Solar Air Research Articles

Theoretical Investigation on Transient Heat Transfer through Building for PV-powered Solar Summer Air Conditioning

Theoretical Investigation on Transient Heat Transfer through Building for PV-powered Solar Summer Air Conditioning

Топокліматичні особливості садово-паркових композиційних груп у парках міста Львова

Проаналізовано історико-стильовий генезис урбанізованих ландшафтів і формування системи садово-паркових насаджень міста Львова. Досліджено вплив місцевих ландшафтних геосистем і геофізичних процесів у них на формування топокліматичних характеристик парків. З'ясовано еколого-біологічні відмінності та особливості формування просторових природних явищ у певній садово-парковій композиції. Встановлено, що вивчення топокліматичних відмінностей потрібно починати із розгляду потоків сонячної радіації, температури повітря та ґрунту, атмосферних опадів і вітру. Проаналізовано територіальні еколого-біологічні відмінності та особливості формування просторових природних явищ залежно від потоків речовини та енергії. Виявлено вузькі амплітуди температури в геокомплексах вершин, середини і підніжжя схилів, бар'єрний вплив на міграцію та місцеву трансформацію повітряних мас, що впливає на специфіку піднаметового фітоценозу. Охарактеризовано врахування топокліматичних характеристик для підвищення комфортності розвитку садово-паркових композиційних груп. Відзначено, що поверхня пагорбів разом з мереживом стежок, прокладених на схилах, піддається ерозії та потребує зменшення та регулювання рекреаційного навантаження. Окреслено негативні явища, які сукупно із віковим чинником та відсутністю належного агротехнічного догляду впливають на умови місцезростання та розвиток паркових насаджень.

Influence of window area and thermal transmittance in the consumption of electric energy in mid-western Brazil

The opening of windows allows the entrance of natural light, however, allows the transfer of thermal load from inside to outside the building and vice versa. Currently, despite the technological advances, it is still not possible in many buildings to integrate natural and artificial light. The design of a building, its geometry, size and properly orientation of the openings can result in great energy savings. Hence, defining the ideal window area for an ambient in which there is a balance between solar thermal load, air conditioning and natural and artificial lighting would lead to an environment whereby the energy consumption is optimized. This research presents the already consolidated methodology for calculation of ideal window area, which aims at the lower consumption of artificial lighting and air conditioning, considering a residential living environment. The analysis of energy consumption was carried out using the DesignBuilder software and the climate file of the city of Cuiabá - MT was considered, in order to quantify the impact of the climate on the supply of natural light and energy consumption. The methodology was divided into 3 stages, the first one consists of the determination of the base case and the constitution of the types of materials for analysis of the different thermal transmittance. In the second part of the method the simulations were performed and in the last stage the results were analysed. The simulations were performed considering the opening area at each 10% of the facade, for three geometries (1: 2, 1: 1 and 2: 1) considering three construction systems. The results showed that the openings in the south facade consume less and that this orientation allows larger openings, as well as the use of geometries with greater depth. Also, the thermal properties of the envelope influence the ideal window area, and the larger the thermal capacity the larger the openings that can be used. The present research showed the importance of considering the adequate areas and implementation of windows in the projects through the simulation. The potential of using sunlight for lighting has also been proven, by integrating natural and artificial light.

Improvement in the Performance of a Solar Hot Air Generator Using a Circular Cone

