Energy Recovery Ventilator Research Articles

Impact of improved indoor air quality in Nunavik homes on children's respiratory health.

Between 2007 and 2012, hospitalization rate related to respiratory system diseases in children ≤1-year-old was near 7 times higher in Nunavik compared with the whole province of Quebec. To assess the impact of poor indoor air quality (IAQ) in residential environments on children's respiratory health, the Nunavik's intervention study investigated the impact of the optimization of ventilation systems on the incidence rates of respiratory infections in children in Nunavik. Children under 10years were recruited and categorized according to the type of ventilation system in their home: energy recovery ventilator (ERV), heat recovery ventilator (HRV), no HRV or ERV, and control groups. Children's' medical records were analyzed over a period of 50weeks pre- and post-intervention. Clinical diagnoses were classified into 4 categories: upper respiratory infections, lower respiratory infections, otitis media, and asthma. A decrease in respiratory infections episodes was observed in all groups following intervention with the highest impact observed for HRV systems (-53.0%). Decreases in the ERV group were not significant (-21,7%) possibly due to the presence of some volatile organic compound (such as propylene glycol) and inerrant experimental bias. Nevertheless, no significant association was found between health episodes incidence and household's behaviors or IAQ.

Experimental study on the net outdoor airflow ratio in supply air of membrane-based energy recovery ventilator

The total energy recovery ventilator for outdoor air handing plays an important role in reducing energy consumption of the ventilation system. At the same time, the cross infection between fresh air and return air is a direct threat to the safety of energy recovery components with the influence of COVID-19. Therefore, how to improve the total exchange effectiveness and net outdoor air flow ratio in supply air of the heat recovery system has become an urgent problem to be solved. In this study, the composite membrane was prepared by non-woven fabric, siloxaneamide and lithium chloride solution, which was used as the membrane for the heat and mass transfer between fresh air and return air. The variation of the selective permeability of the composite membrane was studied experimentally. The experimental results show that the highest permeance of the composite membrane for the water vapor permeability can reach until 32.5×10-8kg/m2·s·Pa. The net outdoor air flow ratio in supply air is 94% when the air volume is 550m3/h The heat exchange efficiency of the heat recovery device is 63.2% under the conditions of the dry and wet bulb temperatures of return air and outdoor air are 21.2°C/12.9°C and 2.3°C/1.2°C, respectively.

A SIMULATION BASED STUDY OF ENERGY CONSERVATION OF RESIDENCES IN LAHORE, PAKISTAN

A house in composite climate of Lahore (Pakistan) needs intensive cooling in summers; energy recovery ventilation to reduce humidity during monsoon and comfortable indoor temperature during winters. All these conditions have to be fulfilled with a reduced load on energy resources. Recent trends in construction and design of residential buildings in Pakistan symbolize uncontrolled use of energy resources. There is no data available with planning and developing authorities of housing sector that shows an account of energy loads of built houses. The potential of conservation of energy will be analyzed by actually studying the cooling and heating loads of recently constructed houses
 Key Words: Energy Conservation Potential, Module Study, Simulations

Data-Driven Models for Estimating Dust Loading Levels of ERV HEPA Filters

With increasing global concerns regarding indoor air quality (IAQ) and air pollution, concerns about regularly replacing ventilation devices, particularly high-efficiency particulate air (HEPA) filters, have increased. However, users cannot easily determine when to replace filters. This paper proposes models to estimate the dust loading levels of HEPA filters for an energy-recovery ventilation system that performs air purification. The models utilize filter pressure drops, the revolutions per minute (RPM) of supply fans, and rated airflow modes as variables for regression equations. The obtained results demonstrated that the filter dust loading level could be estimated once the filter pressure drops and RPM, and voltage for the rated airflow were input in the models, with a root mean square error of 5.1–12.9%. Despite current methods using fewer experimental datasets than the proposed models, our findings indicate that these models could be efficiently used in the development of filter replacement alarms to help users decide when to replace their filters.

