Outdoor Wind Speed Research Articles

A novel solar photovoltaic/thermal assisted gas engine driven energy storage heat pump system (SESGEHPs) and its performance analysis

In order to study the most economical way of heating the buildings, considering the effect of the bilateral load demands on the way of heating the buildings, a novel solar photovoltaic/thermal assisted gas engine driven energy storage heat pump system (SESGEHPs) is presented which can meet the demands of the real-time building heating load and lower temperature heat source of evaporator to ensure the PV/T system works in the optimum temperature range. A test bench of SESGEHPs is set up and the experiments are carried out to test the system heating performance, including the characteristics of the PV/T system, ESGEHPs, building heating load and environmental parameters. The experimental results show that the average COP and PER of the SESGEHPs is nearly 24.5% and 20.4% higher than the ESGEHPs, respectively. The fuel-consumption and the average compressor power consumption of SESGEHPs is nearly 7.5% and 24.0% lower than the ESGEHPs, respectively. Finally, the experimental data are processed using the generalized regression neural network (GRNN) to get the relationship between the independent variable (solar radiation, outdoor dry bulb temperature and wind speed) and dependent variable (the building heating load, heating capacity of the SESGEHPs, heat-obtained quantity and power generation of the PV/T system). It is found that the operating characteristics of the SESGEHPs are greatly affected by the solar radiation and the outdoor temperature, and less affected by the wind speed.

Prediction Research of Heating Load in Residential Area Based on BP Neural Network

This paper analyzed the influence factors of heating load in residential area. The BP neural network algorithm was used for forecast, and BP neural network structure were built. The input sample was outdoor temperature, outdoor wind speed, indoor heat coefficient and heat supply in the last few days. The network structure output was heating load value on the day. Besides, the heating load of a residential district was predicted and verified by day unit and hour unit heating load, and the error of heating load forecasting with different methods were compared. The result shows that the regulation of heating load changes in residential area is periodic. the accuracy of heating load forecasting using hours as a unit is higher than using the day as a unit.

Improving the air change rate in high-rise buildings through a transom ventilation panel: A case study

Passive ventilation techniques can both improve indoor air quality (IAQ) and reduce energy consumption and costs in buildings. In particular, using wind-driven ventilation as a passive design strategy can increase indoor air velocity in naturally ventilated buildings. In tropical regions, where there are only limited differences between indoor and outdoor air temperatures, wind-driven ventilation through a transom ventilation panel (TVP) can be a positive ventilation technique. In this study, we evaluated through experimental tests the efficiency of single-sided ventilation and cross-ventilation through a TVP in a unit within a high-rise residential (HRR) building. To this end, we carried out a series of numerical simulations to calculate the airflow patterns and the indoor air velocity for various outdoor wind speeds when cross-ventilation was applied. The results show that TVP can increase indoor air velocity by up to four times, depending on the outdoor wind speed and the location within the unit. Also, in windy conditions, the mean air change per hour (ACH) in a unit equipped with a TVP is 27% greater than a unit without a TVP. Moreover, a TVP can improve air change rate even when the outdoor wind speed is less than 0.02 ms−1.

A model for calculating single-sided natural ventilation rate in an urban residential apartment

Natural ventilation is an energy-efficient ventilation method for residential buildings, but it is not easy to determine the natural ventilation rate. This investigation developed a simple model for calculating the ventilation rate for an apartment with single-sided natural ventilation with buoyancy and wind pressure effects, based on a wind-driven model. To validate the model, field measurements were conducted in an apartment in an urban residential building in Tianjin, China. The experiment measured indoor and outdoor air temperature, wind speed and direction, wind pressure coefficient at an opening of the apartment, and ventilation rate through the single opening. The results indicated that the wind pressure coefficients calculated by Eq.12 did not agree well with the measured data. However, most of the measurements show a stronger buoyancy effect than wind pressure effect. Our new model was able to predict the ventilation rate with an average error of 13.1%. When we used six other models found in the literature to predict the ventilation rate, the errors ranged from 12.9% to 46.1%. Thus, not only does our model perform very well in predicting the ventilation rate, but it also shown the interaction between buoyancy and wind pressure.

