# Inline Pumped Storage Hydropower towards Smart and Flexible Energy Recovery in Water Networks

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Electromechanical Equipment

#### 2.1. Pump Characteristics

#### 2.1.1. Characteristic Curves and Operational Point

#### 2.1.2. Selection of a Pump

- Pump 1 is not appropriate since it would operate with flow rates not recommended by the manufacturer;
- Pump 2 has a flow rate near to the average daily demand, increasing its probability of becoming obsolete if the demand is intensified or if the flow is reduced due to a pipe roughness increase over time. The maximum efficiency is also inferior to the pump 3 and, if equipped with a VSD, the possible speed range is minor given its inferior heads.

#### 2.2. Pump as Turbine Curves

_{s}was not known, the values of head number (${\psi}_{\mathrm{int}}$) and efficiency (${\eta}_{\mathrm{int}}$) for each discharge number value (${\phi}_{\mathrm{int}}$) were estimated by linear interpolation. When the non-dimensional number was defined, for each diameter and rotational speed ($N$) the head and efficiency curves were determined by Equations (4)–(6):

## 3. Methodology

#### 3.1. Base Pumping System (BPS) and Experimental Results

#### 3.1.1. System Configuration

^{3}existed at downstream of the operating system. A valve located at downstream made it possible to induce flow variations by maneuvering and applying local head loss of the valve. An electromagnetic flowmeter (SC-1) and two pressure transducers (SP-1 and SP-2) were used to record the flow rate and pressure data, respectively. Different tests were carried out for different conditions depending on the different opening percentages of the VR-2 valve and also the pump rotational speeds, as presented in Table 2. The data measurements included the flow rate ($Q$), head ($H$), rotational speed ($N$), pump upstream and downstream pressures, the efficiency of the pump ($\eta $) and hydraulic and mechanic powers ${P}_{h}$ and ${P}_{M}$, respectively).

#### 3.1.2. Experimental Results

#### 3.2. Model Calibration

#### 3.3. Pumping System Operation

#### 3.4. Inline Pumped-Storage Hydropower (IPSH)

^{3}. The by-pass line was equipped with a throttle control valve (TCV) working in an open or closed position to include or isolate the by-pass line. The T-2 was located at a lower elevation to generate a gravity flow from T-1 to T-2. The new IPSH system was considered as a loop system to use the previously assessed characteristics attained in the experimental loop system. It is worth mentioning that the idea is not limited to loop systems but can be adapted to a real system with direct flow condition. In a direct flow system, based on the available head at T-1 and downstream demand, the by-pass line can be activated to use the available head difference for energy generation. Hence, a turbine was considered in the by-pass line to generate energy from the gravity flow. Since WaterGEMS does not include a built-in turbine element, the general purpose valve (GPV) was used for this purpose by defining the flow-head loss curve correspondent to the turbine characteristic curves.

## 4. Dimensional Analysis and Discussion

_{T}= Q

_{P}the length scales of 20 and 50 were considered. Additionally, for geometrically similar impellers operating at the same specific speed, the affinity laws are as follows:

## 5. Conclusions

- Characteristic curves of turbomachines in pump and turbine mode were defined for the best selection which conducts the best energy solution, avoiding eventual induced operating instabilities.
- An inline pumped-storage hydropower (IPSH) solution was defined and adapted from a base pumping system (BPS) in some existing water infrastructures of small to large scales, while not requiring significant changes and investments based on a by-pass and a lower tank upstream the pumping station.
- The energy generation using the gravitational flow appears to be an economic advantage in the definition of the energy recovery solution, as demonstrated through the achieved power.
- Depending on the type of demand (i.e., a constant flow between tanks or a variable demand pattern with water level compensation), the application shows a smart pressure and flow control in an energy recovery solution, replacing classical flow control valves.
- Based on similarity laws for the hydraulic system and the turbomachinery between pumps and turbines, a scaling-up approach for larger hydro energy converters was developed showing promising results.
- The smart approach based on a controlled recovery energy solution, which would be dissipated and the increasing of the system flexibility by a new bottom tank allowing two types of flow conditions (i.e., pump and turbine modes), can significantly improve the energy efficiency in the water sector, allowing us to better face the associated existent energy costs (e.g., pumping, treatment plants, water leakage, expansion and reparation of infrastructures and water bill for costumers).

