Search Results (105)

Flood control infrastructure is essential for the development of cities and the population’s well-being. The goal is to protect human and economic resources by reducing the inundation area and controlling the flood level and peak discharges. Detention basins can do this by storing a large volume of water to be released after the peak discharge. By doing this, a large amount of energy is stored, which can be recovered via micro-hydropower. In addition, as the release flow is controlled and almost constant, Pumps as Turbines (PAT) could be a feasible and economic option in these cases. Thus, this study investigates the feasibility of micro-hydropower (MHP) in urban detention basins, using the Santa Lúcia detention basin in Belo Horizonte as a case study. The methodology involved hydrological modeling, hydraulic analysis, and economic and environmental assessment. The results demonstrated that PAT selection has a crucial role in the feasibility of the MHP, and exploiting rainfall with lower intensities but higher frequencies is more attractive. Using multiple PATs with different operating points also showed promising results in improving energy production. In addition to the economic benefits, the MHP in the detention basin produces minimal environmental impact and, as it exploits a wasted energy source, it also reduces the carbon footprint in the urban water cycle. Full article

The modernisation of irrigation networks has enhanced water use efficiency but increased energy demand and costs in agriculture. Energy recovery (ER) is possible by utilising excess pressure to generate electricity with pumps as turbines (PATs), offering a cost-effective alternative to traditional turbines. This study assesses the use of PATs in pressurised irrigation networks for recovering wasted hydraulic energy, employing the particle swarm optimisation (PSO) algorithm for PAT sizing based on two single-objective functions. The analysis focuses on minimising the payback period (MPP) and maximising energy recovery (MER) at specific excess pressure points (EPPs). A comparative analysis of values for each EPP and objective function is conducted independently in Sector II of the Canal del Zújar Irrigation District (CZID) in Extremadura, Spain. A sensitivity analysis on energy prices and installation costs is also performed to assess socioeconomic trends and volatility, examining their effects on both objective functions. The optimisation process predicts an annual ER for an average irrigation season using 2015 data ranging from 9554.86 kWh to 43,992.15 kWh per PATs from the MER function, and payback periods (PPs) from 12.92 years to 3.01 years for the MPP function. The sensitivity analysis replicated the optimisation for the years 2022 and 2023, showing potential annual ER of up to 54,963.21 kWh and PPs ranging from 0.88 to 5.96 years for the year 2022. Full article

This research provides a comprehensive review of hybrid energy solutions and optimization models for ports and marine environments. It details new methodologies, including strategic energy management and a machine learning (ML) tool for predicting energy surplus and deficits. The hybrid energy module solution for the Port of Avilés was further developed to evaluate the performance of new tools such as the Energy Management Tool (EMTv1), HYbrid for Renewable Energy Solutions (HY4RES), and a commercial model (Hybrid Optimization of Multiple Energy Resources—HOMER) in optimizing renewable energy and storage management. Seven scenarios were analyzed, integrating different energy sources and storage solutions. Using EMTv1, Scenario 1 showed high surplus energy, while Scenario 2 demonstrated grid independence with Pump-as-Turbine (PAT) storage. The HY4RES model was used to analyze Scenario 3, which achieved a positive grid balance, exporting more than imported, and Scenario 4 revealed limitations of the PAT system due to the low power installed. Scenario 5 introduced a 15 kWh battery, efficiently storing and discharging energy, reducing grid reliance, and fully covering energy needs. Using HOMER modeling, Scenario 6 required 546 kWh of grid energy but sold 2385 kWh back. Scenario 7 produced 3450 kWh/year, covering demand, resulting in 1834 kWh of surplus energy and a small capacity shortage (1.41 kWh/year). AI-based ML analysis was applied to five scenarios (the ones with access to numerical results), accurately predicting energy balances and optimizing grid interactions. A neural network time series (NNTS) model trained on average year data achieved high accuracy (R²: 0.9253–0.9695). The ANN model proved effective in making rapid energy balance predictions, reducing the need for complex simulations. A second case analyzed an increase of 80% in demand, confirming the model’s reliability, with Scenario 3 having the highest MSE (0.0166 kWh), Scenario 2 the lowest R² (0.9289), and Scenario 5 the highest R² (0.9693) during the validation process. This study highlights AI-driven forecasting as a valuable tool for ports to optimize energy management, minimize grid dependency, and enhance their efficiency. Full article

