Air Handling System Research Articles

Calibration of a Hybrid Model for HVAC Systems for Fault Data Generation

The application of automated fault detection and diagnosis algorithms has proven to be an effective way to increase the energy efficiency of buildings. While data-driven strategies have demonstrated their potential in developing such algorithms, they require a set of historical data that represents both healthy and faulty equipment operation, which is not a common scenario in real facilities. This article presents a methodology for the generation of synthetic data on both healthy and faulty operation for building heating and air conditioning equipment, which is especially useful for supervision and failure detection in the case of replication and expansion of buildings in tertiary or residential building planning programmes. This work investigates the automatic calibration of a typical air-handling unit hybrid model, composed of the detailed parametric representation of the system components and its control sequence coupled with a simplified thermal load. The model is then extended with fault models that resemble commonly encountered component faults to generate operation data in faulty scenarios. The proposed framework is validated in a real use case with the calibration of an air-handling unit system and its control sequence using 15 days of data gathered from the building management system. The results obtained from the injection of seven typical faults are then compared with the fault-free simulations to highlight and validate their impact on key operating variables. The results prove the capabilities of this methodology to support database generation in the fields of fault detection and advanced maintenance of buildings’ air conditioning systems for building replicas.

Large-scale energy cost optimization and performance analysis for dedicated outdoor air system: simulation results from ASHRAE RP-1865

This is the first journal article from the ASHRAE research project RP 1865, “Optimizing Supply Air Temperature Control for Dedicated Outdoor Air Systems,” focusing on the large-scale energy performance evaluation of the optimal control of dedicated outdoor air systems (DOAS). DOAS is a type of air handling system that is installed in buildings to ensure proper ventilation for the built environment. It is acknowledged that DOAS with proper operation strategies can provide sufficient ventilation and dehumidification while achieving energy efficiency. In this regard, there have been efforts to develop advanced control sequences (e.g., optimal control) for DOAS. Still, limited studies have demonstrated the effectiveness of such DOAS controls on a larger scale under varying climate zones with different DOAS configurations. To fill the research gap, this study aims to quantify the energy-saving potentials of applying an optimal supply air temperature (SAT) control strategy for DOAS considering diverse configurations of HVAC systems in various climate conditions across the United States. For this study, we first developed a total of 180 EnergyPlus models accommodating different types of buildings (i.e., detailed medium-sized office and primary school) and HVAC systems (i.e., DOAS types, DOAS sizes, and terminal units) under varying ASHRAE climate zones (i.e., 2A, 3B, 4A, 4C, 6A, and 6B). Next, genetic algorithm (GA)-based optimizations were conducted to determine the optimal DOAS SAT control that would minimize the energy cost of the entire HVAC system operation. Our study of comparing the optimal control to a typical rule-based control (i.e., outdoor air temperature-based reset control) revealed approximately 4–34% of energy cost saving potential by optimizing the DOAS SAT control sequence.

Odour and indoor air quality hazards in railway cars: an Australian mixed methods case study

PurposeThis case study aimed to diagnose the cause(s) of a seasonal, and objectionable odour reported by travellers and drivers in the railway cars of Australian passenger trains. The research questions were to: (1) identify whether significant microbial colonisation was present within the air handling system of trains and causing the odours; to (2) identify other potential sources and; (3) remedial options for addressing the issue.MethodsA mixed-methods, action research design was used adopted. Sections of the heating, ventilation, and air conditioning (HVAC) systems from odour-affected trains were swabbed for bacteria and fungi and examined for evidence of wear, fatigue and damage on-site and off-site. Insulation foam material extracted from the walls of affected trains was also subjected to a chemical assessment following exposure to varying humidity and temperature conditions in a climate simulator. This was accompanied by a qualitative sensory characterisation.ResultsUpon exposure to a variety of simulated temperature and humidity combinations to recreate the odour, volatile chemical compounds released from the insulation foam by water were identified as its likely cause. In addition, a range of potentially serious pathogenic and odour-causing microbes were cultured from the HVAC systems, although it is considered unlikely that bacterial colonies were the odour source.ConclusionThe research has implications for the sanitising and maintenance policies for HVAC systems on public transport, especially when operating in humid environments. The sanitary imposition, especially in the wake of COVID-19 may be required to ensure the safety of the travelling public and drivers.

