sustainable building façade and advanced fenestration systems€¦ · technology • low-carbon...
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Sustainable Building Façade and
Advanced Fenestration Systems
Tin-Tai ChowBuilding Energy & Environmental Technology Research Unit
Division of Building Science and TechnologyCity University of Hong Kong
(http://www6.cityu.edu.hk/bst/BEET/project_page/index.htm)
Workshop on Potential Technological Developments for Zero Carbon Buildings
16-17 Oct 2013
Low-Carbon Building (LCB)Technology• Passive solar design• Daylight utilization• Efficient ventilation and airflow strategy• High performance system equipment• Energy management and optimization• Thermal and electric load shifting• Waste water and heat recovery• Minimum transportation• Material recycling and min. embedded energy
Stratum ventilationTimber building
Light pipe
Heat exchanger
Water film windows Green roof
Zero-Carbon Building (ZCB) Technology
• Low-carbon building (LCB) technologyPLUS Renewable energy sources
e.g. active solar design, wind energy utilization, biofuel utilization, etc.
Bio-diesel Gen-set
PV/T heat pump / heat pipe
Wind turbine
Roof-mount PV panels Solar-wind power street light
Solar wall and water heaters (ZCB)• Solar chimney
• Wall embedded water piping
• Vacuum-tube water heaters
• Building facade integration for maximum power output
• Energy generation in association with reduced building thermal transmission (reduced air-conditioning load) and heat reflection (reduced UHI effect)
Double skin facade
Vacuum-tube water heaters at balcony
Chow et al. Energy and Buildings, 43(12), 2011, 3467-3474.
Chow et al. Applied Energy, 83(1), 2006, 42-54.
Chow et al. Applied Thermal Engineering, 23(16), 2003, 2035-2049.
Opaque Facade: BiPV/T (ZCB)
Payback period (years)
Stand‐alone
Building‐integrated
Economical 12.1 13.8Energy 2.8 3.8GHG 3.2 4.0
Flat-box aluminum thermal absorberInvention patent CN 1716642
Stand-alone PV/TChow TT et al. Solar Energy, 80(3), 2006, 298-306.
Building-integrated PV/TChow TT et al. Applied Energy, 86(5), 2009, 689-696.
Life Cycle Analysis
Chow TT, Ji J, Int J Photoenergy, 2012 Special issue.
Glazed BuildingsExtensively-glazed buildings are widely in use
• Positive side: transparency; natural brightness; modernity; indoor-outdoor interaction
• Negative side: weak thermal element; energy wastage; global warming
Multi-pane window glazing (LCB)• Air-sealed glazing
• Gas-filled glazing
• Vacuum glazing
• Low-e glazing [IGU]
Chow TT, Li CY, Lin Z. Solar Energy Materials & Solar Cells, 94(2), 2010, 212-220.
Ultra-violet: 300-400 nmVisible light: 400-700 nmNear infra red: 700-2500 nm
New roles of advanced window systems
Two basic principles of ZCB window design for warm climate zone to reduce room heat gain:
1. To filter out infrared spectrum, but not visible light; and
2. To utilize solar radiation as renewable energy source.
absorptive glazing
Thin film PV glazing
See-through Photovoltaic Glazing
Chow TT, Qiu ZZ, Li CY, Solar Energy Materials and Solar Cells, 93, 2009, 230-238.
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month
NV
D-P
V/C
cool
ing
load
, kW
h
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Monthly cooling load distribution for HK in 4 major directions
PV Ventilated Glazing – with power generation
PV glass
solar transmission
incident solar
radiation
indoor
thermal radiation & convection
air flow
clear glassnatural convection
thermal radiation exchange
outdoor
thermal radiation & convection
To DC load
With semi-transparent a-Si solar cells on glazing:
Advantages: energy saving through electricity generation together with reduction in air-conditioning and artificial lighting
Disadvantage: high investment costs
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month
cool
ing
load
, kW
h
S-AB S-PV NVD-PV/C
Chow TT, Qiu ZZ, Li CY, Solar Energy Materials & Solar Cells, 93, 2009, 230-238.
Predicted monthly cooling loads for 3 different glazing systems in typical open-plan office
Water-flow Windowwith enclosed loop
Lower header
Upper header
Supply to hot water system
Water-to-water heat exchanger (at window frame)
Insulated distribution tube
Feed water
Thermosyphon-induced liquid flow up the glazing to the heat exchanger at the top for hot water preheating purpose.
Solar transmission through glazing is reduced and so space cooling load is lowered.
Quality of daylight is enhanced since water affects very little visible light spectrum.