Experimental investigation of condensation in energy recovery ventilators

Membrane-based Energy Recovery Ventilators (ERV) have become an important part of modern ventilation systems for commercial and residential buildings due to their high sensible and latent effectiveness. Using ERVs in winter conditions, however, can result in condensation and frost formation. Whereas frost formation requires extremely low temperatures, condensation can occur even in mild winter weather conditions. In this study, a widely used ERV is experimentally tested under various indoor and outdoor operating conditions. Short time tests are used to determine the onset of condensation while long time tests are used to investigate the effect of channel blockage due to condensation on pressure drop and effectiveness of the ERV. The presence of condensation is inferred from visual observation of water in the exchanger, investigation of the sensible and latent effectiveness, and measurements of pressure drop over the exchanger. It is shown that condensation increases the sensible effectiveness of the supply side and decreases the sensible effectiveness of the exhaust side. Additionally, the latent effectiveness of both air streams increases when condensation occurs, although the increase in exhaust side latent effectiveness is more significant. Increasing the relative humidity and temperature of the indoor air increases the possibility of condensation and its rate, while increasing flowrate only increases the rate of condensation and does not affect its onset. Finally, the accumulation of water in the channels significantly increases the pressure drop in the exhaust side while it does not significantly impact the effectiveness.

Applicability of an organic Rankine cycle for a liquid desiccant-assisted dedicated outdoor air system in apartments

This study investigates the dehumidification and energy performance of central ventilation systems based on a liquid desiccant-assisted dedicated outdoor air system applied to an apartment residential building. This heat-driven central ventilation system should receive heat energy because of regenerating the liquid desiccant. An organic Rankine cycle (ORC) consists of the central ventilation system proposed in this study to provide heat to the regeneration of the desiccant solution. The overall configuration of the ventilation system consists of three main devices, a liquid type of desiccant system, an evaporative cooler driven indirectly to utilize free cooling energy, and the electric heating coil to supply the process air at a neutral temperature condition. The size of the ORC is determined to provide the base electricity demand of community facilities in the apartment selected in this study. The evaluation of the size and energy performance is conducted through a detailed simulation. The results of the energy simulation are compared with heat-driven desiccant wheel and conventional energy recovery ventilation systems. The proposed system demonstrates 4%–24% lower annual primary energy consumption than two existing ventilation systems. This result can be expected that the proposed liquid desiccant-based central ventilation system incorporating ORC is possible to contribute to the achievement of the zero-energy building by using both electricity and heat energy.

BIPV/T for Arctic Residential Applications

This study aims to investigate the performance of an open loop air-based building integrated photovoltaic/thermal collector (BIPV/T) to preheat Energy Recovery Ventilator (ERV) supply air and to generate electrical energy. ERVs have proven successful in cold climates, but in the extreme cold of the arctic frequent frosting and defrosting cycles reduce their effectiveness and increase energy consumption. Thus, by integrating with BIPV/T, this problem can be reduced while also generating solar electricity. A finite difference model of the BIPV/T system integrated in a typical potential application was simulated in MATLAB using local weather data and fresh air requirements to obtain system outputs. BIPV/T parameters such as tilt angle, cavity width and height were varied, keeping in mind nominal lumber sizes and ease of construction for improved implementation for Arctic residential applications.

Indoor air quality impacts of residential mechanical ventilation system retrofits in existing homes in Chicago, IL

Mechanical ventilation systems are used in residences to introduce ventilation air and dilute indoor-generated pollutants. A variety of ventilation system types can be used in home retrofits, influencing indoor air quality (IAQ) in different ways. Here we describe the Breathe Easy Project, a >2-year longitudinal, pseudo-randomized, crossover study designed to assess IAQ and adult asthma outcomes before and after installing residential mechanical ventilation systems in 40 existing homes in Chicago, IL. Each home received one of three types of ventilation systems: continuous exhaust-only, intermittent powered central-fan-integrated-supply (CFIS), or continuous balanced system with an energy recovery ventilator (ERV). Homes with central heating and/or cooling systems also received MERV 10 filter replacements. Approximately weeklong field measurements were conducted at each home on a quarterly basis throughout the study to monitor environmental conditions, ventilation operation, and indoor and outdoor pollutants, including size-resolved particles (0.3–10 μm), ozone (O3), nitrogen dioxide (NO2), carbon dioxide (CO2), carbon monoxide (CO), and indoor formaldehyde (HCHO). Mean reductions in indoor/outdoor (I/O) ratios across all systems after the intervention were approximately 12% (p = 0.001), 10% (p = 0.008), 42% (p < 0.001), 39% (p = 0.002), and 33% (p = 0.007), for CO2, NO2, and estimated PM1, PM2.5, and PM10, respectively. There was a reduction in I/O ratios for all measured constituents with each type of system, on average, but with varying magnitude and levels of statistical significance. The magnitudes of mean differences in I/O pollutant concentrations ratios were generally largest for most pollutants in the homes that received continuous balanced with ERV and smallest in the homes that received intermittent CFIS systems, with apparent benefits to providing ventilation continuously rather than intermittently. All ventilation system types maintained similar indoor temperatures during pre- and post-intervention periods.

