An Investigation of the Energy-Saving Optimization Design of the Enclosure Structure in High-Altitude Office Buildings
Abstract
:1. Introduction
1.1. Background of the Study
1.2. Review of Chinese and International Literature
2. Materials and Methods
2.1. Overview of the Study Area
2.1.1. Geographic Location and Climatic Characteristics of Lhasa City
2.1.2. Characteristics of the Current Situation of Office Buildings in Lhasa City
2.2. Research Framework
2.3. Objects for Energy-Saving Optimization and Renovation
2.4. Data Collection
2.4.1. Questionnaires
2.4.2. Field Measurements
Field Measurement Program
Layout of Measurement Points
Testing Instruments
2.5. Indoor Thermal Comfort Evaluation Indicators
3. Results
3.1. Analysis of Indoor Thermal Comfort of Office Buildings in Lhasa City
3.2. Thermal Neutral Temperature
3.3. Analysis of the Indoor Thermal Environment of the Renovation Object
3.4. Enclosure Optimization and Simulation Verification Analysis
3.4.1. Optimization Objectives and Optimization Scheme
Selection of Optimization Measures
Enclosure Optimization Scheme
3.4.2. Validation Modeling
3.4.3. Simulation Software Validation
- (1)
- The daily trends of measured and simulated values over the test period are plotted, and the correlation between the two is studied.
- (2)
- The absolute and relative errors between the measured and simulated values of the measurement points were calculated. The root mean square error (RMSE) and consistency index (d) [45] were introduced to quantitatively evaluate the absolute and relative errors of the numerical simulation during the test period. The formulas for calculating the RMSE and d values are shown in Equations (5) and (6):
3.5. Comparison of Results before and after Optimization
3.5.1. Analysis of Thermal Environment Parameters
3.5.2. Indoor Thermal Comfort Analysis
4. Discussion
5. Conclusions
- (1)
- The heating system type of established old office buildings in Lhasa is mainly passive, and the passive type systems are categorized into the direct beneficiary type, thermal collector wall type, and additional sunroom type, unlike in other cities in cold climate zones.
- (2)
- The measured and predicted thermal neutral temperatures in Lhasa are 16.5 °C and 18.9 °C, respectively, with a 90% acceptable temperature range of 16.10 °C to 21.77 °C, so the population of the office building occupants in Lhasa has a higher tolerance for cold than predicted.
- (3)
- Passive measures adapted to the Lhasa area are prioritized as follows: passive solar energy, high heat capacity materials, and night ventilation.
- (4)
- Optimizing the envelope of existing office buildings, enhancing the heat storage capacity of the external envelope, and increasing the window area’s natural ventilation can effectively improve the indoor thermal comfort of the renovated building.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
Appendix A
- Questionnaire on Indoor Thermal Comfort for Office Workers in Winter
- Basic information:
- Gender:__________ Age:__________ Height (cm):__________ Weight (kg):__________
- How many years have you lived in Xizang:__________
- 2.
- Current dressing situation:
- 3.
- Your activity status during the 30 min prior to the survey (single choice):
- 4.
- Are you taking steps to cool or warm your room at this time (multiple choice)?
- 5.
- Your heat sensation at this time is (single choice):
- 6.
- Your thermal comfort at this time (single choice):
- 7.
- Your acceptance of indoor hot and cold environments (single choice):
- 8.
- How would you like to see the parameters of the indoor thermal environment improved at this time (multiple choice)?
- 9.
- What would you use to enhance thermal comfort (multiple choice)?
