RISPARMIO ENERGETICO TRAMITE RAFFRESCAMENTO ......RISPARMIO ENERGETICO TRAMITE RAFFRESCAMENTO...

Titolo del meeting - Roma, 2010

RISPARMIO ENERGETICO TRAMITE RAFFRESCAMENTO ADIABATICO

Roma, 2010speaker: Stefano Ruzzon


Energy Savings in direct evaporative cooling

Real application in the Madrid metroand simulated application for offices in Rome

Presented by Stefano RuzzonProduct Manager – Systems for Humidity Control, CAREL Industries S.r.l.

Written by Raul SimonettiApplication Manager – Systems for Humidity Control, CAREL Industries S.r.l.


100 kg/h of water atomized into the air provide a cooling effect of 68 kW! (with a consumption <1 kW) by simply changing its status from liquid to gas

SP

EC

IFIC

HU

MID

ITY

[g/k

g]

SATURATION C

URVE (100

%rH

)

60%

rH

10%rH

B

17°°°°C

A30°C

This is a huge amount of energy that can be used to economize on mechanical cooling

Adiabatic cooling with high pressure sprayer


Because the contact surface between water droplets and air is increased by atomization (high pressure pump and special nozzles)

For 1 litre of water atomised into droplets with an average diameter of 10 µm, the total surface area of the droplets in contact with air is 600 m².

How does water evaporate?


The portion of water evaporated is proportional to the time it remains in contact with air: Time = evaporation length / air speedThe non-evaporated droplets are removed and drained by the drop separator (evaporation efficiency)Es 1.5m, 3m/s ->t=0.5s, eff. appx 95%

Air flow

How quickly does water evaporate?


DECDirect Evaporative Cooling

IECIndirect Evaporative Cooling

DEC & IEC in air ducts


The exhaust air is humidified/cooled before entering the heat recovery unit; IEC does not humidify the indoor ambient

(IEC: indirect evaporative cooling)


Cooling by water evaporation: approx. 680 W/(L/h) of cooling capacity

Implies adiabatic humidification of ambient air (unlike in IEC, the ambient rH is increased)

10 20 30 40 50

60

70

80

90

100

ENTHALPY - KJ PER KILOGRAM OF DRY AIR

30

40

50

60

ENTHALPY -

KJ PER K

ILOGRAM

OF D

RY AIR

SATURATION T

EMPERATURE -

°C

5 10 15 20 25 30 35 40 45 50

DR

Y B

UL

B T

EM

PE

RA

TU

RE

- °C

,002

,004

,006

,008

,010

,012

,014

,016

,018

10% RELATIVE HUMIDITY

20%

30%

40%

50%

60%

70%

80%

90%

HU

MID

ITY

RA

TIO

- G

RA

MS

MO

IST

UR

E P

ER

KIL

OG

RA

M D

RY

AIR

A

B

HU does DEC

Direct Evaporative Cooling


Increment ∆∆∆∆W = +1 gv/kgda �� decrement ∆∆∆∆t ≅≅≅≅ -2.5 °C

Examples:DEC: ∆WHU = +4 gv/kgda � decrement ∆t ≅ -10 °C

IEC:∆WHE = +4 gv/kgda � decrement ∆tHE ≅ -10 ° x 0.50 = -5 °C

Based on the assumption that HE’s efficiency = 50%

But: humidity from DEC goes into the ambient ->must be at an acceptable rHhumidity from IEC goes to exhaust ->can be almost saturated, so usually you can

add more humidity increasing the cooling effect .

Some figures of adiabatic cooling


The dryer the intake air, the greater the temperature decrease.

Examples:1)Intake air 30°C 50%rH

humidified to 70%rH -> 26°C

2)Intake air 30°C 20%rH, humidified to 70%rH

-> 19°C

DEC efficiency depends on initial rH


Convenient where outdoor air is dry for most of the year (i.e. not in Northern Italy, where IEC is more suitable)IEC= Indirect Evaporative Cooling

Can be used where adiabatic humidification is suitableWhere machinery develop heat (printing factories, textile, data centers…)

Cooling effect: 680 W per L/h of evaporated water

It increases with the water evaporation:With the sprayed water flowAnd with the contact surface water-airSpraying water in minuscule drops increase the contact surface.Example: 1 L of water sprayed in 10-µm drops= 600 m²

DEC: Characteristics


Adiabatic air conditioning system at the platforms of Peñagrande subway station, in Camino de Ganapanes street, Madrid.

