Chapter 21

• Germany produces more than 6% of its electricity from solar power — one of the highest rates in the world
• Feed-in tariff system


  Utilities have to buy electricity from anyone on the grid who can produce it from renewable sources
• This has led to homeowners and businesses installing solar roof panels
• Renewable Energy Sources Act of 2000


  Assigned a payment rate according to market considerations for every renewable energy source
• Germany is gradually lowering its tariffs, until a goal of about 52 gigawatts of capacity is reached
• Since 1990, carbon dioxide emissions from German energy sources have fallen by 25%, and emissions of seven other major pollutants (CH4, N2O, SO2, NOX, CO, volatile organic compounds, and dust) have been reduced by 12–95%
• Germany has shut down 7 of its 15 nuclear power plants in response to the Fukushima meltdown in 2011, which increased the rate of coal combustion
• Advantages of new renewables

  • Reduction in air pollution
  • Reduction in greenhouse gas emissions that drive global climate change
  • Diversification of an economy's energy mix
• Although prices are falling, most renewable energy remains more expensive than fossil fuel energy
• Market prices will continue to fall for renewable energy the more it is used
• Policies to encourage transition to renewables

  • Mandates set by governments that a minimum percentage comes from renewable sources
  • Government investment in research and development
  • Tax credits and rebates to individuals and businesses who produce or buy renewable energy
• Together, oil and gas have received 75 times more subsidies and nuclear power has received 31 times more than new renewable energy sources
• The Earth receives enough solar energy each day to power human consumption for 25 years
• Passive solar energy collection

  Designing buildings to maximize absorption of sunlight in winter while keeping the interior cool in the heat of summer
• Thermal mass


  Materials that absorb, store, and release heat slowly, used to build the roof, walls, and floor
• Active solar energy collection

  Using devices to focus, move, or store solar energy
• Flat plate solar collectors


  Dark-colored, heat-absorbing metal plates mounted in flat glass-covered boxes that absorb solar heat from the roof and transfer it to hot water tanks inside the building
• Concentrated solar power (CSP)


  Intensifies solar energy by gathering it from a wide area and focusing it on a single point
• Parabolic trough approach


  Uses curved mirrors to focus sunlight onto synthetic oil in pipes, which is then used to heat water into steam, which then drives turbines
• Power tower facilities


  Receive sunlight concentrated by mirrors and transfer the heat to steam-driven generators
• Photovoltaic (PV) cells


  Convert sunlight directly to electrical energy through the transfer of electrons across silicon plates
• Benefits of solar energy

  • It is an inexhaustible energy source for human use
  • No fuel is needed
  • There are no moving parts, so little maintenance is required
  • No greenhouse gases or other pollutants are emitted
• Drawbacks of solar energy

  • Not all regions are equally sunny
  • Solar energy is an intermittent resource, preventing it from providing a consistent energy supply without storage capacity
  • Solar energy has a high up-front cost of purchasing and installing equipment
• Due to lack of government investment in past decades, solar energy contributes just 0.56% of the U.S. energy supply
• PV technology is the fastest growing power source today, having recently doubled every two years
• China is currently the world leader in solar technology, subsidizing its production so much that it is driving U.S. manufacturers out of business
• Passive solar heating


  Designing a home with a south-facing porch to allow winter sunlight in for warmth, and surrounding it with broadleaf trees to provide cooling shade in the summer
• The initial investment costs for setting up a solar collection system are high
• Wind power


  Generated from the movement of air caused by differentially heated air masses
• Wind turbines


  Convert the mechanical energy of wind into electrical energy
• Wind power capacity is doubling every three years
• When ranked by what proportion of their electricity comes from wind, smaller countries like Denmark, Ireland, and Portugal lead the way
• Offshore wind farms


  Can be ideal because the wind speed is greater and the air is less turbulent, although initial costs are higher
• Limitations of wind power

  • Wind is an intermittent resource that we cannot directly control
  • The geography of the landscape determines how much wind power is available
  • Residents often oppose wind farms near population centers for aesthetic reasons, creating a not-in-my-backyard (NIMBY) syndrome
  • Wind turbines pose a threat to birds and bats, which are killed if they fly into the rotating blades
• Geothermal energy


  Thermal energy that arises from beneath Earth's surface
• Geothermal power plants


  Use heated underground water and steam to generate electricity
• Ground-source heat pumps


  Transfer heat from the ground during the winter, and back into the ground during the summer
• Wind energy has a high EROI ratio
• Geothermal energy always requires access to hot springs
• Fuel cells


  Use hydrogen to generate electricity, and are three times more efficient than internal combustion engines