cost effectiveness matter
Cosr effectiveness of different appliances we must consider a number of different costs
-cost of buying the appliance
-cost of installing the appliance
-the interest charged on a loan to by the appliance
householdes want to reduce their energy bills,to do this they may buy more efficient apliances
payback time is the time it takes for appliance or installation to pay for itself in terms of energy savings
fuel for electricity
in most power stations, water is heated to produce steam.
the steam drives a turbine which is coupled to an electrical generator that produces the electricty
the eneregy can come from burning a fossil fuel such as coal,oil or gas. fossil fuels are obtained from long-dead biological material
in some gas fired power stations, hot gases may drive the turbine directly, a gas fired turbine may be switched on very quickly
biofuels are renewable sources of energy which can generate electricity
in a nuclear power station,the fue used is uranium
nucleus of uranium atom can undergo a process called nuclear fission
this process releases energy
energy from wind and water
energy from wind,waves and tides is called renewable energy.
we can use energy from wind and water to drive turbines directly
in a wind turbine the wind passing over the blades makes them rotate and drive a generator at the top of a narrow tower
electricity can be produced from energy obtained from falling water, waves or tides.
hydroelectric power, at ther power station water is collected in a reservoir. this water is allowed to fow downhill and turn turbines at the bottom of the hell. in a pumped storage system, the energy is stored..then at times of high demand the water can be released to fall through the turbines and transfer the stored energy to electrical energy
waves on the sea to generate electricity, the movement drives a floating turbine that turns a generator. then the electricity is delivered to the grid system on shore by a cable
the level of the sea around the coastline rises and falls twice each day.
these changes in sea level are called tides. if a barrage is built across a river estuary the water at each high tide can be trapped behind it. when the water is released to fall down to the lower sea level,it drives turbines
power from the sun and the earth
Solar energy from the sun travels through space to the earth as electromagnetic radiation
a solar cell can transfer this energy into electrical energy.
each cell only produces a small amount of electricity so they are useful to power small devices such as watches and calculators
we can also join together large numbers of cells to form a solar panel
water flowing through a solar heating panel is heated directly by energy from the sun
a solar power tower uses thousands of mirrors to reflect sunlight onto a water tank to heat the water and produce steam.
geothermal energy comes from inside the earth