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Journal of Water Resources Planning and Management, 2021
In recent years, many researchers recognized pressure reducing valves (PRVs) as potential microhydropower sites, aiming to improve the efficiency of the water networks. Pump as Turbines (PATs) have been pointed out as the most suitable technology because of their favourable cost. Most of the methodologies available in the literature for selection of a PAT to replace a PRV follow a traditional approach that is based on scaling a prototype data using the affinity curves, thus restricting the solution space only to these curves. The optimization based methodology presented in this paper employs the classical hydraulic regulation scheme with the Nedler-Mead simplex direct search algorithm to search for the optimal solution within space that is constrained only by the boundaries of available centrifugal PATs on the market. The methodology also defines the PAT's operation limits based on the PAT's relative mechanical power. Improvements gained by using the novel methodology have been demonstrated on real-world case studies from Ireland and Italy that were previously used in the literature. The results of the considered sites also suggest that the maximal global plant's efficiency is around 80% of the maximal efficiency of the theoretically optimal PAT. The paper also examines effects of different objective functions and different PAT's operation limits on the selection of the optimal PAT.
Pump as Turbine (PAT) Design in Water Distribution Network by System Effectiveness
Water, 2013
Water distribution networks face several problems related to leakages, where the pressure control strategy is a common practice for water loss management. Small-scale hydropower schemes, where pumps as turbines replace pressure reducing valves, can be considered an interesting technical solution, which ensures both economic convenience and system flexibility. Due to the water networks' variable operating conditions, a new methodology to model the effectiveness of pumps as turbines was developed based on the efficiency and the mechanical reliability of the hydropower device and the flexibility of the plant. System effectiveness is proposed as the objective function in the optimization procedure and applied to a real system, enabling one to emphasize that the hydraulic regulation mode of the plant is better than the electric regulation mode for American Petroleum Industry (API) manufacturing standards of pumps.
Energies, 2016
Complex systems of water distribution networks (WDS) are used to supply water to users. WDSs are systems where a lot of distributed energy is available. Historically, this energy is artificially dissipated by pressure reduction valves (PRVs), thanks to which water utilities manage the pressure level in selected nodes of the network. The present study explores the use of economic hydraulic machines, pumps as turbines (PATs) to produce energy in a small network located in a town close to Palermo (Italy). The main idea is to avoid dissipation in favor of renewable energy production. The proposed study is applied to a WDN typical of the Mediterranean countries, where the users, to collect water during the period of water scarcity conditions, install private tanks. The presence of private tanks deeply modifies the network from its designed condition. In the proposed analysis, the economic benefit of PATs application in water distribution networks has been investigated, accounting for the presence of users' private tanks. The analysis, carried out by mean of a mathematical model able to dynamically simulate the water distribution network with PATs, shows the advantage of their installation in terms of renewable energy recovery, even though the energy production of PATs is strictly conditioned by their installation position.
Renewable Energy, 2020
Water Distribution Networks (WDNs) are becoming an attractive area of application for small hydropower, which can contribute to the development of distributed energy generation from renewable sources. Indeed, WDNs experience considerable water leakages due to their age and water management authorities often divide the WDNs by inserting Pressure Reducing Valves (PRVs), which waste a potentially recoverable hydraulic head. The replacement of PRVs with Pump as Turbines (PaTs) can be considered as an economically feasible solution to achieve both an effective pressure control and a throttling energy recovery. The selection, installation and control strategy of a PaT in a WDN must consider the variability of the pressure and the flow rate demand. Starting from the evaluation of the available head and the water demand, in this work, we describe a methodology to select from pump catalogues the most suitable PaT and the best control criteria for a specific WDN. Then, knowing the pump geometry, it is possible to predict the characteristic curve of the pump operating as a turbine by using a 1-D performance prediction model. The WDN of a town in the Apulia region (Southern Italy) has been used as a case study. Finally, a techno-economic evaluation has been carried out by considering both economic and environmental benefits.
Cost-Benefit Analysis for Hydropower Production in Water Distribution Networks by a Pump as Turbine
Journal of Water Resources Planning and Management, 2013
The use of micro hydroelectric plant in urban pipe networks, based on the combination of a 5 PAT (Pump as Turbine), two regulating valves and two pressure meters, is proposed along with 6 simple automation rules. Its economic benefit is tested on a small pipe network, where the net-7 work geometry, as well as the demand coefficient variation in time and space have been inferred 8 from previously collected data and existing analysis. A similar analysis has been also carried out 9 for different scenarios, where the reduction of pipe installation cost due to a diameter reduction is 10 compared with the increased benefit in energy production. The case study shows that a small in-11 crement of the pipe installation cost, with respect to the minimum required by the nodes minimum 12 pressure, can lead to a larger benefit for energy production.
