Maintaining the operation of refrigeration compressors in nominal or close modes by selecting a rational design thermal load and distributing it in response to the behavior of the current thermal load according to the current climatic conditions is one of the promising reserves for improving the energy efficiency of air conditioning systems, which implementation ensures maximum or close to it in the annual cooling production according to air conditioning duties. In general case, the total range of current thermal loads of any air-conditioning system includes a range of unstable loads caused by precooling of ambient air with significant fluctuations in the cooling capacity according to current climatic conditions, and a range of relatively stable cooling capacity expended for further lowering the air temperature from a certain threshold temperature to the final outlet temperature. If a range of stable thermal load can be provided within operating a conventional compressor in a mode close to nominal, then precooling the ambient air with significant fluctuations in thermal load requires adjusting the cooling capacity by using a variable speed compressor or using the excess of heat accumulated at reduced load. Such a stage principle of cooling ensures the operation of refrigerating machines matching the behavior of current thermal loads of any air-conditioning system, whether the central air conditioning system with ambient air procession in the central air conditioner or its combination with the local indoors recirculation air conditioning systems in the air-conditioning system. in essence, as combinations of subsystems – precooling of ambient air with the regulation of cooling capacity and subsequent cooling air to the mouth of the set point temperature under relatively stable thermal load.

The processes of gas turbine unit inlet air cooling by absorption lithium-bromide chiller utilizing the turbine exhaust gas waste heat as athermotransformer has been analyzed for hour-by-hour changing ambient air temperatures and changeable heat loads on the air cooler as consequence. The computer programs of the firms-producers of heat exchangers were used for gas turbine unit inlet air cooling processes simulation. It is shown that at decreased heat loads on the air cooler an excessive refrigeration capacity of the absorption lithium-bromidechiller exceeding current heat loads is generated which can be used for covering increased heat loads on the air cooler and to reduce the refrigeration capacity of the absorption lithium-bromidechiller applied. To solve this task the refrigeration capacity required for gas turbine unit inlet air cooling is compared with an excessive refrigeration capacity of the absorption lithium-bromidechiller exceeding current heat loads summarized during 10 days of July 2015. The system of gas turbine unit inlet air cooling with a buster stage of precooling air and a base stage of cooling air to the temperature of about 15 °C by absorption lithium-bromide chiller has been proposed. An excessive refrigeration capacity of the absorption chiller generated during decreased heat loads on the gas turbine unit inlet air cooler that is collected in the thermal accumulator is used for gas turbine unit inlet air precooling in a buster stage of air cooler during increased heat loads on the air cooler. The results of gas turbine unit inlet air cooling processes simulation proved the reduction of refrigeration capacity of the absorption lithium-bromide chiller applied by 30-40 % due to the use of a buster stage of precooling air at the expanse of an excessive absorptionchiller refrigeration capacity served in the thermal accumulator. So the conclusion has been made about the efficient use of a buster stage of gas turbine unit inlet air cooler for precooling air by using an excessive refrigeration potential of absorption lithium-bromidechiller coolant saved in the thermal accumulator

