COOL DH · Project

District Heating at 40°C: Turning Waste Heat into Affordable Building Warmth

energyPilotedTRL 7

Imagine your city's heating pipes run at near-boiling temperatures, wasting huge amounts of energy along the way. COOL DH figured out how to run district heating at just 40°C — roughly bath-water warm — by redesigning the pipes, substations, and in-building systems from scratch. They actually converted a real neighborhood in Denmark from old-style 85°C heating to this low-temperature system, and built new low-temp networks in Lund, Sweden. Think of it like switching from an old gas-guzzler to an electric car, but for an entire city's heating grid.

By the numbers

40°C

Ultra-low district heating operating temperature demonstrated

85/50°C

Traditional district heating temperature replaced in Østerby conversion

Consortium partners across utilities, manufacturers, and municipalities

Countries with demonstration and validation sites (BE, DK, SE)

Total project deliverables produced

Full-scale demonstration sites (Lund and Høje-Taastrup)

The business problem

What needed solving

Most district heating systems run at 85°C or higher, losing massive amounts of energy through pipe heat losses and making it impossible to use low-grade waste heat from supermarkets, data centers, or industrial cooling. Building operators pay more because the system wastes energy before it even reaches them. Cities need a proven way to cut heating temperatures without sacrificing comfort or safety.

The solution

What was built

The project delivered a complete low-temperature district heating system operating at 40°C, including new substations demonstrated in operational conditions, non-conventional pipe materials designed as commercial products, in-building heating systems with renewable energy integration, legionella-safe domestic hot water systems, and new business models with pricing systems. The Østerby neighborhood was physically converted from 85/50°C to LTDH as a full-scale reference case.

Audience

Who needs this

District heating utilities looking to reduce network losses and integrate waste heatMunicipal energy planners transitioning to low-carbon heatingProperty developers building energy-efficient residential districtsPipe and heat exchanger manufacturers seeking next-generation product linesSupermarket and data center operators with surplus cooling heat to sell

Business applications

Who can put this to work

District heating utilities

enterprise

Target: Municipal or private district heating operators

If you are a district heating utility struggling with high return temperatures and energy losses in your network — this project demonstrated a full system conversion from traditional 85/50°C district heating down to 40°C ultra-low temperature operation. They converted the Østerby area in Høje-Taastrup as proof, including new substations and non-conventional pipe materials that are now available as commercial products.

Real estate development

mid-size

Target: Property developers building energy-efficient housing

If you are a property developer designing new energy-efficient buildings and need a heating solution that integrates local renewable energy — COOL DH developed and tested in-building heating systems and controls that combine low-temperature district heating with distributed renewable energy on buildings. New buildings in Lund, Sweden were equipped with these systems starting in 2018, giving you a proven reference case.

Pipe and component manufacturing

any

Target: Manufacturers of district heating pipes, substations, or heat exchangers

If you are a pipe or heat exchanger manufacturer looking for the next generation of district heating products — COOL DH designed and tested non-conventional pipe materials and innovative pipe components specifically for ultra-low 40°C operation. The project explicitly states these components will become new products introduced as a result of the work, with 12 consortium partners validating the designs across Denmark and Sweden.

Frequently asked

Quick answers

What does it cost to convert an existing district heating network to low-temperature operation?

The project data does not include specific cost figures for network conversion. However, COOL DH developed new business models and pricing systems specifically designed to make the transition economically viable for utilities. The Østerby area conversion serves as a real-world cost reference that the consortium can share.

Can this work at the scale of an entire city, not just a demonstration neighborhood?

The project demonstrated both new-build LTDH networks (Lund, Sweden) and conversion of existing areas (Østerby in Høje-Taastrup, Denmark). With 12 partners across 3 countries including major utilities and municipalities, the system was designed for city-scale rollout. The stepwise transition approach shown in Høje-Taastrup is specifically meant to be replicated district by district.

Who owns the IP for the new pipe materials and substation designs?

The consortium includes 7 industry partners and leading industrial manufacturers who co-developed the components. Based on available project data, the new pipe components and substations are intended to become commercial products. IP arrangements would be governed by the consortium agreement — contact the coordinator COWI AS for licensing details.

How do you handle legionella risk at such low water temperatures?

This is directly addressed in the project objectives. COOL DH demonstrated systems for heating domestic hot water without risk of legionella, even at ultra-low district heating temperatures of 40°C. This was a core technical challenge they solved and validated in the demonstration sites.

Does this comply with current EU energy efficiency regulations?

COOL DH was funded under the EU's EE-04-2016-2017 topic on energy efficiency. The low-temperature approach directly supports EU targets for reducing primary energy use in heating. The business models developed include new pricing systems that incentivize low return temperatures, aligning with regulatory direction toward decarbonized heating.

How long does a conversion from traditional to low-temperature district heating take?

Based on the project timeline, design work began in 2017 and heat recovery started in 2019, suggesting roughly 2 years from design to operational heat delivery. The Østerby conversion from 85/50°C to LTDH was completed within the 5-year project period. The approach emphasizes stepwise transition to minimize disruption.

Consortium

Who built it

The COOL DH consortium is unusually industry-heavy at 58% (7 out of 12 partners), which signals strong commercial intent. It is led by COWI AS, a major Danish engineering consultancy, and includes the actual utilities and municipalities of Lund (Sweden) and Høje-Taastrup (Denmark) — meaning the end-users of the technology are inside the project, not just advisors. With partners from 3 countries (Belgium, Denmark, Sweden) and only 1 university, this is clearly an implementation-focused team rather than an academic exercise. The presence of leading industrial manufacturers in the consortium means the pipe components and substations developed here have a direct path to market.

COWI ASCoordinator · DK
LUNDS UNIVERSITETparticipant · SE
LUNDS KOMMUNparticipant · SE
EUROHEAT & POWERparticipant · BE
HOJE-TAASTRUP KOMMUNEparticipant · DK

How to reach the team

COWI AS is a major Danish engineering firm — their district energy division handles COOL DH inquiries. SciTransfer can facilitate a direct introduction to the project team.

Order a report on this consortium See COWI AS profile →

Next steps

Talk to the team behind this work.

Want to explore how low-temperature district heating can work for your network or development project? SciTransfer can connect you directly with the COOL DH team and help assess applicability to your specific situation.

Order a report on this topic More in Energy & Climate