Advantages:• thermal load reduction;• daylight utilization; and • useful heat gain for hot
water supply
Chow TT, Li CY, Lin Z. Building and Environment, 46(4), 2011, 955-960.
Full-scale triple-glazed water-flow window at environmental chamber
3 components from outdoor to indoor :
one layer of clear glazing (12mm thick)
one layer of flowing water (30mm thick);
one layer of low-e double glazing (24 mm IGU);
Chow TT, Li CY. Building and Environment, 60, 2013, 44-55.
Experimental results• Water temperature increase can be > 10oC in the afternoon. • Water in window circuit kept absorbing heat from the adjacent glass
panes and the incident solar radiation during daytime. • The highest water temperature rise occurred at around 4-5pm.
Performance validation with ESP-r
Normal incident solar radiation on the window from experiment and ESP-rsimulation
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Solar
radia
tion l
avel
Solar radiation from experiment measurement (W/m2)Solar radiantion from simulation (W/m2)
Outer glazing temperature comparsion between experiment and ESP-rsimulation
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1 3 5 7 9 11 13 15 17 19 21 23Hour number
Outer surface temperature of outer glazing-experimentOuter surface temperature of outer glazing-simultion
Inner glazing temperature comparsion between experiment and ESP-rsimulation
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Inner surface temperature of outer glazing-experimentInner surface temperature of outer glazing-simulation
Double clear glazing with reflective coating at inner glass pane
Chow TT, Li CY, Clarke JA, BS2011, IBPSA Conference, Sydney
Water-flow window performance with application in DHW of Sports Center
• 6 rows of water-flow windows on inclined roof
• Each 29.6m x 1.4m (clear glass with reflective coating)
• DHW demand in line with room opening hours: 7am - 10pm
• Occupant, equipment and lighting operating schedules from Performance-based Building Energy Code Guidelines
• Indoor temperature: 20oC during winter and 24oC during summer
• Feed water temperature same as ambient air temperature; feed rate by gravity or mechanical device.
Year round performance
Water tempeature at the inlet and outlet of the window zone in typical winter week
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1 13 25 37 49 61 73 85 97 109 121 133 145 157
Hour of typical winter week
Wat
er te
mpe
ratu
re
Ambient temeprature (oC) Water flowing rate at 0.05kg/s (oC)Water flowing rate at 0.1kg/s (oC) Water flowing rate at 0.15kg/s (oC)Water flowing rate at 0.2kg/s (oC) Water flowing rate at 0.4kg/s (oC)
Water tempeature at the inlet and outlet of the window zone in typical summerweek
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1 13 25 37 49 61 73 85 97 109 121 133 145 157
Hour of typical summer week
Wat
er te
mpe
ratu
re
Ambient temeprature (oC) Water flowing rate at 0.05kg/s (oC)Water flowing rate at 0.1kg/s (oC) Water flowing rate at 0.15kg/s (oC)Water flowing rate at 0.2kg/s (oC) Water flowing rate at 0.4kg/s (oC)
Typical summer week
Typical winter week
For a range of feed water flow rates, the year-round space cooling load can be reduced from 22% to 35%.
Within a typical year, more than 20% of the total incident solar energy can be utilized by the DHW system.
PV/T water-flow window• With PV glass pane as the outer pane
– sc-Si cells laminated between two 6mm clear glazing – 15% electricity generation efficiency at STC – 88% packing factor
• 30mm water flow cavity
• 12mm clear glass pane as the inner pane
Month
Indoor heat gain through PV/T
water-flow window
System thermal
efficiency
System electrical efficiency
System integrated efficiency
(% transmitted) (%) (%) (%) Jan 6.7 14.7 13.12 49.3 Feb 3.8 13.9 13.15 48.5
Mar 9.7 11.1 13.16 45.7
Apr 21.8 6.7 13.15 41.3
May 21.1 8.1 13.14 42.6
Jun 25.8 5.8 13.14 40.4 Jul 26.3 5.7 13.13 40.2
Aug 25.2 6.3 13.13 40.9
Sep 22.4 6.5 13.12 41.0 Oct 19.2 9.4 13.10 43.9
Nov 11.1 12.4 13.12 47.0
Dec 10.9 13.5 13.13 48.0 Overall 16.4 9.9 13.13 44.5
Monthly energy performance
Conclusion• Zero carbon building design calls for new roles of
opaque facade and window systems
• Innovative facades can utilize large amount of solar energy without occupying extra space
• A range of practical solutions and products are available that carry both passive / active roles
• Water-flow window for example is able to absorb solar heat and reduce indoor heat gain, and so to save AC and DHW electricity consumption without disturbing the indoor visual environment
• More R&D works are in need for new initiatives and full utilization
Thank you