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Nomenclature

Symbols | |

D | turbomachinery diameter [m] |

H | head [m] |

L | length [m] |

${n}_{}$ | rotational speed [rpm] |

${n}_{sp}$ | specific speed of the pump |

${n}_{sT}$ | specific speed of the turbine |

P | power [kW] |

Q | flow rate [L/min] or [m^{3}/s] |

t | time [s] |

V | flow velocity [m/s] |

Indices | |

h | hydraulic |

int | interpolated value |

mod | model |

M | mechanical |

pro | prototype |

R | rated or best efficiency point |

T | related to turbine |

Greek letters | |

$\gamma $ | specific weight [N/m^{3}] |

$\eta $ | efficiency |

$\psi $ | head number |

$\phi $ | flow rate number |

Abbreviations | |

BPS | base pumping system |

IPSH | inline pumped-storage hydropower |

MHP | micro-hydropower |

PAT | pump as turbine |

WDN | water distribution network |

WSS | water supply system |

## References

- UN General Assembly. Transforming Our World: The 2030 Agenda for Sustainable Development. 21 October 2015. A/RES/70/1. Available online: refworld.org/docid/57b6e3e44.html (accessed on 14 February 2020).
- IEA (International Energy Agency). Renewables: Market Analysis and Forecast from 2019 to 2024, Paris. 2019. Available online: iea.org/reports/renewables-2019 (accessed on 13 February 2020).
- Ramos, J.S.; Ramos, H.M. Solar powered pumps to supply water for rural or isolated zones: A case study. Energy Sustain. Dev.
**2009**, 13, 151–158. [Google Scholar] [CrossRef] - Ramos, J.S.; Ramos, H.M. Sustainable application of renewable sources in water pumping systems: Optimised energy system configuration. Energy Policy
**2009**, 37, 633–643. [Google Scholar] [CrossRef] - Hoes, O.A.C.; Meijer, L.J.J.; Van der Ent, R.J.; Van de Giesen, N.C. Systematic high-resolution assessment of global hydropower potential. PLoS ONE
**2017**, 12. [Google Scholar] [CrossRef] - Dadfar, A.; Besharat, M.; Ramos, H.M. Storage ponds application for flood control, hydropower generation and water supply. Int. Rev. Civ. Eng.
**2019**, 10. [Google Scholar] [CrossRef] - Kougias, I.; Aggidis, G.; Avellan, F.; Deniz, S.; Lundin, U.; Moro, A.; Muntean, S.; Novara, D.; Pérez-Díaz, J.I.; Quaranta, E.; et al. Analysis of emerging technologies in the hydropower sector. Renew. Sustain. Energy Rev.
**2019**, 113. [Google Scholar] [CrossRef] - Besharat, M.; Dadfar, A.; Viseu, M.T.; Brunone, B.; Ramos, H.M. Transient-flow induced compressed air energy storage (TI-CAES) system towards new energy concept. Water
**2020**, 12, 601. [Google Scholar] [CrossRef] [Green Version] - Ramos, H.M.; Zilhao, M.; López-Jiménez, P.A.; Pérez-Sánchez, M. Sustainable water-energy nexus in the optimization of the BBC golf-course using renewable energies. Urban Water J.
**2019**, 16, 215–224. [Google Scholar] [CrossRef] - Samora, I.; Hasmatuchi, V.; Münch-Allign, C.; Franca, M.J.; Schleiss, A.J.; Ramos, H.M. Experimental characterization of a five blade tubular propeller turbine for pipe inline installation. Renew. Energy
**2016**, 95, 36–366. [Google Scholar] [CrossRef] - Carravetta, A.; Fecarotta, O.; Ramos, H.M.; Mello, M.; Rodriguez-Diaz, J.A.; Morillo, J.G.; Kemi Adeyeye, K.; Coughlan, P.; Gallagher, J.; McNabola, A. Reducing the Energy Dependency of Water Networks in Irrigation, Public Drinking Water, and Process