Sun Patch Research Articles

On the mitigation of the overheating caused by floor heating systems exposed to long direct solar radiation and high occupation rates

This study investigates the effects of solar radiation and human metabolic heat due to occupation on the dynamic thermal response of glazed building's floor heating system (FHS), which may entail an indoor thermal discomfort. A full experiment was conducted on a real test cell to measure various parameters such as surface and floor-depth temperature, ambient and operative temperature, and relative humidity. The sun patch was experimentally simulated with a moving heating film placed on the surface of the radiant floor. The performance of the radiant floor was simulated using a TRNSYS® model in conjunction with SketchUp®. Once validated, the model was used to predict the test cell surface, ambient, and operative temperatures under four different scenarios related to the presence or absence of shading and/or occupant gains. Under the realistic climatic data of the city of Troyes (France), the results show that when the solar and occupants gains are considered on the heating slab, the indoor temperature reach the high value of 33.9 °C. A statistical approach based on Design of Experiments (DoE) method was used to perform sensitivity analysis and evaluate the effects of factors/design parameters such as heating pipe thickness, heating slab conductivity, specific heat capacity and density on surface and indoor air temperatures. Findings indicates that heating slab with 6 cm thickness, and with low conductivity and diffusivity leads to better FHS performances with no overheating/discomfort periods. The developed model could serve as a basis for any predictive adaptive control to mitigate the overheating problem.

Experimental evaluation of the impact of real sun patch on radiant floor heating in highly glazed spaces

When the floor heating system is integrated into highly glazed buildings, the uneven distribution of temperature and humidity caused by the long exposure to the direct solar radiation becomes more and more prominent, which affects the indoor thermal comfort. Given that this issue has already been studied by means of mainly numerical simulations in previous studies and that thermal comfort already needs to be considered by means of a questionnaire, leaving a large room for improvement in terms of experimental considerations. This study quantitatively and qualitatively analyses the evaluation of the impact of real moving sun patch on radiant floor heating for thermal comfort consideration. The effects of long exposure to sun patch on both thermal comfort and thermal sensation are objectively assessed by means of experimental measurements conducted on a thermal manikin placed in a controlled and monitored test cell exposed to non-controlled climatic conditions. The results show that the indoor air temperature exceeds 26 °C, even in winter season, when the sun patch appears and is exaggerated when its duration is extended. The decrease of floor surface temperature is positively correlated with the decrease of sun patch area. Extending the sun patch duration allows the heat absorbed by the floor increase the outlet water temperature and, thus, impact the thermal sensation and thermal comfort. Based on this, future contributions may be to eliminate overheating by combining ventilation systems, intelligent control systems, as well as to recover the radiant heat generated by the sun patch.

Experimental study on the effects of a moving sun patch on heating radiant slabs: The issue of occupants’ thermal comfort

In pursuit of a better indoor thermal environment, radiant heating systems have been widely employed in residential buildings. The effect of the sun patch on floor heating systems is increasingly attracting attention. However, the experimental study on the effect of a moving sun patch is often limited by weather conditions. This study proposes a method to simulate the moving sun patch by heating films in experiments and uses a thermal manikin to evaluate the indoor thermal comfort. The experiments were performed in Troyes, France, which belongs to a temperate oceanic climate. The obtained results show that a moving sun patch decreases the indoor thermal comfort from 1.5 to 1.1 away from comfortable in the case with 11.6% of window-to-wall ratio (WWR). Besides, concerning the overheating problems caused by the sun patch, two potential solutions are proposed. The indoor humidification solution could reduce air overheating duration by 74% in the case with 5.8% of WWR, and by 27% in the case with 11.6% of WWR, respectively. The solution with full return water could reduce the floor surface overheating duration by 40% and by 29%, respectively. In the future, the two solutions can be combined to alleviate the indoor overheating problems induced by the solar radiation.

The Impact of Sun Radiation on the Thermal Comfort in Highly Glazed Buildings Equipped with Floor Heating Systems

Occupants of highly glazed buildings often suffer from thermal discomfort during the mid-seasons when no shadings are used in such buildings, especially when inertial heating systems are used. The present study is devoted to evaluating the impact of long solar beam exposure on the internal thermal discomfort in glazed spaces when heating is implemented through a floor system. A comprehensive experimental study is carried out using an experimental bi-climatic chamber which is fully monitored and controlled, allowing realistic simulations of the dynamic movement of the sun patch on a heated slab. The findings show that a period of discomfort as long as 8 h can occur, and persist far after the sunbeam exposure stops. During this period, the heating slab’s surface temperature, considered from an average point of view, can attain 34°C while the indoor temperature reaches 26°C. Simulations conducted using a previously developed model display a good fit with the measurements.

