Colorado Governor Jared Polis campaigned in 2018 on a platform of 100 percent renewable power by 2040. When he won by a healthy margin of over 10 percent, his victory seemed like an electoral validation of the energy transition — a vision that boosted gubernatorial races around the country that year. 

Between the election and Polis’ inauguration, Xcel Energy — the state’s largest utility — announced its own target of 80 percent carbon reduction by 2030 and 100 percent carbon-free electricity by 2050, an ambitious goal but one that had the potential to undercut Polis’ stricter decarbonization targets. 

In the months since, any daylight between the two plans seems to have disappeared. Since Polis took office, Colorado has enshrined seven pieces of clean energy legislation that the administration frames as a roadmap to 100 percent renewables by 2040.

Polis, a Democrat, described a collaborative approach to achieving Colorado’s clean energy ambitions, as he and his adorable terrier Gia addressed Greentech Media’s Energy Storage Summit Wednesday.

“People understand generally and conceptually that this is the way Colorado is going, America is going, the world is going,” said Polis. “There’s temporary potholes along the way — there is, for instance, a lack of federal progress under this administration. […] But again, you see enormous progress at the local level.”

The recently passed legislation does not codify Polis' renewables-only target. The laws boost clean energy planning and adoption, and require a 50 percent emissions reduction by 2030, ratcheting up to 90 percent by 2050. But the legislative program provides a foundation for Polis to continue pitching his renewables-only message, as he did Wednesday. 

“Our goal for the grid is 100 percent renewables by 2040,” said Polis onstage. “It’s aggressive. [...] We want to reach it or be as close to it as we can.”

In practice, however, Colorado is leaving the door open to a broader range of technologies — including those typically defined as “zero-carbon” rather than “renewable.”

“For us, the answer is not coal and natural gas. So what the answer is, is [that] it can be other sources: It can be storage, it can be nuclear, it can be geothermal electric, it can be hydro. It can be all of the above,” said Polis. 

The nuclear option

Energy wonks have spilled copious ink arguing the relative merits of a mandate for an entirely renewable grid, such as the one Hawaii passed, compared to a zero-carbon target like California’s. The debate revolves around the added costs required to power a grid entirely from intermittent resources as opposed to maintaining some power plants that dispatch on command but do not emit carbon.

Barring a major breakthrough in carbon-capture technology, the main resource that stands to benefit from a “clean” rather than a “renewable” target would be nuclear power. Polis’ campaign platform envisions a future without nuclear, but the carbon-reduction legislation and his comments at the conference suggest that technology could play a role after all.

That said, Colorado currently lacks nuclear power, and construction of traditional nuclear plants has ground to a halt in the U.S. Some companies are trying to commercialize small modular nuclear reactors, which could avoid the high capital expense and schedule overruns that plague conventional nuclear development. But that new approach is “just not market-ready,” Polis said. 

“It's been 10 years away for the last 40 years,” Polis said. “I expect in 2020 and 2030 it will still be 10 years away.” 

Until competitive non-carbon-emitting alternatives emerge, the “100 percent clean” versus “100 percent renewable” debate may have more to do with semantics than practical differences. But Polis did note that wind and solar alone won’t suffice. That’s where energy storage fits in.

“We have the workhorses, which based on economics are going to be wind and solar,” Polis said. “And yet we know the wind and solar are not 24/7/365.”

Colorado enjoys a potent wind resource, blowing 300 days a year, he added. But that still leaves 65 days without wind, and the sun goes down every night.

Xcel has already begun procuring large-scale energy storage to provide firm capacity as older coal plants shut down. Indeed, the initial bid prices for wind-plus-storage came in lower than even existing coal generation, Polis said, which may have encouraged Xcel's goal of attaining an 80 percent carbon-free mix by 2030.

In that announcement, Xcel made clear that the company does not see a pathway to complete grid decarbonization with the technology on the market today. But energy storage has more advancement in store, Polis said, especially compared to the various generation resources that have been on the market far longer.

“I'm pretty bullish on storage,” he said. “I think with storage, you have enormous opportunities for...exponential, game-changing-type technological advances.”