Passive cooling for air-conditioning energy savings with new radiative low-cost coatings

Passive cooling is considered as an alternative technology to avoid unwanted heat gains, to reduce urban heat islands and to generate cooling potential for buildings (limiting air-conditioning energy). According to materials and surface treatments, the roof can represent to be a major heat gain source from opaque elements of the building fabric, heating up the outer surface and increasing heat flow by conduction. This paper presents low-cost new radiative materials (1 ∉/m²) allowing to limit heat gains during diurnal cycle for hot seasons. To evaluate the relevance of these new substrates, their reflective UV-VIS-IR behavior are studied and compared to classical roofed materials available in industrial and developing countries. A 48 m² experimental roof having different surfaces (plate steel sheets, fiber cement, terra cotta tiles and corrugated sheets) allows to determine the temperature ratio δ between uncoated and coated materials. Up to 34% surface temperature gains are obtained for white coated CS, 25% for FC and ∼18% for TCT and PSS. According to uncoated materials for a surface temperature T₀ = 60 °C, simulations showed that the low-cost white opaque reflective roofs (50 m²) presented in this study would reduce cooling energy consumption by 26-49%.     

Thermal storage and nonlinear heat-transfer characteristics of PCM wallboard

For the materials with constant thermophysical properties, the thermal performance of wallboards (or floor, ceiling) can be described by decrement factor f and time lag φ. However, the phase change material (PCM) may charge large heat during the melting process and discharge large heat during the freezing process, which takes place at some certain temperature or a narrow temperature range. The behavior deviates a lot from the material with constant thermal physical properties. Therefore, it is not reasonable to analyze the thermal performance of PCM wallboard by using the decrement factor f and time lag φ. How to simply and effectively analyze the thermal performance of a PCM wallboard is an important problem. In order to analyze and evaluate the energy-efficient effects of the PCM wallboard and floor, two new parameters, i.e., modifying factor of the inner surface heat flux ‘α’ and ratio of the thermal storage ‘b’, are put forward. They can describe the thermal performance of PCM external and internal walls, respectively. The analysis and simulation methods are both applied to investigate the effects of different PCM thermophysical properties (heat of fusion H_m, melting temperature T_m and thermal conductivity k) on the thermal performance of PCM wallboard for the residential buildings. The results show that the PCM external wall can save more energy by increasing H_m, decreasing k and selecting proper T_m (α < 1); that the PCM internal wall can save more energy by increasing H_m and selecting appropriate T_m, k. The most energy-efficient approach of applying PCM in a solar house is to apply it in its internal wall.     

Method for achieving hydraulic balance in typical Chinese building heating systems by managing differential pressure and flow

Hydraulic unbalance is a common problem in Chinese district heating (DH) systems. Hydraulic unbalance has resulted in poor flow distribution among heating branches and overheating of apartments. Studies show that nearly 30% of the total heat supply is being wasted in Chinese DH systems due to a lack of pressure and flow control. This study investigated using pre-set radiator valves combined with differential pressure (DP) controllers to achieve hydraulic balance in building distribution systems, and consequently save energy and reduce the emissions. We considered a multi-storey building modelled in the IDA-ICE software, along with a self-developed mathematical hydraulic model to simulate its heat performance and hydraulic performance with various control scenarios. In contrast to the situation with no pressure or flow control, this solution achieves the required flow distribution and close-to-design room temperatures, as well as 16% heat savings, 74% pump electricity savings, and proper cooling of supply water. The energy consumption savings would therefore have positive environmental impacts, and be reflected in seasonal reductions of 2.1 kg/m² CO₂, 0.02 kg/m² SO₂, and 0.01 kg/m² NO_x for 3rd step energy efficiency buildings in Beijing.     

