South-facing Windows Research Articles

Operational power performance of south-facing vertical BIPV window system applied in office building

The purposes of this study are to analyze the power efficiency of BIPV system under actual operating condition and to reveal the factors of performance decrease through annual monitoring of the south-facing vertical BIPV window system (the capacity of 10.6kWp) whose performance was affected by partial shading.The study first investigated the monthly PR of each inverter to verify what caused the decrease in power performance by analyzing PR variation. Then, the shading analysis was performed using a simulation to analyze the capture loss of measured power performance and ultimately to find out the effect by partial shading components such as small overhang louvers of each floor, obstructions of adjacent building, and nearby hillock.The one-year measurement of the power performance showed that the annual average reference yield was 2.15h/day and the final yield was 1.52h/day; moreover, it was analyzed that the annual average capture loss was 0.49h/day and the system loss was 0.14h/day. Monthly average reference yield in summer (between April and August) showed only 1.28h/day which was 54% lower than the other seasons with average 2.77h/day. The annual average of PR was 0.69 (the monthly maximum of 0.77 and minimum of 0.58); the average PR in the summer with low reference yield was 0.64, while the average PR for other seasons was 0.73. Whereas monthly variation of LS (system loss) did not show big difference of under 9%, monthly LC (capture loss) highly varied with fluctuation. These primarily arise from the effect of the partial shading and vertically installed angle of south-facing BIPV modules.The BIPV system consisted of four arrays and installed on the same south façade. However, the power performance analysis per array showed that each array had different performances. The arrays located above the facade had the highest PR, from 0.74, 0.75, 0.66, and 0.62 respectively in order. In addition, LS and LC analysis of each array showed that there was performance difference mainly by LC, due to the influence of an adjacent building located in the south.The analysis using the simulation showed the adjacent building did not cast any shading but affected on decrease in diffuse solar radiation whose amount was depending on the array location. When it comes to the lowest array, nearly 7% of annual insolation was blocked by front building. The shading analysis, furthermore, revealed that the overhang louvers caused a partial shading problem in spite of short extrusion of 40mm depth all through the year, and particularly, showed a big effect during summer because of high solar altitude. The extruded louvers caused decrease in 4.5% of average insolation loss over the year.

Detailed and simplified window model and opening effects on optimal window size and heating need

The purpose of this study is to quantify the gap between the calculated energy need of a building model with simplified and detailed windows and suggest a method for reducing the gap. A model of a detached house in the cold climate of Estonia was composed and its energy needs with triple and quadruple windows was studied. The window sizes and opening strategies were also varied and all cases were modelled with simplified and detailed window models of which the latter were modelled pane by pane according to the methodology of ISO 15009. Simplified window models resulted in heating need lower by up to 7% and cooling need higher by up to 23%. The optimal window sizes of South facing triple windows remarkably depended on the glazing model and window opening strategy used. Therefore using simplified window models and inappropriate methodology might lead to inadequate facade design. In case of triple windows multiplying the U-value of simplified window models by 1.15 minimized the mismatch in calculated heating needs with different window models. It is recommended to use detailed window models to be used in simulations of mechanically cooled buildings.

Three approaches to optimize optical properties and size of a South-facing window for spatial Daylight Autonomy

This study presents optimization approaches by a recent Climate-Based-Daylight-Modeling tool, EvalDRC, to figure out the necessary area for a daylight redirecting micro-prism film (MPF) while minimizing the glazing area. The performance of a window in terms of spatial Daylight Autonomy (sDA) is optimized by its geometry and optical properties. Data implemented in simulation model are gathered through on-site measurements and Bidirectional-Scattering Distribution Function (BSDF) gonio-measurements. EvalDRC based on Radiance with a data driven model of the films' BSDF evaluates the window configurations in the whole year. The case to achieve an sDA of at least 75% is a South-facing window of a classroom in Switzerland. A window zone from 0.90 m to 1.80 m height provides view to the outside. The upper zone from 1.80 m to 3.60 m is divided into six areas of 0.30 m height in three optimization approaches including the operation of sunshades as well. First, the size of the clear glazing is incrementally reduced to find the smallest acceptable window-to-wall ratio (WWR). Second, micro-prism films are applied to an incrementally varying fraction the initial glazed area to determine the minimum film-to-window ratio (FWR). Finally, both approaches are combined for a minimum FWR and WWR. With clear glazing and WWR of 75%, the sDA of 70.2% fails to meet the requirements. An sDA of 86.4% and 80.8% can be achieved with WWR 75%, FWR 1/9 and WWR 50%, FWR 1/2 respectively. The results demonstrate the films' potential to improve the performance of windows with reduced WWR.

