Assume you were to purchase two 15,000 litre water tanks and put one on a frame

Question

Assume you were to purchase

two 15,000 litre water tanks and put one on a frame 3m higher than the other,a small pump which is 85% efficient ,a small turbine which is 90% efficient when providing a maximum output of 600 watts.

a) What percentage of the input energy needed to pump the water up to the top tank could you recover from the turbine as the water ran back to the bottom tank?

b) What is the maximum amount of energy your water tank system could store?

c) With what velocity would the water be flowing in to the turbine at the moment just before the top tank became empty?

d) If you could get the turbine to output 42W at 12V to light three fluorescent globes how long would they be lit for

Explanation / Answer

a) .85*.9=.765
or 76.5 %

b) E = m g h = d V g h = 1000*15*9.81*3=441450

c) d g h = 1/2 d v^2

v = sqrt(2 g h) = sqrt(2*9.81*3)=7.67 m/s
d)

you can get out .9*441450 = 3*42*t
t=3153 s

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