Chapter 8 Renewable and Alternative Energy Sources

World Wide Energy Production

15.2% alternative84.8% fossil fuels

U.S. Energy Consumption

The four primary consumers of energy in the U.S. in 2007 wereIndustrial32%Transportation28%Residential22%Commercial18%93% of the energy generated and used in the U.S. are from nonrenewable resources

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 futureAlternative Energy Sources

We will look at:Solar energyGeothermal powerHydropowerTidal PowerOcean thermal energy conversionWind energyBiomassAlternative Energy Sources

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

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

Clean Solar EnergySolar energy is clean energyIt produces no hazardous solid, liquid or gas wastesIt does not create water or air pollution

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

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

Solar HeatingTrees can be positioned to shade the house in summerWide eaves can shade windows in summer, but allow winter sunlight to enterDrapes and shutters can insulate window areas in winter

Solar HeatingIt has been estimated that 40 to 90% of most homes heating requirements could be supplied by passive-solar heating systems100% solar homes have been built, but such homes usually cost many tens of thousands of dollars more to buildRetrofitting older homes to be solar efficient can be too costlyOver insulation can aggravate indoor pollution

Solar ElectricityDirect production of electricity using sunlight is accomplished using photovoltaic cells, also called solar cellsThey have no moving parts and are clean energyThey are used to power the space station and to provide electricity in remote areas on Earth

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

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

Storing Solar ElectricityIn a solar energy home, extra electricity is stored in batteries for later useThis work well for one houseUnfortunately, no wholly practical technology has been developed to store large amounts of electricity, despite advances in batteries

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

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

Geothermal Power

Geothermal PowerMagma rising from the mantles brings unusually hot material near the surfaceHeat from the magma, in turn, heats any groundwaterThis is the basis for generating geothermal energy

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

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

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

Types of Geothermal PowerFlash plants take super heated water, usually at temperatures over 200C, 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 generatorA flash power plant in Japan

Types of Geothermal PowerIn binary plants, the hot water flows through heat exchangers, boiling an organic fluid that spins the turbineFor all three types of power plants, the condensed steam and remaining geothermal fluid are injected back into the hot rock to pick up more heatThis is why geothermal energy is viewed as sustainable It is also very cleanOnly produces steam

The Geysers, CaliforniaThe 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 PlantsBy the end of 2005 worldwide use of geothermal energy for electricity had reached 9.3billion watts, with an additional 28billion 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 HeatEven if the geothermal water is not as hot as steam, the warm water can be used to heat buildings, home and even greenhousesThis is routinely done in Russia and IcelandIn fact, using geothermal energy to heat is about 2-3 times as common as using it to create electricity

LimitationsEach geothermal field can only be used for a period of time, a few decades, before heat extraction is seriously reducedSimply 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 yearsIt peaked at over 2 billion watts by 1991, but now in 2011 produces about 0.7 billion watts

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

HydropowerA cross-section of a typical hydroelectric damWater flows down the penstock, turns the turbine blades which power the generators

HydropowerWater 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

HydropowerHydropower is a very clean, pollution-free, renewable energy sourceThe 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

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

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

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

Three Gorges DamThe dam is 185 meters (600 feet) high and 2.3 kilometers (1.4 miles) wideIt 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 DamThe Chinese began filling the reservoir in 2003When filled to capacity, the reservoir will hold 22 cubic kilometers of water

Three Gorges DamAs with any engineering project of great magnitude, there are serious problemsThe reservoir will eventually stretch over 600 kilometers (375 miles) in lengthIt will submerge 125,000 acres of prime farmland

Three Gorges Dam1,900,000 people were forced to relocate, many against their willEntire cities have been abandonedOver 1200 historic areas are being flooded

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

Three Gorges DamOfficials report that the cost is within its US$25 billion budget and insisted early on that the project would pay for itself through electricity generationHowever, 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

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

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

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

Tidal PowerTurbines 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 PowerAnother option is to use under water turbines, which is like an underwater wind farmThis is currently being tested offshore of Scotlands Orkney IslandsThe ebbing and surging tidal flows turn 100 foot propellers, which each produce 1 megawatts of electricity

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

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 turbineOTECThe cold water is used to chill down the water or vaporDrinkable, distilled fresh water is a by-product

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

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

Wind energy has been utilized for thousands of yearsWind Energy

The wind is free, commonly available and can provide clean, pollution-free energyTodays wind-turbines are very high techWind Energy

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

The numbers indicate the percentage of 1990 regional electricity demand that full utilization of wind energy could meetClearly, the great plains have significant wind energy potentialWind Energy

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

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

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

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

Biomass energy is derived from organic matterStoves that burn wood are the classic exampleIn fact, there had been a 20-25% increase in the use of wood stoves over the past several decadesBiomass Energy

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 animalBiomass Fuels or Biofuels

Ethanol fuel is a biofuel alternative to gasoline, which is gaining popularity world-wideCar engines can be designed to run on 10%, 50% even 100% pure ethanolEthanol FuelIt is cleaner burning than gasolineWorldwide, the use of ethanol is rapidly increasing

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 E NumbersLow 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

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%) GasoholGasohol 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 FuelAutomotive 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 fuelsIn 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 FuelEthanol 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 & SwitchgrassThe 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 & SwitchgrassThe 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

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

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

Chapter 9 Water Resources