Combined Thermal Plumes from Multiple Power Stations

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Modelling Combined Thermal Plumes from Multiple Power Stations in the Arabian Gulf with MIKE 3 - George Mitchell (TechnoEconomica) & James Tomlinson (Atkins)

MIKE by DHI 15th UK User Group Meeting - Tuesday 19 March 2013

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  • The use of thermal cooling systems in industries ranges widely. thanks for sharing about your project.
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Combined Thermal Plumes from Multiple Power Stations

  1. 1. 19th March 2013George Mitchell (TechnoEconomica) James Tomlinson (Atkins)
  2. 2. TOPICS  Gulf of Arabia Models  Thermal and hypersaline discharges  Model behaviour in very shallow water  Direct and indirect cooling systems….  Do we need to model these more faithfully?17-Apr-13 2
  3. 3. Outer Gulf Model 3
  4. 4. Gulf Model – Mesh 4
  5. 5. Significant Processes in the Gulf Solar Radiation Nett Long Wave 900 Wm-2 Radiation Peak Shading from Very large buildings variation in effectively nil Relative Humidity Surface heat Wind exchange Outfall Circulation Dispersion Recirculation Stratification Intake Ground heat exchange 5
  6. 6. Tropical Marine Environment See grass beds Reefs Dwellers Algae Coral Reefs(Sheppard et al., 1992; Wilkinson, 2002; GHD, 2007; GHD 2009)
  7. 7. 17-Apr-13 Ecosystems Reaction to Temperature Ecosystems respond to all aspects of the temperature regime, including the maxima and minima, seasonal and daily fluctuations, rates of change and the duration of extreme thermal events. 7
  8. 8. Coral Thermal Limits
  9. 9. Regulations….and reality  REGULATION  The temperature measured downstream of a point of thermal discharge (at the edge of the mixing zone) must not exceed the unaffected temperature by more than 3°C.  REALITY  Mixing zone is very large  Area of impact is potentially 100’s of km2  Recirculation  Interaction  Stratification  Sluggish flows  Ambient sea temperatures in summer reaching 33°C17-Apr-13 9
  10. 10. Sources of Heat  Large Direct Cooled Power Stations 2GW per installation  Industrial Process Cooling Circuits  Desalination Plants (RO)  Cogeneration Plants (MSFD & MED)17-Apr-13 10
  11. 11. Plume Behaviours  MSFD plumes form near sea bed  RO plumes form near sea bed  Direct Cooled PS plumes form near surface  MSFD plumes are depressed by one of the Industrial Circuit plumes  Upper limits of recirculation 1°C max not achieved  Sluggish flows and nature of circulation inhibits strong mixing  Density deficit is a function of season – behaviour is seasonal  Very hot ambient sea temperatures in summer  Upper temperatures may exceed those lethal to corals  NEED TO BE AS ACCURATE AS POSSIBLE17-Apr-13 11
  12. 12. Plume Interaction17-Apr-13 12
  13. 13. Interaction of Plumes Surface Stratification Layered Benthic Impact Stratification
  14. 14. Requirements  Accurate Calibration and Verification of Model  Accurate Representation of Effluents  Flow rate  Salinity  Temperature17-Apr-13 14
  15. 15. Cold Patches in Shallow Water17-Apr-13 15
  16. 16. Ground Heat Exchange Shallow Sea Heat exchange simple 1D Temperature specified at equilibrium depth Ground beneath the sea17-Apr-13 16
  17. 17. 17Ground Heat Exchange - Shallow Water 05-Jul-2007 00:00 04-Jul-2007 18:00 04-Jul-2007 12:00 Ground Heat Exchange - Influence of Equilibrium Depth 04-Jul-2007 06:00 04-Jul-2007 00:00 03-Jul-2007 18:00 5m 1m 03-Jul-2007 12:00 03-Jul-2007 06:00 10m 03-Jul-2007 00:00 2m 02-Jul-2007 18:00 02-Jul-2007 12:00 02-Jul-2007 06:00 02-Jul-2007 00:00 01-Jul-2007 18:00 01-Jul-2007 12:00 01-Jul-2007 06:00 01-Jul-2007 00:00 0.00 -0.20 -0.70 -0.10 -0.30 -0.40 -0.50 -0.60 -0.80 -0.90 -1.00 -1.10 -1.20 -1.30 -1.40 -1.50 °C 17-Apr-13
  18. 18. Evaporative Cooling  Smaller effluent flow  Provides a buffer for recirculation  Effluent temperature uplift function of humidity  Water loss due to evaporation and windage  Discharge salinity uplift  Higher opex and capex 18
  19. 19. Evaporative Cooling - Physics 60 Hot Water 55 50 Falling Droplets Enthalpy KJkg-1 45 40 Approach Rising Air 35 30 25 20 0 10 20 30 40 50 Temperature °C 19
  20. 20. Test Model17-Apr-13 20
  21. 21. Effect of Relative Humidity on Temperature Uplift 25 20 15 Uplift °C 10 e 5 0 -5 0 20 40 60 80 100 Relative Humidity %17-Apr-13 21
  22. 22. Environmental Impact Temperature at Inlet Basin Scenario 21 45 5.0 40 4.0 35 3.0 30 °C 25 2.0 °C 20 1.0 15 Simulated Annual Absolute Temperature – 0.0 10 Calibrated with -1.0 5 measured data 0 -2.0 Nov-2007 Oct-2007 May-2007 Jul-2007 Aug-2007 Sep-2007 Jun-2007 Simulated Ambient Temperature Temperature at Inlet Basin Temperature Uplift
  23. 23. Temperature Distribution Cumulative Distribution 100 99 90 98 80 97 70 96 60 %ile 95 50 94 40 Baseline 93 30 Direct Cooling 92 20 Cooling Tower (Average) 91 10 Cooling Tower Computed 90 0 28 24 29 25 29 26 30 27 30 28 31 29 31 30 32 31 32 Water Temperature °C17-Apr-13 Getting Into Hot Water 23
  24. 24. Some Questions & Recommendations  Ground heating affects shallow water temperatures – how realistically is it modelled?  Does it matter?  Delay in power stations – is it significant?  Cooling towers - should these be modelled properly under certain circumstances?  More investigation needed17-Apr-13 Getting Into Hot Water 24

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