Home Articles DISTRICT HEATING – the key to efficient, resource-saving, green conversion

DISTRICT HEATING – the key to efficient, resource-saving, green conversion

by Linda Bertelsen

The green conversion of the district heating system in Copenhagen and the surrounding area has been underway for many years. Several players – such as the district heating companies CTR, HOFOR, and VEKS – have driven the change in their supply areas.

By Lars Gullev, CEO at VEKS

Published in Hot Cool, edition no. 4/2021 | ISSN 0904 9681 |

In this article, the primary focus will be on VEKS’ development in the supply area, from a production based on fossil fuels to green, sustainable heat production.

Throughout its life, VEKS has saved resources and has thus constantly focused on reducing CO2 emissions.

Excess heat, cogeneration, waste heat, CO2-neutral district heating, climate-friendly heat – many concepts – but what characterizes VEKS’ district heating?

The transmission network in Greater Copenhagen

VEKS is a joint municipal partnership run as a non-profit company. VEKS comprises district heating production, transmission, and distribution in the western suburbs of the metropolitan area. Since its establishment in 1984, VEKS has had the primary purpose of utilizing heat from the combined heat and power plants and surplus heat from waste incineration, larger industrial companies, etc.


When VEKS “went into operation” on October 1, 1987, the purpose was to save resources. The, together with the district heating company CTR, utilized the surplus heat from waste incineration and the large central combined heat and power plants – for VEKS, primarily the Avedore power plant. The first significant step was to connect the local district heating companies in VEKS’ supply area to the transmission network. Thus, fuel oil, coal, and natural gas, previously fueled in the local boilers, could be replaced by district heating from VEKS – a process in 1990.


Excess heat from waste incineration and cogeneration alone has resulted in an annual CO2 reduction of approximately 500,000 tons compared to if the district heating companies had continued to use oil or natural gas for heating.

From 1990 to 2000, VEKS’ efforts to reduce CO2 emissions were, first, replacing fuel oil with light gas oil or natural gas at the central and reserve cargo power plants. Secondly, VEKS’ energy consultancy focused on lowering the return temperature in the transmission network. A lower return temperature reduces heat loss and electricity consumption for pumping and ensures better efficiency at the Avedore power plant. Incidentally, 1990 is the year subsequently used as the reference year to calculate the CO2 emissions from the district heating customers in VEKS’ supply area.

Sustainable biomass

Block 2 of the Avedore Power Plant went into operation in 2001. The heat produced in the new block, based on natural gas and wood pellets, had a decisive influence on CO2 emissions in the coming years.

When the Energy Agreement from 2012 legislatively opened, it was economically attractive for both Orsted and the owner of Avedore Power Plant and VEKS to convert Block 1 of Avedore Power Plant from coal to sustainable biomass.


“That we at VEKS have reached the goal of 70% CO2 reduction already in 2020, you can be proud of – proud to be part of a community that over the past 30 years has had a sustained focus on green conversion. We are on target – and we will do even better in the coming years”, says Lars Gullev, CEO at VEKS.

In the same year, VEKS bought the biomass-fired CHP plant in Koge, covering more than 10% of VEKS’ total heating needs. Since 2016, Denmark’s largest CHP plant, Avedore Power Plant, has produced heat on both blocks based 100% on sustainable biomass and thus displaced the fossil fuels, coal and natural gas.


The biomass conversion on Block 1 alone has resulted in an annual CO2 reduction of approximately 100,000 tons compared to heat production on coal.

VEKS’ customers have reached the goal

With the Climate Agreement from June 2020, a large majority in the Danish parliament decided that in 2030, Denmark should reduce CO2 emissions by 70% compared to 1990. And where does VEKS stand concerning this goal?

VEKS’ supply area has already reached the national goal of reducing CO2 emissions by 70% by 2030. CO2 emissions from a district heating customer in VEKS’ supply area were 58.22 kg / GJ in 1990, while in 2020, we had reduced it to 14 kg / GJ. These numbers correspond to a decrease of 75.9% since 1990. Thus, district heating customers in VEKS’ supply area are already aligned with the national targets, which only apply for 2030. If you are using natural gas, the discharge from your home is still 56.5 kg CO2 / GJ. This number largely corresponds to the CO2 emissions of a district heating customer in VEKS’ supply area in 1990. By converting from natural gas to district heating, it is possible to immediately overtake the national CO2 reduction targets of 70%.

