A 27MW (7,677TR)-capacity heat pump system, comprising four ammonia (R717)-based HicaHP units from Johnson Controls’ Sabroe brand, is the largest of its kind in the Netherlands, according to a statement from Dutch energy company Eneco.
The system recovers residual heat from 65 million liters (17 million gallons) of treated wastewater every day at the HDSR (Hoogheemraadschap De Stichtse Rijnlanden) treatment plant in Utrecht to generate sustainable heat for the local district heating network that serves approximately 20,000 households across the cities of Utrecht and Nieuwegein. An additional 1MW (284TR) of heat is recovered from the heat pump system’s own motors and drives.
It is estimated that the heat pump system, which began operation in September 2024, will meet around 15% of the cities’ district heating demand and reduce the emission of around 30,000 tons of CO2 each year.
A heat exchanger draws heat from the treatment plant’s waste water – ranging in temperature from 12°C (53.6°F) in the winter to 22°C (71.6°F) in the summer – to produce temperatures of up to 75°C (167°F) for distribution through the district heating network.
“Thanks to our partnership with HDSR, we can use heat in a circular process,” said Karen de Lathouder, Chief Operating Officer of Assets at Eneco. “People use heat in their homes, and we then reuse it to supply households with new heat and hot water. This is an excellent way of making our heat more sustainable and accelerating the pace of the energy transition.”
To ensure reliable heating supply, the installation includes a large “heat buffer,” explained Eneco.
Collaboration for efficiency
The system consists of a total of four heat exchangers and eight compressors, each of which is driven by a motor and variable-frequency drive from manufacturer Innomotics. An additional motor has been included to provide “optimal operational flexibility,” explained Innomotics.
“Innomotics’ cutting-edge technology and reliability ensured that we could achieve both high energy efficiency and substantial CO2 savings, making a real difference for our district heating network and the environment,” said Sander Tensen, Manager of Engineering at Eneco, in a press release.
The heat pump system was assembled at Johnson Controls’ Sabroe production facility in Denmark in 2023. The HicaHP portfolio is its latest generation of energy efficient high-capacity ammonia heat pump for industrial applications, according to the manufacturer.
The range covers capacities of 2–7MW (568.7–1,990TR) and is capable of delivering temperatures up to 95°C (203°F). The use of Sabroe’s high-pressure SAB407 screw compressor enables minimal energy consumption, with a system COP of up to 4.2.
Decarbonizing heat
With the goal of achieving climate neutrality by 2035, Eneco is focused on decarbonizing heating with a transition to sustainable alternatives like district heating networks. It is also working to produce heat more sustainably through the use of aquathermal and geothermal energy.
HDSR, Utrecht and Nieuwegein also share an ambition to become climate neutral, Eneco said.
The Utrecht installation addresses both environmental and energy challenges by transforming wastewater into a sustainable heat source, reducing residents’ reliance on fossil fuel-based heating, according to Innomotics.
“This project exemplifies Eneco’s commitment to innovation and sustainability,” said Tensen.
This is one of the latest large-scale ammonia heat pump projects to use wastewater as a heat source for district heating, with other installations recently taking place in Lemgo, Germany, and Malmö, Sweden. The Greater Copenhagen Utility is also currently working on a wastewater heat pump at the city’s Renseanlæg Lynetten treatment plant.
“This project exemplifies Eneco’s commitment to innovation and sustainability.”
Sander Tensen, Manager of Engineering at Eneco
