1,720,985 research outputs found
A COST BENEFIT ANALISYS FOR HYDROPOWER PRODUCTION IN WATER DISTRIBUTION NETWORKS BY PUMP AS TURBINE (PAT)
No full textThe use of micro hydroelectric plant in urban pipe networks, based on the combination of a PAT, two regulating valves and two pressure meters, is proposed along with simple automation rules. Its economic benefit is tested on a small pipe network, where the network geometry, as well as the demand coefficient variation in time and space have been inferred from previously collected data and existing analysis. A similar analysis has been also carried out for different scenarios, where the reduction of pipe installation cost due to a diameter reduction is compared with the increased benefit in energy production. The case study shows that a small increment of the pipe installation cost, with respect to the minimum required by the nodes minimum pressure, can lead to a larger benefit for energy production
Energy transfer from the freshwater to the wastewater network using a PAT-equipped turbopump
Full text linkA new strategy to increase the energy efficiency in a water network exists using turbo pumps, which are systems consisting of a pump and a turbine directly coupled on a same shaft. In a turbo pump, the pump is fed by a turbine that exploits a surplus head in a freshwater network in order to produce energy for one system (wastewater) and reduce the excess pressure in another (drinking water). A pump as turbine (PAT) may be preferred over a classic turbine here due to its lower cost. The result of such a coupling is a PAT-pump turbocharger (P&P). In this research, the theoretical performance of a P&P plant is employed using data from a real water distribution network to exploit the excess pressure of a freshwater stream and to feed a pump conveying wastewater toward a treatment plant. Therefore, the P&P plant is a mixed PAT-pump turbocharger, operating with both fresh and wastewater. A new method to perform a preliminary geometric selection of the machines constituting the P&P plant has been developed. Furthermore, the plant operation has been described by means of a new mathematical model under different boundary conditions. Moreover, the economic viability of the plant has been assessed by comparison with a conventional wastewater pumping system working in ON/OFF mode. Therefore, the net present value (NPV) of the investment has been evaluated in both situations for different time periods. According to the economical comparison, the PAT-pump turbocharger represents the most economically advantageous configuration, at least until the useful life of the plant. Such convenience amounts to 175% up to a time period equal to 20 years
Impact dynamics of mud flows against rigid walls
Full text linkMud flows represent one of the major causes of natural hazards in mountain regions. Similarly to
debris flows, they consist of a hyper-concentrated mixture of water and sediments flowing down a
slope and may cause serious damages to people and structures. The present paper investigates the
force produced by a dam-break wave of mud impacting against a rigid wall. A power-law shearthinning
model is used to describe the rheology of the hyper-concentrated mixture. A onedimensional
shallow water model is adopted and a second-order Finite Volume scheme is employed
to numerically solve the governing equations. The results indicate that depending on the fluid
rheological parameters and on the bottom slope, there exists a minimum value of the wall distance
above which the peak force does not exceed the asymptotic value of the hydrostatic final condition.
For two different values of the channel slope, the dimensionless value of this lower bound is
individuated for several values of the power-law exponent and of a dimensionless Basal Drag
coefficient. An estimation of the maximum peak force for wall distance smaller than the minimum
value is also provided
A new mixed integer non-linear programming model for optimal PAT and PRV location in water distributionnetworks
No full textWater distribution network are energy-demanding systems affected by low efficiency. In such systems, the pressure is generally kept under control by regulation valves to reduce the waste of water due to the leakages. The employment of energy production devices may be an efficient strategy to both reduce waste of water and produce energy, whose feasibility basically depends on the amount of recoverable energy, though. In this study, the optimal location of both pumps as turbines (PATs) and pressure-reducing valves (PRVs) within a literature water distribution network is investigated to maximize the production of energy and water savings. A new mixed integer non-linear model has been developed and a global optimization solver has been employed to perform the optimization. According to the results, the new optimization ensures good solutions, in term of water and energy savings, when compared with other procedures in literature
A new low-cost installation scheme of PATs for pico-hydropower to recover energy in residential areas
Full text linkA limiting factor in the use of hydropower plants in water supply networks consists in the cost of the electromechanical production device and the equipment necessary for the plant regulation. Pumps as Turbines (PATs) are electromechanical devices that have already been used in many mini and micro hydropower plants. Due to their low cost and reliability, PATs are an optimal solution for pico-hydropower plants, whose regulation has been widely analysed in literature, for power installations of only a few kW. A new power plant for small residential areas is presented herein. The new low-cost plant is provided with two PATs, that can work as single, series or parallel (SSP) turbines, and three on/off valves, whose synchronous operations regulate the flows and the head loss. The proposed design method is based on the maximization of the effectiveness of the system. Experimental data on a PAT are used to simulate the plant in several hydraulic conditions, with the application of the turbomachinery affinity law. The simple plant operations and the resulting interactions with the network confirm the viability of the proposed scheme. An economic assessment shows the feasibility of the new plant in different hydraulic situations
