Deciding Number of Generating Units.

How about sustainable water flow or annual rain fall in its water shed. No use to provide more units then available water.

You must decide how many units will be out of service at the peak load conditions. A minimum is the number of units required to handle the max load plus one. You always have one unit that decides to break down at the worst time.

Snowdon & the Grampians have some excellent guide books. Wainrights books of the Pennines are a great read.

Dear Guest,

Hydro plants are far more reliable than any thermal equivalent and can run for decades with little in the way of major overhauls. Therefore the decision on how many units to instal will be influenced by the available water supply as the turn-down ratio is rather limited as the volute has to remain fully filled and given the fixed speed of rotation the displacement will be substantially constant.

This statement over simplifies the situation as extremely high static head installations do feature turbines with variable geometry runners which permit a greater compliance factor.

If you are only trying to save on imported energy and your water supply is limited and perhaps variable you would not be able to justify more than one machine, as the supply becomes more plentiful a second or even a third may be the economic solution.

I have visited a variety of installations across the Scottish highlands where installed capacity ranges from 10MW up to 80MW. Typically you will find 3 or 4 units providing the output, with sequential operation occurring as the 'despatcher' selects the spinning reserve needed for the load.

Good luck,

Massey.

This is an interesting subject. The total installed capacity depends on the available head and the discharge (water available) for generation. USBR recommends that the no. of units should be symmetrical (i.e., for long penstocks). From my experience, for dam site power houses, you can have more no. of units. But for long penstocks, it is better to limit the no. of units. Can you let us know the available net head and discharge available for power generation? Whether the penstock is short or long with a surge tank? I'll be able to give you a specific reply

Samuel,

The Net Head (H)- 568.1meters, Design Discharge- 16.17 m3/sec, Power-81 MW and Low Flow=1.79 m3/Sec.

Net head (H) in m 568.10 Design discharge in cumecs 16.17 Power in MW 81.07169 Power in MW (rounding off) 81 From the net head available, it is seen that it is a high head plant with a long penstock perhaps with a wye piece. Hence, it will be better to install 2 units, each of 40MW capacity with 10% overload capacity. The type of turbine to be installed can be either Pelton or Francis. Hydro units are very reliable and it is not necessary to have more no. of units from reliability point of view. Further, to have more no. of units, the cost rises exponentially Regarding the low flow period, you can store the water and run it as a peaking station If you need any further clarifications, please let me know Samuel Chelliah

Put in the one that suits averaged inflow volume and average head (allowing for line loss)

If the ones available are too small, put in several.

I don't think anyone has written a book this - as it would be somewhat short.