# A Comparison of Energy Recovery by PATs against Direct Variable Speed Pumping in Water Distribution Networks

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

_{2}[4,5,6].

## 2. Methodology

#### 2.1. Study Area

#### 2.2. Direct and Indirect Pumping

#### 2.3. PAT and Microturbine Design/Operation

#### 2.4. Pressure Management and Energy Recovery

## 3. Experimental Investigation

#### Pump under Variable Speed

^{2}; $\rho $ the density of the water, about 1000 kg/m

^{3}; and $D$ the diameter of the pump. The efficiency of the whole pumping system, $\eta $, for each operating condition, can be calculated as:

^{3}. For the tested pump, with a $D$ = 170 mm impeller, at the maximum frequency $f$ = 50 Hz, the discharge, head, and efficiency at the BEP resulted in: ${Q}_{BEP}$ = 14 L/s, $\Delta {H}_{BEP}$ = 81.9 m, and ${\eta}_{BEP}$ = 0.63. If the methodology described in EN16480/2016 is applied, then a minimum efficiency index (MEI) equal to 0.6 can be assigned to the pump.

## 4. Application to the Case Study Network

#### 4.1. Indirect Pumping

^{3}/h; $C$ is a constant depending both on the minimum efficiency index (MEI) and the model of pump; and ${n}_{s}$ (min

^{−1}) is the specific speed whose expression is:

#### 4.2. Pressure Management

#### 4.3. Direct Pumping

## 5. Results

#### 5.1. Energy Indices under Differing Boundary Conditions

#### 5.2. Previously Reported Energy Indices for Different Boundary Conditions

## 6. Conclusions

## Author Contributions

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 6.**Dimensionless discharge ($q$) against dimensionless head ($h$) (

**a**), power ($p$) (

**b**) and efficiency ($\eta $) (

**c**)of pump HMU50-2/2.

**Figure 7.**Best-fit polynomial curve of frequency against best efficiency point ($f\mathrm{vs}{\eta}_{BEP}$).

**Figure 8.**Experimental measurements of $e$ against the dimensionless discharge e(q) and best-fit line.

**Figure 9.**Dimensionless discharge ($q$) against dimensionless head ($h$) (

**a**) and power ($p$) (

**b**) of PAT HMU50-2/2.

**Figure 10.**Time series of flow (

**a**) and head loss (

**b**) through the valve; pattern $\Delta H,Q\left(t\right)$ (

**c**).

**Figure 11.**Trend of efficiency indices for $\Delta {H}_{ind}$ = 25 m with ${i}_{2}$ equal to 25%, 50%, and 75%, respectively.

**Figure 12.**Trend of efficiency indices for $\Delta {H}_{ind}$ = 50 m (

**a**) and $\Delta {H}_{ind}$ = 100 m (

**b**), with ${i}_{2}$ equal to 25%, 50%, and 75%, respectively.

Scenario | Pumping Head (m) | Energy (kWh/Year) | Efficiency Index EI_{1} | Efficiency Index EI_{2} | Recovered Energy (kWh/Year) |
---|---|---|---|---|---|

Indirect | 48.14 | 32,420 | 0.24 | 0.31 | 2234 |

Direct | 34.88 | 22,327 | - |

$\mathbf{\Delta}{\mathit{H}}_{\mathit{i}\mathit{n}\mathit{d}}$ (m) | Energy Recovery | No Energy Recovery | ||
---|---|---|---|---|

Saving (%) | Direct Scenario Cutoff | Saving (%) | Direct Scenario Cutoff | |

25 | 5 | 0.94 $\Delta {H}_{ind}$ | 8 | 1.09 $\Delta {H}_{ind}$ |

50 | 2 | 0.98 $\Delta {H}_{ind}$ | 5 | 1.04 $\Delta {H}_{ind}$ |

100 | 0.5 | 0.99 $\Delta {H}_{ind}$ | 3 | 1.02 $\Delta {H}_{ind}$ |

**Table 3.**Main figures of the indirect and direct pumping scenarios: efficiency index of ideal system (${\eta}_{ai}$), efficiency index of real indirect pumping system with energy recovery (${\eta}_{ar,1.2}$) and otherwise (${\eta}_{ar,1.2}$), efficiency index of real direct pumping system (${\eta}_{ar,2}$).

Scenario | ${\mathit{\eta}}_{\mathit{a}\mathit{i}}$ | ${\mathit{\eta}}_{\mathit{a}\mathit{r}\mathbf{,}\mathbf{1.1}}$ | ${\mathit{\eta}}_{\mathit{a}\mathit{r}\mathbf{,}\mathbf{1.2}}$ | ${\mathit{\eta}}_{\mathit{a}\mathit{r}\mathbf{,}\mathbf{2}}$ |
---|---|---|---|---|

Indirect | 0.37 | 0.24 | 0.22 | - |

Direct | 0.46 | - | - | 0.30 |

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**MDPI and ACS Style**

Morani, M.C.; Carravetta, A.; Del Giudice, G.; McNabola, A.; Fecarotta, O.
A Comparison of Energy Recovery by PATs against Direct Variable Speed Pumping in Water Distribution Networks. *Fluids* **2018**, *3*, 41.
https://doi.org/10.3390/fluids3020041

**AMA Style**

Morani MC, Carravetta A, Del Giudice G, McNabola A, Fecarotta O.
A Comparison of Energy Recovery by PATs against Direct Variable Speed Pumping in Water Distribution Networks. *Fluids*. 2018; 3(2):41.
https://doi.org/10.3390/fluids3020041

**Chicago/Turabian Style**

Morani, Maria Cristina, Armando Carravetta, Giuseppe Del Giudice, Aonghus McNabola, and Oreste Fecarotta.
2018. "A Comparison of Energy Recovery by PATs against Direct Variable Speed Pumping in Water Distribution Networks" *Fluids* 3, no. 2: 41.
https://doi.org/10.3390/fluids3020041