but at leats it remain profitable, maybe because he sold old miners to have the new equipments
It is a neat idea. But going big with this is just not best way as far as profit. Look at all that equipment for 1 S3. I consider solar and bitcoin mining two different investments.
You will make ROI much quicker from finding cheap regular electricity. Then there is no additional equipment cost for something such as solar. I wish solar or wind made sense but just does not large scale compared to moving to the cheap electricity.
The solar technology isn't as far yet as to be able to be worth the hassle and equipment to power a lot of miners, to be honest.
Maybe in the future with electricity probably getting more expensive (think electric vehicles), and more evolved solar powering methods/equipment might make your s5's-s7's run free on solar power and thus generate free money. That would be sweet though.