Influence of pH,salinity, and selenium on the growth of Aeromonas veronii in evaporation agricultural drainage water

Aeromonas veronii was isolated from seleniferous agricultural drainage water and characterized in terms of growth kinetics under changing environmental parameters [i.e. pH, selenium (Se) and salinity (electrical conductivity, EC)] that simulated evaporation. Aeromonas veronii metabolized peptone and was active in volatilizing Se, principally as dimethyl selenide (DMSe). Other volatile products produced included dimethyl disulfide, methyl selenol, dimethyl selenosulfide and dimethyl diselenide. The rate of Se volatilization correlated with the growth of A. veronii, with the highest levels of DMSe released during the exponential phase of growth. The C assimilated was primarily respired as CO₂ or incorporated into cell biomass with a small fraction used in the alkylation of Se. The maximum growth rate (μ_max) for A. veronii was 0.23 h⁻¹ at pH 7.94, 10 μg Se 1⁻¹, and EC of 3.9 dS m⁻¹ and decreased to 0.06 h⁻¹ with increasing salt content (40.2 dS m⁻¹), pH (8.53) and Se (500 μg l⁻¹). Salinity appeared to be the dominant inhibitory factor as observed by a decrease in growth rate and mass of cells. The range in salt content that was most inhibitory to the growth rate of A. veronii was from EC 11.7 to 40.2 dS m⁻¹. As drainage waters evaporate in holding facilities, salinity tends to increase having serious ecological effects on the growth of A. veronii.     

Annular denuder method for sampling reactive gases and aerosols in the atmosphere

The annular denuder method (ADM), consisting of a denuder-filter pack assembly, has been developed to measure several gaseous and aerosol species without sampling artifacts. Its application to the determination of gaseous acids and ammonia in the atmosphere indicates that this aim is achieved, even though the ratio of analytes in the gas phase and particulate matter is extremely low. The procedure is particularly suitable for the measurement of trace levels (0.1 μg m⁻³) of HNO₃ and SO₂ (even in the presence of high levels of sulfate and nitrate) as well as of HNO₂ (by making correction for the positive interference of NO₂ and PAN).The ADM sampling and analysis precision for the examined gases does not exceed ±10% in the 0.1–10 μg m⁻³ range. By sampling at an air flow rate of 151 min⁻¹, the minimum detectable atmospheric concentrations is ∼0.1 μgm⁻³ for each species over a 3 h interval.     

Thermal performance of caprylic acid/1-dodecanol eutectic mixture as phase change material (PCM)

Differential scanning calorimetry (DSC) is used to investigate the thermal properties of caprylic acid, 1-dodecanol and their binary system. The experimental results show that the caprylic acid/1-dodecanol binary system presents eutectic point. The eutectic melting temperature (T_em) is 6.52 °C, and the latent heat of melting of eutectic mixture (ΔH_em) is 171.06 J g⁻¹. The corresponding mass fraction of 1-dodecanol in eutectic mixture is 30%. The eutectic melting temperature and the latent heat of phase change of eutectic mixture have not obvious variations after 60 and 120 thermal cycles, which proves that the eutectic mixture has good thermal stability.     

Methane release rate and methanogenic bacterial populations in lake sediments

Methane release rates from the sediment in the lake were estimated by a batch culture. The methane release rates were decreased from 6.1 ± 0.7 mgCH₄-m⁻²-h⁻¹ at top 5 cm depth to 2.6 mgCH₄-m⁻²-h⁻¹ at 20–30 cm depth of sediments. Overall methane release rate from sediments was 19.9 mgCH₄-m⁻²-h⁻¹. The maximum specific acetate- and H₂-utilization rates, ν_m, were 5.2 × 10⁻⁵ to 7.96 × 10⁻⁶ and 0.9 × 10⁻⁵ to 1.0 × 10⁻⁴ gCOD-gVSS⁻¹-h⁻¹ for the sediments collected in the depths of sediments, respectively. The half-velocity constant, K_s, were from 21 to 65.5 and 27 to 194 mgCOD-1⁻¹ for acetate-and H₂-utilizing methanogens in the depths of sediments, respectively. The acetate-utilizing methanogens were enumerated by the most probable number (MPN) technique, and showed the number of acetate-utilizing methanogens increases as the ν_m increases. The populational distributions were 5.27 × 10⁸ to 2.8 × 10⁸, and 1.2 × 10⁸ MPN-gVSS⁻¹ at the sediments of top 20 and 20–30 cm, respectively. The specific methane production rates of sediments ranged from 1.2 × 10⁻¹¹ to 3.3 × 10⁻¹¹ mgCH₄-MPN⁻¹-h⁻¹ (average = 2.1 × 10⁻¹¹ mgCH₄-MPN⁻¹-h⁻¹) and are reasonably close to values reported in anaerobic treatment reactors and marine sediments. The sediment of top 20 cm had high microbial activity compared with the deeper section at 20–30 cm depth. In addition, the number of H₂-utilizing methanogens was smaller than that of acetate-utilizing methanogens in the sediments.     

