Alternate Energy Sources

Transcription

1 Alternate Energy Sources Sustainable or renewable energy Energy that is renewable and is not being depleted: solar, wind, water (including geothermal and tidal) States with Renewable Energy Goals 1

2 Terminology Watts energy measurement 1 million watts = 1000 kilowatts (kw) = 1 million megawatts (mw) Coal or nuclear power plant supplies an average of 1000 mw power/year Wind Energy Use wind to turn turbines to produce energy Old technology Clean no water or air pollution Unreliable wind stops, so does electricity Wind energy: where? Need steadily windy places Great Plains thought to be able to supply 75% of US energy Far from population concentrations California mountain ridges Most US wind farms on land Cape Cod Wind Farm project first US offshore project (3.6 mw wind turbines) Denmark, Germany 2

3 Requirements Need wind 300+ feet tall windmills are most efficient Each windmill could supply 1-5 megawatts Need power lines traditional wind mills generated power for just a farm Burying power lines 3

4 Megawatts of energy produced by wind Problems Intrusive noise, shadow Aesthetics Difference between conventional power plant pollution and wind power pollution More opposition to wind power than solar power Heavily subsidized green energy Tax credit on clean energy masks true costs cheapest source of new power generation Problems Does kill birds and bats mountain ridges tend to be flyover paths Cuisinarts for birds Roads and power line corridors may have to be built Ideal on farmland 4

5 Sunlight used as energy Most common use is to heat house and water Clean no air or water pollution from energy generation Solar energy 5

6 3 ways to use sunlight 1. Passive heating: sunlight hits surfaces, heat is absorbed, released at night Southern-facing window or walls Low cost Windows and wall materials store heat Heat collected and used at same site Winter locations 3 ways to use sunlight 2. Active heating: sunlight converted into heat and transferred to place of use Still near source of collection Typically water and space (house) heating Water heating very economical Easiest to install on new buildings High initial cost Heat, not electricity, generated 3 ways to use sunlight 3. Solar-generated electricity: uses photovoltaic cells (PV) to convert sunlight into electricity Can be used as shingles on houses or put on top of commercial buildings Low maintenance Good in isolated areas: islands, Alaska, Australia, also in place of power lines (traffic signals) 6

7 Large scale solar-generated electricity Use energy to convert water into steam Only 15 solar power plants currently in US (CA and AZ) Drawbacks to PV Cost Location Size Silicon production key to success is to boost energy efficiency of cells Problems Need sunlight Low efficiency of PV requires more cells to produce reasonable amount of energy Initial cost is high Silicon has to be produced 7

8 Hydroelectric Power Use water to push turbines to generate electricity Moving water has energy Widespread resource if you have enough water, can create electricity Clean power no water or air pollution Usage Approx. 50% of US capacity reached vs. 5% in Africa Central and South America: 50% of power from hydroelectricity 99% of Norway s power from electricity Previous usage in US Tennessee Valley Authority (TVA) built hydroelectric dams to electrify and control floods in the region. In 1950s, TVA was largest supplier of electricity in country 8

9 Dams Most common way to harness energy from water Creates reservoir Ensures steady electricity generation even during periods of low flow Creates falling water Natural electricity: as water moves down a gradient (a slope), it has energy Structure types Hyrdoelectric dams need water to pass through turbines Top electricity producing dams are in China (Three Gorges), Venezuela, and on the Paraguay Brazilian border In US: Grand Coulee, WA largest concrete structure in country 9

10 Dam types "run-of-the-river": water is used continuously with limited reservoir storage (e.g., Bonneville on lower Columbia) Dam types "storage": water is released as needed and available (e.g., Glen Canyon in Arizona) Glen Canyon dam and Lake Powell Advantages Clean energy Operation and maintenance costs are low once dam is built and if sediment is low Generating plants have a long lifetime (50 year licensed just granted at Niagara Falls) Unscheduled breakdowns are relatively infrequent and short in duration since the equipment is relatively simple 10

11 Advantages Hydroelectric turbine-generators can be started and put "on-line" very rapidly Recreational benefits of a reservoir or continued benefit of a free-flowing river Disadvantages 1. Very land-use oriented and may flood large regions Displace people Submerge historic places, and scenic areas YESTERDAY 2. Fish migration is restricted 11

12 3. Reservoirs alters silt-flow patterns Sediment is trapped behind dams Downstream is depleted of sediment: Depletes bank edges Interferes with natural refertilization of land 4. Local habitat altered Water temperature change Habitat loss from reservoir construction 12

13 All lakes and reservoirs, without dredging, will eventually fill in with sediment! Vaiont Dam 13