 13 ? 19%

Methane 1 ? 5%

Heavier hydrocarbons 0.2 ? 0.4%

Heavier hydrocarbons 9 ? 12%

Water vapour 4%

The calorific value of this gas is about 1000 ? 1200 kcal.Nm3.

Biomass gasifier based systems

The major applications of a producer gas produced from a biomass gasifier are as follows .

i) Mechanical shaft power applications, i.e., water pumping for irrigation/drinking and grinding, where the gas is used as fuel for internalcombustion engine running on dual fuel or 100% producer gas mode.

ii) Direct heat applications where it is burnt directly in a boiler, furnace or kiln, burner for institutional cooking, etc., to provide heat.

iii) Electricity generation through shaft power application viz., (engine coupled to an alternator/generator set).
From http://www.indiaenergyportal.org/subthemes_link.php?text=biomass&themeid=5

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Energy transformation

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Energy transformation or energy conversion is the process of changing one form of energy to another. In physics, the term energy describes the capacity to produce certain changes within a system, without regard to limitations in transformation imposed. Changes in total energy of systems can only be accomplished by adding or removing energy from them, as energy is a quantity which is conserved (unchanging), as stated by the first law of thermodynamics. Mass-energy equivalence, which arose from special relativity, says that changes in the energy of systems will also coincide with changes (often small in practice) in the system's mass, and the mass of a system is a measure of its energy content.

Energy in many of its forms may be used in natural processes, or to provide some service to society such as heating, refrigeration, light, or performing mechanical work to operate machines. For example, an internal combustion engine converts the potential chemical energy in gasoline and oxygen into thermal energy which, by causing pressure and performing work on the pistons, is transformed into the mechanical energy that accelerates the vehicle (increasing its kinetic energy). A solar cell converts the radiant energy of sunlight into electrical energy that can then be used to light a bulb or power a computer.

The generic name for a device which converts energy from one form to another, is a transducer.

Conversions to thermal energy (thus raising the temperature) from other forms of energy, may occur with essentially 100% efficiency[citation needed] (many types of friction do this). Conversion among non-thermal forms of energy may occur with fairly high efficiency, though there is always some energy dissipated thermally due to friction and similar processes. Sometimes the efficiency is close to 100%, such as when potential energy is converted to kinetic energy as an object falls in vacuum, or when an object orbits nearer or farther from another object, in space.

On the other hand, conversion of thermal energy to other forms, thus reducing the temperature of a system, has strict limitations, often keeping its efficiency much less than 100% (even when energy is not allowed to escape from the system). This is because thermal energy has already been partly spread out among many available states of a collection of microscopic particles constituting the system, which can have enormous numbers of possible combinations of momentum and position (these combinations are said to form a phase space). In such circumstances, a measure called entropy, or evening-out of energy distributions, dictates that future states of an isolated system must be of at least equal evenness in energy distribution. In other words, there is no way to concentrate energy without spreading out energy somewhere else.

Thermal energy in equilibrium at a given temperature already represents the maximal evening-out of energy between all possible states. Such energy is sometimes considered "degraded energy," because it is not entirely convertible a "useful" form, i.e. one that can do more than just affect temperature. The second law of thermodynamics is a way of stating that, for this reason, thermal energy in a system may be converted to other kinds of energy with efficiencies approaching 100%, only if the entropy (even-ness or disorder) of the universe is increased by other means, to compensate for the decrease in entropy associated with the disappearance of the thermal energy and its entropy content. Otherwise, only a part of thermal energy may be converted to other kinds of energy (and thus, useful work), since the remainder of the heat must be reserved to be transferred to a thermal reservoir at a lower temperature, in such a way that the increase in Entropy for this process more than compensates for the entropy decrease associated with transformation of the rest of the heat into other types of energy

History of energy transformation from the early universe[edit]
Energy transformations in the universe over time are (generally) characterized by various kinds of energy which has been available since the Big Bang, later being "released" (that is, transformed to more active types of energy such as kinetic or radiant energy), when a triggering mechanism is available to do it. A direct transformation of energy occurs when hydrogen produced in the big bang collects into structures such as planets, in a process during which part of the gravitational potential is to be converted directly into heat. In Jupiter, Saturn, and Neptune, for example, such heat from continued collapse of the planets' large gas atmospheres continues to drive most of the planets' weather systems, with atmospheric bands, winds, and powerful storms which are only partly powered by sunlight, however, on Uranus, little of this process occurs.

Familiar examples of other such processes transforming energy from the Big Bang include nuclear decay, in which energy is released which was originally "stored" in heavy isotopes, such as uranium and thorium. This energy was stored at the time of these elements' nucleosynthesis, a process which ultimately uses the gravitational potential energy released from the gravitational collapse of type IIa supernovae, to store energy in the creation of these heavy elements before they were incorporated into the solar system and the Earth. Such energy locked into uranium is triggered for sudden-release in nuclear fission bombs, and similar stored energies in atomic nuclei are released spontaneously, during most types of radioactive decay. In such processes, heat from decay of these atoms of radioisotope in the core of the Earth is transformed immediately to heat. This heat in turn may lift mountains, via plate tectonics and orogenesis. This slow lifting of terrain thus represents a kind of gravitational potential energy storage of the heat energy. The stored potential energy may be released to active kinetic energy in landslides, after a triggering event. Earthquakes also release stored elastic potential energy in rocks, a kind of mechanical potential energy which has been produced ultimately from the same radioactive heat sources. Thus, according to present understanding, familiar events such as landslides and earthquakes release energy which has been stored as potential energy in the Earth's gravitational field, or elastic strain (mechanical potential energy) in rocks. Prior to this, the energy represented by these events had been stored in heavy atoms, ever since the time that gravitational potentials transforming energy in the collapse of long-destroyed stars created these atoms, and in doing so, stored the energy within.

In other similar chain of transformations beginning at the dawn of the universe, nuclear fusion of hydrogen in the Sun releases another store of potential energy which was created at the time of the Big Bang. At that time, according to theory, space expanded and the universe cooled too rapidly for hydrogen to completely fuse into heavier elements. This resulted in hydrogen representing a store of potential energy which can be released by nuclear fusion. Such a fusion process is triggered by heat and pressure generated from gravitational collapse of hydrogen clouds when they produce stars, and some of the fusion energy is then transformed into sunlight. Such sunlight may again be stored as gravitational potential energy after it strikes the Earth, as (for example) snow-avalanches, or when water evaporates from oceans and is deposited high above sea level (where, after being released at a hydroelectric dam, it can be used to drive turbine/generators to produce electricity). Sunlight also drives many weather phenomena on Earth. An example of a solar-mediated weather event is a hurricane, which occurs when large unstable areas of warm ocean, heated over months, give up some of their thermal energy suddenly to power a few days of violent air movement. Sunlight is also captured by green plants as chemical potential energy, when carbon dioxide and water are converted into a combustible combination of carbohydrates, lipids, and oxygen. Release of this energy as heat and light may be triggered suddenly by a spark, in a forest fire; or it may be available more slowly for animal or human metabolism, when these molecules are ingested, and catabolism is triggered by enzyme action.

Through all of these transformation chains, potential energy stored at the time of the Big Bang is later released by intermediate events, sometimes being stored in a number of ways over time between releases, as more active energy. In all these events, one kind of energy is converted to other types of energy, including heat.</div>

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