Sunny Summer Days Research Articles

Erratum to: Comparative analysis of the soil thermal regimes of typical underlying surfaces of oasis systems in an Arid Region

Using supplementary observational data obtained from the “Oasis System Energy and Water Cycle Field Experiment” conducted in the summer of 2005 and 2008, we performed a comparative analysis of the characteristics of soil thermal regimes of an Oasis and the Gobi in terms of the surface albedo, soil temperature gradient, soil heat flux and soil thermal conductivity. The results showed that on sunny summer days, the daily average albedos of the Gobi and Oasis were 0.215, 0.159 in 2005 and 0.207, 0.150 in 2008, respectively. The soil temperature gradient and the net radiation showed an approximate linear relationship; the soil temperature gradient decreased with the increase of net radiation and it declined faster when the net radiation was negative. The soil heat flux of the 0.05 m soil layer varied in phase with the soil heat flux of the 0.20 m layer of soil. The thermal conductivity values of the 0.05 m layer of the Gobi and Oasis soil were 0.193 and 0.374 W m−1 K−1. The soil heat flux can be well estimated using soil temperature gradient and soil thermal conductivity from observation in the Gobi.

Diurnal Variations of Surface Wind Speed Observed in the Mountainous Area of Central Japan during Sunny Summer Days

Diurnal Variations of Surface Wind Speed Observed in the Mountainous Area of Central Japan during Sunny Summer Days

長期間運用を想定したヒートポンプ給湯器による太陽光発電システムの電圧上昇抑制効果

SUMMARY There is a danger of output suppression of high-penetration residential photovoltaic systems due to voltage increase. It is necessa1ry to install new technology to prevent the occurrence of such phenomenon. Therefore, we focused our attention on heat-pump water heaters (HPWHs). HPWHs are usually used to heat water during nighttime because electricity prices are cheaper than during the daytime for the load leveling in Japan. So they can be used as a countermeasure without additional cost if they are operated during the daytime. However, HPWHs do not have sufficient capacity to absorb inverse energy at each residence. Thus, HPWH operation must be optimized to minimize output suppression loss. In this research, we selected four typical sunny days in spring, summer, autumn, and winter. The optimal HPWH operation was calculated by numerical simulation. The optimal monthly HPWH operation was investigated using the weather forecast assuming actual operation in each season.

Source identification of bacterial and viral pathogens and their survival/fading in the process of wastewater treatment, reclamation, and environmental reuse.

Pathogenic safety is drawing wide concern in water reclamation and reuse. In order to elucidate survive/fade of pathogens during the processes of wastewater treatment and reclamation, general indicators (fecal coliform and Escherichia coli), pathogenic bacteria (Salmonella and Shigella) and viruses (enterovirus, rotavirus and norovirus) were investigated in an A(2)O-MBR system. Attention was paid to their strengths from different sources, at various stages of the treatment, and in the product water. According to findings, black water was the main source for pathogens-at least 1-2-log higher in concentration than those from other sources. The preliminary treatment of wastewater by fine screens could bring about 0.2-0.4-log removal for almost all pathogens. The biological treatment units achieved almost identical removal (1.3-1.7-log) for bacteria and viruses. However, subsequent treatment in the membrane bioreactor showed varied removal for fecal coliform (4.7-log), E. coli (2.6-log) and the other pathogens (0.7-1.0-log), indicating that a high reduction of indicator bacteria may not imply equivalent removal of bacterial and viral pathogens. Chlorination was proved to be effective for eliminating all pathogens. In the artificial lake where the product water was stored, fecal coliform was not detected during the study period, but E. coli and pathogens were frequently detected, indicating that these bacterial and viral pathogens may be originating from non-fecal sources. On sunny summer days, the lake water could be bacteria-free due to sunlight radiation, but viruses were still detectable. Therefore, secondary disinfection may have to be adopted when the reclaimed water stored in such an open reservoir is supplied for strict reuse purposes.

