Pumps as turbines for efficient energy recovery in water supply networks

Kramer, Matthias; Terheiden, Kristina; Wieprecht, Silke

doi:10.1016/j.renene.2018.01.053

Cited by 54 publications

(25 citation statements)

References 12 publications

(14 reference statements)

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“…experimental techniques to predict PAT performance from pump characteristics. Kramer et al concluded their study by saying that experimental investigations are still indispensable when an exact knowledge of turbine characteristics is required [28]. This issue is also addressed by Frosina et al [29] who proved by experimental verification that some methods (e.g., Childs' method) differ significantly from reality, while others (e.g., Stepanoff's method) show small relative differences.…”

Section: Volute Casing Nq = 25÷220mentioning

confidence: 99%

The Influence of Changing Hydropower Potential on Performance Parameters of Pumps in Turbine Mode

Polák

2019

Energies

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Pumps as turbines (PAT) are used as an alternative to water turbines in small hydropower plants. The same devices can also be used for energy recovery in water distribution networks. They can replace pressure reduction valves that often lead to energy loss. However, PATs lack the parts that regulate flow so that when a hydropower potential change occurs, efficiency is reduced, as is economic gain. This article summarizes the influence of changing hydropower potential on PAT efficiency and presents comparisons of experimental results with the commonly used predictive model stemming from the theory of physical similarity, which presumes constant PAT efficiency. Our research indicates that the deviation between the model and the real power output calculation at varying potentials was minimal. Similarly, the affine parabola can be used to determine the relationship between total head and flow rate. Other relationships differ from reality the more the PAT efficiency changes. The flow rate and total head dependence on shaft speed are the main factors when setting the optimum operational parameters at varying hydropower potentials. Therefore, a change in efficiency must be included in predictive calculations to correctly optimize PAT operation. The problem is that a change in efficiency cannot be reliably predicted in advance, especially in the case of small-scale devices. For this reason, further research on the issue of changes in PAT efficiency is necessary.

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Section: Volute Casing Nq = 25÷220mentioning

confidence: 99%

The Influence of Changing Hydropower Potential on Performance Parameters of Pumps in Turbine Mode

Polák

2019

Energies

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“…In order to evaluate more accurately the cost of such plants, data from 9 energy recovery schemes in water networks from different countries have been compiled [24,[55][56][57]. All of the selected plants adopted a PAT as a generating device, and had nominal powers ranging from 9 to 120 kW.…”

Section: Prv Total Installation Costsmentioning

confidence: 99%

A Model for Selecting the Most Cost-Effective Pressure Control Device for More Sustainable Water Supply Networks

García

Novara

Nabola

2019

Water

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Pressure Reducing Valves (PRV) have been widely used as a device to control pressure at nodes in water distribution networks and thus reduce leakages. However, an energy dissipation takes place during PRV operation. Thus, micro-hydropower turbines and, more precisely, Pump As Turbines (PAT) could be used as both leakage control and energy generating devices, thus contributing to a more sustainable water supply network. Studies providing clear guidelines for the determination of the most cost-effective device (PRV or PAT) analysing a wide database and considering all the costs involved, the water saving and the eventual power generation, have not been carried out to date. A model to determine the most cost-effective device has been developed, taking into account the Net Present Value (NPV). The model has been applied to two case studies: A database with 156 PRVs sites located in the UK; and a rural water supply network in Ireland with three PRVs. The application of the model showed that although the investment cost associated to the PRV installation is lower in the majority of cases, the NPV over the lifespan of the PAT is higher than the NPV associated with the PRV operation. Furthermore, the ratio between the NPV and the water saved over the lifespan of the PAT/PRV also offered higher values (from 6% to 29%) for the PAT installation, making PATs a more cost-effective and more sustainable means of pressure control in water distribution networks. Finally, the development of less expensive turbines and/or PATs adapted to work under different flow-head conditions will tip the balance toward the installation of these devices even further.

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“…The use of PaTs as energy-recovery units has mainly been applied in WDNs [25]. WDNs constitute typical case studies where the control of pressure inside network branches through PRVs is crucial, as previously reported [26][27][28][29][30]. De Marchis et al [31] developed a dynamic mathematical model for intermittent WDNs in the city of Palermo located in Sicily (Italy): they integrated PaTs in the model and demonstrated their effectiveness to recover energy that would otherwise be wasted.…”

Section: Introductionmentioning

confidence: 99%

Speed and Pressure Controls of Pumps-as-Turbines Installed in Branch of Water-Distribution Network Subjected to Highly Variable Flow Rates

et al. 2019

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The use of Pumps-as-Turbines (PaTs) to replace hydraulic turbines as energy-recovery units in industrial and civil applications is widening the penetration of hydropower in small-scale plants. PaTs show advantages in terms of installation costs and the availability of solutions. Water Distribution Networks (WDNs) represent a potential application where PaTs can be installed to recover water-pressure energy. In this work, a MATLAB©-Simulink model of a WDN branch located in South-Tyrol (Italy) was developed. The flow rate of the WDN was assessed though a measurement campaign showing high daily variability, which negatively affect PaT performance. To let the machine operate close to the Best Efficiency Point (BEP), four different operating strategies were studied to meet the constraint of a fixed pressure equal to 4 bar downstream the WDN branch, required to supply water to users. A PaT speed control strategy was implemented, granting better exploitation of flow rates even in the presence of high daily fluctuations. Energy recovery was 23% higher than that of the reference thanks to an advanced strategy based on controlling PaT rotational speed when the flow rate is smaller than that of the design, and operating in off-design conditions when flow rate is higher than that of the BEP.

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Pumps as turbines for efficient energy recovery in water supply networks

Cited by 54 publications

References 12 publications

The Influence of Changing Hydropower Potential on Performance Parameters of Pumps in Turbine Mode

The Influence of Changing Hydropower Potential on Performance Parameters of Pumps in Turbine Mode

A Model for Selecting the Most Cost-Effective Pressure Control Device for More Sustainable Water Supply Networks

Speed and Pressure Controls of Pumps-as-Turbines Installed in Branch of Water-Distribution Network Subjected to Highly Variable Flow Rates

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