Renewable and Alternative Energy Sources

World Wide Energy Production 15.2% alternative 84.8% fossil fuels

U.S. Energy Consumption The four primary consumers of energy in the U.S. in 2007 were Industrial 32% Transportation 28% Residential 22% Commercial 18% 93% of the energy generated and used in the U.S. are from nonrenewable resources

Alternative Energy Sources World-wide, with the exception of coal, which has known reserves that will last a couple of centuries, the known reserves of oil are expected to be exhausted in your lifetime... Clearly, alternative energy sources are needed for the future

Alternative Energy Sources We will look at: Solar energy Geothermal power Hydropower Tidal Power Ocean thermal energy conversion Wind energy Biomass

Solar Energy The Sun is free (nobody owns or controls it) In principle, the amount of solar energy that reaches the Earth’s surface could provide for all human energy needs forever

Solar Energy The distribution of solar energy over the continental U.S. in watts per square meter The desert regions of the southwest U.S. receive the most sunlight

Clean Solar Energy Solar energy is clean energy It produces no hazardous solid, liquid or gas wastes It does not create water or air pollution

Solar Energy The two areas in which solar energy can make the greatest contribution are in space heating and in the generation of electricity These are uses that account for two-thirds of U.S. energy consumption

Solar Heating The simplest approach to solar heating is passive-solar heating The building design should allow the maximum amount of sunlight to stream in through south and west windows during the cooler months This heats the house and materials inside

Solar Heating Trees can be positioned to shade the house in summer Wide eaves can shade windows in summer, but allow winter sunlight to enter Drapes and shutters can insulate window areas in winter

Solar Heating It has been estimated that 40 to 90% of most homes’ heating requirements could be supplied by passive-solar heating systems 100% solar homes have been built, but such homes usually cost many tens of thousands of dollars more to build Retrofitting older homes to be solar efficient can be too costly Over insulation can aggravate indoor pollution

Solar Electricity Direct production of electricity using sunlight is accomplished using photovoltaic cells, also called solar cells They have no moving parts and are “clean” energy They are used to power the space station and to provide electricity in remote areas on Earth

Solar Electricity A major limitation is cost, which greatly exceeds the cost of producing electricity using fossil fuels or nuclear power The best solar cells are only 20% efficient and only provide 50 watts of electricity per square meter of cell size

Solar Electricity A 100 watt light bulb would require 2 square meters of solar cells And a 100-megawatt power plant would require 2 square kilometers (0.78 square miles) of solar cells This represents a major use of land and resource, which would use far more steel and concrete than a fossil fuel power plant

Storing Solar Electricity In a solar energy home, extra electricity is stored in batteries for later use This work well for one house Unfortunately, no wholly practical technology has been developed to store large amounts of electricity, despite advances in batteries

Storing Solar Energy Some possible schemes for storing the energy of solar generated electricity include breaking up water into oxygen and hydrogen to burn later as fuels Also pumping water to an elevated reservoir for later use as hydroelectric power generation

Solar Energy Currently, solar energy provide less that 0.5% of the U.S. power needs, but even with existing technology, it could provide up to 15%

Solar Electricity In summation, to make solar energy truly useful for large-scale power generation: We need more efficient solar cells We need a means of better storing electricity

TRADE-OFFS Passive or Active Solar Heating Advantages Disadvantages Energy is free Need access to sun 60% of time Net energy is moderate (active) to high (passive) Sun can be blocked by trees and other structures Quick installation Environmental costs not included in market price No CO2 emissions Very low air and water pollution Figure 16.11 Advantages and disadvantages of heating a house with passive or active solar energy (Concept 16-3). Question: Which single advantage and which single disadvantage do you think are the most important? Why? Need heat storage system Very low land disturbance (built into roof or windows) High cost (active) Active system needs maintenance and repair Moderate cost (passive) Active collectors unattractive Fig. 16-11, p. 412

Geothermal Power

Geothermal Power Magma rising from the mantles brings unusually hot material near the surface Heat from the magma, in turn, heats any groundwater This is the basis for generating geothermal energy

Geothermal Power The steam and/or hot water is used to create electricity or for heating

Geothermal Power Plants Worldwide, there are now about 40 geothermal power plants, especially in Japan, Mexico and the Philippines Note that most geothermal power plants are built along plate tectonic boundaries

