Air Conditioning in Green Office Buildings?

Air Conditioning in Green Office Buildings? How to implement Demand Controlled Ventilation Stuttgart Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 1

Air Conditioning in Green Office Buildings ventilation heating / cooling energy pass certification DIN EN 15251 Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 2

Greenbuild Objectives compact building shape (A/V) well balanced window area (SHGC tot f Window < S max ) building mass as thermal storage low indoor loads - low pollution loads (low-olf- building) - low heating loads (< 20 W/m²) - low cooling loads (< 45 W/m²) Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 3

why Air Conditioning? high indoor air quality by mechanical ventilation - demand controlled, efficient ventilation - low draught risk (DR<15%) - low vertical temperature gradient limited room air humidity - minimal humidity in heating mode (mech. humidification) - maximal humidity in cooling mode (mech. cooling and dehumidification) limited room temperature in cooling mode - combined with decentralised secondary cooling system constraints - primary energy demand < reverence demand by EnEV 2009 - maximal rating by certification of LEED, BREAM,... Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 4

higly efficient Air Diffuser (1) low ventilation rate per diffuser, high ventilation efficiency high difference supply - room temperature (+5 to -10 K) low velocities close to the diffuser linear floor diffuser LDU air flow pattern in LTG testroom Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 5

higly efficient Air Diffuser (2) high ventilation rate per diffuser, high ventilation efficiency high difference supply - room temperature (+5 to -12 K) combination with induction unit linear slot diffuser LDB for ceilings air flow pattern in LTG testroom Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 6

Focus on Energy Efficiency heat recovery - heat recovery coefficient > 0,75 Air Handling Energy Costs per m³/h heating energy 0,06 / electr. current 0,14 / cooling energy 0,05 /kwh humidification - gliding relative humidity (>30% r.h.) - moisture recovery (>40% r.h.) cooling, dehumidification - 16-18 C supply air temperature - gliding moisture (< 12gw/kga) ventilation - low SFP- values energy costs [ / a / (m³/h) ] 0,60 0,50 0,40 0,30 0,20 0,10 0,00 ventilation; SFP = 3,2 kw / (m³/s) ventilation heat; 18 C; with / without heat recovery humidification <30%; with / without moisture transmission with without cooling; 16-18 C; with / without dehumidification - smaller air volume rates - shorter AHU running times Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 7

Certification of Indoor Air Quality Ventilation Rate [m³/h/m²] 30 25 20 15 10 5 0 Recommended Outdoor-Ventilation Rates dependent on category, low polluting (DIN EN 15251) category 1 category 2 category 3 0 5 10 15 20 Floor Area per Person [m²/p] V A out = qp A / n + q B A floor area q P ventilation rate per person q B ventilation rate for emissions from building Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 8

Design of AHU for CAV mean density of occupancy 15m²/person example (CAV-system) - low polluting building - category II 4,2 m³/h/m² (design start, SFP= 3,2 kw/(m³/s)) - category I 6,0 m³/h/m² (target value: high IAQ) - 43% higher ventilation rate - solution 1 design AHU up to 5 m³/h/m² increase ventilation rate to 6m³/h/m² by frequency inverter - solution 2 design AHU up to 6m³/h/m² same SFP & velocities Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 9

Energy Costs dependent on V/m² costs [ /m²/a ] 8 7 6 5 4 3 2 1 0 AHU Energy Costs CAV-System with 3.250 h of operating p. a. 2 3 4 5 6 7 8 ventilation rate [ m³/h/m² ] electr. current (vel. var.) electr. current (vel. const.) heating design start solution 2 solution 1 Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 10

First Costs dependent on V/m² costs [ /m 100 90 80 70 60 50 40 30 20 10 0 First Costs CAV-System 2 3 4 5 6 7 8 ventilation rate [ m³/h/m² ] AHU ducts construction costs (AHU room, shafts) increased height betw een floors Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 11

Results of CAV-System solution 1 annuity 0,1 costs of use [ /m²/a] 4,2 m³/h/m² 6 m³/h/m² difference capital costs of AHU, ducts 3,46 3,87 0,41 capital costs of building constr. 1,02 1,26 0,24 energy costs of electricity 1,90 3,78 1,88 sum 6,38 8,91 2,53 solution 2 annuity 0,1 costs of use [ /m²/a] 4,2 m³/h/m² 6 m³/h/m² difference capital costs of AHU, dutcs 3,46 4,16 0,70 capital costs of building constr. 1,02 2,18 1,16 energy costs of electricity 1,90 2,71 0,81 sum 6,38 9,05 2,67 conclusions - higher ventilation rates of CAV-systems are always linked to higher costs for energy and capital investment - are VAV-systems a better solution? Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 12

Example of a demand controlled Ventilation time 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 hour time schedule 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 AHU operation sensor of occupancy 0 0 0 0 0 0 0 0 1 1 1 1 0 1 1 1 1 0 0 0 0 0 0 0 0 decentral on / off window switch 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 decentral on / off increased mech. ventilation 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 manual switch ventilation rate [m³/h/m²] 10 8 6 4 2 0 V entilation Rates of CAV - & V AV -System s exam ple of a 2-3 persons office 0 2 4 6 8 10 12 14 16 18 20 22 24 time CAV VAV Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 13

