sources, conserving energy & efficiency.notebook. December 15, Sources of Electrical Energy: How does a generator work?

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1 Sources of Electrical Energy Efficiency Cost of Electricity SNC 1P/D Sources of Electrical Energy: Energy comes in many different forms, including kinetic energy (energy of motion), chemical energy (energy stored in atoms & molecules), nuclear energy (energy stored in the nucleus of an atom), & electrical energy (electricity). All forms of energy can be converted into other forms. In Canada, most electrical energy is made by converting kinetic energy using a device called a generator. How does a generator work? The key parts of a generator system are a turbine, a shaft & the generator itself. When the turbine turns, it spins the shaft, which spins a rotor in the generator. The kinetic energy of the spinning rotor is converted into electrical energy inside the generator. What sources of energy are used to generate electrical energy? Any form of energy that can be used to turn a turbine can be used to generate electrical energy. The 3 main sources of energy used in Ontario are: 1. Hydroelectric (moving water) 2. Thermoelectric (burning fossil fuels) 3. Nuclear (heat from nuclear reactions of uranium atoms) A small portion of energy comes from the following sources as well: - Solar - Sunlight is converted directly into electricity by solar cells (in solar panels) - Wind - Moving air turns giant turbines which turn a generator - Geothermal - Hot rocks underground heat water to produce steam that turns a turbine generator - Biomass - Heat from burning organic material boils water to produce steam that turns a turbine generator What are renewable & nonrenewable energy sources? Renewable energy sources can be replaced or restocked within a human lifetime, or less. They include water, wind, the sun, biomass, tides & heat from below Earth's surface (geothermal). Nonrenewable energy sources, such as fossil fuels & uranium, cannot be replaced or restocked within a human life span. These sources of energy take from millions to billions of years to form. When all available supplies are used up, they are gone forever. Renewable energy sources - water - solar - wind - biomass - geothermal - tides Sources of Electrical Energy Nonrenewable Energy Sources - fossil fuels - uranium 1

2 Where Ontario Gets Its Electrical Power Electrical energy is a necessity in our every day lives. You depend on electricity for warmth, cooking food, preventing food spoilage, entertainment, household chores, & many other important activities in your life. Electrical Power rate at which electrical energy is produced or used. The unit of measurement for power is the watt which is equivalent to 1 J/s. is 1 million watts kw which A kilowatt hour is equivalent to 1000 watts used over one hour. e.g. 100 watt light bulb X 10 hours of use = 1000 watt hours or 1 kwh Most appliance have a label on them with the number of watts they use. The old style type of meter records the amount of electrical energy used continuously - 24 hrs a day, 365 days a year. The new smart meters measure energy use each hour. The meters encourage "smart" behavior on the part of Ontarians by giving the means to think about how & when we use electrical energy. 2

3 How are smart meters different? Smart meters are electronic & send the data automatically to the power-supply company; Smart meters allow power-supply companies to charge different rates for different times of day; Generally, there are 3 times for power usage - on-peak, midpeak & off-peak; The schedule for these times changes from summer to winter; Time-of-use prices are highest during on-peak use (when the most electrical energy is used) & lowest during offpeak use (when the least electrical energy is used). CFLs contain mercury, which is toxic, and so The amount of energy an appliance uses in a typical year is shown on an EnerGuide label. The large number shows how much energy the appliance uses in one year of normal use. The shaded bar below, shows how the appliance compares with similar ones on the market. The numbers on the bar give a range of efficiency for yearly energy use. The left end is lowest (most efficient) & the right end is highest (least efficient). 3

4 The government of Canada has set standards of efficiency for electrical appliances. Those that meet or exceed these standards have the ENERGY STAR* label for easy identification. Many electrical devices are on, even when you think they are switched off. They are in stand-by mode. The electrical energy that is used by a device when it is turned off is called the phantom load. Examples: If you have a remote control to turn on a television, the television must be able to sense the signal, & requires this energy; Clock displays (on microwave & coffee makers); External power adaptors - if they get warm when not in use, they are using power. Efficiency is a measure of how much useful energy( device produces compared to the amount of energy that was 2. Determine the percent efficiency of a 5000-W dryer if it uses 4500 kwh of energy to produce 750 kwh of R: % efficiency =? A: Eff = E out / E in x 100% Eff = 400 / 2000 x 100% Eff = 20% Therefore the light bulb is 20% efficient. 4

5 Cost of Electrical Energy rate. It is usually around $0.09/kWh. Sample Problems: /kwh. Calculate the cost to operate the laptop for 1 year bulb operating for 10 h. R: cost =? A: cost = P x t x unit cost cost = x 2190 x 5.6 = c cost = $9.20 Therefore it costs $9.20 to use the laptop for a year. 4. If a 0.5 kw washing machine is used for ½ hour each day what is the cost of operating the machine for a week if the /kwh? What is the cost for a month? Worksheets: 5