Experimental performance of a solar air collector with a perforated back plate in New Zealand

This study investigates the thermal efficiency of a solar air heater (SAH), when it was mounted on a custom-made support frame, and was operated under different air mass flow rate. This SAH is composed of a transparent polycarbonate cover plate, a felt absorber layer, a perforated aluminium back plate and an aluminium frame. The ambient inlet air of this SAH is heated as it passes through the perforated back plate and over the felt absorber layer. The heated air is blown out through the outlet. Studies of SAHs with a similar design to this SAH were not found in the literature. The experiment was carried out at Massey University, Auckland campus, NZ (36.7◦ S, 174.7◦ E). The global horizontal solar irradiance, the ambient temperature and the wind speed were recorded using an on-site weather station. Temperature and velocity of the air at the outlet were measured using a hot wire anemometer. During the experiment, the air mass flow rate was between 0.022 ± 0.001 kg/s and 0.056 ± 0.005 kg/s. Results showed that when the SAH was operated at the airflow between 0.0054 kg/s and 0.0058 kg/s, the inlet air temperature and the wind speed (between 0 and 6.0 m/s) did not impact the temperature difference between the outlet air and the inlet air. The thermal efficiency of the SAH increased from 34 ± 5% at the airflow between 0.021 kg/s and 0.023 kg/s, to 47 ± 6% at the airflow ranging from 0.032 kg/s to 0.038 kg/s, to 71 ± 4% at the airflow of 0.056 ± 0.005 kg/s. The maximum thermal efficiency of 75% was obtained at the airflow of 0.057 kg/s. The effective efficiency of the SAH was 32 ± 5% at the airflow between 0.021 kg/s and 0.023 kg/s, 42 ± 6% at the airflow ranging from 0.032 kg/s to 0.038 kg/s, and 46 ± 11% at the airflow of 0.056 ± 0.005 kg/s

Heater choice, dampness and mould growth in 26 New Zealand homes: A study of propensity for mould growth using encapsulated fungal spores

The relationship between the use of unflued gas heaters (UGH, N = 14) and heat pump heaters (HP, N = 12) located in the living rooms, and mould growth on the living room and bedroom walls, of 26 New Zealand (NZ) occupied homes was investigated during winter. Two methods were employed to evaluate the potential of mould growth on walls: (i) measurement of daily hyphal growth rate using a fungal detector (encapsulated fungal spores); and (ii) estimation of fungal contamination based on a four level scale visual inspection. The average wall psychrometric conditions were significantly different between the two heater type groups, in both the living rooms and the bedrooms with the UGH user homes being colder and damper than HP user homes. The UGHs were found to be a significant additional source of moisture in the living rooms which dramatically increased the capacity for fungi to grow on wall surfaces. The average daily hyphal growth rates were 4 and 16 times higher in the living rooms and in the bedrooms of the UGH user homes, respectively. Results from both mould detection methods gave good agreement, showing that the use of a fungal detector was an efficient method to predict the potential of mould growth on the inside of the external walls in NZ homes

The effect of ventilation on air particulate matter in school classrooms

Health problems and respiratory diseases are associated with indoor air particulate matter (PM) mass. This is specially a concern in schools as children spend most of their time indoors. Understanding factors that affect PM mass such as occupant activities, ventilation and the infiltrating outdoor environment are important to safeguard occupant health. We investigated the air quality inside and outside two low decile primary school classrooms (children ages 7–9) over a three-week period during the southern hemisphere winter season in Palmerston North, New Zealand. Both classrooms were heated with wall mounted inverter heat pumps and in addition one classroom roof was fitted with a solar air heated ventilation unit (treatment). Particulate matter was continuously sampled and monitored to identify particles less than 10 µm in aerodynamic diameter (PM10) both outside and inside both classrooms to compare their indoor air quality. Significantly higher PM10 concentrations occurred within both classrooms during school hours (0845–1500), but the ventilated treatment classroom had PM10 concentrations on average 66% lower than those measured in the unventilated control classroom. Elemental composition and source apportionment of hourly samples showed that outdoor sources of PM10 infiltrated indoors, with similar contributions in both classrooms to those measured outdoors. However, the increased PM10 in the classrooms was predominantly from crustal sources, thought to be soil tracked in from outside on children's footwear and re-suspended during activities within the classrooms. Our results indicate that ventilation plays an important role in the quality of indoor air of classrooms and will contribute to the wellbeing of the students. In addition, there is a need to improve dust exposure mitigation strategies (carpet cleaning regime, dust reducing carpet) in classrooms fitted with carpets

