The efficiency and lifetime of Photovoltaic cells degrade with elevated temperature levels over time. Cooling the cells contributes positively to their performance and their lifespan. Heat transfer enhancement techniques using thermal inserts, such as baffles, have been investigated widely within Solar Air Heater research. However, these strategies have not yet been applied to Photovoltaic Thermal technology for such cooling purposes, despite their potential benefits. In this study, V-shaped baffles inspired from Solar Air Heaters are evaluated in the context of Air-Based Photovoltaic Thermal for the first time. A prototype was experimentally tested to validate a Computational Fluid Dynamics model. To further improve the thermohydraulic performance of baffles, a novel design was developed, that of smooth V-baffles. In general, a decrease of 8 C° on average was achieved by the cooling baffles. The new design exhibited a higher Thermal Enhancement Factor than that of the straight edge equivalents, up to 22% higher. Additionally, it was indicated that the use of baffles can be beneficial for Photovoltaic Thermal systems, by achieving a more uniform temperature distribution of the photovoltaic cells, up to 47%. This minimizes the formation of hot zones along the photovoltaic surface.

The European Commission aims to reduce the greenhouse gas emissions of the European Union's building stock by 60% by 2030 compared with 1990. Meanwhile, the global demand for cooling is projected to grow 3% yearly between 2020 and 2050. High-temperature cooling systems provide cooling with lower exergy use than conventional cooling systems and enable the integration of renewable energy sources, and can play a crucial role in meeting the growing cooling demand with less energy use. The aim of this study is to analyse and critically evaluate two high-temperature cooling systems in terms of their energy and exergy use in a case study. We also consider thermal comfort performance, CO2 emissions, and sensitivity to changing operating conditions. The two systems considered are a mechanical ventilation system with heat recovery combined with geothermal cooling (GeoMVHR) and a radiant cooling system with ceiling panels connected to the same geothermal cooling (GeoRadiant) system. The study is conducted using building energy models of a typical office building belonging to a three-building school complex located in Sant Cugat near Barcelona, Spain. IDA ICE 4.8 simulation software was used for the simulations. The results show that the two different installations can produce near-identical thermal comfort conditions for the occupants. The GeoRadiant system achieves this result with 72% lower electricity use and 60% less exergy destruction than the GeoMVHR system. Due to the higher electricity use, the CO2 emissions caused by the GeoMVHR system are 3.5 times the emissions caused by the GeoRadiant system.

Photosynthetically Active Radiation (PAR) is critically required for sustaining plant and vegetable growth. This study investigated PAR availabilities in two typical large-scale greenhouses using an advanced method of climate-based solar modelling in China. Seven Chinese locations in terms of daylight (solar) climate zones and latitudes were studied. The PAR prediction was conducted via RADIANCE (ray-tracing solar and light simulation package). Key findings were: 1) A climate-based analysis was proved as more practical than the methods based on only clear sky and solar geometries. 2) A ray-tracing solar modelling could effectively predict PAR levels at specific positions (e.g. vertical planes), which could benefit the development of vertical farming activities. 3) The PAR availability could receive insignificant impact from roof configuration in these large-scale greenhouses. 4) For the approach of vertical farming, the vertical arrangement of planting system could be significantly affected by greenhouse orientations, while horizontally no such effect can be found. These findings could be developed into design strategies to support greenhouse planning.

Ventilation systems are the primary way of eliminating airborne pathogenic particles in an operating room (OR). However, such systems can be complex due to factors such as different surgical instruments, diverse room sizes, various staff counts, types of clothing used, different surgical types and duration, medications, and patient conditions. OR ventilation should provide a thermally comfortable environment for the surgical staff team members while preventing the patient from suffering from any extreme hypothermia. Many technical, logistical, and ethical implications need to be considered in the early stage of designing a ventilation system for an OR. Years of research and a significant number of publications have highlighted the controversy and disagreement among infection specialists, design engineers, and ventilation experts in this context. This review article aims to provide a good understanding of OR ventilation systems in the context of air quality and infection control from existing research and provide multidimensional insights for appropriate design and operation of the OR. To this end, we have conducted a systematic review of the literature, covering 253 articles in this context. Systematic review and meta-analyses were used to map the evidence and identify research gaps in the existing clinical, practical, and engineering knowledge. The present study is categorized into six research focuses: ventilation system, thermal comfort, staff work practice and obstacles, door operation and passage, air cleaning technology, emission rate, and clothing systems. In the conclusion, we summarize the key limitations of the existing studies and insights for future research direction.

In recent years, the increasing occurrence of heatwaves raises the cooling need of residential buildings in Scandinavian countries, which are traditionally not equipped with active cooling systems. Indoor overheating caused by such heatwaves leads to severe consequences for occupants, especially kids and seniors. Efficient and economical cooling solutions are urgently needed to cope with frequent heat waves. The present study investigated the novel usage of the geothermal-assisted mechanical ventilation with heat recovery (GEO-MVHR) system for cooling purposes in typical Swedish multi-family dwellings. The cooling potential of the system and its contributions to thermal comfort were evaluated. Dynamic simulations were conducted to assess the system’s cooling performance under two climate scenarios: the climate of 2018 representing an extreme year with excessively hot summer and the climate of a typical meteorological year. The GEO-MVHR system shows great potential in mitigating indoor overheating with improved thermal comfort. A ventilation airflow rate of0.50–0.70 l/s/m2 is suggested for multi-family dwellings to maximize the cooling potential of the GEO-MVHRsystem. The indoor operative temperature could be reduced by up to 3 ◦C with the GEO-MVHR system operating for cooling. Modulating the supply air temperature of the GEO-MVHR system based on indoor thermal conditions is recommended, as it shows the advantage of avoiding unnecessary overcooling and energy saving.

