RESUMO As energias renováveis são alternativas para substituição dos combustíveis fósseis sendo crucial para a sustentabilidade do setor agrícola, e importante alternativa para o bombeamento de água na irrigação. Assim, a compreensão das receitas e despesas são fundamentais na viabilidade econômica. Com isso, o objetivo do presente estudo foi verificar o comportamento dos indicadores econômicos em sistema de energia solar off-grid para irrigação com base em diferentes cenários. Foram desenvolvidos projetos fotovoltaicos para diferentes potências de irrigação variando de 0,736 até 22,1 kW, e avaliado os custos para implantação e operação, a ocorrência de economia de escala e verificado o custo nivelado de energia para cada potência analisada. Além disso, foram realizadas análises de sensibilidade, considerando a variação do preço de produto e custo de investimento, para demonstrar as respostas em relação aos indicadores econômicos. Portanto, os projetos de energia fotovoltaicos apresentaram custos crescentes com aumento da potência, e o custo normalizado por kW seguiu uma economia de escala, já o custo nivelado de energia demonstrou viabilidade, exceto para a potência de 22,1 kW. As análises de sensibilidade demonstraram a rentabilidade para as configurações analisadas.

ABSTRACT Renewable energies are alternatives to replace fossil fuels and are crucial for the sustainability of the agricultural sector, besides being an important alternative for pumping water in irrigation. Thus, understanding revenues and expenses is fundamental in economic feasibility. Therefore, the aim of this study was to assess the behavior of economic indicators in off-grid solar energy system for irrigation based on different scenarios. Photovoltaic projects were developed for different irrigation powers ranging from 0.736 to 22.1 kW, and the costs for implementation and operation, as well as the occurrence of economy of scale were evaluated, and the levelized cost of energy for each power analyzed was determined. In addition, sensitivity analyses were performed, considering the variation in product price and investment cost, to demonstrate the responses in relation to economic indicators. Photovoltaic energy projects showed increasing costs with the increase in power, and the normalized cost per kW followed an economy of scale, while the levelized cost of energy showed feasibility, except for the power of 22.1 kW. The sensitivity analyses showed profitability for the analyzed configurations.

ABSTRACT The present work aims to evaluate grain productivity, water productivity, and economic water productivity of three soybean cultivars under supplementary irrigation. Two experiments were conducted during the 2018 and 2019 harvests in Santa Maria/RS, Brazil. The experimental design consisted of a random bifactorial block design with six irrigation depths as the first factor and three soybean cultivars (Glycine max L.) as the second. The irrigation system used was the conventional fixed sprinkler, with a fixed irrigation shift of seven days. Crop productivity, water productivity, and economic water productivity were evaluated. The highest productivity was for 100% of reference evapotranspiration (ETo) in both harvests. Maximum technical efficiency was obtained for depths of 73.03% (Harvest 1) and 77.94% (Harvest 2) of ETo. Both harvests presented higher water productivity and economic water productivity in the 50% and 25% ETo depths respectively. Productivity is increased with irrigation, and the economic water productivity is maximized with reduction of depth.

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.

RESUMO O estudo visa quantificar os custos de produção das culturas de milho e sorgo em condições de sequeiro e irrigado para a geração de etanol, e avaliar a viabilidade econômica em diferentes cenários de preço de comercialização. Foram realizados dois experimentos nos anos de 2019/2020 e 2020/2021, em área experimental da Universidade Federal de Santa Maria, Santa Maria, RS. O delineamento experimental foi em faixas, com blocos ao acaso e quatro repetições. Foram avaliadas três lâminas de irrigação: 0, 50 e 100% da evapotranspiração de referência (ETo) como o primeiro fator, e duas cultivares de milho e uma de sorgo granífero como o segundo fator, sendo utilizados 45 cenários. O uso da irrigação plena (100% de ETo) reduz os custos de produção do litro de etanol em 15 e 17,89% e aumenta a produção de etanol em 44,18 e 48,25% para as culturas de milho e sorgo, respectivamente. Para o preço de mercado de R$ 2,00 L-1, o sorgo granífero não apresenta bom desempenho, com valor presente líquido (NPV) e taxa interna de retorno (IRR) negativos. O preço de venda de R$ 4,00 L-1 e irrigação plena é o melhor cenário econômico, com valores de NPV de R$ 90.356,93, IRR de 33,83%, relação benefício/custo (B/C) de 2,28, índice de rentabilidade (PI) de 3,99 e payback de três anos. O milho é economicamente viável para a produção de etanol em todos os cenários, sendo a irrigação plena e preço de comercialização de R$ 4,00 L-1, o que apresentou o melhor cenário econômico, com valores médios para o NPV de R$ 204.381,68, IRR de 63,35%, B/C de 2,96, IR 8,67 e payback de 1,58 anos, entre as cultivares.

ABSTRACT The study aims to quantify the production costs of maize and sorghum crops under rainfed and irrigated conditions for the generation of ethanol and to evaluate the economic feasibility in different scenarios of marketing price. Two experiments were carried out in the years 2019/2020 and 2020/2021, in an experimental area at the Federal University of Santa Maria, Santa Maria, RS, Brazil. The experiment was in strip plots, in a randomized block design and four replicates. Three irrigation depths, 0, 50 and 100% of the reference evapotranspiration (ETo), as first factor, and two maize cultivars and one grain sorghum cultivar as second factor, using 45 scenarios. The use of full irrigation (100% of ETo) reduces the production costs of the liter of ethanol by 15 and 17.89% and increases ethanol production by 44.18 and 48.25% for maize and grain sorghum crops, respectively. For the market price of R$ 2.00 L-1, the grain sorghum does not show good performance, with negative net present value (NPV) and internal rate of return (IRR). The sale price of R$ 4.00 L-1 and full irrigation is the best economic scenario, with values of NPV of R$ 90,356.93, IRR of 33.83%, benefit/cost ratio (B/C) of 2.28, profitability index (PI) of 3.99 and payback of three years. Maize is economically viable for ethanol production in all scenarios. Full irrigation and market price of R$ 4.00 L-1 represent the best economic scenario, with mean values for NPV of R$ 204,381.68, IRR of 63.35%, B/C of 2.96, PI of 8.67 and payback of 1.58 years, among the cultivars.

ABSTRACT Different water management strategies should be investigated to ensure adequate water supply to furrow-irrigated soybean plants in lowlands. This study examined the performance and efficiency of furrow irrigation techniques and related them to the soybean yield potential in lowland fields of Southern Brazil in the 2017/18 growing season. An experiment was conducted on raised seedbeds to evaluate furrow irrigation techniques: full irrigation with cutback, irrigation during the advance phase with low inflow, irrigation during the advance phase (cutoff), surge irrigation, and no irrigation. The design parameters, efficiency of the techniques, agronomic characteristics, and the grain yield of the soybean crop, were evaluated. The overall performance of the cutback technique in furrow irrigation was superior, followed by the surge irrigation, cutoff, and low inflow techniques. Furrow irrigation increased soybean yield in lowlands, and the cutback technique was the best to guarantee the soybean yield potential in lowlands, resulting in a 29% yield increase compared to non-irrigated.