Thermal Solar Devices

Catalyx has successfully tested a 5-ton prototype absorption type cooler. The device operates on waste heat or solar heat collected via vacuum tube collectors or mirror based concentrators.

We are currently developing equipment based on this successful concept. Our focus is to make self-contained refrigeration units, which can be transported by trucks to remote locations to provide much needed refrigeration for:

1. Vaccines, medications.

2. Preserving perishables such as milk at collection stations.

3. Ice makers in desert locations.

4. Air conditioning for telecommunication towers.

5. Residential/light commercial air conditioning.

Introduction

The requirements for better working conditions and rising comfort demands are the driving force behind a growing market for air conditioning systems today.

An alternative to the currently dominant vapor compression chiller is the sorption cooling system. Conventional compressor air conditioners are driven by electricity, whereas sorption systems are driven thermally, using solar energy or waste heat.

An advantage of the sorption refrigeration system is the use of water or ammonia refrigerant that enhances its environmental acceptance. The profitable use of absorption techniques is limited today to large units and applications where the energy consumption does not play an important role (example: cooling facilities in the RV-market).

Sorption heat pumps for small and medium cooling capacities are not available at present at competitive prices. The question arises as to which requirements have to be fulfilled to increase the economic attractiveness of sorption chillers. The reason for the dominant position of the vapor compression machines in this market is their lower cost in comparison to sorption chillers. The latter require higher investment costs that are caused by components like solution pumps, rectifiers or permanent evacuators. Further more, a conventional absorption system requires low heat rejection temperature to achieve high coefficient of performance. This requires the use of a cooling tower that causes additional costs.

System description

Catalyx has developed sorption chillers with moderate cooling capacities that exhibit acceptable efficiencies at low cost. These chillers operate with ammonia refrigerant and use inorganic or organic salts as absorbers. One advantage of this type chiller is its small size and that is less sensitive to variations of the desorption temperature. In addition the system possesses the capacity to serve as a chill storage. A schematic presentation of the absorption chiller is given in Figure 1. The thermo-chemical compressor consists of two or more reaction vessels that are filled with salt whose adsorption characteristic matches the required thermodynamic conditions

The machine operates in two phases. In the first phase, the chill generation step, the salt absorbs the ammonia from the evaporator step, and the generated heat is removed by the heat rejection system. In the second phase, the regeneration step, the heat from the driving source is used to heat-up the ammoniated complex to decompose it. The desorbed ammonia is then condensed and the process is repeated.

The cyclic operation is made quasi-continuous by the use of two or more equivalent reaction vessels. A sorption chiller with 1 kW cooling power comprising two 5 dm3 reaction vessels and an additional 15 dm3 chill storage vessel are depicted in Figure a. The generated cooling power is used to cool a container by means of wall elements as shown in Figure b. The 1 kW chiller provides the space cooling system with coolant at 16 °C for an environmental temperature of 30 °C and desorption temperature of 70 °C.

a: Complex compound chiller

b: Space cooling wall element