Geothermal Power Plants How the geothermal energy is used depends on the temperature of the water Three types of power plants are used to generate power from geothermal energy: Dry steam Flash Binary

Types of Geothermal Power Dry steam plants take steam out of the ground and uses the steam to turn a turbine that spins a generator This was first done in Italy in 1904 Iceland, a volcanic island, has many geothermal areas that produce steam and are tapped to generate electricity

Types of Geothermal Power Flash plants take super heated water, usually at temperatures over 200°C, out of the ground, allowing it to boil as it rises to the surface, then separates the steam from the water and uses the steam to turn a turbine generator A flash power plant in Japan

Types of Geothermal Power In binary plants, the hot water flows through heat exchangers, boiling an organic fluid that spins the turbine For all three types of power plants, the condensed steam and remaining geothermal fluid are injected back into the hot rock to pick up more heat This is why geothermal energy is viewed as sustainable It is also very “clean” Only produces steam

The Geysers, California The largest U.S. geothermal power plant is The Geysers in California (it uses dry steam) By 1989, a total of 10 billion watts of electricity was being produced by The Geysers and six other plants in the U.S.

Geothermal Power Plants By the end of 2005 worldwide use of geothermal energy for electricity had reached 9.3 billion watts, with an additional 28 billion watts used directly for heating In 1999, it was estimated that the U.S. could produce 100 billion watts of geothermal energy by 2050

Geothermal Heat Even if the geothermal water is not as hot as steam, the warm water can be used to heat buildings, home and even greenhouses This is routinely done in Russia and Iceland In fact, using geothermal energy to heat is about 2-3 times as common as using it to create electricity

Limitations Each geothermal field can only be used for a period of time, a few decades, before heat extraction is seriously reduced Simply put, you can take hot water out of the ground faster than it can be renewed (even if you pump the water back into the ground) For example, steam pressure at The Geysers has declined rapidly over recent years It peaked at over 2 billion watts by 1991, but now in 2011 produces about 0.7 billion watts

TRADE-OFFS Geothermal Energy Advantages Disadvantages Very high efficiency Scarcity of suitable sites Can be depleted if used too rapidly Moderate net energy at accessible sites Environmental costs not included in market price Lower CO2 emissions than fossil fuels CO2 emissions Low cost at favorable sites Figure 16.29 Advantages and disadvantages of using geothermal energy for space heating and for producing electricity or high-temperature heat for industrial processes (Concept 16-7). Question: Which single advantage and which single disadvantage do you think are the most important? Why? Moderate to high local air pollution Low land use and disturbance Noise and odor (H2S) High cost except at the most concentrated and accessible sources Moderate environmental impact Fig. 16-29, p. 428

Hydropower One-third (33%) of all power plants in the U.S. are hydroelectric, but they only generate 6% of U.S. electricity needs

Hydropower A cross-section of a typical hydroelectric dam Water flows down the penstock, turns the turbine blades which power the generators

Hydropower Water use for generating hydroelectric power is totally dependent on the available water (duh!!) The Glen Canyon Dam in Utah is the classic example of building too big of dam for not enough water

Hydropower Hydropower is a very clean, pollution-free, renewable energy source The water is not consumed, but rather simply passes thru the generating equipment, and since several dams may occur along the same river, the water can be reused and reused

Hydropower If every stream and river in America was dammed to generate power, you still only provide 20% of current U.S. power needs There are about 1000 dams in the U.S. and there is very little prospect of building any new ones In fact, some older dams have been removed, such as the 162 years old Edwards Dam in Maine

Three Gorges Dam The Three Gorges Dam is now the largest hydroelectric dam in the world

Three Gorges Dam As a size comparison, it is 5 times larger than the Hoover Dam on the Colorado River

Three Gorges Dam The dam is 185 meters (600 feet) high and 2.3 kilometers (1.4 miles) wide It has 26 hydroelectric power generators with a collective generating capacity of about 18,000 megawatts (the average nuclear power plant generates about 1000 megawatts)

Three Gorges Dam The Chinese began filling the reservoir in 2003 When filled to capacity, the reservoir will hold 22 cubic kilometers of water

Three Gorges Dam As with any engineering project of great magnitude, there are serious problems The reservoir will eventually stretch over 600 kilometers (375 miles) in length It will submerge 125,000 acres of prime farmland