Direct/indirect optimal use of shallow geothermal energy in floor radiant cooling system coupled with air-handling system

Shallow geothermal energy is used as the cold source of floor radiant cooling systems (RFCSs). A physical simulation test bench was built to study the cooling and dehumidification characteristics of an RFCS to evaluate its feasibility. Three operation modes involving direct-supply chilled water, direct-supply chilled-water coupling air-handling system (AHS), and indirect cascade utilization were evaluated. Results showed that the room could be cooled rapidly in the direct-supply chilled-water mode. When the direct-supply chilled-water temperature was lower than 16 °C, condensation occurred on the floor surface. The AHS effectively avoided condensation, and the maximum humidity ratio difference between the air inlet and outlet was 13.61 g/kg. However, the temperature difference between the chilled water and the floor surface was reduced. Under the cascade utilization mode, the cooling efficiency of the system improved, and the indoor temperature and relative humidity were maintained at 20.6–28.1 °C and 57.0–76.1 %, respectively. This study provides valuable insights into the direct application of geothermal energy in RFCSs.

Growing indoor environmental infrastructure: designing for microbial diversity with implications for pollutant metabolism and human health

Abstract Urban inhabitants spend upwards of 90% of their time indoors where building design and mechanical air-handling systems negatively impact air quality, microbiome diversity and health outcomes. Urban bioremediation infrastructure designed to improve indoor environmental quality by drawing air through photosynthesizing plants and metabolically diverse rhizospheres have been investigated since the 1960s; however, in-depth analysis of the potential impacts on indoor environments is required: (1) although recent evidence has illustrated human microbiome alteration and associated health benefits related to exposure to green wall systems, the mechanism(s) of diversification have not yet been established, (2) microbial metabolism and airborne chemical dynamics are extraordinarily complex and hypotheses pertaining to rhizosphere microorganisms metabolizing pollutants require more attention. To explore these areas, we applied a shotgun metagenomic approach to quantify microbial diversity and establish preliminary metabolic profiles within active green wall modules spanning a range of growth media and plant selections. Results indicate that fundamental design decisions, including hydroponic vs. organic growth media, support rhizosphere microbiomes with distinct diversity and metabolic profiles which could impact system performance. The described relationships indicate fundamental green infrastructure design represents an opportunity to “grow” indoor microbial diversity and metabolisms with potential benefits for human pollutant exposure and health outcomes.

Effects of Ionization on the Filtration of Fine and Ultrafine Particles in Indoor Air

As we spend approximately 80% of our time indoors, improving indoor air quality is necessary to lessen the spread and impacts of respiratory diseases and other health issues caused by particle pollution. Currently, in many countries, the primary method of cleaning indoor air is by using better, higher-grade filters in a recirculating air system or increasing ventilation with outdoor air. One way to supplement these time-tested approaches is by implementing ionization. We used a bipolar ionizer to test the removal efficiency of filters on different particle sizes with and without ionization. Calibrated cigarettes were used to generate smoke into a 28-cubic-meter chamber with a recirculating air handling system. It was found that ionization had a 275% increase in the removal efficiency of the most penetrating particle sizes (100-500 nm). We conclude that ionization drastically improves the filter removal efficiency of fine and ultrafine particles in indoor environments.

Sailing through the COVID-19 Pandemic and Beyond: An Evidence-Based Analysis for Dental Healthcare and Practice.

This integrative review aims to provide a consolidated evidence-based appraisal of the most up-to-date guidelines and recommendations of international public and professional health regulatory bodies in relation to preparedness framework for restructuring safe delivery of dental services amid and beyond the coronavirus disease-2019 (COVID-19) pandemic. Most recent updated guidelines for dental professionals from major international health regulatory bodies were reviewed. PubMed, Google Scholar, Cochrane Central Register of Controlled Trials, WHO COVID-19 and LILACS databases, along with relevant preprints were searched, and citations were checked up to January 23, 2021. The search was performed by one author. Shortlisted articles were read and brought to consensus to be included in the study by at least two co-authors. In case of any disagreement between the judgements, an independent co-author’s decision was taken as final. Of 849 records searched, 61 articles were included in the study. Following content analysis of the global guidelines and the collected prevailing evidence, the common themes and recommendations of different guidance documents were collated and summarized into seven domains. Most guidelines have a consensus regarding implementation of rigorous administrative, engineering and environmental infection control strategies. However, variations do exist with regard to the use of respirators in non-aerosol-generating procedure (non-AGP) settings, employment of airborne precautions during non-AGPs, use of supplemental air-handling systems, and preoperative use of mouthwashes. This evidence-based analysis can serve as a useful reopening resource tool and facilitate effective restructuring for delivery of optimal, equitable and safe dental practices globally, during and while emerging from the pandemic.

