SCIENCE 10
UNIT B: ENERGY FLOW IN TECHNOLOGICAL SYSTEMS
Unit Focus Questions
- Which came first: science or technology, and is it possible for technological development to take place without help from “pure” science
- How did effort to improve the efficiency of heat engines result in the formation of the first and second laws of thermodynamics?
- How can the analysis of moving objects help in the understanding of changes in kinetic energy, force, and work?
- Why are efficiency and sustainability important considerations in designing energy conversion technologies?
B3.0 Principles of energy conservation and thermodynamics can be used to describe the efficiency of energy transformations
Key Concepts
- Technological innovations of engines that led to the development of the concept of energy
- Design and function of technological systems and devices involving potential and kinetic energy, and thermal energy conversions
- Efficient use of energy, and environmental impact of inefficient use of energy
Learning Outcomes
- Describe how the first and second law of thermodynamics have changed our understanding of energy conversions
- Describe qualitatively, and in terms of thermodynamic laws, energy transformations in devices and systems
- Define, operationally, “useful” energy from a technological perspective, and analyze the stages of “useful” energy transformations in technological systems
- Recognize that there are limits to the amount of “useful” energy that can be derived from the conversion of potential energy to other forms in a technological device
- Identify the processes of trial and error that led to the invention of the engine, and relate the principles of thermodynamics to the development of more efficient engine designs
- Explain, quantitatively, efficiency as a measure of the “useful” work compared to the total energy put into an energy conversion process or device
- Apply concepts related to efficiency of thermal energy conversion to analyze the design of a thermal device
- Compare the energy content of fuels used in thermal power plants in Alberta (costs, benefits, efficiency, sustainability)
- Explain the need for efficient energy conversions to protect our environment and to make judicious use of natural resources
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B3.1 Laws of Thermodynamics
Systems
System – a set of interconnected partsOpen system – exchanges both energy and matter with the surroundings
Closed system – exchanges energy with the surroundings but not matter.
Isolated system – does not exchange energy or matter with the surroundings.
The First Law of Thermodynamics
Energy cannot be created nor destroyed. It can only be changed from one form to another.The Perfect Machine Cannot be Achieved
Perfect machine – hypothetical machine in which all the input energy is converted completely into mechanical energy.Perpetual motion machine - A machine that will run forever without refueling
The Second Law of Thermodynamics
Heat (energy) always flows from hot objects (areas of high energy) to cold object (areas of low energy), never from cold objects to hot objects.Heat engine – device that converts heat energy into mechanical energy
Heat Engines and Heat Pumps
Heat pump – device that uses mechanical energy to transfer heat energy.
B3.2 The Development of Engine Technology
Developing a Technology
Technology (devices) does not appear out of nowhere. Normally somebody will develop a very basic prototype and different people will keep improving it over time.
Engines
- Engines developed from being used to pump water from coal mines to powering vehicles.
- All engines use a chemical fuel (chemical energy) to heat a gas which expands (thermal energy). The expanding gas pushes on a piston which converts to motion (kinetic energy).
- 1680 Christian Huygens experimented with a piston that was moved by gunpowder. Obviously it was very dangerous and the piston had to be physically moved back to the start position.
- Most Steam engines were first used to pump water out of coal mines.
- 1654 Otto von Guericke demonstrated the power of vacuums and air pressure.
- 1690 Denis Papin used heat to create stem that did the work. Metal working technology did not allow for the construction of high quality cylinders the engine needed.
- 1698 Thomas Savery invented the first steam powered pump. It was used to pump water out of coal mines. The pump could only lift water 6 m (otherwise the boiler would explode) which was not an improvement over animal powered pumps.
- 1712 Thomas Newcomen also used steam to drive the piston in the cylinder. Cold water was sprayed into the cylinder to condense (cool) the steam and move the cylinder back down. Although it allowed water to be pumped higher than animal powered engines, it was very inefficient and required a huge amount of heat and fuel to function.
- 1763 James Watt added a second cylinder in which the steam was condensed. This way the main cylinder remained hot and dramatically increased the engine’s efficiency. This engine dominated industry for almost 200 years. It was large, dirty and inefficient but better then animal or human power.
- 1794 Robert Steele revived Huygen’s idea of trapping an explosion but used gases produced by oil and tar instead of gunpowder.
