Environment 7/e

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Chapter 13Renewable Energy and Conservation
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Overview of Chapter 13

• Direct Solar Energy
• Indirect Solar Energy
• Wind
• Biomass
• Hydropower
• Geothermal
• Tidal
• High and Low Technology Energy Solution

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Direct Solar Energy

• Perpetually available
• Varies with latitude, season, time of day, and
  cloud cover

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Heating Buildings and Water

• Passive solar energy
• System of putting the suns energy to use without
  requiring mechanical devices to distribute the
  collected heat
• Certain design features can enhance passive solar
  energys heating potential
• South facing windows (in N. hemisphere)
• Well insulated buildings
• Attic vents
• Overhangs and solar sunspaces

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Solar Sunspace

• Utilizes passive solar energy to heat and cool
  homes
• Can be added to existing homes

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Heating Buildings and Water

• Active Solar Energy
• System of collecting and absorbing the suns
  energy, and using pumps or fans distribute the
  collected heat

• 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

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Heating Buildings and Water

• Solar Thermal Electric Generation
• Means of producing electricity in which the suns
  energy is concentrated by mirrors or lenses to
  either heat a fluid filled pipe or drive a
  Stirling engine
• More efficient than other solar technologies
• No air pollution
• No contribution to global warming or acid
  precipitation

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Solar Thermal Electric Generation

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Photovoltaic Solar Cells

• A wafer or thin film that is treated with certain
  metals so that they generate electricity when
  they absorb solar energy

• No pollution and minimal maintenance
• Used on any scale
• Lighted road signs
• Entire buildings

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Photovoltaic Solar Cells

• More economical than running electrical lines to
  rural areas

• Can be incorporated into building materials
• Roofing shingles
• Tile
• Window glass

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Cost of Electrical Power Plants

• Alternative power sources are becoming
  competitive with traditional power sources

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Indirect Solar Energy

• Biomass
• Plant materials, such as wood, crop wastes and
  animal waste, used as fuel
• Wind energy
• Electric or mechanical energy obtained from
  surface air currents caused by solar warming of
  air
• Hydropower
• Form of renewable energy reliant on flowing or
  falling water to generate mechanical energy or
  electricity

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Biomass

• Contains energy from sun via photo-synthesizing
  plants
• Oldest known fuel to humans - still used by half
  the worlds population
• Renewable when used no faster than it can be
  produced

• Can convert to biogas or liquids
• Ethanol and methanol
• Clean fuel

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Biomass

• 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
• Disadvantages
• Requires land, water and fossil fuel energy
• Can lead to
• Deforestation
• Desertification
• Soil erosion

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Wind Energy

• Worlds fastest growing source of energy
• Wind results from sun warming the atmosphere
• Varies in direction and magnitude
• New wind turbines harness wind efficiently
• Most profitable in rural areas with constant wind

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Wind Energy

• Few environmental problems
• Kills birds and bats

• No waste - clean source of energy
• Biggest constraints
• Cost
• Public resistance (NIMBY)

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Hydropower

• Most efficient energy source (90)
• Most widely used form of solar energy
• 19 of worlds energy
• Traditional hydropower
• Suited only to large dams
• New technology
• Utilize low flow systems

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Hydropower

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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

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Other Renewable Energy Sources

• Geothermal energy
• Energy from the Earths interior for either space
  heating or generation of electricity
• Tidal Energy
• Form of renewable energy that relies of the ebb
  and flow of the tides to generate electricity

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Geothermal Energy

• Enormous energy source
• 1 of heat in upper 10 km of earth crust is equal
  to 500x the earths fossil fuel sources

• From Hydrothermal Reservoirs
• Created by volcanoes
• Reservoirs used directly for heat or to generate
  electricity

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Geothermal Energy

• From hot, dry rock
• Geothermal heat pumps
• Use difference in temperature between surface and
  subsurface
• Great for heating buildings
• Expensive installation

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Tidal Energy

• Typical difference between high and low tide is
  12 ft
• Narrow bays may have greater variation
• Potential energy difference between low and high
  tide can be captured with
• A dam across a bay
• A turbine similar to a wind turbine

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High and Low Technology Energy Solutions

• Most promising energy sources are energy
  conservation and energy efficiency
• Energy Conservation
• Using less energy by reducing energy use and
  waste
• Energy Efficiency
• Using less energy to accomplish a given task

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Hydrogen as a Fuel Source

• Hydrogen gas (H2)
• Comprised of two hydrogen molecules
• Large amounts of available energy
• Explodes when combined with oxygen releasing
  energy and forming water

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Hydrogen as a Fuel Source

• Advantages
• 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
• Highly volatile (requires special storage)
• Relatively inefficient

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Hydrogen as a Fuel Source -Electrolysis

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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

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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 cells phones or laptops

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Energy Consumption Trends and Economics

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Energy Efficient Technologies

• Super-insulated buildings (right)
• Energy efficient appliances
• Automobiles
• Aircraft technology
• Compact Fluorescent
• light bulbs
• Condensing furnaces

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Cogeneration

• Production of two useful forms of energy from the
  same fuel
• Most effective on small scale

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Energy Savings in Commercial Buildings

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Saving Energy at Home