Indoor environmental quality directly affects occupant health and comfort, with air pollution and odor perception representing two important determinants. This study systematically evaluated the combined effects of an active living wall system (ALWS) on indoor air quality and odor perception. Four cases were tested: Case 1 (soil), Case 2 (soil + filtration), Case 3 (plant + soil) and Case 4 (plant + soil + filtration). Variations in CO2 concentration and particulate matter (PM) was monitored. Results showed that under 24 hours supplementary lighting, CO2 concentration remained within 200 ppm-450 ppm, demonstrating carbon regulation and air purification capacity of the ALWS. In PM experiment, Case 4 exhibited the best performance, reducing PM2.5 below 50 µg/m3 within approximately 517 min and PM10 below 100 µg/m3 in 419 min, indicating efficient particle adsorption and deposition. After calculation, the removal efficiencies of Case 4 for PM2.5 and PM10 were determined to be 41.61 µg/m3˙s and 83.6 µg/m3˙s, respectively. In Case 4, uncovering the chamber increased the mean air-freshness score from 0.63 to 1.38 and the odor-comfort score from 0.31 to 1.21, while decreasing the odor-intensity score from 1.52 to 0.83. Overall, the ALWS not only improved physical air quality but also enhances psychological comfort through visual-olfactory interaction, providing a holistic strategy for healthy and biophilic indoor environments.
The Qinghai-Tibet Plateau serves as a critical ecological barrier and climate stabilizer that regulates global climate and maintains ecological balance. However, carbon emissions from local buildings fueled by straw, firewood, cow dung and other biomass pose severe threats to its fragile ecological environment. Adopting low-carbon strategies to reduce building energy demand is of great significance for mitigating climate change in this region. In this study, highland barley straw (HBS) was adopted as a biomass aggregate to develop a new low carbon composite. The physical, mechanical and thermal properties were systematically characterized, and the energy saving potential of the composite was evaluated for a typical building in Lhasa. As the bulk density increases from 1200 kg·m⁻3 to 1500 kg·m⁻3, the porosity of HBS composite decreases by 11.37%, compressive strength rises from 3.7 MPa to 6.2 MPa, and thermal conductivity increases from 0.101 W·m⁻1·K⁻1to 0.128 W·m⁻1·K⁻1. Microstructural characterization via CT scanning and 3D reconstruction unveiled the interpenetrating network of fibers and binders. Fiber distribution in the planes perpendicular and parallel to the compaction pressure was quantitatively characterized, and the anisotropy in thermal conductivity was elucidated based on the microstructure and fiber distribution of HBS. Replacing traditional blocks with HBS composite reduces heating energy consumption by 88.78% and cuts annual CO₂ emissions by 2794 kg for a typical building in Lhasa. This work demonstrates a scalable, low carbon solution for the Qinghai-Tibet Plateau, with implications for agricultural waste reuse and net-zero building in cold, resource–constrained regions globally.
District heating systems have become the predominant form of winter heating in northern regions owing to their large heating capacity and high energy utilization efficiency. However, long heat-transmission distances and pronounced thermal and hydraulic inertia often result in delayed responses to fluctuations in terminal heat demand, leading to supply–demand mismatches, excessive heat supply, and increased energy consumption. To address these issues, this study develops a thermal–hydraulic model of a community–building–user multi-mode peak-shaving system based on return-water-source heat pumps. Considering the spatiotemporal distribution characteristics of heating loads in typical community buildings, including residential, school, office, and commercial buildings, multi-scenario community energy-use models are established, and the optimal design and capacity configuration of different peak-shaving modes are investigated. System performance is subsequently evaluated in terms of the indoor temperature unmet rate, operational energy consumption, levelized cost of heat, exergy efficiency, and carbon emissions. The suitability of each mode is further assessed using the entropy-weight TOPSIS method. The results indicate that community load characteristics vary considerably and directly affect the operational performance of the multi-mode peak-shaving system. The user-level peak-shaving system exhibits the most stable overall performance and is more suitable for scenarios with pronounced load heterogeneity, such as residential communities. The building-level system demonstrates greater economic suitability for scenarios with substantial load differences among buildings, such as school communities. In contrast, the community-level system is better suited to scenarios with highly synchronized loads, such as commercial communities. These findings provide a basis for mode selection and engineering applications of peak-shaving systems in district heating networks.
The medium-depth coaxial borehole heat exchanger (MCBHE) is a clean-energy technology that can utilize geothermal energy at depths of 1,000-3,000 m for building heating. However, underground parameters significantly affect its heat extraction performance, and the underlying influence mechanisms of different parameters remain unclear. In this study, a three-dimensional CFD model of an MCBHE was established to investigate the effects of soil stratification, ground temperature gradients, groundwater seepage locations, and seepage velocities on its heat extraction performance. The results show that, under stratified soil conditions, the proportion of heat extracted from medium-depth soil layers increases, while the decrease in the inner-tube fluid temperature drop rate (ITFTDR) becomes slower. For the ground temperature gradient, an increase in the linear ground temperature gradient significantly improves the heat transfer efficiency between the MCBHE and the surrounding soil. Although an increase in the layered ground temperature gradient enhances the cumulative heat extraction amount (CHEA), it also leads to higher values of the heat loss rate of the inner tube (HLRIT) and ITFTDR. Under seepage conditions, for both single-layer and double-layer seepage, seepage closer to the lower part of the MCBHE results in a greater increase in CHEA and a lower ITFTDR. A higher uniform seepage velocity promotes temperature recovery of the soil surrounding the MCBHE. Moreover, a seepage pattern in which the velocity gradually increases with soil depth is beneficial for heat extraction from medium-depth soil layers, allowing the fluid in the lower part of the MCBHE to exchange heat more sufficiently with the surrounding soil.
In the context of increasing demands for both indoor health and building energy efficiency, building energy systems integrating solar heating and photovoltaic power generation with air purification show great potential. Incorporating UV inactivation can further enhance disinfection performance. However, in solar utilization systems, air temperature typically falls within a moderate range (40–60°C), and the thermal-UV synergistic inactivation of bioaerosols under such conditions remains insufficiently understood. This study systematically investigates the quantitative thermal-UV synergistic inactivation characteristics of airborne bacteria under different UV peak wavelengths and further develops two self-powered, self-purifying building envelopes. A sealed experimental chamber was constructed to measure the inactivation rate of aerosolized Escherichia coli and Staphylococcus aureus under different UV peak wavelengths (222, 254, and 365 nm) and temperatures (25–60°C). Results show that thermal and UV irradiation exhibit a synergistic inactivation effect at 222 nm and 254 nm. A four-parameter inactivation model was developed and shows good agreement with experimental results. System-level analysis indicates that incorporating UV inactivation significantly improves bioaerosol removal, increasing the daily clean air delivery for E. coli and S. aureus by approximately 2.17 and 5.27 times, respectively. Parametric analysis shows that increasing air channel depth benefits the air purification performance of the system. The findings provide new insights into solar-driven bioaerosol control. Moreover, the established thermal-UV inactivation model can be further extended to air-handling systems such as HVAC systems and heat-recovery ventilation units, offering theoretical support for improving indoor air quality.
