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P3. Rexburg annually averages about 14 inches of precipitation. For calculation

ID: 2269391 • Letter: P

Question

P3. Rexburg annually averages about 14 inches of precipitation. For calculation purposes, assume that all of this precipitation falls as rain. The rain forms as water vapor condenses to form liquid water droplets. (a) Estimate the energy released annually due to release of latent heat, for rainfall of 14 inches on a 1.0 acre building lot. (b) A typical household uses energy at an average rate of about 2.0 kW (including all energy sources) How many households could be supported each year by your answer in (a)?

Explanation / Answer

a) 1acre=4046.86m2

14 inches= 0.3556m

density of water=1000kg/m3

therefore mass of water=volume x density=4046.86 x 0.3556 x 1000=14.39 x 105 kg

latent heat of condensation of water=2260KJ/Kg

means 1kg of water on condensation releases 2260KJ of energy

therefore 14.39 x 105kg of water will release energy=14.39 x 105 x 2260=32.52 x 108 KJ

b) power consumed by one household=2.0KW

means energy consumed per second=2.0 KJ

then energy consumed in one year=2.0 x 365 x 24 x 60 x 60=6.30 x 107KJ

from the amount of energy found by us the number of households that can be supported in one year=32.52 x 108/(6.30 x 107) = 52 (approx)