Chapter 16: Alternative Energy and the Environment

Overview Introduction to Alternative Energy Sources Solar Energy Converting Electricity from Renewable Energy into a Fuel for Vehicles Water Power Ocean Energy Wind Power Biofuels Geothermal Energy

Introduction to Alternative Energy Sources Nonrenewable alternative energy Nuclear Requires a mineral fuel mined from Earth Geothermal Heat is extracted faster than it is replenished Renewable energy sources Solar, fresh water, wind, ocean, and biofuels All derive from the sun’s energy

Solar Energy 10 weeks of solar energy equivalent to all known fossil fuel reserves Two types Passive Active

Passive Solar Energy Promotes cooling in hot weather and retaining heat in cold weather Methods include: Overhangs that block summer sun but allow winter sun Walls in buildings that absorbs heat during the day and releases it at night Deciduous trees as landscaping

Active Solar Energy systems that require mechanical power Electric pump circulate air, water or other fluids from solar collectors to a location where heat is stored Additional pumps move heat to location where energy is converted and used

Solar Collectors Provide space heating or hot water Flat Plate Collector Flat, glass-covered plates over a black background where absorbing fluid is circulated through tubes Evacuated tube collector Each tube filled with absorbing fluid pass through a larger tube

Photovoltaic Converts sunlight directly into electricity Made from thin layers of semiconductors and a solid-state electronic components with few or no moving parts World’s faster growing source of energy

Photovoltaic Off the grid Emerging as a major contributor to developing countries Don’t have ability to build a electrical grid Systems can power lights and televisions in small villages

Solar Thermal Generators Focus sunlight onto water-holding containers Traditionally built using solar power towers Water boils and is used to run conventional steam-driven electrical generators Built with very large output

Solar Thermal Generators In newer facility Mirrors focus solar energy onto pipes with heat-absorbing fluid

Solar Energy and the Environment Generally low impact One concern Variety of metals, glass plastics, and fluids used in the manufacture and use of solar equipment Production and accidental spills could release toxic materials

Converting Electricity from Renewable Energy to a Fuel that can be Burned and can Power Vehicles Two choices: Store electricity in batteries and use electric vehicles Transfer the energy in the electricity to a gaseous or liquid fuel Hydrogen

Hydrogen Fuel Hydrogen as power for fuel cells Electric current separates water into hydrogen and oxygen When H recombined with O, electrons flow between positive and negative poles An electric current H Can be transported in pipeline Combustion product is water Clean fuel

Water Power A form of stored solar energy Long history Waterwheels convert water power to mechanical energy Today’s hydroelectric power plants use water stored behind dams Also produced through the process of pump storage

Small-Scale Systems Electrical power produced by large dams will not increase Most dam sites already utilized Small scale systems have potential in mountainous areas along streams

Water Power and the Environment Advantages Water power is clean and efficient power No burning of fuel, no radioactive waste Disadvantages Flood large tracts of land Block fish migration Trap sediment that would replenish beaches Evaporative loss of water from reservoirs

Ocean Energy High energy in motion of waves, currents and tides in the ocean Difficult to harness Storms destructive and water corrosive Most successful = tidal power Very few areas w/ the right topography

Tidal Power Dam built across the entrance to a bay or estuary Water held in or out of bay until significant difference in level forces water in or out This runs the turbines Environmental impacts Changes hydrology of bay Restricts passage of fish Changes habitat for birds and other organisms

Wind Power Wind produced when differential heating of Earth’s surface create air masses with differing heat contents and densities Wind energy is the cheapest form of alternative energy Less than natural gas and coal Now used in many place including offshore

Wind Power Problems Wind highly variable in time, place, and intensity Wind velocity often increases over hill tops or funneled through a mountain pass

Wind Power and the Environment Wind energy does have a few disadvantages Kills birds Use large areas of land May degrade area’s scenic resources

Future of Wind Power Growing at approximately 30% per year Nearly 10 times the growth rate of oil use Created thousands of jobs and investment opportunities Technology producing more efficient wind turbines

Biofuels and Human History Energy from biomass is the oldest fuel used by humans. Until end of 19th century major fuel source in the US 1 billion people in the world still use wood as primary source of energy for heat and cooking Includes: firewood, cattle dung, peat

Biofuels Energy recovered from biomass-organic matter Three groups Firewood Organic wastes Crops grown to be converted into liquid fuels

Biofuels and the Environment Can pollute the air and degrade the land World’s forests will decrease if our need for forest products and forest biomass fuel exceeds the productivity of the forests Combustion of biomass-derived fuel generally release fewer pollutants then combustion of coal/gasoline But burning urban waste can release heavy metals

Geothermal Energy Deep earth - high density Energy from interior of earth Mined and used to heat buildings and generate electricity May be considered nonrenewable when rates of extraction are greater than rates of natural replenishment Shallow earth - low density Solar energy that has traveled to shallow depths

Geothermal Systems Areas of high heat flow occur at plate boundaries Divergent and convergent plate boundaries Hydrothermal convection- transfers heat from depths to surface Using steam or hot water

Geothermal Most groundwater can be considered a source of geothermal energy Groundwater at a depth of 100m is 13oC or 55oF In summer heat can be transferred to the cool water In winter heat can be transferred from the water to the air

Geothermal Energy and the Environment Problems: Considerable thermal pollution from hot wastewaters Water may be saline or highly corrosive On-site noise Emissions of gas Disturbance of land

Future of Geothermal Energy Could produce 10% of the electricity needed for the western US Geohydrothermal Could potentially provide four times that (10% of US total)