Caracterización multidimensional de alternativas energéticas en el bombeo de aguas subterráneas para la agricultura de regadío

Abstract

This doctoral dissertation has been presented in the form of thesis by publication. During the last decade, numerous international environmental agreements have been reached with the main objective of mitigating the climate change effects by promoting actions aimed to reduce CO2 emissions, and integrate renewable energy resource solutions in most sectors of society. Among these sectors, agriculture is susceptible to changing its energy model. From an international point of view, the agricultural sector, and more specifically such agriculture based on groundwater for irrigation, must achieve a set of energy, environmental and economic challenges for the future. Among them, the energy problem emerges as a relevant target, mainly due to the high fossil fuel dependence and its production cost influence. Others aspects, such as the relevant water resource dependence (very scarce in the Mediterranean area), as well as emissions should be also considered and solved. Nowadays, different organizations and administrations, such as the European Union (EU), are promoting a variety of energy model changes through agricultural process and facilities improvements. These solutions are mainly based on the integration of renewable energy systems, due to their potential energy independence benefits their positive environmental impact in terms of emissions. Focused on the groundwater pumping agriculture sector, PVWP (Photovoltaic Water Pumping) systems were proposed in the specific literature as a remarkable alternative to replace current diésel equipment. Nevertheless, most of the reviewed works only analyze their integration in remote rural areas of Africa or Asia, or small agricultural applications. Only a few of papers describe an extensive study (such as Kelley et al., in 2010). Therefore, there is a lack of contributions that address this integration and transition from a multidimensional point of view: economic, energy, environmental, social and hydric management. Moreover, some questions regarding efficiency, sizing or level of use of the energy capable of providing the required pumping power should be analyzed. This scenario thus represents the starting point of this thesis, underlying the developed contributions The proposed methodology of this thesis was based on the solar and water data gathered from two agricultural areas with an over-exploitation problem of the water resources: the aquifer in the region of La Mancha (Aquifer 23) in Spain; and the aquifer in the area of the Fès-Meknès plain (Saïss Aquifer) in Morocco. Subsequently, a statistical study of the resources was carried out and a Geographic Information System (GIS) was integrated into the study, in order to analyze geographically the distribution of resources and their applicability. With the aim of considering other alternatives and pumping system configurations, beyond such solutions commercially offered by the sector, a neural network-based architecture was designed to configure a map of potential alternatives, including: diesel equipment, PVWP isolated and connected to the grid, and systems supplied only by the power systems. These alternatives were then evaluated and characterized from a multidimensional point of view, taking into account different criteria within the economic, energy, environmental, and social fields. A 4D graphical environment was used to make more friendly and easier the characterization and comprehension of the results. Additionally, it was selected a multi-criteria decision-making process (MCDM) based on the classical AHP-TOPSIS methodologies to order the group of identified alternatives. Consequently, these alternatives were classified and prioritize according to their suitability, reliability, benefits and their adaptation to the conditions of each specific case study. This process entailed a preliminary inquiry of experts. From the results, this thesis provides a series of relevant contributions to the integration of renewable energy sources in the groundwater pumping agriculture sector. These contributions include: (i) the determination of the main impacts affecting the sector from a multi-focus analysis; (ii) the multidimensional characterization of energy alternatives aimed at pumping groundwater; (iii) a statistical and geographical analysis with the support of both exportable and scalable GIS methodology for the PVWP implementation and hydric resource management; and (iv) the application of an AHP-TOPSIS decision-making process (MCDM) to evaluate the suitability, reliability and benefits of the different alternatives to supply energy to the pumping systems. Finally, note the relevance of cooperative pumping systems supplied by PV installations connected to grid; mainly due to their potential economic benefits to the sector, their relevant use-of-energy and their high utilization of these renewable installations