Renewable Electricity

Using Solar Energy to Generate High-Temperature Heat and Electricity Solar Concentrators Deserts Mirrors can focus sunlight to heat up an oil or molten salt which is used to boil water Construction costs are high Some birds mistake the mirrors for water

Producing Electricity with Solar Cells Photovoltaic (PV) cells can provide electricity for a house of building using solar energy roof shingles. Video Solar cells can be used in rural villages with ample sunlight who are not connected to an electrical grid to do a lot.

Where Can We Use Solar? This map shows the amount of solar energy in hours, received each day on an optimally tilted surface during the worst month of the year. This map shows the amount of solar energy in hours, received each day on an optimally tilted surface during the worst month of the year

PRODUCING ELECTRICITY FROM WIND Wind power is the world’s most promising energy resource because: it is abundant renewable cheap clean, emits no greenhouse gases Wind turbines can be used individually to produce electricity. Many wind turbines make up a wind farm.

ELECTRICITY FROM WIND The United States once led the wind power industry, but Europe now leads this rapidly growing business. Why? The U.S. government lacked subsidies, tax breaks and other financial incentives. Which country was the first to use wind turbines to produce commercial electricity in 1890? Denmark

GEOTHERMAL ENERGY Geothermal energy consists of heat stored in soil, underground rocks, and fluids in the earth’s mantle. Can heat and cool buildings Can produce electricity What is magma? Video

Largest group of Geothermal Power plants in the World? The country that is the world's largest producer of geothermal electricity is _____ Second Place (first loser): Philippines Largest group of Geothermal Power plants in the World? The Geysers in Northern California A complex of 22 geothermal power plants located in the Mayacamas Mountains 72 mi north of San Francisco. The Geysers has an average production of 955 MW USA!!!

Generating Geothermal Electricity Dry Steam Power Plants: Underground steam is piped directly from the ground to the generators. (example: The Geysers) Dry steam: water vapor with no water droplets. (only 2 sources in USA) Flash Steam Power Plants Use geothermal reservoirs of hot water (>360°F) that rises to the surface under its own pressure. (Most common) Wet steam: a mixture of steam and water droplets. Binary Cycle Power Plants Use lower temperature water (225-360°F) to heat a low boiling point fluid to produce steam Water is injected back into ground to be reheated ***Most common new type***

DAMS AND RESERVOIRS Pros: Cons: cheap electricity reduce downstream flooding provide year-round water for irrigating crops Cons: displaces people (floods upstream) disrupt aquatic sys. –sometimes, the river stops flowing to the ocean, runs out of water Expensive to build

Provides water for year-round irrigation of cropland Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Provides water for drinking Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Risk of failure and devastating downstream flooding Can produce cheap electricity (hydropower) Figure 14.13 Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important? Downstream flooding is reduced Migration and spawning of some fish are disrupted Fig. 14-13a, p. 317

Powerlines Reservoir Dam Powerhouse Intake Turbine Figure 14.13 Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important? The world’s 45,000 large dams capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow.

Tidal Power Tidal Barrage: a dam that at high tide fills up one side with water, low tide release water and spins a turbine. Bay of Fundy (Nova Scotia)

Tidal stream power: under water stream currents spin a turbine. New York’s east river

Comparing Energy Sources As low as 12 cents now for solar cells

Contribution to total energy consumption (percent) Nuclear Coal Natural gas Oil Wood Hydrogen Solar Contribution to total energy consumption (percent) Figure 17.34 Science, economics, and politics: shifts in the use of commercial energy resources in the United States since 1800, with projected changes to 2100. Shifts from wood to coal and then from coal to oil and natural gas have each taken about 50–75 years. Note that, since 1800, the United States has shifted from wood to coal to oil for its primary energy resource. A shift by 2100 to increased use of natural gas, biofuels, hydrogen gas produced mostly by solar cells, and wind is one of many possible scenarios. (Data from U.S. Department of Energy) Year Fig. 17-34, p. 413