Nonrenewable energy resources
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Nonrenewable Energy Resources Solar Ponds Ocean Thermal Energy Conversion Solar Ponds Working fluid (water, or propane, ammonia, freon (low boiling point) heat exchanger from surface water/ works water into steam exhaust heat back into liquid volume by factor 1000

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Nonrenewable Energy Resources

Solar Ponds

Ocean Thermal Energy Conversion


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Solar Ponds

  • Working fluid (water, or propane, ammonia, freon (low boiling point)

  • heat exchanger from surface water/ works water into steam

  • exhaust heat back into liquid

    • volume by factor 1000

    • compared to if pumping gas into system

  • 33% efficient

  • 1000MW needs 3000MW boiler

    • 2000MW are waste heat


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Solar Ponds

  • Capture solar radiation/ store it almost 100 C

  • water in ponds are source of storage for heat from sun - allows it to maintain original heat

  • specific heat of water


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Saline Solar Ponds

  • Salt water

  • better capacity for heat

  • near inland saline seas or lakes

  • ample sunlight

  • produce electricity from heat stored in layers of increasing concentrations of salt


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Saline Solar Ponds

  • Heat builds up during day in saltier/ denser bottom layer

  • hot brine is pumped out

  • produces steam/spins turbines to generate electricity

  • returned to pond to be reused


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Saline Solar Ponds

  • Experiment: California and Australia

  • Experiment: Dead Sea

    • closed 1989: $


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Freshwater Solar Ponds

  • Heat water and space

  • shallow hole dug; concrete

  • many large, black, plastic bags filled with cm of water placed in whole

  • fiberglass insulation panels


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Freshwater Solar ponds

  • Fiberglass allows heat in, locked in on earth

  • water reaches highest temp, computer turns on and has it pumped to tanks for distribution


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Solar Ponds

  • Require no energy storage nor backup system

  • air pollution

  • moderate net energy yield

  • freshwater solar ponds: any sunny area

    • moderate construction/operation $

    • development/research, 3-4% of electricity w/10 years


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Ocean Thermal Energy Conversion

  • Generating electricity from the difference between ocean temperatures

  • cold = 2000’ below surface

  • difference of 40 F for net power to be generated


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The Basic Process

  • Working fluid (water, ammonia, propane, freon - low boiling point) runs through a heat exchanger

  • gets heat from surface water turns fluid into steam

  • exhaust heat back into liquid decreasing volume by factor of 1000


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The Basic Process Continued

  • Work done by pump is down by 1000 compared to having to pump steam directly back into system

  • overall efficiency is 33%

  • a 1000 MW plant requires 3000MW boiler and 2000MW are given off as waste heat


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The Basic Processes: 3 Types

  • Closed-cycle system

  • Open-cycle system

  • Hybrid-cycle

    • still in theoretical designs

    • basically use both to optimize electricity


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Closed-Cycle System

  • Heat moved from warm surface sea water heats a working fluid (ammonia (78), propane, freon) to vapor

  • expanding vapor drives a turbine attached to generator electricity

  • cold sea H2O passes through condenser w/vaporized working fluid turns the vapor back into liquid to be reused


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Open-Cycle System

  • Warm surface water

  • vaporizes in a near vacuum at surface water temps

  • expanding vapor drives low-pressure turbine attached to generator: elec.

  • Vapor lost salt/almost pure freshwater

  • condensed by exposure to cold water from deep


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Open-Cycle System

  • Avoid direct contact

    • Condensed water can be used for drinking, irrigation, aquaculture

  • Deliberate direct contact

    • produces more elec., but the vapor is mixed with cold water and the discharge water is salty- mixture returned to ocean

  • process constant by continuous supply of warm surface water


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Open-Cycle System Advantages

  • Efficiently removes gases

  • decreases cost

  • eliminates some potentially damaging elements discharge into the atmosphere

  • 20 times energy savings over all other devices


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Problems of OTEC

  • Cost:

    • plant very $ because technology not advanced enough

    • 1KW/hour: 200 - 400 1500

  • Technological:

    • no existing technology

    • how to deliver power?

    • power line in ocean: catch 22

      • dangerous, but necessary


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Problems

  • Technological

    • H2, O2- large quantities make it unreasonable

    • 10% of energy

      • for H2, 30 large shiploads/day or .3 million tons to be piped

  • Legal

    • built outside US and continental limits

      • what about new laws and protection


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Problems

  • Location

    • between 23 North latitude/23 South latitude

    • depths of 200’ but too much space

    • Puerto Rico, Hawaii, Florida, California

      • nat. beauty; plants undesireable


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Biological Problems

  • Metallic corrosion:

    • metallic elements into water

      • copper = ecological damage, aluminum, titanium - plastic, still being developed

  • Ocean water dump:

    • water brought from bottom, in temp and press (-) affects on creatures brought up

    • may have good effects


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Biological Problems

  • Toxic closed-system fluid leaks

  • if ammonia leaks in small bits, not harmful, but devastating in large spill

  • Biocides

    • biofouling

    • chlorine used around plant

      • same as above


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Benefits

  • 2010 10% energy to world; will last billions of years

  • not dependent on sunlight

  • could handle all demands

  • weather irrelevant

  • produce 750MW

    • at least 3/4 as powerful as regular coal plant


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