Sources of indoor air pollution at a New Zealand urban primary school; a case study

Children are particularly vulnerable to the health effects of air pollution and as they spend a large proportion of time at school, this is an important environment for children's exposure to air pollution. Understanding the factors that influence indoor air quality in schools is critical for the assessment and control of indoor air pollution. This study analysed the concentration and sources of air pollution at an urban primary school (5–11 years) in Wellington, the capital of New Zealand. Over a three-week period during spring, indoor measures of particulate matter (PM 2.5 , PM 10 ), temperature, humidity, carbon dioxide (CO 2 ) and nitrogen dioxide (NO 2 ) were taken and hourly air particulate matter samples (PM 2.5 , PM 10-2.5 ) were collected inside and outside for elemental speciation analysis. Indoor PM 10 concentrations during the school day were significantly (p < 0.001) higher than outdoor concentrations 30.1 (range 10.0–75.0, SD 1.9) μg m −3 c.f. 8.9 (range <1.0–35.0, SD 6.8) μg m −3 . Elemental analysis and receptor modelling of PM samples showed that indoor PM 10 was primarily composed of crustal matter (soil) elements, possibly brought in on children's footwear. The primary driver of indoor PM 2.5 was from the infiltration of outdoor pollutants inside, with by-products of motor vehicle emissions the main contributor to indoor PM 2.5 . There is a need for mitigation strategies to reduce exposure to indoor air pollution at school, such as improved cleaning methods, reducing the use of carpet in schools and improved ventilation. The findings from this study will be applicable to many other schools and public buildings with high foot traffic

Low-cost Indoor Air Quality (IAQ) Platform for Healthier Classrooms in New Zealand: Engineering Issues

Providing a good quality classroom environment where children can breathe in fresh air is important. However, investigating the Indoor Air Quality (IAQ) in large numbers of classrooms is often too costly because currently available commercial brands are too expensive for the majority of schools. We have been developing a low-cost Indoor Air Quality (IAQ) platform called SKOMOBO which can monitor important IAQ parameters such as classroom temperature, relative humidly, particular matter and carbon dioxide level. Because our platform is designed in-house and utilizes low-cost sensors, there is a significant cost reduction and is affordable. In this paper, we discuss the design and implementation of SKOMOBO with the focus in several hardware and software engineering issues to explore the right set of strategies for developing a practical system. Through extensive experiments and evaluation, we have determined the various characteristic and issues associated with developing a low-cost sensor platform and their practical implications and mitigations

Integrating Open-Source Technologies to Build a School Indoor Air Quality Monitoring Box (SKOMOBO)

A low-cost, low power consumption indoor environment monitoring instrument, called SKOMOBO (school monitoring box), was developed and tested. SKOMOBO includes sensors to monitor temperature/relative humidity, carbon dioxide (CO2), particulate matter and motions. SKOMOBO was developed using the open source hardware Arduino Pro Mini. This paper describes the process of building SKOMOBO, including sensor selection, printed circuit board design, sensor programming and performance evaluation. Two co-located tests have been undertaken; one in the controlled environment and one in the uncontrolled environment. Results show SKOMOBO measurements have high correlations with their commercial equivalents. In the two different testing environments, the R2 of temperature measurements for all six SKOMOBOs were 1. The R2 for relative humidity and CO2 measurements were above 0.9. The result of this work shows the reliability of SKOMOBO on monitoring indoor air quality

