Transcript Slide 1
Riga Technical University Institute 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 Starting point – the form Sphere The lowest possible area/volume ratio Can be expressed as - 3/r A/V ratio of a sphere with the same volume – 0.2 Cylinder 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 A/V ratio – 0.25 Building envelope Description of external constructions: •External wall - 0.14W/m²K; •Roof - 0.12Wm²K; •External floor - 0.33W/m²K; •Air tightness - 0.6ACH at 50Pa; Window description: •U - value - 1.2W/m²K; •G - value - 0.62; •Tsolar - 0.54; •Tvisible - 0.8; Concrete building body and slabs help to achieve greater thermal mass for accumulating heat during occupied hours. Night cooling – predicted air movement Predicted air exchange rate – 5 ACH Night cooling – simulated air movement Simulated air exchange rate – 7.9 ACH, Indoor/Outdoor temperature difference – 10K, No wind present 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 Benefits of 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% 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 Mechanical cooling + cooling + night cooling shading devices Mechanical cooling + shading Absolute devices + night reduction cooling 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 multistorey 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!