Three Gorges Dam 1,900,000 people were forced to relocate, many against their will Entire cities have been abandoned Over 1200 historic areas are being flooded

Three Gorges Dam Three spectacular river gorges called Qutang, Wuxia and Xiling, all worthy of being national parks, have been flooded

Three Gorges Dam Officials report that the cost is within its US$25 billion budget and insisted early on that the project would pay for itself through electricity generation However, the project is thought to have cost more than any other single construction project in modern China, with unofficial estimates of US$100 billion or more

TRADE-OFFS Large-Scale Hydropower Disadvantages Advantages High construction costs Moderate to high net energy High environmental impact from flooding land to form a reservoir High efficiency (80%) Large untapped potential Environmental costs not included in market price Low-cost electricity Long life span High CO2 emissions from rapid biomass decay in shallow tropical reservoirs No CO2 emissions during operation in temperate areas Figure 16.21 Advantages and disadvantages of using large dams and reservoirs to produce electricity (Concept 16-4). Question: Which single advantage and which single disadvantage do you think are the most important? Why? Danger of collapse Can provide flood control below dam Uproots people Decreases fish harvest below dam Provides irrigation water Decreases flow of natural fertilizer (silt) to land below dam Reservoir useful for fishing and recreation Fig. 16-21, p. 418

Tidal Power All large bodies of water, including the oceans and large lakes, have tides Tidal power captures the energy contained in moving water mass due to tides

Tidal Power Two types of tidal energy can be extracted: Kinetic energy of currents between ebbing and surging tides Potential energy from the difference in height (or head) between high and low tides

Tidal Power You can use the flowing water between low and high tides to generate electricity, similar to hydropower

Tidal Power Turbines can be place on the ocean floor, for example at the entrance of a bay, where the flowing water can turn the fan to generate electricity

Tidal Power Another option is to use under water turbines, which is like an underwater wind farm This is currently being tested offshore of Scotland’s Orkney Islands The ebbing and surging tidal flows turn 100 foot propellers, which each produce 1 megawatts of electricity

OTEC Ocean energy thermal conversion (OTEC) is a new, clean technology that is still in the developmental stage It exploits the temperature difference between warm surface water and the cold water at depth to run a “heat engine” A heat engine is a device placed between a high temperature reservoir and a low temperature reservoir that produces energy

OTEC Either the warm water is used directly to run a turbine, or the heat is used to vaporize a working fluid (ammonia) which runs the turbine The cold water is used to chill down the water or vapor Drinkable, distilled fresh water is a by-product

OTEC The temperature difference must be at least 40oF (22oC) year round, which is only found near the equator So this emerging technology is best for tropic islands

OTEC A test plant is currently being constructed at Keahole Pointe on the Kona coast of Hawaii and should become operational in 2013

Wind Energy Wind energy has been utilized for thousands of years

Wind Energy The wind is free, commonly available and can provide clean, pollution-free energy Today’s wind-turbines are very high tech

Wind Energy In most places, the cost of commercial wind power on a large scale is not now economically competitive with conventionally generated electricity One important factor is that with a doubling of wind speed, power output increases by a factor of 8

Wind Energy The numbers indicate the percentage of 1990 regional electricity demand that full utilization of wind energy could meet Clearly, the great plains have significant wind energy potential

Wind Energy U.S. wind power capacity from 1981 to 2002

Wind Energy U.S. wind power capacity from 1996 to 2008

Wind Energy The U.S. remains the world leader in wind energy, but Europe has embarked on an very ambitious wind-power development program It is predicted that by 2030, wind energy will supply at least twice the electricity it does now

Wind Energy Limitations It would take about 1000 one-million watt windmills to equal the energy output of one sizable fossil fuel power plant The windmills can be noisy And they are hard on migrating birds

TRADE-OFFS Wind Power Advantages Disadvantages Moderate to high net energy yield Steady winds needed Backup systems needed when winds are low High efficiency Moderate capital cost Plastic components produced from oil Low electricity cost (and falling) Environmental costs not included in market price Very low environmental impact High land use for wind farm No CO2 emissions Figure 16.23 Advantages and disadvantages of using wind to produce electricity (Concepts 16-5). With sufficient and consistent incentives, wind power could supply more than 10% of the world’s electricity and 10–25% of the electricity used in the United States by 2020. Question: Which single advantage and which single disadvantage do you think are the most important? Why? Quick construction Visual pollution Easily expanded Noise when located near populated areas Can be located at sea Land below turbines can be used to grow crops or graze livestock Can kill birds and interfere with flights of migratory birds Fig. 16-23, p. 421

