Concept

Freescoo (Free Solar Cooling) is an air conditioning device fed by low grade solar thermal energy.

It is based on DEC (Desiccant Evaporative Cooling) technology with many innovative aspects that have permitted to realize the simplest solar cooling device in the market. Only using low enthalpy heat, 45-60°C, and water evaporation freescoo treats directly external hot and wet air, to obtain a conditioned stream typically at  20°C and 50% of relative humidity like a typical HVAC system, reducing drastically electrical demand.

A typical freescoo unit for a residential application cools a surface of around 30 m2 with a maximum electrical load of 150 W, that can be reduced up to zero with freescoo stand alone configuration exploiting a little embedded photovoltaic panel.

Freescoo is based on two phenomenon, air moisture physical adsorption and indirect evaporative cooling. First process reduces moisture content of external air up to the desired humidity rate. Low enthalpy heat at 45-60°C, easily produced by flat plate or evacuated tube or thermal waste,  feeds this process. Second process instead reduces air temperature up to supply temperature conditions. Supply water consumption is about 20 lt per day.

Freescoo concept can be easily scaled up to higher cooling demands, thanks to the different system configurations(Air Handling Unit, Rooftop, Ventilation Units).

 

Freescoo Vs conventional solar cooling

 

Main advantages of freescoo respect to available solar cooling device are schematically reported.

Simplicity: we use only water as refrigerant fluid. On the contrary, typical solar cooling devices use ammonia, lithium chloride and other aggressive fluids that require precautions both in design of machine and in maintenance phase.

High performance: typical electrical COP(EER) are around 12-13, increasing up to 50 in the stand alone configuration with the photovoltaic system. Those values are much higher than the ones for a typical heat pump(EER=3). Thermal COP is around 1.1, against values lower than 0.8 of typical absorption machine and traditional DEC solutions.

Use of low grade thermal energy: temperatures around 45-60°C are requested for regeneration of the sorption material. On the contrary absorption heat pumps require temperatures higher than 80°C and typical DEC rotors over 70°C. This means that freescoo can be easily coupled with standard solar thermal collectors or waste process heat.

All-in-one solution: freescoo contains internally solar thermal collector, photovoltaic system and electrochemical accumulators, reducing the use of surface.

Sorption storage: the high amount of desiccant material permits to accumulate solar thermal energy during the day and to use it later after the sunset. This solution avoids the need of any water storage.

Air purification: desiccant material provides air purification from VOC contaminants.

 

How it works

 

  • in first phase external hot and wet air is dehumidified thanks to the passage through CPB (Cooled Packed Bed); now air is dry with a similar temperature;
  • in second phase air is cooled thanks to an evaporative cooling system using an air to air heat exchanger. Typical delivery temperatures of the system are 18-20°C;

dehumcool1

Why heat is used?

 

After hours of working sorbent material reach the maximum moisture content. To continue dehumidification it has to be “regenerated” heating and drying sorbent material with hot air. The heat, thanks to CPB technology does not require high temperature, so can be produced easily by commercial solar collector (air or liquid).

regen2

To guarantee a continuous operation of the system are necessary at least two parallel CPB: when the first dehumidify air the other is in regeneration phase and viceversa. An automatic logic control regulates the system in terms of temperature, humidity and regeneration priority.

Freescoo can storage solar energy (as adsorption capacity) thanks to the great amount of sorbent material and exchange surface respect to conventional DEC systems in which there is not storage possibility. This is an important feature to guarantee continuity on service also in absence of solar radiation for a period between 3-5 hours.

In order to make a fair comparison between the energy performances of Freescoo and other conventional AC system (such as for example split systems), the following concept has to be outlined:
Freescoo guarantees always the adequate air change, whereas split systems cannot provide ventilation. The rate of fresh air can be varied from 30% to 100%.

 

Schematic view of: 1 – ouside ambient air; 2 – inside room air; 3 – supply air.
no air change
Conventional split system Freescoo system