The Breathe Easy Study: Impacts of Ventilation Improvements on IAQ and Adult Asthma in 40 Existing Homes in Chicago, IL

BACKGROUND AND AIM: This paper presents preliminary results of the Breathe Easy Project, which as designed to improve indoor air quality (IAQ) and asthma-related health outcomes by installing residential mechanical ventilation systems in forty existing homes in Chicago, IL. Each home had at least one self-reported adult resident with asthma and received one of three types of ventilation systems half-way through the study: exhaust-only system, central-fan-integrated-supply (CFIS) system, or balanced system with an energy recovery ventilator (ERV). METHODS: We conducted quarterly field measurements to monitor indoor and outdoor pollutants, including size-resolved particles (0.3-10 µm), ozone (O3), nitrogen dioxide (NO2), carbon dioxide (CO2), carbon monoxide (CO), and formaldehyde (HCHO). Monthly asthma control test (ACT) surveys were administered for each participant throughout the study. Wilcoxon signed-rank tests were used to evaluate the impacts of ventilation system retrofits on IAQ, indoor/outdoor (I/O) ratio, and ACT score. Chi-square tests for independence and multiple logistic regression were used to analyze associations between IAQ, asthma severity, and baseline characteristics of participants and homes. RESULTS:Indoor pollutant concentrations and I/O ratios were significantly lower after ventilation system retrofits for indoor concentrations of HCHO, CO2, PM1.0, PM2.5, and PM10, and I/O ratios of CO2, NO2, PM1.0, and PM2.5 (P 0.05). There was a small but significant increase in average ACT score of 1.04 across the entire study population after the ventilation system retrofits (P 0.001). Based on association analysis of the pre-intervention period, higher NO2 concentrations were associated with increased odds of poorly controlled asthma, with crude odds ratios (OR) (95% CI) of 2.8 (1.2−6.4). Also, Black participants showed OR (95% CI) of 5.7 (1.3−25.9) for poorly controlled asthma compared to White participants. CONCLUSIONS:The results can potentially provide information on the influence of exposure for many air toxics and will furnish an opportunity to evaluate exposure models for these compounds. KEYWORDS: Air pollution, asthma, exposures, occupational epidemiology

Energy Saving Quantitative Analysis of Passive, Active, and Renewable Technologies in Different Climate Zones

The purpose of this study was to provide a guideline for the selection of technologies suitable for ASHRAE international climate zones when designing high-performance buildings. In this study, high-performance technologies were grouped as passive, active, and renewable energy systems. Energy saving technologies comprising 15 cases were categorized into passive, active, and renewable energy systems. EnergyPlus v9.5.0 was used to analyze the contribution of each technology in reducing the primary energy consumption. The energy consumption of each system was analyzed in different climates (Incheon, New Delhi, Minneapolis, Berlin), and the detailed contributions to saving energy were evaluated. Even when the same technology is applied, the energy saving rate differs according to the climatic characteristics. Shading systems are passive systems that are more effective in hot regions. In addition, the variable air volume (VAV) system, combined VAV–energy recovery ventilation (ERV), and combined VAV–underfloor air distribution (UFAD) are active systems that can convert hot and humid outdoor temperatures to create comfortable indoor environments. In cold and cool regions, passive systems that prevent heat loss, such as high-R insulation walls and windows, are effective. Active systems that utilize outdoor air or ventilation include the combined VAV-economizer, the active chilled beam with dedicated outdoor air system (DOAS), and the combined VAV-ERV. For renewable energy systems, the ground source heat pump (GSHP) is more effective. Selecting energy saving technologies that are suitable for the surrounding environment, and selecting design strategies that are appropriate for a given climate, are very important for the design of high-performance buildings globally.

