In a typical internal combustion engine, such as those found in most automobiles, energy is wasted in a number of ways:
1. Thermal Energy: The majority of the energy from the combustion process is lost as heat through the exhaust. This is because the combustion process is far from perfectly efficient.
2. Mechanical Energy: Some energy is lost through mechanical inefficiencies in the engine itself, such as friction between moving parts.
3. Pumping Losses: Engines lose energy through the work required to pump air and fuel into the cylinders and push out the exhaust gases.
4. Radiated Energy: Some energy is lost through heat radiated from the engine block itself, particularly when the engine is running hot.
5. Idle Losses: When the engine is running but the vehicle is not moving (idling), all of the energy being used by the engine is essentially wasted.
6. Accessory Load: Energy is used to power the various accessories in a vehicle, such as the alternator, power steering pump, air conditioning compressor, etc. While these are necessary for the operation of the vehicle, they do represent a form of energy loss in terms of the overall efficiency of the engine.
7. Incomplete Combustion: Not all of the fuel that enters the engine's combustion chamber is burned. Some is expelled as unburned hydrocarbons, which is not only a waste of energy but also a source of pollution.
8. Transmission Losses: Some energy is lost in the transmission as the power is transferred from the engine to the wheels.
It's important to note that these are inherent to the design of internal combustion engines, and while engineers continually work on improving the efficiency of these engines, these forms of energy loss are difficult to completely eliminate.