Development of a Bayesian inference model for assessing ventilation condition based on CO_(2)meters in primary schools

Outdoor fresh air ventilation plays a significant role in reducing airborne transmission of diseases in indoor spaces.School classrooms are considerably challenged during the COVID-19 pandemic because of the increasing need for in-person education,untimely and incompleted vaccinations,high occupancy density,and uncertain ventilation conditions.Many schools started to use CO_(2)meters to indicate air quality,but how to interpret the data remains unclear.Many uncertainties are also involved,including manual readings,student numbers and schedules,uncertain CO_(2)generation rates,and variable indoor and ambient conditions.This study proposed a Bayesian inference approach with sensitivity analysis to understand CO_(2)readings in four primary schools by identifying uncertainties and calibrating key parameters.The outdoor ventilation rate,CO_(2)generation rate,and occupancy level were identified as the top sensitive parameters for indoor CO_(2)levels.The occupancy schedule becomes critical when the CO_(2)data are limited,whereas a 15-min measurement interval could capture dynamic CO_(2)profiles well even without the occupancy information.Hourly CO_(2)recording should be avoided because it failed to capture peak values and overestimated the ventilation rates.For the four primary school rooms,the calibrated ventilation rate with a 95%confidence level for fall condition is 1.96±0.31 ACH for Room#1(165 m^(3)and 20 occupancies)with mechanical ventilation,and for the rest of the naturally ventilated rooms,it is 0.40±0.08 ACH for Room#2(236 m^(3)and 21 occupancies),0.30±0.04 or 0.79±0.06 ACH depending on occupancy schedules for Room#3(236 m^(3)and 19 occupancies),0.40±0.32,0.48±0.37,0.72±0.39 ACH for Room#4(231 m^(3)and 8–9 occupancies)for three consecutive days.

An exploratory study on road tunnel with semi-transparent photovoltaic canopy-From energy saving and fire safety perspectives

Road tunnels consume a large amount of energy,especially in the Canadian cold climate,where the roads are heated electrically or deicing during the winter.For a more sustainable and resilient road tunnel energy system,we conducted an exploratory study on installing a semi-transparent photovoltaic(STPV)canopy at the entrances and exits of a tunnel under a river.The proposed system generates solar-powered electricity,improves thermal and visual conditions,and reduces energy loads.In this study,field measurements of road surface temperature and air temperature were conducted,and numerical simulations with and without STPV were performed to study air and road surface temperatures under different traffic speeds.The field measurements show the road surface temperatures are higher than the air temperature on average.The interior air and road surface temperature were measured to be above 0°C,even though the outdoor temperature is far below 0°C,thus significantly reducing the need for deicing in winter using salts.The simulations show that the air and surface temperatures elevate due to the solar transmission heat through the STPV canopy,thus reducing deicing energy consumption significantly.The fire safety analysis also showed that the proposed system's top opening should be located near the tunnel entrance instead of the canopy entrance for better smoke exhaust during a fire.

Numerical simulations of smoke spread during solar roof fires

As the installation of solar roofs increases,so has the concern over fires.Smoke from a solar roof fire could spread into a building through roof openings and presents a challenge for existing fire protection strategies.To date,there have been insufficient studies on solar roof fire-induced smoke spread.In this study,we conducted computational fluid dynamics(CDF)simulations using Fire Dynamics Simulator(FDS)to better understand the mechanisms of solar roof fire-induced smoke spread and help with solar roof designs.First,the photovoltaic(PV)combustion model was created in FDS and validated by experimental data.A parametric study was then simulated to investigate the impacts of roof slopes and vent sizes on the smoke spread of the solar roofs.It was found that the roof slope has a significant effect on the fire smoke spread.As the roof slope increases,the region of separation,where the smoke and air are mixed,can extend from the leeward side of the building to the roof ridge.As a result,smoke could fill the attic and room more slowly,leading to a lower soot density and lower indoor temperature.When design a solar roof,both fire smoke protection and PV energy performance should be considered,especially for the low latitude regions where the PV optimal title angle regarding energy performance is small and leads to a higher risk of smoke infiltration.