This research aims to present relevant developments carried out in the domains of energy recovery and the associated digital technology in the water sector. These include the implementation of digital twins of a PRV and energy converters. Several performance tests have been carried out in pumps operating as turbines (PATs) when replacing pressure-reducing valves (PRVs) or coupled to them. Based on virtual prototype of turbines, the numerical modelling of a PRV and tested PATs, with radial and axial impellers, have been developed. On the other hand, Digital Twins (DTs) provide useful data collection/analysis tools for reproducing disruption scenarios for resilience assessment purposes and analyzing asset prognosis and the system efficiency to determine proactive management models. Full article

The paper deals with the issue of determining the optimal setting of input variables in Ansys CFX for modeling pump flow in turbine operation (PAT). The pump model was created in Autodesk Inventor. The mesh for numerical simulations was created using Ansys Fluent Meshing, considering the mesh quality parameters’ skewness and aspect ratio. The Ansys CFX computational model was experimentally verified on an actual pump by measuring the performance parameters on a test circuit and using the PIV (particle image velocimetry) method. The research indicated that the most suitable setting for the model input variables was the inlet pressure and PAT flow rate combination. Another option was to adjust the pressure at the pump inlet and outlet. However, the calculation time in this case was up to 30% longer. The comparison of the model results with the experiment showed that the deviations in the numerical model performance values did not exceed 10% of the values measured on the test circuit. Only the calculated torque was 1.2 ± 0.13 Nm higher on average than the torque measured on the test circuit. This difference is most likely due to the simplification of the geometry of the computational mesh in order to reduce the computation time. Full article

Pressure control by means of pressure-reducing valves (PRVs) is a possible strategy to reduce water losses in water distribution networks (WDNs). However, PRV replacement with energy-harvesting devices—such as pumps as turbines (PATs)—can lead to a more sustainable management of water systems. This study analyzes the case study of a WDN located in Northern Italy, of which the layout is supposed to be upgraded by installing a PAT for both pressure reduction and energy recovery. To identify the optimal PAT to install (i.e., the one that maximizes energy recovery), a fleet of forty-five turbomachines is hypothetically employed. The study reveals that the hydraulic regulation of the optimal PAT allows recovering over 50% of the hydraulic energy available in the WDN. Full article

ALLIEVI is a software developed by the Universitat Politècnica de València to model and analyze hydraulic transients in pressurized water systems. ALLIEVI allows for the modeling of valve and pump maneuvers, including pressure reducing valves (VRPs) and energy recovery elements such as turbines and pumps operating as turbines (PATs). In this work, two practical cases are presented in which ALLIEVI is used as a tool, either to adjust the energy recovery potential of a system or to calculate the hydraulic transient generated by maneuvers of an energy recovery system. Full article

Pump-as-turbines (PAT) has been widely used during the last decade as one of the most interesting technologies in the field of energy recovery. Many studies and papers have been published in which the performance of the pumps in the turbine operating regime were analysed. Since horizontal single stage centrifugal norm pumps are most commonly used as PATs, their performances are analysed in this paper. Most of the research was related to individual pump aggregates or smaller groups and to obtaining their performance curves in turbine random mode. In this work, extensive experimental, numerical, and theoretical investigations were conducted to obtain complete dimensionless performance characteristics of single stage centrifugal norm pumps operating as turbines. One of the goals was to form a simple analytical expression that will, for this type of aggregate, map the pump operating characteristic to the appropriate turbine operating regime. By using the expressions obtained and presented in the paperwork, engineers are enabled to make the appropriate choice of pump aggregate for operation in turbine random mode for potential locations. For this purpose, the procedure for choosing the appropriate PAT aggregate or parallel operation of aggregates and the analysis of their operation on the existing system are presented in the paper. This innovative procedure allows us to select quickly PAT aggregates for a potential location and carry out appropriate techno-economic analyses and analyses of possible energy savings. Full article