Biomass Energy Biomass energy is derived from organic matter Stoves that burn wood are the classic example In fact, there had been a 20-25% increase in the use of wood stoves over the past several decades

Biomass Fuels or Biofuels Biofuels differ from other renewable energy sources, such as wind, hydroelectric, geothermal and solar, as they are primarily used in the transportation sector and are derived from recently living matter, both plant and animal

Ethanol Fuel Ethanol fuel is a biofuel alternative to gasoline, which is gaining popularity world-wide Car engines can be designed to run on 10%, 50% even 100% pure ethanol It is cleaner burning than gasoline Worldwide, the use of ethanol is rapidly increasing

“E” Numbers Ethanol fuel mixtures have "E" numbers which describe the percentage of ethanol in the mixture by volume, for example, E85 is 85% ethanol and 15% gasoline Low ethanol blends, from E5 to E25, are also known as gasohol, though internationally the most common use of the term gasohol refers to the E10 blend

Gasohol E10 gasohol is becoming more commonly found at gas stations in the U.S. (Tennessee is way behind) As the “10” indicates it is made from a mixture of gasoline (90%) and ethanol (10%) Gasohol has higher octane, or antiknock, properties than gasoline and burns more slowly, more cooler, and more completely, resulting in reduced emissions of some pollutants

Ethanol Fuel Automotive ethanol capabilities vary widely country to country, but most spark-ignited gasoline style engines will operate well with mixtures of up to 10% ethanol Brazil is the world leader in ethanol fuels In Brazil, ethanol-powered and flexible-fuel vehicles are manufactured to be capable of operation by burning hydrated ethanol, an azeotrope of 93% ethanol and 7% water

Ethanol Fuel Ethanol fuel is produced from sugar cane in Brazil, which is a more efficient source of fermentable carbohydrates than corn as well as much easier to grow and process in the tropical climate

UT & Switchgrass The UT Biofuels Initiative has started testing the use of switchgrass, which is believed to offer a greater ethanol yield than corn in a temperate climate, such as in Tennessee

UT & Switchgrass The project represents the culmination of years of corporate research and development and a highly touted $40.7 million investment from the state of Tennessee to build a plant for demonstrating technology developed by DuPont Danisco Cellulosic Ethanol

TRADE-OFFS Biodiesel Advantages Disadvantages Reduced CO emissions Increased NOx emissions and more smog Reduced CO2 emissions (78%) Higher cost than regular diesel High net energy yield for oil palm crops Environmental costs not included in market price Low net energy yield for soybean crops Moderate net energy yield for rapeseed crops May compete with growing food on cropland and raise food prices Figure 16.25 General advantages and disadvantages of using biodiesel as a vehicle fuel, compared to gasoline. Question: Which single advantage and which single disadvantage do you think are the most important? Why? Reduced hydrocarbon emissions Loss and degradation of biodiversity from crop plantations Better gas mileage (40%) Can make engines hard to start in cold weather Potentially renewable Fig. 16-25, p. 424

TRADE-OFFS Ethanol Fuel Advantages Disadvantages High octane Lower driving range Low net energy yield (corn) Some reduction in CO2 emissions (sugarcane bagasse) Higher CO2 emissions (corn) Much higher cost High net energy yield (bagasse and switchgrass) Environmental costs not included in market price Figure 16.27 General advantages and disadvantages of using ethanol as a vehicle fuel, compared to gasoline. (Concept 16-6B). Question: Which single advantage and which single disadvantage do you think are the most important? Why? May compete with growing food and raise food prices Reduced CO emissions Can be sold as E85 or pure ethanol Higher NOx emissions and more smog Corrosive Potentially renewable Can make engines hard to start in cold weather Fig. 16-27, p. 426

Alternative Energy Sources Most of the world still relies very heavily on fossil fuels, but slowly but surely, attention is being diverted to alternative energy Energy use in the future will not be dominated by a single source

Alternative Energy Sources The most important aspects of most alternative energy sources is that they promise clean, pollution-free energy