Wind, waves and sun are not zero pollution.But they are certainly are low pollution compared to their competitors. The key about the economics of wind is not that it is cheaper than fossil fuel, but that (even with storage) it is not that much more expensive -- well under double. Given even modest potential for efficiency improvement this means overall energy costs don't have to rise. Photovoltatics are of course much more expensive that wind. But concentrate solar energy, either to drive heat engines, or to run a smaller number of PV cells and the prices drops--especially if you do it out in the desert where there are fewer cloudy days so you get more utilization out of your capital. A lot analysts suggest that if you use the waste heat from desert CSP to desalinate water, the economics gets considerably better.
While a number of pilot CSP plants have been built I don't think anyone has tried the desalinization thing yet. With desalinization you always run into two fairly big ecological problems. One is taking huge amounts of sea water without damaging sea life. (The best solution so far has been to filter the water through sand or gravel just before uptake -- or even to bury the uptake beneath the seabed if the the geography and geology or favorable. This protects sealife but adds to your desalinzation cost.)
The other is disposing of the salt water. (dumping concentrated salt water back into the ocean is very destructive. You can dilute it with many times its own volume in ocean water, or spray it over a very large area. This adds to the energy and cost required for desalinization.)