High resolution modeling of the effects of alternative fuels use on urban air quality: Introduction of natural gas vehicles in Barcelona and Madrid Greater Areas (Spain)

The mitigation of the effects of on-road traffic emissions on urban air pollution is currently an environmental challenge. Air quality modeling has become a powerful tool to design environment-related strategies. A wide range of options is being proposed; such as the introduction of natural gas vehicles (NGV), biofuels or hydrogen vehicles. The impacts on air quality of introducing specific NGV fleets in Barcelona and Madrid (Spain) are assessed by means of the WRF-ARW/HERMES/CMAQ modeling system with high spatial-temporal resolution (1 km², 1 h). Seven emissions scenarios are defined taking into account the year 2004 vehicle fleet composition of the study areas and groups of vehicles susceptible of change under a realistic perspective. O₃ average concentration rises up to 1.3% in Barcelona and up to 2.5% in Madrid when introducing the emissions scenarios, due to the NO_x reduction in VOC-controlled areas. Nevertheless, NO₂, PM10 and SO₂ average concentrations decrease, up to 6.1%, 1.5% and 6.6% in Barcelona and up to 20.6%, 8.7% and 14.9% in Madrid, respectively. Concerning SO₂ and PM10 reductions the most effective single scenario is the introduction of 50% of NGV instead of the oldest commercial vehicles; it also reduces NO₂ concentrations in Barcelona, however in Madrid lower levels are attained when substituting 10% of the private cars. This work introduces the WRF-ARW/HERMES/CMAQ modeling system as a useful management tool and proves that the air quality improvement plans must be designed considering the local characteristics.     

大力发展和推广应用天然气汽车

本文从改善能源结构,治理汽车尾气污染阐述了发展天然气汽车的意义,简介了天然气汽车经济效益、应用技术及发展前景。     

The environmental effects of the CNG bus program on metropolitan air quality in Korea

This study aims to analyze the effectiveness of the compressed natural gas (CNG) bus program on air quality in seven metropolitan cities in Korea. Two hundred and fifty-nine cases from monthly panel data covering June 2005 to June 2008 were analyzed. Natural and sociological characteristics in each city were included as control variables. The Chinese Air Pollution Index was also considered based on previous studies demonstrating that air quality in Korea is adversely affected by transboundary pollution from China. The relationship between five air pollutants (SO₂, NO₂, O₃, CO, and PM₁₀) and the CNG bus ratio was analyzed by panel data analysis. The key findings are as follows. CO and PM₁₀ significantly decrease with an increase in the CNG bus ratio. On the other hand, SO₂ and NO₂ demonstrate no statistically significant relationship with CNG bus ratio, while O₃ appears to have a slightly positive relationship. In addition, the results indicate that air pollution from China contributes to the increase in PM₁₀ and O₃ in Korea approximately at the threshold of 100 in Chinese Air Pollution Index. Even though introducing CNG buses can reduce the level of PM₁₀, it might be also increased due to the pollutants from China.     

正确处理天然气质量中的燃气互换性问题(第二部分)

4 当前欧洲国家燃气质量状况 欧洲国家当前迫切需要为解决天然气的跨境输送、联网而形成一个毋需转换而各国管网可以接受的天然气质量标准.     

浅析CNG汽车及液压式加气子站在石家庄市的应用和发展

1汽车尾气已成为城市空气的主要污染源 近几年来，我国进入城市化高速发展时期，城市建设飞速发展，城市面积扩大、人口增长，道路建设加快，公交车与出租车的需求量上升。由此引起的机动车排气污染也呈上升势头。     

长治市人工煤气-天然(煤层)气转换实践

1 引言。长治市管道煤气工程于1992年建成投产,经过十多年的规模发展,拥有民用户4．8万户．营业公福用户104户,工业用户4户,锅炉15户。日均用气量8万m^3,冬季高峰用气量达13万m^3,形成两座3万m^3储气柜,42座区域和专用调压站,230余km中低压管道的城市供气规模。目前,用气规模已超过设计能力3．5万户的37％,冬季高峰用气量已接近设计外供气能力的极限值,小马拉大车的矛盾非常突出．用户发展受到很大限制,甚至确保当前用户的安全稳定供气也日趋艰难。因此,积极探求新气源,彻底缓解供气紧张的严重局面,成为长治燃气发展的重中之重。在国家西气东输工程暂不向山西省供气情况下,2002年6月,长治煤气化总公司领导多方外出考察调研,经认真研究,以及中国市政工程华北设计院进行技术上充分论证后,果断决策．决定采用先进的集束式撬车运输新技术,引进天然(煤层)气,以缓解长治市燃气气源日趋紧张的状况,同时进一步优化长治城市燃气结构,提高城市品位,改善居民生活质量。     

