The Absorber Box by Watergy, a company from Berlin, Germany, uses humid air as a source of energy. The air conditioning system can heat or cool air, thus controlling the humidity and temperature using a saline solution for intermediate storage, which saves energy. The project, supported by funding from the German Federal Ministry of Economics and Technology, is now in the market for beta-testers.

The air conditioning system can be used both for ventilation with heat recovery and for humidity control, as well as to humidify air and cool buildings. Therefore, it is just as suitable for offices and classrooms as it is for hospitals or museums - any buildings with high standards of constant humidity or industrial halls with significant humidity. Depending on the application, incoming or outgoing air can be dehumidified. The energy released in this way is used to recover, provide or dissipate heat. Evaporation processes are used for cooling or to optimise room humidity.

The Absorber Box uses the principles via which water evaporates and condensates in two coupled air circuits. A hygroscopic saline solution in the device combines absorption and desorption processes, in which the saline solution forces changes between the steam and water phases. For heating, heat is provided directly via the dried air, or stored in the saline solution. For cooling, the heat can be dissipated specifically via temperature increases which occur on absorption.

The air conditioning device will create excellent air quality, as it regulates moisture and absorbs dust and pollutants from the air in the brine. The high salt content of the absorption solution acts as an antiseptic to eliminate bacteria.

No cost “assault”

Watergy managing director Martin Buchholz installs his Absorber Box either centrally in the ventilation cellar or decentrally in various storeys or individual rooms: “The advantage of a decentral solution is the greater proximity for ventilation. On the other hand, decentral devices can absorb humidity in circulation mode and return heated, dried and clean air to the room.”Cost advantages arise in ongoing costs due to the lower energy requirements compared with standard full air conditioning systems, as the Absorber Box uses the energy concealed in sources of moisture such as exhaled air or steam. In phases of high humidity, the water can be stored in the brine and emitted again in dry phases to increase the quality of the air in the room.

In summer, this allows significant energy savings via passive drying of incoming air and utilisation of temperature fluctuations between day and night. “However, this function requires an additional thermal storage tank to absorb the thermal load during the day,” adds Buchholz. “If installed decentrally in buildings with few occupants, the external air rate required can be reduced via circulation. This further decreases the heating requirement and energy losses through ventilation. Decentral installation also reduces the ventilation distances and decreases energy consumption compared with central ventilation systems.”

The combination of multiple building services equipment components also reduces investment costs: heat recovery, humidification and dehumidification are performed throughout the process. No other spray or steam humidifiers and hygiene filters are required. The large contact surface between the brine and air in the Absorber Box can even replace underfloor heating in very well insulated buildings.