Countries like Germany and the United Kingdom lack ideal year-round sun exposure
ID: 2293208 • Letter: C
Question
Countries like Germany and the United Kingdom lack ideal year-round sun exposure, but they are still the global leaders in installed solar capacity per capita. In Germany, solar photovoltaic panel located on a top of a roof produces the following electrical power in a cloudy and a sunny day.
a. What is the total energy produced by the PV in a cloudy day?
b. ) What is the fraction of the energy loss in a cloudy day?
c. (If an electrolytic cell converts water into hydrogen and oxygen and operates at 50% efficiency, how many 12m*21m PVs are needed to produce 1 kg of hydrogen in a cloudy day? Note that electrolysis of water requires 285kJ.
d. ? Briefly compare the energy production by a PV in a winter day and a summer day if both of these days are equally bright
Time Power (W) cloudy day Power (W) sunny day 06:00 07:00 8 08:00 09:00 | 10:00 11:00 12:00 60 70 5 155 180 13:00 190 14:00 195 180 155 15:00 16:00 17:00 18:00 115 15 19:00 20:00 21:00Explanation / Answer
Part-A
Total power available in a cloudy day = 795 W
Total energy obtained = 795W *14 hrs = 11.130 kW-hrs
Part-B
Total power available in a sunny day= 1467 W
Total energy obtained =1467 W* 14 hrs =20.538 KW-hrs
Energy loss in cloudy day = 9.408 kW-hrs
45% less energy available in cloudy day.
Part-D
In winter day solar light is available for only 8 hours. That window is generally in between 9AM to 4PM.
But for summer days that window is available for almost 15 hours in a single day.
Consider a sunny day for this comparison.
Power extracted in a summer day = 1467 W
Available Energy =1467*14 =20.538 kW-hrs
Power extracted in a winter day =1250W
Available energy =1250*8= 10 kW-hrs
Hence energy available in a summer is almost 50% higher compared to a winter day with similar brightness.