Collection and Storage of Solar Gains Incident on the Floor in a House During the Heating Season

Large amounts of south facing windows can help reduce heating demand in the winter and shoulder seasons by allowing high levels of solar radiation to enter the building. One problem that may arise from large areas of south facing glazing is overheating of the adjacent rooms, even during winter in a cold climate.Cooling of the floors may provide a means to prevent overheating in such a situation. Cooling a floor prevents solar gains absorbed by the floor from being transferred to the space by convection or infrared radiation. This cooling can be achieved with the use of water pipes in the floor. The heat removed can be upgraded to a higher temperature with a heat pump, and then may be stored in a thermal storage tank for space heating and domestic hot water heating.This paper shows preliminary simulation results of such a system for a house in Ottawa, Canada. The house contains a much larger south facing window area than is typical. In periods of overheating, the solar gains are absorbed by the floor cover and collected by the cold pipes in the floor. The heat is upgraded by a heat pump and stored in a hot storage tank.Preliminary modelling results show that, with the use of a large thermal storage tank (2 m3), space heatingand domestic hot water demand with this type of system may be reduced by as much as 24%, when compared with a more conventional house.

Energy conservation using solar collectors integrated with building louver shading devices

Solar collector plates are typically installed on roofs, but they can also be installed on the walls and windows of a building. Integrating solar collectors with shading devices that are installed on windows to block solar radiation extends the application of solar collectors. This study developed a prototype system integrating horizontal louver shading devices with solar collectors. Atmospheric data and the physical parameters of collector efficiency were recorded to examine collector performance. The results showed that the day collector efficiency, instantaneous efficiency, and collector efficiency coefficient satisfied Taiwan government standards. Consequently, integrating horizontal louver shading devices with solar collectors is feasible, but suitable only for south-facing windows.

The early design stage of a building envelope: Multi-objective search through heating, cooling and lighting energy performance analysis

The majority of decisions in the building design process are taken in the early design stage. This delicate phase presents the greatest opportunity to obtain high performance buildings, but pertinent performance information is needed for designers to be able to deal with multidisciplinary and contrasting objectives. In the present work, an integrative approach for the early stages of building design is proposed to obtain detailed information on energy efficient envelope configurations. By means of genetic algorithms, a multi-objective search was performed with the aim of minimising the energy need for heating, cooling and lighting of a case study. The investigation was carried out for an open space office building by varying number, position, shape and type of windows and the thickness of the masonry walls. The search was performed through an implementation of the NSGA-II algorithm, which was made capable of exchanging information with the EnergyPlus building energy simulation tool. The analyses were conducted both in absence and in presence of an urban context in the climates of Palermo, Torino, Frankfurt and Oslo. In addition, a preliminary analysis on the Pareto front solutions was performed to investigate the statistical variation of the values assumed by the input variables in all the non-dominated solutions. For the analysed case study, results highlighted a small overall Window-to-Wall Ratio (WWR) of the building in all locations. Pareto front solutions were characterised by low WWR values especially in east, west and north exposed facades. The area of the south facing windows was higher compared to the other orientations and characterised by a higher variability.

Modern insulation requirements change the rules of architectural design in low-energy homes

In the design of very well-insulated homes, there is a need for a more nuanced design that takes into account winter and summer conditions. In this paper, we compare a traditional design for a typical Danish single-family house with large glazing areas oriented towards the south and smaller glazing areas towards the north, and a design with an even window distribution where the glazing-to-floor ratio is the same for each room. We found that the use of solar gains through south-oriented windows is not as important as is traditionally believed because, in well-insulated homes, space heating demand is not reduced much by having larger south-facing windows. Furthermore, we found that there is a g-value above which the additional solar gains through south-oriented windows do not help reduce space heating demand, and it becomes important to use solar shading or glazing with solar-control coating as a cheaper alternative to reduce overheating. Maximum window sizes from an overheating perspective were identified that are larger than the optimal window sizes for space heating demand. However, we show that the difference in space heating demand with optimal window size and with larger window sizes is small, so it is up to the building owner to decide whether or not he wants larger glazing areas to allow for more daylight. And windows can be positioned in the façade with considerable architectural freedom. However, we do recommend an even distribution of the glazing-to-floor ratio, because this generally provides an improved thermal indoor environment in south-oriented rooms and will ensure a better daylight level especially in north-oriented rooms. We also show that the optimal window size is influenced by thermal zone configuration and that there is a need for models in which a difference is made between zones with direct and with non-direct solar gains.

