Generating Current Electricity Review

Hydroelectric Power Hydro-electric generating stations use fast-moving water from a river or a waterfall, or water stored in a reservoir behind a dam. As water flows it moves the blades on a turbine, which is connected to an electrical generator. RENEWABLE

Tidal Energy RENEWABLE Tides from ocean water rotate a water turbine which is connected to an electrical generator. RENEWABLE

Thermal Energy -Steam is produced by heating water. -The steam is used to rotate a turbine to generate electricity. -The energy to heat the water can come from a variety of sources.

Fossil Fuels NON-RENEWABLE Fossil fuels are formed from plants, animals, and micro-organisms that lived millions of years ago (e.g. coal, oil and natural gas). When they are burned they produce energy. NON-RENEWABLE

Radioactive Materials Long tubes are filled with uranium and placed inside a reactor. Neutrons collide with the uranium causing nuclear fission. The uranium atoms split apart releasing energy. NON-RENEWABLE

Biomass Biomass is any biological material (including plants and animals). Biomass can be burned or methane gas (released from decaying plant and animal matter) can be collected and burned as fuel. RENEWABLE

Geothermal Energy Uses the thermal energy from deep in the Earth. Liquid goes through pipes in the ground and are heated by the Earth’s thermal energy. The hot liquid then heats water in a tower to create steam. RENEWABLE

Wind Energy Wind turns a wind turbine that is connected to an electrical generator. RENEWABLE

Solar Energy A photovoltaic cell (solar cell) converts light directly into electrical energy. RENEWABLE

Electrical Power & Efficiency

What is Electrical Power? Electrical power is the rate at which electrical energy is produced or consumed in a given time Unit of Measurement for Power: Watt (W) The higher the ‘wattage’, the more electrical energy a device produces OR uses to operate 1 W = 1 joule per second (J/s)

Measuring Energy Usage J/s is a very small unit so for larger amounts of electrical energy we use: watt•hours (W•h) kilowatt•hours (kW•h) gigawatt•hours (GW•h) kW•h is the standard unit for measuring electrical energy usage It is 1000 times greater than W•h, while GW•h is 1 000 000 times greater than kW•h 1 kilowatt = 1,000 Watts

Efficiency When we transfer energy from gas, wind or water into electricity, some energy is lost Efficiency A measure of how much useful energy an electrical device produces compared with the amount of energy that was supplied to the device Some appliances are more efficient at using more of the electrical energy they receive than others For example, a new clothes dryer might use 300 kW•h in 1 year while an older model uses 800 kW•h VS.

Consider… A 60 W incandescent light bulb uses more electrical energy than a 15 W compact fluorescent light bulb, but they produce the same amount of light VS. Where does the remaining energy used by the incandescent light bulb go? Energy is converted into thermal energy (heat) instead of light!

EnerGuide & Energy Star Labels A label to inform consumers of the estimated electrical energy consumption (kW•h) an appliance will use in a year The Energy Star symbol is used to identify the products that meet the minimum level of efficiency

Calculating the Efficiency of a Device ENERGY OUT Percent Efficiency = × 100% ENERGY IN Energy OUT (Eout)= A measure of how much useful energy the device puts out to do its task Energy IN (Ein)= A measure of how much energy the device requires

Practice Problem #1 A light bulb uses 100 J of electrical energy and produces 35 J of light energy. Calculate the percent efficiency of the light bulb. Given: Eout = 35 J Ein = 100 J % efficiency = ? Eout % efficiency= × 100% Ein 35 J 100 J % efficiency= × 100% Therefore the efficiency of the light bulb is 35% % efficiency= 0.35 × 100% % efficiency= 35%