Limitations Susceptable to lead build up, require use of lead free gasoline. Require “richer” fuel mixture, burn more fossil fuels and emit more CO 2 In fact most of emission is CO 2 which is a greenhouse gas The manufacturing of catalytic converters requires palladium and/or platinum for which there are environmental effects from the mining of these metals

Diesel Engines Found mostly in large trucks, locomotives, farm tractors and occasionally cars. An internal combustion engine Does not mix the fuel and air before they enter the combustion chamber Does not use a spark for emission Heavier and bulkier than gasoline engine Slower speed and slower response to driver More efficient than gasoline engines, efficiencies of over 30% of converting fuel energy to mechanical energy.

Diesel Engines Piston moves down, drawing air into the cylinder Compression stroke –chamber only contains air and the piston pushes up, increases the air pressure and temperature until ignition can occur when the fuel is introduced. Short burst of fuel is sent into the chamber when this pressure is reached. Explosion heats gases in chamber and causes them to expand, pushing the piston down. Piston pushes up, expelling the exhaust gasses.

Diesel engines-advantages Ignition occurs at a higher T, resulting in higher efficiency than gasoline engines (more than 30% efficient in converting chemical to mechanical energy). Can run on low grade fuels and diesel fuels have 10% more BTU per gallon. CO emissions are lower – more air in the chamber means more CO 2 than CO is formed

Diesel engines-disadvantages Hard to start in cold weather-compression stroke can’t reach the ignition temperature. Solved with installation of a glow plug, a small heater. Gelling-Diesel fuel can crystallize in cold weather clogging fuel filters and hindering fuel flow. Solved via electric heaters on fuel lines. Fuel injection is critical, if timing is off, combustion is not complete and results in excess exhaust smoke with unburned particles and excess hydrocarbons.

Diesel engine disadvantages Noisy More expensive initially Smell Diesel fuel has become routinely more expensive than gasoline – Why?-rising demand, cheap gas due to decreased demand, environmental restrictions (need for lower sulfer emissions and higher taxes on diesel fuel than gasoline).

Gas turbines Newer type of internal combustion engine. Used in jets and some electric power plants Air pulled in the front and compressed in a compressor. (The rotating fan-like structure you see when you look into a jet engine). Air is mixed with fuel and ignited, this heated mixture expands. Expanding gas moves through the turbine, which is connected to the compressor by a rotating shaft. Hot gases are expelled with a greater velocity than the intake air, giving the engine is thrust.

Gas Turbines For electricity generation, the power output turbine turns the shaft. For aircraft, the gas is expelled out the jet nozzle.

Gas Turbines 20-30% efficiency converting thermal energy to mechanical energy Lightweight Respond quickly to changing power demands Relatively cheap for public utilities Limitations are the need for materials to withstand T~ 1000 C and the high rotation speeds

Generating Electricity 1831 Michael Faraday discovers that by moving a magnetic bar near a loop of wire, an electric current can be induced in the wire. Known as electromagnetic induction This allowed the generation and transmission of electricity possible, along with electric motors and modern communications and computer systems Electromagnetic induction animation

Electromagnetism It was already known that the opposite was true, that a metal placed inside a current loop could become magnetized.

Generators Coil of copper wire mounted on a rotating armature Coils are rotated through a magnetic field This induces a current in the coils. But, the induced current resists the rotation of the coils, so we need an external energy source to rotate the coils. The current exits the rotating coil via slip rings that are in contact with carbon brushes. The direction of current flow changes as the coil rotates in the magnetic field. This produces an alternating current.

Generator

Alternating vs direct current Direct current –flow of current in one direction. Produced by batteries, solar cells, dynamos Alternating current – when the flow of current periodically changes direction(50-60 times per second). This is what is delivered to homes and businesses