Originally Posted by
Snoopy
1.6GWh (storage capacity at Roxburgh) = 1,600MWh
The Roxburgh dam can provide 1,600MWh/200MW = 8 hours of equivalent wind energy storage (using Jantar's figures).
Roxburgh has a maximum generation capacity of 320MW. So the 1,600MWh storage capacity will be emptied in:
1,600MWh / 320MW = 5 hours (maximum discharge rate). Of course, hydro does not run flat out all the time. A 60% utilisation rate would see that the storage at Roxburgh empties in:
5 / 0,6 = 8.333 hours,
which very neatly matches your 200MW Wind Energy buffer. Jantar.
But if the output of the Clyde dam feeds the Roxburgh dam, and Clyde is of larger capacity, why can't Clyde replenish Roxburgh as it empties (should that be required)?
For Clyde, 6,000MWh / 200MW =30 hours
So really you can store 30+8 =38 hours of wind energy in the Clyde/Roxburgh system.
Jantar you say:
"The only true storage on the Clutha scheme is at Hawea, but that has such severe ramp rate and flow restrictions that changes in outflow must be made 15 - 24 hours before the water is either required, or no longer required, at Clyde."
But if the storage in Roxburgh/Clyde is kept at at even half of its maximum level (19 hours of storage) and water is short, that means there is enough time to bring the storage at Hawea into play should the coupled wind energy projects not deliver. So why is it not realistic to regard Hawea, Clyde and Roxburgh as part of a giant Clutha River battery?
Isn't that theoretical buffer capacity for windfarms at Onslow modelled around the wind generation capacity being on or off? As more wind farms spread up around the country, isn't it less likely that they will all be generating together, or, on the other side of the coin, be becalmed together?
SNOOPY