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- Energy production of solar DSF for ceiling-mounted localized air distribution systems in a virtual classroomPublication . Conceição, Eusébio; Gomes, João; Lúcio, Maria Manuela; Awbi, HazimThis paper presents an application of energy production in a solar Double Skin Facade (DSF) used in a Heating, Ventilation and Air-Conditioning (HVAC) system for a ceiling-mounted localized air distribution systems in a virtual classroom. In this numerical work, a virtual classroom, an inlet ceiling-mounted localized air distribution system, an exhaust ventilation system, and a DSF system are considered. The numerical simulations consider an integral building thermal response (BTR) and a coupling of an integral human thermal-physiology response (HTR) and differential computational fluid dynamics (CFD). The BTR numerical model calculates, among other parameters, the DSF indoor air temperature and energy production. The HTR numerical model calculates, among other parameters, the human thermal comfort. The CFD numerical model, among other parameters, calculates the indoor air quality. In this study which is performed for winter conditions, the energy produced in the DSF is used for driving the HVAC system. Six different airflow rates are used. The air temperature and energy production in the DSF are also evaluated. The influence of the airflow rate on the HVAC system performance is evaluated by the Air Distribution Index for mid-morning and mid-afternoon conditions. The results show that energy production reduces when the airflow increases and the operating point can be selected using the acceptable levels of thermal comfort and air quality levels or using the maximum Air Distribution Index value. In this study, the application of the thermal comfort and air quality levels criteria demonstrates that the HVAC system uses an optimum airflow rate.
- A neural network based intelligent predictive sensor for cloudiness, solar radiation and air temperaturePublication . Ferreira, Pedro M.; Gomes, João; Martins, Igor A. C.; Ruano, AntonioAccurate measurements of global solar radiation and atmospheric temperature, as well as the availability of the predictions of their evolution over time, are important for different areas of applications, such as agriculture, renewable energy and energy management, or thermal comfort in buildings. For this reason, an intelligent, light-weight and portable sensor was developed, using artificial neural network models as the time-series predictor mechanisms. These have been identified with the aid of a procedure based on the multi-objective genetic algorithm. As cloudiness is the most significant factor affecting the solar radiation reaching a particular location on the Earth surface, it has great impact on the performance of predictive solar radiation models for that location. This work also represents one step towards the improvement of such models by using ground-to-sky hemispherical colour digital images as a means to estimate cloudiness by the fraction of visible sky corresponding to clouds and to clear sky. The implementation of predictive models in the prototype has been validated and the system is able to function reliably, providing measurements and four-hour forecasts of cloudiness, solar radiation and air temperature.
- Production of thermal energy in university building greenhouses in cold climate conditionsPublication . Conceição, Eusébio; Gomes, João; Lúcio, Maria Manuela Jacinto Do Rosário; Awbi, HazimThe present work focuses on the production of thermal energy in University building greenhouses in cold climate conditions. The building model uses a system of energy and mass balance integral equations, which are solved by the Runge–Kutta–Felberg method with error control. This numerical study is about the thermal behaviour of a university building with complex topology, in winter and transient conditions. The thermal comfort of the occupants, using the Predicted Mean Vote index, and the indoor air quality, using the carbon dioxide concentration, are evaluated. This building has 319 compartments distributed by four floors and it is equipped with one internal greenhouse in the third floor. This greenhouse is located on the south facing facade and the heated air in this space will be transported to compartments located on the north facing façade. The spaces subject to the influence of the heated air coming from the greenhouse improve the level of thermal comfort of its occupants. The level of indoor air quality in occupied spaces is acceptable according to international standards.
- CloudspotterPublication . Gomes, João; Ferreira, P. M.; Ruano, AntonioDevido a uma crescente consciência ambiental, a nível global, têm vindo a fazer-se inúmeros esforços para reduzir o consumo energético e, consequentemente, a pegada de carbono deixada pela população mundial.
