RISPARMIO ENERGETICO TRAMITE RAFFRESCAMENTO ADIABATICO. Roma, 2010 speaker: Stefano Ruzzon

Transcription

1 RISPARMIO ENERGETICO TRAMITE RAFFRESCAMENTO ADIABATICO Roma, 2010 speaker: Stefano Ruzzon

2 Energy Savings in direct evaporative cooling Real application in the Madrid metro and simulated application for offices in Rome Presented by Stefano Ruzzon Product Manager Systems for Humidity Control, CAREL Industries S.r.l. Written by Raul Simonetti Application Manager Systems for Humidity Control, CAREL Industries S.r.l.

3 Adiabatic cooling with high pressure sprayer 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 B 17 C SATURATION CURVE (100%rH) 60%rH A 10%rH SPECIFIC HUMIDITY [g/kg] 30 C This is a huge amount of energy that can be used to economize on mechanical cooling

4 How does water evaporate? 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.

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

6 DEC & IEC in air ducts DEC Direct Evaporative Cooling IEC Indirect Evaporative Cooling

7 (IEC: indirect evaporative cooling) The exhaust air is humidified/cooled before entering the heat recovery unit; IEC does not humidify the indoor ambient

8 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),018,016,014,012,010,008,006,004,002 ENTHALPY - KJ PER KILOGRAM OF DRY AIR ENTHALPY - KJ PER KILOGRAM OF DRY AIR SATURATION TEMPERATURE - C DRY BULB TEMPERATURE - C HUMIDITY RATIO - GRAMS MOISTURE PER KILOGRAM DRY AIR Direct Evaporative Cooling 90% 80% 70% B A 60% 50% 40% 30% 20% 10% RELATIVE HUMIDITY HU does DEC

9 Some figures of adiabatic cooling Increment W = +1 g v /kg da decrement t -2.5 C Examples: DEC: W HU = +4 g v /kg da decrement t -10 C IEC: W HE = +4 g v /kg da decrement t HE -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 rh humidity from IEC goes to exhaust ->can be almost saturated, so usually you can add more humidity increasing the cooling effect.

10 DEC efficiency depends on initial rh 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

11 DEC: Characteristics 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 suitable Where 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 flow And with the contact surface water-air Spraying water in minuscule drops increase the contact surface. Example: 1 L of water sprayed in 10-µm drops= 600 m²

12 Adiabatic cooling tested in Madrid underground 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.

13 DEC in Peñagrande: the idea In summer time, ventilation cannot fully compensate for the indoor heat loads due to trains (electrical motors) and people waiting. In August, the outdoor conditions reach 35 C, up to 40 %rh Solutions: Chiller + cooling coil, OR DEC Chiller + cooling coil : more expensive than DEC DEC: lower cost + savings from energy saving

14 2 station for comparative test 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

15 DEC in Peñagrande station (Madrid subway) 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

16 Spraying rack and drop eliminator

17 Pump and control

18 High-pressure water atomizer certified according to VDI6022 Cabinet with high press. pump With control system and VFD (100 to litres/hr) Spraying nozzle (in rack) Rack to spray in duct/ahu with double electrovalves & AISI304 drop separator

19 Atomizer: characteristics Runs on demineralised water: Up to 50 µs/cm 0-25 ppm CaCO 3 Sprayed water pressure: 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):

20 DEC in Peñagrande: structure 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 monitoringsystem acquires: Outdoor air: temperature and humidity Dischargingair: temp. and hum. (end of duct) Ambient air: temperature and humidity

21 Data from a typical day in the stations COMPARATIVA ESTACIONES 4/09/06 El ecpa S.L. Instalaciones y Control 90,00 80,00 70,00 60,00 ºC Y %HR 50,00 40,00 30,00 20,00 10,00 0, HORA 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.

22 Reading the data rh in DUCT COMPARATIVA ESTACIONES 4/09/06 El ecpa S.L. T in second Instalaciones station (no y Control DEC) 90,00 rh after mix indoor T in station with DEC 80,00 70,00 60,00 ºC Y %HR 50,00 40,00 30,00 20,00 10,00 0, HORA 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.