Energy partition and conversion of solar and thermal radiation into sensible and latent heat in a greenhouse under arid conditions

For a greenhouse thermal analysis, it is essential to know the energy partition and the amount of solar and thermal radiation converted into sensible and latent heat in the greenhouse. Factors that are frequently needed are: efficiency of utilization of incident solar radiation (π), and sensible and latent heat factors (η and δ). Previous studies considered these factors as constant parameters. However, they depend on the environmental conditions inside and outside the greenhouse, plants and soil characteristics, and structure, orientation and location of the greenhouse. Moreover, these factors have not yet been evaluated under the arid climatic conditions of the Arabian Peninsula.In this study, simple energy balance equations were applied to investigate π, η and δ; energy partitioning among the greenhouse components; and conversion of solar and thermal radiation into sensible and latent heat. For this study, we used an evaporatively cooled, planted greenhouse with a floor area of 48 m². The parameters required for the analysis were measured on a sunny, hot summer day. The results showed that value of π was almost constant (≅0.75); whereas the values of η and δ strongly depended on the net radiation over the canopy (R_na); and could be represented by exponential decay functions of R_na.At a plant density corresponding to a leaf area index (LAI) of 3 and an integrated incident solar energy of 27.7 MJ m⁻² d⁻¹, the solar and thermal radiation utilized by the greenhouse components were 20.7 MJ m⁻² d⁻¹ and 3.74 MJ m⁻² d⁻¹, respectively. About 71% of the utilized radiation was converted to sensible heat and 29% was converted to latent heat absorbed by the inside air. Contributions of the floor, cover and plant surfaces on the sensible heat of the inside air were 38.6%, 48.2% and 13.2%, respectively.     

The use of Pb/210Pb ratios in lake sediments for estimating atmospheric fallout of stable lead in South-Central Ontario,Canada

The ratio of Pb concentrations (μg g⁻¹) to excess ²¹⁰Pb (²¹⁰Pb_exc) activities (dpm g⁻¹) in the surface (0–1 cm) sediments of lake cores, together with a knowledge of atmospheric ²¹⁰Pb fluxes, were used to estimate the atmospheric deposition of stable Pb in south-central Ontario, Canada. Between three and five cores were collected from each of 10 lakes, while in one lake (Red Chalk - Main Basin) a total of 25 cores were obtained.The average atmospheric ²¹⁰Pb_exc flux to the main basin of Red Chalk Lake was calculated to be 1.1 dpm cm⁻² year⁻¹, a value which compares favourably with literature estimates of ²¹⁰Pb deposition for Ontario. The surface Pb/²¹⁰Pb_exc ratios for 61 cores ranged between 1.26 and 3.44 μg dpm⁻¹(average 2.15 ± 0.45 μg dpm⁻¹). Therefore, the predicted atmospheric Pb deposition was 14–38 mg m⁻² year⁻¹ (average 24 ± 5.0 mg m⁻² year⁻¹). This estimate of stable Pb fallout is similar to those measured by alternate methods and indicates that elemental ratios in lake sediments might be useful for predicting the behaviour of other contaminants in lakes.     

Heat balance and tracer gas technique for airflow rates measurement and gaseous emissions quantification in naturally ventilated livestock buildings

