For example, a steam powered electrical generating plant which operates between 500 K and 300 K (room temperature) has a maximum possible efficiency of 40%. You can check this using the equation for efficiency. Similar considerations hold for an internal combustion engine, the basic operation of which is illustrated below IL 71 **** (An especially well presented (very visual) discussion of the two laws)  
Fig. 37. The heat exchange for an internal combustion engine
In this segment of the cycle, the fuel mixture explodes, either from a spark plug for a gas engine or from the high pressure for a diesel engine. This drives the piston downwards, which subsequently turns the crankshaft and eventually the wheels - this is the part which converts the energy of heat into useful work. The piston then rises, expelling the exhaust gases which carry away the waste heat. The cycle then goes on to draw in more fuel mixture to repeat the cycle. The major point here is that the exhaust gases carry with them excess heat which could not be converted into useful work.
The important message here is that some ``waste heat'' is always expelled into the cooler reservoir; and that no heat engine could operate without such expulsion. This is why, for example, one notices in the winter near a steam powered electrical generating plant that nearby ice on a river is melted - this comes from the waste heat of the plant being expelled into the river.
The British scientist and author, C.P. Snow, had an excellent way of remembering the three laws:
1. You cannot win (that is, you cannot get something for nothing, because matter and energy are conserved).
2. You cannot break even (you cannot return to the same energy state, because there is always heat loss to work done, or there is always an increase in disorder; entropy always increases).
3. You cannot get out of the game (because absolute zero is unattainable).
Fig. 38. The student should try to complete this sentence.
The internal combustion engine
The following gives you the energy distribution for an internal combustion-driven car:
Input energy: (Heat content of the gasoline) 100%
Engine heat (heat lost in exhaust gases, heat lost o coolant , heat lost to air ): 62%
Drive Train: Overcoming friction in transmission, differential, and wheel bearings,): 10%, overcoming inertia, air resistance and gravity: 12%
Idling Losses – 17.2% Rolling Resistance – 4.2%
Aerodynamic Drag – 2.6% Driveline Losses - 5.6%
Accessories – 2.2% Engine Losses – 62.4%
Overcoming Inertia; Braking Losses– 5.8%
To move forward, a vehicle's drivetrain must provide enough energy to overcome the vehicle's inertia, which is directly related to its weight. The less a vehicle weighs, the less energy it takes to move it. Weight can be reduced by using lightweight materials and lighter-weight technologies (e.g., automated manual transmissions weigh less than conventional automatics).
In addition, any time you use your brakes, energy initially used to overcome inertia is lost.
Rolling Resistance – 4.2%
Rolling resistance is a measure of the force necessary to move the tire forward and is directly proportional to the weight of the load supported by the tire. A variety of new technologies can be used to reduce rolling resistance, including improved tire tread and shoulder designs and materials used in the tire belt and traction surfaces.
For passenger cars, a 5-7% reduction in rolling resistance increases fuel efficiency by 1%. However, these improvements must be balanced against traction, durabillity, and noise.
Aerodynamic Drag – 2.6%
A vehicle must expend energy to move air out of the way as it goes down the road—less energy at lower speeds and progressively more as speed increases. Drag is directly related to the vehicle's shape. Smoother vehicle shapes have already reduced drag significantly, but further reductions of 20-30% are possible.
Accessories – 2.2%
Air conditioning, power steering, windshield wipers, and other accessories use energy generated from the engine. Fuel economy improvements of up to 1% may be achievable with more efficient alternator systems and power steering pumps.
Overcoming Inertia; Braking Losses– 5.8%
Fig. 39. The energy losses of a car engine
(For detail see IL below
The New Age of “Green Cars”.
Scientific evidence strongly suggests that the buildup of greenhouse gases in the atmosphere is raising the earth's temperature and changing the earth's climate - both have many potentially serious consequences. Transportation, specifically the combustion of fossil fuels in our vehicles, is the single largest source of human-made greenhouse gases. The more fuel your vehicle burns the more greenhouse gases it emits.
You may be surprised to know that most vehicles produce several times their weight in greenhouse gases each year. Not only does most of the fuel you put in your tank become greenhouse gas emissions, but the carbon in the fuel combines with oxygen in the air, almost tripling the weight of the fuel itself.
A major contributor to the green house effect by human activity (sometimes referred to as anthropogenic) is carbon dioxide. (The other major contributor is water vapor). Carbon dioxide is produced from the combustion of fossil fuels (coal, oil, gas) in vehicles, industrial boilers and residential furnaces. The average car pumps two to three times its own weight in carbon dioxide into the atmosphere each year. About 30% of all carbon dioxide emissions in Canada are from road vehicles and mostly from personal and commercial light-duty vehicles.
The greenhouse gas estimates presented here are "full fuel-cycle estimates" and include the three major greenhouse gases emitted by motor vehicles: carbon dioxide, nitrous oxide, and methane (notice the absence of water vapor). Full fuel-cycle estimates consider all steps in the use of a fuel, from production and refining to distribution and final use. This gives a more complete picture of how using a particular fuel contributes to climate change.
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