Hydro-power energy recovery in pressurized irrigation networks: A case study of an Irrigation District in the South of Spain

In pressurized irrigation networks, energy reaches around 40% of the total water costs. Pump-as-Turbines (PATs) are a cost-effective technology for energy recovery, although they can present low efficiencies when operating outside of the best efficiency point (BEP). Flow fluctuations are very important in on-demand irrigation networks. This makes flow prediction and the selection of the optimal PAT more complex. In this research, an advanced statistical methodology was developed, which predicts the monthly flow fluctuations and the duration of each flow value. This was used to estimate the monthly time for which a PAT would work under BEP conditions and the time for which it would work with lower efficiencies. In addition, the optimal PAT power for each Excess Pressure Point (EPP) studied was determined following the strategy of minimising the PAT investment payback period (PP). The methodology was tested in Sector VII of the right bank of the Bembézar River (BMD), in Southern Spain. Five potential sites for PAT installation were found. The results showed a potential energy recovery of 93.9 MWh and an annual energy index per irrigated surface area of 0.10 MWh year −1 ha −1 . Renewable energy will become increasingly important in the agriculture sector, to reduce both water costs and the contribution to climate change. PATs represent an attractive technology that can help achieve such goals.2 of 20 points of excess pressure. Water networks are commonly sub-optimal in terms of their use of energy and water resources, due to changes in elevation, demand, water pressure and leakage rates across many kilometres of pipelines. Recent research has studied the application of MHP turbines in water supply and wastewater infrastructure to reduce pressure to desired levels and recover energy in the form of electricity [11][12][13][14]. In pressurized irrigation networks, the irrigation devices (drippers, sprinklers) continue to evolve towards greater efficiency in the consumption of water and energy. This results in a lower working pressure requirement in some areas of an irrigation network, triggering the potential for available energy recovery. In addition, due to changes in elevation and demand across a typical irrigation network, areas of excess pressure are unavoidable, unless a network is situated in an area with uniform gradient and demand distribution.The use of pump-as-turbines (PATs) for energy recovery have been shown to be cost-effectivepotentially just 10% of the cost of conventional MHP turbines [15][16][17][18][19] at sites with small power output capacity [20,21]. Nonetheless, PATs have the disadvantage of relatively low efficiency, which can reduce further with large flow fluctuations. It has been shown that the efficiency of the PAT can reduce to approximately 70% of the maximum efficiency when the flow is 20% below the Best Efficiency Point (BEP) flow rate [21]. Different investigations have also analysed the use of PATs in irrigation networks for energy recovery. Nonetheless, the flow fluctuations in the i...

Section: Discussionmentioning

confidence: 96%

Section: Economic Viabilitymentioning

confidence: 99%

mentioning

confidence: 99%

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Pump-as-Turbine Selection Methodology for Energy Recovery in Irrigation Networks: Minimising the Payback Period

Chacón

Díaz

Morillo

et al. 2019

“…Besides rural and urban water networks, irrigation water networks also have provided great potential in energy recovery, where a substantial amount of energy used for water distribution can be recovered [19]. The energy harvesting in irrigation water networks is relatively a new area, with very challenging concerns because of the flow variation.…”

Section: Introductionmentioning

confidence: 99%

Transient-Flow Induced Compressed Air Energy Storage (TI-CAES) System towards New Energy Concept

Besharat

Dadfar

Viseu

et al. 2020

In recent years, interest has increased in new renewable energy solutions for climate change mitigation and increasing the efficiency and sustainability of water systems. Hydropower still has the biggest share due to its compatibility, reliability and flexibility. This study presents one such technology recently examined at Instituto Superior Técnico based on a transient-flow induced compressed air energy storage (TI-CAES) system, which takes advantage of a compressed air vessel (CAV). The CAV can produce extra required pressure head, by compressing air, to be used for either hydropower generation using a water turbine in a gravity system or to be exploited in a pumping system. The results show a controlled behaviour of the system in storing the pressure surge as compressed air inside a vessel. Considerable power values are achieved as well, while the input work is practically neglected. Higher power values are attained for bigger air volumes. The TI-CAES offers an efficient and flexible solution that can be exploited in exiting water systems without putting the system at risk. The induced transients in the compressed air allow a constant outflow discharge characteristic, making the energy storage available in the CAV to be used as a pump storage hydropower solution.

“…However, these methods are mainly suitable for SHP integration in common water systems (e.g., aqueducts for civil and industrial uses), whose hydraulic schemes and functioning can be different from collective irrigation systems [9,12]. Most of these works have focused on urban water supply networks and not on the irrigation sector, which usually has higher fluctuations in water demand, as well as different seasonal and daily demand patterns [21]. As regards the energy recovery in irrigation networks, Pérez-Sánchez et al [12] have proposed a methodology to estimate the energy dissipated by friction losses, the energy required for irrigation, and the recoverable energy based on the variation of flow following the random demand of the users and the real irrigation allocations.…”

Section: Introductionmentioning

confidence: 99%

Equivalent Small Hydro Power: A Simple Method to Evaluate Energy Production by Small Turbines in Collective Irrigation Systems

Nicotra

Zema

D’Agostino

et al. 2018

The exploitation of water flows in collective irrigation networks is promising in view of enhancing renewable energy production in agriculture. To this goal, a simplified method to estimate the electricity production of small hydro power (SHP) plants integrated in existing irrigation systems is proposed. This method schematizes the water network by an “equivalent” system, consisting of a single pipeline with homogeneous diameter and material. The proposed method only requires as input data the altimetry and the maps of the irrigated areas instead of the materials and diameters of all the conduits of a common water network (often unknown by irrigation managers). The feasibility of the proposed method has been verified to size SHP plants in seven collective irrigation systems of Calabria (Southern Italy). This application has highlighted a mean error of 20% in estimating the SHP power with a more detailed model, previously developed by the same authors and verified in the same context; these estimates are more accurate for SHP plants not exceeding 150–175 kW of electrical power. These results suggest the applicability of the proposed method for feasibility studies or large-scale projects of small SHP plants.