Renewable Energy

Passive Solar Energy: How it Works 1.System absorbs and stores heat from sun within well insulated structure 2.Walls & floors made of stone, adobe, brick, or concrete 3.Water tanks used to store collected solar energy as heat; slowly released heat throughout the day and night 4.Supplement heat with natural gas or propane heater

Fig a, p. 409 Superwindow Stone fl oor and wall for heat storage Passive Solar Energy White or light-colored roofs reduce overheating Vent allows hot air to escape in summer Summer sun Heavy insulation Winter sun Super- window

Passive Solar Home in Colorado Fig , p. 410

Active Solar Energy: How it Works 1. Capture energy from sun by pumping a heat absorbing fluid (water or antifreeze) through special collectors 2. Collectors may be located on the roof in special racks to face the sun 3. Some heat directly used 4. Some heat stored in insulated container with gravel, water, clay & used later 5. Used to heat water in many homes

Fig b, p. 409 Pump Active Solar Energy Solar collector White or light-colored roofs reduce overheating Heat to house (radiators or forced air duct) Heavy insulation Super- window Hot water tank Heat exchanger

Solutions: Passive and Active Solar Heating for a Home Fig , p. 409

Rooftop Solar Hot Water on Apartment Buildings in Kunming, China Fig , p. 410

Countries that Use Active Solar Heating Systems 1.Used mostly to heat water in residentail areas 2.China, Germany, Japan, Greece, Austria, & Turkey

Fig , p. 411 Advantages and Disadvantages of Passive or Active Solar Heating AdvantagesDisadvantages 1. Net energy is moderate (active) to high (passive) 1. Need access to sun 60% of time during daylight 2. Very low emissions of CO 2 and other air pollutants 2. Sun can be blocked by trees and other structures 3. High installation and maintenance costs for active systems 3. Very low land disturbance 4. Moderate cost (passive)4. Need backup system for cloudy days

World Availability of Direct Solar Energy Darker the color, the less available sunlight per kilowatt-hour per day

U.S. Availability of Direct Solar Energy The biggest limiting factor of solar thermal energy systems is the availability of WATER which is in short supply in areas that receive the greatest amount of solar power

Indianapolis Airport Solar Iniative Only receives moderate amount of sunlight for solar energy

Cooling Buildings Naturally Technologies available  Open windows when cooler outside  Use fans  Superinsulation and high-efficiency windows  Overhangs or awnings on windows  Light-colored roof  Geothermal pumps

We Can Use Sunlight to Produce High- Temperature Heat & Electricity 1. Solar thermal systems  Central receiver system  Collect sunlight to boil water, generate electricity  1% of world deserts could supply all the world’s electricity  Require large amounts of water – could limit  Wet cooling  Dry cooling 2. Low net energy yields

Solar Thermal Power in California Desert Fig , p. 411

Solutions: Solar Cooker in India Fig , p. 412

Solar Cell Array in Niger, West Africa Fig , p. 413

Solar-Cell Power Plant in Arizona Fig , p. 414

Global Production of Solar Electricity Figure 11, Supplement 9

Fig , p. 414 AdvantagesDisadvantages 1. Moderate net energy yield1. Need access to sun 2. Little or no direct emissions of CO 2 & other air pollutants 2. Need electricity storage system or backup 3. Easy to install, move around, and expand as needed 3. High costs for older systems but decreasing rapidly 4. Solar-cell power plants could disrupt desert ecosystems 4. Competitive cost for newer cells Advantages & Disadvantages of Solar Cells

Solar Thermal Concentrating Systems By using mirrors and lenses to concentrate the rays of the sun, solar thermal systems can produce very high temperatures—as high as 3,000 degrees Celsius. This intense heat can be used in industrial applications or to produce electricity. The water, at about 300 degrees Celsius, runs to a central collector (hot water tank), where it produces steam that drives an electric turbine.

We Can Produce Electricity from Falling and Flowing Water 1. Hydropower  Uses kinetic energy of moving water  Indirect form of solar energy  World’s leading renewable energy source used to produce electricity 2. The top 5 countries that use hydropower:  Canada, China, Brazil, U.S. & Russia 3. The Three Gorges Dam that spans the Yangtze River in China is the world’s largest hydroelectric dam.