Three-dimensional and high-resolution building energy simulation applied to phase change materials in a passive solar room

Phase change materials (PCMs) reduce energy consumption and improve indoor thermal comfort in buildings. Various numerical models have been developed to evaluate the thermal performance of the PCMs integrated into building enclosures. To remain computationally efficient, these models typically adopt a trade-off between the ability to investigate complex and realistic configurations and the prediction accuracy of the heat transfer associated with the phase change. This study developed a model to simulate a room with three-dimensional heat conduction in PCM-integrated walls and to analyze the surface heat balances with high resolution. The model was validated using experimental data of a passive solar test cell with a non-uniform and dynamic thermal environment. The model was then applied to investigate the PCMs integrated into the test cell during the summer. The PCM with a narrow phase change temperature range and a thickness of approximately 10mm was highly effective in reducing the indoor temperature fluctuations; the peak surface temperature was reduced by up to 6°C in the sun patch, and the operative temperature fluctuations decreased by up to 2.6°C. The PCM integration could be limited to the sun patch trajectory on the wall surfaces to optimize its utilization and limit the installation cost.

The Role of Light Shelf and Window Size on Daylight Performance of an Architecture Studio

Daylight affects our health and comfort. Recently, occupants face thermal and visual comfort problems due to the lack of solar control elements and improper design decisions of glazed surfaces. Recent studies show that solar control systems and window-based variables are some of the most significant variables which influence daylight performance. This study aims to test various combinations of window sizes and light shelf scenarios for a uniform distribution of daylight and visual comfort of occupants in two architecture studios in the İzmir Institute of Technology (IZTECH) Campus. In scenarios; window size and location, exterior and interior light shelves’ height, incline angle, and materials are tested. It is concluded that variables significantly improved the uniform distribution of daylight of both studios and sun patch areas of the south/east-oriented studio. Also, the artificial light requirement of the south/west-oriented studio is improved by 29.36% and 31.75% for the 21st of June and December respectively.

Experimental study on the thermal comfort in the room equipped with a radiant floor heating system exposed to direct solar radiation

In buildings with highly glazed facades, the main drawback of radiant floors is the overheating problem when exposed to direct solar radiation. Combined with local climate data from Troyes, an experimental investigation was performed under various exposure duration 2, 4, and 6 h with different solar intensity scenarios that were experimentally realized by a heating film. Indoor air temperatures and floor surface temperature were measured. Obtained results showed that the maximum floor surface temperatures all exceeded the limitation of 29 °C during the sunshine durations. When the sun patch was applied on the floor, the building type changed from category A to category B in terms of the vertical air temperature difference. To sum up, the sun patch indeed gave rise to floor overheating problems in the case of the existing control system, and the case of 6h sunshine duration with an intensity of 718 W/m2 would lead to the worst living conditions taking all factors consideration. The findings and insights of this study will provide an experimental database for designers and engineers.

Studies on how to counteract overheating caused by sun patch exposure in ventilated highly glazed spaces heated by floor heating systems

Enhancing the glazing areas in buildings could save energy by increasing solar gain and thus decreasing the demand for heating and artificial lighting during the cold season. However, relatively large glazed buildings often cause thermal discomfort to occupants due to the midseason heating, especially in the case of inertial heating systems. This study was conducted to examine the impact of direct solar radiation on the dynamic thermal behavior of a floor heating system. A series of experiments were conducted on a monitored full-scale controlled test cell facility simulating a dynamic sun patch on a radiant heating slab. A previously published bi-dimensional dynamic model based on the finite difference method was extended and validated to consider the additional heat flux brought by the sun patch. The findings show that the overheating time induced by the sun patch exposure was approximately 8.5 h after the disappearance of the solar patch. The average heating floor surface temperature attained 33.91 °C, whereas the indoor air temperature reached 26 °C. The conducted numerical parametric study revealed that when the sun patch occurs, ventilation remarkably decreases the indoor air temperature but keeps the average surface temperature almost unchanged and primarily over the standard upper limits. In contrast, water-based cooling technique appeared to be efficient under sun patch exposure since the average surface temperature and indoor air temperature can be decreased and maintained under acceptable limits in the average comfort zone.