The aim of this solution is to provide more comfort, cooling the environment using water as a “source of power”, because it’s considerably more economic than traditional cooling systems (direct expansion) as it consumes less power.

Adiabatic cooling tested in Madrid underground


In summer time, ventilation cannot fully compensate for the indoor heat loadsdue to trains (electrical motors) and people waiting.

In August, the outdoor conditions reach 35 °C, up to 40 %rH

Solutions:Chiller + cooling coil, ORDEC

Chiller + cooling coil : more expensive than DECDEC: lower cost + savings from energy saving

DEC in Peñagrande: the idea


For evaluating the benefits of the DEC solution, a comparative installation has been built in two subway stations along the same line, so that they have the same outdoor conditions, same number of trains, passengers, etc:

Penagrande station:equipped with DEC and monitored

Illustracion station:monitored only

2 station for comparative test


2 platforms

2 AHUs to compensate the indoor heat loads:

• Each rated 90,000 m³/h (as per design), 100% outdoor air

• No cooling coil

DEC in Peñagrande station (Madrid subway)


Spraying rack and drop eliminator


Pump and control


Cabinet with high press. pumpWith control system and VFD

(100 to 5.000 litres/hr)

Spraying nozzle(in rack) Rack to spray in duct/AHU with

double electrovalves& AISI304 drop separator

High-pressure water atomizercertified according to VDI6022


Runs on demineralised water:

Up to 50 µS/cm0-25 ppm CaCO3

Sprayed water pressure: 20-80 bar

Water flow modulated by VFD upon demand

Specific power consumption: 5-10 W/(L/h) of water

External R.O. system included

Hygienic compliance for use in AHU also for

hospitals (local laws/norms apply):

Atomizer: characteristics


High-pressure atomizer in each AHU

Water flow controlled by a humidity probe downstream in the duct

Brings outdoor air from 35 °C, 40 %rH to 27 °C, 70%rH

Real outdoor air flow: 71,818 m³/h per AHU

Evaporated water: 277 kg/h per AHU

The monitoring system acquires:

• Outdoor air: temperature and humidity

• Discharging air: temp. and hum. (end of duct)

• Ambient air: temperature and humidity

DEC in Peñagrande: structure


COMPARATIVA ESTACIONES 4/09/06

0,00

10,00

20,00

30,00

40,00

50,00

60,00

70,00

80,00

90,00

12.3

0

13.0

0

13.3

0

14.0

0

14.3

0

15.0

0

15.3

0

16.0

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0

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0

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0

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0

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0

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0

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0

23.0

0

23.3

0

HORA

ºC Y

%H

R

Tª EXT. PEÑAG. Tª EXT. ILUST. Tª AMB. PEÑAG. Tª AMB. ILUST. Tª IMP. PEÑAG. Tª IMP. ILUST.

HR EXT. PEÑAG. HR EXT. ILUST. HR AMB. PEÑAG. HR. AMB. ILUST. HR IMP. PEÑAG. HR IMP. ILUST.

El ecpa S.L.Instalaciones y Control

Data from a typical day in the stations


COMPARATIVA ESTACIONES 4/09/06

0,00

10,00

20,00

30,00

40,00

50,00

60,00

70,00

80,00

90,00

12.3

0

13.0

0

13.3

0

14.0

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0

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0

16.3

0

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0

17.3

0

18.0

0

18.3

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0

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0

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0

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0

21.3

0

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23.0

0

23.3

0

HORA

ºC Y

%H

R

Tª EXT. PEÑAG. Tª EXT. ILUST. Tª AMB. PEÑAG. Tª AMB. ILUST. Tª IMP. PEÑAG. Tª IMP. ILUST.

HR EXT. PEÑAG. HR EXT. ILUST. HR AMB. PEÑAG. HR. AMB. ILUST. HR IMP. PEÑAG. HR IMP. ILUST.

El ecpa S.L.Instalaciones y ControlrH in DUCT

rH after mix indoor

T in second station (no DEC)

T in station with DEC

Reading the data


In the period 15/july/2006 to 15 sept/2006, the temperature in the Penagrande station

was 3.4°°°°C (=6,1°°°°F) colder than in the Illustration station, not equipped and used for

comparison

When compared to traditional systems using direct expansion, water coolers with

compressors, roof-tops etc, the fundamental advantage of the adiabatic cooling

system is its low power consumption.

The test in Madrid was considered positive:

today 13 subway stations of Metro are equipped with DEC and more will be

equipped as budget will allow for.