Airborne particles are the main cause of surgical site infections in operating rooms . The ventilation systems are crucial for diluting and removing the airborne particles from the operating room environments. The unidirectional airflow ventilation system is one of the common ventilation that is used in infection-prone surgeries. However, obstacles such as surgical staff and medical lamp may affect the unidirectional-ventilated airflow and consequently, reduce the washing effect of the ventilation. The aim of this study is to numerically investigate the impact of the heat loads on the airflow behaviour and particle distribution in an operating room equipped with unidirectional airflow ventilation system. In this regards, overall heat loads including the equipment, overhead lamps, and medical lamps were considered in the simulated cases. The computational fluid dynamics technique was used to simulate the airflow patterns and Airborne particles distribution. The applied numerical model was validated based on the measurement data. Results showed that the unidirectional airflow ventilation system exhibited satisfactory stability under diverse range of heat loads and can provide acceptable protection for the wound area during the surgery.

This paper presents a framework of exergy analysis to evaluate the performance of the condensing dehumidification and the desiccant wheel dehumidification. The performance of two dehumidification methods are compared for pure dehumidification purposes based on proposed dehumidification systems that undertake only the latent load. An air-source heat pump is adopted in the dehumidification systems to serve as the cold and heat source. Based on thermodynamic perfectibility theory and the laboratory experiment of the desiccant wheel, the power requirements and exergy efficiency of the two dehumidification methods are analyzed and compared under 17 sets of operating conditions. The coefficient of performance of the heat pump in the condensing dehumidification system is 2–3 times higher than in conventional air-conditioning systems. Environmental factors that influence the performance of each dehumidification method are identified. The performance of condensing dehumidification is affected mostly by the humidity ratio of indoor air, whereas the outdoor air temperature has a minor impact. The humidity ratio difference between indoor and outdoor air is the most influential factor in the desiccant wheel dehumidification, followed by the outdoor air temperature. Under the operating conditions examined in the present study, the condensing dehumidification shows 3–4 times higher exergy efficiency than the desiccant wheel dehumidification. Therefore, the condensing dehumidification should be preferred over the desiccant wheel dehumidification for typical indoor dehumidification applications.

Operating room (OR) ventilation plays an important role in mitigating the spread of bacteria-carrying particles (BCPs) and preventing the incidence of surgical site infections (SSIs). The use of surgical lamps in ORs is critical for patient safety and staff comfort. However, the surgical lamp serves as an obstruction in the ventilation airflow and also as a source of heat generation, which often creates a stagnant area under the lamp. Such a stagnant area is normally poorly ventilated, where a significant amount of BCPs can accumulate. As the lamp is usually positioned above the patient to illuminate the wound, the accumulation of airborne BCPs under the lamp leads to a high risk of infections and constitutes a threat to patient safety. Therefore, we proposed an innovative design of the surgical lamp, that is, the fan-mounted surgical lamp. The performance of this new design of lamp was compared with the conventional closed-shape lamp under two ventilation strategies: mixing and unidirectional airflow (UDF) ventilation. To account for different working conditions, both the horizontal and 45° orientations were applied to the lamps. We employed numerical simulations to predict the BCPs contamination in the proximity of the surgical site, as it is directly related to the risk of SSIs. The results showed that the fan-mounted lamp considerably reduced the level of contamination under both ventilation strategies. Results also suggested that the contamination level cannot be effectively reduced by only adjusting the orientation of the closed-shape lamp under unidirectional airflow ventilation.

This study numerically investigated the effect of staff number on the airborne bacteria contamination in two operating rooms (ORs) equipped respectively with conventional turbulent mixing and temperature-controlled airflow (TCAF) ventilation. Four pre-defined cases with 3, 5, 7, and 9 surgical staff surrounding the operating table were simulated. The contamination level steadily rises as more persons were added in the turbulent mixing ventilation. The TCAF ventilation, however, is less sensitive to the number of persons in the OR and maintains a sufficiently low level of contamination in all cases. The mixing ventilation examined in this study is not recommended for infection-prone surgeries if more than 4-5 personnel should be present in the OR. In contrast, the OR with TCAF ventilation can accommodate at least 9 surgical professionals without comprising the ultraclean environment at the surgical site. Comparisons with the analytical estimation based on the perfect dilution model also indicate that TCAF uses airflow more efficiently than the mixing ventilation. 

Operating rooms (ORs) often have door openings connected to uncontrolled areas that are more contaminated. Opening the door may allow an inflow of contaminated air, degrade the microbiological air cleanliness and possibly cause surgical site infections (SSIs). This study numerically investigated the transient airflow and bacteria-carrying particles spread caused by the opening of a sliding door in an OR with mixing ventilation. Results showed that a single door opening raises the overall OR contamination by 2.1 colony-forming units per cubic metre (CFU/m3) under a temperature difference of about 3°C. With a similar level of overall contamination, the risk of infections differs dramatically, as the corresponding contamination at the surgical site ranges from lower than 1 CFU/m3 to higher than 10 CFU/m3. This implies that quantifying only the air volume exchange is not sufficient for a valid and reliable assessment of the impact of door openings on the risk of SSIs. Temporarily reducing the OR exhaust flow during door operation was found to be an effective solution to minimize the impact of door openings on the risk of infections. In the case examined in the present study, a 20–30% reduction in OR exhaust flow decreases the airborne contamination to a sufficiently low level.