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Energy harvesting from municipal water management systems: f

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Daniele Novara

on 2 February 2017

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Transcript of Energy harvesting from municipal water management systems: f

Energy harvesting from municipal water management systems: from storage and distribution to wastewater treatment
Master Thesis
Candidate: Daniele Novara
Supervisors: Prof. Ph.D. Helena Margarida Machado da Silva Ramos
Prof. Ph.D. Eng. Wojciech Stanek

29th December 2016
From IST:
Prof. Helena Ramos
Mariana Simão

Prof. Wojciech Stanek
Prof. Krzysztof Pikoń

Politechnika Śląska:

From business:
ATO 5 - Astigiano Monferrato

From water to energy
Water-Energy Nexus
Case-study 1
Case-study 2
Case-study 3
Conclusions and future work
World energy generation
Shares by fuel in electricity world production in 2014 (IEA)
Environmental concerns
Economic instabilities
Physical limit of resources
Security of supplies
A global issue
Fossil-based economy
Global warming
A part of solution:
Hydropower technologies
Long history
Non-intermittent, reliable
Competitive costs
Different technologies and sizes
Pumps as Turbines (PATs) - 1
Compact dimensions
Mass manufactured
Short delivery time
Low installation cost
Proven results
Low availability of characteristic curves in turbine mode given from producers
Rigid geometry, no flow rate regulation and low part-load efficiency
Typical performance curves of pumps and PATs (Chapallaz, 1992)
Drawing of a centrifugal PAT (www.worldpumps.com)
Pumps as Turbines (PATs) - 2
PAT performance prediction
2) Mathematical correlations
3) CFD analysis
1) Experimental test
Based on efficiency and/or specific speed.
Several authors: Stepanoff, Childs, Sharma, Alatorre-Frenk, Nautiyal, Grover...
Possibly a good compromise (accuracy vs. resources)
Needs validation from experimental data
Cumulative graph of electricity generation by source in Italy between 1887 and 2014 (TERNA, 2016)
Hydrostatic Pressure Wheel/Machine (HPW/HPM)
Experimental, compact waterwheel design for application in open channels with reduced head differences
Developed in 2007-2013 under EU's HYLOW project from universities of Southampton and Darmstadt
Water utilities: large energy consumers
Energy is required to extract, treat, store, monitor and distribute water
Growing energy demand, high costs
Scheme of an integrated water supply system (WSS) (waterconservationwasting.weebly.com)
Working scheme of HPM (Schneider, 2008)
Hydrostatic pressure distribution on a vertical surface immersed in fluid
Comparison between actual and calculated nondimensional parameters h and q for a selected PAT
Water and energy: highly correlated resources
Need for an integrated view and management of the two sectors
Average hourly water consumption from domestic users as percentage of daily demand relative to 12 cities across USA and Canada (Opitz et al., 1999)
Electricity demand load curve in Italy on 29/3/2016 (TERNA)
Energy recovery from Water Supply Systems (WSS) - 1
Lower investment cost respect to standard Hydropower
Reduction of costs faced by water utilities
Reduction of leakage rate
Basic scheme of WSS having pipe branches holng excess pressure
E.g. pressure control in water distribution networks
Case-study 1: Scurzolengo water tower (Italy) - 1
Height: 24 m
Capacity: 250 m3
Case-study 1: Scurzolengo water tower (Italy) - 2
View from control room (left) and picture of the water tower (right)
Measurements: inlet water pressure and flow sensors located at the basis of the tower
Variations of upstream pressure, inlet flow and tank level on 11.2.2016
Case-study 1: Scurzolengo water tower (Italy) - 3
1) Calculation of continuous and singular head losses
PAT selection chart (Chapallaz, 1992)
2) Net head determination
3) Choice of machinery
4) Sizing of machinery
(Cordier diagram)
N = 3000 rpm
D = (154±12) mm
Case-study 1: Scurzolengo water tower (Italy) - 4
5) Plant layout
Producible energy over a year
Case-study 1: Scurzolengo water tower (Italy) - 5
7) Economic analysis
Colebrook-White equation
6) Technical analysis
Payback between 1 and 2 years
LCOE of 0.025 €/kWh
8) Environmental analysis
9585 kWh/year
Avoided emissions each year:
3.13 ton CO2
28.76 g PM
2.97 kg NOx
41.7 GJ of primary energy saved per year
LCOE of generated electricity by source in 2013 (wikipedia)
Case-study 2: PRV substitution with PAT - 1
Possible system layouts
Characteristic curve and parameters of optimal PAT (no regulation)
Significant increase in producible energy when bypass is introduced
Besides, HR allows keeping a fixed downstream pressure
Performance gap due to limited data
Maximum attainable plant efficiency for evaluated scenarios
Scheme of PRV station and two possible design solutions (with or without regulation)
Case-study 2: PRV substitution with PAT - 2
System working points over a day
Case-study 2: PRV substitution with PAT - 3
Case-study 2: PRV substitution with PAT - 5
Overall plant efficiency vs. impeller diameter for PATs with different specific speed at N = 1520 rpm
No flow regulation
Top and side view of WWTP channel (all measures in mm)
Case-study 3: Asti WWTP - 1
Cumulative Discounted Cash Flow (CDCF) plotted versus project timeline under six analyzed scenarios
Water flow rate at WWTP outlet channel and depth at Venturi intake on 12/4/2016
Case-study 3: Asti WWTP - 2
Case-study 3: Asti WWTP - 3
Case-study 3: Asti WWTP - 4
Case-study 3: Asti WWTP - 5
Case-study 3: Asti WWTP - 6
80 cm bed drop at outlet WWTP channel
Fluid motion through the channel for a flow rate of 440 l/s
1) Net head determination
Average monthly flow rate in 2015
Lateral and axonometric views of the designed HPM
Axonometric views of the main channel with HPM unit installed and side by-pass
Main design constraint: channel size
Characteristic curve of the designed HPM
Energy Sankey diagram relative to Q = 288 l/s
2) Machinery choice and sizing
3) Technical analysis
4) Economic analysis
5) Environmental analysis
LCOE: 0.158 €/kWh.
More than six times the value of Case-Study 1
Avoided emissions each year:
1.3 ton CO2
11.94 g PM
1.23 kg NOx
17.3 GJ of primary energy saved per year
3980 kWh/year
Materials saved per year:
347 kg of coal
285 Nm3 of natural gas
Materials saved per year:
836 kg of coal
687 Nm3 of natural gas
General conclusions and future developments
Case-Study 1: Scurzolengo water tower
Case-Study 2: PRV substitution with PAT
Case-Study 3: Asti WWTP
Thank you!
installations within
Water Supply Systems
: significant contribution towards a less energy intensive, CO2-free, sustainable and reliable future water sector.

