auditing for energy efficiency in water supply and ... · energy optimization in waterworks slide 7...

Auditing for Energy Efficiency in Water Supply and

Wastewater utilities – Concepts and Applications

Energy saving processes using the example of HAMBURG WASSER, Germany

- Water supply: Waterworks -

Energy optimization in waterworks

Efficiency = Results achieved vs. resources

used (according to ISO 9000)

Options:

Minimize input (resources used)

Maximize output (results achieved)

Both is best!

Energy Optimization: produce constant/more

water with constant/less energetic input

Higher Efficiency = higher energetic

productivity

Process optimization is energy optimization!

Introduction – energy efficiency


Overview

Energy saving measures in water supply – Waterworks

Energy consumers in waterworks

Energy optimization by process optimization

Wells, abstraction and treatment

Pumping

Examples from Hamburg Wasser

Energy generation

Staff qualification and motivation

Measurability and data

Success control (Performance indicators)



Introduction

Specific energy consumption in Germany: ~ 0.51

kWh/m³ drinking water

Germany: 2,400 Mio. kWh electric power (2007)

Pumps are the main energy consumers in

drinking water production (waterworks), esp. in

water abstraction and distribution

Aims:

Increase of sustainable energy efficiency,

i.e. Relation between obtained benefits and

used energy

Reduction of CO2- Emissions



Distribution of energy between different sectors of waterworks

Energy for extraction of raw water

Energy for pumping clear water

Energy for water treatment and buildings

Extraction of raw water

(groundwater)

Pumping clear water

Water treatment and buildings

Example:

HAMBURG

WASSER




Deterioration of yield of a well:

Well ageing, deposits on filter tubes of wells and

adjoining filter sand - well performance may

decrease – more energy consumption, corrosion

Groundwater as raw water source needs pumping

energy

Bad pump steering, hydraulic overuse, pumps without

frequency converters, high specific energy

consumption

Pumps may get blocked by ochre formation/ferric

incrustation

General hydraulic situation of well field not clear Extraction of raw water

(groundwater)



Water treatment and buildings of treatment plant

Treatment process needs energy (little)

Aeration and degassing with compressors, blowers, fans: energy

demanding process

Pumping in treatment is little at HAMBURG WASSER

Since pumps are big energy consumers – little energy consumption in

treatment compared to abstraction and distribution of water

Filter backwashing needs 5-10% of filtered water – energy use because

of treated water becoming wastewater

Energy consuming disposal of

backwash water

Heating of building




Pumping clear water

Pumps pump water directly into the system at HAMBURG WASSER –

no water towers

Pressure in the system: 5-6 bars

Flow needs to be adapted to costumer water consumption – water

must stay < 24 hours in the system

Pumps are working at all times (esp. during daytime)

Frequency converters are necessary in pumps

Pumping clear water



Background at

HAMBURG WASSER

Decrease in water

consumption in Hamburg

Changed operation - less

water is treated and

pumped into network

Result : throttling with gate,

shift of operating point,

incrustation ...) – needs a

lot of energy

Deterioration of yield from

wells

Decrease in water consumption

Water consumption in L/(person*day) in Germany


Key factors for technical implementation of energy

optimization

Operational optimization

Efficient energy use

Correct design of system

components (e.g. Pump, electric

motor etc.)

Correct design of related systems

(e.g. pipe network, treatment process, transformers etc.)

Correct operation

(e.g. pump operation, usage of reservoirs, water

rationing etc.)


Process Cycle for energy optimization

Data collection

Preparation energy

balance Energetic evaluation

Determination of

areas with

investigation needs

Implementation of

measures

Assessment of

potentials for energy

minimization

Feedback/

Control

Process optimization


Process optimization - water abstraction

Extraction of raw water from groundwater

Supervision of every groundwater well (hours used per

day, flow, raw water quality, inside observation by

camera if problems)

Well head management

Do not abstract too high flows

Sustainable groundwater abstraction (prevent ferric

incrustation/iron hydroxide deposition in well)

Saves energy (groundwater level does not sink that

much) less conveyor height needed in pumping

Long term well rehabilitation – use wells as long as

possible; building new wells is energy consuming Extraction of raw water

(groundwater)


Process optimization - water abstraction

Extraction of raw water from groundwater II

Maintenance of pumps to prevent blocking by ferric

incrustation

When planning new wells: modeling of the

groundwater situation before well construction

Find best groundwater abstraction situation

(energy efficient)

Do not build well in vain if e.g. problem of

salination

Groundwater has often better quality than surface

water – in water treatment this safes energy,

chemicals, wastewater (with chemicals) in contrast to

treatment of surface water


(groundwater)


Process optimization - pumping

Optimization during extraction

Energy efficient well pumps

Modeling of the hydraulic situation

Effects of well ageing

Optimized pump steering

Equipment of regulating pumps with

frequency converters

Significant reduction of the specific energy

consumption



kWHQ

Pges

Aufn

*367

**

Performance curve and submersible pump

Submersible pumps

Principle of flow rate / conveyor

heights (Centrifugal pump)

Pump specific

characteristic diagram

Interpretation of optimal

operating point

Power input



][2*

.