Average results during 2 months of test


146,42 kW5,54 kWElectric power [b]

EURO 7116EURO 297Running cost [d + f]

Not applicableEURO 28Water cost [f = e x 0,95 EURO/m³]

Not applicable29850 litresSprayed water [e]

EURO 7116EURO 269Cost of electrical energy[d= c x 0,18 EURO/kWh]

39535 kWh1496 kWhElectric energy [c = a x b]

270 hrs270 hrsDuty (June 7-25, 2006) [a]

Equivalent chiller

(EER=2.5)

DEC

(based on real data)

Parameter

DEC in Peñagrande:savings


London Underground – “Cooling the tube” projectDucted system with humiFog at Charring Cross stationHumiFog ventilated units at Colliers Wood station

The test is considered positive; a test with wet media was discarded as problematic

Another test in London…


Cabinet with high press. pumpWith control system and VFD

(100 to 5.000 litres/hr)

Spraying nozzle(in rack) Rack to spray in duct/AHU with

double electrovalves& AISI304 drop separator

High-pressure water atomizercertified according to VDI6022


0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 120 140 160 180 200

water flow kg/h

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 120 140 160 180 200

water flow kg/h

High pressure pump:

combining variable speed (with VFD) and staging(electrovalves)to obtain acontinuous modulation in a wide range with:• no recirculation• no wetting • no waste• less wear out

This linear response diagram results from the combination of speed control AND staging

Precise modulation of water flow


• no water recirculation (VFR)• demineralized water (no salts)• no chemical biocide that accumulates in the ambient• all stainless steel components including droplet separator• complete automatic water drains and flushing cycles obtained with inlet + outlet electrovalves

Hygienic safety is needed for this application


Rome: a simulation of DEC in an office

A simulation of DEC with the same principle has been made for Rome, with its climatic situation represented in this chart


Conditions considered:

Office for 40 persons

Set point: 21 °C, 50 %rH

Air quality: IDA 1 (pure, as per EN 13779:2004)

Supply temperature: 18 °C (point I of chart on slide 12)

Ventilation: 6-20 every day, all year long

1 kWh = 0.18 EURO

1 m³ of mains water= 1.28 EURO

Comparison between:

• DEC: high-pressure atomizer with saturation efficiency= 90%

• Chiller + cooling coil: EER= 2.5

Rome: DEC in AHU for an office (estimate)


Main characteristics:High-pressure atomizer for DECFree cooling by Variable Air Volume to compensate the internal heat loads

Rome: DEC for office - AHU


R R

ASHRAE PSYCHROMETRIC CHART NO.1NORMAL TEMPERATURE

BAROMETRIC PRESSURE: 101,325 kPa

Copyright 1992AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR- CONDITIONING ENGINEERS, INC.

SEA LEVEL

5

10

15

20

25

30

10 15 20 25

DR

Y B

ULB

TE

MP

ER

AT

UR

E -

°C

,002

,004

,006

,008

10% RELATIVE HUMIDITY

20%

30%

40%

50%

60%

70%

80%

90%

HU

MID

ITY

RA

TIO

- G

RA

MS

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IST

UR

E P

ER

KIL

OG

RA

M D

RY

AIR

R R

ASHRAE PSYCHROMETRIC CHART NO.1NORMAL TEMPERATURE

BAROMETRIC PRESSURE: 101,325 kPa

Copyright 1992AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR- CONDITIONING ENGINEERS, INC.

SEA LEVELD1

No free cooling, NO energy saving;

mechanical cooling at Gvent (min G

E),

eventually de-humidification

D2D3

Region U4

Heating + evap.+

free cooling

U1U2

Partial free cooling +

evaporative cooling

U3Full free cooling +

evaporative cooling

hSET

hI

SET

hE,min

I

U1: No free cooling, NO energy saving; mechanical cooling at Gvent (min GE), then evaporative cooling

D2: partial free cooling + de-humidification

D3: full free cooling + de-humidification

G I: sup

ply flo

w

G E: ou

tdoo

r air flo

w

G vent: min G

E

D4 (not shown, left of D3):de-humidification +heating + free cooling

Rome: DEC + free cooling


D2

D3

D4

D1

U1

U4U3 U2

Each dot represents a condition of the outdoor air

Rome: Climatic conditions


The simulation has been performed thanks to a programme developed by the University of Padova, Department of Technics and Management, to estimate the energy savings with the usage of DEC or IEC techniques. The programme uses a climatic database with 1-hour resolution available for most cities in the world; the inputs are setpoint, number of people and other thermal loads, efficiency of evaporation and so on.

