Corporate planning officials at Xcel Energy and Duke Energy said in interviews they foresee advanced nuclear reactors, carbon capture and the use of hydrogen among the tools they will need to reach their 2050 carbon-free goals.
Xcel and Duke have already pledged to carry out generation transition plans that would add gigawatts of new wind generation and even more solar generation over the next two decades, largely in an effort to replace coal-fired generation and to supplement both natural gas-fired and nuclear facilities.
However, they, along with numerous other investor owned utilities (IOUs), face the question of how they will be able to boost or transform a generation portfolio enough to offset any remaining fossil fuel-fired generation and reach a net-zero carbon dioxide emissions goal 30 years from now. This is often referred to as getting the remaining 20% of carbon reductions.
Technologies not currently available
Xcel was one of the earliest IOUs to announce it would pursue zero-carbon electricity by 2050. On December 4, 2018, Xcel said it would reduce the company's carbon emissions by 80% by 2030 compared with 2005 levels in the eight states it serves on its way to a 100% reduction by 2050.
The company's chairman, president and CEO, Ben Fowke, called the goals "ambitious," and said Xcel was "accelerating" its push to reach its 100% reduction goal "because we're encouraged by advances in technology, motivated by customers who are asking for it and committed to working with partners to make it happen."
The company previously had a goal of cutting its carbon footprint by 60% by 2030, which it said could be achieved "affordably with renewable energy and other technologies currently available."
But, Fowke said, "achieving the long-term vision of zero-carbon electricity requires technologies that are not cost effective or commercially available today." He said Xcel would work to develop advanced technologies "while putting the necessary policies in place to achieve this transition."
'Storage won't cut it'
According to Frank Prager, senior vice president of strategy, planning and external affairs, Xcel has been considering advanced nuclear reactors as well as the oxygen combustion cycle that takes a pure CO2 stream and prepares it for sequestration. The latter is referred to as the Allam cycle, which is being developed by Net Power.
"These two are leaders in the clubhouse," he said.
"But eventually, a new suite of technologies will be needed," said Prager. "Electricity storage is not going to cut it. We are looking at new technologies, but we still don't have the answer."
A number of other IOUs have mentioned hydrogen as on their list of technologies to watch, while Prager noted that hydrogen "has its challenges."
Prager said in an interview that Xcel began retiring coal facilities and adding a lot of renewables in 2005, and since then reduced has its carbon emissions by 44%.
To get to the 80% reduction level by 2030 it will continue to add renewables, retire coal-fired capacity, employ a conservation plan and, where it can, pursue coal-to-gas to help renewables.
The company has proposed to extend the license at its Monticello nuclear plant to 2040 and will "evaluate if it's appropriate to extend either of the two Prairie Island units in the coming years," a spokesman said.
Retired coal
Duke Energy, on September 17, 2019, announced an updated climate strategy with a new goal of net-zero carbon emissions from electric generation by 2050.
"The company also is accelerating its near-term goal by cutting its carbon dioxide emissions by half or more from 2005 levels by 2030," it said.
The company has said sustained, low gas prices and declining costs for renewables and storage have allowed the company to accelerate its goal to at least 50% by 2030.
Between 2005 and the end of 2019 it reduced carbon emissions by 39%. It has said it has retired 49 coal-fired units totaling 6,190 MW since 2010, "replacing those with flexible natural gas and growing renewables."
Four technologies
According to Sarah Adair, a public policy director for Duke Energy, "it is going to take an evolution" to reach the 2050 goal.
She said in an interview that Duke is today considering four technologies for future use, but others may emerge.
The four, she said, are: advanced, small modular nuclear reactors that could replace the company's 11 GW nuclear fleet after 2050; carbon capture utilization and storage that might be useful in handling industrial emissions; long-duration energy storage that would include not only batteries but also mechanical, chemical and molten salt technologies; and hydrogen.
Adair noted that both GE and Siemens have said they are developing hydrogen-fired or co-fired turbines that may be available for installation in the 2030 to 2035 time period.
GE has said it has combustion technologies that are capable of "operating on a wide range of hydrogen concentrations up to about 100% (by volume) converting a gas turbine to a hydrogen turbine."
Siemens has said that the "ability of gas turbines to burn hydrogen as a fuel will play in a world trending towards full decarbonization and an unfolding hydrogen economy."
