Toke seized the career opportunity of a lifetime: Now, he is set to intricately intertwine Power-to-X with a large scale district heating system

Toke Kjær Christensen has embarked on an exciting industrial Ph.D. project with a focus on district heating, PtX, and sector coupling.

Toke Kjær Christensen has embarked on an exciting industrial Ph.D. project with a focus on district heating, PtX, and sector coupling.

An intriguing industrial Ph.D. collaboration between a Danish utility company, a university, and NIRAS is set to venture into uncharted territory. Toke Kjær Christensen will be conducting research on the utilization of surplus heat from PtX.

August 17, 2023

"It's just lukewarm water," says Toke Kjær Christensen with a subdued tone and a chuckle. However, he has embarked on a mission that might turn out to be a breakthrough in the transition to renewable energy.

At the age of 30, Toke has spent the past five years working as an energy planner at NIRAS. But now, an exciting opportunity has arisen. He has started an industrial Ph.D., where he's set to assist Aalborg Utility Company (situated in Northern Jutland, Denmark) in generating entirely new knowledge, and he's become affiliated with a research group at Aalborg University.

The task at hand involves mapping the entire value chain within Aalborg Utility's energy system, as well as investigating and selecting new technologies capable of integrating surplus heat from Power-to-X fuel production into large-scale district heating supply.

"At its core, it's sector coupling. We're working with synergies across various energy disciplines. If we can make the surplus heat from PtX collaborate with the rest of the energy system, it truly becomes valuable," says Toke Kjær Christensen.

"NIRAS engages in a Ph.D. project like this because it will contribute to new and essential knowledge in the energy sector. We need to move away from fossil fuels, enhance the optimal utilization of renewable energy sources, and in this context, we need to improve our capacity to leverage CO2 as a resource – for instance, in power-to-X. We look forward to following Toke's project, which aligns seamlessly with NIRAS's energy strategy, 'GREENsition.'"

says Bettina Skjoldborg, Head of Department at NIRAS.
Toke Kjær Christensen at the coal-fired district heating plant (Nordjyllandsværket), which is scheduled to be phased out by 2028.
Toke Kjær Christensen at the coal-fired district heating plant (Nordjyllandsværket), which is scheduled to be phased out by 2028.


  • Aalborg Utility is the primary funder of Toke's industrial Ph.D.
  • Aalborg University has welcomed Toke into its research group for energy planning.
  • NIRAS co-finances the project and, much like the university, serves as a collaborative partner for Toke.
  • A steering committee has been established for the Ph.D., comprising representatives from all three parties.

The Background of the PhD

Aalborg Utility provides district heating to a substantial number of consumers in the city of Aalborg and its vicinity. The primary heat production takes place at a coal-fired district heating plant, partially supplemented by heat from waste incineration, as well as surplus heat from a large company (Aalborg Portland) and other minor sources of excess heat.

However, the district heating plant is set to be phased out by 2028, and the heat production is to transition to alternative non-fossil energy sources. Aalborg Utility is currently engaged in this process, planning the mix of energy sources that will supply district heating to the inhabitants of Northern Jutland in the future.

A pivotal and innovative component of Aalborg Utility’s upcoming energy mix could be a substantial Power-to-X facility, planned for construction in Aalborg by CIP – Copenhagen Infrastructure Partners. The PtX facility is intended to produce synthetic fuels for the transportation sector, but additionally, the processes at the facility are anticipated to generate significant amounts of surplus heat.

Surplus heat will become important in the energy system of the future

"We need to transition to renewable energy sources. Coal needs to be phased out as an energy source, and we have national CO2 reduction targets. So, how can we best utilize the resources available? In Denmark, we need to significantly improve our utilization of surplus heat, which could become one of the primary sources in the energy systems of the future," says Toke.

And it's precisely this challenge that Toke, with his industrial Ph.D., is set to assist Aalborg Utility in overcoming.

"We are exploring technologies for thermal energy storage with variations in time, season, and perhaps even geography. We're investigating possibilities for direct utilization of surplus heat, or whether the temperature of surplus heat should be raised. In essence, we're examining efficiency rates, supply security, technologies, and economics," he explains.

Toke TKC 3

The Quest for Synergies

Toke embarked on his industrial Ph.D. journey at the beginning of 2023, and as per the plan, his dissertation is expected to be finalized by early 2026. The process will also include an international internship, where Toke will seek valuable experiences abroad.

Engaging with energy systems, development, planning, and synergies is something that the doctoral student eagerly anticipates.

"It's incredibly exciting to be at the forefront of the developments happening in the energy sector. I find it motivating to work with the technologies and uncover synergies. Moreover, being a small part of the grand, long-term progression towards renewable energy sources is something I truly enjoy," he expresses.

Toke TKC 4

Get in touch

Toke Kjær Christensen

Toke Kjær Christensen


Aarhus, Denmark

+45 4299 9225

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