Key challenge:
development of innovative and efficient technologies for micro and pico-hydropower
, since little knowledge and expertise is currently available with respect to the great achievements made in the field of medium-to-big size hydropower converters.

Decision support tools
design guidelines
are needed in order to foster a widespread implementation of micro-hydropower schemes within WSS by
balancing different aspects
: amount of generated energy, economic and environmental benefits, reliability and system adaptability to future scenarios.
environmental and economic parameters
, with
payback period lower that two years
within all the analyzed scenarios.

Future work:
• acquisition of
additional data
about variation of pressure and flow profiles during summer months;
• obtain a more precise quotation of the
grid connection costs
• evaluation the installation of an
coupled with the PAT unit;
• study of a
sediment filter
upstream respect to the PAT;
• evaluation of a
multistage PAT
, which could possibly attain higher efficiencies respect to the considered solution.

The installation of PAT units as
pressure control device
within water networks proved to be a
technically feasible
and efficient solution. Schemes including
showed a
higher electricity yield
respect to mere PRV substitution with PAT, besides allowing network operators to set and maintain a constant
optimal backpressure

improving the available database
including characteristic curves of additional PATs;
• developing the analysis to include
economic parameters
• considering the coupling of an
to the designed PAT allowing for additional possibilities of flow regulation;
• performing the analysis based on an
increased number of pressure and available head samples

Despite the significant and guaranteed daily water flow passing through the examined WWTP outlet channel, the
extremely low available head
causes an hypothetical HPM installation to
perform low
in terms of generated electricity and economic attractiveness.
Future works:
• computational Fluid Dynamics (
) studies;
• improvements in the knowledge available on HPM converters inserted in a
real working environment
• verification that the operations of
Venturi Flume
would not be compromised by an HPM unit placed at downstream;
• reduction of the uncertainties in economic analysis;
• contemplate the possibility of
energy self-consumption
within the WWTP itself;
• evaluation of a
Gravitational Vortex

Characteristic curve and parameters of optimal PAT (Hydraulic Regulation)
Case-study 2: PRV substitution with PAT - 4
Overall plant efficiency vs. impeller diameter for PATs with different specific speed at N = 3020 rpm
Hydraulic regulation
Limited environmental impact (reservoirs)
From Large Hydro (P > 10 MW) to Small, Micro and Pico (P < 10 kW)
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