> Renewable energy sources have zero fuel costs.

That's not true. It costs fuel to mine the resourses needed, to build the equipments, to install them, to maintain them. The IPCC states that globally, nuclear power emits _less_ greenhouse gases than hydro and solar, and emits about the same as wind. [1]

[1] https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5... Table A.III.2, page 1335

For more info, please see this eye opening TedX talk on the subject: https://www.youtube.com/watch?v=ciStnd9Y2ak