In this work the design and the study of a solar hot air generator, using concentrated solar radiation are proposed. This generator consists of a circular disc heated by the radiation reflected by a parabolic collector. The disc is placed at the entrance of an opened vertical cone. Under the thermal radiation effect emitted by the hot source, the internal wall of the generator is heated. The heating of the air at the generator-inlet generates a thermosiphon flow that is added to the one created by the hot source. In order to determine the critical parameters, the local convective transfer along the generator wall as well as the thermal and dynamic fields of the hot air at the cone exit for different angles and ratios of the rays are studied. It has been found out that the critical parameters of the conical generator, from which the thermal and dynamic characteristics of the hot air produced are R*=0.5; C=0.65; α=8°, have significantly improved. A comparative study of the hot air characteristics at the exit of the optimal conical generator, with two cylindrical and rectangular generators of the same geometrical characteristics is realized. The obtained results reveal relative increases of the mass flow rate of 78% and the heat flux absorbed by the air of 116% at the exit of the optimal cone compared to the cylinder. The results show also relative increases of the air temperature and the thermal flux absorbed by the air respectively of 400% and 129% at the exit of the optimal cone compared to the channel. A correlation between the hot source temperature and the air temperature at the exit of the optimal conical generator has been determined.

Studying the Impact on Urban Health over the Greater Delta Region in Egypt Due to Aerosol Variability Using Optical Characteristics from Satellite Observations and Ground-Based AERONET Measurements

This research addresses the aerosol characteristics and variability over Cairo and the Greater Delta region over the last 20 years using an integrative multi-sensor approach of remotely sensed and PM10 ground data. The accuracy of these satellite aerosol products is also evaluated and compared through cross-validation against ground observations from the AErosol RObotic NETwork (AERONET) project measured at local stations. The results show the validity of using Multi-angle Imaging Spectroradiometer (MISR) and Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on the Terra and Aqua platforms for quantitative aerosol optical depth (AOD) assessment as compared to Ozone Monitoring Instrument (OMI), Sea-viewing Wide Field-of-view Sensor (SeaWiFS), and POLarization and Directionality of the Earth’s Reflectances (POLDER). In addition, extracted MISR-based aerosol products have been proven to be quite effective in investigating the characteristics of mixed aerosols. Daily AERONET AOD observations were collected and classified using K-means unsupervised machine learning algorithms, showing five typical patterns of aerosols in the region under investigation. Four seasonal aerosol emerging episodes are identified and analyzed using multiple indicators, including aerosol optical depth (AOD), size distribution, single scattering albedo (SSA), and Ångström exponent (AE). The movements and detailed aerosol composition of the aforementioned episodes are demonstrated using NASA’s Goddard Space Flight Center (GSFC) back trajectories model in collaboration with aerosol subtype products from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission. These episodes indicate that during the spring, fall, and summer, most of the severe aerosol events are caused by dust or mixed related scenarios, whereas during winter, aerosols of finer size lead to severe heavy conditions. It also demonstrates the impacts of different aerosol sources on urban human health, which are presented by the variations of multiple parameters, including solar radiation, air temperature, humidity, and UV exposure. Scarce ground PM10 data were collected and compared against satellite products, yet owed to their discrete nature of availability, our approach made use of the Random Decision Forest (RDF) model to convert satellite-based AOD and other meteorological parameters to predict PM10. The RDF model with inputs from the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2) and Global Land Data Assimilation System (GLDAS) datasets improves the performance of using AOD products to estimate PM10 values. The connection between climate variability and aerosol intensity, as well as their impact on health-related PM2.5 over Egypt is also demonstrated.

Microclima, produção e composição do mosto da ‘Syrah’ cultivada sob cobertura de plástico

Foi feita a caracterização do microclima do vinhedo, das variáveis de produção das videiras e das propriedades físico-químicas do mosto da uva para vinho ‘Syrah’ cultivada com cobertura e sem cobertura de plástico impermeável (ráfia). As videiras foram sustentadas em Y e manejadas em regime de safra de inverno na região produtora de uvas de Louveira, SP. Durante o período da maturação das uvas foram feitas determinações, na altura dos cachos, da radiação solar e da temperatura do ar. Na colheita foram determinadas as variáveis fitotécnicas (número de ramos, número de cachos, massa dos cachos e produtividade) e físico-químicas do mosto (teor de sólidos solúveis, acidez total, teor de ácido tartárico, antocianinas, polifenóis totais e taninos). Os valores de temperatura máxima do ar foram superiores nas videiras sob cobertura de plástico em comparação às cultivadas a céu aberto enquanto a radiação solar foi mais elevada na condição sem cobertura. A produtividade e o teor de sólidos solúveis totais foram mais elevados para as videiras sob cobertura de plástico. Não foi observada influência da cobertura de plástico impermeável nos teores de antocianina, polifenóis totais e taninos das uvas.