- Application of a school building thermal response numerical model in the evolution of the adaptive thermal comfort level in the mediterranean environmentPublication . Conceição, E. Z. E.; Nunes, A. R. L.; Gomes, João; Lúcio, Maria Manuela Jacinto Do RosárioIn this paper, a review is made of the adaptive thermal comfort model This is then applied and compared with the performance of the conventional thermal comfort model for a school located in a Mediterranean weather environment Measurement data, combined with a building thermal response numerical model, are used to define the comfort performance under ambient natural ventilation and passive conditions for various classrooms These results can then be used to identify the locations that require further measures to improve comfort, such as extra passive heat load and shading measures The school design is based on that of an actual school and consists of three buildings, with 94 rooms Envelope construction consists of opaque panels, 307 glazed window units and concrete floors and ceilings The adaptive method uses external and internal environmental variables Input data include occupation pattern and ventilation strategies External environmental variables include air temperature, relative humidity, wind velocity and wind direction Internal parameters include occupancy cycle, occupant activity level, clothing level, airflow rate and flow velocity Indoor ventilation conditions are based on the airflow rate and the air velocity values measured in real classrooms Environmental thermal comfort conditions were evaluated, in all occupied spaces, using the PMV index method of the Fanger model corrected with the adaptive model
- Comparative study of a clean technology based on DSF use in occupied buildings for improving comfort in winterPublication . EZE, Conceicão; Gomes, João; Lúcio, Maria Manuela Jacinto Do Rosário; Conceição, Maria Inês; Awbi, HazimThis paper presents a comparative study of a clean technology based on a DSF (double skin facade) used in winter conditions in the occupied buildings comfort improvement, namely the thermal comfort and air quality. The performance of a solar DSF system, the building’s thermal response, the internal thermal comfort and the internal air quality are evaluated. In this study, a DSF system, an air transport system and a HVAC (heating, ventilating and air conditioning) system based on mixing ventilation are used. The study considers a virtual chamber occupied by eight persons and equipped, in the outside environment, by three DSFs. A new horary pre-programming control methodology is developed and applied when the airflow rate is constant and the number of DSFs to operate is variable, when the airflow rate is variable and the number of DSFs to operate is constant and when the airflow rate is variable and the number of DSFs to operate is variable. This work uses a numerical model that simulates the integral building thermal behavior and an integral human thermal response. The internal air, provided by a mixing ventilating system, is warmed using the DSF system. The air temperature inside the DSF system and the virtual chamber, the thermal comfort level using the PMV index, the internal air quality using the carbon dioxide concentration and the uncomfortable hours are calculated for winter conditions. The results obtained show that the energy produced in the DSF, using solar radiation, guarantees acceptable thermal comfort conditions in the morning and in the afternoon. The indoor air quality obtained at the breathing level is acceptable. It is found that the airflow rate to be used is more decisive than the DSF operating methodology. However, when a solution is chosen that combines a ventilation rate with the number of DSF to operate, both variables throughout the day can obtain simultaneously better results for indoor air quality and thermal comfort according to the standards.
- Energy production in solar collectors in a university building used to improve the internal thermal conditions in winter conditionsPublication . Conceição, Eusébio; Gomes, João; Lúcio, Maria Manuela Jacinto Do Rosário; Awbi, HazimIn this numerical study the energy production in solar collectors in a University building used to improve the internal thermal conditions is made. Passive and active solutions, using external solar collector and internal thermo-convectors, are used. The numerical simulation, in transient conditions, is done for a winter typical day with clean sky. This numerical study was carried out using a software that simulates the Building Dynamic Response with complex topology in transient conditions. The software evaluates the human thermal comfort and indoor air quality levels that the occupants are subjected, Heated Ventilation and Air Conditioned energy consumption, indoor thermal variables and other parameters. The university building has 107 compartments and is located in a Mediterranean-type environment. External solar water collectors, placed above the building’s roof, and internal thermo-convectors of water/air type, using mixing ventilation, are used as passive and active strategies, respectively. The thermal comfort level, using the Predicted Mean Vote index, and the indoor air quality, using the carbon dioxide concentration, are evaluated. The results show that in winter conditions the solar collectors improve the thermal comfort conditions of the occupants. The indoor air quality, in all ventilated spaces, is also guaranteed.
