Laws of Thermodynamics• 1st law: Conservation of Energy
• Energy cannot be created nor destroyed• Energy can be transferred from one system to another
• 2nd law: • Energy transfer must only have one direction• Entropy (disorder) increases over time
• 3rd law:• Absolute zero is achieved when all kinetic energy stops
SO…..• 1st law of Thermodynamics
• Explains how we can convert energy from chemical or mechanical energy to usable electric energy
• windmill animation
• 2nd law of Thermodynamics explains WHY energy efficiency can be so low
Solar
• Solar energy is harnessing energy from the sun’s rays• Passive Solar – Placing buildings strategically to
take advantage of the sun’s heat• Example: Log Homes
• Active Solar – uses solar panels to convert energy into a usable form such as electricity
Fig. 17-17, p. 398
Single solar cellSolar-cell roof
–
Boron enriched silicon
+
Junction
Phosphorus enriched silicon
Roof options
Panels of solar cells
Solar shingles
• Benefits of Solar:• Readily available• Renewable• Fairly simple system• Pollution free energy source• Can sell back extra energy to the power company
• Drawbacks of Solar:• High start up cost for active solar energy system• Location dependent (Seattle would not be a good
city for solar energy)
Core Case Study: The Coming Energy-Efficiency and Renewable-Energy Revolution
• It is possible to get electricity from solar cells that convert sunlight into electricity.• Can be attached like shingles on a roof.• Can be applied to window glass as a
coating.• Can be mounted on racks almost
anywhere.
Core Case Study: The Coming Energy-Efficiency and Renewable-Energy Revolution
• The heating bill for this energy-efficient passive solar radiation office in Colorado is $50 a year.
Figure 17-1Figure 17-1
Passive Solar Heating
• Passive solar heating system absorbs and stores heat from the sun directly within a structure without the need for pumps to distribute the heat.
Figure 17-13Figure 17-13
Fig. 17-13, p. 396
Direct Gain
Summer sunHot air
Warm air
Super-insulated windows
Winter sun
Cool air
Earth tubes
Ceiling and north wall heavily insulated
Fig. 17-13, p. 396
Greenhouse, Sunspace, or Attached Solarium
Summer cooling vent
Warm air
Insulated windows
Cool air
Fig. 17-13, p. 396
Earth Sheltered
Reinforced concrete, carefully waterproofed walls and roof
Triple-paned or superwindowsEarth
Flagstone floor for heat storage
Fig. 17-14, p. 396
Trade-Offs
Passive or Active Solar Heating
Advantages Disadvantages
Energy is free Need access to sun 60% of time
Net energy is moderate (active) to high (passive)
Sun blocked by other structures
Need heat storage system
Quick installation
No CO2 emissions
Very low air and water pollution
High cost (active)
Very low land disturbance (built into roof or window)
Active system needs maintenance and repair
Moderate cost (passive)
Active collectors unattractive
Cooling Houses Naturally
• We can cool houses by:• Superinsulating them.• Taking advantages of breezes. • Shading them.• Having light colored or green roofs.• Using geothermal cooling.
Wind• Wind energy is converted into a usable energy form by using
wind turbines
www.lacoastpost.com www.windenergyplanning.com
Wind Power
• Benefits of Wind Power:• Readily available• Can sell back extra power• Pollution free energy source
• Drawbacks of Wind Power:• Disrupts migration patterns• Turbine farms are not aesthetically pleasing• Turbines are expensive• Good for specific locations only
Hydro
• Hydro power is mechanical energy derived from water
• Most hydropower is generated by damming rivers
• Using waves or ocean currents is being researched as a source of hydropower
www.southeastasia.biz
Three Gorges Dam
• 1.5 miles long • 574 feet deep • $23 billion• 13 cities and 1,300 villages were flooded
• Benefits of Hydropower• Readily available• No pollution produced• Constant source of power
• Drawbacks of Hydropower• Damming rivers disrupts ecosystems, causes
sediment to build up and disrupts the natural flow of a river
Geothermal
• Geothermal energy uses natural underground heat sources
• When heat escapes the earth in the form of steam, the steam is used to turn a steam turbine which converts the heat energy into electrical energy
• Benefits of Geothermal:• When drilled correctly, little pollution is produced• Takes up a relatively small area, does not disrupt
the landscape• Drawbacks of Geothermal:
• Can only be used in a limited capacity• Very location specific• May run out of steam• May release hazardous gasses or minerals if
drilled improperly
Biomass
• Biomass is burning biomass fuel in a specialized burner. Steam generated turns a steam turbine which turns mechanical energy into electrical energy
Biomass at the Denver Zoo!• Trash and animal
waste is converted into pellets
• The pellets are put into a gassifier and heated to 400 degrees!
• When hot enough, a gas is emitted that is converted by micro gas turbines into electrical energy
• Denver Zoo
• Benefits of Biomass• Less waste in landfillsReadily available
• Drawbacks of Geothermal• Not currently available on a large scale basis
USING RENEWABLE SOLAR ENERGY TO PROVIDE HEAT AND ELECTRICITY
• The European Union aims to get 22% of its electricity from renewable energy by 2010.
• Costa Rica gets 92% of its energy from renewable resources.• China aims to get 10% of its total energy from renewable
resources by 2020.• In 2004, California got about 12% of its electricity from wind
and plans to increase this to 50% by 2030.