Desain Sistem Pembangkit Lisrik Tenaga Surya Pada Tambak Udang sebagai Penggerak Aerator

Indonesia is a tropical region with very large solarenergy where an average daily insulation of 4.5 - 4.8 KWh / m² /day. Based on this fact, solar energy is a potential form ofrenewable energy to be developed. This study aims to design aPLTS system which is the initial stage of planning PLTS systemdevelopment. This system Design uses Matlab software byutilizing the Matrix Unit Interface (GUI) Matlab to calculatethe amount of electrical load to be used, battery capacityrequirements, number of solar modules and large capacity ofthe inverter to be used. Location of the measurement datacollection takes place in the city of Pinrang, area of the Suppasub-district shrimp farm. Measurements are conducted todetermine how much solar radiation and air temperature in thepond area.

Solar Powered Air Compressor for Domestic Purpose

Solar Powered Air Compressor for Domestic Purpose

Appraisal of Climatic Conditions for Potential Solar Energy Applications in Nawabshah and Quetta Cities

This study was conducted to appraise climatic conditions for potential applications of solar energy units in Nawabshah and Quetta cities. For that, twenty two annual monthly average data of insolation on horizontal surface, at various slopes on titled surface, air temperature, earth skin temperature was acquired and evaluated through the Statistical Package for the Social Sciences software. It is discovered from the study that Quetta is a more promising place for installation of solar energy applications as compared to Nawabshah as it receives more solar radiations and less air temperature.

Heat transfer performance of an integrated solar-air source heat pump evaporator

This study proposes a dual heat source integrated heat pump evaporator using solar energy and air energy as the heat sources. Both the refrigerant and water coils were installed and arranged in the evaporator in a certain manner. During the cold season of Xiangtan (China), the heat transfer performance of the integrated heat pump evaporator was studied both experimentally and theoretically (through simulations). The results show that the evaporator’s hot water supply can increase the refrigerant’s evaporation temperature and heat pump’s coefficient of performance (COP). With the increase in average water temperature of evaporator from 14.6 °C to 39.5 °C, the heat pump’s COP increased by 15%. In the simulations conditions, the proportions of the heat released by air and the heat released by hot water are basically the same as the experimental date. Comparing the refrigerant-water-refrigerant type evaporator with the water-refrigerant-refrigerant type evaporator, the former is more capable of gaining heat from low temperature water than the latter, and is more conducive to the comprehensive utilization of air and solar energy by heat pump in the cold season. Additionally, the refrigerant-water-refrigerant type evaporator has better anti-frosting capability under lower water temperatures.

Solar hybrid air conditioning system to use in Iraq to save energy

The energy saving issues are becoming necessary worldwide, as excessive consumption of energy leads to the consumption of a larger amount of fuel, increases environmental pollution and negatively affects the ozone layer. In Iraq, in particular, the demand for central air conditioning systems and home air conditioners with high electrical capacity has become increasingly clear in the recent years. Air conditioning systems within residential and public buildings, as well as government facilities became a necessity for good internal comfort, which was driven by desertification, high temperature, air pollution and increased population, resulting in increased consumption of electric power and pressing of power plants. Aiming at usage of renewable energy sources, the proposed system uses solar collectors as auxiliary solar thermal compressors and integrate them with air conditioning systems. The proposed solution will increase the cooling system efficiency, reduce electricity consumption and pollution.