Experiments were performed to study the airflow rates (AFRs) in a naturally ventilated building through four summer seasons and three winter seasons. The AFRs were determined using heat balance (HB), tracer gas technique (TGT) and CO₂-balance as averages of the values of all experiments carried out through the different seasons. The statistical analyses were correlation analysis, regression model and t-test. Continuous measurements of gaseous concentrations (NH₃, CH₄, CO₂ and N₂O) and temperatures inside and outside the building were performed. The HB showed slightly acceptable results through summer seasons and unsatisfactory results through winter seasons. The CO₂-balance showed unexpected high differences to the other methods in some cases. The TGT showed reliable results compared to HB and CO₂-balance. The AFRs, subject to TGT, were 0.12 m³ s⁻¹ m⁻², 1.15 m³ s⁻¹ cow⁻¹, 0.88 m³ s⁻¹ LU⁻¹, 56 h⁻¹, 395 m³ s⁻¹ and 470 kg s⁻¹ through summer seasons, and 0.08 m³ s⁻¹ m⁻², 0.83 m³ s⁻¹ cow⁻¹, 0.64 m³ s⁻¹ LU⁻¹ 39 h⁻¹, 275 m³ s⁻¹ and 328 kg s⁻¹ through winter seasons. The AFRs are not independent values, rather they were estimated for specific reference values, which are: area, cow and LU as well as rates. The emission rates through summer seasons, subject to TGT, were 9.4, 40, 3538 and 2.3 g h⁻¹ cow⁻¹; and through winter seasons were 4.8, 19, 2332 and 2.6 g h⁻¹ cow⁻¹, for NH₃, CH₄, CO₂ and N₂O, respectively.     

Convection from a cold window with simulated floor heating by means of a transiently heated flat unit

Windows play an important role in the energy performance of buildings. Measurements of the natural convection flow along a cold window surface have been carried our, in a climate chamber. A transient heating procedure was used, which was achieved by a heated flat unit placed horizontally below the window (similar to floor heating). The air temperature in the space outside the window was set to −12°C. The local Grashof number, Gr_x, ranged from 9.5 × 10⁷ to 3.0 × 10⁹. During heating, Gr_x was nearly unchanged at each measurement station along the window surface. The heating; procedure was found to have a negligible impact on the local heat transfer and on the distributions of velocity and dimensionless temperature in the near-window region. The local heat transfer data along the window surface are found to be correlated with Nu_x=0.0077 Gr_x^0.46. The mean convective heat transfer is discussed, and compared with previous results for the natural convection along a vertical plane or in an enclosure with different end temperatures. The velocity and temperature data show good agreement with power profiles, by modifying the characteristic scales that have been generally used for the natural convection boundary layer flow along a vertical flat plate. The results of the correlation and modification are presented.     

Acute toxicity tests with Daphnia magna straus and Pimephales promelas rafinesque in support of national pollutant discharge elimination permit requirements

The purpose of this study was to determine the static acute toxicity of aniline, p-chloro-m-cresol and 2(2,4,5-trichlorophenoxy) propionic acid (silvex) to daphnids (Daphnia magna) and bis(2-chloroethoxy)methane and 2-sec-butyl-4,6-dinitrophenol (dinoseb) to both daphnids and fathead minnows (Pimephales promelas). These data were needed to fulfill requirements established in the NPDES Permit (National Pollutant Discharge Elimination System) issued to the Michigan Division of The Dow Chemical Co. (Midland, Mich., U.S.A.) by the State of Michigan. Where appropriate, water quality-based effluent limitations could be recommended based on the acute toxicity data generated during this study. The results of the acute toxicity tests indicated that bis(2-chloroethoxy)methane was practically non-toxic to both daphnids and fathead minnows (LC₅₀ values of 201 and 184 mg l⁻¹, respectively); additionally, silvex was also found to be practically non-toxic to daphnids (LC₅₀ value > 140 mg l⁻¹). Aniline was highly toxic and p-chloro-m-cresol moderately toxic to daphnids, with calculated LC₅₀ values of 0.17 and 2.0 mg l⁻¹, respectively. Dinoseb was highly toxic both to daphnids and fathead minnows, with reported LC₅₀ values of 0.24 and 0.17 mg l⁻¹, respectively.     