浅谈城市天然气居民用户气量预测

通过介绍居民用气量计算公式中用气量指标及气化率两个不确定参数的影响因素,阐述了居民用气量预测的难度及重要性,旨在通过分析掌握居民用气指标和用气规律,从而准确预测居民用气量。     

Indoor air quality in new and renovated low-income apartments with mechanical ventilation and natural gas cooking in California

This paper presents pollutant concentrations and performance data for code-required mechanical ventilation equipment in 23 low-income apartments at 4 properties constructed or renovated 2013-2017. All apartments had natural gas cooking burners. Occupants pledged to not use windows for ventilation during the study but several did. Measured airflows of range hoods and bathroom exhaust fans were lower than product specifications. Only eight apartments operationally met all ventilation code requirements. Pollutants measured over one week in each apartment included time-resolved fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), formaldehyde and carbon dioxide (CO₂) and time-integrated formaldehyde, NO₂ and nitrogen oxides (NO_X). Compared to a recent study of California houses with code-compliant ventilation, apartments were smaller, had fewer occupants, higher densities, and higher mechanical ventilation rates. Mean PM_2.5, formaldehyde, NO₂, and CO₂ were 7.7 µg/m³, 14.1, 18.8, and 741 ppm in apartments; these are 4% lower, 25% lower, 165% higher, and 18% higher compared to houses with similar cooking frequency. Four apartments had weekly PM_2.5 above the California annual outdoor standard of 12 µg/m³ and also discrete days above the World Health Organization 24-hour guideline of 25 µg/m³. Two apartments had weekly NO₂ above the California annual outdoor standard of 30 ppb.     

An innovative power pack and motor for a compressed air car of practical performance

SYNOPSIS

Much more attention is now being paid to local air pollution levels in Europe and America, led by the California Air Resources Board (CARB) who have pronounced that a given percentage of cars sold in that State must be zero emission by a certain date [1]. The obvious contender to fulfil such a requirement is the electric driven vehicle, but manufacturers are having problems producing a reliable battery of sufficient energy density.

Do compressed air driven cars represent a viable alternative? Their advantage is the long life of the power pack and the relatively high speed recharging, which must be set against their greater capital cost. The authors show that the pneumatic car can certainly equal the performance of electric transportation when use is made of modern materials and energy recovery through the utilisation of heat pipes, and conclude that they are indeed worthy of further investigation.     

The use of moments for assessing air quality in ventilated rooms

A comprehensive theoretical framework is presented, based on the use of moments of concentration histories, i.e. multiplying concentration readings by time of reading and then integrating with regard to time. The concept is applicable to characterize either the diffusion of the supplied air or a contaminant released within the room. Results are presented from about 50 measurements demonstrating the usefulness and practical applicability of the approach for assessing air quality in ventilated buildings. Different experimental procedures have been explored and are discussed.     

Investigations on air pressure and air losses in compressed air tunneling through saturated clayey soil

Determination of air pressure and assessment of air losses in clayey soil are of great importance to implementation of compressed air tunneling. In the present work, a series of air flow tests were performed to provide a more reasonable method based on flow characteristics of snap-off pressure and the dissolution/diffusion. Results showed that, the nonlinear air flow behavior and gas breakthrough were presented with the increase in air pressure. After that, the excessive pressure decreased continuously to reach an equilibrium termed as the snap-off. For the tested clayey soil, snap-off pressures around 250 kPa could be adopted as the air pressure, which was significantly lower than the gas breakthrough pressures. Diffusion coefficient of 1.5 × 10^-11 m²/s could be determined in the followed dissolution/diffusion stage, which bring 3 orders of decreasing magnitude in air losses compared to the capillary flow occurred after gas breakthrough. As a conclusion, the adoption of snap-off pressure in compressed air tunneling could effectively prevent the continuous air/water flow in clayey soil and create a more human-friendly environment. Additionally, less air losses could be presented compared to that using gas breakthrough pressure, indicating tremendous energy savings in field implementation.     