Indoor air quality assessment in dwellings with different ventilation strategies in Nunavik and impacts on bacterial and fungal microbiota.

Indoor air quality is a major issue for public health, particularly in northern communities. In this extreme environment, adequate ventilation is crucial to provide a healthier indoor environment, especially in airtight dwellings. The main objective of the study is to assess the impact of ventilation systems and their optimization on microbial communities in bioaerosols and dust in 54 dwellings in Nunavik. Dwellings with three ventilation strategies (without mechanical ventilators, with heat recovery ventilators, and with energy recovery ventilators) were investigated before and after optimization of the ventilation systems. Indoor environmental conditions (temperature, relative humidity) and microbiological parameters (total bacteria, Aspergillus/Penicillium, endotoxin, and microbial biodiversity) were measured. Dust samples were collected in closed face cassettes with a polycarbonate filter using a micro-vacuum while a volume of 20m3 of bioaerosols were collected on filters using a SASS3100 (airflow of 300L/min). In bioaerosols, the median number of copies was 4.01×103 copies/m3 of air for total bacteria and 1.45×101 copies/m3 for Aspergillus/Penicillium. Median concentrations were 5.13×104 copies/mg of dust, 5.07×101 copies/mg, 9.98 EU/mg for total bacteria, Aspergillus/Penicillium and endotoxin concentrations, respectively. The main microorganisms were associated with human occupancy such as skin-related bacteria or yeasts, regardless of the type of ventilation.

Detailed Analysis of Thermal Comfort and Indoor Air Quality Using Real-Time Multiple Environmental Monitoring Data for a Childcare Center

Thermal comfort, indoor air quality (IAQ), and energy use are closely related, even though these have different aspects with respect to building performance. We analyzed thermal comfort and IAQ using real-time multiple environmental data, which include indoor air temperature, relative humidity, carbon dioxide (CO2), and particulate matter (e.g., PM10 and PM2.5), as well as electricity use from an energy recovery ventilation (ERV) system for a childcare center. Thermal comfort frequency and time-series analyses were conducted in detail to thoroughly observe real-time thermal comfort and IAQ conditions with and without ERV operation, and to identify energy savings opportunities during occupied and unoccupied hours. The results show that the highest CO2 and PM10 concentrations were reduced by 51.4% and 29.5%, respectively, during the occupied hours when the ERV system was operating. However, it was also identified that comfort frequencies occurred during unoccupied hours and discomfort frequencies during occupied hours. By analyzing and communicating the three different types of real-time monitoring data, it is concluded that the ERV system should be controlled by considering not only IAQ (e.g., CO2 and PM2.5) but also thermal comfort and energy use to enhance indoor environmental quality and save energy based on real-time multiple monitoring data.

Development of TRNSYS model for energy performance simulation of variable refrigerant flow air-conditioning system combined with energy recovery ventilation

ABSTRACT The variable refrigerant flow air-conditioning system is an HVAC system that can perform at a high capacity with low consumption thanks to its variable-speed compressor. The paper introduces a TRNSYS model to build a simulation model to calculate the energy performance of an existing variable refrigerant flow system and to build a model that can be used as a reference when a VRF system is proposed to a certain situation. The TRNSYS model was compared with the actual energy consumption to see the data agreement between the two models. Temperature, Relative Humidity, and energy consumption were metered using proper instruments, and it was compared with the obtained simulation results. The validation of the simulation model showed close values to the actual system, as the obtained Normalized Mean Bias Error (NMBE) between the simulation and measured values for temperature and relative humidity was 4.3 and 7.6%, respectively. While it was around 7.8% for the total energy consumption. Besides, the paper proposed an Energy Recovery Ventilation to be simulated with the existing TRNSYS model to compare it with the same system without ventilation to see if it is feasible to add an Energy Recovery Ventilation unit to the existing system. It shows a worthy reason to be used, as it saves 18.8% annually of the energy consumption of the system.

