Chapter #14 Guided Reading
14.1 OUTLOOK FOR ENERGY
● Energy Crises in Ancient Greece and Rome
The energy crisis is not new. Ancient Greeks and Romans exhausted the wood supply upon which they depended for heat and cooking. They began to take advantage of solar energy to heat.
● Energy Today and Tomorrow
There has been a succession of primary energy sources throughout the world. Use of wood peaked in the U.S. in the 1880s when coal assumed preeminence as the primary energy source. This was followed by oil, which has dominated since WWII. The use of fossil fuel has improved the standard of living: improved sanitation, medicine, and agriculture are all consequences. The only thing certain about tomorrow’s energy resources is that they will change.
14.2 ENERGY BASICS
Energy is the ability to do work. Work is the product of force times distance. A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction. So energy is defined by its ability to move something.
The First Law of Thermodynamics states that energy can neither be created nor destroyed, but it may be transformed from one type into another type. Solar can be converted to heat and then to electricity, for example.
The Second Law of Thermodynamics states that any conversion of energy from one form to another requires that some of the initial energy input be degraded into a less useful form, usually heat. No energy conversion is 100% efficient. For example, it is impossible to convert electrical energy to light energy with 100% efficiency. There will always be some heat loss.
14.3 ENERGY EFFICIENCY
Two types of efficiencies can be derived from the 1st and 2nd laws. First-law efficiency deals with the amount of energy without consideration of the quality or availability, and is expressed by energy delivered/energy supplied. Suppose a furnace delivers 1 unit of heatenergy to the house for every 1.5 units of energy supplied to the furnace. This represents an efficiency of 67%. The first-law efficiency may include losses of energy involved in extracting the gas from the ground and transporting it to where it is used (as is done for a full energy analysis of a process), or it may include only the energy actually delivered. Second-law efficiency is the minimum amount of energy required/actual energy input. The second-law efficiency tells us how efficient a process is relative to how efficient it
could be. Essentially the second-law efficiency tells us how efficient it could be, the first-law tells us how efficient a process actually is.To use high quality energy for low-quality energy tasks is wasteful, and the second-law efficiency gives information on this. Power plants, for example, produce enormous amounts of waste heat, as do the transmission lines.
14.4 ENERGY SOURCES AND CONSUMPTION
The U.S. has 5% of the world’s population and accounts for 25% of world energy consumption. A peak in oil production (extraction) is expected to occur in 2020-2030, followed by a decline. However, the demand for oil may occur sooner, which will raise the price of oil significantly, reducing the growth rate in demand, stimulating the development of alternative energy sources and conservation, and possibly extending the supply of oil.
● Fossil fuels and Alternative Energy Sources
About 90% of energy consumed in the U.S. today are from nonrenewable fossil fuels: petroleum, natural gas and coal. Alternative energy sources include geothermal, nuclear, hydropower and solar, some of which are renewable.Since 1980 energy consumption in the U.S. has increased from about 20 exajoules to
more than 95 exajoules. About 50% was wasted. Energy conservation is one of our greatest untapped energy sources!
14.5 ENERGY CONSERVATION, INCREASED EFFICIENCY, AND COGENERATION
Conservation of energy simply means using less. Energy may also be conserved by increasing the energy efficiency (1st and 2nd-law efficiencies) of devices and processes. Cogeneration is a means of increasing the efficiency of our energy delivery processes by taking advantage of wasted heat energy. For example, the hot water that created by condensing the steam in electric power plants is now discharged into lakes or rivers in the U.S. In Europe it is common to pipe this hot water into the cities to heat homes.
A Closer Look 14.1: Energy Units
The joule is the fundamental International System energy unit, and equals the force of 1 Newton (N) applied over a distance of 1 m. One Newton is the amount of force required to give a 1-kg mass an acceleration of 1 m/s/s, so 1 Joule is the force of 1 Newton times 1 meter (force times distance). The Watt is a measure of the rate at which energy is used. A watt (W) is equivalent to 1 joules per second. A kilowatt-hour, which household bills are based on, is the equivalent of using 1000 Watts for 1 hour.
Conversions:
1 cal = 4.2 joules
1 Wh or 1 Watt-hour = 3600 joules
1 Kcal/hr = 1,163 Wh
1 exajoule = 1018 Joule or 1 billion billon Joules
● Building design
Building designs offer opportunities for energy conservation. Better insulation, use of active and passive solar designs, and appropriate landscaping can help.
● Industrial Energy
Usage of the principle above has allowed US industries to increase production without increasing energy use in direct proportion.
In terms of automobile design and regulation, hybrid cars are becoming more common. It may be possible to tax inefficient autos such as SUVs and to raise the tax on gasoline. Europeans have been paying a high tax on gasoline for many years.
● Values, Choices, and Energy Conservation
Many of us routinely practice conservation, and there are many ways that we can all contribute (the text gives an extensive list). Experience in European nations indicates that Americans could greatly improve on our energy conservation efforts and still maintain a high quality of life.