Application and evaluation of Stanghellini model in the determination of crop evapotranspiration in a naturally ventilated greenhouse

Stanghellini model is one of the few models primarily developed to predict the evapotranspiration of crops (ETc) in naturally ventilated greenhouses. However, there are insufficient data on the model regarding its use, particularly in China where solar greenhouses without heating systems are fast spreading for vegetable growth and production. The application of Stanghellini model and the evaluation of its performance using meteorological and tomato plant data generated inside an unheated and naturally ventilated multi-span Venlo-type greenhouse is exploited in this study. Model capability was evaluated by utilizing data from sap flow measurements, meteorological and crop data. Measured meteorological data included solar radiation (Rs), air temperature (Ta), relative humidity (RH) and net radiation (Rn). Average leaf area index (LAI) values measured during the experimental period were 1.00, 3.30, 4.05 and 2.93; while determined crop coefficients (Kc) changed from 0.40, 0.62, 1.12 to 0.83 for the initial stage, development stage, mid-season stage and late-season stage, respectively. Results from the study indicated that the average hourly ETc values of tomato plants using sap flow measurements were 0.165 mm/h, 0.148 mm/h, 0.192 mm/h and 0.154 mm/h for the initial stage, development stage, mid-season stage and late-season stage, respectively. Meanwhile, the ETc values obtained from calculation using Stanghellini model were 0.158 mm/h, 0.152 mm/h, 0.202 mm/h and 0.162 mm/h for the initial stage, development stage, mid-season stage and late-season stage, respectively. These ETc values calculated by the Stanghellini model were close to the measured values within the same period. The coefficients of correlation (R2) based on hourly ETc for the calibration data was 0.94 and that of the validation dataset was 0.90. Scatter plots of the estimated and measured hourly ETc revealed that the R2 and the slope of the regression line for May, June and July were 0.94, 0.90, 0.96 and 1.15, 0.97, 1.10 respectively. These data were well represented around the 1:1 regression line. A model sensitivity analysis carried out illustrates how the changes in Rs and Ta affect greenhouse ETc. Stanghellini model was therefore proven to be suitable for ETc estimation with acceptable accuracy in unheated and naturally ventilated greenhouses in the Northeast region of China. Keywords: calibration, verification, crop evapotranspiration, naturally ventilated greenhouse, sap flow DOI: 10.25165/j.ijabe.20181106.3972 Citation: Acquah S J, Yan H F, Zhang C, Wang G Q, Zhao B S, Wu H M, et al. Application and evaluation of Stanghellini model in the determination of crop evapotranspiration in a naturally ventilated greenhouse. Int J Agric & Biol Eng, 2018; 11(6): 95–103.

Design and experimental analysis of a solar thermoelectric heating, ventilation, and air conditioning system as an integral element of a building envelope

This study presents an innovative concept of a compact integrated solar-thermoelectric module that can form part of the building envelope. The heating/cooling modes use the photovoltaic electrical current to power the heat pump. The experimental analysis was carried out and the results of coefficient of performance were in the range 0.5–1 and 2.6–5 for cooling and heating functions, respectively. The study demonstrates that thermoelectric cooler can effectively be used for heating, ventilation, and air conditioning applications by integrating with solar panels especially in cooling applications. The system is environmentally friendly and can contribute in the implementation of zero energy buildings concept. Practical application: In order to help address the challenge of climate change and associated environmental effects, there is continuous demand for new technologies and applications that can be readily integrated into day-to-day life as a means of reducing anthropogenic impact. Heating, ventilation, and air conditioning, as one of the largest energy consumers in buildings, is the focus of many researchers seeking to reduce building energy use and environmental impact. This article proposes using facades and windows that have an integrated modules of solar photovoltaic cells and thermoelectric devices that are able to work together to achieve heating and cooling effects as required by the building without requiring any external operational power.

