> Isn't total "total daylight time per year" constant across the earth?
More or less (depending on how you measure).
Issues:
1) Storage. If you live at lat 65 you need extreme amounts of heat and lighting in winter, and you need almost no heat and lighting in summer. Massive seasonal energy storage solutions such as aquifers do exist but they are expensive. This is why hydro is so good - it's both renewable AND is perfect for seasonal storage.
2) Incidence. Total daylight that has a good incidence for catching isn't constant across the earth. A lot of the "extra" sunlight that northern finland gets in the summer is in the wee hours of the night. It's not exactly scorching from zenith then. When the sun sits ON the horizon for a few hours, even a small hill on the horizon will ruin your solar power.
I would also hazard a guess that the closer to the horizon the Sun is located, the more atmosphere it needs to cross to reach you (because of the lower angle) which results in higher absorption rate before it reaches you (simply said, it's a bit darker the closer you get to the poles). I'm mostly guessing though, so please correct me.
ps: I remember seeing the sun in northern Norway at midnight in the summer long time ago when I was visiting. Was just a little bit brighter than the moon usually is.
pps: This is the same effect as what the sun looks like just before sunset around the rest of the world.
More or less (depending on how you measure).
Issues:
1) Storage. If you live at lat 65 you need extreme amounts of heat and lighting in winter, and you need almost no heat and lighting in summer. Massive seasonal energy storage solutions such as aquifers do exist but they are expensive. This is why hydro is so good - it's both renewable AND is perfect for seasonal storage.
2) Incidence. Total daylight that has a good incidence for catching isn't constant across the earth. A lot of the "extra" sunlight that northern finland gets in the summer is in the wee hours of the night. It's not exactly scorching from zenith then. When the sun sits ON the horizon for a few hours, even a small hill on the horizon will ruin your solar power.