An Energy Source must be Bountiful…… P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Conversion of A Resource into Useful Form

4 th Law & A Two Way implementation Conversion of available resource into usable form of resource. –Combustion & Heat Transfer –Thermodynamics – Carnot & Rankine Utilization of usable form into Mechanical Power –Parson’s Approach –De Laval’s Approach

4 th Law of thermodynamics Matter cycles in regions of energy flow; such cycles, visible in natural complex structures, including those of life, occur as limited material resources scramble to provide a vehicle for entropy export. {Schneider & Sagan, 2005}

Entropy Vehicles on Earth Biomass energy: 4.3 x 10 3 EJ/year Wind, waves convection and currents: 11.7 x 10 3 EJ/year Convection in volcanoes and hot springs: 9.36 EJ/year Ocean tides: 93.6 EJ/year Direct conversion to heat in air, earth and oceans: 2.55 x 10 6 EJ/year

A tree converts disorder to order with a little help from the Sun The building materials are in a highly disordered state - gases, liquids and vapors. The tree takes in carbon dioxide from the air, water from the earth as well as a small amount from water vapor in the air. From this disordered beginning, it produces the highly ordered and highly constrained sugar molecules, like glucose. The radiant energy from the Sun gets transferred to the bond energies of the carbons and the other atoms in the glucose molecule. In addition to making the sugars, the plants also release oxygen which is essential for animal life.

First Law Analysis of Photosynthesis:SSSF First Laws for furnace in SSSF Mode: m CO2 m water m vegetation Q Q W m Oxygen Conservation of Mass:

First Law Analysis of Photosynthesis:SSSF Species Conservation Equation: First Laws for furnace in SSSF Mode: Conservation of Mass:

Fossilization : Bio - Chemical Peat deposition is the first step in the formation of coal. The humid climate of the Carboniferous Period (360 to 286 million years ago), which favoured the growth of huge tropical seed ferns and giant nonflowering trees, created the vast swamp areas As the plants died and fell into the boggy waters, which excluded oxygen and killed bacteria, they partially decomposed but did not rot away. The vegetation was changed into peat, some of which was brown and spongy, some black and compact, depending on the degree of decomposition.

First Law Analysis of Formation of Peat :SSSF Species Conservation Equation: First Laws for furnace in SSSF Mode: Conservation of Mass: W m CO2 m vegetation Q Q m Peat m CH4

Peat Peat is The first stage in the formation of coal from wood (cellulose). Rate of reaction : 3cm layer per 100 years. Light brown fibrous at the surface and colour becomes darker with depth. Typical Composition: Moisture : 85%, Volatile Matter : 8 %, Fixed Carbon : 4%, Ash : 3%. Calorifica Value : 650 kCal/kg. Occurrence of Peat : Niligiri Hills and banks of Hooghly. Sun dried Peat is very useful as a fuel with following composition: Moisture : 20%, Volatile Matter : 50 %, Fixed Carbon : 25%, Ash : 5% Bulk density : 300 kg/m 3 and low furnace temperature and efficiency. Products from Peat: Charcoal,Producer gas.

Secondary Transformation : Geo-Chemical Stage The decayed vegetation was subjected to extreme temperature and crushing pressures. It took several hundred million years to transform the soggy Peat into the solid mineral. 20 m of compacted vegetation was required to produce 1 m seam of coal. This is called as coalification or coal forming. The extent to which coalification has progressed determines the rank of coal.

Modeling of Coalification Peat to Enriched peat: (mostly due to heating) lignite to Sub-bituminous: (mostly due to pressure &heating) Enriched peat to lignite: (mostly due to pressure &heating) Sub-bituminous to High volatile Bituminous:

High Volatile Bituminous to Medium volatile Bituminous: Medium Volatile Bituminous to Low volatile Bituminous: Low Volatile Bituminous to semi Anthracite: Semi Anthracite to Anthracite:

Constant Pressure Steam Generation Process Constant Pressure Steam Generation: =0 Theory of flowing Steam Generation

Knowledge for Use & Conservation Constant Pressure Steam Generation: Practical way of understanding the use of fuel energy: Is it possible to get high temperature with same amount of burnt fuel? What decides the maximum possible increase for same amount of burnt fuel?

Carnot’s View of Rankine Cycle Creation of Temperature at constant pressure :

Steam Generation : Expenditure Vs Wastage h s Liquid Liquid +Vapour Vapour

Variable Pressure Steam Gneration s h

Specific PressureEnthalpyEntropyTempVolume MPakJ/kgkJ/kg/KCm3/kg Analysis of Steam Generation at Various Pressures

More Availability of Energy Specific TempPressureVolumeEnthalpyEntropy CMPam3/kgkJ/kgkJ/kg/K