The effect of environmental and structural factors on indoor air quality of apartments in Korea

The indoor air quality (IAQ) was measured in newly built Korean apartments before and after occupancy in a survey of 158 residences in 24-apartment complexes nationwide. Factors that might affect pollutant concentration, such as temperature, humidity, housing size, and duration of occupancy, were analyzed in relation to the measured concentrations. Average pollutant levels were consistent with the Ministry of the Environment's recommended standards; however, pollutant levels in some apartments exceeded the current standards. We found that the concentrations of formaldehyde and toluene often exceeded the more stringent guidelines that will soon be enacted. Our results suggest that stronger countermeasures are therefore required to control these two chemicals. The results show that the pollution concentration was generally proportional to temperature and humidity, but that, in some cases, the concentration measurements were inversely proportional to these two factors, and in a few others the relationship between these factors was not clear. Indoor air pollution readings were highest in the 30-pyeong apartments, followed by 10-, and 20-pyeong residences. The pollutant concentrations decreased to about half of their initial levels after one year of occupancy, but the concentration of formaldehyde in indoor air persisted for a longer period. The duration of the apartment's occupancy affected indoor air pollutant concentrations more so than other factors such as temperature, humidity, and apartment size.     

Emissions variation in urban areas resulting from the introduction of natural gas vehicles: Application to Barcelona and Madrid Greater Areas (Spain)

On-road traffic is the major contributor to pollutant emissions in urban areas. Nowadays different emission abatement strategies are being tested in order to improve urban air quality (e.g. the European Commission currently promotes the use of natural gas as an alternative fuel). Several feasible scenarios regarding the introduction of natural gas vehicles (NGV) are studied in the two main cities of Spain (Barcelona and Madrid) by using the HERMES emission model. The most suitable emission factors to NGV are selected among those available in the literature. The account of emissions in the base case scenario estimated for a typical summertime polluted day of the year 2004 reflects that in Barcelona 86% of primary pollutants come from on-road traffic compared to 93% in Madrid, because of the heavier industrial activity in the former. The introduction of NGV in urban zones would have a positive effect on emissions, whose extent largely depends on the substituted fleets and the conurbation characteristics. Maximum reductions in NO_x emissions in Madrid are attributed to the substitution of 10% of the oldest diesel and petrol cars, while in Barcelona the change of 50% of the oldest commercial light vehicles becomes more effective. PM_2.5 and SO₂ emissions can be significatively reduced with the introduction of NGV instead of the oldest commercial light vehicles. The substitution of conventional fuels by natural gas must reach around 4% to achieve significative reductions in traffic emissions (larger than 5%). This work focuses on air quality issues, therefore GHG emissions are not included, nevertheless this kind of associated impact has to be considered by the decision makers. Assessing the efficacy of environmental improvement strategies entails a realistic design of emission scenarios and their evaluation. The detailed emission account provides a fundamental basis for the air quality modelling and its comparison among scenarios.     

The impact of biogas and fuelwood use on institutional kitchen air quality in Kampala,Uganda

Experts have suggested that microscale biogas systems offer a source of renewable energy that improves indoor air quality, but such impacts have not been directly measured. This study documented cooking behaviors and measured 2.5‐μm particulate matter (PM_2.5), carbon monoxide (CO), and sulfur dioxide (SO₂) concentrations within 14 institutional kitchens in Kampala, Uganda, that prepare meals using biogas (n=5), a mixture of biogas and fuelwood (n=3), and fuelwood (n=6). Small institutions (10‐30 people) with biogas kitchens had 99% lower concentrations of PM_2.5 (21 μg/m³) than fuelwood kitchens (3100 μg/m³). Larger institutions (>100 people) had biogas systems that produced insufficient gas and relied on fuelwood to meet over 90% of their energy needs. PM_2.5 concentrations in these biogas‐firewood kitchens were equivalent to concentrations in fuelwood kitchens. Although concentrations of hydrogen sulfide (H₂S) in biogas were as high as 2000 ppm, 75% of systems had undetectable H₂S levels (<100 ppm) in the biogas. Kitchens using biogas with high H₂S had correspondingly higher SO₂ concentrations in the kitchen air. However, even the highest SO₂ concentration in biogas kitchens (150 μg/m³) was lower than SO₂ concentration in fuelwood kitchens (390 μg/m³). The results suggest that biogas systems can offer air quality improvements if sized properly for energy demands.     