A comparison of VegSyst and mod-VegSyst models in predicting dry matter, nitrogen uptake and transpiration of greenhouse-grown tomatoes

The dynamic model in discrete time VegSyst for vegetable crops predicts thermal time (TT), daily dry-matter production (DMP), crop nitrogen uptake (Nup) and crop transpiration (ETc). Because this model makes photosynthetically active radiation (PAR) and ETc calculations that are very complex, a simplified model has recently been proposed. In mod-VegSyst, photo-thermal time (PTT) is proposed as a new state variable. Whereas VegSyst calculates ETc according to the FAO method, as the product of reference evapotranspiration and crop coefficients, in mod-VegSyst, ETc is calculated by the Baille transpiration model for greenhouse crops. Also, mod-VegSyst uses a simpler exponential light interception function based on the leaf area index (LAI), which is a function of PTT, to calculate DMP and Nup. The aim of the current work was to compare the quality of predictions of the two VegSyst models using data for global solar radiation, air temperature and relative humidity from an experiment carried out in Chapingo, Mexico, during autumn-winter 2015, in which tomatoes (Solanum lycopersicum L) were grown in an experimental greenhouse. Firstly, the parameters of both models were calibrated using nonlinear least squares estimation. The performance of the two models was then evaluated using squared root mean squared error (RMSE) and mean absolute error (MAE) statistics. The results showed that DMP and ETc rates are better predicted by mod-VegSyst than by VegSyst, whilst Nup was predicted similarly by the two models.

Assessment of olive transpiration derived from a remote sensing energy balance model compared with sap flow measurements

A remote sensing energy balance (R(SEB)) algorithm was used to estimate transpiration (TRSEB) from a high density and drip-irrigated olive (Olea europaea L. 'Arbequina') orchard, located in Pencahue Valley, Maule Region of Chile (35°23'S; 71°44'W). Meteorological variables over the orchard such as solar radiation, air temperature, relative humidity, wind speed and canopy temperature from zenith were recorded during the southern hemisphere summer, from January through February 2015. The RSEB model was evaluated using sap flow measurements obtained from compensation heat-pulse sensors. In 30-min intervals, the results showed that RSEB model estimated the olive transpiration with errors of 16%, presenting a root mean square error (RMSE) of 0.2 L h-1 and a mean absolute error (MAE) of 0.1 L h-1. On a daily basis, the RSEB model was able to predict the olive transpiration with RMSE and MAE values of 0.68 and 0.57 mm day-1, respectively. The overall analysis suggested that the model underestimates transpiration with errors of 10% on a daily basis.

Empirical Model of Human Thermal Comfort in Subtropical Climates: A First Approach to the Brazilian Subtropical Index (BSI)

The bioclimatic well-being of individuals is associated with the environmental characteristics of where they live. Knowing the relationships between local and regional climatic variables as well as the physical characteristics of a given region and their implications on thermal comfort is important for identifying aspects of thermal sensation in the population. The aim of this study is to develop an empirical model of human thermal comfort based on subjective and individual environmental patterns observed in the city of Santa Maria, located in the state of Rio Grande do Sul, Brazil (Subtropical climate). Meteorological data were collected by means of an automatic meteorological station installed in the city center, which contained sensors measuring global solar radiation, air temperature, globe temperature (via a grey globe thermometer), relative humidity and wind speed and direction. A total of 1720 people were also interviewed using a questionnaire adapted from the model recommended by ISO 10551. Linear regressions were performed to obtain the predictive model. The observed results proposed a new empirical model for subtropical climate, the Brazilian Subtropical Index (BSI), which was verified to be more than 79% accurate, with a coefficient of determination of 0.926 and an adjusted R2 value of 0.924.