Experimental study on the effects of direct sun radiation on the dynamic thermal behavior of a floor-heating system

Radiant floor heating systems (FHSs) are considered reliable heating systems since they maintain the indoor air temperature at the desired value and reduce its fluctuations more efficiently than conventional heating systems do. However, FHSs require an optimal control strategy especially when they are exposed to perturbations such as direct solar radiation or unscheduled crowding. The present study investigates the dynamic thermal response of a FHS exposed to a simulated direct solar radiation that is localized on its upper surface to quantify the potential effects of this exposure and identify the subsequent control issues of the FHS. Three experimental test scenarios were examined by varying the location of the sun patch and its duration. The experimental results show that the tested FHS, primarily regulated by controlling the indoor ambient air temperature, experiences a deficient regulation of the indoor temperature, which leads to an overheating period depending on the sun patch intensity and duration. An overheating of 4 °C compared with the recommended maximum desired value was recorded for duration of approximately 11.5 h after the sun patch was turned-off. The experimental results may be used in further numerical studies to predict the thermal behavior of FHSs exposed to sudden solar patches on their upper surfaces. The FHS design elements (material, thickness, etc.), as well as the control procedures, must be reconsidered to address the issue of overheating under such conditions.

A pixel counting technique for sun patch assessment within building enclosures

Pixel counting (PxC) emerged as a powerful technique for external solar shading calculations of buildings, providing accurate results with great computational efficiency even for dense geometries. Motivated by this fact and because the technique can be also adapted to cope with interior surfaces without further ado, this paper aims at experimentally evaluating the PxC technique implemented in Domus software for calculating sun patch distribution within building enclosures. For the validation purpose, digital images were taken from the surfaces of an experimental house to compare with the simulation results obtained by using EnergyPlus and two PxC based tools: Domus and Shading II SketchUp plug-in. This first task has shown that the PxC presents results in good agreement with the experimental data, in terms of both location and area of the sun patch. Also, a second case study was constructed to evaluate the capability of PxC for simulating non-convex zones with perforated shading elements. The results, in general, have shown that the PxC can provide accurate results in situations where polygon clipping based algorithms cannot be applied.

Adapted time step to the weather fluctuation on a three dimensional thermal transient numerical model with sun patch: Application to a low energy cell

In the case of highly efficient buildings the solar and internal gains have a higher impact on the energy balance than on classical constructions, with lower insulation.In this context, a model was developed which considers the three dimensional heat transfers through the walls. It simulates the transient behavior of rooms with the use of a refined spatial and temporal discretization and considers the projection of solar radiation through a window onto interior walls, referred to as sun patch. Validation of the model was carried out using experimental data from a low energy cell operating in a natural climate.Shorter sampling steps seem necessary to consider accurately the fluctuations of the weather data and the short dynamics of the systems such as the regulated heaters. In this paper, simulations with weather data at different time steps (1min, 10min and 1h) are going to be analyzed. The impact of the contribution regarding the adaptive and variable time step of the differential equation solver will also be shown. Finally, the impact of the different time steps on the accuracy of the low energy cell’s temperatures and heating loads will be discussed.

Study of the effect of sun patch on the transient thermal behaviour of a heating floor in Algeria

Solar radiation is a renewable non polluting energy source which can be used in buildings through various systems technologies. Thermal radiation, absorbed or transmitted by the walls and windows, creates a solar gain which has a direct impact on the thermal behavior in the building. Most existing thermal models neglect the effect of the evolution of the sun patch position on the heating floor which can have a great impact on the indoor thermal comfort.In this paper, we present numerical model to calculate the transient sun patch position and its influence on the heating floor model in order to evaluate its impact on the heating floor operating conditions and on the indoor air temperature, which has a great influence on thermal comfort under the climatic conditions of Oran city in Algeria. The sun patch is calculated using Ray Tracing model as proposed in FLUENT whereas the room and the heating floor are modelled with TRNSYS software.Using literature data, the two proposed models (sun patch model and heating floor model) are validated and used to simulate the cases with different geographic locations and different window orientations, surfaces, and positions. Our results suggest that the displacement of the sun patch on the heating floor lead to a superheating of the irradiated zone and it affects the indoor air temperature and thermal comfort too.