The operation of gas turbine unites significantly depends on the ambient air temperature at the inlet, and the higher it is, the greater the specific fuel consumption is spent for the production of a unit capacity (mechanical/electrical energy), and, accordingly, the more harmful substances are removed to the atmosphere with exhaust gases. To reduce the negative impact of unproductive fuel consumption during the operation of gas turbine units at elevated ambient temperatures, the inlet air cooling is applied. The paper studies the ecological efficiency of gas turbine unite inlet air cooling, taking into account the variable climatic operation conditions for regions with different climatic conditions over a period of five years (2014-2018): temperate climate of Ukraine (on the example of cities Sumy and Ternopol) and the subtropical climate of the PRC (cities Beijing and Nanjing). The annual reduction in emissions of carbon dioxide CO2 and nitric oxide NOX was chosen as indicators for assessing the environmental effect of air cooling. It has been shown that deeper cooling gas turbine unite inlet air to 7...10 °C provides almost a half to two times greater reduction in specific fuel consumption, respectively, and harmful emissions compared with traditional cooling to 15 °C by the most widespread absorption lithium-bromide chillers, and for the temperate climate of Ukraine the relative effect is much greater than for the subtropical climatic conditions of the PRC. Reducing carbon dioxide CO2 over five years for the PRC climate when cooling air to 10 °C is approximately more than 500 t, and for Ukraine – more than 240 t, and NOX nitric oxide – about 3.5 t for China and 1.6 t for Ukraine, while with traditional cooling to 15 °C: more than 300 t for China, and for Ukraine about 120 t, and nitric oxide NOX – about 2 t for China and 0.7 t for Ukraine. Based on the results of a rough assessment of the environmental effect of cooling the ambient air at the inlet of gas turbine units, in the temperate climate of Ukraine, deep cooling of the air is especially advisable, which provides almost twice the effect compared with traditional cooling to 15 °C.

The cold output for the heat-moisture treatment of ambient air in air conditioning systems depends on its parameters (temperature and relative humidity), which vary significantly during operation. To determine the installed (design) cooling capacity of air conditioning system chillers, it is proposed to use a reduction in fuel consumption of a power plant or cooling capacity generation following its current conditioning spending over a certain period, since both of these indicators characterize the efficiency of using the installed cooling capacities of the air conditioning system. To extend the results of the investigation to a wide range of air conditioning units, two methods were used to determine the design cooling capacity (refrigerating capacity): by the maximum annual value and by the maximum growth rate of the efficiency indicator. The first method allows choosing the design cooling capacity, which provides a maximum annual reduction in the specific fuel consumption due to air cooling or maximum cooling capacity generation, which is necessary for air cooling following current climatic conditions. The second method allows determining the minimum design (installed) cooling capacity of chillers, which provides the maximum rate of reduction in fuel consumption by the power plant and the increment in the annual cooling capacity generation following the installed cooling capacity of chillers. The efficiency of air conditioning systems was analyzed for different climatic conditions: a temperate climate using the example of Voznesensk city (Ukraine) and the subtropical climate of Nanjing city (China). It is shown that the design cooling capacity values calculated by both indicators of its use efficiency are the same for the same climatic conditions. Wherein, if to determine the design cooling capacity by both methods - by the maximum annual value and the maximum rate of growth of the indicator, its values turned out to be quite close for tropical climatic conditions and somewhat different for a temperate climate.

Significant fluctuations in the current temperature and relative humidity of the ambient air lead to significant changes in the heat load on the air cooling system at the inlet of the gas turbine unit, which urgently poses the problem of choosing their design heat load, as well as evaluating the efficiency of the air cooling system for a certain period of time. The efficiency of deep air cooling at the inlet of gas turbine units was studied with a change during July 2015–2018 for climatic conditions of operation at the compressor station Krasnopolie, Dnepropetrovsk region (Ukraine). For air cooling, the use of a waste heat recovery chiller, which transforms the heat of exhaust gases of gas turbine units into the cold, has been proposed. The efficiency of air cooling at the inlet of gas turbine units for different temperatures has been analyzed: down to 15 °C – an absorption lithium-bromide chiller, which is used as the first high-temperature stage for pre-cooling of ambient air, and down to 10 °C – a combined absorption-ejector chiller (with using a refrigerant low-temperature air cooler as the second stage of air cooling). The effect of air-cooling was assessed by comparing the increase in the production of mechanical energy as a result of an increase in the power of a gas turbine unit and fuel saved during the month of July for 2015-2018 in accumulating. Deeper air cooling at the inlet of the gas turbine unit to a temperature of 10 °C in a combined absorption-ejector chiller compared to its traditional cooling to 15 °C in an absorption bromine-lithium chiller provides a greater increase in net power and fuel saved. It is shown that due to a slight discrepancy between the results obtained for 2015-2018, a preliminary assessment of the efficiency of air cooling at the inlet of gas turbine plants can be carried out for one year.