Comparative study on the dynamic heat transfer characteristics of PCM-filled glass window and hollow glass window

In order to determine the effects of the phase change material filled glass window (PCMW) on building energy consumption in the hot summer and cold winter area of China, dynamic heat transfer process and heat transfer parameters of the PCMW and the hollow glass window (HW) exposed to different non-steady boundary conditions related to the climatic characteristic were investigated. The experiments and the numerical simulations in a representative sunny summer day were conducted, and the results were in good agreement. Then the validated numerical model was used to simulate the dynamic heat transfer processes of the two kinds of windows at more different weathers, the temperature and heat flux fluctuations on the interior surfaces were analyzed based on simulation results. It was concluded that in the representative sunny summer day, the peak temperature on the interior surface of the PCMW reduced by 10.2°C, and the heat entered the building through the PCMW reduced by 39.5%, comparing with the HW. However, in the other representative days, the dynamic thermal performance of the PCMW was unsatisfactory as it cannot decrease the building energy consumption. The annual energy consumption of the air conditioning system and the heating system because of the heat transferred though the PCMW decreased 40.6% comparing with the HW applied.

Development and modelling of a solar assisted liquid desiccant dehumidification air-conditioning system

This paper presents the development and simulation of an advanced solar assisted liquid desiccant dehumidification air-conditioning system for energy efficiency and sustainability. The system is mainly designed to cut down building electricity consumption while providing satisfied indoor thermal comfort. It includes a counter flow packed bed absorber, a counter flow packed bed regenerator, and an array of flat plate solar collectors. The system is integrated with an evaporative cooler and a cooling tower to cool the processed air and the strong desiccant solution, respectively. A whole system simulation is used to evaluate the system performance by using a full-scale simulation system developed on the basis of Matlab Simulink platform. The simulation results based on three consecutive sunny summer days in Sydney show that the proposed system can achieve an average daily thermal coefficient of performance of 0.5-0.55, and 73.4% of thermal energy required for thermal regeneration was provided by the solar collectors. It is expected that the average daily thermal coefficient of performance could be higher during other mild summer days as the percentage of thermal energy provided by the solar water heating system will increase due to the relatively low cooling demand of the building.

Building thermal-insulation effect on ambient and indoor thermal performance of green roofs

Building thermal insulation (BTI) may influence indoor cooling by green roofs. The hypothesis that buildings with poor BTI may benefit more from green-roof passive cooling is tested. An experiment was designed in humid-tropical Hong Kong to investigate two BTI states (good and poor) and three treatment plots (control-bare, succulent Mexican Sedum, and broadleaved Perennial Peanut). Temperature sensors were installed along a holistic vertical profile from outdoor air to green-roof layers and indoor ceiling and air. On summer-sunny day, poorly-insulated control roof allows notable daytime peak thermal intrusion, counterpoised by comparable nocturnal thermal discharge. It is the only roof with bidirectional heat fluxes and nearly-balanced diurnal heat-energy budget. Other roofs are predominantly unidirectional (downward) with considerable indoor heat gain. Well-insulated control roof experiences extended (morning to night) thermal intrusion, with depressed but delayed and prolonged heat influx, and thermal insulation breaching. At night time, it creates nocturnal thermal barrier to reduce heat escape from indoor space. Simple Sedum green roof on poorly-insulated roof establishes green-roof heat-sink effect to incur daytime and nocturnal aggravated thermal intrusion. On well-insulated roof, it generates a synergistic-dual thermal barrier to suppress thermal insulation breaching. However, nocturnal thermal discharge has been constrained by persistent positive thermal gradient throughout the day. Thicker and more-elaborate Peanut green roof brings considerable evapotranspiration cooling and synergistic-dual thermal barrier to generate daytime subdued thermal intrusion and mask inherent BTI-differences. As omission of BTI for both Sedum and Peanut green roofs does not earn more indoor cooling, the hypothesis cannot be accepted. To optimize passive cooling, green roofs with thicker substrate and denser foliage should be installed on buildings with good BTI.