Effect of Outdoor Wind on the Efficiency of Mechanical Smoke Exhaust in High-rise Building Fires

In this paper, in order to analyze the effect of the outdoor wind on the efficiency of the mechanical exhaust system in high-rise building fires, a 15-floor high-rise building with a long corridor in Nanjing was studied. FDS (Fire Dynamic Simulation) was used to analyze the effect of different smoke exhaust models under the influence of outdoor wind. Without the outdoor wind, the CO2 concentration in the corridor was 3080ppm, natural smoke exhaust model could meet the need for evacuation. When the outdoor wind speed was 2.4m/s, the CO2 concentration in the corridor was 5042ppm, which was unable to meet the need for evacuation. Thus additional mechanical exhaust system was necessary to add for reducing the CO2 concentration in the corridor. Because the outdoor wind speed showed exponential growth with height increased, the CO2 concentration in the corridor increased with height of fire floor under the same mechanical exhaust system. The smoke exhausting volume should be redesigned, because the traditional mechanical exhaust system was unable to guarantee the people to escape safely when the fire floor was on the 12th floor or above.

Noise-reducing vents for windows in warm, humid, tropical countries

ABSTRACTSustainable building design requires the application of natural ventilation, which has three prerequisites – a comfortable outdoor air temperature (20–25°C), unpolluted outdoor air and a low-noise environment (under 55 dBA). There are many locations where the first two prerequisites are met, but the environmental noise makes applying natural ventilation challenging. This research developed an auxiliary noise-reducing vent for windows (NRVW) that allows daylight and outdoor air to enter the room while reducing the penetration of outdoor noise. As an auxiliary, the NRVW is intended to be integrated into any (double) glazed windows with a sound transmission class (STC) above 25 dBA. The research used physical model experiments to measure the NRVW’s STC and outdoor–indoor transmission class (OITC). Digital model simulation was used to measure the NRVW’s ventilation performance. It was found that NRVW has a rating of STC 18 and OITC 16, and it generates indoor air velocity of 0.015–0.086 m/s in the occupants’ zone for an outdoor wind speed of 1–5 m/s. Modification of the room interior increases the indoor air velocity to 0.147 m/s. Computer simulation also demonstrated that, with an occupant inside the room, an outdoor air temperature of 25°C and outdoor wind speed of 1–5 m/s maintained the indoor air temperature at 25.309–25.258°C, indicating that the resulting airflow could keep the indoor air temperature low. Although the NRVW was originally developed for warm–humid climate conditions, it is also applicable for other climates if the required outdoor conditions are met.

Discussion on fresh air volume in Temperature and Humidity Independent Control of Air-conditioning System

The fresh air volume in Temperature and Humidity Independent Control of Air-conditioning System(THIC) of a typical office was comfirmed, under the premise of adopting the refrigeration dehumidifying fresh air unit(7°C/12°C). By detailed calculating the space moisture load and the fresh air volume required for dehumidification in 120 selected major cities in China, it can be inferred that the minimum fresh air volume required for dehumidification in THIC is mainly determined by the local outdoor air moisture and the outdoor wind speed; Then the mathematical fitting software Matlab was used to fit the three parameters, and a simplified formula for calculating the minimum per capita fresh air volume required for dehumidification was obtained; And the indoor relative humidity was simulated by the numerical software Airpak and the results by using the formula data and the data for hygiene were compared to verify the relibility of the simplified formula.

A multiple-fan active control wind tunnel for outdoor wind speed and direction simulation.

This article presents a new type of active controlled multiple-fan wind tunnel. The wind tunnel consists of swivel plates and arrays of direct current fans, and the rotation speed of each fan and the shaft angle of each swivel plate can be controlled independently for simulating different kinds of outdoor wind fields. To measure the similarity between the simulated wind field and the outdoor wind field, wind speed and direction time series of two kinds of wind fields are recorded by nine two-dimensional ultrasonic anemometers, and then statistical properties of the wind signals in different time scales are analyzed based on the empirical mode decomposition. In addition, the complexity of wind speed and direction time series is also investigated using multiscale entropy and multivariate multiscale entropy. Results suggest that the simulated wind field in the multiple-fan wind tunnel has a high degree of similarity with the outdoor wind field.

