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Alternatives to Nuclear Energy: Classifications and Technology Erica Raheja 04/13/08 Power Conversion: Turbines • Almost all electrical energy produced • Driven by a fluid Most common: steam Other: wind or water • Used to convert energy into electrical energy (attach to generator) Simplest: shaft with blades attached Early examples: windmills or waterwheels Alternative Energy Sources • • • • Fossil fuels: coal, petroleum, natural gas Solar power Wind power Water power Hydro-electric Tidal Wave • Geothermal power • Biofuel Fossil Fuels • • • • Coal, petroleum, natural gas Found in the earth’s crust Non-renewable resource Burned to create steam which turns turbine Fossil Fuels cont. Pros of Fossil Fuels • • • • Large amounts of energy produced Relatively cheap Can build a plant almost anywhere Transportation of fuel relatively easy Cons of Fossil Fuels • Pollution Burning fossil fuels produces carbon dioxide, a “greenhouse” gas • Obtaining the fuel can have negative effects on the environment • Acid rain • Release of radioactive material • Non-renewable resource Solar Power • Three major categories Photovoltaic cells Solar power heating Solar furnaces • Other research Solar Power cont. • Photovoltaic (PV) cells Convert solar energy directly into electrical Photons from the light knock the electrons into an excited state, generating electricity Cells connected together in panels for more electricity Solar Power cont. • Solar power heating Sun heats water in exposed glass panels Require less electrical power to heat Problem: water in panels can freeze Solar Power cont. • Solar furnaces or Concentrating Solar Power (CSP) system Concentrate sunlight into small beam by use of mirrors or lenses Can then use as heat source Solar Power cont. • Trough system Solar Power cont. • Power tower system Solar Power cont. • Dish engine system Solar Power cont. • More pictures Solar Power cont. • Research/Experimental Technology Solar updraft tower A large greenhouse funnels heated air into a central tower which can turn turbines Solar pond A pool of salt water collects and stores solar energy Solar Power Pros • • • • It is free Can be used in remote locations Good for low-power usage Renewable resource Solar Power Cons • Does not work at night • Extremely expensive to build solar power stations • Unreliable except in sunny climates Wind Power • Wind blows in and turns propeller blades, turning a generator • Pitch can be changed according to wind speed • Made to turn and face wind Wind Power cont. • Often build many wind towers together to create “farm” • Need places where wind is reliable and strong Wind Power Pros • Wind is free • No waste products • Land underneath potentially used for farming purposes • Way of providing energy to remote locations • Renewable resource Wind Power Cons • Wind unpredictable, unreliable source of power • Coastal land expensive • Can kill birds • Noise pollution Water Power • Three major categories Hydro-electric power Tidal Wave Water Power cont. • Hydro-electric power • Running water has kinetic energy (converted from potential energy height) • Generally dam built to trap water • Water flows through dam, turning turbines as it passes by Water Power cont. • Dam must be thicker at bottom to withstand pressure • Expensive to build but water is free and produces cheap energy • Evaporation from sun keeps lake filled with water Water Power cont. • Hoover dam Water Power cont. • Hydro-electric advantages Energy cheap after dam is built No waste or pollution produced Reliable source of power Water can be stored for peak usage Can increase to full power relatively fast Electricity can be produced constantly Renewable • Disadvantages Expensive to build dams Changes to the environment Suitable sites can be difficult to find Water Power cont. • Tidal power • Dam built across a river estuary • Ebb and flow of the tides either turns a turbine or pushes air through a pipe that turns a turbine Water Power cont. • Largest tidal power station in the world: Rance estuary in France • Only can generate power when the tide is going in or out Water Power cont. • Other option: offshore turbines or tidal stream systems • Similar to underwater wind farm • Need locations in fast currents Water Power cont. • “Swanturbines” design from University of Wales Swansea Water Power cont. • Advantages Tidal power is essentially free, renewable, and clean once the original installation is made Produces electricity reliably - tides are predictable Not expensive to maintain Offshore turbines relatively inexpensive and lowimpact on environment • Disadvantages A barrage across an estuary is expensive Few sites (about 20 around the world) Only provides power for 10 hours Water Power cont. • Wave power Water Power cont. • Advantages Wave power is free, clean, and renewable Inexpensive to build and maintain Can produce a lot of energy • Disadvantages Waves unpredictable - need suitable site Can be noisy Must be able to withstand all weather Geothermal Power • Heat from the earth used for power • Dry steam Steam from fractures used to drive turbine • Flash Hot water rises and boils as it comes to the surface. Steam used to drive turbine • Binary Hot water run through heat exchangers, boiling organic fluid used to drive turbine Geothermal Power cont. • If there is not already water below ground, can pump water down • Called Enhanced Geothermal System (EGS) Geothermal Power cont. • Important resource in volcanically active areas: Iceland, New Zealand • Efficiency depends on the temperature of the water • Can deplete a site Geothermal Power cont. • The Nesjavellir Geothermal Power Plant in Iceland Geothermal Power Pros • No pollution • Power plants take up little room, giving it a low impact on the environment • No fuel is needed • Once built, energy almost free • Work continuously • Renewable resource Geothermal Power Cons • • • • Few places viable to build power stations Depletion of a site can occur Hazardous gas can rise to the surface Can lower land stability Biofuel • Generally, biofuel is burned and used to heat steam • Made of or derived from dead biological matter • Exist in solid, liquid, and gaseous forms Biofuel cont. • Solid biofuel: wood, biogenic municipal solid waste, unused portions of field crops, animal wastes • Can be burned for heat to warm homes or be used in external combustion engines • Can convert wood and byproducts into liquid or gas via gasification Biofuel cont. • Liquid biofuel: bioalcohol (ethanol) or bio-oil (biodiesel or vegetable oil) • Generally used in diesel engines No modifications needed for biodiesel • Reduce emissions from fossil fuels • Made from corn, sugarbeets, sugar cane, etc. Biofuel Pros • Makes sense to use waste products when possible • Fuel tends to be cheap • Less demand on the earth’s resources • Renewable resource Biofuel Cons • Collecting in sufficient quantities can be difficult • Burning does still produce greenhouse gases • Some materials are not available all year round Biofuel cont. • Biogas: methane gas • Produced from current waste streams like paper and sugar production and sewage • Naturally ferment to create methane • Mechanical biological treatment: use anaerobic digesters to process biodegradable material • Renewable natural gas: upgraded to quality like natural gas World Primary Energy Production • • • • • • • (Data from 2005) 36.8% petroleum 26.6% coal 22.9% dry natural gas 6.3% hydro power 6.0% nuclear power 0.9% other (geothermal, solar, wind, and biofuel)