The effect of a photocatalytic air purifier on indoor air quality quantified using different measuring methods

The effect on indoor air quality of an air purifier based on photocatalytic oxidation (PCO) was determined by different measuring techniques: sensory assessments of air quality made by human subjects, Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) and chromatographic methods (Gas Chromatography/Mass Spectrometry and High-Pressure Liquid Chromatography with UV detection). The experiment was conducted in a simulated office, ventilated with 0.6 h⁻¹, 2.5 h⁻¹ and 6 h⁻¹, in the presence of additional pollution sources (carpet, chipboard and linoleum). At the lowest air change rate, additional measurements were made with no pollution sources present in the office. All conditions were tested with the photocatalytic air purifier turned on and off. The results show that operation of the air purifier in the presence of pollutants emitted by building materials and furniture improves indoor air quality, as documented by sensory assessments made by human subjects. It also reduces concentrations of many chemical compounds present in the air as documented by the PTR-MS technique. For the lowest ventilation, results from measurements using the chromatographic methods have similar tendency, however many of the 50 compounds that were targeted for analysis were not detected at all, independent of whether the purifier was on or off. For the two conditions with higher ventilation the results were inconclusive.     

Risk analysis of LPG (liquefied petroleum gas) vehicles in enclosed car parks

A risk analysis is presented for an enclosed 30×30 m car park in which LPG (liquefied petroleum gas) vehicles are allowed to park. An event tree analysis is used to define 26 different incident scenarios and their probabilities. FLACS, a specialised CFD program, is used to calculate the formation of a flammable vapour cloud and its dilution by means of the ventilation system as well as the overpressures generated in a vapour cloud explosion. Existing empirical methods are used to calculate the overpressures generated by a BLEVE and the heat radiated by a fire ball and a jet fire. The simulations have shown that a release from a 70 l LPG fuel tank can lead to vapour clouds of up to 200 m³ that fill the entire height of the car park, while the explosion simulations have shown that such vapour clouds can lead to overpressures above 30 kPa in the entire car park. The ventilation simulations have shown that high flow rates of approximately 0.060 m³/s per m² of car park floor area are necessary to rapidly dilute these large vapour clouds.     

The effect of an ion generator on indoor air quality in a residential room

Ion generators charge particles with a corona prior to their removal on collector plates or indoor surfaces and also emit ozone, which can react with terpenes to yield secondary organic aerosol, carbonyls, carboxylic acids, and free radicals. This study characterized the indoor air quality implications of operating an ion generator in a 27 m(3) residential room, with four different test room configurations. Two room configurations had carpet overlaying the original flooring of stained/sealed concrete, and for one configuration with and without carpet, a plug-in air freshener was used as a terpene source. Measurements included airborne sampling of particulate matter (0.015-20 μm), terpenes and C(1) -C(4) and C(6) -C(10) aldehydes, ozone concentrations, and air exchange rates. When the heating, ventilating, and air-conditioning system was not operating (room air exchange rate = ～0.5/h), the use of the ion generator in the presence of the air freshener led to a net increase in ultrafine particles (<0.1 μm). Also, increased concentrations of ozone were observed regardless of air freshener presence, as well as increases in formaldehyde and nonanal, albeit within measurement uncertainty in some cases. Thus, it may be prudent to limit ion generator use indoors until evidence of safety can be ascertained. PRACTICAL IMPLICATIONS: Portable ion generators are intended to clean the air of particles, but they may emit ozone as a byproduct of their operation, which has the potential to degrade indoor air quality. This study showed that under certain conditions in a residential room, the use of a portable ion generator can increase concentrations of ozone and, to a lesser degree, potentially aldehydes. Also, if operated in the presence of a plug-in air freshener that emits terpenes, its use can increase concentrations of secondary organic aerosol in the ultrafine size range.     

The effect of structures on indoor humidity--possibility to improve comfort and perceived air quality

The research presented in this paper shows that moisture transfer between indoor air and hygroscopic building structures can generally improve indoor humidity conditions. This is important because the literature shows that indoor humidity has a significant effect on occupant comfort, perceived air quality (PAQ), occupant health, building durability, material emissions, and energy consumption. Therefore, it appears possible to improve the quality of life of occupants when appropriately applying hygroscopic wood-based materials. The paper concentrates on the numerical investigation of a bedroom in a wooden building located in four European countries (Finland, Belgium, Germany, and Italy). The results show that moisture transfer between indoor air and the hygroscopic structure significantly reduces the peak indoor humidity. Based on correlations from the literature, which quantify the effect of temperature and humidity on comfort and PAQ for sedentary adults, hygroscopic structures can improve indoor comfort and air quality. In all the investigated climates, it is possible to improve the indoor conditions such that, as many as 10 more people of 100 are satisfied with the thermal comfort conditions (warm respiratory comfort) at the end of occupation. Similarly, the percent dissatisfied with PAQ can be 25% lower in the morning when permeable and hygroscopic structures are applied.