An Experimental and Computational Investigation of Tailor-Developed Combustion and Air-Handling System Concepts in a Heavy-Duty Gasoline Compression Ignition Engine

This study investigates using tailor-developed combustion and air-handling system concepts to achieve high-efficiency, clean gasoline compression ignition (GCI) combustion, aimed at addressing a future heavy-duty ultralow NOx standard of 0.027 g/kWh at the vehicle tailpipe and the tightening CO2 limits around the world by combining GCI with a cost-effective engine aftertreatment system. The development activities were conducted based on a 15 L heavy-duty diesel engine. By taking an analysis-led design approach, a first-generation (Gen1) GCI engine concept was developed and tested, encompassing tailor-designed piston bowl geometry, fuel spray pattern, and swirl motion paired with a customized, fixed-geometry, two-stage turbocharging system and a high-pressure EGR loop with two-stage cooling. Across four key steady-state operating points, the Gen1 GCI concept demonstrated 85–95% lower smoke and 2–3% better diesel-equivalent gross indicated fuel consumption compared to the diesel baseline at 1 g/kWh engine-out NOx. By upgrading to a Gen2 air-handling concept that was composed of a prototype, single-stage, variable-geometry turbocharger and a less restrictive EGR loop, 1D system-level analysis predicted that the pumping mean effective pressure was reduced by 43–54% and the diesel-equivalent brake-specific fuel consumption was improved by 2–4%, thereby demonstrating the performance enhancement potential of refining the air-handling system.

Bayesian and machine learning-based fault detection and diagnostics for marine applications

ABSTRACT Marine maintenance can improve ship performance by leveraging predictive maintenance, Machine Learning and Data Analytics. This paper aims to enrich the literature, by developing a novel framework for ship diagnostics based on operational data and the probability of faults. Moreover, the framework can identify the root cause of developing faults avoiding black-box Neural Networks, and complex physics-based models. This research integrates Machine Learning-based Fault Detection, Exponentially Weighted Moving Average control charts, and Bayesian diagnostic networks which allow the examination of the rate of development (fault profile) of faults and failure modes. For validation, the case study of a marine Main Engine is used to examine faults in the engine’s Air Cooler and Air and Gas Handling System. It is concluded that any simultaneous abnormal deviations in the Main Engine’s Exhaust Gas Temperature are more likely to be caused by a fault in the Air and Gas Handling System.

Size dependent infectivity of SARS-CoV-2 via respiratory droplets spread through central ventilation systems

Here we evaluate the transport of respiratory droplets that carry SARS-CoV-2 through central air handling systems in multiroom buildings. Respiratory droplet size modes arise from the bronchioles representing the lungs and lower respiratory tract, the larynx representing the upper respiratory tract including vocal cords, or the oral cavity. The size distribution of each mode remains largely conserved, although the magnitude of each droplet mode changes as infected individuals breathe, speak, sing, laugh, cough, and sneeze. Here we evaluate how each type of respiratory droplet transits through central ventilation systems and the implications thereof for infectivity of COVID-19. We find that while larger oral droplets can transmit through the air handling systems, their size and concentration are greatly reduced with but few oral droplets leaving the source room. In contrast, the smaller droplets that originate from the bronchioles and larynx are much more effective in transiting through the air handling system into connected rooms. This suggests that the ratio of lower respiratory or deep lung infections may increase relative to upper respiratory infections in rooms connected by central air handling systems. Also, increasing the temperature and humidity in the range considered after the droplets have achieved an “equilibrium” size reduces the probability of infection.

Identification of SARS-CoV-2 RNA in healthcare heating, ventilation, and air conditioning units.

