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Buildings and construction together account for global energy use of 36%. Thermal properties of building facade have significant impact on the cooling and heating loads as well as the lighting loads. Facade, accounts for almost 50% of the thermal loads in buildings in the tropics. This project experimentally investigates the performance and operational characteristics of a set of green building technologies, namely LED and auto-dimming lighting, active chilled beam (ACB) air-conditioning, automated daylight redirecting shading and Electrochromic glazing (EC) under the tropical climate conditions of Singapore. This set of green building technologies cover major energy consumptions (lighting, air-conditioning and heat gain through façade) in tropical buildings. Experiments are conducted in the BCA SkyLab testing facility which allows side-by-side comparisons and investigation of orientation effects of these technologies. The study focuses on revealing the energy, visual and thermal comfort performances as well as the dynamic responses to weather conditions of these technologies when they are deployed individually and in combinations.

Results show that more benefits can be obtained by deploying a combination of the tested technologies in terms of annual energy savings as well as thermal and visual comfort, as compared to deploying the technologies individually. The combined technologies showed about 35% energy savings in North orientation, 33% in East orientation, 28% in West orientation and 29% in South orientation. These savings are derived from using auto-dimming technology in conjunction with LED lighting, lower supply airflow rate of the ACB and daylight re-direction capability of the automated blinds (combined system with automated blinds) or tinting for the EC glazing (combined system with EC glazing). The conventional reference system consisting of Low-e double-glazing unit (DGU), manual blinds, conventional FCU system and T5 fluorescent lamps. Both the automated blinds system and the EC glazing can provide thermal and visual comfort with unobstructed view when compared to a typical building using a Low-e DGU and manual blinds system. The ACB system can provide better thermal environment with its lower air discharge rate characteristics, as compared to the traditional FCU system. However, the energy savings and thermal comfort potentials of ACB deteriorates as room heat load increases to over 112 W/m².

The findings of this project will provide support to the decision making in adopting these technologies by providing quantitative information on their true performance and operational characteristics in the context of Singapore. The project also provides indications on how much the building energy-efficiency performance envelop can be push further by adoption of new technologies. The information serves as foundation for the development of policy and road mapping framework of next generation super high-performance buildings and sustainable built environment.

Lighting, Auto-dimming and Automated blinds test:

As shown in Figure 3, compared to the common reference system consisting of non-dimmable T5 fluorescent lamps without window blinds, adding auto-dimming function showed about 46% savings in lighting energy consumption, switching to LED lamps provided about 24% of lighting energy savings, LED lamps combined with auto-dimming showed around 80% energy savings for North orientation. Without window blinds, visual comfort was frequently compromised in terms of high working plane level illuminance and glare experienced by the occupants. Compared to the same reference, an integrated system consisting of LED lamps, auto-dimming lighting control and automated blinds achieves up to 75% of lighting energy savings for North orientation. The North orientation had higher daylight savings potential due to higher daylighting potential throughout the day compared to the East orientation, which saved 63% lighting energy instead. The lighting energy savings potential is higher for clearer sky conditions due to higher daylighting potential. In Singapore’s tropical climate, the integrated system shows excellent capability to provide visual comfort while achieving significant lighting energy savings. Performance evaluation of the technologies in terms of its impacts on cooling energy and total building energy consumption were also performed through computational simulation study. The simulation results are consistent with the experimental measurements finding at BCA SkyLab.

Active chilled beam test:

As shown in Figure 4, compared to the common reference system consisting of conventional FCU system, showed about 21% savings in North orientation, 19% in East orientation, 20% in West orientation and 23% in South orientation. The reduction in energy consumption is due to savings in fan energy due to low supply air flow rate. There is also potential in reducing chiller side energy consumption due to the requirements of high temperature chilled water, which may result in decrease of total building energy consumption. The savings potential diminishes as the total heat density room increases to 130 W/sqm. It can be concluded that both conventional FCU and ACB system have accomplished the required comfort criteria as per ISO 7730. ACB system can produce satisfactory thermal environment inside any building, with low air discharge compared to traditional air conditioning (here, it is Conventional FCU) system and sometimes provide even better thermal environment. However, ACB system is not recommended when the total cooling load density is high (112 W/sqm) as the ADPI will drop below the ASHRAE recommended acceptable range (80%) and occupant closer to window will feel more discomfort as opposed to conventional FCU system.

Electrochromic glass test:

When compared to DGU (SHGC 0.27, VLT 59%), the EC glazing’s VLT is 63% and the SHGC is 0.44 (0% tint); thus though there is a daylight benefit, heat reduction is not maximum. Similarly, when SHGC is controlled up to 0.06 (100% tint), VLT drastically reduces to 2.1% and there is no benefit of daylight despite there is a significant reduction in the heat gain and improvement in energy savings. As shown in Figure 5,during the testing period, the west and north orientation showed measured energy savings up to 4%. West orientation had higher cooling energy savings than the north orientation due to the tinting control of EC glazing facade, which helped to reduce the transmission heat from the low angle sun during afternoon. This also led to lower lighting energy savings from the auto dimming system in the west orientation. Simulations were conducted to further compare the performances of EC glazing to DGU in a realistic office building setting. The results showed that EC glazing provided annual energy savings of up to 7.2% compared to DGU, under the weather conditions of Singapore. In case of thermal comfort, EC glazing provided a better thermal environment falling in category A for PMV. This study shows that EC glazing facades could effectively utilise daylighting and reduce heat gain to provide energy benefits without compromising on visual and thermal comfort. EC glazing facade could also maintain good visual comfort (DGP below 0.35) without the need for internal shades, which is beneficial for good exterior visual connectivity. The results of this study provide performance evaluation data of EC glazing in tropical environment to support decision making for industry adoption.

Combination test:

Compared to the combined conventional reference system consisting of Low E DGU, Manual blinds, conventional FCU system and T5 fluorescent lamps, advanced technologies showed about 35% savings in North orientation, 33% in East orientation, 28% in West orientation and 29% in South orientation. These savings are from using auto-dimming technology in conjunction with LED lighting, lower supply air flowrate of the ACB and daylight re-direction capability of the automated blinds (combined system with automated blinds) or tinting for the EC glazing (combined system with EC glazing) as shown in Figures 6 and 7. Good visual comfort was maintained at all times by the combined system with Automated blinds and >90% of the time by combined system with Electrochromic glazing. DGP was kept below 0.35 and working plane illuminance was maintained between the recommended 500 to 3000 lux. Both the automated blinds system and the EC glazing can provide both thermal and visual comfort with unobstructed view when compared to a typical building using a Low e DGU and blinds system. Conventional FCU and ACB system have accomplished the required comfort criteria as per ISO 7730. ACB system can produce satisfactory thermal environment, with low air discharge compared to traditional air conditioning system and sometimes provide even better thermal environment.