DIPARTIMENTO DI TECNICA E GESTIONE

DEI SISTEMI INDUSTRIALIFACOLTÀ DI INGEGNERIA - UNIVERSITÀ DI PADOVA

How the simulation has been made


simulation program inputs

Ambient air temperature tA [°C] 22,0Ambient air relative humidity ϕΑϕΑϕΑϕΑ [%] 50

Ambient air humidity ratio xA [kgv/kga] 0,00822 8,22Ambient air enthalpy hA [kJ/kga] 43,0

City (TRY) Venice

Inlet air temperature tI [°C] 20,0Inlet air humidity ratio xI [kgv/kga] 0,00821 8,21

Inlet air enthalpy hI [kJ/kga] 41,0

Persons 10Persons Latent Load [W/pers] 50

Other Latent Load [kW] 0,0Total Latent Load Gv [kgv/s] 0,00020Total Latent Load Plat [kW] 0,5

Persons Sensible Load [W/pers] 75Other Sensible Load [kW] 30,00

Total Sensible Load Psens [kW] 30,8Ventilation (external) Air Flow Gvent [l/(s pers)] 7

Optimize External Air Flow GE ? 1,00Ventilation (external) Air Flow Gvent [m3/h] 252Ventilation (external) Air Flow Gvent [kga/s] 0,086

Specific Latent Load ∆xsp [kgv/kga] 0,00238Inlet Air Flow GI [m3/h] 44.914

Ventilation / Inlet Air Flow Ratio Gvent/GI 0,01Outlet / External Air Flow Ratioαααα = GO/GE 0,90

HU Saturator Efficiency (nominal) ηηηηHU 90%EER chiller 2,9

ηηηη electric plant 40%

Initial month Final monthWorking period March October

Start TimeStop TimeWorking time 6,00 20,00

AMBIENT AIR CONDITIONS

EXTERNAL AIR CONDITIONS

INLET AIR CONDITIONS

OTHER INPUTS


110,4Electric energy used for DEC [e]

1590Annual saving [g – h]

14Sprayed water: 11039 litres/yr @ 1.28 EURO/m³ [h](*)

1604Saved energy [g = f x 0.18 EURO/kWh]

EURO/yearCost saving

8914 kWh

ca. 8.9 t of CO2

Saved electric energy [f = d - e]

9024Electric energy saved by the chiller [d = c / EER]

22561Free cooling + DEC net [c = a – b]

3667Energy for de-humidifying the outdoor air [b]

26228Of which by free cooling + DEC [a]

38407Total load (heat gains + ventilation)

kWh/yearLoads

(*) approx. 30 liters/day, like a shower …

Rome: DEC for office - savings


DEC is convenient, because it cools the air by exploiting the latent heat of water evaporation (680 W/[L/h])

DEC by high-pressure water sprayer uses 5-10 W/(L/h), approx. equal to 4% the power of an equivalent chiller + cooling coil

Less pollution: each kWh saved corresponds to 1 t of CO2 not introduced into the atmosphere (average value)

DEC is convenient where adiabatic humidification is suitable and where outdoor air is warm and dry for most of the year not in Northern Italy, where IEC is more suitableIEC= Indirect Evaporative Cooling

DEC - conclusions


Sprayer for

• Winter humidification in AHU

• Direct Evaporative Colling (DEC) in summer

Can e save more energy?Can e save more energy?

Evaporative cooling summary: DEC


25°C

50%rH

25°C,

50%rH

35°C, 40%rH

31°C, 36%rH

29°C, 56%rH

30’000m3/h

Power saving: 58kW

Heat exchanger: ∆P = 400Pa

Di=1.7x1.7x1.5m; spacing 8,5mm

Efficiency = 58%

Heat recovery to save energy, but…

Can e save more energy?Can e save more energy?


25°C

50%rH

18°C, 100%rH

100kg/h

35°C, 40%rH

28°C, 55%rH

25°C, 70%rH

30’000m3/h

Power saving: 100kW

Heat exchanger: ∆P = 400Pa

Di=1.7x1.7x1.5m;spacing 8,5mm

Efficiency = 58%

Energy saving = 100 – 58 = 42 kW

by

spraying 100kg/h water

0,95 kW electric power ONLY!

Cooling coil is 42kW smaller

Chiller has 42kW less capacity!