Influence of canopy structural characteristics on cooling and humidifying effects of Populus tomentosa community on calm sunny summer days

The measurements of air temperature, relative humidity, and canopy structural characteristics were performed on calm sunny summer days in the Populus tomentosa community and the sun in the Beijing Olympic Forest Park, China. The aim of this study was to investigate in detail the correlations between the detailed cooling and humidifying effects and the canopy structural characteristics of the community. Hourly values of air temperature and relative humidity, canopy density, leaf area index and mean leaf angle were analysed statistically. The cooling effect reached its maximum by 13:00h, whereas the humidifying effect reached its peak at 09:00h. Compared with the control open space site, the community seemed to lower the air temperature by 1.0°C–5.0°C and to increase the relative humidity by 4%–15% during the daytime. Furthermore, the canopy density had a greater impact in terms of cooling and humidifying effects from 08:00h to 13:00h. In addition, these effects were more controlled by the canopy density and by the leaf area index than by the mean leaf angle from 15:00h to 18:00h. The results also suggest that the nature of the correlations will vary at different times of the day. Overall, these findings provide new insights into the relationships between canopy structural characteristics and diurnal variations in microclimatic parameters in urban forests, which could be studied in greater detail in future studies.

Thermal analysis of PCM-filled glass windows in hot summer and cold winter area

Phase change material (PCM)-filled glass window was suitable for absorbing or releasing more heat than conventional glass window. Comparisons of thermal performance between PCM-filled glass windows and insulated glass windows (double glass windows filled with dry air and surrounded by sealing strips) were presented in this paper. A 3D unsteady model was built in FLUENT to obtain the internal and external surface temperature fluctuations of these windows in 48 h. Compared with insulated glass windows, thermal performance (especially the thermal regulation effect) of double glass windows filled with Na2SO4·10H2O was quite satisfactory in sunny days of summer, while double glass windows filled with CaCl2·6H2O had a better thermal performance in overcast and rainy days of summer. Because the phase change temperature of these PCM is higher than the ambient temperature in winter, the thermal regulation effects of them were not as good as expected.

Heat-sink effect and indoor warming imposed by tropical extensive green roof

The study evaluates diurnal cooling effect of two herbs on tropical green roofs, C3 broadleaved Perennial Peanut (Arachis pintoi) and CAM succulent Mexican Sedum (Sedum mexicanum) with contrasting photosynthesis-transpiration physiology. The holistic outdoor-substrate-indoor vertical temperature profile is evaluated. Control, Sedum and Peanut experimental plots were established on a residential building in Hong Kong, each equipped with temperature sensors at 7–11 vertical positions. On summer sunny day, Control plot displays conspicuous daytime heating at roof surface and 15cm and 150cm above it. Indoor air and ceiling temperatures with <2°C diurnal range indicates effective dampening by building heat-sink effect. Sedum roof displays a vertical thermal sequence: 15cm>soil>Sedum surface>drainage>150cm>tile. Sedum surface is heated to a maximum of 35.4°C, merely 1–2°C lower than adjacent soil and 15cm air, indicating daytime CAM stomata closure to restrict transpiration cooling. Contrary to expectation, sensible heat stored in Sedum roof generates green-roof heat-sink effect (GHE), driving downward heat flux throughout the day to raise indoor temperature by 1–2°C. Peanut plot's vertical thermal sequence is: 150cm>15cm>soil>rockwool>Peanut surface>drainage>tile. Peanut surface is significantly cooled by C3 transpiration to 28.8°C, and it remains the coolest among outdoor positions throughout the day. Slightly less heat than Sedum is fluxed downwards to raise indoor temperature. Cooling due to effective C3 transpiration and thicker vegetation and substrate layers is offset by more intensified GHE. The green roofs demonstrate opposite proximal thermal impact which is limited to near-ground (15cm) air, with warming at Sedum but cooling at Peanut. Both vegetated plots show less heat ingress into indoor space in daytime, but more in nighttime. On summer cloudy and rainy days, both green roofs with GHE brought more heat flux to indoor space throughout the day. Contrary to findings outside the tropics, the tropical extensive green roofs cannot bring net cooling to indoor environment in summer.

