North Anna Unit 3 Hybrid Cooling

Transcription

1 North Anna Unit 3 Hybrid Cooling John D. Waddill, P.E. Dominion Resources, Inc. EPRI Workshop on Advanced Cooling Technologies Acknowledgement: Douglas A. Kemp, P.E. Bechtel Power Corporation PP640.1

2 Why the North Anna Site? Space Environmentally acceptable No superior alternative Originally planned for 4 units PP640.2

3 PP640.3

4 Available Water Supply Net Inflow Pre-Operational Evaporation Minimum Dam Release Available Water Supply Unit 3 Water Needs Once Through System 369 cfs 93 cfs 40 cfs 236 cfs 28 cfs Storage Volume: 25,400 acre-ft (250 ft to 248 ft, msl) PP640.4

5 Overview of North Anna Project ESP application submitted to NRC in units at 1520 MWe each Unit 3 cooling system changed in 2005 from open to closed cycle due to agency and public concerns Thermal Discharge Lake level and downstream flow impacts COL application submitted in Nov 2007 ESP received in Nov 2007 PP640.5

6 Cooling Technologies Considered Closed Cycle Conventional Cooling Tower Thermal Issue: Solved Water Use Issue: Potentially Worse Combination Wet-Dry Cooling (Hybrid) Thermal Issue: Solved Water Use Issue: Significantly Reduced PP640.6

7 Available Cooling Technologies GPM / Gross MW Output NA3 Reservoir Mechanical Draft Natural Draft *Data from filed ESP and COL Applications PP640.7

8 Wet / Dry Cooling Concept How does it work? Closed cycle cooling system design Dry Tower and water-conserving Hybrid Tower in series Unit 3 s Circulating Water cooled initially in Dry Towers Circulating Water then passed through Hybrid Towers Dry section of Hybrid tower cools incoming Circulating Water and provides warm air for limiting visible plume. Wet section completes the heat rejection using evaporation PP640.8

9 Wet / Dry Cooling Concept How does it work? Two conceptual operating modes Energy Conservation (EC) Dry cooling will be reduced with reliance on hybrid tower for heat removal. Water Conservation (WC) Minimum 1/3 heat removal by Dry Tower, balance of heat removal by Hybrid. PP640.9

10 Conceptual Flow Path & Cycles PP640.10

11 Projected Plant Consumptive Water Use System Average Water Use (CFS) Closed Cycle Reservoir Hybrid Tower Hybrid Tower & Dry Tower (EC/WC) Hybrid Tower & Dry Tower (WC Only) PP640.11

12 Hybrid Cooling PP640.12

13 Hybrid Cooling PP640.13

14 Look to the Future PP640.14

15 Concept Design How much dry cooling? Land Use Cost Power Required Potential impact on turbine performance PP640.15

16 Concept Design How much dry cooling? Comparison of Dry Cooling Percentages Percent Dry Cooling Capacity Approx. Number of Tower Cells Required Percent increased land use (over 33% design) Approx. Dry Tower Cost, 2005 dollars Approx. Electrical Power Required, MWe M M M 50 PP640.16

17 Resulting Performance Bad News The system performs best when normally not needed Cool weather. Approach temperature has significant impact on dry tower performance/duty. Resulting higher circulating water temperature has consequence of higher turbine backpressure lower turbine efficiency lower power output. Remedy? More tower cells Results in higher hotel loads, land use, cost PP640.17

18 Resulting Performance Effect of Ambient Air Temperature on Dry Tower CWT PP640.18

19 Resulting Performance Good News When you really need it, the system can perform Long droughts. Projected annual average evaporation reduced by more than 30% using EC/WC operation. Projected annual average evaporation reduced by 70% using WC only. PP640.19

20 Resulting Performance Percent Decrease (Increase) in Average Water Consumption Vs. Once Through Cooling Design Energy Conservation Only (EC) Water Conservation Only (WC) Proposed Operating Plan EC and WC Dependent on Lake Level Annual Winter (9) Spring Summer Fall Preliminary Data PP640.20

21 Resulting Performance Model Prediction for Time Below Lake Low Level Elevation Existing Units Existing Units Plus Unit 3 with Once Through Design Existing Units Plus Unit 3 with Hybrid Cooling 5.2% 11.6% 7.0% PP640.21

22 Lake Level Hydrograph Open Cycle Cooling PP640.22

23 Lake Level Hydrograph Closed Cycle Cooling PP640.23

24 Summary The North Anna Unit 3 hybrid cooling system: Eliminates thermal impacts to the lake Significantly reduces water use from a once through or conventional wet cooling tower system. Minimizes impact on period of time lake is below low level Provides a balance between environmental stewardship and cost (capital and lost revenue due to reduced plant efficiency/power production) PP640.24

25 Questions? PP640.25