Cities around the world, including 22 cities in the United States and a growing number in Canada have pledged to go 100% renewable. It’s a noble, collaborative effort to be the cleanest, most environmentally sustainable cities on the planet, with an ultimate and cumulative end goal of each city doing its part to reduce worldwide carbon emissions.
Many cities that have made the pledge don’t yet have a route to an all-renewables, carbon-free destination. Some don’t have ownership of their electricity providers and thus have little or no influence over power fuel sources. Others depend today on energy sources that are based almost entirely on fossil fuel, making the renewables transition particularly difficult. Still others are dealing with high permitting costs for popular renewable options like rooftop solar, as well with other regulatory obstacles. Technologically, anyone switching to a renewables-based grid must, by default, deal with the intermittency and reliability issues imposed by wind and solar. Even hydro electric energy is generally limited by the amount of water flowing in rivers, a quantity that can vary significantly over time.
A broader question, however, is why a fully renewable grid is more desirable than any other combination of zero-carbon energy sources. And what the overall effort and cost would be to decarbonize via that pathway alone.