Numerical simulations of boundary‐layer processes and urban‐induced alterations in an Alpine valley

AbstractHigh‐resolution simulations are performed with the Weather Research and Forecasting (WRF) model, coupled with an advanced urban parameterization scheme, to evaluate the modifications induced by the urban area of Trento on boundary‐layer processes in the Alpine Adige Valley in a typical summer sunny day. Specific gridded datasets of urban morphology parameters and anthropogenic heat releases were created to provide high‐resolution input information for the urban scheme. Comparison of model results against measurements from surface weather stations shows that the model simulates reasonably well the development of valley winds, as well as the complex interaction occurring north of Trento between the up‐valley wind of the Adige Valley and a lake breeze flowing from a tributary valley. The urban heat island of the city is also well captured by the model, with stronger intensities at night and lower values during daytime. Comparisons with an idealized simulation, where all the urban land use grid points are replaced by cropland, suggest that the city inhibits the development of the ground‐based thermal inversion at night and also affects valley winds, modifying both the typical down‐valley wind, and the interaction between the up‐valley wind of the Adige Valley and the lake breeze. Further sensitivity tests are performed to evaluate the impacts of the gridded datasets of urban morphology and anthropogenic heat releases, and to assess what are the benefits of using the advanced urban scheme against a simple bulk parameterization. Results highlight that even the moderate anthropogenic heat releases present in Trento appreciably affect nocturnal temperatures in the city, while gridded information on urban parameters is not essential in the present case, because urban morphology does not display a high spatial variability. However, it is shown that the choice of the urban scheme may have significant impacts on both temperature and wind fields.

Determination of estrogenic steroids and microbial and photochemical degradation of 17α-ethinylestradiol (EE2) in lake surface water, a case study

In this study, a GC-MS technique was applied to determine 17α-ethinylestradiol (EE2), an active ingredient of oral contraceptives, and its fate in Lake Quinsigamond, Massachusetts, USA. To the knowledge of the authors, this is the first study of EE2 and its microbial and photochemical degradation in a lake ecosystem. EE2 was detected at a concentration up to 11.1 ng L(-1). At this concentration EE2 may affect the reproduction of fish and other aquatic organisms in the lake due to its high estrogenic activity. EE2 was persistent to the biodegradation by the microorganisms in the lake. Under aerobic conditions a long lag phase (42 days) was observed before the biodegradation of EE2 and a half-life of 108 days was estimated. Under anaerobic conditions, EE2 experienced even a longer acclimation stage (63 days) and a slower microbial degradation in the lake water. The photodegradation of EE2 was rapid in the lake surface water under natural sunlight, with a half-life of less than 2 days in summer sunny days. Compared to biodegradation, photodegradation may represent a predominant removal mechanism for EE2 in natural surface waters.

Numerical simulation of airflow in a solar chimney for cooling buildings in the city of Yazd

This paper investigates numerically a two-dimensional turbulent flow in a solar chimney due to free convection heat transfer. For evaluation of the fluid flow and heat transfer in the system, the basic equations including conservation of mass and momentum in the x, y directions and energy in the Cartesian coordinate are converted to the algebraic form using the finite volume method. This simulation (use the commercial CFD code) provides the profile of temperature, velocity, and mass flow rate variations in the solar chimney in different conditions. These results can be used to evaluate the effective parameters and optimize the performance of the system for natural evaporative cooling and ventilating the buildings. Based on climate conditions in Yazd, the optimum dimension of the width of the chimney is 0.3–0.4 m, inlet height is 0.3 m, and the flow rate created in the system and at the outlet is at 0.18 m3/s. The mean cooling rate resulted from the solar chimney is about 800 W/m2. Considering the long hot and sunny days of summer (about 12 h in Yazd), the use of this system in warm and dry region is recommended. We can save a considerable amount of energy sources such as natural gas or oil and lower CO2 emissions.

