Anenergy efficient household uses 3.2 kWh electrical energy per day.To utilise w

Question

Anenergy efficient household uses 3.2 kWh electrical energy per day.To utilise wind-power they need to be able to

store energy which will then be used to drive an electricgenerator. They are planning to use water pumped to ahigh

tank for energy storage.

a)How much water should they have stored for 2 days supply, if thewater is stored at height of 15 m above the

turbine, in order to store the equivalent to 2 days electricalenergy in gravitational potential energy form?

b)As a person with some understanding of efficiency, you suggest theyinclude a factor for conversion from

gravitational potential energy to electrical energy and togetheryou estimate that from stored tank 67% efficiency.

Onthis basis, how much water should be stored?

Explanation / Answer

Given that    power is P = 11520000 J/day ------------------------------------------------------ a)   We have the formula for the power is                   P = mgh/ t here t = 2 days             11520000 J/d =  mgh/ ( 2 days)       The mass of water stored per 2days is m = (2 days*  11520000 J/day )/(hg) Here h = 15 m Substitute the values. b We have the formula for the energy is               eQ = mgh     The mass of the water is m =(eQ)/(gh) Here Q =  11520000 J            e = 0.67             h = 15m Substitute the values for m

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