1.1 Energy-consuming appliances at home Input and output Main sources of energy in Hong Kong Energy efficiency Check-point 1 1 2 Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home Input and output Does a rice cooker of power 450 W work at this rate? Unfortunately, this is only the power input. The actually power output is much less than this value. When you buy an electrical appliance, will you consider its efficiency? Book E3 Section 1.1 Energy-consuming appliances at home

1 Main sources of energy in Hong Kong Electricity is the main source of energy.  covers 50% of energy needs in Hong Kong  powers all sorts of appliances at home Gas (LPG or town gas)  2nd most popular source of energy in the home  mainly for cooking and water heaters Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home 2 Energy efficiency a Energy conservation When we use electrical appliances, many different energy conversions occur. e.g. Turn on a television light energy, sound energy and heat electrical energy Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home 2 Energy efficiency a Energy conservation When we use electrical appliances, many different energy conversions occur. e.g. Turn on a fan electrical energy kinetic energy and heat A lot of electrical appliances generate heat but… heat is not always the form of energy that we want. Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home 2 Energy efficiency b End-use energy efficiency End-use energy efficiency: The useful proportion of energy used End-use energy efficiency useful energy output energy input =  100% A high-efficiency appliance uses less energy to do the same job. Example 1 End-use energy efficiency of a kettle Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home 2 Energy efficiency c Overall energy efficiency End-use energy efficiency only tells the energy lost in operating an electrical appliance. How about the energy lost during generation and transmission of electricity? initial energy input power plant power transmission appliance initial energy output waste heat Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home 2 Energy efficiency c Overall energy efficiency Overall energy efficiency: Takes the efficiency of each step into account Overall energy efficiency final energy output initial energy input =  100% In Hong Kong, the efficiency of a power station: 34%–53% transmission: ~95% Example 2 Overall energy efficiency Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home Check-point 1 – Q1 Which form(s) of energy is electrical energy converted into when you use a power drill? A Kinetic B Sound C Heat D All of the above Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home Check-point 1 – Q2 End-use energy efficiency of a kettle = 93% If its useful output power is 1600 W, what is its input power? A 1720 W B 1693 W C 1488 W D 1120 W Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home Check-point 1 – Q3 Efficiency of a power station = 40% Efficiency of the transmission network = 90% Efficiency of an electric iron = 60% Overall energy efficiency = ? Overall energy efficiency = 40%  90%  60% = 21.6% Book E3 Section 1.1 Energy-consuming appliances at home

Book E3 Section 1.1 Energy-consuming appliances at home The End Book E3 Section 1.1 Energy-consuming appliances at home