- #1
Fendergutt
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Homework Statement
A water heater gathers energy with the help of solar collectors on the roof, where water circulates in pipes and are provided heat from the sunrays that get through a transparent cover. The water is then pumped down in a tank inside the house.
What area must the gatherer have to warm the water in a 200 L (litres) tank from 20 deg. Celsius to 40 deg. Celsius in one hour, if we assume that the system has a coefficient of performance of 20%? (80% of the energy in sunlight is lost, or: ends up other places than the water heater.)
[Answer: 33 m^2]
Homework Equations
Given: the intensity of the incoming sunlight is 700 W/m^2 and the specific heat capacity of water is C_water = 4186 J kg^(-1) K^(-1).
The Attempt at a Solution
Q_water = C_water * m_water * ΔT = 4186 J kg^(-1) * 200 kg * 20 K = 16.7 MJ
I know coefficient of a heat pump given by: η = abs(ΔQ)/ΔW
Right now I'm a little stuck here. Thanks for any help.