Application of Green Façade as Passive Cooling Technique for Energy Efficiency

Transcription

1 Application of Green Façade as Passive Cooling Technique for Energy Efficiency Mohd Khairul Azhar bin Mat Sulaiman Architecture Department, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia. Institute Applied Climatology & Landscape Ecology, Faculty of Biology, University of Duisburg-Essen, Essen, Germany. 1

2 Contents Introduction Objectives Methodology Findings Conclusion 2

3 Introduction Building Energy Efficiency can be improved by implementing Active Energy Efficient strategies Heating, Ventilation & Air-conditioning (HVAC) systems, electrical lighting Passive Energy Efficient strategies Building envelope insulation, material, shading devices, green roof, green facade Singapore (Wong et al, 2009) External shading - 100% coverage of Green Façade Reduced space cooling load : 17.93% Greece (Balaras C.A. et al, 2000) External shading ;i.e. awning and light-coloured roof & external wall Reduced space cooling load : 30% Hong Kong (Cheung, C.K. et al., 2005) External insulation - Extruded polystyrene (EPS) Energy saving : 31.4% Peak load saving : 36.8% 3

4 Issue Government of Malaysia has announced, which ordered government offices to set an air-conditioning temperature no lower than 24 Celsius for optimum indoor thermal comfort and energy saving step. According to Ministry of Energy, Green Technology and Water, by lowering one degree (23 C) on airconditioning thermostat, overall expenditure will increase from 4 to 7 per cent annually BERNAMA, Malaysia National News Agency, reported on 11 August 2011 Thus, this study is investigating on application of green façade as passive cooling technique for energy saving step on cooling period of office building. 4

5 Overview of Vertical Greenery Systems Direct Green Facade Indirect Green Façade Indirect Green Façade Trellis/ Wiremesh Cable & rod Indirect Green Façade Perimeter flowerpot Living wall - Panel Living wall Geotextile felt 5

6 Green façade (GF) is a vertical manner planting system rooted in the ground or planter pot, using supporting structure such as modular trellis, wire mesh or cable for climbing plants in screening exterior surface of building façade. As passive cooling technique in providing conducive indoor thermal environment and energy efficiency, GF acts as external shield offer shades to the building facade avoiding undesirable excessive radiation and reducing heat flux transfer through exterior surface (Chen, Li, and Liu 2013, Jim and He 2011). transmitted radiation cooling load cooling load solar radiation solar radiation indoor outdoor indoor outdoor conventional wall Green Facade 6

7 However, a key factor to successful outcomes is depending on vegetation used in the system (Wong N.H. et al, 2003; Perez et al, 2009; Hodo-Abalo, S. et al, 2012, Fang C.F., 2008). Thus, a carefully decision on plant selection to be used is a crucial step to be taken for optimization on performance of the system. Furthermore, this step need to be engaged is to avoid frustration on the expectation of effectiveness of these systems as passive cooling technique. This study aimed to investigate performance of selected tropical climbing plants used on GF for energy efficiency on cooling load for office building. Selected tropical climbers used for this study are Thunbergia grandiflora and Argyreia nervosa. Research Objective To investigate on energy saving of space cooling load for building attached with Green Façade (GF) at eastern and western orientation walls using selected tropical climbers; Thunbergia grandiflora and Argyreia nervosa. 7

8 Research Methodology 8

9 Findings 1st experiment : 8 th June 2013 Thunbergia grandiflora VS Control. On sunny day, from hr. Ave. ambient temperature : 31.7 C Ave. solar radiation : 324.9W/m² Leaf area index (LAI) : 4.14 (east) and 4.08 (west) Leaf size: 15cm (medium) Energy savings: 17.2% per day Peak load savings: 25.0% Energy rate savings: RM0.24/day 9

10 Findings 2nd experiment : 04 th August 2013 Argyreia nervosa VS Control. On sunny day, from hr. Ave. ambient temperature : 33.1 C Ave. solar radiation : 527.0W/m² Leaf area index (LAI) : 3.72 (east) and 3.84 (west) Leaf size: Ave. 25cm (large) Energy savings: 15.2% per day Peak load savings: 34.2% Energy rate savings: RM0.22/day 10

11 Findings Temperatures of the interior wall surface and indoor air are important parameters to evaluate the indoor thermal environment. Indoor surface temperature on east and west orientation walls of test cell with GF has a smaller temperature fluctuation comparing to control cell walls. Similar results were demonstrated on indoor air temperature fluctuation. It can be seen that the GF has a promising effect on stabilizing the indoor environment when the air conditioner is on. Consequently, it helps in reducing energy consumption for cooling loads. Thunbergia grandiflora Argyreia nervosa 11

12 Findings Thunbergia grandiflora VS Control. Thunberg ia sp. (Kwatt) Control (KWatt) Indoor Indoor Thunberg Control ia sp. ( C) ( C) mean max min stdev

13 Findings Thunbergia grandiflora VS Control. Thunberg ia sp. (Kwatt) Control (Kwatt) Thunberg ia sp. Control East In East In ( C) ( C) Thunberg ia sp. Control West In West In ( C) ( C) mean max min stdev

14 Findings Argyreia nervosa VS Control. Argyreia sp. (Kwatt) Control (Kwatt) Argyreia sp.( C) Control ( C) mean max min stdev

15 Findings Argyreia nervosa VS Control. Argyreia sp. (Kwatt) Control (Kwatt) Argyreia sp. East In ( C) Control East In ( C) Argyreia sp. West In ( C) Control West In ( C) mean max min stdev

16 Findings Previous results are indicated TG and AN were performed significantly for building energy efficiency. Both of climbers on GF were demonstrated able to reduce energy demand for cooling period. Next experiment was conducted to identify which climbers on GF is performed effectively in reducing energy consumption for cooling load within the same weather condition. 3rd experiment : 28 th August 2013 Thungergia grandiflora VS Argyreia nervosa On sunny day, from hr. Ave. ambient temperature : 30.1 C Ave. solar radiation : 328.0W/m² Ave. Leaf area index (LAI) : 4.11 (TG) and 3.78 (AN) 16

17 Findings Results indicated both GFs were performed almost similar for building energy efficiency even though both climbers having a different LAI (TG; ave. LAI : 4.11 and AN; ave. LAI: 3.78). This is assumed of leaf size of AN (ave. 25cm) which can provides large area leaf surface coverage. However, TG was identified as most suitable climber for energy efficiency compared to AN due to higher energy saving. Energy savings of TG vs AN: TG save 5.2% per day than AN Peak load savings of TG vs AN : TG save 15.4% than AN Energy rate savings TG vs AN : TG save RM0.03/day rate than AN 17

18 Conclusion GF has a promising effect on building energy efficiency as passive technique for cooling effect through shading on building envelope. GF is stabilizing the indoor environment when the air conditioner is on. Consequently, it helps in reducing energy consumption for cooling loads. Effectiveness of GF may perform significantly with suitable selection of climber on GF. In comparison to Thunbergia grandiflora and Argyreia nervosa, it was identified that TG is more suitable in providing benefit towards energy efficiency. 18

19 Thank you 19