Design and Energy Performance of a Buoyancy Driven Exterior Shading Device for Building Application in Taiwan
Abstract
:1. Introduction
2. Design Consideration
- (1)
- The application must be realistic and practical.
- (2)
- All details must be improved, especially the design process and generation.
- (3)
- The design may be extensively used.
- (4)
- It must also possess the function of home security.
- (5)
- It must include all facts relevant to product maintenance.
- (6)
- The concepts may be improved in the future.
3. Methodology
3.1. Materials Selection
Diagram | ||
---|---|---|
Position | Designation | Description |
A | External frame | Aluminum alloy, offer frame stability and security function |
B | Interior frame | Aluminum alloy, offer frame stability and security function |
C | Drive lever | Acrylic-plastic, move upward along with the uplifting level of liquid surface inside the compartment |
D | Link | Acrylic-plastic, one end connected to the drive lever and the other, to the pivot |
E | Panel | Acrylic-plastic, offer sun-shielding and daylight function |
F | Pivot | Aluminum alloy, drive the panel to turn toward the intended direction and offer security function |
G | Liquid supply hole | Rubber material, introduce liquid into the system |
H | Upper chamber | Propose using liquid, provide the liquid volume required to turn the sun shading panel just for 60° |
I | Liquid compartment | Connect to upper and lower chambers |
J | Floating board | Expandable-polystyrene, offer the upward force and make drive lever rise, super-hydrophobic and high porosity |
K | Lower chamber | Install floating board and make it move upward along with the uplifting level of liquid surface |
L | Liquid level controller | Control the suitable time and pumping volume of motor |
M | Maintenance section | Battery Replacement and motor maintenance |
N | On-off switch | Set the operation time and the start switch |
O | Motor | Convey the liquid of lower chamber to the upper one |
3.2. Functional and Structural Design
3.3. Detail Design
4. Impact on Indoor Environment
4.1. Simulation Tools
4.2. Description of the Design of a Typical Office Simulation Model
Item | Description |
---|---|
Space geometry | Width = 6.0 m; Depth = 5.0 m; Ceiling height = 3.0 m; with one 6.0 m exterior exposed wall |
Exterior wall construction | Construction from outside layer to inside layer: 30 mm marble, 30 mm mortar, 150 mm reinforced concrete, 10 mm cement fiber board; equivalent to U-value = 2.76 W/(m2K) |
Windows | Window-to-wall ratio = 80%; Window width = 6.0 m; Window height = 2.4 m |
Window glass | 6 mm Clear glass; U-value = 5.78 W/(m2K); SHGC 1 = 0.82 |
Blinds | Thickness = 0.25 mm; Blind slat width = 300 mm; Slat separation distance = 300 mm; Conductivity = 211 W/(mK); Slat surface reflectance = 0.7 |
Blind rotation mechanism | East: 0° (horizontal) to 60° from 06:00 to 12:00 and is fixed at 0° for the other hours. West: 0° (horizontal) to 60° from 12:00 to 18:00 and is fixed at 0° for the other hours. North and South: All day fixed at 0°. |
Internal heat gain | Occupancy density = 0.2 person/m2; Lighting density = 15W/m2; Appliances power density = 10 W/m2; Weekday’s occupied hours = 08:00–17:00 |
HVAC system | VAV system with chiller capacity of 3.93 kW, Nominal COP = 6.5; Economizer = none; Cooling setpoint = 24 °C (winter) & 28 °C (summer); Outside air flow rate = 9.4 L/s per person; Cooling hours: 08:00–17:00 |
4.3. Impact on Energy Performance Results
4.4. Impact on Indoor Thermal Comfort Results
4.5. Effectiveness of the Blind System with Various Thermal Properties of Glazing
Location | Comparison Items | Reduction Ratio of the Proposed Blind As Compared to the Case Without Blind | Reduction Ratio of the Proposed Blind As Compared to Traditional Fixed Blind | |
---|---|---|---|---|
Taipei *1 | Overheating | frequency, ξ (h) | 24.5% | 5.7% |
severity, I (K·h) | 31.1% | 7.5% | ||
Overcooling | frequency, ξ (h) | 55.3% *3 | 10.5% *3 | |
severity, I (K·h) | 53.1% *3 | 9.6% *3 | ||
Sensible cooling energy (kWh) | 27.9% | 5.8% | ||
Orientation sensitivity order for energy saving | SE > E > SW > W > S > NE > NW > N | |||
Kaohsiung *2 | Overheating | frequency, ξ (h) | 11.9% | 3.5% |
