Nonrenewable Energy Resources

1. Nonrenewable Energy Resources Solar Ponds Ocean Thermal Energy Conversion

3. 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

5. 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

7. 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

8. 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

9. Saline Solar Ponds • Experiment: California and Australia • Experiment: Dead Sea • closed 1989: $

10. 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

11. 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

12. 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

14. 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

15. 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

16. 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

17. The Basic Processes: 3 Types • Closed-cycle system • Open-cycle system • Hybrid-cycle • still in theoretical designs • basically use both to optimize electricity

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

26. 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

27. 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

28. 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