Centrifugal Pump Calculation

Dear Mr.irfanmalik,

You have confirmed that it is a Pumped Storage Scheme, which is pumping water to Reservoir as Motor-Pump Set, during LEAN Demand Hours and working as Turbine(water )-Generator set, during PEAK Demand Hours. The Pump should be designed in such away that it will work as Water Turbine - when the Water is admitted from the Over Head Reservoir.

I give below a Model Caculation. Data below is assumed for Model Calculation.

ASSUMPTIONS: 1. Water Pumping to Reservoir as pump-set = 1,00,000 M^3 in 5 Hrs or 20,000 M^3/Hr. or 5555.55 Kgs./Sec.

2. Head to be Pumped - 50 Metres.

3. Duration of Pumping - 5 Hours.

4. Motor Efficiency - 96%

5. Pump Efficiency - 80%

6. Water Loss% - 0.25%

POWER REQUIRED for PUMPING = (W x H/75) x 1/ ( Motor Eff. X Pump Eff.) where W = Weight of Water/Sec. in Kg., H = Head in Metres, Efficiency is given above.

Water Flow is (1,00,000/5) x 1000/3600 = 5555.55 Kgs/Sec. Hence Power required to Pump = 5555.55 x (50/75) x 1/ (0 .96) x (0.80) = 4822.52 H.P = 3616.89 KW = 3.6168 MW. ……(1)

POWER OBTAINED WHILE WORKING AS TURBINE-GENERATOR

1. Water Available 1,00,000 M^3 x(99.75/100) = 99750 M^3 in 5 Hrs. = 19950 M^3/Hr.= 5541.66 Kgs./Sec.

Power from Reservoir Water = 5541.66 x (50/75) x (0 .96) x (0.80) = 2837.33 H.P = 2127.99 KW = 2.1279 MW …………(2)

Nett Loss of Power is (1) - (2) = 3.6168 - 2.1279 = 1.4889 MW 1.4889 MWHr. For 5 Hrs.

Hence Power Loss/Hr = 0.2997 MW or 299.78 Units /Hr.

BENEFIT: DEMAND and SUPPLY Difference is NARROWED DOWN TO SOME EXTENT.

CAUTION: COST-BENIFIT has to be considered before going for this type of Pumped Storage Scheme. The Efficiency for Pump as well as Turbine will slightly vary and I have taken as Equal for both cases.

I hope now it is clear to you.

DHAYANANDHAN.S