The Race for Decarbonization in Minneapolis and St. Paul
The operators of the decades-old energy systems that heat and cool buildings in downtown Minneapolis and St. Paul are facing increasing pressure to reduce their carbon emissions. These mostly hidden networks of insulated pipes, connected to centralized heating and cooling equipment, are known as district energy systems. Long touted as an energy-efficient way to heat and cool cities and campuses, especially in cooler climates, many of these systems are still powered by fossil fuels – a problem that can no longer be overlooked as institutions set ambitious goals to eliminate greenhouse gas emissions.
Climate Pledges Drive Decarbonization Efforts
University district energy systems began initiatives to reduce emissions years ago, and now, according to Rob Thornton, president and CEO of the International District Energy Association, “we’re seeing a lot of emphasis on this from cities and towns” as well. In Minneapolis, Cordia Energy, the private company that operates the largest downtown district energy system, is replacing natural gas boilers with electric models. And in downtown St. Paul, officials are seeking federal funding for a project to recover heat from a wastewater treatment plant, reducing energy use for a system currently powered by electricity and biomass.
“We’re doing decarbonization at the rate that our customer base is asking for and we can economically withstand,” said Jacob Graff, Cordia Energy’s north region president. The company’s downtown Minneapolis system serves a diverse range of buildings, from stadiums and high-rises to apartments and medical facilities.
A Centuries-Old Concept with Modern Challenges
The concept of district heating has been around for centuries, with roots tracing back to the networks of hot water pipes built in ancient Rome. Some of the first modern steam-based systems were established in New York in the 1880s. Today, the United States has more than 700 district energy systems heating and cooling buildings in downtowns, universities, medical campuses, towns, and communities.
Cordia Energy’s Minneapolis system, which opened in 1972 to serve the 57-story IDS Center (still the tallest building in the city), now manages seven plants that heat and cool the IDS and more than 100 other buildings, including U.S. Bank Stadium, Target Center, and the convention center. Hennepin County operates a smaller district energy system connected to a downtown trash incinerator, primarily serving county buildings and Minneapolis City Hall.
The District Energy St. Paul system, which began in the early 1980s, has the largest hot water system in the country, serving more than 200 buildings. Together, the two systems in the Twin Cities serve some of the state’s biggest buildings, which have emerged as the largest sources of greenhouse gas emissions in both Minneapolis and St. Paul.
Ambitious Decarbonization Goals
Cordia Energy plans to reduce emissions from its Minneapolis system by 30% by 2030 before reaching net zero by 2050. The company is leveraging Xcel Energy’s green tariff program to offset around half the electricity it uses this year and is exploring options like replacing older engine-driven chillers with electric models.
In downtown St. Paul, the District Energy system is owned and operated by a company of the same name. It has already decarbonized around half of its system through the use of biomass, solar thermal, and renewable energy credits. The company is now seeking a $152 million grant from the U.S. EPA to tap into heat from the Metro Wastewater Treatment Plant, which could produce 60 megawatts of thermal energy and allow the system to source 92% of its energy from carbon-free or carbon-neutral sources by 2028 – far ahead of its 2050 net-zero goal.
“This certainly would be able to accelerate that by 30 years,” said District Energy president and CEO Ken Smith. “From everything we’ve seen, there’s nothing like this, certainly not in the United States, and I don’t believe there’s anything like it at this scale in Canada, either.”
Challenges Facing District Energy Decarbonization
While the urgency to decarbonize district energy systems is clear, a one-size-fits-all solution does not exist. Each system is unique, with its own set of customers and geographic considerations. Not all can be easily or inexpensively retrofitted for electrification, and the ongoing uncertainty in the commercial real estate market due to the COVID-19 pandemic adds financial risk to these projects.
Thornton, of the International District Energy Association, noted that electricity pricing can escalate quickly, especially during the summer months, creating uncertainty in the market. New technologies may also require more space, different controls, and significant staff training.
Jacob Graff of Cordia Energy ticked off several challenges in decarbonizing the Minneapolis system. Geothermal, for example, works well on campuses and in low-slung neighborhoods, but the problem of sending steam to the 50th floor of a skyscraper remains a significant hurdle. There is also no simple, clean power source like natural gas that has the energy density to create and push steam through a sprawling district energy network.
Electrification may be a goal, but offsetting it with clean power is daunting. Cordia would need to install heat pumps capable of drawing more than 400 megawatts from a clean energy source – a formidable task. Hydrogen and biomass show promise, but sourcing enough of these fuels to reliably service a large district energy system remains a challenge. Battery storage, microgrids, and other technologies could play a role, but each brings its own set of cost and implementation concerns.
“We have the economy of Minneapolis in our hands, and regional economics depend on downtown Minneapolis,” Graff said. “We need a reliable infrastructure that people can count on that can be delivered economically, and it’s our responsibility to do that.”
The Path Forward for District Energy Decarbonization
As the operators of these district energy systems navigate the complex landscape of decarbonization, they are exploring a variety of innovative solutions. Cordia Energy is leveraging hydropower from a dam it owns in Yosemite National Park to decarbonize its system in San Francisco, and the company is studying the potential of geothermal technology for its Minneapolis operations.
In downtown St. Paul, the District Energy system’s plan to tap into the Metro Wastewater Treatment Plant’s heat could serve as a model for other cities. By recovering this waste heat and leveraging heat pumps, the company aims to provide 92% of its energy from carbon-free or carbon-neutral sources – a significant leap forward in the race to decarbonize.
While the challenges are substantial, the commitment to reducing emissions is clear. As Rob Thornton of the International District Energy Association noted, “we’re seeing a lot of emphasis on this from cities and towns” as they work to meet their climate goals. The operators of these district energy systems are rising to the occasion, exploring innovative solutions and collaborating with customers and partners to chart a path toward a more sustainable future.
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