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Typical Buildings | Heating System | Physical Characteristics | Heat Collection Methods and Heat Utilization Processes | Specifications |
---|---|---|---|---|
A | Direct beneficial type | 15 years; 5 floors; white exterior finish; building area of approximately 18,120.49 m2 | Large south-facing glass windows capture direct solar radiation and utilize furniture and floors to absorb stored heat. | Fast cooling at night and indoor temperature fluctuations; simple construction, construction, management, and maintenance are convenient. |
B | Active type of heating | 15 years; 5 floors; gray exterior; building area approximately 18,120.49 m2 | Converting solar energy into electricity to provide power for the building; utilizing the collector system to provide domestic hot water, heating, or cooling. | The heating effect is good, the temperature is stable, and the scope of application is wider. |
C | Thermal storage wall | 13 years; 7 floors; gray exterior finish; building area approximately 19,227.15 m2 | The heat storage wall is covered with glass, leaving an air layer in the middle, with an air inlet and outlet at the bottom and top of the wall for convection circulation, and the vents are closed at night to stop the work. | The indoor temperature can be automatically adjusted according to the opening and closing of the air outlet, the construction is more complicated than the direct beneficiary type, and the warming is slow. |
D | Additional sunroom | 13 years; 4 floors; light yellow exterior finish; building area approximately 2777.38 m2 | The south room is buffered by enclosing the space with transparent material to store heat and raise the room temperature during the day and insulated curtains to separate the sunroom from the main room at night to stop heat loss. | The amount of material has a high cost, the temperature difference between day and night is large, summer daytime is too hot, and the sun can be combined with green plants to increase indoor humidity, as well as buffer the indoor cold air in the room. |
Type of Enclosure | Tectonic Resistance Measures |
---|---|
External wall | 20 mm cement mortar + 370 mm heavy mortar clay + 20 mm lime mortar |
Interior wall | 20 mm cement mortar + 180 mm crushed stone, pebble concrete + 20 mm cement mortar |
Roofing | 20 mm cement mortar + 200 mm aerated concrete + 130 mm reinforced concrete + 15 mm cement mortar |
Floor | 20 mm cement mortar + 100 mm reinforced concrete + 20 mm cement mortar + gypsum board ceiling |
Ground level | 100 mm plain concrete + 20 mm paste layer + 30 mm terrazzo flooring |
External window | Glass curtain wall, 10 mm ordinary single-layer glass |
Type of Enclosure | Heat Transfer Coefficient (W/m2·K) | Heat Transfer Coefficient Limits (W/m2·K) | Exceeded Limits (%) |
---|---|---|---|
Facade/Glass Curtain Wall | 1.97 | 0.6/0.55 | 328%/358% |
Roofing | 0.98 | 0.45 | 211% |
External window | 3.1 | 2.0 | 155% |
Clothing | Thermal Resistance Value (clo) | Clothing | Thermal Resistance Value (clo) | Clothing | Thermal Resistance Value (clo) |
---|---|---|---|---|---|
Light jacket | 0.20 | Thin outer pants | 0.15 | Leather shoes | 0.02 |
Heavy jacket | 0.50 | Woolen pants | 0.24 | Galoshes | 0.05 |
Woolen knitwear | 0.25 | Long underwear pants | 0.15 | Sneakers | 0.03 |
Thick sweater | 0.36 | Long-sleeved underwear | 0.20 | Thick skirts | 0.23 |
Long-sleeved T-shirt | 0.08 | stocking | 0.02 | Thick outer pants | 0.24 |
Instrument | Measurement Parameters | Measurement Range | Instrument Accuracy | Instrument Photos | Manufacturer and Location |
---|---|---|---|---|---|
GSP-958 Recorder | Room temperature/relative humidity | −20–60 °C/ 0–99.9%RH | ±0.5 °C/±3% RH | Lexiang Electronic Technology Co., Ltd., Guangzhou, China | |
JTR04 Black Globe Temperature Tester | Black globe temperature | −20–125 °C | Ambient temperature ±0.2 °C | Yichang Industrial Co., Ltd., Shanghai, China | |
WFWZY-1 Universal Wind Speed and Temperature Recorder | Indoor wind speed | 0.05–30 m/s | ± 0.05 m/s | Tianjian Huayi Technology Development Co., Ltd., Beijing, China |