Impact of passive cooling techniques on energy demand for residential buildings in a Mediterranean climate

This study presents the thermal analysis of a building prototype, which was designed and built in accordance with energy efficiency measures to improve indoor thermal comfort, particularly in summer. The building prototype is located in Souidania (20 km southwest of Algiers, latitude 36°7N, Longitude 03°2E). The location is characterized by a temperate Mediterranean climate. In order to perform this analysis, various activities are carried out: a series of monitoring campaigns; dynamic simulations with TRNSYS software, calibration of the model with experimental data and comparative study with buildings that use different wall constructions. Based on a validated building thermal model, dynamic analysis is carried out in order to evaluate the impact of thermal mass and of eaves and night ventilation. The results demonstrate that cooling energy demand is more affected by thermal transmittance values than by the envelope thermal mass. A recommended guideline for the optimum overhang length for south-facing windows is proposed. Ultimately, it is found that the combination of both natural ventilation and horizontal shading devices improves thermal comfort for occupants and significantly reduces cooling energy demand.

Floor Plan Analysis of Detached Houses for the Low-income Households

Energy poverty has been defined as low-income households who paid energy cost more than 10% of their ordinary income. Therefore, there are various subsidy programs focused on house remodeling for low-income households and one of them is the Home Energy Efficiency Assistance Program which have done by Korea Energy Foundation since 2007. The aim of the program is to improve the thermal performance of dilapidated dwellings and analyzed the detached house for the low-income households to develop the building typology. The database contained approximately 3,061 households which was obtained from the program in 2013 and the results of the study were like this; 1) For the shape of residential houses, the number of rectangular shaped building was higher than non-rectangular shaped ones. 2) For the orientation of buildings, the south layout of the detached housing was dominant to gain heating energy into buildings. 3) For the floor area, the average floor area was <TEX>$44.2m^2$</TEX>, although its size varied wide variations, which range from <TEX>$6.3m^2$</TEX> to <TEX>$107.1m^2$</TEX>. 4) For the windows and doors, the south-facing window was larger than the other side. Finally it would be possible to determine the characteristics of residential houses for low-income families. A future study could establish typology of low-income housing that it would estimate the performance of each model building before and after the retrofit to improve the energy performance.

The Effects of Orientations on the Room's Thermal Performance in the Tropics

Thermal performance of terrace house in Malaysia very much depends on the spatial design due to limited responsive environment factors. Building orientation is one of the important responsive factors under design consideration. The main concerns of the opening’s orientation are solar radiation and wind. In Malaysia, the maximum amount of solar radiation directly affects the thermal performance and thus the orientation of the window should be designed in the way to minimize solar gain and maximize natural ventilation. This paper investigates the effect of building orientation on the thermal performance of the residential room with solar chimney. The case study house facing north was located at Kuching, Sarawak, Malaysia. The field measurement was conducted in the case study house compound on 16 may 2012 to obtain the boundaries condition for CFD (Computational Fluid Dynamic) simulation. Four cardinal orientations were selected to investigate the thermal performance via CFD in DesignBuilder. The results show that the south facing window could maintain the lowest air temperature in the indoor environment with mean air temperature of 31.78°C and air mean velocity 0.023m/s with 35°C extreme outdoor temperature and zero wind velocity.