Factors influencing indoor PM2.5 concentration in rural houses of northern China

In traditional houses in rural areas of Northern China, most traditional heating systems, heated by mini-stove in the kitchen, usually take agricultural residues as fuels resources. Besides, burning cave under the ground-floor of a rural house is also widely used. The higher PM2.5 concentration is crisis for human health. In this study, PM2.5 concentration, temperature, relative humidity inside and outside the houses have been measured, moreover the factors impact on I/O rate coefficient has been discussed. The results show that the I/O rate coefficient in the evening is 2.5 times greater than the I/O rate coefficient in the daytime. I/O rate coefficient of PM2.5 concentration is positive related to air temperature difference between indoor and outdoor. In addition, the impact of outdoor wind speed and predominant wind direction on the PM2.5 emission has been studied.

Seasonal variation of window opening behaviors in two naturally ventilated hospital wards

Natural ventilation enables personal control, and occupant behaviors in window opening play a decisive role on natural ventilation performance, indoor air quality (IAQ), and/or airborne infection risk in a hospital setting. The occupant behaviors differ significantly from different building types with different functions and living habits. Based on a one-year field measurement in two general hospital wards in Nanjing, China, the effects of air quality (i.e. indoor CO2 concentration and outdoor PM2.5 concentration) and the climatic parameters (i.e. indoor/outdoor temperature, relative humidity, and outdoor wind speed, wind direction and rainfall) on window opening/closing behaviors are analyzed. Indoor air temperature or relative humidity is found to be a dominant factor for window opening behaviors. Seasonal differences are observed for the different influences of physical factors. The outdoor temperature is found to be associated with the window opening probability negatively during the cooling season, but positively during the transition and heating seasons. The indoor relative humidity positively affects the window opening probability during the transition season while a negative impact appears during the cooling and heating seasons. Based on the seasonal variation of window opening behaviors, Logistic regression models in different seasons (cooling, transition and heating seasons) are developed to predict the window opening/closing state and are verified to be promisingly adaptable with results of accuracy bigger than 70%.

Impacts of climate change on the cooling loads of residential buildings differences between occupants with different age

Climate Change is known to have a great impact on the energy consumption in buildings. This paper studied the cooling load of a residential building in Jinan, China, in 2020, 2050, 2080 by considering the impacts of climate change on the influential parameters for cooling loads. The Hadley Centre Coupled Model 3(HadCM3) was employed to investigate the impact of climate change on the outdoor temperature, solar radiation and wind speed. In addition, this study also differentiated the cooling loads according to occupants’ age, since the energy usage patterns and the requirements on cooling loads are closely related to occupants’ age. The results suggest that climate change will create significant impacts on the cooling loads in residential buildings. Regarding occupants’ age, the impact on the occupants under 55-year-old is larger than the people older than 55.

Multivariate multifractal detrended fluctuation analysis of 3D wind field signals

Characterizing the dynamic behavior underlying wind field from experimental multivariate signals is a challenging problem of continuous interest. In this work, we propose the multivariate multifractal detrended fluctuation analysis (MV-MFDFA) method to directly study the fractal dynamics of multichannel data in a complex system. By conducting several simulations on synthetic multivariate series, the validity of the proposed MV-MFDFA is illustrated. Then we utilize MV-MFDFA to analyze the 3D wind field signals collected at two different airflow environments, i.e., indoor and outdoor environments. Results show that the indoor and outdoor three wind vectors show multifractal properties, and the multifractal degrees of outdoor three wind vectors are stronger than those of corresponding indoor three wind vectors. By analyzing the indoor and outdoor multivariate wind speed, we find that the indoor and outdoor multivariate wind speed are antipersistent long-range correlation, and the indoor multivariate wind speed exhibits weaker multifractal properties than that of outdoor multivariate wind speed. Moreover, the multifractality of indoor multivariate wind speed depends mainly on the large fluctuations, while the multifractality of outdoor multivariate wind speed depends mainly on the small fluctuations. These findings indicate that the MV-MFDFA allows better understanding the dynamical mechanisms governing 3D wind variability.

