MODELLING THE ENERGY PERFORMANCE

Transcription

1 IBPSA Nordic 203 (Lund) 20 / 09 / 203 MODELLING THE ENERGY PERFORMANCE OF NIGHT-TIME VENTILATION QUASI-STEADY STATE CALCULATION METHOD EN ISO 3790 Jérôme LE DRÉAU Per HEISELBERG, Rasmus JENSEN, Ayser SELMAN What is the goal of night-time ventilation? o Achieve thermal comfort during the transition/summer season o Avoid the use of mechanical cooling system Principle: making use of the exposed thermal mass o The building structure is cooled down overnight with relatively cold outdoor air o Heat sink available during the occupied period of the next day 2

2 Problem: How to take into consideration the dynamic effects of night-time ventilation in the monthly calculation method? Plan: Principle of the calculation method o Cooling need in EN ISO 3790 o Methods tested for modelling night-time ventilation Development of the correction coefficients o Presentation of the simulation cases o Results Selection & Validation of the correction factors (not included in the paper) 3 PRINCIPLE OF THE CALCULATION METHOD 4 2

3 How is calculated the cooling need in EN ISO 3790? Solar heat gains Ventilation Internal heat gains Transmission Monthly heat balance, = + η [0; ] + 5 Why do we need correction coefficients? 6 Cooling consumption (kwh/m² per year) BSim - 2 zones Monthly basic 0 No NTV 3 ACH 5 ACH 7 ACH 9 ACH Þ Overestimation of the capacity of NTV without correction coefficients limited heat storage capacity (function of the thermal mass) limited temperature variation in the building (from 20 C to 26 C) 6 3

4 Methods tested for modelling night-time ventilation, = + η + =, +,, = Method (proposed in EN ISO 3790) Method 2 7 DEVELOPMENT OF THE CORRECTION COEFFICIENTS 8 4

5 Development of the models o Danish climate o single office room ( m) o 55 % of the façade glazed, no solar shading 288 simulations o 6 levels of thermal mass (60 40 Wh/K.m²) o 4 orientations o 2 levels of internal heat loads o NTV: - maximum time of operation 60 (from 8h to 5h) 50-4 up to 7.5 ACH Effect of night-time ventilation (South facing room) Q C,nd (kw.h/m 2 ) Top view No NTV NTV 8h NTV 2h NTV 5h C m (Wh/K.m 2 ) 9 Parameters influencing and o Major influence of the thermal mass o Minor influence of the maximum time of operation Method Method C ve (-) NTV 8h - 6ACH NTV 8h - 7.5ACH NTV 2h - 5ACH NTV 2h - 6ACH NTV 5h - 4ACH NTV 5h - 5ACH C m (Wh/K.m 2 ) C g (-) NTV 8h - 6ACH NTV 8h - 7.5ACH NTV 2h - 5ACH NTV 2h - 6ACH NTV 5h - 4ACH NTV 5h - 5ACH C m (Wh/K.m 2 ) 0 5

6 SELECTION & VALIDATION OF THE MODEL Model used for validation (Danish BR) o Different shape o Different window-to-floor-area ratio Test with 4 different levels of thermal mass and different air change rates. 2 thermal zones N-S 2 6

7 Validation results 0% x- x- x- x- light - 3 light - 5 light - 7 light - 9 ACH ACH ACH ACH light - 3 ACH light - 5 ACH light - 7 ACH light - 9 ACH medium medium medium medium heavy ACH- 5 ACH- 7 ACH - 9 ACH 3 ACH heavy - 5 ACH heavy - 7 ACH heavy - 9 ACH Error on the heating & cooling consumption (%) 5% 0% -5% -0% -5% -20% -25% -30% Without correc. Method Method 2 Accuracy of Method 2 Þ ± 5% 3 CONCLUSION 2 methods have been developed ( and ) from 288 simulations Only one method has been selected (after the validation case): o Accuracy of ± 5 % (on the total energy consumption) o Accurate even in mono-zone modelling (robustness) o BUT not tested with other climates. C =, = h C g (-) NTV 8h - 6ACH NTV 8h - 7.5ACH NTV 2h - 5ACH NTV 2h - 6ACH NTV 5h - 4ACH NTV 5h - 5ACH C m (Wh/K.m 2 ) 4 7

8 Thank you for your attention! Jérôme LE DRÉAU PhD fellow Supervisor: Prof. Per HEISELBERG Aalborg University (DK) - Department of Civil jld@civil.aau.dk (