Industry: REDAWN Project. Proceedings
**2018**, 2, 681. [Google Scholar] [CrossRef] [Green Version] - Samora, I.; Manso, P.; Franca, M.J.; Schleiss, A.J.; Ramos, H.M. Energy Recovery Using Micro-Hydropower Technology in Water Supply Systems: The Case Study of the City of Fribourg. Water
**2016**, 8, 344. [Google Scholar] [CrossRef] [Green Version] - Fecarotta, O.; Aricò, C.; Carravetta, A.; Martino, R.; Ramos, H.M. Hydropower Potential in Water Distribution Networks: Pressure Control by PATs. Water Resour. Manag.
**2014**, 29, 699–714. [Google Scholar] [CrossRef] - Gallagher, J.; Harris, I.M.; Packwood, A.J.; McNabola, A.; Williams, A.P. Strategic assessment of energy recovery sites in the water industry for UK and Ireland: Setting technical and economic constraints through spatial mapping. Renew. Energy
**2015**, 81, 808–815. [Google Scholar] [CrossRef] - Qian, Z.; Wang, F.; Guo, Z.; Lu, J. Performance evaluation of an axial-flow pump with adjustable guide vanes in turbine mode. Renew. Energy
**2016**, 99, 1146–1152. [Google Scholar] [CrossRef] - Carravetta, A.; Derakhshan Houreh, S.; Ramos, H.M. Pumps as Turbines; Springer Tracts in Mechanical Engineering; Springer: Cham, Switzerland, 2018. [Google Scholar]
- Vieira, F.; Helena, M.; Ramos, H.M. Optimization of operational planning for wind/hydro hybrid water supply systems. Renew. Energy
**2009**, 34, 928–936. [Google Scholar] [CrossRef] - Pérez-Sánchez, M.; Sánchez-Romero, F.J.; Ramos, H.M.; López-Jiménez, P.A. Energy Recovery in Existing Water Networks: Towards Greater Sustainability. Water
**2017**, 9, 97. [Google Scholar] [CrossRef] [Green Version] - Fontana, N.; Giugni, M.; Glielmo, L.; Marini, G.; Raffaele, Z. Use of hydraulically operated PRVs for pressure regulation and power generation in water distribution networks. J. Water Resour. Plann. Manag.
**2020**, 146. [Google Scholar] [CrossRef] - Postacchini, M.; Darvini, G.; Finizio, F.; Pelagalli, L.; Soldini, L.; Di Giuseppe, E. Hydropower Generation Through Pump as Turbine: Experimental Study and Potential Application to Small-Scale WDN. Water
**2020**, 12, 958. [Google Scholar] [CrossRef] [Green Version] - Carravetta, A.; Del Giudice, G.; Fecarotta, O.; Ramos, H.M. PAT Design Strategy for Energy Recovery in Water Distribution Networks by Electrical Regulation. Energies
**2013**, 6, 411–424. [Google Scholar] [CrossRef] [Green Version] - Fontana, N.; Giugni, M.; Glielmo, L.; Marini, G.; Verrilli, F. Real time control of a PRV in water distribution networks for pressure regulation: Theoretical framework and laboratory experiments. J. Water Resour. Plann. Manag.
**2018**, 144. [Google Scholar] [CrossRef] - Creaco, E.; Campisano, A.; Fontana, N.; Marini, G.; Page, P.R.; Walski, T. Real time control of water distribution networks: A state-of-the-art review. Water Res.
**2019**, 161. [Google Scholar] [CrossRef] - Puleo, V.; Fontanazza, C.M.; Notaro, V.; De Marchis, M.; Freni, G.; La Loggia, G. Pumps as turbines (PATs) in water distribution networks affected by intermittent service. J. Hydroinform.
