Lecture 1: Energy and Environment

Transcription

1 Lecture 1: Energy and Environment Energy is a prime mover of economic growth and is vital to sustain the economy. Energy consumption is an indicator of economic growth of a nation Economic growth depends, among other factors, on the long term availability of resources that are affordable, accessible and their use do not pollute the environment. Industrialization contributes to economic growth and requires energy. Major energy intensive industries consumed 68% of the total energy available in A similar trend continues in the subsequent years also. Energy consumption is strongly related to environment cleanliness, when fossil fuel is the main source of energy Fossil fuel accounts for more than 70% of the total energy requirement of India and other countries Energy resources: Classification of energy resources is given in the following flow sheet: Energy Resources Primary (Natural) Secondary (Synthetic) Non Renewable (Fossil Fuel) Renewable Coke Fuel Gas (Producer Gas) Oil Coal Petroleum Natural Gas Solar Geothermal Wind Biomass Hydrothermal

2 It must be noted that all fossil fuel reserves are plant origin and it takes millions of years to form a deposit below the earth crust through physico chemical reactions Coal: Types of Non Renewable sources of energy Coal is formed by the prolonged action of geological forces on the plant and vegetal matter accumulated below the earth crust. The process is called COALIFICATION. Coalification is both time and force dependent. Coalification brings following changes to the accumulated plant: Wood Peat Lignite Bituminous Anthracite Graphite Increase in time and magnitude of forces Both, physical change like colour, strength, density and structure; and chemical change occur. Chemical changes are important: Oxygen decreases from 40% for wood to 305 for peat, 20% for lignite, 5% for bituminous and 2% for anthracite coal. Volatile matter decreases from about 70% for wood to 5% or less for anthracite coal. Increase in carbon from about 30% for wood and peat to 90 95% for anthracite coal. Petroleum: Petroleum is formed in the earth s crust from the accumulated vegetal and animal matter metamorphic processes similar to coalification. From crude petroleum gasoline, lubricating oil, fuel oils etc. are obtained. Natural gas: It is used directly

3 Renewable sources of energy Geothermal: energy obtained by tapping the heat of the earth below its surface. Hot underground water or steam is used to produce electricity. Biogas: produced from wastes of paper and sugar industries, animal and so on. CH 4 is the product. Bio fuel: Biodiesel, ethanol etc. are derived from plants. Solid Biomass: Wood fuel, biogenic portion of municipal waste, certain plants. Biomass mass may be used in a number of ways to produce energy. The common methods are gasification, combustion, fermentation and anaerobic digestion. India is very rich in biomass Hydro thermal: Energy in water in the form of KE, temperature difference. Solar Energy: Energy collected from sunlight. It can be used in many ways: Generate electricity using photovoltaic cells. Generate electricity using concentrating solar power. Photovoltaic cells have a low efficiency factor Energy Scenario under Indian Condition India ranks 6 th in the world in total energy consumption and needs to accelerate the development of energy sector to meet 8 9% economic growth in the country. India though rich in coal and abundantly endowed with renewable energy has very small hydrocarbon reserves (0.4% of the world s reserve). India is a net importer of energy, more than 25% of primary energy needs being met through imports in the form of crude oil and natural gas. In energy production, coal and oil account for 54% and 34% respectively with natural gas, hydro and nuclear contributing to the rest. Industrial sector in India consumes 52% energy. Consumption of primary energy in India is 530 Kg of oil equivalent/person in 2004 compares to 1240 Kg oil equivalent/person in China and the world average of 1770 Kg of oil equivalent/person.

4 Primary energy consumption per person will grow with the growth in economy because energy consumption is an index of country s economic growth and prosperity. Issues related to Fossil Fuel Usage Fossil fuel contains potential energy/chemical energy and is obtained by combustion. The figure shows: Potential energy of fuel Combustion Sensible heat in POC at flame temperature Heat Transfer between POC and the sink (sink: furnace walls/product) to raise the sink temperature Discharge of POC at T T sink (If T sink is 1200 o C then T POC 1200 o C) Increase in C of environment is proportional to fossil fuel input Loss of high quality thermal energy (quality of energy α temperature of POC) Thus usage of fossil fuel energy source relates to environment sustainability (increased use of fossil fuel increases the C emission) and energy security (limited fossil fuel reserves).

5 What should be done???? Energy consumption is an indicator of the economic growth of a nation. A developing nation like ours has the needs of energy for industrial growth. Unless renewable sources of energy are exploited on a massive scale, fossil fuel is the only source of energy. Limited reserves of fossil fuels and the way in which fossil fuel energy is available (combustion and unutilized energy in Products of combustion) need ways to search means to optimize energy consumption. Energy saving will automatically reduce the carbon emission. We should think in terms of the following concept Switch: Can we switch over to renewable energy source? If yes, to what extent? Reduce: Can we reduce the present level of energy consumption? If yes, then how? Capture: Can we capture the heat of POC which is exiting the industrial furnace? If yes, how? Key words: Energy resources, Environment, furnaces, energy efficiency