22

mHzzg

vv

g

ppH vea

eaeaA

Operating point of submersible pump

System curve

Pump curve

System curve

Raw water abstraction system

The system curve determines the needed

head of the pump:

Operating point of the pump is the

intersection of pump curve and system

curve (Basis for pump operation planning)

Change of pump curve by changed

rotational speed (frequency converter)

Change of system curve by flow losses

(gate throttling)

Characteristic curve consists of:

Dynamic losses of the pipe

network, static heights and

losses of the valves



*) = increased head

Pump curve

NEW system curve

Minimization

Raw water abstraction system

Negative effects of throttling

Reduced flow rate at increasing

heads due to turbulences (heat,

sound)

Resulting in changed operating

point → reduced capacity of the

submersible pump → energy

losses

→“inefficient operation“



[m³/h*m]s

QQspez

Specific yield

Iron hydroxide deposition in

well tube

Corrosion in well tube

Measures to maintain original yield of extraction wells

Determination of specific yield of a well

Reason for deterioration:

Hydraulic overuse

Mineral/organic deposits in wells or

filter material (iron hydroxide

deposition, mucilage, sand)

Corrosion

→ Changed operating point due to

increased conveyor heights with sinking

water level



Measures to maintain original yield

Well regeneration

Basic principle: removal of deposits from

filter tubes and adjoining filter sand,

discharge of detached deposits and control

of the regeneration progress via suspended

solid analysis

Initiate appropriate recovery action

immediately when well performance

decreases by 10 to 20% (DVGW W 130)

Regeneration can be performed only when

the well is generally suitable for regeneration

measures (construction, material,

performance, stability)


Process optimization - water treatment

Surface Water

Less energy used in abstraction / more energy and more chemicals

used in treatment

Elimination of turbidity, anorganic matter, organic matter such

as plant matter, algae, bacteria (health risk)

If particles too small → flocculation before filtration needed

More wastewater due to chemical products (energy for disposal)



Groundwater

More energy used in abstraction / less energy used in treatment

since water quality usually better than surface water

Oxidation of iron and manganese (Fe2+, Mn2+) to Fe3+, Mn4+

Elimination of Fe3+, Mn4+ in filter



Water treatment and buildings of treatment plant

Reduce filter backwash water to <5% of filtered water; less water is

used for e.g. back flushing of filters, less energy is needed; saving

water = saving energy

Reduce cycle of filter backwashing of possible (every 72 hours at

Hamburg Wasser)

What are you doing with the wastewater from backwashing? Can you

use it for other processes (after sedimentation)?

Better use cascade or flat aeration (bottom with holes) than

compressors, blowers, fans

Process optimization is energy efficiency

Reduce heating of building




Backwashing Performance

Adjust backwashing velocity to filter

material and water temperature

Reduce water for backwashing by

Air-scour wash (backwashing with

air, afterwards water) or

simultaneous air and water wash

for one-layer filters

Only air-wash for multi-layer filters

Adjust pipes to backwashing velocity

Construct nozzle floor to backwashing

pressure



Optimization by combined air + water backwashing

1. Air

2. Air + water

3. Water to get air

bubbles out of filter

bed

Saves water

Saves energy

because less water

needs to be treated for

backwashing



Optimization of processes

Energy-saving selection of processes in

water treatment

Optimal operating points aggregates

Avoid oversizing!

Adapted control (e.g. compressors)


Pumping systems in water supply chain (core processes):

1 raw water abstraction

2 water transport

3 water distribution

Typical Pumping Stations


Water

distribution

Reservoir Treatment

Plant

Transport to

water

treatment

Raw water

abstraction 1

2 3

e.g. well field

pumps or

surface water

intake pumps

Transport pump

= individual

pumps

Distribution pumps =

pumps in parallel,

hydraulic of network

need to be known



Optimization of treated water pumps

Optimal efficiencies of individual pumps and

pumping systems

Use of standard motors IE3

Adapted control (switching points)

Avoid throttle control and use of frequency

converters if control is required


Process optimization - examples from Hamburg Wasser

Exchange of 33 submersible pumps

Example waterworks Nordheide – Plant description




Well shafts:

2 well fields; 33 deep wells

depth.: 86 - 329 meters

Water treatment:

10 concrete pressure filters

3 purging pumps;

1 purge air blower

Storage:

2 drinking water reservoirs;

Volumes: 10,000 m³ +

40,000 m³ in elevated reservoirs

Drinking water pumps:

Gravity pipes DN 1,000;

1 emergency pump with 4,500 m³/h

Daily output:

40,000 – 60,000 m³

Annual output:

15.7 Mio. m³




Schamatic of WW Nordheide



Example waterworks Nordheide – Project description

Exchange of 33 well pumps

Regulation of heads via installation of

9 frequency converters – avoiding

energy loss by throttling

Variable adaption of heads and flow

rates at constant efficiency (only

useful for continuous operation and

alternating mode)

Frequency conversion: efficiency loss

~2-3%, higher power consumption

possible due to required safety margin

for e-motor Frequency converter for submersible pump



Example waterworks Nordheide

Comparison of performance curves for old/old and new/new pump

0

5

10

15

20

25

30

35

40

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160 180

He

ad[m

]

Flow rate [m³/h]

H (alte Pumpe) H (neue Pumpe) P (alte Pumpe) P (neue Pumpe)

Po

we

r co

ns

um

ptio

n [k

W]




0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0 20 40 60 80 100 120 140 160 180

Ove

rall

eff

icie

ncy

[-]

Flowrate [m³/h]

Eta ges (alte Pumpe)

Eta ges (neue Pumpe)

Comparison of performance curves for old and new pump



Energy efficiency = Economic efficiency

Specific energy need of old pump: 34.95 kWh/100m³

Specific energy need of new pump: 33.00 kWh/100m³

Yearly operation time of 6,570 h =

Energy savings of 12,780 kWh/a

Assumed energy price (Germany) of 0.15 € / kWh =

1,900 € savings per year

→ Amortization of costs for pump exchange after 4.7 years




Example waterworks Nordheide: changing a well pump

Exchange of pump


Energy generation at waterworks

E.g. by wind power (good in

northern Germany)

Possible on empty spaces

Consider danger for the public in

wintertime (falling ice from rotors)

above: turbine with generator at water works

Stellingen

left: usage of energy from drinking water via

heat exchangers for heating of buildings

Process optimization - energy generation


At waterworks Stellingen: since 2001 a

turbine with generator is installed

At waterworks Schnelsen: usage of a

portion of clean water for heating the

building complex (by heat exchanger)

Heizungsschema WW Stellingen

Plattenwärme-

übertragerZwischenkreislauf

(Klarwasser)

7 °C

8 °C

5 °CWärmepumpenheizung

Elektrische Energie

Vorlauf

Trinkwasserteilstrom

im Wasserwerk

55 – 65 °C

Gas

Gas-Zusatz-

Heizung

Warmwasser-

Speicher und

Heizsystem

Heizungsschema WW Stellingen

Plattenwärme-

übertragerZwischenkreislauf

(Klarwasser)

7 °C

8 °C

5 °CWärmepumpenheizung

Elektrische Energie

Vorlauf

Trinkwasserteilstrom

im Wasserwerk

55 – 65 °C

Gas

Gas-Zusatz-

Heizung

Warmwasser-

Speicher und

Heizsystem

above: turbine with generator at water works

Stellingen

left: usage of energy from drinking water via

heat exchangers for heating of buildings





savings per year:

Energy: 440,000 kWh

usage of drinking water for cooling of buildings


kitchen 210 kW

cooling need:

8 h/ 5 d

data centre 210 kW

cooling need:

24 h/ 7 d

Cooling machine with air

cooling

210 kW cooling capacity

drinking water distribution

to city of Hamburg


Heat exchanger at waterworks Stellingen





Options in hot countries: thermal

Possibility of photovoltaic

Which options for energy generation are

suitable for a specific region?

Suppliers available?



Is staff involved in decision making processes?

Is there a commitment of the staff to maximize

energy efficiency in the waterworks?

Does involved personnel understand the issue of

energy efficiency?

It is a Management task to ensure that involved staff:

Understands need and importance for energy

efficiency

Participates in decision making processes

Is trained to conduct energy optimization measures

Understands that process optimization is energy

optimization

Involvement of staff



Through staff training on energy efficiency,

interest on the topic rises

Greater awareness among the staff is induced

- energy is saved at the same time by this

awareness:

Staff starts to think about energy at evera

moment

Do not waste energy

Turn off equipment and appliances

Think about potentials of improvement –

even on the small skale

Involvement of staff


Success control (performance indicators)

“Performance indicators are measures of the efficiency and effectiveness of the

delivery of the services by a department that results from the combination of

several variables. The information provided by a performance indicator is the

result of a comparison – to a target value, previous values of the same

indicator, or values of the same indicator from other departments.”