Safe velocity of on-fire train running in the tunnel

The safety of a running train on fire in a tunnel is a key issue for rescue operations, and the train velocity is mainly related to its safety. In this study, the relationship between the wind velocity and heat release rate (HRR), temperature field around the train, and flame/smoke pervasion rule were investigated under the conditions of variable train velocity, fire location, and fire source location. Beijing Metro was considered as a typical example, in which the safe velocity was estimated to be ∼41.83 km h⁻¹. Assuming the occurrence of fire at the center of the train, the numerical simulations of the flow field using the sliding grid of CFD were performed for a full-scale tunnel under different HRRs. When the fire source reached to the target section, the velocities of all the monitoring points rapidly increased. The velocities increased as the train tail arrived at the target section. The velocities at the measuring points increased with the increase in height, excluding the value of the position with a distance of 0.025 m from the tunnel ceiling. The average temperature and concentration of smoke in the annular space between the train and tunnel ceiling had the minimum values when the running train on fire moved with a speed of 45 km h⁻¹. Thus, the safe velocity of a subway train on fire should be managed between 41.83 km h⁻¹ and 45 km h⁻¹.     

Light-scattering features of turbidity-causing particles in interconnected reservoir basins and a connecting stream

Light-scattering features of minerogenic particles in interconnected reservoir basins and a connecting stream in the watershed of New York City's water supply system, where these particles dominate scattering, were characterized by scanning electron microscopy interfaced with automated X-ray microanalysis and image analysis (SAX). SAX provided information on composition (in terms of elemental X-rays), shapes, number concentration, size distribution, and projected area concentration (PAV_m) of particle populations. Mie theory calculations based on SAX results were used to estimate the scattering coefficient and the mean scattering efficiency at a wavelength of 660 nm [b_m(660) and <Q_b,m(660)>]. Throughout the study system, nonspherical clay mineral particles in the 1-10 μm size range dominated PAV_m, light scattering and its surrogate, nephelometric turbidity (T_n). Patterns of particle size contributions to b_m(660) (and T_n) remained relatively invariant over a wide range of T_n (more than 200-fold difference). The median size for these contributions was most often ∼2.5 μm. The credibility of the SAX characterizations of the light-scattering features of the minerogenic particles and the calculations based on Mie theory for the study system was supported by (1) the strength of the T_n-PAV_m relationship, (2) the reasonable closure between T_n measurements and calculated values of b_m(660), and (3) the closeness of <Q_b,m(660)> to the limiting value of 2 for polydispersed particle populations. Upstream sources of turbidity-causing particles within the study system were demonstrated to have highly similar light-scattering features. This indicates similar potencies for the particle populations from these sources for turbidity impacts in downstream waters and supports the direct incorporation of T_n measurements into loading calculations to evaluate relative contributions of these inputs with respect to such impacts.     

Limits and potentials of office building climatisation with ambient air

One of the first passive energy standard office buildings in Europe was extensively monitored over 3 years to analyse the summer performance of highly insulated, well sun-shaded and mechanically ventilated buildings. During typical German summer conditions with less than 160 hours ambient air temperatures above 25 $°$C, these buildings perform excellently during summer, even if the internal loads are rather high with 200–400 Wh m⁻² day⁻¹. If ambient air temperatures are significantly higher like in summer 2003 with more than 3 K higher average temperatures than usual, nearly 10% of all office hours are above 26 $°$C. Detailed measurements showed that the night discharging of heavy thermal masses such as the concrete ceiling was not always effective under free convection conditions. Room air temperature decreased by 2–3 K only although measured night air changes were always above 5 h⁻¹. The measured air change rates contained not only cool ambient air but also backflow of warmer air from the corridors, which could be shown by flow visualisation in the rooms and by simulation studies. Improvements to the night ventilation performance can be achieved, if early evening ventilation with high heat gains can be reduced and if fans support the air exchange in the cooler morning hours.Three year measurements and simulation of the earth heat exchanger showed that excellent performance is achieved with COP’s between 35 and 50. Due to the limited fresh air volume flow in such buildings, the earth heat exchanger only removes a fraction of the loads, here about 18% of the total internal loads.     

