Today, 1 September 2026, Cotes celebrates its 40th anniversary.
Cotes was founded on 1 September 1986 as Cotes Luftteknik by Ellen and Søren Rønnow Olesen. What started as a Danish dehumidification company has since developed into an international specialist in adsorption dehumidification and humidity control.
Over the past four decades, we have delivered more than 250,000 dehumidifiers, primarily across Europe.
But the story of Cotes is not only about the number of units we have produced. It is about the problems they have been built to solve.
Built for applications where reliability matters
Cotes dehumidifiers are designed for demanding technical and industrial environments.
That matters because many of the applications we work with form part of critical infrastructure. Our systems are used to protect wind turbines, waterworks, military installations, production facilities and other technical environments where humidity, condensation and corrosion can affect reliability and operation.
In these applications, dehumidification is not simply about creating a comfortable indoor climate.
It is about controlling the physical conditions that can cause corrosion, electrical instability, condensation, ice formation or process problems. This places high demands on materials, airflow control, serviceability, measurement and long-term operational stability.
For 40 years, this engineering approach has been at the centre of how we develop our products.
Innovation driven by real engineering problems
Many of the solutions we develop begin with a specific physical problem.
In battery manufacturing, for example, extremely low moisture levels are required to maintain stable production conditions and battery quality.
Cotes has developed multi-stage Ultradry® systems capable of producing air at extremely low dew points. Systems have been delivered with supply air around -92 °C dew point, while the technology has an engineering capability down towards approximately -120 °C under appropriate conditions.
Just as importantly, the multi-stage principle makes it possible to regenerate the adsorption rotors using lower-temperature heat.
Instead of depending solely on high-temperature electric heating, systems can be designed to use hot water from sources such as heat pumps, district heating or waste heat from other processes.
For large battery factories, this can substantially reduce electricity demand compared with conventional high-temperature electric regeneration concepts. The exact savings depend on the system design, operating conditions and available heat source, but in large installations the potential can be very significant.
Protecting offshore wind against both salt and humidity
Offshore environments create another type of humidity challenge.
Salt aerosols enter structures and settle on surfaces. When relative humidity rises, the salt absorbs moisture and can form conductive moisture films. This accelerates corrosion and can affect sensitive electrical equipment.
Cotes has developed a solution principle that addresses both salt and humidity.
Incoming marine air is treated so that salt can be separated from the air stream, after which the air is further dried and supplied to the protected structure under controlled conditions.
Today, this principle is used extensively for corrosion protection in offshore wind turbines.
The same engineering principle is relevant far beyond wind energy. It is now being applied to other coastal installations, including lighthouses, and has clear potential in naval environments where ships, radar systems, electronics, weapon systems and other equipment must remain operational despite exposure to salt and humidity.
Recovering energy that would otherwise be lost
Energy use has also been a major focus of our development work.
In an adsorption dehumidifier, a large share of the energy input is used to regenerate the rotor. The warm, moisture-laden regeneration air leaving the system still contains useful thermal energy.
By integrating heat recovery, part of this energy can be transferred back to the incoming regeneration air.
Under suitable operating conditions, this principle can reduce annual energy consumption by approximately 20–25% compared with an equivalent system without heat recovery.
It is a relatively simple idea physically: use energy twice before allowing it to leave the system.
Making professional drying easier
Innovation at Cotes is not only about large industrial systems.
We have also focused on making professional drying equipment easier to transport, install and operate.
For damage restoration applications, we have developed lightweight adsorption dehumidifiers designed to reduce handling requirements while still providing professional drying capability.
We have also developed practical installation accessories such as our window kit, which allows the wet regeneration air from a temporary dehumidifier to be discharged through a window with only a small opening.
These may appear to be simple details, but in water-damage restoration, faster installation and easier handling can help drying begin sooner — and ultimately help people return to their homes and normal lives faster.
130 people behind the technology
None of this would have been possible without the people behind Cotes.
Today, we are approximately 130 skilled and committed employees working across Denmark, Poland, Germany and France.
They design our products, build them, test them, sell them, install them, support our customers and continuously look for ways to improve what we do.
Technology matters, but companies do not innovate by themselves. People do.
We are also increasingly using artificial intelligence across many of our internal processes. For us, AI is another engineering and productivity tool: a way of making knowledge easier to access, supporting employees and improving the way we work.
The next chapter: Cotes and CAREL
As we celebrate our 40th anniversary, Cotes is also entering one of the most important new chapters in our history.
Cotes is becoming part of the CAREL Group.
This gives us access to a much larger international organisation, broader geographical reach and complementary technologies and competencies within climate and humidity control.
For our customers, this means a stronger organisation behind future projects, access to a broader service and support network and the possibility of developing more complete solutions.
For Cotes, it means that we can continue doing what we have spent 40 years learning to do: solve demanding humidity problems through engineering.
Only now, we can do it with considerably more resources behind us.
Forty years after Ellen and Søren Rønnow Olesen founded Cotes Luftteknik, the fundamental idea remains remarkably similar:
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Understand the physical problem.
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Develop a solution that works in the real installation.
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Build it to last.
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And keep improving it.
Thank you to our employees, customers, suppliers and partners who have been part of the first 40 years.
Thomas Rønnow