Power from the Sun: Solar, Hydro and Wind Dennis Silverman U. C. Irvine Physics and Astronomy

Solar Power Most of all energy we use comes or has come from the sun. Fossil fuels arise from fossil plants and animals converted to carbon (coal), or hydrocarbons (methane and petroleum). We are 1/3 to 1/2 through the process of burning hundreds of millions of years of fossil fuel accumulations in two centuries.

Free Solar The sun would heat the planet to 0° Fahrenheit without the atmosphere. The sun runs the greenhouse that keeps the earth warmed up to an average of 58° F with the greenhouse gas atmosphere. It evaporates the oceans to provide the rain and fresh water for crops and drinking water and hydropower. It powers the weather to provide winds. It grows our crops and forests through photosynthesis Solar energy provides our daylight and moonlight. It heats our buildings in the daytime, and the sea and land hold heat for the night.

Pharoah Akhenaten and Queen Nefertiti Monotheism of Aten, the Sun, BC Possible father of Tutankhamen (King Tut)

Solar Manipulation The next best way to use solar is to modify its effects. –Reflective roofs to keep buildings cool –Reflective windows to keep out direct sunlight during the summer, and keep heat in during the winter –Windows and skylights for indoor daytime lighting

Paint Your House White? Santorini

Direct Solar Energy Mediterranean climates now using rooftop or nearby solar water heating – Greece, Israel, Japan. It is 80% efficient. Solar clothes drying

Solar Photovoltaic Electricity Silicon wafers doped to form photovoltaic cells –Power is free, but –Large wafers still thick and crystal grown as chips, so still expensive –Cost still 3 to 10 times as expensive as fossil fuel power –Efficiency only 10 to 15%, so large areas needed –Daily and yearly average only 1/5 of maximum power capacity installed –Don’t need storage if send excess power back over the grid –Storage could be in charging car batteries or in hydrogen fuel, or –Concentrate on using more energy during the daytime –Silicon valley investigating thin film disk technology to make cheaper

Unelectrified Areas Two billion people do not have electricity To save on kerosene lanterns, solar cells with batteries and lcd lights have been developed for nighttime lighting Also used to charge freeway phones

California’s Million Solar Roofs California SB1 (Senate Bill 1) to provide rebates to equip solar power installations Goal is 3 gigawatts solar by 2017 This could be 3 kw/household, at $9/watt is $27,000/household Companies rebated per kwh generated New homes must offer solar option by ,000 more homes can be added to generating electricity into the power network $2.8 billion CA cost, 30% Federal rebate, up to $18 billion total cost, but for less average electricity than a nuclear plant at $2-3 billion. Could only nearly pay if it brings down costs through economies of scale, or if it leads to technological breakthrough through research and competition Only $100 million for solar water heating

U. S. Solar Resources

U. S. Tracking Mirror Solar

Solar Trough Mirrors Suitable For Large Systems Grid-connected Power Grid-connected Power MW size Heats mineral oil to hundreds of degrees Then vaporizes a fluid to drive a turbine

Dish with Sterling Engine Modular Remote Applications Demonstration Installations High Efficiency Conventional Construction Heat expands gas and drives piston

Solar Tea? Tibet, Dreprung Monastery

Solar Tower Suitable For Large Systems Grid-connected Power MW size Potentially Lower Cost Potentially Efficient Thermal Storage Molten Salt heated, averages out solar input Can store heat overnight

Cost Of Energy* (Max Lechtman) TroughDish/EngineTower *Cents/kWh in 1997 $

Hydropower  Of the renewable energy sources that generate electricity, hydropower is the most often used. It accounted for 7 percent of total U.S. electricity generation and 75 percent of generation from renewables in 2004  Over one-half of the total U.S. hydroelectric capacity for electricity generation is concentrated in three States (Washington, California and Oregon) with approximately 27 percent in Washington, the location of the Nation’s largest hydroelectric facility – the Grand Coulee Dam

How Hydropower Works

World-wide, about 20% of all electricity is generated by hydropower.

Glen Canyon Dam and Power Station

Aswan Dam on the Nile River

Wind Power - Mykonos

Clipper Ship

World Wind Capacity. Total now 74 Gigawatts worldwide, with 65% in Europe. Market growing at 32% a year. 3.3% of European electricity now from wind. 1% of U.S. electricity.

Wind Generation Physics  Power proportional to the cube of the wind velocity.  (v² from Bernoulli pressure for force on wingshaped propeller, times a distance per second of rotating propeller, which is proportional to v.)  Most of energy from small bursts.  ½ of energy comes in 15% of the time.  Average capacity factor is 35% of the maximum.  Wind turbines best spaced 3-5 times the rotor diameter perpendicular to the wind, and 5-10 times the diameter parallel to the wind.

Virginia’s “Switzerland” Wind Power Proposal  39 towers of 400 feet height  $2 million per tower at 1 megawatt So about a 40 megawatt peak project  Enough power for 15,000 homes x 12,000 kwh/yr / 9,000 hours/year = 20 million watts average Implies a 50% duty cycle  To compare to a 1 gigawatt nuclear plant, would require 50 such projects, or about 2,000 wind towers and $2 billion.

England, Germany, Netherlands: 10 Gigawatt Foundation Project  Proposal for 2,000 wind turbines of 5 megawatts each to make 10 gigawatts  Could power more than 8 million homes  Would cover 3,000 square kilometers  In the southern North Sea

“Here Comes The Sun” (by George Harrison) Conclusions  “All renewable energy is local” Adapt to locally available sources of renewable energy  Energy conservation is still the cheapest form of making energy available  In California, solar water heating is the next cheapest source of energy  Hydro should be maintained  Solar arrays are efficient and should be supported  Wind power is about the cost of nuclear. Have to find the right location. Siting a problem with views, noise, birds.  Nuclear power is omitted from renewable, but should be included as it also is non-polluting for greenhouse gases.  Solar photovoltaic needs more research and improvement, and is currently a wasteful investment.