Simulation of energy impact of an energy recovery ventilator in Northern housing

The single core Energy Recovery Ventilator (ERV) used in this study is equipped with defrost control that recirculates the exhaust indoor air, while keeps the outdoor air intake damper closed. This defrost strategy has the disadvantage of reducing the outdoor air supplied to the house, which may affect the indoor air quality. First, this paper presents new correlation-based models of supply air temperature T2 after the energy recovery core during normal and defrost operation modes based on laboratory experimental data. A pre-heating coil heats the supply air from T2 to indoor air temperature. Second, a house in Montreal (4356 HDD) is simulated as a reference using TRNSYS program. Since the program cannot simulate the operation under defrost mode, the new models are connected in TRNSYS using equation boxes. The energy use of houses at three locations in northern Canada with HDD of 8798 (Inuvik), 8888 (Kuujjuaq) and 12208 (Resolute), are also simulated, without and with ERV unit. The seasonal energy used for heating the house and pre-heating the supply air is compared with results from Montreal. Compared to the case without heat recovery, the ERV unit leads to energy savings: 24% (Montreal), 26% (Inuvik), 27% (Kuujjuaq), and 27% (Resolute). Compared to the minimum standard requirements, the outdoor airflow rate due to defrost is reduced by 4.7% (223 hours) in Montreal, 19% (1043 hours) in Inuvik, 13% (701 hours) in Kuujjuaq, and 24% (1379 hours) in Resolute.

Experimental Measurement and Computational Simulation Analysis of Indoor Air Quality in Office—Integration of Voltage Adsorption Dust Collection Device and Energy Recovery Ventilator

Experimental Measurement and Computational Simulation Analysis of Indoor Air Quality in Office—Integration of Voltage Adsorption Dust Collection Device and Energy Recovery Ventilator

Performance of energy recovery ventilators under different climatic regions

Energy recovery ventilators (ERVs) have been utilized within air conditioning systems to enhance energy efficiency and to improve indoor air quality. ERV performance contributes significantly towered lowering electrical consumption and emissions of the installed systems. Annual energy savings resulted from integrating a hybrid flow ERV to a conventional HVAC system is numerically investigated in the current research. Thermal performance of air to air ERV is estimated with the aid of computational fluid dynamics (CFD) approach, and the average annual energy consumption of the simulated building is estimated using hourly analysis program (HAP) software at different locations worldwide. Based on CFD simulations, a correlation for the total effectiveness of the ERV was developed (et = 4.2ΔTR0.06377Re−0.29458) which is a function of dry and wet bulb temperature at design conditions of a given location (ΔTR) and Reynolds number (Re) of air flowing through the ERV. Furthermore, CFD simulations showed that the amount of latent energy recovered could be as high as 6 times the amount of sensible energy recovered as the ambient conditions approaches the tropical humid conditions or as ΔTR decreases. Building simulations using HAP showed that the ERV has reduced the size of the cooling/heating coils which resulted in lowering the electrical energy needed to run the HVAC equipment. Utilizing the ERV could also contribute to coil downsizing of up to 40.5 kW, a total electrical load recovery of up to 8648 kWh and RER values of up to 662 for tropical cities such as Singapore. Moreover, an up to 16,000 kgCO2e could be reduced with an annual cost saving of up to US$3000 when adopting the ERV unit. Therefore, it is recommended to design the ERV to serve at relatively low Re values which reflects on obtaining higher effectiveness, lower pressure drop and the greatest possibility for energy recovery.

Energy saving potential of a model-predicted frost prevention method for energy recovery ventilators

This study evaluates the energy-saving potential of a prediction model-based pre-heat coil operation method for frost prevention in energy recovery ventilators, compared to existing approaches. Energy recovery ventilator (ERV) requires pre-heating of the incoming outdoor air to prevent undesirable condensation and frost formation in the enthalpy exchanger during winter. Conventionally, the introduced outdoor air is pre-heated to a certain constant temperature using a pre-heat coil, resulting in unnecessary energy consumption. Maintaining a constant pre-heat temperature during the operation of the ERV is not ideal as the frost threshold temperature varies with the outdoor air temperature and humidity. Therefore, to reduce pre-heating energy consumption, a prediction model-based pre-heat coil operation method is proposed herein. A numerical model predicting the frost threshold temperature based on the outdoor air and exhaust air conditions was developed, and validated using the optimal Latin hypercube design method. Subsequently, a series of energy simulations was performed considering an identical residential model, located in 8 cities with different climatic conditions, to evaluate the energy-saving potential of the proposed pre-heat coil operation method compared to conventional methods. The proposed method consumed 7%–72% less energy in the ERV operation and required a 1%–21% smaller pre-heat coil capacity than the conventional method. Thus, the proposed operation method is superior to the conventional method as it prevents frost formation and consumes a minimal amount of energy.

