CHAPTER 15
RENEWABLE ENERGY

I. Principles of Solar Energy

A. Where Does it Originate?
B. How Much Solar Energy Reaches the Earth?

II. Direct Solar

A. Water Heating

1. Passive Solar
a. Benefits
·Economic
·Environmental
b. Costs
·Economic
·Environmental
c. What is passive solar's future?

2. Active Solar
a. Benefits
·Economic
·Environmental
b. Costs
·Economic
·Environmental
c. What is active solar's future?

B. Space Heating

1. Passive Solar
a. Benefits
b. Costs
c. What is passive solar's future?

2. Active Solar
a. Benefits
b. Costs
c. What is active solar's future?

Fig. 15.4 A mix of sources of renewable energy provided 7.6% of the nation's energy use in 1997.
Fig. 15.5 Equal amounts of energy are found in the visible-light and infrared regions of the solar spectrum.
Fig. 15.6 Flat-plate solar collector. As it is absorbed by a black surface, sunlight is converted to heat. A clear glass or plastic window over the surface allows the sunlight to enter but traps the heat. Air or water is heated as it passes through tubes embedded in the black surface.
Fig. 15.7 Solar water collector. In nonfreezing climates, simple water-convection systems may suffice. If freezing occurs, antifreeze is circulated.
Fig. 15.8 Solar collectors can save homeowners on fuel bills. Air heated in the collector moves in by passive convection.
Fig. 15.9 Large, Sun-facing windows permit sunlight to enter during winter months. Insulating drapes are drawn to hold in the heat when the Sun is not shining. Suitable overhangs, awnings, and deciduous plantings will prevent excessive heating in the summer.
Fig. 15.10 In summer, the house may be shaded with deciduous trees or vines. In winter, leaves drop, and the bare trees allow the house to benefit from sunlight. Evergreen trees on the opposite side protect and provide insulation from cold winds
C. Electricity Production

1. Technologies
a. Photovoltaic cells
b. Solar through collectors
c. Experiment technologies

2. Costs
a. Economic
b. Environmental

3. Benefits
a. Economic
b. Environmental

4. What is the future of electricity production using solar?

Fig. 15.13 Research and development has brought the price of photovoltaic cells down about 50-fold in the past 25 years. As prices have come down, sales have increased dramatically.
III. Indirect Solar

A. Hydrogen Fuel
1. How does it work?
2. Negative net energy and why solar is suggested as a source of energy
3. Prospects - What is the future?
4. Costs
a. Economic
b. Environmental
5. Benefits
a. Economic
b. Environmental

B. Hydropower
1. How does it work?
2. Prospects - What is the future?
3. Costs
4. Benefits

C. Wind Power
1. How does it work?
2. Prospects - What is the future?
3. Costs
4. Benefits

D. Biomass Energy

1. Technologies
a. Burning firewood
b. Burning wastes
c. Producing methane
d. Producing alcohol

2. Prospects - What is the future?
3. Costs
4. Benefits

Fig. 15.18 The fuel cell accomplishes the reaction of hydrogen and oxygen through stages such that their high potential energy creates an electric potential.   The only byproduct is water, the same as when burning hydrogen and oxygen.
Fig. 15.22 The total power needs for the Mason-Dixon Dairy, located in Pennsylvania, are obtained as a byproduct of cow manure, and nutrients are recycled in the process. Excess power, nearly half of what is produced, is sold to the local utility.
IV. Other Renewable Energy Options

A. Geothermal Energy
1. How does it work?
2. Prospects - What is the future?
3. Costs
4. Benefits

B. Tidal Power
1. How does it work?
2. Prospects - What is the future?
3. Costs
4. Benefits

C. Ocean Thermal Energy Conversions
1. How does it work?
2. Prospects - What is the future?
3. Costs
4. Benefits

V. Policy for a Sustainable Energy Future
Fig. 15.24A Direct solar heating of space and hot water, photovoltaic cells, solar-trough collectors, wind power, production of hydrogen from solar or wind power offer the potential for supplying sustainable energy with a minimum of environmental impact.
Fig. 15.24B In addition to direct and indirect solar energy sources, production of methane from animal manure and sewage sludges seem to offer the potential for supplying sustainable energy with a minimum of environmental impact.
Fig. 15.24C Additional alternative energy sources.