Numerical analysis of indoor thermal comfort in a cross-ventilated space with top-hung windows

Abstract: Natural ventilation can be used in residential buildings in several Australian climatic zones and well-designed windows have the potential to facilitate indoor thermal comfort by allowing occupants to control volumetric outdoor airflow and indoor air velocities. Top-hung window is one of the most popular window types in Australia. This paper investigates the effect of the attributes of top-hung windows (i.e. window length, aspect ratio, height above the ground, window opening angle and the fly screen porosity) and outdoor air conditions (i.e. outdoor air temperature, wind speed and direction) on indoor thermal comfort during cross ventilation using CFD simulations. The Taguchi method was used to design the simulation scenarios and analysis of variance was used to determine the most significant factors influencing thermal comfort optimisation so as to reduce the number of CFD simulation cases. For the range of parameters considered and a particular case study building, results show that outdoor air temperature, window height and window opening angle are the most important factors influencing indoor thermal comfort in this room. The optimal window configurations for indoor thermal comfort of the case study building are also identified using a signal-to-noise ratio analysis.

Study on moisture condensation on the interior surface of buildings in high humidity climate

Hot and humid air infiltration would lead to moisture condensation on the interior surface of buildings in high humidity climate, which has a negative influence on the indoor environment and building life. This study aims to expound the transient property of moisture condensation on the interior surface of buildings in high humidity climate, and find the typical places where moisture condensation often occurs by numerical and experimental methods. A numerical model of a test chamber is established, which is used to predict the distribution of heat and humidity due to air infiltration. Simulation results from the application of FLUENT software are compared with the experimental data, and a validation procedure is presented. The effect of outdoor air temperature, humidity ratio and wind speed on the moisture condensation state is investigated. The results prove that these parameters have a significant impact on the start time, duration and magnitude of moisture condensation. Two regression equations are developed from the experimental results, which describe the relationship between the indoor air temperature, humidity and the factors of infiltrated air. Meanwhile, two kinds of dew-proof solutions are proposed.

Window opening behavior of occupants in residential buildings in Beijing

Window opening behavior has a vital influence on indoor air quality, thermal comfort, and energy consumption. In residential buildings, the window opening behavior of occupants may vary considerably owing to different indoor and outdoor environmental parameters and personal habits. In this study, we investigated the factors influencing the window opening behavior of occupants in 19 residences in Beijing by monitoring the open/closed status of windows, and eight environmental parameters, including temperature and relative humidity of indoor and outdoor air, indoor CO2 concentration, outdoor PM2.5 concentration, and outdoor wind speed and direction. The influence of the season and time of day was also analyzed, and typical window operation schedules were determined. Predictive models of the occupants' window opening behavior were established based on multivariate linear logistic regression. The results indicated that outdoor air temperature was the most influential factor, followed by indoor CO2 concentration, indoor air temperature, outdoor and indoor relative humidity, ambient PM2.5 concentrations, and outdoor wind direction and wind speed.

Soiling-induced transmittance losses in solar PV modules installed in Kathmandu Valley

Renewable energy sources are fast emerging as more reliable supplement of conventional energy sources. Among the various renewable sources, solar energy is most sought after in today’s world. Solar PV modules when installed in outdoor environments suffer from various factors which are generally unaccounted in laboratory testing. Energy generation from solar collectors is primarily dependent on the amount of incident radiation on their surfaces. Soiling on modules is known to reduce the transmittance of incident rays to solar cell and cause significant output power degradation. Soiling is closely associated with the various factors such as module tilt angle, site-specific climate, outdoor exposure period, humidity, wind speed, dust characteristics and material properties. This experimental work is aimed to study the transmittance losses encountered by solar PV modules and the corresponding power degradation. The experimental results show an alarming reduction in transmittance as high as 69.06% over the dry study period experiencing no rain. The power of dusty solar module decreases by 29.76% compared to the module cleaned on daily basis. Dust deposition density on the PV module accounted to 9.6711 g/m2 over the study period.

