Chapter 13 Renewable Energy and Conservation
I. Direct Solar Energy
• A. Perpetually available – we will only run out when the sun’s nuclear fire burns out – found all over the earth
• B. Varies with latitude, season, time of day, and cloud cover
• C. Heating Buildings and Water
– 1. Passive solar energy
• System of putting the sun’s energy to use without requiring mechanical devices to distribute the collected heat
– 2. Certain design features can enhance passive solar energy’s heating potential – can save as much as 50% on heating costs – more expensive to install (about 7% of new homes have this)
• South facing windows (in N. hemisphere)
• Well insulated buildings
• Attic vents
• Overhangs and solar sunspaces
– 3. Solar Sunspace
• Utilizes passive solar energy to heat and cool homes
• Can be added to existing homes
Typically used to heat water
8% of energy in US is used to heat water
This technology could supply large amount of US energy demand
– 4. Active Solar Energy
• System of collecting and absorbing the sun’s energy, and using pumps or fans distribute the collected heat
– 5. 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
– 6. More efficient than other solar technologies
• No air pollution
• No contribution to global warming or acid precipitation
Solar Thermal Electric Generation
• 7. Photovoltaic Solar Cells
– a. A wafer or thin film that is treated with certain metals so that they generate electricity when they absorb solar energy
b. No pollution and minimal maintenance
c. . Used on any scale
Lighted road signs
Entire buildings
d. currently provide 13,000 MW of electricity worldwide = 13 large nuclear power plants
• e. Can be incorporated into building materials – Roofing
shingles
– Tile
– Window glass
e. More economical than running electrical lines to rural areas
II. Cost of Electrical Power Plants
• A. Alternative power sources are becoming competitive with traditional power sources
III. Indirect Solar Energy
• A. Biomass
– Plant materials, such as wood, crop wastes and animal waste, used as fuel
• B. Wind energy
– Electric or mechanical energy obtained from surface air currents caused by solar warming of air
• C. Hydropower
– Form of renewable energy reliant on flowing or falling water to generate mechanical energy or electricity
IV. Biomass
• A. Contains energy from sun via photo-synthesizing plants – Oldest known fuel to humans - still used by half the
world’s population – Renewable when used no faster than it can be
produced
B. Can convert to biogas or liquids
Ethanol and methanol
Clean fuel
• C. Advantages – 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
• D. Disadvantages – Requires land, water and fossil fuel energy – Can lead to
• Deforestation • Desertification • Soil erosion
V. Wind Energy
• A. World’s fastest growing source of energy
• B. Wind results from sun warming the atmosphere
– Varies in direction and magnitude
• C. New wind turbines harness wind efficiently
– Most profitable in rural areas with constant wind
• E. No waste - clean source of energy
• F. Biggest constraints: – Cost
– Public resistance (NIMBY)
D. Few environmental problems
Kills birds and bats
VI. Hydropower
• A. Most efficient energy source (90%)
• B. Most widely used form of solar energy – sun powers the water cycle
– 19% of world’s energy
• D. traditional hydropower
– Suited only to large dams
• E. New technology
– Utilize low flow systems
Hydropower
VII. Other Indirect Solar Energy
• A. Ocean waves
– Produced by winds
– Has potential to turn a turbine- and create electricity
• B. Ocean Temperature Gradients
– Use difference in temperature of surface and deep water to create electricity
VIII. Other Renewable Energy Sources
• A. Geothermal energy
– Energy from the Earth’s interior for either space heating or generation of electricity
• B. Tidal Energy
– Form of renewable energy that relies of the ebb and flow of the tides to generate electricity
A. Enormous energy source
1% of heat in upper 10 km of earth crust is equal to 500x the earth’s fossil fuel sources
IX. Geothermal Energy
• B. From Hydrothermal Reservoirs
– Created by volcanoes
– Reservoirs used directly for heat or to generate electricity
• C. From hot, dry rock – fracture the rock and then run water into the fractures to make an artificial reservoir – Ex. New Mexico
• D. Geothermal heat pumps
– Use difference in temperature between surface and subsurface
– Great for heating buildings
– Expensive installation
X. Tidal Energy
• A. Typical difference between high and low tide is 1–2 ft
– Narrow bays may have greater variation
• B. Potential energy difference between low and high tide can be captured with
– A dam across a bay
– A turbine similar to a wind turbine
XI. High and Low Technology Energy Solutions
• A. Most promising “energy sources” are energy conservation and energy efficiency
• B. Energy Conservation
– Using less energy by reducing energy use and waste
• C. Energy Efficiency
– Using less energy to accomplish a given task
XII. Hydrogen as a Fuel Source
• A. Hydrogen gas (H2)
– Comprised of two hydrogen molecules
– Large amounts of available energy
– Explodes when combined with oxygen releasing energy and forming water
• B. Advantages
– Very high energy density so it could be used for gasoline in automobiles and other forms of transportation unlike coal and nuclear energy
– Can be produced from any electrical source
• Electrolysis (see illustration on next slide)
– No greenhouse gases and few other pollutants
• C. Disadvantages
– Highly volatile (requires special storage)
– Relatively inefficient
Hydrogen as a Fuel Source - Electrolysis
D. 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, but reactants are supplied from outside source
E. Future Applications of Fuel Cells
• Hydrogen Fuel Cell Vehicles – Hydrogen is not yet
readily available as a fuel source • 61 hydrogen
fueling stations in US
• Batteries in cell phones or laptops
XIII. Energy Consumption Trends and Economics
XIV. Energy Efficient Technologies
• Super-insulated buildings (right)
• Energy efficient appliances
• Automobiles
• Aircraft technology
• Compact Fluorescent
light bulbs
• Condensing furnaces
XV. Cogeneration
• Production of two useful forms of energy from the same fuel – generation of electricity through some thermal process (often natural gas); the residual low-temp. steam left over after electricity production is used for building or industrial heating
– Most effective on small scale
XVI. Energy Savings in Commercial Buildings
XVII. Saving Energy at Home