GlobalData Power (MIT only)
Data and reports on power/electricity sectors worldwide, including: thermal, wind, solar, hydro, nuclear, smart grid, geothermal, bio, and ocean.
To download data, including latitude and longitude, click on Fundamentals > Power Plants. Use the facets on the side to narrow down the result and click Select. To download, click Advanced Data Export, select a power type, and the fields you want to download (which include lat/long).