Impact of sun patch and three-dimensional heat transfer descriptions on the accuracy of a building’s thermal behavior prediction

A thermal transient numerical model (M3D) which considers the three-dimensional heat transfer through the envelope of a room and the sun patch through a window has been developed and validated in a recent paper. The use of a refined spatial and temporal discretization allows considering more precise interactions between the sun patch projection with the structure and quick time perturbations in the stresses. This is particularly necessary for highly insulated and low energy consumption buildings. In this new paper, M3D is subsequently transformed to simpler configurations, close to classical modelling thermal building simulation software that neglects the sun patch and the 3D heat transfer, in order to quantify the main contributions of this model. A first configuration is to consider one-dimensional heat conduction for the envelope and the transmitted solar radiation is only projected onto the floor (M1D). A second configuration considers also one-dimensional heat conduction but the transmitted beam radiation falls on each wall or floor that is impacted (M1D,sp). Comparison between experimental data and numerical results of these three models shows, as expected, that M1D and M1D,sp are less accurate than M3D. This is particularly true when wanting to evaluate surface temperature distributions or heating power evolution in winter.

Development and validation of a three dimensional thermal transient numerical model with sun patch: Application to a low energy cell

High performance simulation of low energy building requires ever more accurate descriptions of the systems under study to improve the building's performance. This paper describes a numerical model to simulate a single room, using a three-dimensional description of heat conduction in the envelope with environmental conditions that vary over short time-steps are described. The simulation considers the projection of solar radiation through a window onto interior walls. The indoor air temperature is assumed to be uniform. The temperature of the inner and outer surface of the walls are calculated at each time step using a variable-step solver. Validation of the model was carried out using experimental data from a low energy cell operating in a natural climate. A set of well-calibrated temperature sensors and an infrared camera have been used to accurately measure the cell's thermal behavior. Comparison between experimental data and numerical results for free varying conditions shows good agreement and the reliability of the model is proven.These validated results were found for a highly insulated cell. Future studies for different thermal mass cells, with new materials, will be realized to show the contribution of this model. Thermal comfort will also be studied.

Investigation of declared seating preference and measured cognitive performance in a sunlit room

Current daylighting standards are not sufficient to guarantee a high-quality daylighting experience as they fail to take the behavior of building occupants into consideration. The way that a daylit room is appreciated and used has not been fully explored, especially under sunlighting conditions. This research is the first of its kind to assess how the distance between a subject and a sun patch on the floor is related to a broad range of behavioral responses, including conclusive preference and measured cognitive performance. One hundred subjects participated in a controlled experiment in a work setting. Investigations of the declared preferences of seating area and subjects' cognitive performances indicated that people are not always aware of the environmental factors that influence their behavior. Subjects were generally attracted to sunlight and outdoor views, but they did not necessarily perform best in these preferred areas. Privacy and a sense of control were two hidden factors that greatly affected subjects' decisions and performances. Current daylighting literature and design practice do not pay adequate attention to such factors as sense of visual control or privacy in the design of rooms. On the other hand, the perceived problem of visual glare caused by sunlight penetration did not affect performance as much as subjects believed it would. An additional result suggested that individual behaviors were more affected by environmental elements than were group activities.

The effect of floor heat source area on the induced airflow in a room

We examine the role of heat source geometry in determining rates of airflow and thermal stratification in natural displacement ventilation flows. We modify existing models to account for heat sources of finite (non-zero) area, such as formed by a sun patch warming the floor of a room. Our model allows for predictions of the steady stratification and ventilation flow rates that develop in a room due to a circular heat source at floor level. We compare our theoretical predictions with predictions for the limiting cases of a point source of heat (yielding a stratified interior), and a uniformly heated floor (yielding a mixed interior). Our theory shows a smooth transition between these two limits, which themselves result in extremes of ventilation, as the ratio of the heat source radius to the room height increases. Our model for the transition from displacement to mixing ventilation is compared to previous work and demonstrates that the transition can occur for smaller sources than previously thought, particularly for rooms with large floor area compared to ceiling height.