Evidence continues to grow supporting the aerosol transmission of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). To assess the potential role of heating, ventilation, and air conditioning (HVAC) systems in airborne viral transmission, this study sought to determine the viral presence, if any, on air handling units in a healthcare setting where coronavirus disease 2019 (COVID‐19) patients were being treated. The presence of SARS‐CoV‐2 RNA was detected in approximately 25% of samples taken from ten different locations in multiple air handlers. While samples were not evaluated for viral infectivity, the presence of viral RNA in air handlers raises the possibility that viral particles can enter and travel within the air handling system of a hospital, from room return air through high‐efficiency MERV‐15 filters and into supply air ducts. Although no known transmission events were determined to be associated with these specimens, the findings suggest the potential for HVAC systems to facilitate transfer of virions to locations remote from areas where infected persons reside. These results are important within and outside of healthcare settings and may present necessary guidance for building operators of facilities that are not equipped with high‐efficiency filtration. Furthermore, the identification of SARS‐CoV‐2 in HVAC components indicates the potential utility as an indoor environmental surveillance location.

The potential of vehicle cooling systems

Vehicle engine cooling systems have several functions. Excess heat removal from the engine helps to rapidly cool it, quickly reach operating temperature, maintain a constant engine operating temperature, and provide heat to the vehicle’s passenger compartment. Developments in the automotive industry, such as hybrid and electric vehicles, now also involve the temperature management of battery packs. Currently, the coolant used in cooling systems is water or an equivalent substance. Water as a coolant has low thermal conductivity. Therefore, researchers are trying to use nano-liquid as a coolant in the cooling system. Better results are expected by use of this alternative. Nano-liquids contain metal particles that enhance thermal transfer properties, so current and future cooling systems could operate more efficiently. Adding phase change materials to the cooling and air handling systems will result in better efficiency in future vehicles. In the case of hybrid and electric vehicles, the addition of thermoelectric generators to cooling and exhaust systems increase efficiency. Present developments help increase a vehicles’ usability and the possibility of achieving greater efficiency.

Tailored Air-Handling System Development for Gasoline Compression Ignition in a Heavy-Duty Diesel Engine

The simultaneous application of new low-NOx emissions standards and greenhouse gas (GHG) rules has placed great pressure on the commercial vehicle industry and has driven demand for innovative solutions. One potential solution, gasoline compression ignition (GCI), utilizes gasoline’s lower reactivity to promote partially premixed combustion and extract efficiency while reducing the PM-NOx trade-off curve. Gasoline’s volatility allows for the use of higher levels of exhaust gas recirculation (EGR), a key enabler of GCI combustion. In order to deliver higher levels of EGR while maintaining sufficient boost pressure, a tailored and efficient air-handling system is critical. This work presents the analysis-led development of a low-NOx GCI air-handling system including both turbocharger matching and EGR configuration for a prototype heavy-duty GCI engine based on a model year 2013 Cummins ISX diesel engine using low octane gasoline (RON80). In the analysis-driven development process, a 1D engine system-level analysis was closely coupled with closed-cycle 3D CFD GCI combustion development. Three different boost systems were investigated using a validated 1D engine model: 1) the production turbocharger; 2) an off-the-shelf single-stage waste-gate turbocharger; 3) a prototype single-stage variable geometry turbocharger. For each boost system, three EGR configurations were evaluated: 1) a high-pressure EGR route; 2) a low-pressure EGR route; 3) a dual-loop EGR route. The air-handling system performance was first investigated over five steady-state engine operating conditions extracted from the ramped modal cycle supplemental emissions test. Then, through cosimulation using a Simulink-based engine controls model, the best performing candidates under transient operation through the Heavy-Duty Federal Test Procedure certification cycle were identified. The production turbocharger, designed for 4–6 g/kWh engine-out NOx, suffered from low combined turbocharger efficiency under the low-NOx GCI thermal boundary conditions. The prototype 1-Stage variable geometry turbocharger, when used with a high-pressure EGR configuration, demonstrated higher combined efficiencies, while the waste-gate turbocharger showed the best results when used with a dual-loop EGR system. All low-pressure only EGR configurations were found to incur additional pumping penalties due to the need for a back pressure valve to drive sufficient EGR levels. In the transient test cycle analysis, the single-stage high-pressure EGR system was capable of delivering the target boost and EGR, while the off-the-shelf waste-gate turbocharger, with its higher mass inertia, showed slower turbine response and a resulting lag in boost response. Unsurprisingly, the dual-loop EGR system also suffered from delays in EGR delivery during engine acceleration. In summary, the prototype single-stage variable geometry turbocharger with a high-pressure EGR system produced the best performance over both the steady-state and transient engine cycles and was identified as the best candidate for the prototype low-NOx heavy-duty GCI engine.

