Performance of solar refrigerating units using ammonia, methylamine, ethylamine, dimethylamine, methanol, and ethanol as refrigerants (adsorbates) and activated carbon as adsorbents has been studied. A mathematical model has been built to determine the level of thermodynamic perfection based on simplified theoretical operation cycle and gradual integration of experimental and calculated values of daily variation of the key parameters of the refrigerating unit. A solar power unit where horizontal insolating tubes and plane mirror concentrators are used has been built and successfully tested.One way of utilizing solar energy (radiation) for refrigeration is to use ecologically safe solar adsorption refrigerating units (SARU).Operation of such units is based on the physical adsorption process in which the molecules of a gaseous refrigerant cluster up over the solid surface of the sorbent, followed by condensation, upon cooling, of the vapor of the refrigerant in the porous structure of the sorbent. This process is reversible, i.e., when heat energy is supplied, the refrigerant (adsorbate) is desorbed from the adsorbent.The flow diagram of the SARU does not differ from that of "dry" solar sorption units [1]. The presence of the solid sorbent predetermines the periodicity (cyclicity) of operation of such a unit. During the day, due to solar heating in the generator, the refrigerant is released (desorbed) from the saturated adsorbent and is accumulated in a receiver upon liquefaction in a condenser. During the night, the refrigerant is adsorbed as the adsorber cools off, whereupon cooling effect is produced in the evaporator.In the SARU, ammonia (NH 3 ), methylamine (CH 3 NH 2 ), ethylamine (C 2 H 5 NH 2 ), dimethylamine (CH 3 ) 2 NH, methanol (CH 3 OH), and ethanol (C 2 H 5 OH) can be used as refrigerants-adsorbates and activated carbon, as adsorbents.In the process of producing activated carbon, hydroxyl (-OH) and carboxyl (-COOH) groups may form on its surface, so the carbon may be both nonpolar and polar and exhibit properties of cations, anions, or ampholytes.The adsorbates containing electronegative elements (oxygen, nitrogen, etc.) may form associates (micelle) owing to formation of hydrogen bonds and the amine and alcohol molecules may exhibit diphilic properties due to polar functional groups (-NH 2 and -OH) and nonpolar radical (-R); the molecules of the surface-active substances may form associates depending on the polarity of the surrounding phase. Having dipole moments, the adsorbates also may form associates on account of electrostatic interaction of the dipoles [2].Based on their basicity strength, the adorbates can be arranged in the following order: C 2 H 5 NH 2 > (CH 3 ) 2 NH > > CH 3 NH 2 > NH 3 > C 2 H 5 OH > CH 3 OH.The base is an electron donor (nucleophile) [3]. Presence of carboxyl groups (-COOH) on the carbon surface facilitates formation of stronger bonds with strong bases.

Results are presented on raising the performance of solar-powered refrigeration plant (SPRP) by accelerating the physicochemical processes and improving the design. Characteristics are given for working pairs involving several salt ammoniates for use in SPRP. Reactions are quoted for the formation of these salt ammoniates together with a physicochemical model for dry absorption-desorption, and a theoretical cycle for an SPRP in the Clapeyron diagram. A theoretical model is presented for a mirror concentrator for solar energy at the surface of a triangular reactor, and solar absorbing conversion coatings have been developed, with recording of the heat-engineering characteristics of sorbents containing traces of graphite inclusions, which intensify the physicochemical and heat and mass exchange processes in the SPRP. An experimental equipment scheme is presented together with graphs showing the measured temperatures at various points in the apparatus in relation to the time of day.Cyclic-operation sorption-type solar-powered refrigeration plant working from the energy of solar radiation is a method of saving traditional energy sources and preserving environmental cleanness.One can use refrigeration plant based on ozone-safe coolants and sorbents for cooling and freezing products and for air conditioning, and also for heating water by heat absorption. We have examined the scope for raising the performance of solar-powered refrigeration plant not only by intensifying the physicochemical processes but also by upgrading the design.The tests were done with an upgraded solar-powered refrigeration plant based on solid sorbents produced at the Astrakhan State Technical University. The operation is based on using natural diurnal temperature differences in the environment and solar radiation in daytime. We can work with the salts of alkaline-earth metals (SrCl 2 , SrBr 2 , CaCl 2 , CaBr 2 , MnCl 2 , BaCl 2 ) and refrigeration agents such as ammonia, ethanol, methylamine, ethylamine, and so on.The generator and absorber 1 (Fig. 1) of combined type consists of the hot box 3 with two-layer shell made of glass (area 1.38 m 2 ) and three horizontal equally separated reactors 2 established within the flat mirrors, which concentrate solar energy on these reactors. A sunlight-absorbing conversion coating is located on the outer surface of the reactors [1]. The apparatus was oriented with the sun-receiving part strictly pointing south and located at 45°to the horizon. The cooled chamber 9 contains a U-form evaporator 8, the lower part of which is immersed in a vessel containing water. The condenser 5 can be used with water or air cooling in accordance with the design. The reactors 2 contain a solid sorbent, and the coolant is contained in the vessel 6. A Russian Federation patent protects the design of the reactors in the generator and absorber [2].