Topography integration to wind downscaling

In building energy simulations, an urban context is assessed for its impact on local wind conditions. This process, known as wind downscaling, generally considers terrain that is characterized by the obstructions such as buildings and trees. However, topography, the shape of a land, is hardly considered for its combined impact with terrain. Wind downscaling is particularly challenging in large urban areas for the required high computational costs, while the existing models are still in their infancy. This paper developed a method to integrate the topography effect in existing terrain-driven wind downscaling. To facilitate its utility in early design stages, sampling and interpolation approach were adopted for computational efficiency. Samples were generated for urban contexts, considering topography with slopes and terrain with buildings. These samples were geometrically modeled and assessed for outdoor wind speed in virtual wind tunnel tests with CFD simulations. The assessment results were analyzed and stored in a database, which was used to interpolate for a new condition. The proposed method was demonstrated for its reasonable accuracy and high computational efficiency by comparing the interpolation result with CFD simulation for an actual site.

Factors affecting occupants’ interactions with windows in residential buildings in Beijing, China

Occupants’ interactions with windows not only influence energy consumption but also influence indoor air quality of the buildings. There are many factors that affect occupants’ behaviors on windows opening and closing, such as the arrival of occupants, meteorological condition, indoor thermal environment and air quality. In this study, we tended to investigate what and how environmental factors influence residential occupants’ window opening behavior in spring in Beijing, China. The environmental factors concluded air temperature and relative humidity of indoor and outdoor, indoor CO2 concentration, outdoor PM2.5 concentration and outdoor wind speed. We conducted a field study in 9 naturally ventilated residences in Bei-jing during spring. Environmental parameters mentioned above and window status were monitored. A stochastic model of occupants’ window opening behavior was established via multi-variate linear logistic regression. The results indicate that influence of the all 7 variables on window opening behavior was significant. The multivariate linear logistic regressed model with normalized variable for the window opening behavior prediction is [logitp=log(p1−p)=2.11CCO2,nor+2.096Tin,nor−5.277RHin,nor−3.547CPM,O,nor+5.71Tout,nor+4.512RHout,nor−2.158Vs−1.844]

Study on the influence of air curtain barrier efficiency on infiltration air volume and temperature distribution in large space in winter

In this paper, a large space building model is built by CFD software to study the effect of air curtain on the reduction in infiltration air volume. The influences of the pressure difference between inside and outside, the air curtain air supply speed and the air curtain outlet thickness on the air curtain barrier efficiency are also discussed. The results show that when the pressure difference between indoor and outdoor is 1.0 pa, the barrier efficiency of air curtain is 40%-80% with the air curtain supply speed increasing from 8 m/s to 18 m/s. However, the barrier efficiency is 20%-45% when the indoor and outdoor pressure difference increases to 6.0 pa with the same air curtain supply speed range. At the same time, when the outdoor wind speed is 3 m/s, the rest area average temperature of the large space building with air curtain is 10.8 ºC higher than which without air curtain. The use of air curtain to reduce the amount of infiltration and improve indoor heat comfort has a very good effect.

Study on present situation and optimization strategy of infiltration air in a train station in winter

The role of hot or wind pressing forming a pressure difference between the indoor and out-door of the building envelop, the unorganized infiltration air will flow into rooms. Indoor and outdoor temperature, outdoor wind direction and speed have an impact on the infiltration air volume. There are multiple aisles connecting the outdoor space and the station hall, leading to a large amount of outdoor air into the station. In this paper, the measurement of infiltration air volume and regional temperature in railway station was performed in Wuhan. The software ContamW was used to simulate the ventilation paths and the infiltration air volume. The changes of infiltration air volume was analyzed, and the corresponding measures to reduce the infiltration air were studied. The results showed that using air curtains with the barrier efficiency of 62.6% and closing the opening windows, the static wind and v=3 m/s of northeast wind conditions, the amount of infiltration air can be reduced by 78% and 79% separately in Wuhan area.