Large-scale carbon sequestration remains a big question mark. "I don't think you can go anywhere in the world and see those components operating together, at any utility scale," he said.

Gasification has been around for decades, but removing CO2 and storing it on a large scale needs much more research, he said.

Much discussion has gone on about how long the carbon would be sequestered, he said. "What people don't know for sure is in different geological formations, what will occur?

"How much can a reservoir ... hold of CO2?

"How do you monitor it for leaks?"

Also, he wondered, what would be the regulatory structure governing carbon sequestration?

Carbon dioxide has been pumped underground safely to rejuvenate oil wells. But that is on a minor scale compared with the amount of gas that would have to go into geological domes or other structures underground before power plant CO2 emissions are reduced significantly.

Depending on the pressure needed to move the gas, and the distance it must be pumped underground, "we've seen estimates that up to 30 percent of the power output" of a plant would be used for sequestration.

"There will be a cost associated with it," Walje said. "It's actually a very complex set of equations, and there are some unknowns." These include scale of operations and how fast sequestration can be proved as a viable option. "We think it's not quite as soon as most people think it's going to be."

Rocky Mountain Power is interested in a mix of energy sources and techniques, he said.

"Our biggest concern as a company is that policymakers make decisions that start to take some of these resources off the table."

Long-developed energy sources like natural gas, coal and nuclear power can run on a "base load" scale, meaning 24 hours a day other than down time for maintenance.

"Wind, solar and some of the other technologies aren't as predictable," Walje said. "You can't be sure they'll be there when you need them."

Environmental dream

Kathy Van Dame, policy coordinator for the Wasatch Clean Air Coalition, doesn't believe much in nuclear power or carbon sequestration. They are part of the old ways of doing things, the mass generation approach, she said.

"You have a captive customer base that really doesn't have a lot in the way of alternatives," she said. To utility people, nuclear power is "much closer to their vision of the future, where they take what's worked in the past and project it onto the future."

Nuclear waste is a big problem, Van Dame said. She recalled talking to a nuclear engineer in 1977, "who assured me that that problem was solved or almost solved. 'Don't worry about it. It's not a problem,"' she quoted the engineer.