Environmental Science Chapter 18: Renewable Energy

Chapter 18 Targets I can list six forms of renewable energy, and compare their advantages and disadvantages. I can describe the difference between passive solar heating, active solar heating, and photovoltaic energy. I can describe the current state of wind energy technology. I can explain the differences in biomass fuel use between developed and developing nations. I can describe how hydroelectric energy, geothermal energy, and geothermal heat pumps work.

Renewable Energy Renewable energy: energy from sources that are constantly being formed Types of renewable energy: Solar energy (3 Ways) Wind energy Kinetic energy of moving water (3 Ways) Earth’s heat

Solar Energy can be used 3 ways: Solar Heating Solar Heating  Electricity Solar Energy  Electricity

Solar Hot Water 1890: solar water heaters used in sunny states like California, Arizona, and Florida 1920: 1,000’s of solar water heaters had been sold. BUT … large deposits of oil and natural gas were discovered in western United States. These low cost fuels became available, solar water systems were replaced with heaters burning fossil fuels. Solar collector for heating water A home in California in 1906

Today, solar water heaters making a comeback (more than half a million in California alone!) Heat water for use inside homes/businesses and swimming pools (see picture) Panels on building’s roof contain water pipes. Sun hits panels and pipes. Warmed water then used in a swimming pool

Passive vs. Active Solar Heating Active Solar Heating System Video

Solar Thermal Electricity Solar energy  electricity Some solar power plants (see picture from California's Mojave Desert) use curved mirrors called parabolic troughs to focus sunlight on a pipe running down center of mirror. Mirror focuses sunlight on pipe, causing water inside to boil and produce steam. Steam is then used to turn a turbine to make electricity.

SOLAR THERMAL ELECTRICITY

Solar Thermal Electricity PROBLEM: Works only when sun is shining. On cloudy days/at night, power plants can't create energy. Some solar plants, use "hybrid" technology During day they use sun. At night/cloudy days they burn natural gas to boil the water to generate electricity.

Another form of solar power (heat) to make electricity: (Central Tower Power Plant)  Sunlight is reflected off 1,800 mirrors (heliostats) circling the tall tower. A fluid (liquid sodium) is heated by the sun's rays. That fluid is used to boil water to make steam to turn a turbine and a generator. This experimental power plant is called Solar II and was built in the Mojave desert.

Solar Cells or Photovoltaic Energy Sunlight converted directly to electricity using solar cells Solar cells also called photovoltaic cells (PV cells); can be found on many small appliances, like calculators, and even on spacecraft First developed in 1950’s for U.S. space satellites; made of silicon, a special type of melted sand Sunlight strikes solar cells and electrons are knocked loose. They move toward treated front surface. When the two surfaces are joined by a wire, a current of electricity occurs between the negative and positive sides. Solar cells  PV module  Array Some arrays are set on special tracking devices to follow sunlight all day long.

Solar energy is stored in batteries to light roadside billboards at night or for emergency roadside cell phones when no telephone wires are around Some experimental cars also use PV cells - convert sunlight directly into electricity to power motors on the car Solar cells are used in satellites in outer space - see the picture of solar panels extending out from a satellite

Biomass Energy Biomass = waste from organisms Dead trees, branches, yard clippings, left-over crops, wood chips, bark and sawdust from lumber mills (even manure) Trash that can't be recycled  landfill Using biomass for fuel cuts down need for "landfills" to hold garbage Energy from Biomass Video

Biomass to Electricity 60 million tons of biomass (amount produced by most states) 2,000 megawatts of electricity (enough for 2 million homes!) How biomass works: Biomass gathered in big trucks Waste taken to biomass power plant Biomass fed into furnace and burned Heat used to boil water, and steam turns turbines and generators

Landfill Gas Biomass can also be “tapped” at landfills (LANDFILL GAS) 1. Garbage decomposes  methane gas 2. Pipelines collect methane gas that is used in power plants to make electricity Similar thing can be done at animal feed lots / places where many animals are raised. When manure decomposes  methane gas  burned at the farm to make energy to run the farm. Landfill Gas to Electricity Video

