1. Chapter 13 Renewable Energy and Conservation

2. Overview of Chapter 13 Direct Solar Energy Indirect Solar Energy
Heating Buildings and Water
Solar Thermal Electric Generation
Photovoltaic Solar Cells
Indirect Solar Energy
Biomass Energy
Wind Energy
Hydropower
Other Renewable Energy Sources
Geothermal Energy
Tidal Energy
High and Low Technology Energy Solution
Hydrogen and Fuel Cells
Energy Efficiency

3. Direct Solar Energy
Varies with latitude, season, time of day, and cloud cover
Current technology…

4. Heating Buildings and Water
Passive solar energy
system of putting the sun’s energy to use without requiring mechanical devices to distribute the collected heat
Certain design features can enhance passive solar energy’s heating potential
South facing windows (in N. hemisphere)
Well insulated buildings
Attic vents
Overhangs and solar sunspaces
Why don’t more homes have passive solar energy technology?

6. Solar sunspace Utilizes passive solar energy to heat and cool homes
Can be added to existing homes

7. Heating Buildings and Water
Active Solar Energy
System of collecting and absorbing the sun’s energy, and using pumps or fans distribute the collected heat
Most common
Series of collection devices on roofs or in fields
Typically a black panel or plate
Used to heat water

8. Heating Buildings and Water
Solar Thermal Electric Generation
Means of producing electricity in which the sun’s energy is concentrated by mirrors or lenses to either heat a fluid filled pipe or drive a Stirling engine
Examples…
More efficient than other solar technologies
Benefits
No air pollution
No contribution to global warming or acid precipitation

9. Solar Thermal Electric Generation
Solar thermal plant in CA – uses troughs to focus sunlight on fluid filled tube…

10. Photovoltaic Solar Cells
Thin cells are treated with certain metals so that they generate electricity when they absorb solar energy
Convert sunlight directly into energy
Pros:
No pollution, minimal maintenance
Used on any scale
Lighted road signs
Entire buildings
Cons:
Not very efficient
Requires a great deal of land

11. Photovoltaic Solar Cells
Benefit to utility companies
Rural areas in developing countries– it is more economical to use PV solar cells
Future - can be incorporated into building materials
Roofing shingles
Tile
Window glass

12. Cost of Electrical Power Plants
Other technologies…
Indirect Solar Energy
Combustion of biomass
Wind energy
Hydropower

13. Indirect Solar Energy Biomass Can convert to biogas or liquids
Plant materials used as fuel
Ex: wood, crop wastes, sawdust, and animal wastes
Contains energy from sun via photosynthesizing plants
Renewable when used no faster than it can be produced
Can convert to biogas or liquids
Ethanol and methanol
Pros and cons…

14. Advantages and Disadvantages of Biomass
Reduces dependence on fossil fuels
Often uses waste materials
If trees are planted at same rate biomass is combusted, no net increase in atmospheric CO2
Disadvantages
Requires land, water and energy
Can lead to
Deforestation
Desertification
Soil erosion

15. Indirect Solar Energy Wind Energy
Electric or mechanical energy obtained from surface air currents caused by solar warming of air
World’s fastest growing source of energy
Wind results from sun warming the atmosphere
Varies in direction and magnitude
New wind turbines harness wind efficiently

16. Wind Energy Kills birds and bats Cost Public resistance
Most profitable in rural areas with constant wind
Few environmental problems
Kills birds and bats
No waste- clean source of energy
Biggest constraints
Cost
Public resistance

17. Indirect Solar Energy Hydropower
Form of renewable energy reliant on flowing or falling water to generate mechanical energy or electricity
Sun’s energy drive hydrologic cycle
Most efficient energy source (90%)

18. Hydropower Generates 19% of world’s energy Traditional hydropower
Only suited for large dams
New technology
May be able to utilize low flow waterways
Impacts of Dams
Changes natural flow of rivers
Disrupts migratory fish patterns
Potential dam breaks

