Energy savings with Munters’ internal rotor energy recovery systems

Do you happen to have one of the many older and still steadily running Munters dehumidifiers operating in your facility? Like Munters and most other environmentally concerned companies, you might also be focusing on reducing the energy consumption and carbon foot print? If YES, Munters can provide retrofit solutions to optimize the energy efficiency in these older units, securing energy efficient operation years ahead.

How to cut the energy consumption for reactivation by up to 25%  

Since the majority of the energy required for the desiccant process is used in heating the reactivation airstream, significant energy savings are achieved by recovering the energy in the reactivation cycle.

Internal energy recovery systems for the rotor reactivation process can be installed retro fit in a wide range of bigger dehumidifiers (e.g. MX, MA, MCD, ICA, MTS & MDU Series) offering energy savings up to 25%, typically with a short ROI of around 2 years or less.

The Purge sectors can easily be installed on site by our skilled Service Teams and does not involve any external rebuilding – most of the work is done inside the dehumidifier itself.  



Munters standard desiccant rotor design                       

The Munters desiccant rotor (wheel) works on the principle of sorption, which is the adsorption or the absorption process by which a desiccant removes water vapour directly from the air.

The air to be dried passes through the rotor and the desiccant removes the water vapour directly from the air and holds it while rotating.

As the moisture-laden desiccant passes through the reactivation sector (90° shielded part of the rotor surface), the water vapour is transferred to a heated airstream, which is exhausted to the outside.

This process is continuous, allowing for highly effective and uninterrupted dehumidification.

In this continuous process the rotor is carrying heat into the process airstream. It is this energy that we recover and re-use in the reactivation cycle, resulting in lower energy costs in reactivation power and post cooling.

We offer different types of internal recovery systems, individually designed for the different series of dehumidifiers.


Energy Recovery Purge (ERP) – Reduces energy needed for reactivation


When upgrading the dehumidifier with the ERPsystem, an extra sector on both sides of the desiccant rotor will be added. This extra sector is placed on the process side where the rotor leaves the reactivation chamber. Fresh air from the reactivation inlet (1)  will go through this purge to remove the heat from the rotor material and mix this recoverd waste heat with the reactivation air after the heater (2).

Hereby we can reduce the size (and power consumption) of the reactivation heater and still grant the same dehumidification performance. As the ERP removes heat from the rotor material, the process air (3) temperature will be reduced, securing substantial savings in cases where post cooling is needed.           

The ERP can be installed retro fit on dehumidifier MX, MDU and MDS Series.

• Reduced reactivation energy costs by up to 25%
• Reduced post cooling energy costs
• Reduced carbon footprint
• Less expensive compared to external heat recovery
• ROI of within 1 to 2 years
• Standard kit available for MX, for easy installation


Pre Purge – internal energy recovery in open systems

For MX series dehumidifiers operating in open systems (dehumidifier is placed outside the dehumidified room and does not recirculate the air), the PrePurge is an easy-to-install energy recovery purge solution.
The PrePurge only includes one purge sector, leading warm process air from the rotor into the reactivation air stream (1). Hereby a part of the fresh air for reactivation (2) is replaced with warmer air, reducing the energy supply needed for the reactivation heater.


• Reduced reactivation energy costs by up to 25%
• Reduced post cooling energy costs
• Reduced carbon footprint
• Easy to install
• ROI of within 1 to 2 years


Other Purge options:

Munters has also developed Purge sectors enhancing the capacity of the rotor itself. Retrofit Low Dewpoint purge for dehumidifiers in applications where a low dewpoint is required and the Energy Efficiency Purge (EEP) that boosts the performance of the rotor still with the same amount of energy used.

Please contact your local Service Team for more info.



PowerPurge™ - tailor made purge sector for rotor diameters at minimum 1,3m

For dehumidifiers type MDU and MDS where the inlet water content is lower than 12g/kg, the PowerPurge™ will efficiently recover heat inside the reactivation sector itself.
The unique and patented PowerPurge™ system collects waste heat off the hottest section of the desiccant rotor (wheel) and uses that heat to help with the reactivation cycle of the rotor. This reduces the energy supply required for reactivation while lowering the discharge temperature of the process air, decreasing energy costs for eventual post cooling.

How does it work?
One extra purge sector is added on each side of the standard reactivation sector of the rotor, positioned both before and after this sector. A separate air stream (1) recirculates in a closed loop. This air circuit cools the rotor material before it enters into the process air stream. This recovered heat pre heats the rotor material in the second purge sector, before it enters the reactivation sector.
This is a very efficient way to reduce the energy needed for the reactivation heater.


• Reduction of installed reactivation heater capacity - up to 30%
• Reduced postcooling energy costs
• Improved drying performance
• ROI of within 1 to 2 years
• Reduced carbon footprint
• Patented technology
• Tailor made on site



Case studies documenting huge savings

We have published a number of Case Studies on purge installations. Read more here:

Coloplast, Denmark (Energy Recovery Puge)

Niko, Belgium (Energy Recovery Purge )

Ice Centre North, Denmark (Energy Recovery Purge)


Other upgrade options available

Performance Check
Munters' Performance Check will clarify the performance of the desiccant rotor. Based on the Performance Report issued, our Service Team will advise on recommended actions.

Energy Check (consult your local Munters Service Team to check availability)
An Energy Audit goes beyond the dehumidifier and is a 360° audit of both dehumidification system and the complete installation as such. This extensive audit will provide you with recommendations on amendments and upgrades that will grant you better capacity and energy efficiency.

Energy source conversion
In case alternative and less expensive energy sources have become available since the commissioning of the dehumidification system, it can often be beneficial to convert the reactivation energy source from e.g. electricity to gas or steam. The lower energy costs secure a short ROI and reduced CO2 foot print.

Dual reactivation
When waste energy is available, a redesign of the dehumidification system can often secure substantial energy savings, utilizing the waste energy for the reactivation air stream. Based on an analysis of configuration, set-up and control systems our Service Team will evaluate the profitability and calculate savings.

Control options
A number of advanced controls options have been developed that allows for retrofit installation. Update of control systems allows closer control and can be connected to existing MBS systems. Modulating controls enables more energy efficient operation, and alarm options will improve safety.

Contact your local Munters Service Team for more information!