Earth/Space: Bellringer1.) What is the difference between
conserving electricity and increasing yourelectricity efficiency?
Electricity• 1/3 of the energy consumed globally is
used to generate electricity– 16 trillion kWh/year.–¼ is consumed in the United States
• Electricity is a secondary source of energy.– Generated from primary sources of energy.
• Coal, natural gas, nuclear fission….– Generated in large centralized power plants.
• Most power plants consist of a spinningelectrical generator.– Spinning caused by steam heated by coal,
nuclear fission, etc.– 2/3 of energy lost as heat
• Sent out into the world
• Cooling Towers– Cools the used
steam back into hotwater, so that it canbe re-used.
– About 2/3 of the heatis wasted, only about1/3 goes toelectricity.
• Something has to spin that generator– Usually a Steam Turbine that is powered
by a primary energy source.• Burning coal, oil, or natural gas• Nuclear Reactor
• The substation uses largetransformers
– converts the voltage up toextremely high voltages forlong-distancetransmission.
– Typical voltages for longdistance transmission are155,000-765,000 volts inorder to reduce line losses.
• A typical maximumtransmissiondistance is about300 miles.– 3 wires for 3 phases.– Extra wires are
ground wires.• Extract lightening
• For power to be used in a home orbusiness, it comes off the transmissiongrid and is stepped-down to thedistribution grid.
• Power is distributed todifferent sets of distributionlines and leave thesubstation in differentdirections.– Power lines have three
wires for the 3-phase power.– The fourth wire lower on the
poles is the ground wire.– Sometimes additional wires
are added for phone andcable.
• Regulator Bank– Located along the
line– Regulates voltage
• Prevents overvoltageor undervoltageconditions
• Taps– A house needs only
one of the threephases.
– Taps for one or twophases run off themainline downsidestreets
At the House• At each house, there is a
transformer drum attached tothe pole.
• In subdivisions, the lines areoften underground, with agreen transformer box aboveground.
• Transformer reduces 7200volts down to 240 volts.
• The 240 volts entersa house through atypical watt-hourmeter.
• The meter lets thepower companycharge you forenergy use.
• Single-phase power– What you have in
your houses– Single-phase 120-
volt AC service– 1 prong delivers
electrons toappliance
– 1 prong deliverselectrons to theground.
• 1. Power plant– Generator, Steam
Turbine• 2.Transmission
Substation• 3.Power Substation• 4.Transformer Drum• 5.Tap
Top Related