Indirect Evaporative Cooling (IEC)


Thanks to the use of demineralised water, maintenance on the high-pressure water sprayer is limited to its pump:

change the oil every 2,000 hours of dutychange the gaskets and valves every 4,000 hrs of duty

Dedicated warnings are generated every 2,000 hours

Why using a high pressure sprayer instead of an air washer or wet media?(1) Capacity modulation and (2) maintenance costs !!!

Water sprayer: maintenance


ADIABATIC WITH RECIRCULATION ADIABATIC WITHOUT RECIRCULATION VDI 6022-2006: OPERATIONS

14 days

1 month

3 months

6 months

12 months

24 months

14 days

1 month

3 months

6 months

12 months

24 months

Complete hygienic inspection by a specialist

� �

Control of contamination, damage, microbial proliferation and corrosion: cleaning and repairs

� �

Check for condensate in the humidification section

�

Bacterial count on the water: if > 1,000 CFU/ml (1 CFU/ml for Legionella pneumophila), wash with disinfectants, rinse, dry; analysis of supply water quality

� Recirculated

water

� Supply water

Exception: isothermal

Check the condensate drain circuit from the droplet collector tank or the cylinder in isothermal appliances

�

VDI 6022: maintenance of humidification sectionsystems with vs. without recirculation


ADIABATIC WITH RECIRCULATION ADIABATIC WITHOUT RECIRCULATION VDI 6022-2006: OPERATIONS

14 days

1 month

3 months

6 months

12 months

24 months

14 days

1 month

3 months

6 months

12 months

24 months

Check the recirculating pump for contamination and fouling in the water lines and check the condition of the filters: clean the pump water circuit.

�

Inspect the atomiser nozzles for fouling: clean or replace the nozzles

� �

Check the limit probe � Functional test on the conductivity meter: calibration

�

Functional test on the sterilisation device: repair

�

Check the automatic shutdown mechanisms

�

Clean the humidifier if shut down for more than 48 hours: wash with detergents/disinfectants, rinse and dry

When necessary



ADIABATIC WITH RECIRCULATION ADIABATIC WITHOUT RECIRCULATION

VDI 6022-2006: OPERATIONS

14 days

1 month

3 months

6 months

12 months

24 months

14 days

1 month

3 months

6 months

12 months

24 months

Droplet separator and flow rectifier: check for contamination, damage, fouling and corrosion. If fouled, remove and clean the separator and check the condition of the duct downstream of the separator.

�

� (not required

by the standard but

recommended)

NUMBER OF MONTHLY

OPERATIONS 2 4 1 1 1 1 0 2 2 3 0 1

TOTAL NO. OF MONTHLY

OPERATIONS1 2 6=4+2 7=6+1 8 9 10 0 2 4 7 7 8

1 This is the number of preventive maintenance operations that must be completed in the month in question: this is the total of the operations

indicated with the “�” in the corresponding column + the operations indicated in the columns to the left of this (more frequent) . Example for recirculating adiabatic humidifiers: every 6 months the operation of the sterilisation device must be checked (“6 months”) + the operation in the “3 months” column + the 4 monthly operations + the 2 monthly bacteriological analyses, giving a total of 8 operations every 6 months.



VDI 6022 “Hygiene requirements for ventilation and air-conditioning systems and -units”ASHRAE, “ASHRAE 12-2000 Guidelines – Minimizing the Risk of Legionellosis Associated

with Building Water Systems”AS/NZS 3666.1:2002, “Air-handling and water systems of buildings—Microbial control”Subdirección General de Sanidad Ambiental y Salud Laboral, “GUIA TÉCNICA PARA LA

PREVENCIÓN Y CONTROL DE LA LEGIONELOSIS EN INSTALACIONES”Renato Lazzarin, Luigi Nalini, “Air humidification - Technical, health and energy aspects”,

CAREL SpAEN 13779:2004 “Ventilation for non-residential buildings – Performance requirements for

ventilation and room-conditioning systems”Vattenfall AB, “LIFE-CYCLE ASSESSMENT”

(http://www.vattenfall.com/www/vf_com/vf_com/Gemeinsame_Inhalte/DOCUMENT/360168vatt/386246envi/2005-LifeCycleAssessment.pdf#search="life%20cycle%20emissions%20-vfcom")

Bibliography


Thank you

Stefano Ruzzon

Product ManagerSystems for Humidity Control, CAREL Industries S.r.l.

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