Chapter 18
Renewable Energy Sources
Cleaner Cars, Cleaner Fuels



Cars release a lot of pollution
2005
 Bush administration
 7% improvement in
mileage
 22.2 mpg
 2020 30.5 mpg
Diesel engines need work
Cleaner Cars, Cleaner Fuels



Energy Policy Act of 2005
 Tax credits
 Energy-efficient autos
Liquid hydrogen as a
fuel
What does the future
hold?
Electrical Generation Costs
Direct Solar Energy




Energy directly from the sun
Tremendous amount
Always available
Must be collected
Active Solar Heating



Collectors absorb solar energy
Pumps or fans distribute heat
Primarily for heating water
Passive Solar Heating





No mechanical devices to distribute
heat
New home design
Room temperature
is steady
Convection
Save on heating!
A Passive Solar Home
Photovoltaic (PV) Solar Cells




Convert sunlight into electricity
Thin wafers or films
No pollution
Minimal maintenance
Photovoltaic (PV) Solar Cells



Can be used in remote areas
Good choice for developing countries:
why?
School, home use
Photovoltaic (PV) Solar Cells



Can look like conventional roofing
Prices are coming down
Future progress is critical
Solar Thermal Electric
Generation




Sun’s energy concentrated by mirrors,
lenses
Heat a working fluid
Fluid is circulated to
boil water
Steam generates
electricity
Solar Thermal Electric
Generation




Backup system needed
Very efficient
No pollution
produced
Must be costcompetitive
Hydrogen As A Fuel Source






Could be the fuel of the future
Where does the hydrogen come from?
Electrolysis
Must use renewable fuel source to
obtain the hydrogen!
Few pollutants produced when burned
Can be used for transportation
Solar-Generated Hydrogen





Use PV cells for electrolysis of water
Currently not very efficient
Still expensive
Would need new distribution system for
transportation
Future development is critical
Solar-Generated Hydrogen

Fuel cells
 Electrochemical cell
 Like a battery
 Major carmakers working on it
Indirect Solar Energy


Indirect use of sun’s energy
Biomass, wind power, hydroelectricity
Biomass Energy





Wood, plants, animal wastes
Potentially renewable: why?
Burned to release energy
Half of human population
relies on
Cooking, heating
Biogas





Mixture of gases
Similar to natural gas
Animal wastes
Biogas digesters
 Decompose wastes
 Use gas for cooking, lighting
 Solid remains are fertilizer
Can also be used to power fuel cells
Biogas Digester
Biomass As A Liquid Fuel



Methanol, ethanol
Gasohol: mix gasoline and ethanol
Biodiesel
 Plant, animal oils
 Becoming more popular
 Burns cleaner than regular diesel
Ethanol




Sugarcane, corn, wood, agricultural and
municipal wastes
Government subsidizes
Good outlet for some wastes
Problems
 Land and water use
 Soil erosion
 Decreased food production
Wind Energy







Fastest growing energy source
No waste, emissions
Electricity
Costs are declining
Denmark is a world
leader
Need steady winds
Great Plains of U.S.
Wind Power Is On The Rise!
Wind Energy Problems


Birds and bats killed by turbines
 Avoid migration routes
 Operate only at certain times
 Monitor the project
Visual pollution
 Maple Ridge, NY
 Massachusetts coast
Hydropower




Flowing or falling
water spins turbines
Most efficient way to
produce electricity
19% world’s electricity
2200 U.S. plants
Hydropower Problems








Damages ecosystem, species
Displaces people: Three Gorges Dam
High construction cost
Reduces downstream flow
Reservoirs eventually fill in
Danger of collapse
Degrades river
Increase in waterborne disease:
schistosomiasis
Geothermal Energy



Use energy from Earth’s interior
Big potential source
Electricity
 Hydrothermal reservoir: hot fluid
 Bring fluid to surface to generate
electricity
Geothermal Energy
Geothermal Energy



Emits very few pollutants
Is it truly renewable?
Land may subside
Geothermal Heat Pumps







Used for heating and cooling
Ground temperature relatively constant
Underground pipes carry water
Fluids circulate
Expensive to install
Use is on the increase: why?
Very efficient!
Tidal Energy




Use power of the tides to generate
electricity
France, Russia, China, Canada
Very few ideal locations
May be damaging to ecosystems
Conservation & Efficiency



Energy conservation
 Using less energy
 Reduce use, waste
 Carpooling
Energy efficiency
 Using less energy for a task
 More fuel-efficient cars
Both very important!
Energy Consumption Trends


Use is on the increase
Greatest increase in developing
countries: why?
Energy-Efficient Technologies



Appliances, automobiles, light bulbs,
furnaces, etc…
“Superinsulated” buildings
May cost more, but will save money!
Energy-Efficient Technologies


National Appliance Energy Conservation
Act
 Sets national standards
 Much greater efficiency today
Invest in energy improvements now to
save money in the long run
Automobile Efficiency



Has improved since 1970s: why?
Increased use of minivans, trucks, SUVs
Efficiency must continue to improve
Cogeneration



Combined heat and power (CHP)
Recycling “waste” heat
Generate electricity, use steam before
cooling it back down
Electric Companies & Energy
Efficiency




Make more money, generate less
electricity
Incentives for conservation
Help consumers save electricity
 Light bulbs, furnaces
Company doesn’t have to invest in new
power generation
Electric Companies & Energy
Efficiency



Use cogeneration to save energy
Improve electricity grids
 Some energy lost in transmission
Plan for future use
Energy Conservation At Home





Average household: $1500/year on
utilities
Use energy-efficient technologies
Better insulation, windows
Seal cracks
Replace inefficient appliances
Energy Conservation At Home