Alternative Energy Chapter 18

Solar Energy  Renewable Energy Source  Found every where at least part of the year.  Three (3) Types: –Passive Solar Heating –Solar Water Heating –Solar Cells

Passive Solar Heating  How it works: –Build your home facing south. –Large, double pane windows. –Thick walls & insulation on north side. –Concrete, adobe or stone construction. –Venting for hot air out during summer. –Drapes in winter to keep heat in at night. –Deciduous trees planted on south side  Block sunlight in summer  Allow sunlight in winter

Passive Solar Heating

 ADVANTAGES –Free energy –Renewable –Clean –Safe  DISADVANTAGES –Unattractive –Is there enough available sunlight in all areas? –Construction costs –Requires backup heat source

Solar Water Heating  How it works: –“Solar Collectors” on roof  Pipes with water or anti-freeze are coiled through box on roof.  Heated water transferred to basement.  Heat exchanged to fresh water; water pumped back to roof to be reheated.

Solar Water Heating

 ADVANTAGES –Free energy –Renewable –Clean –Safe  DISADVANTAGES –Unattractive –Is there enough available sunlight in all areas? –Requires a backup hot water source

Solar Cells (Photovoltaics)  How it works: –Converts sunlight to electricity! –Sunlight strikes semi-conductor –Electrons are excited and move; creates electricity. –Energy can be stored in a chemical battery for use when sunlight is absent.

Photovoltaics (Solar Cells)

Solar Cells  ADVANTAGES –Free energy –Renewable –Clean –Safe  DISADVANTAGES –Expen$ive! –Need large surface area –Unattractive –Is there enough available sunlight in all areas? –Requires a backup electricity source

Wind Energy  How it works: –Sunlight heats Earth’s surface –Warm air rises; cooler air replaces it (wind) –Wind (mechanical E) turns giant blades –Connected to a generator; creates electricity

Wind Energy  ADVANTAGES –Free energy –Renewable –Clean –Well developed technology –Electricity is cheaper per watt than coal produced.  DISADVANTAGES –Unattractive –Few regions with consistent winds –Noisy –Interfere with microwave communications –Harm birds & wildlife

Wind Energy

Hydroelectricity  How it works: –Dam is constructed to make a reservoir –Need height change to create enough power of moving water –Flowing water through dam turns turbines, turns generator, makes electricity

Hoover Dam

Hydroelectricity  ADVANTAGES –Free energy –Renewable –Clean –Flood control –Reservoir for recreation & irrigation  DISADVANTAGES –Disrupts ecosystems & floods upstream land –Tremendous environmental damage during construction –Dam construction is extremely expensive –Limited to areas with rivers & streams

Geothermal Energy  How it works: –Uses Earth’s heat to create steam to make electricity –Hot Dry Rock Method  Pump cold water below ground  Turns to steam  Extract pressurized steam  Turns turbine, turns generator, creates electricity

Geothermal Energy

 ADVANTAGES –Free energy –Potentially Renewable*** –No greenhouse gases –Minimal environmental damage during set-up  DISADVANTAGES –Limited availability on Earth. –Earth takes a long time to replace the heat.***

Biomass  How it works: –Burn organic matter to produce heat –Examples:  Wood (#1 fuel in world usage)  Municipal Waste (garbage)  Sugar cane (Hawaii)  Chicken droppings –Convert to other products  Corn to ethanol (gasoline additive)

Waste to Energy Plant

Biomass  ADVANTAGES –Reduces “wastes” –Renewable –Conserves fossil fuels –Sell extra electricity to public  DISADVANTAGES –CO 2 emissions –Noxious gases released –Who wants to live near a plant that burns trash or chicken poop?

Tidal Energy  How it works: –Offshore Turbines  Similar to underwater windmills –Tidal Barrage  Similar to hydroelectric dams

Offshore Turbines

Tidal Barrage

Tidal Energy  ADVANTAGES –Free energy –Renewable –Clean (non- polluting)  DISADVANTAGES –Affects ecosystems –Unattractive –Expensive to build –Affects shipping

Energy Concepts & Efficiency

Introductory Energy Concepts  Energy –“The ability to do work”.  KEY CONCEPT! –The amount of energy in the universe is constant.

Six (6) Forms of Energy  Mechanical –The energy of moving things.  EX: wind, moving water  Electrical –The energy of moving electrons  Heat –The energy of temperature change  Hotter temperatures can do more work.

Six (6) Forms of Energy  Light –The energy of moving photons  Chemical –The energy stored in the bonds between atoms.  EX: food, wood, gasoline, batteries, coal, oil…  Nuclear –The energy stored between the subatomic particles  EX: Nuclear power plants

Kinetic vs. Potential Energy  Kinetic Energy –The energy of something moving. –EX: Ball rolling down a hill.  Potential Energy –Stored energy; can be moved and used when needed. –EX: Ball on the edge of a hill.

Kinetic vs. Potential  At Top = 100% potential  At Bottom = 100% kinetic

1 st Law of Thermodynamics  “Conservation of Energy Law” –Energy can neither be created nor destroyed.  Energy in the universe is constant.  If you can’t destroy energy, you CAN change its form! –EX: Matches –EX: Light Bulb

2 nd Law of Thermodynamics  “Energy Quality Law” –When energy changes form, some useful energy is always degraded to lower quality, less useful energy.  Low temperature heat is the least useful energy form! –EX: 90% of energy in gas (chemical) is changed to heat!

Energy Efficiency  Net Energy –Total E – (E input & wasted E)  Energy Efficiency –% of total E that does work. –Wasted energy reduces E efficiency  Life cycle costs –Initial energy costs + lifetime operating costs

Electricity  The movement of electrons.  Created by moving a conducting material (copper wire) through a magnetic field.  “Electric Generator”

Coal & Turbine Pictures