An improved model to predict thermal runaway in concentrator III–V multi-junction solar cells

Thermal runaway is a serious problem leading to the sudden death of solar cells connected in parallel in concentrator photovoltaic (CPV) modules when those cells are not protected by string diodes. In this paper, an improved thermal runaway model is proposed with consideration of temperature dependence of external quantum efficiency (EQE), short-circuit current and diode behavior. Based on this model, the influence of key parameters, such as concentration ratio (CR), the number of solar cells connected in parallel, the shaded area of the solar cell, air mass and aerosol optical depth on the thermal runaway effect in CPV modules, has been analyzed. For a given CR, the maximum number of parallel-connected solar cells is determined in order to avoid the sudden death of the shaded solar cell.

Development and application of a dynamic model for a solar assisted liquid desiccant air conditioning system

The investigation showed that there were few research works about the real dynamic performance of solar-assisted liquid desiccant air conditioning systems with an unsteady term in the governing equations. Regarding the unsteady properties of the components, a novel dynamic model was developed for a solar-assisted internally cooled liquid desiccant air conditioning system. In the model, the variable t (time) was involved in the governing equations of each component to take into consideration the influence of the previous condition on the following state of the system. The accuracy of the above mathematical model was verified partly with experimental results of some key components. Then the model was applied to a real solar-assisted internally cooled liquid desiccant air conditioning system for an office building with the capacity for eight people in Hong Kong. The transient performance of the system on a summer design day in Hong Kong was investigated. The results reflected the necessity of considering the influence of the former state on the following running of the system. In conclusion, the novel model could be a reliable tool to predicate the system operation and provide useful information for better control of the system.

EXPERIMENTAL STUDY OF DRYING BY THE SOLARIUM VARIABLE BAFFLE SENSOR OF YELLOW AND GREEN LEMON TO KEEP THESE VITAMINS FOR A LASTING AND NATURAL MEDICINAL THERAPY

The use of variable baffle solar panels for drying is the low level of heat exchange with the air in the dynamic vein of the solar panel. This weakness in such systems does not provide optimal performance or high thermal efficiency from their use. There is, however, a very noticeable improvement in heat transfer when the baffles are placed in rows in the ducts. To conduct the experiments, solar energy was simulated, the goal being to improve the relationship between temperature and thermal efficiency of a solar panel air heating plane and to use the system to reduce the time to gently dry the lemon to keep these vitamins. lemon and destinine for a sustainable therapy (the lemon promotes the absorption of calcium and in case of rhumet gill or five also to treat sinusitis, against migraine solair dryness and also for sustainable conservation and also for a sustainable medicine for a sustainable medicine.

Temperature correction of substrate moisture measurements made in coir in polytunnel-grown strawberries

The aim of this work is to assess the use of temperature corrected soil moisture data to improve the relationship between environmental drivers and the measurement of substrate moisture content in high porosity soil-free growing environments such as coir. Substrate moisture sensor data collected from strawberry plants grown in coir bags installed in a table-top system under a polytunnel illustrates the impact of temperature on capacitancebased moisture measurements. Substrate moisture measurements made in our coir arrangement possess the negative temperature coefficient of the permittivity of water where diurnal changes in moisture content oppose those of substrate temperature. The diurnal substrate temperature variation was seen to range from 7C to 25C resulting in a clearly observable temperature effect in substrate moisture content measurements during the 23 day test period. A temperature correction algorithm is presented in this work that has been derived from the Complex Refractive Index Model (CRIM) equation which was easily calibrated for coir and applied to the substrate moisture and temperature data. The diurnal variations seen with the temperature compensated substrate moisture data now align very well with the expected diurnal water demands of the strawberry plants. To further evaluate the relationship between environmental drivers of solar radiation and vapour pressure deficit with substrate moisture the temperature correction algorithm was programmed within a GP2 data logger. The GP2 was also collecting solar radiation, air temperature and relative humidity data. The resulting comparison of substrate moisture responses to environmental drivers illustrates a significantly improved correlation with temperature corrected substrate moisture measurements. We conclude that this new temperature correction algorithm addresses the effect of temperature on the relative permittivity of water which will affect all capacitance based sensor measurements in high porosity soil-free growing substrates such as coir.