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Estimation of the energy potential of solar radiation and comparison with normative data for Ukraine

Redko Ihor, Redko Oleksandr I., Redko Andriy, Bakumenko Nina, Ujma Adam, Zadiranov Vadym

Meteorology Hydrology and Water Management. Research and Operational Applications

2025

Vol. 13, Iss. 1

60--73

This article presents the results of an analysis of the long-term variability of average monthly and annual solar radiation in Ukraine from 2011 to 2020. The measurement data are compared with earlier periods and the standard period of 1961-1990. The statistical characteristics of changes in solar radiation are determined. The characteristics of solar radiation are compared with normative data of the National Standard of Ukraine (DSTU-NBV.1.1.-27:2010). In recent years, the annual amounts of direct radiation have increased by 18-23%. The total annual radiation in 2020 was 6% greater than in 1961-1990. Hourly and daily direct and scattered radiation were analyzed with empirical dependencies and engineering calculations. The efficiency of using the sustainable potential of solar energy depends on the climatic characteristics of the specific area or region. Inconsistencies in regulations can therefore create a problem where the best places for energy production lack public interest, infrastructure, and cost-effective consumption. Depending on the regional climatic conditions of Ukraine, the solar energy potential varies from 1400 MJ/m2 in the western regions to 1950 MJ/m2 in the eastern ones. An important characteristic of solar energy resources is the duration of sunshine. For Kyiv, the average monthly duration varies from 180 h in March to 120 h in November. The possible annual duration of sunshine varies accordingly from 4452 h (2011) to 4481 h (2020). The maximum values were observed in June (331 h) and August (334 h).

Parameters of a cascade two-stage air-to-water heat pump at low ambient temperature

Redko Andriy, Ujma Adam, Pavlovskyi Serhii, Redko Ihor, Gvozdetskii Oleksandr, Chaika Yurii, Borodai Dmytro

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

2023

Vol. 12

132-142

The results of the numerical calculation of the thermodynamic parameters of a cascade (two-stage) air-to-water heat pump at low atmospheric air temperatures are presented. A Freon R407c is used in the first circuit and a R152a is used in the second circuit. Calculations are made for ambient temperatures from 7°С to -25°С. The effect of underrecovery temperatures in heat exchange equipment is shown. Cycles with R245fa, R142b, R114, R123, R290, R236fa, R600a refrigerants, a mixture of isobutane and isopentane have been investigated. The effect of the complexity of a two-stage scheme on the efficiency of the cycle has been evaluated. The use of more complex schemes (for example, with liquid injection) does not affect the thermodynamic perfection of the heat pump and may be appropriate only to ensure operational reliability. Reducing the underrecovery temperature to 1K is shown to increase the thermodynamic efficiency of the installation.