- In 1801 Phillippe Lebon invented the first internal combustion engine powered by coal gas. The explosion of the gas, caused by an electrical spark, would expand and push the piston.
- In 1867 N.A. Otto and Eugen Langen improved the efficiency by compressing the coal gas-air mixture before ignition to improve efficiency (four stroke engine).
- In 1880 Gottlieb Daimler developed an engine that ran on liquid petroleum products (gasoline) instead of coal gas.
Developing Future Technologies
Technologies develop over time. What is science fiction today is tomorrow’s reality..
B3.3 Useful Energy and Efficiency
Useful energy
Energy input – the energy put into the situationUseful energy output – the energy taken out of the situation to do a specific task.
Lost energy is the part of the energy input that is changed into non-useful energy (heat due to friction)
For example out of 100 J worth of fuel that you put into a car, only 14 to 30 J is used to propel the car forward (useful energy) the remaining energy is lost as heat.
Efficiency
Efficiency - is a measure of how much of the input energy is changed into useful output energy.
Efficiency = Output Energy / Input Energy x 100%
Ex. An SUV uses 2.5 × 108 J of fuel generate 1.1 × 108 J of kinetic energy. How efficient is the SUV?
Efficiency = Output Energy / Input Energy x 100 %
Efficiency = 1.1 × 108 J / 2.5 × 108 J x 100 %
Efficiency = 44 %
Efficiency = 1.1 × 108 J / 2.5 × 108 J x 100 %
Efficiency = 44 %
Practice Problems
Practice Questions # 1- 3 on pages 216 – 217
B3.3 Check and Reflect p. 220
Applications 5 to 9
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B3.4 Energy Applications
Energy Supply
Solar Energy SourcesThe Sun is a ball of superheated gases that undergo a fusion nuclear reaction to release light energy. When the light hits the Earth it is changed into several different types of energy.
Wind energy is caused by the uneven heating of Earth’s atmosphere. As sections warm up the air expands outwards causing wind.
Water energy is caused by the evaporation of water. The evaporated water rises up through the atmosphere and falls as precipitation. The rain hits the ground and flows downhill to the oceans. The river can be dammed and used to create hydro-electric energy.
Biomass energy is released when biological matter is combusted. Plants use the sunlight to growth by creating glucose (sugar). By burning the glucose in the biomass we can use the energy.
- Garbage
- Landfill gases
- Alcohol foods
- Crops
- Wood
Non-Solar Energy Sources
Non-solar energy sources are not related to the Sun.
Geothermal energy is caused by the heat of Earth’s interior. Superheated water deep underground forces its way to the surface where it erupts as a geyser. Geothermal plants use the steam to create electricity.
Tidal energy is caused by the force of gravity of the moon on the Earth’s oceans. The oceans move towards the moon causing tides. The moving water can be used to create electrical energy.
Renewable and Non-renewable Energy Sources
Renewable energy sources are constantly being recreated. For example solar, wind, water, geothermal, tidal and biomass. For all practical implications these are unlimited sources. Non-renewable energy sources can only be used once. For example nuclear and fossil fuels. Once they are used, they are gone forever.
Energy Demand
Energy demand has been increasing over time. Three factors have led to this:- Each person uses more energy today than people have used previously.
- The world’s population has been growing exponentially. See graph page 223. A few countries like China have imposed population restrictions.
- The world is heavily dependent on non-renewable energy sources. Alberta’s electricity is mostly powered by coal.
The Effects of Energy Use
The widespread use of fossil fuels has resulted in many problems- Greenhouse gases are released by burning fossil fuels.
- Smog is created by burning fossil fuels
- Oil tanker spills destroy marine habitats
- Oil drilling has environmental consequences.
Energy Consumption and Conservation
- Our supply of conventional oil is expected to last 40 years from 2000 which means in 2040 we will run out of oil. (estimated)
- Our supply of natural gas is expected to last 62 years from 2000, which means in 2060 we will run out of natural gas. (estimated)
- Both of these events will occur within your lifetime!
Sustainable Development and Planning for the Future
Sustainable development means continuing to improve living conditions but at a rate and using technology that will be viable forever.For example designing cars that run on solar power, using geothermal plants for heating and electricity.
Practice Problems
Do Review questions # 30 – 60 on pages 233-235