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

Renewable Energy

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 in China

www.livescience.com

Three Gorges Dam

• 1.5 miles long • 574 feet deep • $23 billion• 13 cities and 1,300 villages were flooded

www.howstuffworks.com

• 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.

Energy Efficiency – renewable energy sources• Solar• Wind• Hydro• Biomass• Geothermal

USING RENEWABLE SOLAR ENERGY TO PROVIDE HEAT AND ELECTRICITY

• Denmark now gets 20% of its electricity from wind and plans to increase this to 50% by 2030.

• Brazil gets 20% of its gasoline from sugarcane residue.

• In 2004, the world’s renewable-energy industries provided 1.7 million jobs.