Hoover Dam Hydropower and River Operations Electric Market Forecasting Conference. Mark Cook, PE Manager, Hoover Dam

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1 Hoover Dam Hydropower and River Operations Electric Market Forecasting Conference Mark Cook, PE Manager, Hoover Dam

2 Hoover Dam Type of Operation Impacts of Drought Mitigating Drought Impacts through Major Modifications and Improvements

3 Peaking Plant 17 Main Generating Units 2 Station Service Units 2074 MW Nameplate Rating Releases 9.6 Million Acre feet per year Generates about 3.5 Terawatt hours per year

4 Boulder Canyon Project Act Authorizes [t]hat the dam and reservoir provided for by section 1 hereof shall be used: First, for river regulation, improvement of navigation, and flood control; second, for irrigation and domestic uses and satisfaction of present perfected rights in pursuance of Article VIII of said Colorado River compact; and third, for power.

5 Operation of Lake Mead and Hoover Dam Two modes of operation govern the releases from Lake Mead Flood Control (releases in excess to downstream water delivery requests) Meet the downstream water delivery requests Flood Control operations governed by U.S. Corps of Engineers regulations 5

6 Operation of Hoover Dam Monthly energy targets are disaggregated into each contractor s share by Western Each contractor schedules its energy to meet energy demands on a real-time basis Monthly gross energy target is met within ± 2 percent Reclamation may change monthly gross energy target within the month based on system conditions 6

7 Hoover s Versatility Black Start Capability Ramping Full Range Up or Down Spinning Reserve - Motoring Non-Spinning Reserve Quick Startups 7

8 LOAD RANGE(MW) Typical Hoover Hours of Operation HOURS OF OPERATION

9 CAPACITY RANGE Typical Capacity Hours of Operation , , HOURS OF OPERATION

10 Energy Allocations Arizona, 20% California, 55% Nevada, 25%

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12 Impacts of Drought The worst drought on record since the early 1900s reduced the generating capacity of Hoover from 2074 MW (lake elevation 1165) to presently 1576 MW (lake elevation 1082).

13 Constraint Expectation 1050 ft All units will have decreased power capability and efficiency 11.5 units can operate, but we expect little to no regulation ability at the high efficiency top end With low tail water submersions, cavitation damage will occur when operated above the rough zone 4.5 units will have regulation ability, but will have minimal rough zones Estimated Plant Capacity: 1371 MW

14 Constraint Expectation ft All units will have decreased power capability and efficiency 11.5 units can operate, with minimal operational regulation below the rough zones Cavitation damage is expected at high loads all tail water elevations 4.5 units will have regulation ability at the top end, but with larger rough zones Estimated Plant Capacity: 1046 MW

15 Constraint Expectations 950 ft All units will have decreased power capability and efficiency 11.5 units may be able to run, but with cavitation or vibration damage at any load 4.5 units will have minimal regulation ability at the top end due to rough zones increasing and capacity decreasing With low tail water submersions, none of the units will be operated at full load Estimated Plant Capacity: 696 MW

16 Impacts of Lower Lake Elevations Loss of Total Generation Capacity Loss of Ability to Regulate Decreased Energy Output Increased Rough Zones Increased Maintenance (cavitation) Concerns

17 Mitigating Low Lake Elevations Efficiency and Capacity Improvements Unit Controls Modernization Major Overhauls of Turbine Components Stainless Steel Wicket Gates Opening Existing Wicket Gates beyond 100% Wide Head Range Turbine

18 Old Control and Relay Panels Relays for unit control, solid state relay protection, analog meters, pistol grip manual controls, and window type annunciator for alarms

19 New Control and Relay Panels TMC TPC GPC UCC DCDC Programmable logic controller for unit control, digital relay protection, touch screen for manual control, monitoring, and alarms

20 UCM Project Performance Benefits UCM improves efficiency while units are providing regulation for the power system. Faster operating mode transitions such as starting and stopping a unit Faster changing from condense mode to generate mode Faster transition/loading through the unit rough zones Faster load-following response.

21 Wide Head Turbines 5 Turbines Total 4 Full Size 1 Half Size

22 Wide Head Range Turbine Benefits Improved efficiency and wider regulating capability during low head operation Improved regulating capability, by reducing or eliminating the load ranges which produce rough zones Provides capability for capacity and regulation from Hoover at low lake levels, mitigating the risk of losing capacity, regulation, and unit availability, due to rough unit operation

23 Wide Head Range Turbine Design Concepts Operate at higher efficiency and increased capacity, over an effective head range of 350 feet (Lake Mead elev. 1004) to 575 feet (Lake Mead elev. 1229) Designed to operate over the entire effective head range, the best operation will be across the expected head range, from net head 396 (Lake Mead elevation 1050) to 511 feet (Lake Mead elev. 1165).

24 Unit Efficiency (%) 100 Unit A8 Unit Efficiency History Pre-Overhaul Performance Testing Post-Overhaul Performance Testing New Runner Priliminary Performance Testing Unit Power (MW)

25 A1 Turbine Installation

26 Wicket Gate Stainless Steel Replacement Wicket gates at Hoover Dam have extensive cavitation and erosion damage. There is also damage and wear to the bearing areas. Prior repairs (to the nose and tail of the gates) have created differences in flow patterns across the gates. An economic benefit/cost ratio and payback period for replacing the wicket gates versus refurbishing the wicket gates was conducted along with a computational fluid dynamics (CFD) analysis.

27 Wicket Gate Stainless Steel Replacement Condition of old wicket gates

28 Wicket Gate Stainless Steel Replacement Benefits from installing new stainless steel wicket gates Increasing Efficiencies with Better Flow Profiles Increasing Power Output Capacities by Allowing More Water to Pass Through Gates Avoiding Costs Due to Water Leakage when Units are shut down Avoiding Higher Condensing Costs Which Result from Water Leakage During Condense Mode

29 Wicket Gate Stainless Steel Replacement New Stainless Wicket Gates

30 Stainless Steel Wicket Gates and Widehead Turbine

31 Overall Results Faster Response Better Alarming More Spinning Reserve Capacity Higher Efficiency Better Reliability

32 Capacity in Megawatts Lake Mead Elevation Hoover Capacity with and without Wicket Gate Modifications As of 2016 The Total Increased Capacity = 105 MW Jun-98 Sep-02 Feb-05 Jun-06 Jul-07 Apr-08 Apr-09 Feb-10 Jan-11 May-11 Aug-11 Nov-11 Dec-11 Date Capacity with Wicket Gate Changes Capacity without Wicket Gate Changes Lake Mead Elevation

33 10 Year Annual Hoover Plant Efficiency 88% 87.5% 87.3% 87.1% 87.0% 87% 86% 85% 84% 83.3% 83.5% 84.1% 84.5% 84.7% 83% 82.6% 82% 81%

34 QUESTIONS?