23 Average results during 2 months of test In the period15/july/2006 to15 sept/2006, the temperature in the Penagrandestation 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: today13 subway stationsof Metro are equippedwithdec and more willbe equipped as budget will allow for.

24 DEC in Peñagrande:savings Parameter DEC (based on real data) Equivalent chiller (EER=2.5) Duty (June 7-25, 2006) [a] 270 hrs 270 hrs Electric power [b] 5,54 kw 146,42 kw Electric energy [c = a x b] Cost of electrical energy [d= c x 0,18 EURO/kWh] Sprayed water [e] 1496 kwh EURO litres kwh EURO 7116 Not applicable Water cost [f = e x 0,95 EURO/m³] EURO 28 Not applicable Running cost [d + f] EURO 297 EURO 7116

25 Another test in London London Underground Cooling the tube project Ducted system with humifog at Charring Cross station HumiFog ventilated units at Colliers Wood station The test is considered positive; a test with wet media was discarded as problematic

26 High-pressure water atomizer certified according to VDI6022 Cabinet with high press. pump With control system and VFD (100 to litres/hr) Spraying nozzle (in rack) Rack to spray in duct/ahu with double electrovalves & AISI304 drop separator

27 Precise modulation of water flow High pressure pump: water flow kg/h combining variable speed (with VFD) and staging (electrovalves) to obtain a continuous 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

28 Hygienic safety is needed for this application 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

29 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

30 Rome: DEC in AHU for an office (estimate) 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

31 Rome: DEC for office - AHU Main characteristics: High-pressure atomizer for DEC Free cooling by Variable Air Volume to compensate the internal heat loads

32 Rome: DEC + free cooling ASHRAE PSYCHROMETRIC CHART NO.1 NORMAL TEMPERATURE BAROMETRIC PRESSURE: 101,325 kpa R R Copyright 1992 AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING ENGINEERS, INC. SEA LEVEL,008 D h I,006 No free cooling, NO energy saving; mechanical cooling at G vent (min G E ), eventually de-humidification D3 h SET D2 I D2: partial free cooling + de-humidification Gvent : min G E SET GE : outdoor air flow GI : supply flow 90% 15,004 80% 70% 60% 50% 10,002 40% DRY BULB TEMPERATURE - C HUMIDITY RATIO - GRAMS MOISTURE PER KILOGRAM DRY AIR U1 Region U4 Heating + evap.+ free cooling U2 h E,min Partial free cooling + evaporative cooling U3 Full free cooling + evaporative cooling D3: full free cooling + de-humidification 30% 20% 10% RELATIVE HUMIDITY D4 (not shown, left of D3): de-humidification + heating + free cooling U1: No free cooling, NO energy saving; mechanical cooling at G vent (min G E ), then evaporative cooling

33 Rome: Climatic conditions Each dot represents a condition of the outdoor air D2 D3 D1 D4 U1 U4 U3 U2

34 How the simulation has been made DIPARTIMENTO DI TECNICA E GESTIONE DEI SISTEMI INDUSTRIALI FACOLTÀ DI INGEGNERIA - UNIVERSITÀ DI PADOVA 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.

35 AMBIENT AIR CONDITIONS simulation program inputs Ambient air temperature ta [ C] 22,0 Ambient air relative humidity ϕα [%] 50 Ambient air humidity ratio xa [kgv/kga] 0, ,22 Ambient air enthalpy ha [kj/kga] 43,0 EXTERNAL AIR CONDITIONS City (TRY) Venice INLET AIR CONDITIONS Inlet air temperature ti [ C] 20,0 Inlet air humidity ratio xi [kgv/kga] 0, ,21 Inlet air enthalpy hi [kj/kga] 41,0 OTHER INPUTS Persons 10 Persons Latent Load [W/pers] 50 Other Latent Load [kw] 0,0 Total Latent Load Gv [kgv/s] 0,00020 Total Latent Load Plat [kw] 0,5 Persons Sensible Load [W/pers] 75 Other Sensible Load [kw] 30,00 Total Sensible Load Psens [kw] 30,8 Ventilation (external) Air Flow Gvent [l/(s pers)] 7 Optimize External Air Flow GE? 1,00 Ventilation (external) Air Flow Gvent [m3/h] 252 Ventilation (external) Air Flow Gvent [kga/s] 0,086 Specific Latent Load xsp [kgv/kga] 0,00238 Inlet Air Flow GI [m3/h] Ventilation / Inlet Air Flow Ratio Gvent/GI 0,01 Outlet / External Air Flow Ratioα = GO/GE 0,90 HU Saturator Efficiency (nominal) ηhu 90% EER chiller 2,9 η electric plant 40% Initial month Final month Working period March October Start TimeStop Time Working time 6,00 20,00