● Energy Crises in Ancient Greece and Rome
The energy crisis is not new. Ancient Greeks and Romans exhausted the wood supply upon which they depended for heat and cooking. They began to take advantage of solar energy to heat.
● Energy Today and Tomorrow
There has been a succession of primary energy sources throughout the world. Use of wood peaked in the U.S. in the 1880s when coal assumed preeminence as the primary energy source. This was followed by oil, which has dominated since WWII. The use of fossil fuel has improved the standard of living: improved sanitation, medicine, and agriculture are all consequences. The only thing certain about tomorrow’s energy resources is that they will change.
14.2 ENERGY BASICS
Energy is the ability to do work. Work is the product of force times distance. A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction. So energy is defined by its ability to move something.
The First Law of Thermodynamics states that energy can neither be created nor destroyed, but it may be transformed from one type into another type. Solar can be converted to heat and then to electricity, for example.
The Second Law of Thermodynamics states that any conversion of energy from one form to another requires that some of the initial energy input be degraded into a less useful form, usually heat. No energy conversion is 100% efficient. For example, it is impossible to convert electrical energy to light energy with 100% efficiency. There will always be some heat loss.
14.3 ENERGY EFFICIENCY
Two types of efficiencies can be derived from the 1st and 2nd laws. First-law efficiency deals with the amount of energy without consideration of the quality or availability, and is expressed by energy delivered/energy supplied. Suppose a furnace delivers 1 unit of heatenergy to the house for every 1.5 units of energy supplied to the furnace. This represents an efficiency of 67%. The first-law efficiency may include losses of energy involved in extracting the gas from the ground and transporting it to where it is used (as is done for a full energy analysis of a process), or it may include only the energy actually delivered. Second-law efficiency is the minimum amount of energy required/actual energy input. The second-law efficiency tells us how efficient a process is relative to how efficient it
could be. Essentially the second-law efficiency tells us how efficient it could be, the first-law tells us how efficient a process actually is.To use high quality energy for low-quality energy tasks is wasteful, and the second-law efficiency gives information on this. Power plants, for example, produce enormous amounts of waste heat, as do the transmission lines.
14.4 ENERGY SOURCES AND CONSUMPTION
The U.S. has 5% of the world’s population and accounts for 25% of world energy consumption. A peak in oil production (extraction) is expected to occur in 2020-2030, followed by a decline. However, the demand for oil may occur sooner, which will raise the price of oil significantly, reducing the growth rate in demand, stimulating the development of alternative energy sources and conservation, and possibly extending the supply of oil.
● Fossil fuels and Alternative Energy Sources
About 90% of energy consumed in the U.S. today are from nonrenewable fossil fuels: petroleum, natural gas and coal. Alternative energy sources include geothermal, nuclear, hydropower and solar, some of which are renewable.Since 1980 energy consumption in the U.S. has increased from about 20 exajoules to
more than 95 exajoules. About 50% was wasted. Energy conservation is one of our greatest untapped energy sources!
14.5 ENERGY CONSERVATION, INCREASED EFFICIENCY, AND COGENERATION
Conservation of energy simply means using less. Energy may also be conserved by increasing the energy efficiency (1st and 2nd-law efficiencies) of devices and processes. Cogeneration is a means of increasing the efficiency of our energy delivery processes by taking advantage of wasted heat energy. For example, the hot water that created by condensing the steam in electric power plants is now discharged into lakes or rivers in the U.S. In Europe it is common to pipe this hot water into the cities to heat homes.
A Closer Look 14.1: Energy Units
The joule is the fundamental International System energy unit, and equals the force of 1 Newton (N) applied over a distance of 1 m. One Newton is the amount of force required to give a 1-kg mass an acceleration of 1 m/s/s, so 1 Joule is the force of 1 Newton times 1 meter (force times distance). The Watt is a measure of the rate at which energy is used. A watt (W) is equivalent to 1 joules per second. A kilowatt-hour, which household bills are based on, is the equivalent of using 1000 Watts for 1 hour.
Conversions:
1 cal = 4.2 joules
1 Wh or 1 Watt-hour = 3600 joules
1 Kcal/hr = 1,163 Wh
1 exajoule = 1018 Joule or 1 billion billon Joules
● Building design
Building designs offer opportunities for energy conservation. Better insulation, use of active and passive solar designs, and appropriate landscaping can help.
● Industrial Energy
Usage of the principle above has allowed US industries to increase production without increasing energy use in direct proportion.
In terms of automobile design and regulation, hybrid cars are becoming more common. It may be possible to tax inefficient autos such as SUVs and to raise the tax on gasoline. Europeans have been paying a high tax on gasoline for many years.
● Values, Choices, and Energy Conservation
Many of us routinely practice conservation, and there are many ways that we can all contribute (the text gives an extensive list). Experience in European nations indicates that Americans could greatly improve on our energy conservation efforts and still maintain a high quality of life.