The use of pumps as turbines has been gaining more and more attention in recent years. The present work mainly investigates the influence of blade wrap angle on the internal flow and pressure fluctuation characteristics of centrifugal pumps as turbines. Five different wrap angles (35°,45°, 55°, 65°, and 75°) for a forward-curved impeller were numerically analyzed under multiple operating conditions. The accuracy of numerical simulation was validated by experimental results. The results show that maximum efficiency is achieved with a blade wrap angle of 35°, and the highest efficiency flow point gradually decreases as the blade wrap angle increases. It is found by conducting entropy production theory analysis that the high-entropy production rate regions in PATs are concentrated in the volute tongue and impeller blade inlet regions, and that the entropy production rate at the impeller inlet region increases and then decreases as the blade wrap angle decreases. In addition, pressure pulsation was affected not only by dynamic and static interference but also by an irregular vortex around the impeller; its magnitude under Q_t is higher than 0.8Q_t for blade wrap angles of 55° and 75°. The primary frequency of pressure pulsation within the impeller is the axial frequency fn and its multiples, and the frequency with the largest amplitude is 3fn. The periodicity of vortices is closely related to the periodicity of pressure pulsation. And it is suggested that a PAT with a 35° blade wrap angle is advantageous for improving the stability of a turbine. Full article

Pumps-as-Turbines (PATs) are increasingly used in micro-hydropower applications due to their cost competitiveness that is brought about by lower acquisition, design, operation, and maintenance costs. Despite these, limited research exists that investigates PAT failures. Notably, there is a literature gap concerning cavitation in PATs. As such, this study proposes an improvement to the deviation from the normal distribution (DND) technique to facilitate application in PAT cavitation detection. Probability density functions of vibration signals collected during operation at design speed and various cavitation states are developed and the DND computed using two approaches, i.e., the use of baseline data and the original method, for comparison purposes. Normal probability plots are presented to depict suitability of the two approaches in quantifying the DND. Results show higher deviation when using baseline data, hence, improved detection capabilities with amplification of the slope of the trend line under cavitating conditions when using the proposed DND approach. The proposed method also allows for establishing clear alarm limits for the condition monitoring of PATs in practice. Moreover, the proposed method is validated by application at various PAT operating speeds and cavitation states. The proposed method is found to be responsive, reliable, and independent from operating speed. Full article

Due to the existence of an inlet elbow, transmission shaft, and other structural components, the inflow of axial-flow pumps as turbines (PATs) becomes non-uniform, resulting in the complexity of internal flow and adverse effects such as structural vibration. In this paper, numerical methods were employed to explore the non-uniform inflow effects on impeller forces and internal flow field characteristics within an axial-flow PAT. The study results indicated that non-uniform inflow caused uneven pressure distribution inside the impeller, which leads to an imbalance in radial forces and offsetting the center of radial forces. With an increasing flow rate, the asymmetry of radial forces as well as the amplitude of their fluctuations increased. Non-uniform inflow was found to induce unstable flow structures inside the impeller, leading to low-frequency, high-amplitude pressure fluctuations near the hub. Using the enstrophy transport equation, it was shown that the relative vortex generation term played a major part in the spatiotemporal evolution of vortices, with minimal viscous effects. Full article

Using pumps operating as turbines (PATs) offers the possibility of increasing the sustainability of water and energy systems by recovering the excess energy that would be otherwise lost in pressure-reducing valves or head loss chambers. Regarding on-grid applications, there have been many research works, and PATs have been implemented in several ways. However, more research still needs to be done on optimizing the efficiency and stability of PATs operating in off-grid systems. This work contributes to the development of stable direct current (DC) off-grid electric systems based on PATs using a self-excited induction generator (SEIG). In this context, a methodology is proposed, based on the hydraulic, mechanical, and electric subsystems, to define the PAT-SEIG operational area to maximize energy conversion and system efficiency. These limits depend highly on the capacitor value, rotational speed, and electric load. In addition, an analytical model is proposed to estimate the PAT-SEIG operation under specific conditions. With this, water managers can design and optimize an off-grid PAT-SEIG system and define the best hydraulic machines, electronic equipment, and control elements to maximize energy conversion within the target of operational limits. Two micro PAT-SEIG setups were implemented in the hydraulic laboratory of IST/CERIS under typical operating conditions to validate the proposed methodology. The system’s maximum efficiency and operational limits can be adapted using different capacitor values for the excitation of the SEIG. Considering the nominal efficiencies of the system’s components, the maximum p.u. efficiency obtained for each PAT-SEIG system was between 0.7 and 0.8 p.u. Full article