- Application of a developed adaptive model in the evaluation of thermal comfort in ventilated kindergarten occupied spacesPublication . Conceição, E. Z. E.; Gomes, João; Antão, N. H.; Lucio, M. M. J. R.In this work the application of a developed adaptive model in the evaluation of thermal comfort in ventilated kindergarten occupied spaces is made. The study, conducted in real conditions, in mediterranean environment for cold and warm thermal conditions is made. The adaptive model is developed in a Kindergarten, using subjective and experimental measurements. Three different trained groups of subjects are used. Each one expressed its thermal subjective response, in different classrooms, for cold and warm thermal conditions. In the study, the classrooms are ventilated by natural airflow, while the indoor playground is ventilated by forced airflow. The natural airflow in the classrooms is measured using tracer gas decreasing concentration. The measurements are made for different window states, from close state to open state. In both warm and cold thermal conditions the simulation is made in real occupation and ventilation conditions. The natural ventilation is promoted, in both thermal conditions, using experimental measurements. In cold thermal conditions the forced airflow is done from the greenhouse to the indoor playground, while in warm thermal conditions the forced airflow is done in the opposite direction. In the thermal comfort level evaluation the developed adaptive model is used, while in the air quality level evaluation the carbon dioxide concentration released by the occupants is used. (C) 2011 Elsevier Ltd. All rights reserved.
- Influence of the airflow in a solar passive building on the indoor air quality and thermal comfort levelsPublication . Conceição, Eusébio; Gomes, João; Awbi, HazimThe influence of the airflow in a solar passive building on the indoor air quality and thermal comfort levels was investigated. The numerical study for a university library was conducted using a software that simulates the building thermal behavior with complex topology, in transient conditions, for evaluating the indoor air quality and occupants' thermal comfort levels for typical summer and winter days. Solar radiation was used as a renewable energy source to increase simultaneously the thermal comfort and air quality levels and reduce building energy consumption. Regarding the solar passive building, consideration was given to all of the building structure envelope, shading devices and interior details, while in the solar active building active ventilation was used. To analyze the airflow that simultaneously provides the best indoor air quality and thermal comfort levels, a new integral methodology based on the minimization of the total number of uncomfortable hours was used. The results show that it was possible to determine an air change rate that ensures a good compromise between thermal comfort and indoor air quality. An optimal air change rate of two and three renewals per hour had been determined, respectively, for winter and summer conditions.
- Spiral beacon calibration and experiments for underwater localizationPublication . Viegas, Rúben; Zabel, Friedrich; Gomes, João; Silva, AntónioUnderwater localization and navigation are still challenging tasks due to the underwater acoustic channel characteristics. Spiral sources are underwater transducers that create structured acoustic fields from which the angle to the source can be readily obtained. The angle estimation is obtained from the phase difference between transmitted circular and spiral fields, but for reliable operation the transducers must be properly calibrated. This paper presents a spiral source calibration procedure with the integration of a stepper motor to measure phase and amplitude features of the transmitted circular and spiral fields, at multiple bearing angles. The calibration was performed for two developed prototypes, which in turn determined the most appropriate operating frequency range. For one of the prototypes, its linearity was confirmed at all the tested frequency ranges through homogeneity and additivity tests. In addition to calibration, acoustic localization experiments were carried out with the transmission of circular and spiral fields, with a comparative analysis against footage captured from the top of the test pool. The phase difference of the mobile hydrophone was subtracted to the phase difference of the reference hydrophone to compute the angle between the spiral beacon and the mobile hydrophone. The localization results revealed noteworthy angular errors, hypothesized to be associated with the Doppler effect induced by the movement of the mobile hydrophone. These calibration and localization experiments suggest that spiral sources could be an important enabling technology for safe and reliable localization of underwater vehicles.