• Energy Research

Abstract This paper presents a methodology aimed at assisting irrigation district managers in the optimal rehabilitation of pressurized irrigation networks. The methodology uses a multi-objective approach and finds optimal trade-off between investments and long term operational costs. The approach is based on two steps: 1—application of two alternative optimization algorithms to determine optimal trade-offs between installation costs and pump power absorption; 2—post-processing of the optimal solutions in terms of long term costs under various possible scenarios generated featuring various values of the useful construction life and of the capital recovery factor. Applications were carried out on a real case study, considering a pre-fixed electricity tariff and the on-demand operation of the network. After analyzing the results, the most cost-effective solution, with a redesign cost of 205,627 €; and overall cost varying from 6,019,447 €; to 11,498,053 €; according to the scenarios considered, was selected.

Water distribution networks (WDNs) are significant users of energy and contributors to greenhouse gas emissions. Energy recovery strategies (ERSs) have potential for switching WDNs to a renewable energy source, thereby assisting with the transition to net-zero emissions and reducing the dependency of water utilities on power-grids. To address the current lack of understanding of the potential for ERSs to achieve these goals, this work presents a holistic review, which considers all available devices, i.e. turbines, pumps as turbines, and other alternative strategies, such as the GreenValves, as well as all the kinds of application in the literature. Besides describing the latest most significant achievements in the context of ERSs, the review also identifies the most common issues and proposes several future research directions, including the need for a better test and comparison of the various available solutions in field applications, and more thorough analyses of the socio/political problems hampering their diffusion.

Abstract In recent years, pressurized pipe networks have improved the efficiency of irrigation systems while substantially increasing their energy demand. The progressive rise in energy costs makes it difficult to maintain the profitability of agricultural holdings. Moreover, global warming is a serious problem that threatens the environment worldwide and low CO2 emission processes should be promoted. To address these issues, it is necessary to look for sustainable and more profitable alternatives for the agricultural sector. One of these new alternatives is the use of renewable energies for pumping irrigation water at farm level, particularly photovoltaic energy. Nevertheless, the instability of irradiation hinders its management for stand-alone photovoltaic installations. In this work, a real-time model called the Smart Photovoltaic Irrigation Manager (SPIM) is developed to synchronize the photovoltaic power availability with the energy required to pump the irrigation requirements of different sectors of irrigation networks. SPIM consists of different modules to calculate the key management variables of the photovoltaic irrigation system: the daily irrigation requirements, the hydraulic behavior of the irrigation network, the instantaneous photovoltaic power production and the daily soil water balance. The lack of photovoltaic energy during daylight hours on any day of the irrigation season to supply the daily required amount of water is balanced with either the water stored in the soil or by extending the duration of the irrigation events in the following days when necessary. SPIM has been applied to simulate the management of photovoltaic irrigation in a real olive orchard in Southern Spain during the 2013 irrigation season. The results showed that the proper management of the photovoltaic irrigation system provided enough water to satisfy crop irrigation requirements throughout the irrigation season and avoided the emission of 1.2 tn CO2 eq using only the energy generated by solar panels.

Increasing of water use efficiency has been a key strategy for dealing with water scarcity in semiarid countries. In Spain modernization of irrigation schemes has consisted in the substitution of old open channels systems by pressurized networks. However, this improvement has represented a significant increase in water costs, mainly due to the higher energy requirements. Five irrigation districts of Andalusia, Southern Spain, have been analyzed using performance indicators, before and after the improvement actions. Results indicate an average reduction in water diverted for irrigation of 23%, but water costs increased in 52%. Consequently, farmers are migrating to more profit- able crops, such as citrus, with higher water requirements. Furthermore, managers’ predictions about the cropping patterns for the 2020s suggest that the area devoted to citrus production will increase by 12%, implying even higher potential maximum irrigation water demand. Hence, farmers will have to adapt to a future scenario by using deficit irrigation and other water saving technologies. Consequently, the vulner- ability of the irrigated agriculture to the typical droughts of the Mediterranean climate may increase.

AbstractWater distribution networks have to face the challenge of providing for a growing population with efficient management of water and energy. Pressure control in water networks is an efficien...

Pressure Reducing Valves (PRV) have been widely used as a device to control pressure at nodes in water distribution networks and thus reduce leakages. However, an energy dissipation takes place during PRV operation. Thus, micro-hydropower turbines and, more precisely, Pump As Turbines (PAT) could be used as both leakage control and energy generating devices, thus contributing to a more sustainable water supply network. Studies providing clear guidelines for the determination of the most cost-effective device (PRV or PAT) analysing a wide database and considering all the costs involved, the water saving and the eventual power generation, have not been carried out to date. A model to determine the most cost-effective device has been developed, taking into account the Net Present Value (NPV). The model has been applied to two case studies: A database with 156 PRVs sites located in the UK; and a rural water supply network in Ireland with three PRVs. The application of the model showed that although the investment cost associated to the PRV installation is lower in the majority of cases, the NPV over the lifespan of the PAT is higher than the NPV associated with the PRV operation. Furthermore, the ratio between the NPV and the water saved over the lifespan of the PAT/PRV also offered higher values (from 6% to 29%) for the PAT installation, making PATs a more cost-effective and more sustainable means of pressure control in water distribution networks. Finally, the development of less expensive turbines and/or PATs adapted to work under different flow-head conditions will tip the balance toward the installation of these devices even further.