Genetic optimization of external fixed shading devices

In the present paper a genetic optimization (GO) has been carried out on an office room with a south facing window in order to design an optimal fixed shading device. Two different glazing systems have been taken into account, one standard double glass and an high performance glazing system specifically designed to prevent high sun loads. The shading device is a flat panel positioned parallel to the window and inclined by its horizontal axis. The device shades the window from direct sun penetration reducing the cooling loads in summer, but also affecting daylight and heat loads in winter limiting the sun gains, therefore the impact on the overall building energy consumption is investigated. A genetic optimization has been performed for identifying a possible geometry with the lower energy impact. Lighting loads, computed by the DAYSIM code, have been considered as inputs for the code ESP-r which drives the energy computation. The results demonstrate that electrical energy absorbed by the lighting system has to be always taken into account in designing energy efficient shading devices.

An investigation into the impact of movable solar shades on energy, indoor thermal and visual comfort improvements

Buildings are huge energy consumers and are responsible for a large part of greenhouse gas emissions in the world. Among building energy efficiency measures, solar shading plays a significant role in reducing building energy consumption, especially in hot summer and cold winter zone of China. This paper carried out a field measurement of shading performance of movable shades installed on the south-facing facade of a residential building in Ningbo city of China. The field tests show that external movable solar shades have a good shading performance that can reduce solar transmittance to about 8% and keep indoor illuminance at about 1000 lux with little fluctuations, indicating a suitable level for indoor environments. A building simulation study on energy, indoor thermal and visual performance of movable solar shades was further carried out. Several important indexes were adopted to give an in-depth analysis, including energy performance, room base temperature, transmitted solar radiation, PMV-PPD and its distribution as well as Discomfort Glare Index (DGI). Results show that movable solar shades used for south-facing windows not only reduce building energy demand by 30.87%, but also improve indoor thermal comfort by 21% in summer as well as reduce dramatically extremely uncomfortable risks by 80.4%, and meanwhile the visual comfort condition is also improved by 19.9%.

Case Study: Performance Assessment of Various Sun Shades for Hot-Dry Climate

There are many reasons to control the amount of sunlight admitted into a building. In warm, sunny climates excess solar gain may result in high cooling energy consumption. In cold and temperate climates winter sun entering south-facing windows can positively contribute to passive solar heating; and in nearly all climates controlling and diffusing natural Illumination will improve day lighting. A Well-designed sun control and shading devices can dramatically reduce building peak heat gain and cooling requirements and improve the Natural lighting quality of building interiors. In this casestudy Shading Devices commonly found in India are evaluated to find Optimized Shading Device for Hot-Dry Climate of South India

A vacuum tube based improved solar cooker

A new type of improved solar cooker based upon the use of a single vacuum tube is presented in this paper. The proposed cooker utilizes a solar collector consisting of parallel plane rectangular glass mirror strips mounted inside a wooden frame and requiring one dimensional solar tracking through a common driver. The proposed design can be either installed over the roof top of a house or near a south facing window (in countries of northern hemisphere). Temperatures as high as 250 C are attainable, making it suitable for all types of cooking. Due to larger collector area, the design offers substantially higher cooking power compared to other conventional solar cookers. Theoretical performance analysis and comparative experimental results at different times of the year with a 1.775 m 2 collector prototype have been included along with the cost/benefit analysis.

Residential Solar-Based Seasonal Thermal Storage Systems in Cold Climates: Building Envelope and Thermal Storage

The reduction of electricity use for heating and domestic hot water in cold climates can be achieved by: (1) reducing the heating loads through the improvement of the thermal performance of house envelopes, and (2) using solar energy through a residential solar-based thermal storage system. First, this paper presents the life cycle energy and cost analysis of a typical one-storey detached house, located in Montreal, Canada. Simulation of annual energy use is performed using the TRNSYS software. Second, several design alternatives with improved thermal resistance for walls, ceiling and windows, increased overall air tightness, and increased window-to-wall ratio of South facing windows are evaluated with respect to the life cycle energy use, life cycle emissions and life cycle cost. The solution that minimizes the energy demand is chosen as a reference house for the study of long-term thermal storage. Third, the computer simulation of a solar heating system with solar thermal collectors and long-term thermal storage capacity is presented. Finally, the life cycle cost and life cycle energy use of the solar combisystem are estimated for flat-plate solar collectors and evacuated tube solar collectors, respectively, for the economic and climatic conditions of this study.

