By Tushar Gupta Class 10 RESONANCETopic: Energy
What is energy ?• Energy is the capacity of a body for doing work.• Energy stored in a body or a system is equivalent to total work done by the body till whole whole of the energy has been completely exhausted.
• Most of our energy requirement is fulfilled from the fuels and electricity.• Energy can be converted from one form to another.
History of energy use• Date back several thousand years ago. Sun is probably the first source of energy known to mankind.• Animals learn "energy" and its "power" when getting warmth under sun and when facing the danger of a forest fire due to lightning.
Forms of energy In everyday life, energy exists in these eight forms:• Mechanical (kinetic and potential)• Chemical• Nuclear• Heat• Light• Electrical• Sound
More details about the eight forms of energy• Mechanical energy is• The energy of motion (kinetic) and the energy of position (potential)• Elastic potential energy is stored in a stretched spring or a bowstring• When an object is lifted above the ground, it has gravitational potential energy
• Chemical energy• The energy that bonds molecules together.• Nuclear energy• Energy released, when some changes take place in the nucleus of an atom of a substance.
• Thermal (heat) energy• Energy of moving and vibrating molecules• A specific kind of kinetic energy.• Light energy• Hot objects like a filament lamp or a gas mantle give off light• Light is a form of electromagnetic radiation.
• Electrical energy• Energy of moving electrons• Electrical appliances use it to operate• Sound energy• Vibrating objects produce sound• A form of energy detected by the ear. Music and noise are sound.
How do we use energy?To human, its main function can be grouped into five main categories:• Energy allows us to see• Energy give us warmth• Energy produces growth• Energy produces motion• Energy powers technology
Energy Sources Classified as non-renewable and renewable sources .Non-renewable Renewable(1) Petroleum (Oil) (1) Hydropower(2) Natural Gas (2) Geothermal(3) Coal (3) Solar(4) Propane (4) Wind(5) Uranium (5) Biomass
Non-renewable Sources of energy• Non-renewable sources require millions of years of natural processes to be produced and cannot be replenished.• Coal , petroleum and natural gas and propane are also known as fossil fuels
Fossil fuels as source of electricity and mains of heating and transportation
Distribution of fossilfuel use in the world natural gas 25% petroleum 38% coal 21% others 16%
Renewable Sources of energy Five renewable sources used most ofteninclude hydropower, solar, wind, geothermal, and biomass can be replenished in a short period of time
Solar energy• Sunlight is the most abundant energy source on the earth• On average, the earths surface receives about 1.2 x 1017 W of solar power• Most of the other renewable energy also depend on the sun as the primary source
Advantages of Renewable Energy atMacro and Micro Level
Composition of solar energy (Sunlight) Composition of sunlightUltra- violet rays Visible light Infra red rays
Wind energy• Wind contains kinetic energy• The higher the wind speed ,the higher the kinetic energy• Kinetic energy of the wind→ rotor( blades with an aerodynamic profile) → transmits the rotational motion via a gear set to the generator → power
Geothermal energy• Natural heat extracted from the earths crust• In form of heat, which originates deep in the earths molten interior• Responsible for volcanoes and earthquakes
Biomass energy• Utilization of organic waste to produce energy• Chemical energy stored in plants and animals or in the animal waste is called bio- energy• Burning of the biomass will release the energy in the form of heat
Hydropower• Capture the kinetic energy of falling water to generate electricity• Flowing or falling water rotates turbines and generators where kinetic energy is converted to mechanical → electrical energy
What is a good source of energy?We could say that a good source of energy would be one• Which would do a large amount of work per unit volume or mass,• Be easily accessible,
• Be easy to store and transport, and• Perhaps most importantly, be economical
How much energy do we use?• According to the Key World Energy Statistics (2002 Edition) from the International Energy Agency (IEA), the world consumption breakdown of primary energy in 2000 is as follows:
Energy Conversions• All forms of energy can be converted into other forms. – The sun’s energy through solar cells can be converted directly into electricity. – Green plants convert the sun’s energy (electromagnetic) into starches and sugars (chemical energy).
– In an electric motor, electromagnetic energy is converted to mechanical energy.– In a battery, chemical energy is converted into electromagnetic energy.– The mechanical energy of a waterfall is converted to electrical energy in a generator.
Chemical Heat Mechanical• In an automobile engine, fuel is burned to convert chemical energy into heat energy. The heat energy is then changed into mechanical energy.
