Energy Efficiency
Energy Efficiency There are many different forms of energy. Most of our household Sound appliances convert electrical energy into some other useful form of energy. Mechanical Heat Chemical Gravitational Light
Energy Efficiency There are many different forms of energy. Most of our household appliances convert electrical energy into some other useful form of energy. Electrical
Energy Efficiency There are many different forms of energy. Most of our household appliances convert electrical energy into some other useful form of energy. Electrical
Energy Efficiency There are many different forms of energy. Most of our household appliances convert electrical energy into some other useful form of energy. Stove Light Bulb Electricity Heat Electricity Light Stereo Electricity Sound
Energy Efficiency There are many different forms of energy. Most of our household appliances convert electrical energy into some other useful form of energy. These energy conversions are never 100% efficient. For example, an incandescent light bulb that receives 100 Joules of electrical energy does not convert all of it into light energy. Only 10% of the electrical energy is converted into light. Light Bulb Are there more efficient bulbs? Light Heat Sound Light Heat Sound
Energy Efficiency There are many different forms of energy. Most of our household appliances convert electrical energy into some other useful form of energy. These energy conversions are never 100% efficient. For example, an incandescent light bulb that receives 100 Joules of electrical energy does not convert all of it into light energy. Only 10% of the electrical energy is converted into light. Yes! Light Bulb Light Heat Sound Light Heat Sound
Energy Efficiency There are many different forms of energy. Most of our household appliances convert electrical energy into some other useful form of energy. These energy conversions are never 100% efficient. For example, an incandescent light bulb that receives 100 Joules of electrical energy does not convert all of it into light energy. Only 10% of the electrical energy is converted into light. Light Bulb Light Heat Sound Light Heat Sound
ELECTRICAL POWER The rate at which electrical energy is produced or consumed in a given time. Unit of Measurement: Watt (W) 1 W = 1J/s The higher the Wattage the more energy energy uses to run.
60 W Incandescent Light bulb
15 W compact fluorescent bulb (CFL)
The 60 W incandescent light bulb uses more electrical energy than the CFL to produce light. However, each bulb produces the same amount of light.
Measuring Electrical Energy Usage We measure large amounts of electrical energy using the kilowatt-hour kilowatt-hour: the use of one kilowatt of power in one hour
Efficiency The measure of how much useful energy an electrical device produces compared with the amount of energy that is supplied to the device.
Example An old clothes dryer might use 800kW.h of energy in one year, while a newer model might use 300 kw.h in one year.
Example Both clothes dryers perform the same task, but the newer model is more efficient b/c it uses less electrical energy than the older model.
EnerGuide Labels Found on all appliances sold in Canada Ex. Stoves, dishwashers, refrigerators, washers, and dryers Provides an estimate of how much electrical energy the appliance will use in one year
EnerGuide Labels Tell How much electricity the appliance consumes in one year How the appliance compares with other similar appliances in terms of electricity consumption
Energy Star Labels Created in 1972 by the U.S. Environmental Agency Appliances that use 10% to 50% less energy compared to other appliances of the same make and model
Percent Energy Efficiency To determine how energy efficient an electrical device is, we have to know how much electrical energy the device uses (input) and how much energy is actually converted into a useful form (output). The following formula can be used to calculate the percent energy efficiency: Percent Energy Efficiency = Useful Energy Output Total Electrical Energy Input X 100 % Useful Energy Output is the amount of electricity that is converted into a useful form (such as heating water in a kettle or producing light from a bulb). Total Electrical Energy Input is the total electrical energy used by the electrical device.
Example Science Power 9 pg. 346 An electric kettle has a power rating of 1000W. It takes the kettle 4.00 min. to heat 600 ml of water from 22.0 ºC to 100ºC. If it takes 1.96 X 10 5 J of energy to heat the water, what is the efficiency of the kettle? G: P = 1000 W t = 240 s R: A: Percent efficiency =? S: To find total electrical energy input use the following equation: E = P X t E = 1000 W X 240 s = 240 000 J = 2.40 x 10 5 J S: Percent efficiency = Percent efficiency = Useful energy output Total electrical energy input 1.96 X 105 J 2.40 x 10 5 J Useful energy output = 1.96 X 10 5 J X 100 % X 100 % = 81.7 % The kettle is about 81.7 % efficient when heating 600 ml of water from 22.0 ºC to 100ºC.
Example #2 A light bulb uses 100J of electrical energy and produces 35 J of light energy. Calculate the percent efficiency of the light bulb. G: E out = 35J E in = 100J R: % efficiency =? A: E output % efficiency = E input X 100 % S: = 35J 100J X 100 % = 35% S: The efficiency of the light bulb is 35%
On your own A taster oven uses 1200J of energy to produce 850J of thermal energy. Calculate the % efficiency of the toaster oven. G: E out = 850J E in = 1200J R: % efficiency =? A: E output % efficiency = E input X 100 % S: = 850J 1200J X 100 % = % S: The efficiency of the light bulb is %
Calculating Cost Cost to operate = Power used x Time X cost of electricity
Calculating Cost A laptop computer uses 75W adapter when it is plugged in. electricity costs 5.6 c/kw.h. Calculate ho much it would cost to operate the laptop for 1 year for 24 hours per day. G: P = 75 W = 0.075kW t = 24hrs = 8760 hours R: A: Cost to operate=? Cost to operate = Power used x Time X cost of electricity S: = 0.075kW X 8760 hr X 5.6 c/kw.hr = 3679 c or $36.79 S: IT would cost $36.79 to operate a laptop computer for 24 hrs per day for 365 days