you have answered in detail after you wrote the question
It is true that solar energy is not cost efficient at all but of recent, people have started using more of solar power based equipment and it is far more viable than it was earlier.
For example, the whole of the Kochi airport in Kerala, India is run on solar power. The airport is energy efficient and has received many awards from all over the world.
My nephew built a house last year and he has installed solar power panels which is meant for a single house and it did not cost him so much. It also reduces the power bill considerably.
The fact that solar power depends on climate is indeed a dampener but in tropical countries, it would not be a problem at all. Even in monsoons, solar power can be got even though in small measures. Solar power did help a lot when during the Kerala floods, the power lines broke and the system itself had failed. It was used to charge mobiles, emergency lights and so on.
Solar does not produce electricity at night.
It did help a lot of people in spite of torrential rain and floods, when the power lines were cut off.
The dust accumulation reduces the efficiency of the panels ....
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