273 ISSN 0003-701X, Applied Solar Energy, 2018, Vol. 54, No. 4, pp. 273–278. © Allerton Press, Inc., 2018. Original Russian Text © N.R. Avezova, E.Yu. Rakhimov, J.O. Izzatillaev, 2018, published in Geliotekhnika, 2018, No. 4, pp. 49–56. Resource Indicators Used for Solar Photovoltaic Plants in Uzbekistan Part 1 N. R. Avezova a, *, E. Yu. Rakhimov a , and J. O. Izzatillaev a a Physical Technical Institute, Uzbekistan Academy of Sciences, Tashkent, 700084 Uzbekistan *e-mail: avezov@uzsci.net Received February 15, 2018 Abstract—The annual supply of total solar irradiation (SI) to the surface of a randomly oriented photovoltaic panel (PVP) is considered; on this basis, the optimal horizontal tilt for seasonal or annual use is found. A f low diagram is proposed for determining the global total irradiation (GTI) on the surface of PVPs installed in var- iously oriented positions. Surkhandarya region is considered as an example. The actinometric findings obtained from the Sherabad station, as well as the PVP test results, are provided. Keywords: solar irradiation, solar energy, photovoltaic panel, solar photovoltaic power station, global total irradiation DOI: 10.3103/S0003701X18040023 INTRODUCTION The prospects of using solar energy (SE) in Uzbekistan are one of the main areas of development in renewable energy. One of the topical tasks in Uzbekistan’s development strategy is to increase the efficiency of using SE in various branches of the national economy [1]. Because of the need to save pri- mary energy resources, the design, creation, and oper- ation of solar photovoltaic stations (PVS) requires solving many research and engineering tasks. To make use of PVSs in more efficient regions is a very pressing problem, the solution of which will make it possible to improve engineering and economic characteristics of solar power engineering equipment and optimize the energy parameters and operation modes, taking into account variable solar irradiation (SI) energy loads. It is known that the efficiency of using SE in prac- tice largely depends on how accurately the predesign developments are carried out, taking into account the regularities of and specific data on SI supply, as well as in temperature, atmospheric dust content, and wind speeds in the region where the PVS will supposedly be built and used. If actions are taken based on the road map com- piled together with the Asian Development Bank for technical assistance project UZBTA 8008, the task of producing 6% of all the country’s energy through SE by 2030 will be quite realistic; for this, less than 0.1% or around 88 km 2 of Uzbekistan’s area will be required [2]. Consequently, the government has taken specific steps in this regard to attract foreign investments and modern technologies. It is planned to deploy SPVPs with a total ac power of up to 2 GW in Tashkent, Samarkand, Navoi, Jizzakh, Surkhandarya, and Kashkandarya regions [1–4]. Therefore, taking into consideration the country’s territory and various cli- mate zones, it is a critically important task for Uzbeki- stan to reliably assess the SE potential in specific geo- graphical areas. Only when this task is solved will the developers and consumers of solar energy plants have reliable information on determining the possibility of annual electricity production and the operational effi- ciency of SPVPs in the regions in question. This work studies the main effects on the input photovoltaic panel (PVP) parameters, including the orientation, tilt, panel and ambient temperatures, and dirt and dust levels on the front surface. These indica- tors are the basic data for preparing a predesign feasi- bility study of PVSs. SPECIFIC DATA ON SOLAR IRRADIATION SUPPLY The technological capacity of renewable energy sources in Uzbekistan is 176 million tons of oil equiv- alent (TOE), 98.5% of which is the share of SE energy potential. From this perspective, the use in calcula- tions of actinometric data on incoming SI from terres- trial or satellite weather stations affects the accuracy of evaluating the annual production of PVPs at a level of 7–30% [5–10]. According to long-term terrestrial actinometric readings, the intensity of SI across the republic’s terri- tory varies from 1500 kWh/m 2 per year in the Fergana valley to 2100 kWh/m 2 per year in the north. The min- imal and maximum monthly intensity of direct SI SOLAR PLANTS AND THEIR APPLICATION