열회수형 환기장치의 습도교환효율에 따른 동/하계 결로 발생률과 에너지회수율

To resolve indoor air pollution such as CO₂ concentration problems that threaten the health of the occupants as well as to minimize the ventilation load that occupies a large portion of the cooling and heating loads, recently, the air-conditioning industry of cooling buildings including general houses has attracted much interest in Energy Recovery Ventilators (ERV). The commercially available ERV shows relatively good performance in general outdoor conditions, but condensation occurs inside the device from a humid climate in summer or a low temperature in winter, causing problems such as mold and rust. In this paper, the actual condensation occurrence ratio of South Korea was derived according to the latent effectiveness, and the outdoor conditions in which such condensation occurred were analyzed. As a result of summer simulation, the condensation occurrence ratio of Seoul/Busan was approximately 4.9%/12.9% at 0% latent effectiveness, and 0.7%/3.0% at 10%. In Seoul and Busan, condensation rarely occurs when the latent effectiveness is more than 20%. As a result of the winter simulation, the condensation occurrence rate of Seoul/Busan is approximately 84.9%/51.6% at the latent effectiveness of 0%. In the case of Seoul, as the latent effectiveness increases, the condensation occurrence rate slowly decreases, and then rapidly decreases from 30%. Condensation rarely occurs at 80% or more. In the case of Busan, it decreases linearly, and condensation rarely occurs at 70% or more.

Semi-empirical mapping method for energy recovery wheel performance simulation

Abstract Energy recovery ventilators are often employed in buildings to decrease the energy consumed by their HVAC systems, and to improve overall indoor air quality. Several studies in the open literature have developed physical or empirical models to simulate the performance of energy recovery wheels. However, these models are often computationally intensive, time-consuming, or require numerous experimental data points to train and execute the performance predictions. These models also tend to lack flexibility for varying all of the available wheel design parameters. Hence, developing a mapping method with better computational efficiency and flexibility is the goal of this research. A finite difference numerical model for simulating the performance of an energy wheel has been developed and validated using experimental test results from independent laboratories. This model was then employed to provide an extensive data set for the development of an energy wheel performance mapping method. After validating this new mapping approach, the method predictions were compared against independent data sets from two different laboratories, and additional sources available in the literature, to identify its universality. The mapping method delivers good agreement between the predictions and validation data, and requires only a small number of data points to train, which is one of its novel contributions. Another unique contribution of the proposed mapping method is that once the model is trained it can predict the performance characteristics for other wheels with different physical design geometries and operating conditions, provided only that the desiccant material is the same.

다중이용업소의 환기방법에 따른 냉·난방에너지 소비량

Recently, the pandemic virus COVID-19 causing many infections and cases of infection by from being in the same space with an individual or individuals without direct contact has been alarmingly increasing. Referring to COVID-19’s virulent propagation mechanism, it may be inadequately safe to maintain a distance of 1 to 2 m from an infected person to prevent infection, and frequent, effective ventilation is necessary to remove more virus particles. In this paper, a cafe was selected as a typical multi-use store. TRNSYS18 was used to compare and analyze the heating and cooling load values with the different types of ventilation methods. The analyses were: ventilation not performed, forced ventilation performed at 1500 CMH continuously for 24 hours (simple forced ventilation), forced ventilation according to the concentration of CO₂ (reasonable forced ventilation), ventilation using a crossflow plate, and rotary energy recovery ventilation. Compared to the reasonable forced ventilation, the plate and the rotary energy recovery ventilation showed reduction ratios of 6.3% and 20.9% respectively. The heating loads increased by 16.1 times for simple forced ventilation and 6.2 times for reasonable forced ventilation compared to when ventilation was not performed. Conversely, the plate and the rotary energy recovery ventilation showed an increase of approximately two times only.