19. Three Gorges Dam
1990s China began work on the Three Gorges Dam (TGD), which will meet several goals:
Designed to produce electricity equivalent to 18 nuclear power plants or large coal power plants  advantage because air pollution is a concern in China
Agricultural productivity downstream will be optimized
Will be used for transportation, commercial fishing and recreation
Range of problems associated w/ building dams…
China had difficulty finding investors – since uncertainty about design, construction and effectiveness was so great

20. Other Indirect Solar Energy
Ocean waves
Produced by winds
Has potential to turn a turbine- and create electricity
Ocean Temperature Gradients
Use difference in temperature of surface and deep water to create electricity

21. Other Renewable Energy Sources
Geothermal Energy
Energy from the Earth’s interior for either space heating or generation of electricity
Typically associated with volcanism
From Hydrothermal Reservoirs (right)
Created by volcanoes
Reservoirs used directly for heat or to generate electricity
Renewable?
Environmentally benign?

22. Geothermal Energy From hot, dry rock Geothermal heat pumps
Technology exists but is expensive
Geothermal heat pumps
Use difference in temperature between surface and subsurface
Great for heating buildings
Expensive installation

23. Other Renewable Energy Sources
Tidal Energy
Form of renewable energy that relies of the ebb and flow of the tides to generate electricity
Typical difference between high and low tide is 1-2 ft but range can be higher
Narrow bays may have greater variation
Energy can be captured with
A dam across the bay
A turbine similar to a wind turbine

24. Energy Conservation vs. Energy Efficiency
Human requirements for energy will continue to increase as the population increases and as developing countries raise their standards of living
Energy conservation – using less energy by reducing energy use and waste, for example
Example…
Energy efficiency – using less energy to accomplish a given task, as for example with new technology
Important environmental benefits from greater energy efficiency and conservation:
Using energy efficient appliance could reduce CO2 emissions by millions of tons each year (slowing climate change)
Reduce air pollution, acid precipitation and other environmental damage

25. Hydrogen as a Fuel Source
H2 contains large amounts of available energy
Gas at RT, liquid when cooled to -435 ˚F
Explode when combined with the O2  releasing energy and forming water
Advantages to Hydrogen as a fuel source
Very high energy density
Can be produced from any electrical source
Electrolysis (see illustration on next slide)
No greenhouse gases and few other pollutants
Can be use in vehicles
Disadvantages to Hydrogen as a fuel source
Highly volatile (requires special storage)
Relatively inefficient

26. Hydrogen as a Fuel Source- Electrolysis

27. Hydrogen Fuel Cell Fuel cell
Device that directly converts chemical energy into electricity
Requires hydrogen from a tank and oxygen from the air
Similar to a battery, only the reactants are supplied from outside source

28. Applications of Fuel Cells
Although technology is improving, not commonly available
Vehicles
Not yet commonly available
Hydrogen is not yet readily available as a fuel source
Batteries in cells phones or laptops

29. Energy Consumption Trends and Economics
Lower energy intensity – implies economy is more energy efficient as it generates wealth
Energy Trends in Developing Countries
Per capita energy consumption is substantially less in developing countries than in industrialized countries

30. Energy Efficient Technologies
Compact Fluorescent light bulbs
Condensing furnaces
Super-insulated buildings (right)
Energy efficient appliances
National Appliance Energy Conservation Act (NAECA)
Automobiles
Aircraft technology

31. Cogeneration
Production of two useful forms of energy from the same fuel
Cost effective on small or large scale…

32. Energy Savings in Commercial Buildings
Energy services companies often offer their assistance so that businesses make little or no financial outlay
How does this work?

33. Electric Power Companies and Efficiencies
Traditionally to meet future power needs, electric utilities planned to build new power plants or purchase additional power from alternative sources
Now they avoid these large expenses by demand-side management – help electricity consumers save money by reducing energy costs
How?
Improvements:
US electric power plants are important target for improved energy efficiency – much heat is lost during generation of electricity
Improve our electric grids – about 10% of electricity is lost during transmission right now

34. Saving Energy at Home