Interior view Peltier dehumidifier
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  3. Dehumidification
  4. Practical knowledge concerning dehumidifiers
  5. Overview of dehumidification methods
  6. Condenser dryers with Peltier technology

Condenser dryers with Peltier technology

Functional principle, possible applications and usage limits of Peltier dehumidifier

Just like in compressor-operated condenser dryers, a cold surface must be generated inside this type of dehumidifier. The temperature of this surface must lie below the dew point of the air so that water can condense on it. 

Peltier dehumidifiers, however, do not use a compression refrigerant machine to dehumidify the room air but an integrated Peltier element – sometimes referred to as TEC (thermoelectric cooler).

These compact, thermoelectric converters are based on the eponymous Peltier effect which, if current flows between the two parts of the element’s plate, causes one element side to become very hot and the other side to become very cold – with a temperature difference of up to 70 °C between the hot and cold side.

Peltier elements are ultra-compact and are used, for instance, in mini refrigerators, mobile camping coolers or for cooling PC elements.

Peltier condenser dryers have an integrated fan that sucks in the room air and guides it past the cold element side, where it is cooled to below its dew point, condenses at the surface and drips into a collection container.

The dry air is then guided past the hot element side, absorbs the heat and flows back into the room as warm, dry air.

Compact design – limited effective radius

For process-related reasons, condenser dryers with Peltier technology do not require any defrost system and consume little power. Furthermore, they can be designed to be extremely compact and very silent due to the lack of compressor noise.

However, these dehumidifiers have a relatively small operating range and a comparatively low efficiency, currently no more than about one third of a compressor’s efficiency. For this reason, thermoelectrics does not represent a true alternative to the widespread refrigerant compression technology, particularly also because the performance of single Peltier elements cannot be scaled up as desired.

This is why comparative efficiency values – e.g. litres per kWh, as they can sometimes be found for competitive devices – should be taken with a grain of salt. It is like comparing apples to oranges, because Peltier dehumidifiers are not scalable and cannot achieve dehumidification performances anywhere near those of refrigerant dryers. In practice, a 24 hour dehumidification process will not yield more than a small glass of water.

Peltier dehumidifiers and refrigerant dryers can only be compared to a limited extent since they were designed for different ranges of application.

Being a long-time leader in the mobile dehumidification market, we are of the opinion that Peltier devices are only suitable for closed rooms with very small dimensions, for instance closets and shoe cabinets, pantries or small, windowless lavatories.

Peltier devices are not able to permanently dehumidify entire living spaces, even if some advertisements may suggest so.

Side note: In order to upgrade a Peltier dryer in a way that it has the same power as a refrigerant dryer, it would be necessary to install 40 or 80 Peltier elements in parallel in one single device – depending on the desired dehumidification capacity of e.g. 10 or 20 litres in 24 hours.

This would not only tremendously increase the dehumidifier’s dimensions, but also its power consumption. Alternatively, you could of course distribute 40 or 80 individual Peltier devices throughout the room. Certainly an eyecatcher ;-)

Exemplary comparison showing the size of a typical Peltier element as used in small dehumidifiers.
Exemplary comparison showing the size of a typical Peltier element
Cooling fins are screwed onto the cold side of the Peltier element. There the humid air condenses and the condensate drips into the collection container below.
Interior view of a Peltier dehumidifier
Functional principle of a Peltier dehumidifier

Dehumidifier equipment technology – practical knowledge from Trotec

Practical knowledge concerning dehumidifiers – summary of all chapters

Chapter 1: Basic knowledge regarding humidity – relative is everything
Chapter 2: Overview of dehumidification methods – condensation and desiccation
Chapter 2.1: Condenser dryers with compressor technology
Chapter 2.2: Condenser dryers with Peltier technology
Chapter 2.3: Desiccant dehumidifiers
Chapter 3: Which dehumidification method for which purpose?