Minnesota appears to be on its way to getting all of its energy from carbon-free sources in the next 30 years. It's all part of the state's efforts to reduce, and then eliminate, greenhouse gas emissions that contribute to climate change.

Gov. Tim Walz has proposed a deadline for eliminating those emissions in electricity production: 2050, the year the United Nations' climate change panel has identified as the critical point at which net global emissions need to be reduced to zero, in order to avoid the most catastrophic impacts of climate change.

But is it possible? And how quickly?

Xcel Energy, the state's largest electricity utility, has set itself on the path toward getting 100 percent of its energy from carbon-free sources by 2050. Major corporations in the state, like 3M, have also committed to eliminate fossil fuels for electricity. And earlier this week, Walz announced a plan to move the rest of the state's utilities toward that same goal, calling it an "economic and moral" responsibility.

Minnesota already has a 25 percent renewable energy mandate, and close to half of the state's electricity comes from carbon-free sources: renewable energy, which mostly comes from wind but also solar and hydroelectricity; and non-renewable nuclear, which doesn't give off carbon. The rest of the state's electricity comes from a mix of coal and natural gas.

Burning coal and natural gas to make electricity results in carbon dioxide emissions. Carbon dioxide is a greenhouse gas, and we care about that because there's a direct link between greenhouse gas emissions and climate change.

And by 2030, Xcel expects 85 percent of its energy in Minnesota to come from carbon-free sources. The company plans to get to that point by using electricity from sources that are already part of its energy mix: wind, solar and nuclear. Like Xcel, other Minnesota utilities are looking to retire coal plants, but they can't match Xcel's pace for decarbonization because they don't have nuclear plants.

But getting to 100 percent carbon-free by 2050? That's where it gets tricky.

"We don't have a total clear direction on how we get there by 2050," said John Marshall, Xcel's community relations director. But he added that the company anticipates it will need to rely on technologies that don't yet exist — at least not on a large scale — in order to get there.

"As we reflect upon technologies and how fast technology has advanced just in the last decade," Marshall said, "we're confident that emerging technologies will help us get there."

A few options: Nuclear fusion. Carbon capture. Flow batteries.

"Flow batteries are really cool," said Ellen Anderson, director of the Energy Transition Lab at the University of Minnesota. "That's an up-and-coming technology that could use things like iron that could come from Minnesota. They can last longer, they can be scaled up and used to save excess wind energy and solar energy and then inject them back into the grid 12 hours later or two days later even."

And even though there is a lot of excitement around adding renewable energy and storage to the electricity mix, Anderson said, there are also a lot of questions about how soon the state can phase out fossil fuels from the electricity sector.

"I think the political debate is going to be challenging to get agreement on doing this quickly," she said.

That political debate continues Thursday, when the state Senate's energy committee will hear a bill that lifts a ban on new nuclear power plants in Minnesota, and next Tuesday, when the state House will hear the bill on the governor's proposal for the first time.

Minnesota appears to be on its way to getting all of its energy from carbon-free sources in the next 30 years. Derek Montgomery for MPR News 2018

Cost and reliability are the two things that tend to hold utilities back from a quick transition to clean energy. When Xcel talks about its transition, for example, the company emphasizes the need to keep electricity affordable for its customers.

Xcel also says that keeping its nuclear plants open until their licenses expire in the 2030s is key to providing reliable power, because nuclear plants run constantly, and are already providing almost a quarter of the state's electricity.

But not all energy experts in Minnesota expect nuclear will play such an outsized role in the state's energy mix by 2050. Nuclear power is expensive — and researchers haven't figured out how to generate large amounts of nuclear power without creating large amounts of hazardous waste.

"I am a bit skeptical about that," said state Commerce Department Commissioner Steve Kelley, "because if you look around today, the costs of new nuclear plants are extremely high and make wind and solar look quite cheap by comparison."

Still, some state lawmakers want to leave the door open for additional nuclear energy. But they'd have to change state law to do it, because Minnesota put a moratorium on the construction of nuclear facilities in the state 25 years ago.

Kelley said the governor's proposal for going 100 percent carbon-free by 2050 leaves space for nuclear to continue to play some role in electricity generation, because what's most important is that Minnesota eliminates the greenhouse gas emissions that contribute to climate change.

"It would leave our children and grandchildren with a cleaner and, I think, lower-cost electrical sector and a broader economy that's cleaner," Kelley said.

But even if state experts, utility companies and environmental advocates find a way to agree on how to move the state toward using 100 percent carbon-free electricity, how it's distributed is also up for debate.

Xcel issued a report this week saying that large-scale, utility-owned electricity generation is the way to go. But others have a very different vision, incorporating new models of local control, like rooftop solar and microgrids.

Entrepreneur Greg Jaczko, who worked as a federal nuclear regulator under the Obama administration and now works on smaller-scale energy systems, said the revolution to eliminate carbon from the electricity sector will need to go hand in hand with a revolution in the way electricity is distributed.

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"I think the concept of a power company or a utility is going to be very different than it is today," Jaczko said, "where a building thinks about generating its own power rather than pulling in power from the broader electricity grid."

Small, large, fast, slow: State lawmakers have a lot to consider as they decide whether 100 percent carbon-free energy is the right policy for Minnesota.

Kelley says it's part of a broader effort to reduce Minnesota's greenhouse gas emissions contributing to climate change.

"The electricity sector is the best place to start, because we have the technology, and recent proposals for new energy facilities have demonstrated that wind and solar can be the low-cost alternative," he said.

Kelley said state officials are also looking at ways to help the state's transportation sector embrace electric vehicles. Minnesota set a goal in 2007 to reduce its total greenhouse gas emissions 80 percent by 2050, but is not on track to reach the goal.