Level | Evaluation Indicators | |
---|---|---|
I | PPD ≤ 10% | −0.5 ≤ PMV ≤ +0.5 |
II | 10 ≤ PPD ≤ 25% | −1 ≤ PMV ≤ −0.5 or +0.5 ≤ PMV ≤ +1 |
III | PPD ≥ 25% | PMV < −1 or PMV > +1 |
A | B | C | D | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
PMV | PPD | Rank | PMV | PPD | Rank | PMV | PPD | Rank | PMV | PPD | Rank | |
10:00 | −0.8 | 15.52% | II | −1.3 | 44.52% | III | 0.9 | 19.15% | II | −1.8 | 64.09% | III |
13:00 | −0.1 | 5.36% | I | −0.8 | 18.35% | II | −0.4 | 9.04% | I | 0.8 | 16.41% | II |
16:00 | −0.1 | 5.83% | I | −0.3 | 7.94% | I | 0 | 5.03% | I | 1 | 21.9% | II |
19:00 | −0.6 | 12.07% | II | −0.5 | 9.36% | I | −0.2 | 6.77% | I | −0.2 | 6.22% | I |
23 January | 24 January | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Outdoor | 3F | 4F | Outdoor | 3F | 4F | |||||||
OT | RH | RT | RH | RT | RH | OT | RH | RT | RH | RT | RH | |
Minimum | −7.26 | 13.00 | 8.00 | 7.20 | 9.00 | 9.10 | −9.51 | 6.00 | 8.10 | 5.30 | 9.20 | 7.30 |
Maximum | 5.15 | 44.00 | 30.80 | 16.20 | 22.40 | 14.60 | 5.82 | 48.00 | 32.60 | 16.40 | 23.00 | 15.00 |
Mean | −0.43 | 21.31 | 19.81 | 10.45 | 15.87 | 11.56 | −1.11 | 16.69 | 21.37 | 9.56 | 16.85 | 11.08 |
SD | 4.55 | 9.82 | 7.11 | 3.45 | 4.30 | 2.15 | 5.51 | 13.10 | 7.48 | 4.39 | 4.56 | 2.93 |
Renovation Site | Energy-Saving Technical Measures | Construction Method | Heat Transfer Coefficient (W/m2·K) |
---|---|---|---|
External wall | Using rock wool as insulation | 10 mm cement mortar + 370 mm heavy mortar clay + 10 mm cement mortar + 90 mm rock wool insulation layer + 110 mm air layer (including light steel keel hangings + 10 mm granite hanging surface) | 0.31 |
Roofing | Inverted roof | 20 mm cement mortar + 2 mm thick 911 polyurethane waterproof coating + 20 mm cement mortar + 100 mm thick extruded polystyrene (XPS) heat insulation board + 40 mm reinforced concrete + 20 mm cement mortar | 0.41 |
Shutter | Improve airtightness, increase window opening ratio | Single-frame hollow double-glazed steel sliding window (6 + 12A + 6) | 2.71 |
Glass Curtain Walls | Improvement of heat storage capacity | Hollow double-glazed curtain wall Internal injection of dry or inert gas or evacuation | 2.98 |
Activities | Air Exchange Rate | Clothing (clo) | RH | Air Velocity (m/s) | Thermal Neutral Temperature (℃) | Staffing (People/m2) | Lighting Power (W/m2) | Electrical Power (W/m2) | |
---|---|---|---|---|---|---|---|---|---|
Office | Meditation, typing | 0.5 | 1.47 | 10.7% | 0.2 | 18.9 | 0.1 | 9 | 15 |
Meeting Room | Meditation, typing | 0.5 | 1.47 | 10.7% | 0.2 | 18.9 | 0.1 | 9 | 15 |
Space for transportation | Walking | 1 | 1.47 | 10.7% | 0.2 | 18.9 | 0.1 | 9 | 15 |
Dates | Variant | Sample Size | RMSE | d |
---|---|---|---|---|
23 January | RT | 13 | 5.40 | 0.97 |
24 January | 13 | 5.02 | 0.99 |
Measurement Results before Renovation | Simulation Results before Renovation | Simulation Results after Renovation | |||||||
---|---|---|---|---|---|---|---|---|---|
PMV | PPD | Level | PMV | PPD | Level | PMV | PPD | Level | |
10:00 | −1.8 | 64.0% | III | −1.7 | 55.8% | III | −0.29 | 11.9% | II |
13:00 | 0.8 | 16.4% | II | −1.01 | 39.3% | III | −0.45 | 18.2% | II |
16:00 | 1 | 21.9% | II | −0.6 | 42.3% | III | 0.84 | 30.8% | II |
19:00 | −0.2 | 6.22% | I | −0.75 | 42.8% | III | 0.65 | 16.6% | II |
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Sun, W.; Chen, L.; Suolang, B.; Liu, K. An Investigation of the Energy-Saving Optimization Design of the Enclosure Structure in High-Altitude Office Buildings. Buildings 2024, 14, 645. https://doi.org/10.3390/buildings14030645
Sun W, Chen L, Suolang B, Liu K. An Investigation of the Energy-Saving Optimization Design of the Enclosure Structure in High-Altitude Office Buildings. Buildings. 2024; 14(3):645. https://doi.org/10.3390/buildings14030645
Chicago/Turabian StyleSun, Wenjing, Lixing Chen, Baimu Suolang, and Kai Liu. 2024. "An Investigation of the Energy-Saving Optimization Design of the Enclosure Structure in High-Altitude Office Buildings" Buildings 14, no. 3: 645. https://doi.org/10.3390/buildings14030645