Validation of the Belgian single-patch sky and sun simulator

This study considers the validation of the Belgian sky and sun simulator that uses the daylight coefficient method to predict illuminance in architectural scale models. The validation work includes comparisons between the measured and the calculated illuminance values for CIE overcast skies, for a CIE clear sky without sun, and for the sun alone. The measurements were made in a simple rectangular scale model and the numerical simulations were carried out by Superlite and RADIANCE. The comparison of mock-up measurements under the single-patch sky simulator (SPS) and the mirror box (MB) to RADIANCE predicted values produced low-root-mean-square errors (RMSEs) (with a maximum RMSE of 17.5% for the simulator and 22.7% for the MB) and low positive mean bias errors (MBEs) (maximum values of 8.5% and 13.3%, respectively). Although the sun patch size was slightly overestimated, especially at low-sun altitudes, the results were reliable and in accordance with the sun simulator's objectives. Parallax error measurements were undertaken, and these led to a restriction of the model size in order to limit the error to 12.5% for a CIE overcast sky.

Validation of a glazed space simulation model using full-scale experimental data

The application of classical building-energy simulation programs is not appropriate for glazed spaces because of their particularities (as the transmission of solar radiation through windows as well as reflection and absorption). Consequently, modifications must be performed in order to correctly describe the thermal behavior of the sunspace and its (possible) coupling with the attached construction. This study presents the integration of a veranda model within the Clim2000 software designed for dynamic building energy modeling. We first introduce the model main hypotheses with focus on a simplified approach concerning the sun patch location. The proposed method is compared to an exact technique of sun patch representation. The results issued from the confrontation show that the simplified method has an excellent precision. Moreover, the complete sunspace numerical model was tested by means of full-scale experimental building. A detailed description of the experimental set-up is given, emphasizing the sky temperature acquisition and the air temperature measurement inside the experimental sunspace. Three veranda configurations were carried out: simple veranda, veranda with shutters and veranda with horizontal mask on the roof. The numerical results achieved were satisfactory comparing to experimental data. Nevertheless, additional systematically work (using sensitivity analysis) must be performed to investigate the inputs impact (particularly the sky temperature) on model predictions.

History Means Often Having to Say You're Sorry

MY DOG DIED THIS MORNING. Tazzy had not been ill. In fact, she had been playful and happy on her morning walk, not an hour before she followed me upstairs, found a sun patch to lie in, and died. Playful and happy had been normal for her recently, but certainly not always. Just six months ago, almost to the day, I snatched her from Highway 101, onto which she, in her near starvation, had apparently wandered in search of food. She was skinny, very skinny. Dehydrated. Dirty. Wormy. And sweet. As eager to get into the backseat of my car as I was to get her home and start getting her healthy, start the process of historic reconciliation for whatever those injustices and neglect had been that she, clearly, had suffered through the hands of other members of this human species. I was sorry then for the state she was in, although I had not caused it. And I am sorry now that her time of love and plenty was so short, although I am sure that it would not have been even six months had I not come along. As I mourn the passing of this innocent life that possessed all of the loyal, funny, and dear attributes that we associate with a true dog friend, I find myself repeating, “I am sorry. I am sorry.” But, for what should I be sorry? I am the heroine here, am I not? The kind rescuer. The rectifier. For what should I feel responsible, other than helping this creature have some pleasure in life? But symbolism, responsibility, and regret are deeply rooted, nonrational phenomena, not easily subject to the empiricism that would allow me to take comfort in, say, comparing the dog’s weight today with her weight six months ago. Surely I was motivated to create a relationship with this forlorn dog—not even just to be a Good Samaritan by taking her to the pound—through some sense of moral

EFFICIENCY OF AN INVERSE METHOD TO DETERMINE NATURAL-CONVECTION HEAT

The final aim of this study is to identify the value of convective heat transfer generated by a local perturbation analog to a sun patch. A first approach to this work consisted of developing a means of evaluating the local heat transfer based on the use of an inverse method. We first chose the well-known academic case of a vertical heated plane plate to generate natural heat convection transfer. Then, for several temperatures of the plate, a first validation of the chosen inverse method was obtained in the steady state. It consisted of a comparison between the results provided by the inverse method and those obtained by the use of thermocouples to measure the temperature inside the boundary layer. These two types of results are also compared with relations published in the literature. In conclusion, the authors observe that the inverse method is pertinent and gives satisfactory results.