Effects of excessive weather on the micro-climate of apple plantations under the hail protection nets

The general utilisation of hail nets is spreading all over the world and in Hungary too. Hail nets are at present the only tool, whichis able to prevent heavy hail damage in agricultural crops. Besides its numerous advantages, there are also deleterious side effects, e.g. itchanges the microclimate of the crop stand. Our study aimed to observe the differences, which characterise the physical status of crop standsunder the protection of hail nets compared with the stands in open air under various meteorological conditions: high or low temperature, calmor windy atmosphere and their possible combinations. The results indicated that on hot and calm days the difference may attain 3–4° C. Oncool summer days, the difference was only 1.5 ºC. The hail net influences the relative humidity of the air, which means on ho summer daysoften 7-8% differences. Conditions of radiation may also differ conspicuously. Measurements prove the reduced global radiation on sunnysummer days to 70%. This impairs as a rule the development of fruits reducing their quality and also its quantitative traits. Sunburn is, on theother hand, significantly prevented by shadow.

Weather effect on thermal and energy performance of an extensive tropical green roof

This study investigated the weather effect on thermal performance of a retrofitted extensive green roof on a railway station in humid-subtropical Hong Kong. Absolute and relative (reduction magnitude) ambient and surface temperatures recorded for two years were compared amongst antecedent bare roof, green roof, and control bare roof. The impacts of solar radiation, relative humidity, soil moisture and wind speed were explored. The holistic green-roof effect reduced daily maximum tile surface temperature by 5.2°C and air temperature at 10cm height by 0.7°C, with no significant effect at 160cm. Green-roof passive cooling was enhanced by high solar radiation and low relative humidity typical of sunny summer days. High soil moisture supplemented by irrigation lowered air and vegetation surface temperature, and dampened diurnal temperature fluctuations. High wind speed increased evapotranspiration cooling of green roof, but concurrently cooled bare roof. Heat flux through green roof was also weather-dependent, with less heat gain and more heat loss on sunny days, but notable decline in both attributes on cloudy days. On rainy days, green roof assumed the energy conservation role with slight increase instead of reduction in cooling load. Daily cooling load was 0.9kWhm−2 and 0.57kWhm−2, respectively for sunny and cloudy summer days, with negligible effect on rainy days. The 484m2 green roof brought potential air-conditioning energy saving of 2.80×104kWh each summer, equivalent to electricity tariff saving of HK$2.56×104 and upstream avoidance of CO2 emission of 27.02t at the power plant. The long-term environmental and energy benefits could justify the cost of green roof installation on public buildings.

A generic temperature model for solar photobioreactors

With the objective of addressing issues related to the temperature control of a solar closed photobioreactor (PBR), a laboratory set-up representative of an intensified closed flat panel PBR was designed. Only its thermal behaviour was considered, with no cultivation of microalgae. It was characterized indoors under controlled artificial irradiation and outdoors under solar irradiation on sunny days in summer. A simplified thermal model to predict the temperature time course was developed and validated by comparison with experimental results. The thermal model was then used as a simulation tool to investigate relevant parameters influencing thermal behaviour, such as the optical properties of the illuminated surface and the surrounding wind speed. A heat balance was applied for different cases to determine the energy consumption during one year of operation with temperature regulated in a range suitable for microalgae growth.

