Improving Thermal Comfort & Reducing Energy Consumption in Naturally Ventilated University Buildings

Transcription

1 Australasian Campuses Towards Sustainability 26 th -28 th September 2012: Brisbane, Australia Improving Thermal Comfort & Reducing Energy Consumption in Naturally Ventilated University Buildings Laia Ledo, Zhenjun Ma, Paul Cooper Sustainable Building Research Centre, University of Wollongong, New South Wales, Australia

2 Agenda Background Objectives Methodology Results Conclusions

3 Background Australia s green house gas (GHG) emissions per capita are amongst the highest in the world (third highest emitter). Almost a quarter of Australian GHG emissions are from the built environment. There is an urgent need to take action against climate change. The climate change impacts are irreversible but the risks can be reduced by embracing adaptation and mitigation.

4 Background Studies (CIE, 2007) suggest that Australian building sector could reduce its energy consumption between 20 and 40% by implementing energy efficiency measures Source: Centre for International Economics, CIE, 2007

5 Background 30% reduction of GHG emissions can be achieve by 2020 against the 2004 baseline (IPCC, 2007). Less optimistic studies predict a similar reduction (30-35 %) although over a longer time span by 2050 (CIE, 2007).

6 Background buildings accounts for ~ 23% of Australian GHG emissions poor building performance (IEQ, energy) WHY? annually, just % of the existing building stock are new buildings building stock constructed without sustainability awareness Energy efficiency needs involvement of all the economy sectors Educational buildings unique opportunity to influence society

7 Indoor Environmental Quality Describe the conditions that determines how we feel in a space. Indoor environmental quality can be divided in : Air quality, visual, acoustic and thermal comfort. A review (Frontczak and Wargocki, 2011) ranked the importance of the IEQ factors and it was found that thermal comfort is the most important factor affecting the occupants.

8 Thermal Comfort Where there is broad satisfaction with the thermal environment (CIBSE, 2007) Feeling hot or cold responding to the transfer of heat from people s body to the surroundings, and to the quality of the air within the space.

9 Thermal Comfort Operative Temperature combines the effect of Air Temperature and Radiant Temperature.

10 Thermal Comfort Fanger (1970) Conducted confined chamber experiments that conditions in mind that expresses satisfaction with the environment (ASHRAE Standard 55, 1992) Source: ASHRAE Standard 55, 1992

11 Adaptive Thermal Comfort ASHRAE RP 884 Adaptive model project When a change occurs causing thermal discomfort, people react in such a way that their thermal comfort is re-established, Auliciems. Source: Prof. Richard de Dear, Sydney, 2011

12 Adaptive Thermal Comfort ASHRAE, Standard 55, 2004 EN 15251, 2007

13 Retrofits options Retrofits can be divided according to potential savings, financial risk and overall impact on the building performance: Standard retrofits: low financial risk, 15-30% energy reduction. Deep retrofits: high financial risk, over 50% energy savings.

14 Modelling Modelling can be used to: Assess the effect of each retrofit measure in the overall building performance Assist to make informed decisions about the uptake of an upgrade

15 Aim Investigate a variety of retrofits options that could potentially improve the thermal comfort and reduce the energy consumption: University of Wollongong recent increase in the overheating complaints. To address the overheating complaints, UOW Facilities Management (FM) is in the process of retrofitting air conditioning potentially a major increase in energy consumption. Modelling carried out to determine whether occupant behaviour and/or energy efficiency measures could result in improvements to avoid HVAC.

16 Case Study Building Characteristics : Constructed in the mid sixties Two level brick with a flat metal deck roof External shading on windows on the north facing side Layout of the building space: highly partitioned Approximately 15% of the total building area is air conditioned

17 Case Study Breakdown of total energy use by application for the case study Building. Average Energy consumed per annum: 446 MJ/m 2

18 Case Study Façade:

19 Case Study Ceiling:

20 Case Study Typical office room:

21 Case Study

22 Case Study DesignBuilder sketch of the ground floor geometry for Building 4

23 Methodology

24 Methodology Measures implementation details:

25 Methodology Computers and lighting loads:

26 Methodology Simulation Output:

27 Experimental vs Simulation Occupants and internal loads Natural Ventilation Air tightness Input weather data file Uncertainities

28 Results

29 Results Predicted temperatures and ASHRAE comfort zones for ground floor room during occupied hours.

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31 Results Heaters in use

32 Conclusions The proposed retrofits potentially could greatly benefit the thermal comfort and the energy consumption in climates similar to Sydney/ Wollongong. Simulations show that internal loads play a major role in overheating hours thermal comfort energy consumption Relatively simple behaviour change measures could avoid need for HVAC: Education and motivation of occupants (optimal use of windows, switch off lights and computers, night purge, etc) Upgrade lighting and IT, then improve envelope

33 Surveys Please help my research Step 1: Respond to the Survey By knowing your behaviour as building user and the way your institution addresses sustainability and thermal comfort we will gain insight into implementing retrofit strategies to universities. Step2: Have a chat with me about the current practices from your institution.

34 Acknowledgments Thanks to: Mr. Craig McLauchlan Dr. Phil Fletje