How much power can Solar Power give?

The main advantage to solar energy is that, unlike fossil fuels, it is inexhaustible. Not only that but there is little to no harmful emissions associated with renewable energy. Wind power is a form solar energy as well. Currently solar power is used for residential homes primarily. Flat solar panels feed energy into the cities power grids, effectively running the homes meter backwards for as much power as the panel produces. To answer your question about the tower, it is estimated that a tower that would produce 100 MegaWatts would have to be 1000 m high and 20 KMs in area. The largest one currently constructed can power about 10,000 homes (http://www.treehugger.com/files/2009/04/worlds-largest-solar-power-tower-spain.php). To give you a scale coal plants produce about 3.5 gigawatts in comparison. Currently wind energy shares a similar efficiency rating (20.3%). But countries like China, Germany, and the United States all produce 25+ Gigawatts of power through wind farms. Currently it seems unfeasible to run a city on only solar energies. There are other renewable resources such as tidal energy and geothermal energy but those are rather lacking as well. Look into nuclear energy because it is rather efficient and with the proper safety methods and waste disposal methods, it can be considered a good alternative to fossil fuels. Hope that helps.