Subtropical Cities September Design for Energy Efficiency in Commercial Buildings in Queensland

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Owen Lynch
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1 Subtropical Cities September 2006 Design for Energy Efficiency in Commercial Buildings in Queensland

2 Contents Typical Building Constraints & Requirements Understanding Energy Consumption in Buildings HVAC System Options System Option Implications Capital Cost Maintenance Plant Area Floor to Floor Height Indoor Air Quality Energy Consumption Infiltration & Condensation Summary

3 Constraints & Requirements Lack + of + Space = Building Height Sub-Tropical Climate Capital Cost $ Maintenance Temperature ( C) Energy Demand Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Date: Mon 01/Jan to Mon 31/Dec Wet-bulb temperature: (HongKong90.fwt)

4 Achieving good design outcomes? Change our expectations? -> expanded comfort parameters difficult in air conditioned environments Change locations? Break the laws of thermodynamics? Holistic design? -> consider all factors effecting comfort and how the building design deals with those factors

5 Seek to maximise key features in building design: Maximising external views through clear facades; Controlling glare and direct solar penetration through appropriate building orientation, external shading and fenestration design; Maximising natural light penetration through use of light shelves and appropriate fenestration design; Maximising natural ventilation as appropriate; Minimising energy consumption through efficient air-conditioning design.

6 Factors that affect occupants Air temperature; Surface temperature and emissivity; Direct solar radiation; Relative humidity; Acclimatisation; Occupant density; Occupant clothing and activity levels; and Air movement and freshness.

7 Understanding Building Energy Consumption Tenant Cond. Water Loop 2.0% Exterior Lighting 1.2% Lift Motor Room AC 0.8% Hydraulic & Fire Pumps 0.5% Electrical Losses 2.4% Heating 0.0% Domestic Hot Water 2.5% Misc Non Tenant Loads 6.4% Central Plant Pumps 6.4% Chillers 31.3% Lifts & Escalators 8.5% Common Area Lighting 12.7% Fans 25.3%

8 HVAC System Options VAV System Displacement System Chilled Ceiling System

9 HVAC System Options Supply Air 8 C Supply Air 8 C C hille d ce ilings C hille d be am s Ra dian t c o o lin g C on ve ctive c oo ling CHILLED CEILING AND BEAMS

10 Variable Air Volume System Variable Air Volume System RSH < 200 W/m 2 Supply air > 12 C S/R air < 10 K Induction diffusers <500 L/s per diffuser Low Temperature Air VAV System RSH < 200 W/m 2 Supply air > 8 C S/R air < 16 K High induction air diffusers <500 L/s per diffuser

11 Displacement Ventilation Displacement System RSH < 30W/m 2 Supply air > 20 C S/R Air < 7 C Displacement diffusers <14 L/s per diffuser Micro-Climate RSH < 80W/m 2 Supply air > 17 C S/R Air < 10 C Induction diffusers <50 L/s per diffuser

12 Chilled Ceilings and Beams Passive Type Ceilings /Beams Up to 85 W/m mm min. Requires additional outdoor air supply Supply water temperature > 15 C Supply / Return Water +2 K Active Type Beams Up to 250 W/m mm depth incorporates primary air supply Supply water temperature > 15 C

13 VAV System Height Requirements

14 Displacement System Height Requirements 3500

15 Chilled Ceiling System Height Requirements 3400

16 Building Height 4 Floors 6 Floors 16 m 22 m VAV System Displacement Chilled Ceiling

17 Cost Comparison Capital Cost Maintenance Cost $ / m $ / m VAV System Displacement System Chilled Ceiling System 0

18 Plant Area Comparison VAV System Displacement System Chilled Ceiling System Minimum Floor to Floor Height Additional building height over 63 floors Estimated Additional Riser Area over 63 Levels Air Handling Plantroom Area mm 3,750 3,500 3,400 m m m 2 5,000 4,000 1,000