Do you know???• Since the 1980s the Hong Kong Observatory has employed solar cells to power some automatic weather stations in many places of Hong Kong. Up to now, there are over 20 stations equipped with solar cells.
Energy and Environment Pollutants• Burning of fossil fuels produce air pollution. The followings are a brief description of the air pollutants:
Carbon dioxide• Carbon dioxide is released into the atmosphere as a result of burning fossil fuels such as coal, oil and natural gas.• Increases in carbon dioxide concentrations results in global warming due to greenhouse effect.• It is predicted that the temperature of the world would rise by 1.5°C in 50 years. This in effect alters precipitation patterns and raises sea levels by about one metre.
Nitrogen oxides• Nitrogen oxides (NOx) are released by burning fossil fuels at electric power plants and in automobiles,• Nitrogen oxides are an important precursor to ozone and acid rain. NOx, when mixed with other chemicals in air under the action of sunlight, generates photochemical smog and reduced visibility
Sulphur dioxide• Sulphur dioxide (SO2) comes from the combustion of fuel containing sulphur, mostly coal and oil• NOx and SO2 produces acid rain, which is the main cause of acidification of lakes, accelerated corrosion of buildings and monuments.
Mercury• Mercury is a heavy metal that is discharged into the air and accumulates in our lakes, streams and ultimately inside our bodies• The largest sources of mercury in the environment are coal-fired power plants, medical waste and municipal waste incinerators
Ozone• Ozone is formed under a complex chain of chemical reactions in the presence of sunlight and high temperatures involving a host of precursors• Major ones are oxygen, nitrogen oxides (NOx) and reactive volatile organic compounds (VOC)• Common VOC source include paints
Energy crisis• Power plant, industries, buildings and motor vehicles rely heavily on fossil fuels, such as coal, oil and natural gas• Unfortunately, human activities have resulted in the consumption of these scarce natural resources
• Fossil fuels are also unevenly distributed around the world. Although only one-quarter of the worlds population lives in developed countries, the energy consumption accounts for three- quarters of total consumption in the world• Less developed countries often have to promote economic growth and to cope with high population growth
• Global demand for oil will grow by an estimated 50% during the next several decades, while both coal and natural gas consumption are expected to double
Effects on Hong Kong• No indigenous energy resources in Hong Kong, we have to rely totally on imported fuels, and we know that fossil fuels are already exhausting.
Conserve energy• Since fossil fuels are a nonrenewable source of energy, it is important that we conserve energy• We can conserve energy by turning off lights when they are not being used, walk instead of drive if we are going short distances and wear layers of clothes to keep warm.
How to save energy in daily lives?• Minimize energy use• Use energy efficiently• Minimize energy loss
Minimize energy use• Use ventilation or fans where possible• Relocate where seats under direct sunlight that require strong air-conditioner for comfort
• Organize "Dress Casual Day" on a weekly basis where air-conditioner is adjusted to a slightly higher temperature• Turn off some or all air-conditioners 15 minutes before leaving the room
Use energy efficiently• Preferred air-conditioner temperature set-point is 25.5 ºC when the outdoor air temperature is above 25.5 ºC for acceptable comfort conditions of least energy consumption
• Clean air-conditioner and dust filter regularly• Establish a maintenance program to ensure air-conditioner is operating efficiently
Minimize energy Loss• Keep windows and doors closed to minimize air infiltration when air-conditioner is running• Lower window blinds or curtains to reduce direct sunlight during summer time
• Turn off some lighting when the occupancy is low (e.g. on Saturdays)• Turn off lighting in public areas (e.g. pantries, lavatories, circulation space etc.) during lunch and after office hours
What have we learnt?• Energy does work.• Energy is never ‘used up’ it is simply converted from one form to another.• Fuels and food are sources of energy.• There are 3 main classes of fuel which can be used to generate electricity: Fossil fuels, renewable fuels and nuclear fuels.
• Fossil fuels such as gas, coal and oil and renewable fuels such as wood are burnt and heat is generated.• This heat is used to boil water and the steam that is created is used to turn large propellers called turbines.• These turbines then turn electrical generators.• There are other sources of energy such as: Solar power, wind power, hydroelectric power and wave power.
Conclusion• To make sure we have plenty of energy in the future, its up to all of us to use energy wisely• We must all conserve energy and use it efficiently. Its also up to those who will create the new energy technologies in the future