**2013**. [Google Scholar] [CrossRef] [Green Version] - Alberizzi, J.C.; Renzi, M.; Righetti, M.; Pisaturo, G.R.; Rossi, M. Speed and Pressure Controls of Pumps-as-Turbines Installed in Branch of Water-Distribution Network Subjected to Highly Variable Flow Rates. Energies
**2019**, 12, 4738. [Google Scholar] [CrossRef] [Green Version] - Chacón, M.C.; Rodríguez Díaz, J.A.; Morillo, J.G.; McNabola, A. Hydropower energy recovery in irrigation networks: Validation of a methodology for flow prediction and pump as turbine selection. Renew. Energy
**2020**, 147, 1728–1738. [Google Scholar] [CrossRef] - Pérez-Sánchez, M.; Sánchez-Romero, F.J.; López-Jiménez, P.A.; Ramos, H.M. PATs selection towards sustainability in irrigation networks: Simulated annealing as a water management tool. Renew. Energy
**2018**, 116, 234–249. [Google Scholar] [CrossRef] - Morillo, J.G.; McNabola, A.; Camacho, E.; Montesinos, P.; Rodríguez Díaz, J.A. Hydro-power energy recovery in pressurized irrigation networks: A case study of an Irrigation District in the South of Spain. Agric. Water Manag.
**2018**, 204, 17–27. [Google Scholar] [CrossRef] - Pérez-Sánchez, M.; Sánchez-Romero, F.J.; Ramos, H.M.; López-Jiménez, P.A. Modeling Irrigation Networks for the Quantification of Potential Energy Recovering: A Case Study. Water
**2016**, 8, 234. [Google Scholar] [CrossRef] [Green Version] - Pérez-Sánchez, M.; Sánchez-Romero, A.J.; Ramos, H.M.; López-Jiménez, P.A. Optimization Strategy for Improving the Energy Efficiency of Irrigation Systems by Micro Hydropower: Practical Application. Water
**2017**, 9, 799. [Google Scholar] [CrossRef] [Green Version] - Besharat, M.; Tarinejad, R.; Aalami, M.T.; Ramos, H.M. Study of a compressed air vessel for controlling the pressure surge in water networks: CFD and experimental analysis. Water Resour. Manag.
**2016**, 30, 2687–2702. [Google Scholar] [CrossRef] - Pottie, D.L.F.; Ferreira, R.A.M.; Maia, T.A.C.; Porto, M.P. An alternative sequence of operation for Pumped-Hydro Compressed Air Energy Storage (PH-CAES) systems. Energy
**2019**. [Google Scholar] [CrossRef] - Odukomaiya, A.; Abu-Heiba, A.; Graham, S.; Momen, A.M. Experimental and analytical evaluation of a hydro-pneumatic compressed-air Ground-Level Integrated Diverse Energy Storage (GLIDES) system. Appl. Energy
**2018**, 221, 75–85. [Google Scholar] [CrossRef] [Green Version] - Ramos, H.; Borga, A. Pumps as turbines: An unconventional solution to energy production. Urban Water
**1999**, 1, 261–263. [Google Scholar] [CrossRef] - Ramos, H.; Borga, A. Pumps yielding power. Dam Eng. Water Power Dam Constr.
**2000**, 10, 197–217. [Google Scholar] - Fontanella, S.; Fecarotta, O.; Molino, B.; Cozzolino, L.; Della Morte, R. A Performance Prediction Model for Pumps as Turbines (PATs). Water
**2020**, 12, 1175. [Google Scholar] [CrossRef] [Green Version] - Chaker, M.A.; Triki, A. Investigating the branching redesign strategy for surge control in pressurized steel piping systems. Int. J. Pres. Ves. Pip.
**2020**, 180, 104044. [Google Scholar] [CrossRef] - Kapelan, Z. Calibration of Water Distribution System Hydraulic Models. Ph.D. Thesis, University of Exeter, Exeter, UK, 2010. [Google Scholar]
- Wylie, E.; Streeter, V.; Suo, L.F. Fluid Transient in Systems; Prentice-Hall: Englewood, NJ, USA, 1993. [Google Scholar]
- Ramos, H.M. Simulação e Controlo de Transitórios Hidráulicos em Pequenos Aproveitamentos Hidroelétricos. Ph.D. Thesis, Civil Engineering, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal, 1995. (In Portuguese). [Google Scholar]

