There are 2 problems with solar in the tropic zone. One is that there are a lot of very green trees that block the sunlight year round, and would have to be cut down to make room for the solar panels. Solar panels could be located in areas where there are no trees. But there is the second problem. Much of the tropics is covered by clouds for much of the year. That will greatly reduce the output of any solar farm. So the most optimum locations for solar farms are near the deserts such as the Namib and Sahara. But there are areas in Africa where wind would be a better choice than solar. And the wind turbines would take up less land and be the lowest cost per kWh.