19 Indoor Air Quality & Comfort VAV System Mixed flow Zone control Air Flow vs Ceiling Height Displacement System Mixed flow for low ceilings Individual occupant control Pollutants rise to extract L/s per m Temperature Gradient : 2.0 K/ Temperature Gradient : Chilled Ceiling 100% outdoor 1/L/s per m 2 Zone control Ceiling Height

20 Energy Modelling Zone Maximum Air Flow (L/s/m 2 ) VAV System Displacement Chilled Ceiling Perimeter Core

21 Brisbane Energy Consumption Comparison Total Building Energy Consumption kwh/m2.pa Water cooled VAV Air cooled VAV Chilled beam

22 Hong Kong Energy Consumption Comparison Total Buildng Energy Consumption kwh/sqm.a VAV System Displacement System Chilled Ceiling System

23 Brisbane Energy Consumption Comparison Building Energy Use Fans Space cooling Common area lighting Pumps Exterior Lighting Lifts Switchboard losses Heating (electric) Domestic Hot Water 800, , ,000 kwh per year 500, , , , ,000 0 Water cooled VAV Air cooled VAV Chilled beam

24 Hong Kong Energy Consumption Comparison

25 Sub Tropical Climate Brisbane ( C db) C Hour

26 Sub Tropical Climate Brisbane ( C wb) C Hours

27 Energy Cost Comparison Energy Cost Demand Cost $ / m VAV System Displacement System Chilled Ceiling System

28 Climatic Psychrometric Considerations Why Displacement Systems are suited to dry climates! Brisbane Canberra O

29 Infiltration and Condensation Leaky 3.4 AC/hr Average 1.6 AC/hr Tight 0.8 AC/hr Very Tight 0.1 AC/hr Air Tight 0.0 AC/hr

30 Life Cycle Cost Comparison Year Life Cycle NPV 20 Year Life Cycle NPV $ / m VAV System Displacement System Chilled Ceiling System

31 Summary Chilled ceiling systems are more suited to tropical climates than displacement systems Chilled ceiling systems provide the following benefits in subtropical climates: Potential for up to 15% reduction in total base building energy consumption Improve indoor air quality through 100% outdoor air delivery Reduces building height for same NLA or increases NLA for same building height Lowest Net Present Value option in sub-tropical climate Caution: Chilled ceiling systems must be installed in buildings with minimal infiltration levels of 0.1 ac/hr or less with air pressurisation system operating

32 Other Low Energy Strategies Extensive dedicated sub-metering system using Smart Meters. Dedicated lighting control system to serve all lighting including tenant, common areas, and external lighting. Internal blinds on all facades. To reduce radiant temperature and glare levels. Provide low load chillers. One air handling unit per façade. No in-duct heating, in electric or hydronic form is to be provided anywhere. Design for allow for after-hours use. Floor by floor plant is ideal Provide full air tight shut-off in after hours periods. Where VAVs are used, commission to turn down to 25% for the perimeter zones and 40% in the central zones. Main air handling plant should be designed and selected to achieve a maximum total static resistance of no more than 800 Pa. Consider low temperature air system. Lighting control system to serve plantrooms. Naturally lit fire stairs Variable speed drives to the tenant condenser water pumps. Solenoid valves shut-off to serve all water cooled packaged air conditioning units. Filter over static alarms on all air handling units. Photoelectric daylight sensors for perimter zones Light coloured roofs. Specify high efficiency chillers. Select cooling towers to return depressed condenser water temperatures to the chillers All HVAC plant must operate on BMS time-switches to shut down after normal operating hours

Energy Efficient HVAC-system and Building Design

Energy Efficient HVAC-system and Building Design Maija Virta 1, Harri Itkonen 1, Panu Mustakallio 1, Risto Kosonen 1 1 Halton Oy, Finland Corresponding email: maija.virta@halton.com SUMMARY This paper