The Future of Biomass Biomass is renewable because plants can be grown over and over Another use of biomass is ethanol, a liquid alcohol fuel Ethanol is used in special cars designed to use alcohol fuel instead of gasoline The alcohol can also be combined with gasoline (gasohol) and reduce our dependence on oil

Geothermal Energy "Geo" = earth "thermal" = heat Below earth’s crust, top layer of mantle is hot liquid rock called magma. For every 328 feet below ground, temperature increases 5.4oF. At 10,000 feet below ground, the temperature is hot enough to boil water. Deeper under the surface, hot water can reach temperatures more than 300oF (hotter than boiling water 212oF). It doesn't turn to steam because it is not in contact with the air. Geysers? (Old Faithful pictured at right)

Geothermal Today In U.S., we geothermally heat water in swimming pools and health spas Hot water from below ground can be used to heat buildings during winter. The hot water runs through insulated pipes to public buildings. Iceland has at least 25 active volcanoes and many hot springs and geysers, this country uses the most geothermal energy globally Geothermal Energy in Iceland Video

Geothermal Electricity Steam from below ground  electricity in geothermal power plant Holes drilled into ground and pipes lowered into steam Steam comes up through pipes Steam causes turbine blades to spin and a generator to make electricity Steam is cooled off in cooling tower and pumped back below ground to be reheated by the earth

Hydroelectricity Hydroelectric power  kinetic energy of moving water  electricity Dams built across large rivers Hydro power today is found in mountainous areas of states where there are lakes and reservoirs and along rivers Washington state leads nation in hydroelectricity 87% is produced by hydroelectric facilities Hydroelectricity Video

How a Hydro Dam Works Water behind dam flows through intake into pipe called a penstock Water pushes against blades in a turbine Turbine spins a generator to produce electricity. The electricity travels via electric lines to homes, schools, factories and businesses

Ocean Energy 3 basic ways to tap ocean for energy: Waves High and low tides Temperature differences in the water

Wave Energy Moving waves  Kinetic energy Wave turbine: Wave rises into a chamber. Rising water forces air out of chamber. Moving air spins a turbine which turns a generator. When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed. Most wave-energy systems are very small. They can be used to power a warning buoy or a small light house. Wave Energy Animation

Tidal Energy An increase of at least 16 feet between low tide to high tide is needed for tidal electricity to be generated directly. When tides come into shore, they may be trapped in reservoirs behind dams. When the tide drops, water behind the dam can be let out just like a hydroelectric power plant. Tidal Power Video

Ocean Thermal Energy Conversion (OTEC) Uses temperature differences in the ocean. Sun warms surface water more than deep ocean water. OTEC plant produces energy using the following steps: Warm surface water is boiled in a vacuum chamber. This produces a steam that drives a turbine to generate electricity. Cold deep-ocean water will condense the steam. The steam turns into water that can be used again. OTEC Video

Renewable Energy Pro’s No shortage of renewable energy from the sun, wind and water and even stuff usually thought of as garbage (biomass). Sunlight falling on U.S. in one day contains more than 2X energy we consume in an entire year. California has enough wind gusts to produce 11% of world's wind electricity) Less pollution Renewable energy resource development  new jobs for people and less oil we must buy from foreign countries Continued research has made renewable energy more affordable than 25 years ago. Cost of wind energy has dropped from 40¢ per kilowatt-hour to less than 5¢. Cost of solar electricity, through photovoltaics has dropped from more than $1/kilowatt-hour in 1980 to 20¢/kilowatt-hour today.

Renewable Energy Con’s Takes up a lot of land: Solar thermal energy (huge mirrors) needs large tracts of land as a collection site. Average wind farm requires 17 acres of land to produce one megawatt of electricity, enough electricity for 750 to 1,000 homes. However, farms and cattle grazing can use the same land under the wind turbines. The environment is also impacted when the buildings, roads, transmission lines and transformers are built. A renewable power plant doesn’t release air pollution or use fossil fuels, it can still have a negative impact on the environment: Making PV cells uses toxic chemicals Wind farms cause erosion in desert areas and affect natural views because they tend to be located on or just below ridgelines. Bird deaths also occur due to collisions with wind turbines and wires. Dams used in hydroelectric power cause farmland and forests to flood. Downstream, dams change the chemical, physical and biological characteristics of the river and land.