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[Sustainable Energy Developments] Geothermal,Wind and Solar Energy Applications in Agriculture and Aquaculture || Chapter 7: Fundamentals of solar energy
摘要： Modern agricultural systems are characterized by the intensive and optimal use of land and water, turning agricultural exploitation into a semi-industrial concept. Greenhouses are systems suitable both for zones with unfavorable climatic conditions – allowing crop growth regardless of the ambient temperature – and for regions with less restrictive weather – with the aim of increasing crop productivity and improving fruit quality. In this context, a secure and environmentally friendly energy supply must be considered, for any power range or circumstance, including for stand-alone installations. Crop growth is primarily determined by climate and the amount of water and fertilizers applied through irrigation. Therefore, greenhouses are ideal for farming because they allow one to optimize these physical parameters, via the photosynthetic process (Ramírez-Arias et al., 2012), to enhance biomass production. This manipulation requires energy consumption, depending on the crop’s physiological requirements, and the production patterns adopted for yield quantity and timing. The present general concern on the development of more efficient and sustainable productive activities has increased interest in the evaluation of alternatives to the conventional energy sources in the sector; presently many are involved in processes for assessing the environmental feasibility and technological development of such alternatives (Antón et al., 2007; Bojacá et al., 2014; Martínez-Blanco et al., 2011; Page et al., 2012; Romero-Gámez et al., 2012; Torrellas et al., 2013; van der Werf et al., 2014). This work aims to provide an overview of the existing options for the integration of renewable sources in greenhouses located in semi-arid regions where, for example, the high availability of solar radiation facilitates its use for the fulfillment of a certain percentage of the heat and/or electricity loads of greenhouses. Accordingly, this overview contains the basic technological aspects of the main renewable technologies applicable in greenhouses, some simplified design tools and criteria for their selection. Finally, it includes a summary of selected experiences in this field. The main objective is to contribute to a better understanding of the technologies that should support the promotion and development of projects for the implementation of renewable energies in agriculture.
关键词： biomass,geothermal energy,wind energy,semi-arid climates,crop growth control,renewable energy,photovoltaic,greenhouses,energy efficiency,solar energy
更新于2025-09-04 15:30:14
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Lidar arc scan uncertainty reduction through scanning geometry optimization
摘要： Doppler lidars are frequently operated in a mode referred to as arc scans, wherein the lidar beam scans across a sector with a ?xed elevation angle and the resulting measurements are used to derive an estimate of the n minute horizontal mean wind velocity (speed and direction). Previous studies have shown that the uncertainty in the measured wind speed originates from turbulent wind ?uctuations and depends on the scan geometry (the arc span and the arc orientation). This paper is designed to provide guidance on optimal scan geometries for two key applications in the wind energy industry: wind turbine power performance analysis and annual energy production prediction. We present a quantitative analysis of the retrieved wind speed uncertainty derived using a theoretical model with the assumption of isotropic and frozen turbulence, and observations from three sites that are onshore with ?at terrain, onshore with complex terrain and offshore, respectively. The results from both the theoretical model and observations show that the uncertainty is scaled with the turbulence intensity such that the relative standard error on the 10 min mean wind speed is about 30 % of the turbulence intensity. The uncertainty in both retrieved wind speeds and derived wind energy production estimates can be reduced by aligning lidar beams with the dominant wind direction, increasing the arc span and lowering the number of beams per arc scan. Large arc spans should be used at sites with high turbulence intensity and/or large wind direction variation.
关键词： arc scans,wind energy,Doppler lidar,scan geometry optimization,turbulence intensity
更新于2025-09-04 15:30:14