Sources of nitrogen dioxide (NO₂) in New Zealand homes: findings from a community randomized controlled trial of heater substitutions

UNLABELLED: Houses in New Zealand have inadequate space heating and a third of households use unflued gas heaters. As part of a large community intervention trial to improve space heating, we replaced ineffective heaters with more effective, non-polluting heaters. This paper assesses the contribution of heating and household factors to indoor NO2 in almost 350 homes and reports on the reduction in NO2 levels due to heater replacement. Homes using unflued gas heaters had more than three times the level of NO2 in living rooms [geometric mean ratio (GMR) = 3.35, 95% CI: 2.83-3.96, P < 0.001] than homes without unflued gas heaters, whereas homes using gas stove-tops had significantly elevated living room NO2 levels (GMR = 1.42, 95% CI: 1.05-1.93, P = 0.02). Homes with heat pumps, flued gas heating, or enclosed wood burners had significantly lower levels of NO2 in living areas and bedrooms. In homes that used unflued gas heaters as their main form of heating at baseline, the intervention was associated with a two-third (67%) reduction in NO2 levels in living rooms, when compared with homes that continued to use unflued gas heaters. Reducing the use of unflued gas heating would substantially lower NO2 exposure in New Zealand homes. PRACTICAL IMPLICATIONS: Understanding the factors influencing indoor NO2 levels is critical for the assessment and control of indoor air pollution. This study found that homes that used unflued gas combustion appliances for heating and cooking had higher NO2 levels compared with homes where other fuels were used. These findings require institutional incentives to increase the use of more effective, less polluting fuels, particularly in the home environment

Deployment issues for integrated open-source-Based indoor air quality school Monitoring Box (SKOMOBO)

A low-cost, low power consumption indoor environment monitoring device, called SKOMOBO (SKOol Monitoring Box), was developed. SKOMOBO includes the sensors to monitor temperature/relative humidity, carbon dioxide, particulate matter (PM) and motion (PIR). SKOMOBO was developed using the open source software on Arduino Pro Mini. 165 units of SKOMOBO were manufactured at Massey University (New Zealand) in September 2017. These units were then deployed across New Zealand to monitor the indoor air quality in primary school classrooms. This paper describes the practical deployment issues we faced and lessons learnt prior/during the field study aimed at understanding the connection between the air quality and student performance. We believe that the discussion in this paper is of importance and could potentially save a lot of money and effort for other similar sensor products

The respiratory health effects of nitrogen dioxide in children with asthma

There is growing evidence that asthma symptoms can be aggravated or events triggered by exposure to indoor nitrogen dioxide (NO2) emitted from unflued gas heating. The impact of NO2 on the respiratory health of children with asthma was explored as a secondary analysis of a randomised community trial, involving 409 households during the winter period in 2006 (June to September). Geometric mean indoor NO2 levels were 11.4 μg·m-3, while outdoor NO2 levels were 7.4 μg·m-3. Higher indoor NO2 levels (per logged unit increase) were associated with greater daily reports of lower (mean ratio 14, 95% CI 1.12-1.16) and upper respiratory tract symptoms (mean ratio 1.03, 95% CI 1.00-1.05), more frequent cough and wheeze, and more frequent reliever use during the day, but had no effect on preventer use. Higher indoor NO2 levels (per logged unit increase) were associated with a decrease in morning (-17.25 mL, 95% CI -27.63- -6.68) and evening (-13.21, 95% CI -26.03- -0.38) forced expiratory volume in 1 s readings. Outdoor NO2 was not associated with respiratory tract symptoms, asthma symptoms, medication use or lung function measurements. These findings indicate that reducing NO2 exposure indoors is important in improving the respiratory health of children with asthma. Copyright©ERS 2011

Indoor air quality, largely neglected and in urgent need of a refresh

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