The world’s water infrastructures suffer from inefficiencies, such as high energy consumption and water losses due to inadequate management practices and feeble pressure regulation, leading to frequent water and energy losses. This strains vital water and energy resources, especially in the face of the worsening challenges of climate change and population growth. A novel method is presented that integrates micro-hydropower plants, with pumps as turbines (PATs), in the water network in the city of Funchal. Sensitivity analyses evaluated the microgrid’s response to variations in the cost of energy components, showing favorable outcomes with positive net present value (NPV). PV solar and micro-wind turbines installed exclusively at the selected PRV sites within the Funchal hydro grid generate a combined 153 and 55 MWh/year, respectively, supplementing the 406 MWh/year generated by PATs. It should be noted that PATs consistently have the lowest cost of electricity (LCOE), confirming their economic viability and efficiency across different scenarios, even after accounting for reductions in alternative energy sources and grid infrastructure costs. Full article

In order to reduce the impact of production changes on the performances of pumps as turbines (PATs) in the process industry, it is imperative to lessen head variations at different mass flow rates. This study established a relationship equation between theoretical head and geometric parameters for multistage PATs. The influence of these parameters on the flatness of the head-flow (H-Q) curve was determined through derivation methods. The original PAT was a two-stage pump, and 12 PAT models were designed by modifying the geometric parameters of the positive guide vanes. Fluent software was employed for numerical simulations. The study found that numerical calculations aligned well with theoretical derivations for the flat H-Q curve. Considering the geometric variations in the positive guide vane, increasing the outlet placement angle, blade number, and throat area or decreasing the base circle diameter was able to flatten the H-Q curve effectively; at the best efficiency point, the throat area had the most significant impact on a slope, followed by the outlet placement angle, blade number, and base circle diameter, respectively. The individual contributions to reducing the slope were 0.53, 0.24, 0.1, and 0.09. In terms of the best efficiency point (BEP) of PATs, increasing the throat area appropriately was able to improve the BEP of the PAT by around 1.65% and shifted its BEP towards higher flow rates. However, in other cases, the BEPs all decreased. Increasing the outlet placement angle of the positive guide vane by 3° led to the BEP being reduced by 0.79%. When the number of positive guide vane blades was increased from 8 to 10, the BEP decreased by 1.24%. When the diameter of the base circle of the positive guide vane was decreased, the BEP of the turbine decreased by 0.06%. This study provides theoretical support and can serve as a reference for the design of multistage hydraulic turbines with flatter H-Q curves. Full article

A pump as turbine (PAT) can be a cost-effective and versatile solution to recover energy in several fields of application. However, its optimal exploitation requires a reliable and general methodology for selecting the optimal turbomachine. To this purpose, this paper presents and validates a comprehensive methodology that identifies the best turbomachine (i.e., the one that maximizes the recovered energy) by considering two hydraulic sites and forty-five PATs. In both sites, the methodology correctly identifies the best PAT, which allows for the recovery of up to 45% of the available hydraulic energy. To further investigate PAT potential, an additional layout of installation, which comprises two PATs installed in parallel, is also considered. The operation of both PATs is optimally scheduled to maximize energy recovery. As a result, the energy recovered by the best pair of PATs is almost 50% of the available hydraulic energy. An in-depth analysis about PAT operation (i.e., operating range, causes of wasted energy, timeframe of operation and PAT efficiency) reveals that the installation of two PATs is actually recommended in just one of the two considered sites. Full article