If our days were 48 hours instead of 24 hours, how would affect the average temperature?
Would remain about the same? Would increase average temperature? Would decrease average temperature.

On earth some animals migrate in summer and winter seasons. They don't and can't migrate daily.
How long would a day have to be for animals to migrate in a similar way that animals migrate due to seasonal change?

At the equator earth rotates at about 1000 miles per hour.
Earth circumference is around 40,000 km [the metric system was intended that the meter be 1/40,000 of the earth circumference.] So, 24 divided by 40k is 1666.67 kph [1035 mph]
A 48 hour day rotational speed would be 833.3 kph [517.5 mph].
No animal can travel a 1000 mph nor 500 mph, but they would only need to some fraction of the rotation speed for some kind of daily migration.

If we had a 48 hour day would solar panels make more economic sense. Or would make matters worse?
Would there be more cloud cover or would there be less.
If we had a 48 hour day would the days would hotter in some places- obviously one would have longer afternoon high temperatures, in someplaces [assuming it wasn't raining as it commonly does in the tropics].
Would you get more hurricanes and more severe hurricanes, or the opposite?

If you had less cloudy days, you would get more energy from solar panels. With 48 hour day it would make more sense to track the solar panel to face the sun [or more foolish not to do so].

Changing the length of our day should have a significant affect- but what would these affects be. If you had a longer nite do you sleep more per day and year. Would people drink more alcohol or less? If you drink excessively, nites are generally not long enough:)
But generally would you want to sleep for twice as long as 8 hours per day? Would people sleep around 10 hours at nite and say 6 hours during noon. If you had a 48 hour day would you, could you sleep more than you currently do?

In a 48 hour day would animals devote more effort at nest making- would hibernation more daily basis be more likely as some animals hibernate during the winter. Or would be more on the move?

In a 200 hour day, do you get more creatures hibernating or less?
With 200 hour day. At the equator, the earth rotational speed is 200 kph [124 mph].
At such slow rotation, birds could get our jet lag.
In our 24 hr world we have 24 time zones, for the same time period, the 200 hr world, would have 200 time zones. Daily a bird could cross a couple zones in the same someone flying from NYC to LA could cross a coupe time zones. In such a world herd animal could extend their day by traveling west, and predators could move in waves traveling west or east.