Neural Computing and Applications, 2018
In these days, energy, water, fossil fuel restrictions and greenhouse gas emission have become the mutual problem of all countries. The application of hydro turbines, especially pumps as turbines in water distribution network, can be a great solution to these problems. In this research study, it is aimed to introduce a procedure for obtaining the optimum position of a pump as turbine in water distribution network. For this purpose, two objective functions are considered, namely power and up surge ratio. The reason of selecting the power is to maximize the energy production and minimize the payback period, and the reason of selecting the upsurge ratio is to minimize the initial costs and network risks. In the proposed methodology, a transient analysis database is being combined with optimization algorithms. In this research study, Bently hammer software has been used for generating the mentioned database. Ant colony optimization algorithm has been used for obtaining the discrete variable and three other heuristic algorithms, namely grey wolf optimizer, whale optimization algorithm and ion motion algorithm were used for finding the best continuous variable. Pipe number and the position of hydro turbine on the pipe were considered as the discrete and continuous variables, respectively. The proposed methodology was tested on a network in Palermo which data were available. The results indicated that the proposed methodology can suggest the best 6 pipes among 70 pipes of network and also the accurate position of the turbine on the pipe.
Optimal Selection of Pumps As Turbines in Water Distribution Networks
Proceedings
Pumps As Turbines (PATs) can be installed in Water Distribution Networks (WDNs) to couple pressure regulation and small-scale hydropower generation. The selection of PATs in WDNs needs proper knowledge about both the performances of machines available in the market and the operating conditions of the network. In this paper, a procedure for the preliminary selection of a PAT is proposed, based on the design of the main parameters (the head drop and the produced power at the Best Efficiency Point, the impeller diameter and the rotational speed) to both maximize the producible power and regulate the exceeding pressure.
Energy Production in Water Distribution Networks: A PAT Design Strategy
Water Resources Management, 2012
Pump operating as turbine (PAT) is an effective source of reducing the equipment cost in small hydropower plants. However, the manufacturers provide poor information on the PAT performance thus representing a limit for its wider diffusion. Additional implementation difficulties arise under variable operating conditions, characteristic of water distribution networks (WDNs). WDNs allow to obtain widespread and globally significant amount of produced energy by exploiting the head drop due to the network pressure control strategy for leak reductions. Thus a design procedure is proposed that couples a parallel hydraulic circuit with an overall plant efficiency criteria for the market pump selection within a WDN. The proposed design method allows to identify the performance curves of the PAT that maximizes the produced energy for an assigned flow and pressure-head distribution pattern. Finally, computational fluid dynamics (CFD) is shown as a suitable alternative for performance curve assessment covering the limited number of experimental data.
Optimal location of micro-turbines in water supply network
2015
Micro-hydropower is currently expanding as a solution to improve the efficiency of water systems by using energy excesses which are typically lost. In the particular case of water supply systems, often excessive pressure exists in zones of the network connected to other areas situated at higher altitudes. Pressure reducing valves are commonly used as a mean for dissipation of this excess energy. In this work, the installation of micro-turbines in a closed water supply network is analyzed as a way to recover the existing surplus of energy by converting it into electricity. The flow in water supply systems is highly variable, with a direct impact on the efficiency of the turbine and, as most water-supply networks are meshed, the optimal location of the energy converters is not straightforward and needs assessment by simulation processes. For this purpose, an optimization tool based on the application of an evolutionary algorithm was developed to select the best location, model and run...
Energy Production by Means of Pumps As Turbines in Water Distribution Networks
Energies
This paper deals with the estimation of the energy production by means of pumps used as turbines to exploit residual hydraulic energy, as in the case of available head and flow rate in water distribution networks. To this aim, four pumps with different characteristics are investigated to estimate the producible yearly electric energy. The performance curves of Pumps As Turbines (PATs), which relate head, power, and efficiency to the volume flow rate over the entire PAT operation range, were derived by using published experimental data. The four considered water distribution networks, for which experimental data taken during one year were available, are characterized by significantly different hydraulic features (average flow rate in the range 10-116 L/s; average pressure reduction in the range 12-53 m). Therefore, energy production accounts for actual flow rate and head variability over the year. The conversion efficiency is also estimated, for both the whole water distribution network and the PAT alone.