Investigation of potential aerosol transmission and infectivity of SARS-CoV-2 through central ventilation systems

The COVID-19 pandemic has raised concern of viral spread within buildings. Although near-field transmission and infectious spread within individual rooms are well studied, the impact of aerosolized spread of SARS-CoV-2 via air handling systems within multiroom buildings remains unexplored. This study evaluates the concentrations and probabilities of infection for both building interior and exterior exposure sources using a well-mixed model in a multiroom building served by a central air handling system (without packaged terminal air conditioning). In particular, we compare the influence of filtration, air change rates, and the fraction of outdoor air. When the air supplied to the rooms comprises both outdoor air and recirculated air, we find filtration lowers the concentration and probability of infection the most in connected rooms. We find that increasing the air change rate removes virus from the source room faster but also increases the rate of exposure in connected rooms. Therefore, slower air change rates reduce infectivity in connected rooms at shorter durations. We further find that increasing the fraction of virus-free outdoor air is helpful, unless outdoor air is infective in which case pathogen exposure inside persists for hours after a short-term release. Increasing the outdoor air to 33% or the filter to MERV-13 decreases the infectivity in the connected rooms by 19% or 93% respectively, relative to a MERV-8 filter with 9% outdoor air based on 100 quanta/h of 5 μm droplets, a breathing rate of 0.48 m3/h, and the building dimensions and air handling system considered.

Built Environment Airborne Infection Control Strategies in Pandemic Alternative Care Sites.

To identify design strategies utilized in airborne infection isolation and biocontainment patient rooms that improve infection control potential in an alternative care environment. As SARS-CoV-2 spreads and health care facilities near or exceed capacity, facilities may implement alternative care sites (ACSs). With COVID-19 surges predicted, developing additional capacity in alternative facilities, including hotels and convention centers, into patient care environments requires early careful consideration of the existing space constraints, infrastructure, and modifications needed for patient care and infection control. Design-based strategies utilizing engineering solutions have the greatest impact, followed by medical and operational strategies. This article evaluates infection control and environmental strategies in inpatient units and proposes system modifications to ACS surge facilities to reduce infection risk and improve care environments. Although adequate for an acute infectious disease outbreak, existing capacity in U.S. biocontainment units and airborne infection isolation rooms is not sufficient for widespread infection control and isolation during a pandemic. To improve patients' outcomes and decrease infection transmission risk in the alternative care facility, hospital planners, administrators, and clinicians can take cues from evidence-based strategies implemented in biocontainment units and standard inpatient rooms. Innovative technologies, including optimized air-handling systems with ultraviolet and particle filters, can be an essential part of an infection control strategy. For flexible surge capacity in future ACS and hospital projects, interdisciplinary design and management teams should apply strategies optimizing the treatment of both infectious patients and minimizing the risk to health care workers.

Fault Prognosis of Key Components in HVAC Air-Handling Systems at Component and System Levels

Fault prognosis of the air-handling systems, which are the key subsystems of heating, ventilation, and air conditioning systems, allows system operators to know the remaining useful life (RUL), thus preventing unexpected breakdowns and reducing the operational and maintenance costs. In this article, a new hidden semi-Markov model-based method is developed. In the method, only relevant state-transition points are selected and estimated, leading to computational efficiency. Physics-based models are used in a novel way to provide “mapping matrices” relating component capacities to fault severities, capturing impacts of multiple failure modes. Experimental results show that our method can effectively estimate the RUL of the components and the systems. Note to Practitioners —Air-handling systems within HVAC condition the air to satisfy human thermal comfort and air quality requirements. The fault prognosis of these systems is critical, since it allows system operators to know the remaining useful life (RUL), thus preventing unexpected breakdowns and reducing the operational and maintenance costs. In this article, a new hidden semi-Markov model-based method is developed to estimate the RUL of an air-handling system and its components. Experimental results show that our method can predict the RUL of the components and systems with high accuracy.