36 Rome: DEC for office - savings Loads Total load (heat gains + ventilation) Of which by free cooling + DEC [a] Energy for de-humidifying the outdoor air [b] Free cooling + DEC net [c = a b] Electric energy saved by the chiller [d = c / EER] Electric energy used for DEC [e] Saved electric energy [f = d - e] kwh/year , kwh ca. 8.9 t of CO 2 Cost saving Saved energy [g = f x 0.18 EURO/kWh] Sprayed water: EURO/m³ [h](*) Annual saving [g h] EURO/year (*) approx. 30 liters/day, like a shower

37 DEC - conclusions 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 suitable IEC= Indirect Evaporative Cooling

38 Evaporative cooling summary: DEC Sprayer for Winter humidification in AHU Direct Evaporative Colling (DEC) in summer Can e save more energy?

39 Heat recovery to save energy, but 35 C, 40%rH 29 C, 56%rH Heat exchanger: P = 400Pa Di=1.7x1.7x1.5m; spacing 8,5mm Efficiency = 58% Power saving: 58kW 25 C, 50%rH 31 C, 36%rH m3/h 25 C 50%rH Can e save more energy?

40 Indirect Evaporative Cooling (IEC) Heat exchanger: P = 400Pa Di=1.7x1.7x1.5m;spacing 8,5mm 18 C, 100%rH 100kg/h 35 C, 40%rH 25 C, 70%rH Efficiency = 58% Power saving: 100kW 28 C, 55%rH m3/h 25 C 50%rH Energy saving = = 42 kw Cooling coil isby 42kW smaller Chiller spraying has 42kW 100kg/h less water capacity! 0,95 kw electric power ONLY!

41 Water sprayer: maintenance 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 duty change 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!!!

42 VDI 6022: maintenance of humidification section systems with vs. without recirculation VDI : OPERATIONS 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 Check the condensate drain circuit from the droplet collector tank or the cylinder in isothermal appliances 14 days Recirculated water ADIABATIC WITH RECIRCULATION ADIABATIC WITHOUT RECIRCULATION month months months months months days month months months months 24 months Supply water Exception: isothermal

43 VDI 6022: maintenance of humidification section systems with vs. without recirculation ADIABATIC WITH RECIRCULATION ADIABATIC WITHOUT RECIRCULATION VDI : OPERATIONS 14 days 1 month 3 months 6 months 12 months 24 months 14 days 1 month 3 months 6 months 12 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 When 48 hours: wash with necessary detergents/disinfectants, rinse and dry 24 months

44 VDI 6022: maintenance of humidification section systems with vs. without recirculation ADIABATIC WITH RECIRCULATION ADIABATIC WITHOUT RECIRCULATION month months months months months days month months months months VDI : OPERATIONS 14 days Droplet separator and flow rectifier: check for contamination, damage, fouling and corrosion. If (not required fouled, remove and clean by the standard the separator and check but the condition of the duct recommended) downstream of the separator. NUMBER OF MONTHLY OPERATIONS TOTAL NO. OF MONTHLY 2 6=4+2 7= OPERATIONS 1 24 months 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.

45 Bibliography VDI 6022 Hygiene requirements for ventilation and air-conditioning systems and -units ASHRAE, ASHRAE Guidelines Minimizing the Risk of Legionellosis Associated with Building Water Systems AS/NZS :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 SpA EN 13779:2004 Ventilation for non-residential buildings Performance requirements for ventilation and room-conditioning systems Vattenfall AB, LIFE-CYCLE ASSESSMENT ( 68vatt/386246envi/2005- LifeCycleAssessment.pdf#search="life%20cycle%20emissions%20-vfcom")

46 Thank you Stefano Ruzzon Product Manager Systems for Humidity Control, CAREL Industries S.r.l.