Energy Saving Potential from Daylighting through External Multiple-Slat Shaded Window in the Tropics

Sunlight is strong and skylight is voluminous in the tropics. External multiple horizontal slats are simple but effective to shade the direct sunlight from north- and south-facing windows of a building in a tropical region. The device still allows the skylight to pass through and offers comfortable viewing from the interior to the exterior scene. This paper presents technical results of an experimental and simulation study on the use of such device with windows. The paper demonstrates an optimization of energy benefit from using such device on appropriate size of and suitable type of the glazed window.

Assessment of fixed shading devices with integrated PV for efficient energy use

The use of external fixed shading devices to adjust solar influx radiation and to save energy is well known. However, fixed shading devices can reduce daylight availability, increase artificial light needs and block the beneficial winter solar radiation.This paper is part of a research on the characteristics of the optimum shading device. The aim is to investigate the balance between the energy needs for heating and cooling the space that the shading device is used for and the energy that is used for lighting the same space and the energy that the shading device can produce.In order to investigate the balance between the above mentioned parameters, thirteen types of fixed shading devices have been studied and categorized according to their energy performance, for a single occupant office room. The same office room is tested for two different Mediterranean latitudes in Athens and in Chania, Crete in Greece and for two different south facing windows’ sizes.The thermal behavior of the devices is assessed through computer simulation application and the daylight analysis is assessed with both computer simulation and physical modeling. Stable parameters were the internal loads in the office room, the south orientation of the façade and the type of glazing. Variable parameter was the type of the fixed shading device.The study shows that all shading devices with integrated south facing PV can efficiently produce electricity which may be used for lighting. The study highlights the fact that shading devices such as Surrounding shading, Brise–Soleil full façade and Canopy inclined double work efficiently against thermal and cooling loads and may be used to produce sufficient electricity and control daylight. The study defines the geometrical parameters that will be incorporated to the overall characteristics of the optimum fixed shading device and proposes new fields of development for the BIPV technologies.

A Preliminary Study on the Performance of Daylight Responsive Dimming Systems with Improved Closed-Loop Control Algorithm

Daylight responsive dimming systems continuously adjust electric lighting output with an algorithm to maintain target illuminance levels at the workplane in combination with available daylight. A key factor of closed-loop proportional control algorithms is the ratio of photosensor response to daylight illuminance at the workplane. This ratio determines in part the control slope (M) between dimming level and lighting output. Although this ratio is known to vary significantly with sun and sky conditions, it is typically set to a fixed value at the time of calibration. Such practice adversely affects the accuracy and therefore reliability of these systems.To investigate how to improve performance, a solstice-to-solstice experiment was conducted in a conventional private office mockup with a large-area, south-facing window and a fixed height roller shade positioned to block direct sun for most hours of the year. This simple preliminary case was used to explore and define the methods for derivation of improved control algorithms with the intent of studying more complex cases in future work. First, variations in the ratio of photosensor signal to daylight workplane illuminance were analyzed using a divided time period, clearness index (KT) ratio, and the ratio of diffuse solar irradiance to global solar irradiance on an exterior horizontal surface (Id/IT). Second, an improved closed-loop proportional control algorithm was suggested based on least square fits to the experimental data assuming that commissioning would occur at targeted times. The performance of this improved algorithm was compared to a modified conventional control algorithm and found to deliver more reliable, accurate performance when commissioning was performed on two targeted days within the solstice-to-solstice period.For the improved control algorithm when calibrations were performed based on day of the year (June/December), the measured workplane illuminance levels did not fall below 90 percent of the design level for 98.4 percent of the test period. For improved control algorithm when calibrations were performed based on sky conditions (Id/IT ratio for clear and overcast), the measured workplane illuminance levels did not fall below 90 percent of the design level for 99.5 percent of the test period. This study indicates that improvements to the dimming control algorithm and commissioning practices can improve system accuracy and may increase market adoption of the daylight responsive dimming systems.