Tri-generation of air conditioning, refrigeration and potable water by a novel absorption refrigeration system equipped with membrane dehumidifier

Air conditioning and refrigeration systems account for almost half of the energy consumption in buildings of the developed countries. The liquid sorption system is a promising alternative to the conventional vapor compression system which is energy inefficient. It is classified into open (dehumidification) and closed (absorption) systems which are used to control the humidity of air and temperature of the cooling stream respectively. The present study proposes a new hybrid system that integrates the absorption refrigeration system with a membrane dehumidifier for air conditioning and refrigeration. The proposed system also produces potable water from ambient humidity. It is viable only with the membrane dehumidifier since its microporous membrane avoids the direct contact between the air and solution streams but allows heat and mass transfer between them. As a result, the vacuum pressure of the proposed system remains unaltered. Moreover, the corrosion in the proposed (due to traces of air) and air handling systems (due to traces of solution) is avoided. In the present study, the performance of the proposed system is compared with the conventional absorption refrigeration system and also investigated under the influence of the design and operating parameters, and ambient conditions. Performance analysis found that the proposed system produces the air with 2.6 kW cooling capacity and 0.00102 kg/s potable water from the given evaporator load of 10 kW for the hot and humid climatic conditions.

Energy Performance Evaluation of a Desiccant Air Handling System to Maximize Solar Thermal Energy Use in a Hot and Humid Climate

A desiccant air handling unit is one of the major types of dehumidification handling systems and requires hot water or hot air to regenerate sorption materials. If solar thermal energy is used as the heat source for regeneration, in general, a backup electrical heater, backup boiler, or combined heat and power (CHP) is installed in order to maintain a stable hot water supply. In this study, effective control is proposed for a desiccant air handling system that uses solar thermal energy (flexible control), and its energy performance is compared to that of a traditional control (the fixed control) through a system simulation. The diurnal behavior shows that the system with a fixed control without a backup boiler cannot process the latent load properly (28 GJ of unprocessed latent load for July and August). On the other hand, the system with a flexible control without a backup boiler is able to process required latent heat load. Based on the fact that the fixed control needs a backup boiler to process the latent load, the system with a fixed control with a backup boiler is considered for the energy performance comparison. The simulation results show that the primary energy-based coefficient of performance (hereafter, COP) of the system with a flexible control without a backup boiler reaches 1.56. On the other hand, the primary energy-based COP of the system with a fixed control with a backup boiler reaches only 1.43. This proves that the flexible control contributes to the higher energy performance of the system and maximizes the use of solar thermal energy more than the fixed control.

Experimental energy performance assessment of a solar desiccant cooling system in Southern Europe climates

Solar desiccant cooling systems, SDEC, could be an effective alternative to conventional cooling systems, which mainly depend on electrical energy. The main objective of this work was to determine experimentally the seasonal coefficient of performance, SCOP, of a SDEC system composed of a desiccant wheel, an indirect evaporative cooler and a thermal solar system, to control indoor conditions in a research lab room. The dependence of coefficient of performance on outdoor air conditions and percentage of renewable energy used by the SDEC system were also analysed. Experimental tests were carried out for six weeks during spring and summer seasons in Martos, Spain.The experimental results showed that the SDEC system independently adjusted the temperature and humidity of the supply air. 75% of the energy consumed by this air handling system comes from renewable sources. A seasonal coefficient of performance of the SDEC system of 2 was obtained for the period analysed. It is shown that the higher the outdoor temperature, the higher instantaneous COPs is. These results suggest that the use of SDEC systems in hot climates, such as southern European climates, could contribute to achieve the EU's energy goals within the frame of Nearly Zero Energy Buildings.

Numerical Study of Pre-Ventilation Effects on Cabin Temperature Using Solar Sunroof

When a vehicle is parked under the summer sun, to avoid the passenger discomfort caused by high cabin temperature, the performance of forced ventilation, which is called pre-ventilation, using a solar sunroof integrated with a photovoltaic (PV) cell to reduce cabin thermal load is investigated numerically in this study. The vehicle pre-ventilation system is composed of a solar sunroof, DC/DC converter, and air handling system. The indoor thermal load is reduced by the hot cabin air that moves when outside air is supplied to the cabin. The simulation model is established with the component and system model approach using Dymola, and the numerical analysis results are compared with the experimental data. Using the validated model, pre-ventilation performance is analyzed with 40-, 80-, and 120-W PV cells in each solar sunroof system. The results indicate that the 40-W PV cell in the solar sunroof is sufficient for this pre-ventilation application considering cost and cabin thermal comfort performance. Further, the effects on cabin space and DC/DC converter efficiencies were investigated. The analysis results show that cabin volume slightly affected cabin temperature, whereas the efficiency of DC/ DC converter was not significantly affected by cabin temperature reduction.