**Figure 4.**Pump operation zone in the third quadrant and characteristic parameters [34].

**Figure 5.**Pump as turbine (PAT) characteristic curves for different specific speed values, based on experimental tests and affinity laws (adapted from [25]): (

**a**) efficiency curves; (

**b**) head curves.

**Figure 8.**Scheme of the base pumping system (BPS) in the mathematical model and experimental apparatus.

**Figure 9.**Comparison of experimental and numerical results for the BPS; (

**a**) head and flow rate; (

**b**) root mean square error (RMSE).

**Figure 12.**Scheme and visualization of the experimental set-up of the inline pumped-storage hydro (IPSH) solution.

Parameters | Measuring Range |
---|---|

Pump head [m] | 1.8 to 16.92 |

Flowmeter Rate [L/min] | 0 to 61.98 |

Rotational speed of the pump [rpm] | 1600 to 2950 |

Opening valve VR2 [%] | 0 to 100 |

Variable Parameters | Tested Values |
---|---|

VR-2 closure percentage [%] | 4.16, 6.25, 8.33, 10.41, 12.5, 16.66, 25, 33.33, 50, 66.60, 83.33, 100 |

Pump rotational speed, N [rpm] | 1600, 1800, 2000, 2200, 2400, 2600, 2800, 2950 |

Parameter | Value |
---|---|

Flow rate [L/min] | 35 |

Head [m] | 13.5 |

Efficiency [%] | 75 |

Rotational speed [rpm] | 2950 |

Specific speed (Equation (2)) | 10.05 |

**Table 4.**Scale-up parameters for a hydraulic system and turbomachine affinity characteristic parameters with ${n}_{sT}$ (in m, m

^{3}/s) = 8.8.

Parameter Unit | Hydraulic System | Turbine Impeller | Turbine Affinity Laws | |||
---|---|---|---|---|---|---|

Q | V | D | N_{T} | H_{T} | P_{T} | |

[m^{3}/s] | [m/s] | [mm] | [rpm] | [m] | [kW] | |

Model | 0.60 × 10^{−3} | 0.99 | 25 | 2170 | 10.64 | 0.052 |

1/20 | 1.04 | 4.42 | 500 | 470 | 200 | 1532 |

1/50 | 10.31 | 6.99 | 1250 | 298 | 503 | 41,657 |

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**MDPI and ACS Style**

Ramos, H.M.; Dadfar, A.; Besharat, M.; Adeyeye, K.
Inline Pumped Storage Hydropower towards Smart and Flexible Energy Recovery in Water Networks. *Water* **2020**, *12*, 2224.
https://doi.org/10.3390/w12082224

**AMA Style**

Ramos HM, Dadfar A, Besharat M, Adeyeye K.
Inline Pumped Storage Hydropower towards Smart and Flexible Energy Recovery in Water Networks. *Water*. 2020; 12(8):2224.
https://doi.org/10.3390/w12082224

**Chicago/Turabian Style**

Ramos, Helena M., Avin Dadfar, Mohsen Besharat, and Kemi Adeyeye.
2020. "Inline Pumped Storage Hydropower towards Smart and Flexible Energy Recovery in Water Networks" *Water* 12, no. 8: 2224.
https://doi.org/10.3390/w12082224