VEKS Projects supporting the green transition

VEKS is involved in several projects that contribute to the green transition – you save resources and thereby reduce CO2 emissions.

CP Kelco

CP Kelco has, in collaboration with VEKS, developed a project where surplus heat covers the heating needs of 2,200 households – connected to Koge District Heating. The focus was initially on lowering the noise level from CP Kelcos cooling towers, whose heating fans made noise when letting the excess heat blow away. This connection changed a burdensome noise problem to a surplus heat project, where VEKS today utilizes the surplus heat in the local district heating system instead of it being sent directly into the blue air in a noisy way as before. The effect of the CP Kelco project constituted approximately 1.5% of VEKS’ total heat purchases and was officially inaugurated on April 9, 2018, by then Minister Lars Christian Lilleholt.


The surplus heat project at CP Kelco alone has resulted in an annual CO2 reduction of approximately 10,000 tons compared to if the customers had continued to use natural gas for heating.

VEKS Gas engine

In the summer of 2015, gas production started at Solrod Biogas A / S, which annually produces approximately six million cubic meters of biogas for VEKS’ gas engine in Solrod. VEKS is involved in the project as a buyer – of the biogas. At Solrod heating plant, VEKS has built a building for this purpose, which houses a gas engine that produces green electricity for the electricity grid via a generator. Simultaneously, the gas engine is converting the cooling water into district heating for the VEKS system.


VEKS’ gas engine generates around 25,000 MWh (25 million kWh) of green electricity annually. The heat from the gas engine covers 1% of VEKS’ total heat sales.

More on the way

Over the years, VEKS has “collected heat” where it made sense, and more is on the way.

In recent years, we have gained experience from a collaborative project on large heat pumps, which also involves VEKS, at the same time as large-scale geothermal energy in the metropolitan area is also a high-priority development area.

VEKS will, together with Hoje Taastrup District Heating, put a 70,000 m3 water pit heat storage into operation in 2021/2022. The project has received EUDP support, which is the supply to support development projects by the Danish Energy Agency. The heat storage unit will utilize the district heating even better, as you store the district heating when it is cheap to produce – conversely, you use the heat from the storage when it is expensive to produce. Therefore, the new warehouse will benefit the total electricity and heat production in the entire metropolitan area and thus also the green transition – mainly because you can reduce the local heat production based on fossil fuels, oil, or natural gas. A total of seven energy companies will benefit from the upcoming heat storage.


The heat storage alone will result in an annual CO2 reduction of up to 15,000 tons.

At the end of 2020, VEKS collaborated with Carbon Capture Cluster Copenhagen (C4) with eight other energy companies – including Copenhagen / Malmo Port – to capture CO2 from several large energy plants in the Copenhagen area. VEKS’ interest in this collaboration is the possibility of utilizing surplus heat from the “CO2 capture process” in the district heating system. The partnership provides an opportunity to catch up to 3 million tons of CO2 annually in 2030, part of which will be biogenic CO2.

Throughout 2021, VEKS has been in dialogue with some data centers that want to establish server hotels in the Copenhagen area with robust electricity infrastructure. The surplus heat from these data centers – large quantities – can be utilized in the district heating system.

At the end of 2021, VEKS has initiated the first discussions with Orsted (owner of Avedore Power Plant) about the utilization of surplus heat from a potential future PtX plant, where the supply of CO2 comes from a straw-fired boiler.

All in all, the district heating system of the future in Copenhagen will use large heat pumps and surplus heat from waste energy plants, data centers, CO2 capture, and PtX factories. An exciting future where district heating will be the backbone of modern society focuses on efficiently using our energy resources.

For further information please contact: lg@veks.dk

Download the Hot Cool article here.

Meet the author

Lars Gullev
Consultant, VEKS