A large pumped storage scheme for seasonal reliability of national power supply?

Transcription

1 A large pumped storage scheme for seasonal reliability of national power supply? Earl Bardsley (University of Waikato) Bryan Leyland (LCL Ltd) Sarah Bear (URS Ltd) Acknowledgements We thank Contact Energy Ltd and Meridian Energy Ltd for kind provision of generating and discharge data and financial support. 1

2 The dry-year issue Most of NZ power will remain hydro Only 4, GWh storage capacity Insufficient storage to use wet years to offset low inflows later New Zealand Hydro Storage 23-4 Storage (GWh) 45 4, 4 GWh , 2 Electricity savings call Spill 15 Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct Jan Apr Jul Oct

3 Stand-by coal-fired stations? Expensive to maintain No guarantee of new gas finds Increase storage capacity? Capacity increase of about 1, GWh Not possible with existing lakes Pumped storage as an alternative? 3

4 Conventional pumped storage (Small water volumes shifted between upper and lower reservoirs) Load-following for thermal stations Frequency control and voltage support Turlough Hill Pumped Storage Scheme, Ireland 4

5 The Saurdal seasonal pumped storage scheme (Norway) : A model for New Zealand? Energy storage Reservoir level range Upper Reservoir area Tunnel length 7,76 GWh 125 metres 82 km km Clutha River Alexandra Manorburn Reservoir N Location of New Zealand Onslow- Manorburn basin (Central Otago) Lake Roxburgh Roxburgh Dam Roxburgh Lake Onslow 5

6 N Alexandra Manorburn Dam Proposed Onslow- Manorburn seasonal pumped storage scheme Lake Roxburgh Clutha River Tunnel Onslow Dam km Reservoir area: 12 km 2 Energy storage : 12, GWh Level range: 8 m Tunnel length: 2 km Head range: m Southern portion of Lake Onslow 8-metre contour Onslow Dam 6

7 Northern portion of Lake Onslow 8-metre contour Proposed northern dam site 8-metre contour 4 metres Upper Manorburn reservoir 7

8 Simulation As if scheme was in operation Seek to smooth Clutha + Waitaki power yield through dry periods Move existing hydro lakes toward midrange levels (spill reduction) Release (m 3 s -1 ) +15 Discharge or Pumping Pumped storage daily water uptake or release to Clutha River (199-23) Pumped Storage Discharge or Pumping Rates at Roxburgh Dam (m 3 s -1 ) Pumping (m 3 s -1 )

9 Release (m 3 s -1 ) Discharge or Pumping Pumping (m 3 s -1 ) Pumped storage daily water uptake or release to Clutha River (1992 dry year) Pumped Storage Discharge or Pumping Rates at Roxburgh Dam (m 3 s -1 ) Jan July Dec Generating Power (MW) Power (MW) Pumping Pumped storage daily power generated or used for pumping (199-23) Pumped Storage Power Inputs and Outputs (MW) Mean: - 84 MW 9

10 Power (MW) Power (MW) Power (MW) Power (MW) Clutha + Waitaki Power Schemes: Power Output (199-23) Example Simulation of Pumped Storage Smoothing (case of Constant Power Output) Simulation result: Clutha + Waitaki power yield maintained (199 23) Actual Mean: 1269 MW Simulated 1 Mean: MW Cumulative energy gain from alternative lake operating mode (199-23) Cumulative Energy (GWh) 14 12, , Power (GWh) 8 6 4, 4 2 Actual 65 % 75 % 85% Actual Waitaki + Clutha spill losses Recorded Simulated losses with pumped storage Time (years)

11 Water levels of simulated Onslow- Manorburn Reservoir (199-23) Water Level (metres) Water Levels of Simulated Onslow-Manorburn Pumped Storage Reservoir Maximum water level variation: 5 metres Water Level (metres) 536 Lake Level (metres) Lake Level (metres) Lake 1991 Pukaki 1992 Water 1993 Levels 1994 as 1995 Simulated 1996 with 1997 Pumped 1998 Storage 1999 (199-23) Recorded and simulated Lake Pukaki water levels (199-23) Recorded Lake Pukaki Water Levels Recorded Simulated

12 Lake Rotoaira (.5 metre operating range) Lake Moawhango, 15 metres operating range 12

13 Related Benefits of the Onslow-Manorburn Scheme: Spinning reserve and frequency-keeping Supporting wind energy and small hydro Some reduction in Lower Clutha flood peaks Water supply for Dunedin city Onslow-Manorburn pumped storage: Conclusions Energy-neutral Could buffer hydro power output through future climatic variations Reduced hydro lake seasonal fluctuations But would it fit into the market? 13