(International Water Association - IWA, 2006)

Performance measurement helps the management to

Steer the department

React to variances and irregularities

Monitor the operation of the water utility

IWA Performance Indicator System – PIS



IWA Performance Indicators for Water Supply Services

IWA PIS for water services recognized as a worldwide reference, useful for

internal and external benchmarking

PIs are grouped in a structure that makes sense for every utility and for all

types of uses of the system:

Water resources (WR)

Personnel (Pe)

Physical (Ph)

Operational (Op)

Quality of service (QS)

Economic and financial (Fi)

Each group is divided into subgroups

In special cases, subgroups are broken

down into smaller units


IWA Performance Indicators for Water Supply Services


are used

For Exapmle:


PI requirements:

Each performance indicator should comply with the following

requirements:

be clearly defined, with a concise meaning

be measurable

be auditable

be as universal as possible

be simple and easy to understand

be quantifiable to provide an objective measurement

any subjective appraisal should be avoided

be unique

Only PI which are deemed essential for effective performance evaluation should be established!


Optimization of water supply using performance indicators


Process Performance Indicator System (PPIS)

Examples:

o Chemical Use in Water Treatment:

g Coagulant

m³ x NTU (Turbidity)

o Energy Efficiency of Pumps:

Kwh

m³ x m Pumping Height



Example: Specific energy consumption in catchment, treatment and

distribution of drinking water in 2005-2011

Experiences at HAMBURG WASSER


0,524

0,517

0,512

0,492 0,491 0,488

0,479

0,47

0,48

0,49

0,50

0,51

0,52

0,53

2005 2006 2007 2008 2009 2010 2011

Sp

ecific

en

erg

y c

on

su

mp

tio

n

ca

tch

me

nt, tre

atm

en

t a

nd

dis

trib

utio

n

[kW

h/m

³]

-10%

source: HAMBURG WASSER Benchmarking report 2011


Getting started


Consideration of status quo (determine/calculate existing PIs)

Discuss and agree upon additional PIs needed - as well as

about the structure

Consider measurement (you will need data)

Establish a performance indicator database (required and

existing PIs)

Collection of missing and required data

Continuous improvement of performace

Evaluation of your activities by

benchmarking of defined PIs



Benefits of performance indicators

Public, clients, authorities, politicians:

Reliable and transparent presentation of the

performed service

Organizational setup:

Development of a structured, systematic data

model

Working procedures:

Transparent working processes, comparable

results for all utility areas

External services:

Efficient, transparent evaluation of services

provided by contractors



Examples for performance indicators

related to energy efficiency in waterworks

Indicator unit

Consumption:

Specific energy consumption

during water production [kWh/m³]

Cumulated energy consumption

during water production [MWh]

Own water consumption

related to pure water production [%]

Energy optimization by own energy

production:

Energy production rate

related to overall consumption [%]



Indicator

Consumption:

Specific energy consumption

during water production

Cumulated energy consumption

during water production

Own water consumption

related to pure water production

Energy optimization

through own energy production:

Energy production rate

related to overall consumption

Target (for next year etc.)

- x kWh/m³ compared to

present value

- x MWh compared to

present value

- x % compared to

present value

+ x % compared to

present value


Generation per year:

Electricity 14 Mio. kWh/a


HAMBURG WASSER performance outlook – Horizon 2018

Reduced power consumption:

Exchange of well pumps

Maximum energy efficiency (no throttle operation)

Determination of the optimal operation point

Increased usage of water-thermal energy generation

Increased power generation

Construction of more wind generators

Placed at the water works (Commissioning late 2015)



Exercise

Questions for success control

Clear responsibilities:

Who sets the targets?

Who defines performance indicators?

Who is in charge of reporting them?

Organization:

Who is responsible for data collection?

How transparent is the process?

How is data published and accessible?

How is staff involved (staff motivation)?



Measurement points for energy consumption

Well field

Pumping station at well field

Energy in treatment esp. filter backwashing

Energy of pumping within waterworks

Energy of pumping water into system

Energy of pumping stations in the network



Measurement of water flow for energy efficiency

Amount of

Raw water coming into water works

Backwashing water

Treated water pumped into the network

Amount of water at costumers

If no data is available:

Install flow meters, calibrate and maintain them

Collect, store, evaluate the data you need


Thank you

auditing for energy efficiency in water supply and ... · energy optimization in waterworks slide 7...

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