METHODOLOGY FOR ENERGY EFFICIENCY IMPROVEMENT ANALYSIS IN PRESSURIZED IRRIGATION NETWORKS. PRACTICAL APPLICATION

Abstract

Analyses of possible synergies between energy recovery and water management are essential for achieving sustainable improvements in the performance of pressurized irrigation networks. Improving the energy efficiency of water systems by hydraulic energy recovery is becoming an inevitable trend for energy conservation, emissions reduction, and increases in profit margins. This Ph.D. research is focused on the proposal and development of an optimization methodology that improves energy efficiency in pressurized irrigation networks. To develop this methodology, the main objective of this Ph.D. thesis, the research is supported by secondary objectives. The first secondary objective overviews the state-of-the-art for different hydropower systems, paying attention to those systems in which residual energy can be considered for energy improvement. Furthermore, the need to analyze this energy improvement in pressurized irrigation networks is justified through enumerating the main advantages and disadvantages of these energy recoveries. This first objective establishes the contextualization stage of the thesis. The second part of this Ph.D. research, which develops the rest of the objectives, is called the procedural stage. This phase contains the analytical and experimental development of this research. The analytical phase develops the main steps of the optimization strategy. Each step comprises one methodology or method that is focused on the following objectives: ? To propose a methodology to determine the circulating flow over time in pressurized irrigation networks in any line depending on the agronomist intrinsic parameters of the established crops ? To develop a calibration strategy for the flow assignment in lines, which indicates the success of the proposed methodology ? To establish the energy balance as well as the involved energy terms to quantify the theoretical recoverable energy in pressurized water networks, particularly in irrigation networks ? To present a new methodology to maximize the recovered energy considering the actual feasibility to allocate pumps working as turbines (PATs) within pressurized water networks by using simulated annealing as a water management tool. The analytical phase is complemented with an intensive experimental campaign in two different PATs (radial and axial) in steady and unsteady flow conditions. The campaign regarding steady flow conditions enables the study of the efficiency variations in the machine as a function of the flow and rotational speed. The experimental analysis as well as the modification of the classical affinity laws allows one to determine the best efficiency line (BEL) and the best efficiency head (BEH) based on Suter parameters. Both lines enable modelers to establish the optimal rotational speed as a function of the flow during each instant to maximize the recovered energy. These new lines (BEL and BEH) should be incorporated within the optimization strategy, developing a procedure to recover energy as a function of the number of installed machines. Finally, to complement the developed analysis for the installation of the recovery systems in pressurized water systems, the unsteady flow in these facilities is also analyzed.