TECHNICAL AND ECONOMIC FEASIBILITY OF OFF-GRID PHOTOVOLTAIC SYSTEMS FOR IRRIGATION

ABSTRACT In rural areas, the electricity supply is affected by problems such as low quality and limited access in some regions. The use of renewable sources, with decentralized generation, can offer an alternative to the existing scenario. The objective of this work is to perform a technical and economic analysis of off-grid photovoltaic systems, without energy storage, intended for irrigation. Photovoltaic systems from different irrigation systems were sized, with power ratings from 0.736 to 29.44 kW. Their technical feasibility was determined based on the energy supply period and the availability of solar radiation as restriction variables. Economic feasibility was determined by the indicators of net present value (NPV), internal rate of return (IRR), benefit/cost ratio (B/C) and profitability index (PI). Feasible operation was found for irrigation systems with motors up to 11.04 kW; however, for systems that required higher powers, the number of operating hours available was less than the minimum required. NPV, IRR, B/C and PI showed increasing values as a function of increasing power. Thus, off-grid photovoltaic systems without energy storage are technically and economically feasible for systems with power of up to 11.04 kW

PERFORMANCE OF ANALYSIS METHODS OF SLOPE STABILITY FOR DIFFERENT GEOTECHNICAL CLASSES SOIL ON EARTH DAMS

ABSTRACT The aim of this study was to evaluate the performance of less accurate analysis methods of slope stability, in order to reduce the number of operations used by the most accurate methods available in the literature. The study evaluated four methods for calculating slope stability. Fellenius (FELLENIUS, 1936), Bishop (BISHOP, 1955), Simplified Bishop (BISHOP & MORGENSTERN, 1960) and Simplified Janbu (JANBU, 1973) were compared with the Spencer method (SPENCER, 1967), which is considered an accurate method for calculating the factor of safety (FS). The procedure was performed in scenarios with different soil groups according to the Unified Soil Classification System (USCS) (ASTM 2011), heights and slope inclinations, and under conditions of reservoir subject to fast and slow emptying. Thus, comparative analyses were made using the correlation index “r”, the accuracy index “d” (WILLMOTT et al, 1985) and the performance index “c” (CAMARGO & SENTELHAS, 1997). The methods that had optimal performance for the analyzed conditions were the Simplified Bishop, the Simplified Janbu and the Bishop methods; the Simplified Bishop method obtained a correlation coefficient of 99%. Thus, they can be used as alternative methods to replace the Spencer method in the analysis of slope stability on earth dams

Agronomic performance of maize hybrids under supplemental irrigation depths

ABSTRACT The choice of a maize hybrid, considering the technology level and irrigation management, contributes to the improvement of the plant productivity and water use efficiency (WUE). Thus, the objective of this study was to evaluate the effects of irrigation depths on production components, grain yield, technical efficiency, and WUE in maize hybrids. The experiment was conducted in Santiago, RS state, Brazil, in the 2015/2016 and 2016/2017 crop seasons, using a randomized block design in factorial scheme, consisting of five irrigation depths (0, 50, 75, 100 and 125% of crop evapotranspiration - ETc) and four maize hybrids in crop season I (2015/2016), and six maize hybrids in crop season II (2016/2017). The number of ears per plant, number of grains per ear, 100-grain weight, grain yield, and WUE were evaluated. The irrigation depths affected the 100-grain weight, grain yield and WUE in both crop seasons, and the number of grains per ear in crop season I. The irrigation depths increased the productive performance of the maize hybrids from 9.9 to 41% when using irrigation depths of maximum technical efficiency, which varied from 90.1 to 105.4% ETc. The AG9025, P1630 and DKB290 maize hybrids presented the best agronomic performances, with grain yields from 13,609.1 to 16,281.3 kg ha-1.</jats:p

Corn yield under various simulated irrigation depths

ABSTRACT Mathematical models are tools to estimate and understand system behaviors against diverse situations; they may help in decision-making through simplified representations of the reality, allowing simulating various scenarios and estimating impacts of different courses of action on production systems, assisting thus in activity planning. Thus, this paper proposed a simulation of corn crop yields according to different field experiment characteristics and weather conditions in which it was conducted, with the purpose of setting a simulation model already calibrated and tested for corn crop cycle in the region of Santiago &#8211; RS, Brazil. The increasing water levels had a positive effect on grain yield and corn dry matter. On the other hand, a level of 800 mm reduced corn yield, as well as water application efficiency decreased from 550 mm. The proposed model can be used as a tool for regional planning in corn crop implementation under irrigation and enables identifying irrigation strategies for high grain yields, being considered a tool for yield prediction in irrigated crops