riga technical university institute of heat, gas and water technology
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OFFICE BUILDING NIGHT COOLING POTENTIAL IN BALTIC REGION. Riga Technical University Institute of Heat, Gas and Water technology. RENARS MILLERS, ALEKSANDRS ZAJACS, ARTA USELONOKA. General information: Location – 56.97 ° N, 24.07° E (Riga), Site – outside city centre, - PowerPoint PPT PresentationTRANSCRIPT
Riga Technical UniversityInstitute of Heat, Gas and Water technology
OFFICE BUILDING NIGHT COOLING POTENTIAL IN BALTIC REGION
RENARS MILLERS, ALEKSANDRS ZAJACS, ARTA USELONOKA.
General information:
Location – 56.97° N, 24.07° E(Riga),
Site– outside city centre, surrounding agglomeration 2-4 storey buildings
Model ground area - 662m2 Volume – 14214m3 Height – 6 storeys, 24m
Envelope/volume ratio (Net) – 0.24m2/m3 Envelope/volume ratio (Gross) – 0.25m2/m3 Window/envelope ratio – 32%
Solar protection – standard glazing + shading devices
Cooling technique – Mechanical cooling + night cooling
The lowest possible area/volume ratioCan be expressed as - 3/r
A/V ratio of a sphere with the same volume – 0.2
Starting point – the form
Sphere
If h=D then A/V ratio can be expressed as - 3/r
A/V ratio of a sphere with the same volume – 0.22
Cylinder
A/V ratio – 0.25
Window description:
•U - value - 1.2W/m²K;•G - value - 0.62;•Tsolar - 0.54;•Tvisible - 0.8;
Description of external constructions:
•External wall - 0.14W/m²K;•Roof - 0.12Wm²K;•External floor - 0.33W/m²K;•Air tightness - 0.6ACH at 50Pa; Concrete building body and
slabs help to achieve greater thermal mass for accumulating heat during occupied hours.
Building envelope
Night cooling – predicted air movement
Predicted air exchange rate – 5 ACH
Simulated air exchange rate – 7.9 ACH, Indoor/Outdoor temperature difference – 10K, No wind present
Night cooling – simulated air movement
The benefits of night cooling
Mechanical cooling
Mechanical cooling + night cooling
Absolute reduction
Relative reduction
Annual energy consumption for cooling, kWh/m²
17 8 -9 -53%
Peak load, kW 247 217 -30 -12%
Simple shading design
No external shading devices With external shading devices
Mechanical cooling Mechanical cooling + shading devices
Absolute reduction
Relative reduction
Annual energy consumption for cooling, kWh/m²
17 12 -5 -29%
Peak load, kW 247 197 -50 -20%
Benefits of shading devices
Heat balance of typical room on the south side
No shading, no night cooling
Shading, night cooling
Shading devices in combination with night cooling as passive cooling approach
Mechanical cooling
Mechanical cooling + night cooling
Mechanical cooling + shading devices
Mechanical cooling + shading
devices + night cooling
Absolute reduction
Relative reduction
Annual energy consumption for cooling, kWh/m²
17 8 12 4 -13 -76%
Peak load, kW 247 217 197 138 -109 -44%
Reduction from night cooling – 30kW
Reduction from shading devices – 50kW 80kW
Conclusions:• Stack effect can boost air exchange rate during night cooling in multi-
storey building• Night cooling in this case is more effective for reducing energy
consumption – 53%• Shading devices are more effective to reduce peak load – 20%• Significant reduction of pike load – 44% can be achieved when using both
– night cooling and shading design in combination.
Thank you for your attention!