A parameterization of dust concentration (PM₁₀) of dust events observed at Erdene in Mongolia using the monitored tower data

Hourly mean time series of dust concentration (PM₁₀) measured at 3 m high and a sonic-anemometer measured momentum and kinematic heat fluxes at 8 m high above the surface have been obtained from a 20-m monitoring tower located at Erdene in the Asian dust source region of Mongolia for years of 2009 and 2010. These time series were used to identify dust events and to develop optimal regression equations for the dust concentration of dust events with the friction velocity (u_*) and the convective velocity scale (w_*). In total, 68 dust events were identified in 2009 (except for November) and 43 dust events for the period from March to August in 2010. The duration of each dust event ranged from 3-29 h in 2009 and 5-35 h in 2010. The maximum hourly mean dust concentration of the dust event was found to be 4,107 μg m^− 3 in May in 2009 and 4,708 μg m^− 3 in March in 2010 while a minimum of 251 μg m^− 3 in August in 2009 and 662 μg m^− 3 in June in 2010. The optimal regression equation for the dust concentration (C) of dust events was found to have the form of log C = a + b(u_* + cw_*)ⁿ, where a, b, c and n are constants that vary month to month. The convective velocity scale (w_*) that has not been taken into account in most dust modelings was found to enhance the dust concentration of dust events during the cold period from December to March when the soil temperature was below the freezing level for both the stable (w_* < 0) and unstable (w_* > 0) stratifications, whereas the convective velocity caused a reduction in the dust concentrations during the warm period from April to October, suggesting the importance of the convective velocity to estimate dust concentration of dust events.     

Nitrification in porous media during rapid,unsaturated water flow

A substantial nitrification in rapid infiltration (RI) systems for wastewater treatment is a prerequisite for obtaining good N removal by denitrification. The purpose of this study is to investigate nitrification in porous media at conditions corresponding to RI treatment systems. Nitrification in six 50-cm porous media columns (98% weathered granite or sand and 2% field soil) during unsaturated leaching at constant flow rates of synthetic wastewater was investigated. Concentrations of NH₄-N between 20 and 60 mg l⁻¹ were applied and vertical concentration profiles of NO₃-N, NO₂-N and NH₄-N were measured for 54 d at 30°C (three columns) and for 140 d at 10°C (three columns). A time lag in nitrification of 20 d was found at 10°C. Complete nitrification was obtained after 3–5 at 30°C and after approximately 50 d at 10°C. Assuming first-order nitrification at steady-state, the corresponding first order reaction rate coefficients (k₁) for NO₃ production in the columns were estimated to be between 0.4 and 1 h⁻¹ at 10°C and between 6 and 9 h⁻¹ at 30°C. Steady-state NO₃ profiles were obtained between 1.5 and up to 9 weeks after the experiments were started. At the actual soil-air contents (0.10 cm³ air phase cm⁻³ soil), oxygen limitations were not observed during the experiments. Nitrogen loadings (water flow times N concentration) above 100 mg N 1⁻¹ cm h⁻¹ (1 g N m⁻² h⁻¹) caused NH₄ accumulation in the columns at 10°C and should probably be avoided during operation of RI system.     

Using SWAT, Bacteroidales microbial source tracking markers,and fecal indicator bacteria to predict waterborne pathogen occurrence in an agricultural watershed

Developing the capability to predict pathogens in surface water is important for reducing the risk that such organisms pose to human health. In this study, three primary data source scenarios (measured stream flow and water quality, modelled stream flow and water quality, and host-associated Bacteroidales) are investigated within a Classification and Regression Tree Analysis (CART) framework for classifying pathogen (Escherichia coli 0157:H7, Salmonella, Campylobacter, Cryptosporidium, and Giardia) presence and absence (P/A) for a 178 km² agricultural watershed. To provide modelled data, a Soil Water Assessment Tool (SWAT) model was developed to predict stream flow, total suspended solids (TSS), total N and total P, and fecal indicator bacteria loads; however, the model was only successful for flow and total N and total P simulations, and did not accurately simulate TSS and indicator bacteria transport. Also, the SWAT model was not sensitive to an observed reduction in the cattle population within the watershed that may have resulted in significant reduction in E. coli concentrations and Salmonella detections. Results show that when combined with air temperature and precipitation, SWAT modelled stream flow and total P concentrations were useful for classifying pathogen P/A using CART methodology. From a suite of host-associated Bacteroidales markers used as independent variables in CART analysis, the ruminant marker was found to be the best initial classifier of pathogen P/A. Of the measured sources of independent variables, air temperature, precipitation, stream flow, and total P were found to be the most important variables for classifying pathogen P/A. Results indicate a close relationship between cattle pollution and pathogen occurrence in this watershed, and an especially strong link between the cattle population and Salmonella detections.