Design of AHU for VAV-Operation cat.2 / low emission / c4 1 Person Off. 2-3 Pers.Off. Open Plan Off. Conference mean dim remarks relative frequency 9% 44% 36% 11% 100% occupancy 12 10 15 4 10,25 m²/person operation ratio F_rlt 0,7 0,7 1 0,5 draft DIN V 18599-7 u. T10, Tab. 4 absence coeff. c_rlt 0 0 0 0 draft DIN V 18599-7 u. T10, Tab. 5 design vent.rate - building 2,52 2,52 2,52 2,52 design vent.rate - build.+pers. 4,62 5,04 4,20 8,82 5,12 m³/h/m² CAV mean vent.rate V_dc 3,99 4,28 4,20 5,67 4,38 m³/h/m² with occupancy sensor operation ratio F_nat.vent. 0,7 0,7 1 0,8 natural ventilation, mech. ventilation shut off mean vent.rate V_dc 2,8 3,0 4,2 4,5 3,58 m³/h/m² with occupancy sensor & natural ventilation Comparison of CAV- & VAV-Operation VAV with occupancy sensor centralised AHU potential of electr.energy saving 30% mean ventilation rate demand on electr. energy 20 15 10 5 0 5,12 15,0 CAV 4,38 12,9 VAV with occupancy sensor 3,58 m³/h/m² 10,5 VAV with occupancy sensor & window switch kwh/m²/a 4,38 2,5 VAV by decentralized ahu & occupancy sensor & window switch AHU, ducts 15% smaller higher first costs for VAV decentralised AHU (1/room) potential of electr.energy saving 80% higher first costs for AHU ( /m³/h) higher costs for maintenance ( /m²) no ducts, no ventilation shafts, no ahu rooms Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 14

Example of a Ventilation Control System 4m/s in ducts control ratio 1:3 to 1:4 1 to 4m/s duct velocity in volume flow controler Extract Supply compact controller for supply and tracked exhaust volume flow Type VRD-W flow control principle with control ratio 1 )* - 10m/s and characteristic control field )* supported only by few manufaturers Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 15

Cost-Effectiveness of VAV-Systems savings - ventilation system & construction costs - 6 5m³/h/m² - energy costs for electricity (by VAV) extra first costs for VAV- installation - reference parameters zone of occupancy 30m² ventilated area 400m² - assumptions room automation for lighting, ventilation, heating & cooling using occupancy sensor for lighting & ventilation LON-bus - additional charge for VAV-controller compared with mech. CAV-controller - pressure & volume flow controller in main supply & extract duct 13 occupancy units - window switches 4 per room costs [ /m²/a] 2 1,5 1 0,5 0-0,5-1 -1,5 Balance Sheet VAV-CAV 0,19 0,23 1,09-0,65-0,45 costs for control units in main ducts wiring occupancy sensor costs for window switches additional charge for VAVcontroller (LON) savings by electricity savings by ventilation system Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 16

Example of a decentralised Ventilation Unit exhaustmodule exhaust ventilation damper exhaust fan extract air filter heat- & moisture recovery module heat-, moisture recovery secondary air fan supply- & secondary air mudule heat exchanger heating / cooling supply fan outdoor air filter decentralised ventilation unit FVM outdoor ventilation damper Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 17

Key-Components for green Air Conditioning diffuser - highly inductive close to diffuser (high t) - low velocity, displacement flow in occupance zone induction unit - high secondary capacity at low ventilation rate and low primary pressure - moderate supply water temperature 16 C for cooling, 30 C for heating fancoil with supply diffuser - highly efficient, low noise fan - minimised fan operation time decentralised ventilation unit - SFP < 1,5 kw/(m³/s) - VAV volume controller - high control accuracy at low velocities (1-6 m/s) supply extract ww cw wall diffuser unit LDK floor induction unit HFB fancoil floor unit VKB dec. ventilation unit FVDplus - low pressure drop when damper is open volume control unit VRF-W Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 18

Summary green air conditioning provides for high IAQ all year - at high thermal comfort - and low energy demand primary energy for ventilation, heating, cooling 75-100 kwh/m²/a green air conditioning postulates - a highly efficient use of electricity - highly efficient components - in some respect a responsible attitude of the occupant VAV-systems are, just at low ventilation rates, a sustainable solution - they are more flexible than CAV - the demand of space is smaller - they are easily shut off during natural ventilation - they are better accepted by occupant - savings balance the additional charge for VAV Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 19

Grenzstrasse 7 D - 70435 Stuttgart Tel: +49 (711) 8201-180 Fax: +49 (711) 8201-720 E-Mail: raumluft@ltg-ag.de E-Mail: prozessluft@ltg-ag.de E-Mail: ingenieurdienstleistungen@ltg-ag.de Internet: www.ltg-ag.de Rechte allein bei ICEBO 08 10.10.2008 CI / DrRo 20