Potentialities of Complex Network Theory Tools for Urban Drainage Networks Analysis
Full text linkUrban drainage networks (UDNs) represent important infrastructures to protect and maintain community health and safety. For these reasons, technicians and researcher are focusing more and more on topics related to vulnerability, resilience and monitoring for controlling illicit intrusions, contaminant and pathogenic spread. In the last years the complex network theory (CNT) is attracting attention as a new, useful and structured approach to analyze urban systems. The aim of this work is to evaluate potentialities of CNT approaches for UDNs vulnerability assessment and monitoring system planning. Limits and potentialities of applicability of CNT tools to UDNs are first provided evaluating the performances of standard centrality metrics. Then, it is proposed the use of tailored metrics embedding prior information, as intrinsic relevance of each node and pipe flow direction, which derive from the Horton's hierarchy and geometric data (pipe slope), respectively, without performing hydraulic simulations. The analysis is applied on two schematic literature networks of different complexity and to a real case-study. The results suggest that vulnerability/resilience, monitoring design, contaminant and pathogenic spreads can be effectively analyzed using tailored metrics. Therefore, the proposed approach represents a complementary tool respect the more complex and computationally expensive methodologies and it is particular useful for large complex networks
Potential Energy, Economic, and Environmental Impacts of Hydro Power Pressure Reduction on the Water-Energy-Food Nexus
No full textThe installation of hydropower pressure reduction (HPPR) technology in water supply networks (WSN) has recently been encouraged to limit water losses through leakage. Traditionally, pressure reducing valves (PRVs) were positioned at strategic nodes in a water network and were operated continuously to dissipate excess energy and minimize pipe failure. The alternative adoption of low-cost and highly reliable HPPR technology - Pump As Turbine (PAT) - can recover energy to improve the sustainable management of water networks and increase the energy, economic, and environmental benefits derived from the provision of water resources. To encourage the exploitation of HPPR, indicators and metrics were developed and applied for a case study (olive crop production with an irrigation network in Andalusia, Spain). The case study incorporated (1) a number of WSN scenarios based on water supply conditions, location of the HPPR within the network, and pipe age; (2) the expected performance of the PAT in the market; and (3) the expected optimal performance of an HPPR design based on a variable operation strategy (VOS). Independent life cycle indicators and nexus metrics were created to enhance the evaluation of the performance of HPPR technology as part of the water-energy-food nexus. In this case study, the new metrics expressed the impact of HPPR technology on the water-energy food nexus in terms of climate change and in the context of olive production in an irrigation network. The methodology for assessing combined energy, economic, and environmental metrics (3EM) can be used to account for the value of HPPR deployment in any WSN. These metrics can inform local decision makers and national policy makers, by providing relative and/or absolute evidence on the environmental impacts of HPPR technology in the water sector
A performance prediction model for pumps as turbines (PATs)
Full text linkIn recent years, the interest towards the use of pumps operating as turbines (PATs) for the generation of electrical energy has increased, due to the low cost of implementation and maintenance. The main issue that inhibits a wider use of PATs is the lack of corresponding characteristic curves, because manufacturers usually provide only the pump-mode performance characteristics. In the PAT selection phase, the lack of turbine-mode characteristic curves forces users to expend expensive and time-consuming efforts in laboratory testing. In the technical literature, numerous methods are available for the prediction of PAT turbine-mode performance based on the pump-mode characteristics, but these models are usually calibrated making use of few devices. To overcome this limit, a performance database called Redawn is presented and the data collected are used to calibrate novel PAT performance models
A New Low-Cost Technology Based on Pump as Turbines for Energy Recovery in Peripheral Water Networks Branches
Full text linkThe recovery of excess energy in water supply networks has been a topic of paramount
importance in recent literature. In pressurized systems, a pump used in inverse mode (Pump As
Turbine, PAT) demonstrated to be a very economical and reliable solution, compared to traditional
energy production devices (EPDs). Due to the large variability of flow rate and head drop within
water distribution networks, the operation of PATs could be performed by a series-parallel regulation
system based on an electronic or a hydraulic principle. Despite the low cost of the PATs and of
regulation and control systems, a great barrier to the diffusion of a small hydro power plant in water
distribution is represented by the necessity of additional civil works to host the whole plant. Based
on laboratory and numerical experiments, the present paper proposes a new low-cost technology,
overcoming most of the limitations of the present technologies when low energy is available and
high discharge variation occurs. The operating conditions of the plant are properly optimized with
reference to the working conditions of a case study. Despite the laboratory prototype having exhibited
a significantly low efficiency (i.e., 16%), due to the use of small centrifugal pumps suitable for the
analyzed case study, in larger power plants relying on more efficient semi-axial submersed pumps,
the energy conversion ratio can increase up to 40%. The results of this research could be useful for
network managers and technicians interested in increasing the energy efficiency of the network and
in recovering energy in the peripheral branches of the network were a large variability of small flow
rates are present
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