Albert Murray's Magical Youth

[ILLUSTRATION OMITTED] It's a short walk from 125th Street subway station to Harlem home of Albert Murray, Stanley Crouch's literary father man whom Henry Louis Gates Jr. dubbed King of Cats in New Yorker a few years ago. Murray, a student with Ralph Ellison at Tuskegee in 1930s later Ellison's sparring partner for decades (their long-running cultural dialogue was published in 2000 as Trading Twelves: The Selected Letters of Ralph Ellison Albert Murray), began publishing novels after he retired from Air Force in 1962. may be best known for his trilogy Train Whistle Guitar (1974), The Spyglass Tree (1991), The Seven League Boots (1996), but his critical writings include South to a Very Old Place (1972) From Briarpatch File: On Context, Procedure American Identity (2001), as well as countless articles. I was calling on him in my research for a documentary on Federal Writers' Project, his early friendship with Ellison. As I covered blocks I mentally retraced my phone calls with Murray, searching for some encouragement. Found none. was generally indifferent to questions about his friend's early days on Federal Writers' Project. Murray wasn't interested in politics and all that bullshit, he warned. But he was gracious enough to welcome a visit. I lowered my expectations kept walking. The apartment building dominated an otherwise patchy block. I signed in at desk took elevator up. Mrs. Murray let me in graciously before letting herself out to go to market. Their apartment was packed to transom with books artwork, including a striking collection of African art Romare Bearden prints of Ellington Ulysses. What dominated place, though, was spectacular south-facing window, wide as living room, its down-island vista of all Manhattan. Murray moved slowly used a walker, occasionally he rambled. But at ninety, his mind was agile. Out of nowhere, he launched into a discourse on Booker T. Washington's philosophy for Tuskegee, outlining the talented tenth idea, taking it back to Frederick Douglass, then forward to his own essay in From Briarpatch File, award he received as a notable Alabama writer. Not black writer! Alabama writer. was proud of that. gave an impersonation of Washington (Yes, Lord made Earth, but Dutch made Holland) laughed. said that Washington's point, missed by many of his detractors, was that blacks should work to secure their own property economic base. Murray remained uninterested in my list of questions. Emergency relief work on FDR's New Deal was too ideological for an artist, he said. Murray is famously allergic to labels, especially label of black writer, resents political baggage. knew Ellison not as a black writer, but as an artist intellect beyond categories, beyond simple views of race--like multiracial characters in Ellison's unfinished second novel, published posthumously in 2000 as Juneteenth this year as Three Days Before Shooting. Everybody's related in United States, see? Murray said. Everybody is part white part black ... Those abstractions [white black] get you around But epic literature of thing will deal with metaphors that help you to cope with complexity. [ILLUSTRATION OMITTED] When I asked about 1930s more generally, he directed me to a photo album across room. That's Tuskegee, 1939, he said, pointing to a photo of him in a suit, looking flash. That's way I dressed. The suit was from the swankiest store in Atlanta, a four-hour drive away. Long before Murray met Ellison to discuss books, he first noticed older boy because of his style. He was a junior when I was a freshman, Murray told me. Ellison had worked briefly at a haberdashery in Oklahoma City, which is what attracted me to him. …

Daylighting performance of an electrochromic window in a small scale test-cell

In this paper, the results of an experimental investigation aimed at assessing the performance of electrochromic (EC) windows with respect to daylighting control in buildings are presented. The research is performed under real weather conditions by a small scale test-cell equipped with a small area double glazing unit (DGU) where one pane consists of an EC device with visible transmittance τ v ranging from 6.2 to 68.1% and the other of an ordinary clear float glass ( τ v ≈90%). Experimental tests are carried out as a function of time, weather conditions, test-cell orientation and switching strategies. These data are integrated with spectrophotometric measurements. Results show that the angle selectivity of the glazing combined with its active switching effect allows a wide range of selectable transmission states to suit the latitude and orientation of a building in relation to the local climatic conditions. For south facing windows and under the involved climatic conditions EC glazing driven by a dynamic control strategy can be very effective in reducing discomfort glare caused by high window brightness. Glare reduction can be realized contemporarily maintaining the work plane illuminance to adequate level for computer based office tasks so without compromising much of the available daylight. Furthermore, since EC glazing is never switched to heavily darkened states ( τ v >20%), colour rendering of inside objects should be always acceptable, although internal illuminance level could be slightly lower than to what users prefer in relation to the correlated colour temperature of the incoming light. These results change when considering west orientation for which high-luminance direct sunlight patches are registered on the work-plane even for EC glazing switched to its lowest transmitting state letting suppose that EC windows cannot provide full control of uncomfortable direct sunlight effects without integration of additional shading devices.