Energy efficiency assessment in collective irrigation systems using water and energy balances: methodology and application

Abstract

Many collective irrigation systems have been operating for decades, facing high degradation of existing infrastructures and huge water-energy efficiency problems. Predominantly composed of open canals, they have been partially or entirely converted into pressurised pipe systems, implying a considerable increase in energy consumption and operation and maintenance costs. Simple, easy-to-use, and comprehensive approaches for energy efficiency assessment in collective irrigation systems are needed for diagnosis and assisting decision-making on implementing adequate improvement measures. This research proposes and demonstrates an innovative approach based on the water and energy balances and performance indicators to assess the effect of water losses, network layout and operation, energy recovery, and equipment on energy efficiency. A novel methodology for energy balance calculation is proposed for open canal, pressurised and combined systems. The application to a real-life open canal system and network areas allowed the identification of efficiency problems mainly due to water losses in canals, followed by the dissipated energy in friction losses. Less critical are pumping and manoeuvring equipment inefficiencies. Also, a considerable excess of gravity energy is recovered in hydropower plants. In raising pipe systems, in which shaft input energy predominates and costs for pumping play a key role, surplus and dissipated energy in friction losses are the most relevant issues. Significant energy is lost in the water conveyance and distribution in both systems. Consequently, the potential to improve energy efficiency through water loss management, network layout, and operation improvement, besides pumping and manoeuvring equipment replacement, is considerable.