Photodegradation of psychiatric pharmaceuticals in aquatic environments – Kinetics and photodegradation products

Benzodiazepines are widely consumed psychiatric pharmaceuticals which are frequently detected in the environment. The environmental persistence and fate of these pharmaceuticals as well as their degradation products is of high relevance and it is, yet, scarcely elucidated. In this study, the relevance of photodegradation processes on the environmental persistence of four benzodiazepines (oxazepam, diazepam, lorazepam and alprazolam) was investigated. Benzodiazepines were irradiated under simulated solar irradiation and direct and indirect (together with three different fractions of humic substances) photodegradation kinetics were determined. Lorazepam was shown to be quickly photodegradated by direct solar radiation, with a half-life time lower than one summer sunny day. On the contrary, oxazepam, diazepam and alprazolam showed to be highly resistant to photodegradation with half-life times of 4, 7 and 228 summer sunny days, respectively. Apparent indirect and direct photodegradation rates are of the same order of magnitude. However, humic acids were consistently responsible for a decrease in the photodegradation rates while fulvic acids and XAD4 fraction caused an enhancement of the photodegradation. Overall, the results highlight that photodegradation might not be an efficient pathway to prevent the aquatic environmental accumulation of oxazepam, diazepam and alprazolam. Also, nineteen direct photodegradation products were identified by electrospray mass spectrometry, the majority of which are newly identified photoproducts. This identification is crucial to a more complete understanding of the environmental impact of benzodiazepines in aquatic systems.

ACSA : An Adaptive Content System Architecture

Adapting content services to the needs of the users requires content adaptation for context and sensibility. Adapting to context may necessitate distinguishing between video delivery to a PC versus a smart phone, while adapting to sensibility may necessitate between video delivery outside, in a quiet environment, or at home, or offering different movie choices on a sunny summer day, a cold winter day or a holiday season. One key area to address in providing adaptive content services is the design of the delivery system architecture of the adaptive content server. This paper describes several alternatives for this architecture, and outlines some additional concerns that must be considered when the chosen architecture is implemented.

Comfort and Energy-Saving Intelligent Shutter

Most currently used shutters are manually operated. The design of an intelligent shutter has been proposed. The intelligent shutter can be powered by a solar battery. Photosensitive resistors have been used to determine if it is in daytime or nighttime, if it is sunny or not, and if the light is turned on or turned off. Digital temperature sensors have been used to detect the indoor temperature and the outside temperature. They are also used to determine the current season. The intelligent shutter is automatically controlled according to the above information. It is turned off at night and is set in sleep mode to save energy. It is turned on partially on sunny day in summer. In rainy day, the shutter is turned off while the indoor light is on. The intelligent shutter can also be controlled using a wireless remote controller, which makes it very friendly. It is comfort and energy-saving using the intelligent shutter. Experiments have demonstrated the applicability of the design.

CHARACTERIZATION AND ANALYSIS OF THE EFFECTS OF GREENHOUSE CLIMATE CONTROL EQUIPMENT ON GREENHOUSE MICROCLIMATE AND CROP RESPONSE

An overview of the recent scientific and technical advances on issues concerning the greenhouse microclimate, control and management in Mediterranean regions is presented and discussed. Special emphasis is given on the effects of climate control equipment in: (a) greenhouse microclimate and (b) crop response. The main greenhouse climate control systems presented and discussed are the heating, dehumidification, ventilation, shading and cooling systems. These systems are the most widely used for greenhouse climate control especially in the Mediterranean area. In these areas, natural ventilation and whitewashing are the most common methods/systems used for greenhouse climate control during summer, since they require less energy, less equipment operation and maintenance and are much cheaper to install than other cooling systems. However, generally these systems are not sufficient for extracting the excess energy during sunny summer days and therefore, other cooling methods such as forced ventilation combined with evaporative cooling (mist or fog system, sprinklers, wet pads), are used. On the other hand, during the winter period, heating and dehumidification are necessary for a standard quality production. Optimal greenhouse climate control became more important in the latter part of the 20th century, when concerns about food safety, environmental pollution stimulated extensive research in the development of Integrated Production and Protection systems aiming at a significant reduction of pesticides use. The prospective and needs for future research and development in greenhouse climate control are presented in the conclusion. Special emphasis is given to the necessity to combine both physical and ecophysiological studies, because of the crucial role played by the crop in determining the microclimate in greenhouses.