Provides irrigation water above and below dam Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Provides water for drinking Deprives downstream cropland and estuaries of nutrient-rich silt Reservoir useful for recreation and fishing Risk of failure and devastating downstream fl ooding Can produce cheap electricity (hydropower) Reduces down- stream fl ooding of cities and farms Disrupts migration and spawning of some fish Advantages & Disadvantages of Dams & Reservoirs

Fig b, p. 328 Powerlines Reservoir Dam Intake Powerhouse Turbine

Fig , p. 415 AdvantagesDisadvantages 1. Moderate to high net energy 1. Large land disturbance & displacement of people 3. Low-cost electricity 2. High CH 4 emissions from rapid biomass decay in shallow tropical reservoirs 4. Low emissions of CO 2 and other air pollutants in temperate areas 3. Disrupts downstream aquatic ecosystems Advantages and Disadvantages of Large- Scale Hydropower 2. Large untapped potential

Tides & Waves Can Be Used to Produce Electricity 1. Produce electricity from flowing water  Ocean tides and waves 2. So far, power systems are limited  Only 2 large ones in operation 3. Disadvantages  Few suitable sites  High equipment costs  Damaged by storms and corrosion

Wind Power: an Important Step toward Sustainability 1. Wind: indirect form of solar energy  Wind is caused by different angles of sun’s rays hitting earth between equator and poles  Creates different amounts of solar heating  Coupled with Earth’s rotation, wind is created  Captured by turbines  Converted into electrical energy 2. Second fastest-growing source of energy 3. What is the global potential for wind energy? 4. Wind farms: on land and offshore

World Electricity from Wind Energy Figure 12, Supplement 9

Wind Turbine & Wind Farms on Land & Offshore Fig , p. 417 Wind turbines can be 22 stories tall (wind is more stable at that height) Blades on turbines can be as long as a 7 story tall building Countries that are the largest wind-power producers are: Germany, U.S., Spain, India, & Denmark

Fig , p. 418 Advantages and Disadvantages of Wind Power AdvantagesDisadvantages 1. Moderate to high net energy yield 1. Needs backup or storage system when winds die down 3. Low electricity cost 2. Visual pollution for some people 3. Low-level noise bothers some people 4. Can kill birds if not properly designed and located 2. Widely available 5. Easy to build & expand 4. Little or no direct emissions of CO 2 & other air pollutants

United States Wind Power Potential States with greatest wind potential: North Dakota, South Dakota, Kansas, Texas

Energy from Burning Solid Biomass 1. Biomass: Plant materials & animal waste we can burn or turn into biofuels 2. Production of solid mass fuel  Indirect form of solar energy because it is produced from photosynthesis  Plant fast-growing trees  Biomass plantations  Collect crop residues and animal manure 3. 10% of the World’s energy is supplied by biomass

Plants & Plant Wastes to Produce Liquid Biofuels 1. Liquid biofuels  Biodiesel  Ethanol 2. Biggest producers of biofuel  The United States  Brazil  The European Union  China

Advantages & Disadvantages of Biofuels over Gasoline & Diesel Fuel 1. Biofuel crops can be grown almost anywhere 2. No net increase in CO 2 emissions if managed properly 3. Available now AdvantagesDisadvantages 1. Increase soil degrading, erosion, & nutrient leaching 2. Raise food prices 3. Reduce water supplies, especially for corn & soy

Getting Gasoline & Diesel Fuel from Algae & Bacteria 1. Algae remove CO 2 ; convert it to oil  Not compete for cropland = not affect food prices  Wastewater/sewage treatment plants  Could transfer CO 2 from power plants 2. Algae challenges  Need to lower costs  Open ponds vs. bioreactors  Affordable ways of extracting oil  Scaling to large production

Geothermal Energy 1. Geothermal energy: heat stored in  Soil  Underground rocks  Fluids in the earth’s mantle 2. Geothermal heat pump system  Energy efficient and reliable  Environmentally clean  Cost effective to heat or cool a space 3. Is NOT a form of solar energy 4. The United States (California, Nevada, Utah, and Hawaii) is the largest producer of geothermal electricity from hydrothermal reservoirs

A Geothermal Heat Pump System Can Heat or Cool a House Fig , p. 425

Geothermal Sites in the United States Figure 26, Supplement 8

Fig , p. 426 AdvantagesDisadvantages 1. Moderate net energy & high efficiency at accessible sites 1. High cost & low efficiency except at concentrated & accessible sites 2. Lower CO 2 emissions than fossil fuels 2. Scarcity of suitable sites 3. Low cost at favorable sites 3. Noise & some CO 2 emissions Advantages & Disadvantages of Geothermal Energy

Hydrogen as a Fuel 1. Hydrogen as a fuel  Eliminate most of the air pollution problems  Reduce threats of global warming 2. Some challenges  Chemically locked in water and organic compounds = net negative energy yield  Expensive fuel cells are the best way to use hydrogen  CO 2 levels dependent on method of hydrogen production

A Fuel Cell Separates the Hydrogen Atoms’ Electrons from Their Protons Fig , p. 427

Fig , p. 428 Advantages & Disadvantages of Hydrogen as a Fuel AdvantagesDisadvantages 1. Can be produced from plentiful H 2 O at some sites Fuel cell 1. Negative net energy yield 2. CO 2 emissions if produced from carbon-containing compounds 2. No direct CO 2 emissions if produced from H 2 O 3. Good substitute for oil3. High costs require subsidies 4. High efficiency (45–65%) in fuel cells 4. Needs H 2 storage & distribution system