Energy Efficiency

What is Energy Efficiency? Energy efficiency refers to how effectively a device can transfer the energy it recieves to do the task it is designed for.For example, a solar panel takes solar energy and transforms it to electrical energy. If the solar panel was 100% efficient then it would turn all of the energy it recieves (input energy) to electrical energy (output energy). Unfortunately, no device is 100% efficient and we will always lose some energy to unwanted forms of energy, usually heat. On average a solar panel might recieve 1000 joules of solar energy. Most solar panels are about 20% efficient, this means that only 20% of the energy it recieves (in this case about 200 joules) will be transformed in to the desired output energy, electrical energy.See if you can identify the different types of energy involved in driving a car below: Input energy Chemical energy from petrol Desired output energy Kinetic energy Wasted output energy Heat Identify the sources of wasted energy in running a ceiling fan: Heat Light Sound Kinetic energy Identify the input energy for turning a wind turbine: Sound energy Kinetic energy Heat energy Electrical energy When riding a bike, what is the desired output energy? Sound energy Chemical energy from food Kinetic energy of the bike moving Heat energy of the tyres on the road We can calculate how energy efficient a device is by using the following equation:Energy efficiency = useful energy output / total energy outputThis equation will give you the energy efficiency as a decimal, to convert this to a percentage you must mulitply your answer by 100.A battery powered car uses 1800j of energy. Of this, 450j are transformed in to useful kinetic energy. What is the energy efficiency percentage of the battery powered car? 25% Abdul mows his lawn every month. His lawn mower uses 3200kj of chemical energy from the petrol Abdul puts in to it. This energy is converted to the following energy types:960kj in to kinetic energy1050kj in to sound energy1190kj in to heat energyWhat is the energy efficiency percentage of Abdul's lawn mower? 30% Examine the image of Australian tennis pro Ashleigh Barty. Categorise the energy types below as useful or wasted: Useful Kinetic energy of the racquet Kinetic energy of the player's body Kinetic energy of the ball Wasted Sound energy from the ball hitting the ground Heat energy from the friction between the ball and the ground