severity, I (K·h) | 25.4% | 7.9% | ||
Overcooling | frequency, ξ (h) | N/A *4 | N/A *4 | |
severity, I (K·h) | N/A *4 | N/A *4 | ||
Sensible cooling energy (kWh) | 32.8% | 8.2% | ||
Orientation sensitivity order for energy saving | SW > SE > W > E > S > NW > NE > N |
SHGC | U-Value | |||||
---|---|---|---|---|---|---|
5.78 (W/m2) | 4.4 (W/m2) | |||||
Overheating Frequency | Overheating Severity | Cooling Energy | Overheating Frequency | Overheating Severity | Cooling Energy | |
0.82 | 24.5% (−) | 31.1% (−) | 27.9% (−) | 21.6% (−2.9%) | 29.6% (−1.5%) | 29.4% (+1.5%) |
0.5 | 22.6% (−1.9%) | 27.6% (−3.5%) | 20.8% (−7.1%) | 24.6% (+0.1%) | 30.0% (−1.1%) | 23.1% (−4.8%) |
4.6. Daylighting Performance Analysis
Orientation | UDI100-2000 lux | DGI > 24 | ||||
---|---|---|---|---|---|---|
No Blind | Fixed Blind | Proposed Blind | No Blind | Fixed Blind | Proposed Blind | |
N | 67.8% | 80.9% | 80.9% | 53.3% | 0.0% | 0.0% |
E | 61.2% | 77.9% | 77.9% | 58.9% | 19.9% | 19.6% |
S | 53.0% | 76.7% | 76.7% | 59.3% | 8.3% | 8.3% |
W | 55.7% | 76.9% | 77.1% | 56.3% | 11.0% | 10.5% |
- Daylight glare index (DGI) was adopted to analyze the glare problem to address the visual comfort issue. The calculation of DGI is as Equation (6). Jakubiec and Reinhart suggested four levels of the degree of perceived glare and considered it intolerable when DGI > 31 and imperceptible when DGI < 18 [35]. Figure 15 illustrates the annual temporal distribution of the DGI categorized according to the four levels of a west facing space. From Figure 15 and Table 5, the blind system, either fixed or the proposed one, are capable of efficiently alleviating the glare problem and enhancing the visual comfort, regardless of orientation.
5. Conclusions
- (1)
- In this paper the design considerations, design concept, and detailed design of the automatic buoyancy-shading device for building applications was presented. The choice of materials for the design creates the extra function, as discussed in above sections. The automatic shading device is unique in its driving and control mechanisms, it can be easily used and set up on typical windows in Taiwan.
- (2)
- Controllers for the panel positioning are often very complex and confusing. However, our design seems to satisfy user preferences and is convenient to use.
- (3)
- It is possible to improve user expectations and replace conventional shading devices with simplified and effective designs.
- (4)
- The effectiveness of the blind system was evaluated with regard to the improvement of indoor thermal comfort and the cooling energy saving. The results revealed that there was a 24.5% and 11.9% reduction in the occurrence of overheating when using the automated blind for the SW case in Taipei and Kaohsiung, respectively. The overheating severity alleviated by the blinds could also reach 31.1% and 25.4%, suggesting that blinds are a promising method for improving indoor thermal comfort.
- (5)
- The cooling energy saving potential was 27.9% and 32.8% for Taipei and Kaohsiung, respectively. This reveals that in a centrally air-conditioned space, there is efficient energy saving potential.
- (6)
- The cooling energy saving effectiveness of the blind system would decrease with the improvement of glazing’s solar radiation blocking ability (i.e., SHGC), but would increase with the improved glazing insulation property (i.e., U-value).
- (7)
- The proposed blind system is capable of both improving the usage of daylighting and also reducing the glare problem.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Huang, K.-T.; Liu, K.F.-R.; Liang, H.-H. Design and Energy Performance of a Buoyancy Driven Exterior Shading Device for Building Application in Taiwan. Energies 2015, 8, 2358-2380. https://doi.org/10.3390/en8042358
Huang K-T, Liu KF-R, Liang H-H. Design and Energy Performance of a Buoyancy Driven Exterior Shading Device for Building Application in Taiwan. Energies. 2015; 8(4):2358-2380. https://doi.org/10.3390/en8042358
Chicago/Turabian StyleHuang, Kuo-Tsang, Kevin Fong-Rey Liu, and Han-Hsi Liang. 2015. "Design and Energy Performance of a Buoyancy Driven Exterior Shading Device for Building Application in Taiwan" Energies 8, no. 4: 2358-2380. https://doi.org/10.3390/en8042358