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Open accessJournal ArticleDOI: 10.3390/IJERPH18052574

A Study of Optimal Specifications for Light Shelves with Photovoltaic Modules to Improve Indoor Comfort and Save Building Energy.

04 Mar 2021-International Journal of Environmental Research and Public Health (MDPI AG)-Vol. 18, Iss: 5, pp 2574
Abstract: Recent studies on light shelves found that building energy efficiency could be maximized by applying photovoltaic (PV) modules to light shelf reflectors. Although PV modules generate a substantial amount of heat and change the consumption of indoor heating and cooling energy, performance evaluations carried out thus far have not considered these factors. This study validated the effectiveness of PV module light shelves and determined optimal specifications while considering heating and cooling energy savings. A full-scale testbed was built to evaluate performance according to light shelf variables. The uniformity ratio was found to improve according to the light shelf angle value and decreased as the PV module installation area increased. It was determined that PV modules should be considered in the design of light shelves as their daylighting and concentration efficiency change according to their angles. PV modules installed on light shelves were also found to change the indoor cooling and heating environment; the degree of such change increased as the area of the PV module increased. Lastly, light shelf specifications for reducing building energy, including heating and cooling energy, were not found to apply to PV modules since PV modules on light shelf reflectors increase building energy consumption.

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Topics: Photovoltaic system (55%), Daylighting (53%)
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5 results found


Open accessJournal ArticleDOI: 10.3390/SU13158251
23 Jul 2021-Sustainability
Abstract: The achievement of sustainable cities and communities is closely linked to an accurate design of the buildings. In this context, the transparent elements of the building envelope have a crucial role since, on one hand, they are a bottleneck in regards to heat and mass transfers and sound propagation, while, on the other hand, they must allow daylight penetration. Thus, they are responsible for occupants’ thermal and visual comfort and their health. Considering passive solutions for windows, the light shelves can improve natural light penetration, reducing the lights’ electricity demand and controlling windows’ related thermal aspects. The scientific literature is characterized by several studies that analyze this topic, which, however, focus only on the daylight field and sometimes the energy saving for lights. Moreover, they often refer to fixed sky type for the simulations. The aim of the present study is to analyze the application of the light shelves with a multi-disciplinary approach, by means of dynamic simulations, in the EnergyPlus engine, for a whole year. A new methodological approach is presented in order to investigate the technology under different fields of interest: daylight, lighting energy, cooling and heating needs, and thermo-hygrometric comfort. The case study chosen is an existing building, a student dormitory belonging to the University of Athens. It is subject to a deep energy renovation to conform to the “nearly Zero Energy Building” target, in the frame of a European research project called Pro-GET-onE (G.A No. 723747). By means of the calibrated numerical model of this HVAC–building system, ten different configurations of light shelves have been investigated. The best solution is given by the application of an internal horizontal light shelf placed at 50 cm from the top of the window with a depth of 90 or 60 cm. It has been found that despite the reduction in electricity demand for lighting, the variation in heating and cooling needs does not always lead to a benefit.

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Topics: Daylighting (62%), Zero-energy building (56%), Daylight (54%) ... read more

1 Citations


Open accessJournal ArticleDOI: 10.3390/EN14238013
30 Nov 2021-Energies
Abstract: Window design affects the overall performance of a building. It is important to include window design during the initial stages of a project since it influences the performance of daylight and thermal comfort as well as the energy demand for heating and cooling. The Norwegian building code facilitates two alternative methods for achieving a sufficient daylight, and only guidelines for adequate indoor thermal comfort. In this study, a typical Norwegian residential building was modeled to investigate whether the criteria and methods facilitate consistent and good performance through different scenario changes and furthermore, how the national regulations compare to European standards. A better insulated and more air-tight building has usually a lower annual heating demand, with only a marginal decrease in the daylight performance when the window design is unchanged. A more air-tight construction increases the risk of overheating, even in cold climates. This study confirms that a revision of the window design improves the overall performance of a building, which highlights the importance of proper window design. The pursuit of lower energy demand should not be at the expense of indoor thermal comfort considering the anticipated future weather conditions. This study indicates that criteria for thermal comfort and daylight, if clearly defined, can affect the energy demand for heating and cooling, as well as the indoor climate positively, and should be taken into account at the national level. A comparison between the national regulations and the European standards was made, and this study found that the results are not consistent.

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Topics: Daylight (58%), Thermal comfort (55%)

Open accessJournal ArticleDOI: 10.3390/BUILDINGS11110494
20 Oct 2021-Buildings
Abstract: The present study investigates the issue of computer-aided daylight evaluation in an office room with a light shelf and dropped translucent ceiling. In this type of room, daylight is admitted from two sources: (i) a standard window in the wall and (ii) via a light shelf and clerestory window, which illuminate the plenum located above the working space. The light from the plenum is transmitted through the translucent ceiling into the office room. The present study is based on data obtained through a computer-aided daylight simulation by DeLuminae (DL-Light, ver. 11.0.9, and DL-Instant, ver. 6.1.4) software using the Radiance engine and real weather data for Wroclaw, Poland, at 51st lat. N. An office room of 12 × 6 m with different shading and daylight distribution scenarios was simulated (Variants 1–5). Next, the useful daylight illuminance (UDI (%)) for the range of 300–3000 lx and daylight glare probability (DGP) were calculated. To further optimize the daylighting scenarios, an adaptive shading system was simulated, which was activated when the illuminance value dropped below 300 lx. In the final variant, Variant 6, mean UDI300–3000 values were recorded to be above 80% for 95% of the area of the work plane. This allows the conclusion that a light shelf and translucent ceiling guide daylight deep into the room, improving uniformity and reducing glare when the standard window is covered by an adaptive shading system.

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Topics: Daylight (64%), Daylighting (63%)

Open accessJournal ArticleDOI: 10.3390/SU13168816
06 Aug 2021-Sustainability
Abstract: In modern society, humans spend most of their time in the indoor environment (home, work, school...). This indoor lifestyle constantly poses challenges to our physical and mental health by affecting our hormone levels and circadian rhythm. This article deals with the possible connection between human and working environment factors and the emergence of health problems in connection with work. Using statistical methods, the dependence between the six characteristics (age, length of employment, visual demand of the work task, satisfaction with lighting conditions, and shift work) and occurrence of health-related problems and discomfort (i.e., eye discomfort, headache, eye fatigue, and seasonal affective disorder symptoms) was examined. The paper also deals with the evaluation of lighting conditions in the workshop using the lighting design software DIALux evo 9.2. Using this software, two lighting variants were modeled. The first simulated variant included lighting parameters according to the currently used luminaries and the second variant contained more efficient LED luminaries.

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Topics: Shift work (50%)

Journal ArticleDOI: 10.1016/J.BUILDENV.2021.108481
Hyunmin Lee1, Heangwoo Lee1Institutions (1)
Abstract: There is a growing concern about the skyrocketing amount of energy required for lighting in buildings. Therefore, research is being conducted on light shelves, which are natural daylighting systems. Recent studies have attempted to integrate photovoltaic (PV) modules into light shelves; however, installing the modules on reflectors degrades the daylighting performance. Therefore, this study applied PV modules on curved light shelves to improve both the daylighting performance and concentration efficiency and proved their effectiveness using a full-scale testbed. The main findings are listed as follows. 1) This study proposes a method to apply PV modules to the bottom of light shelves to improve the performance of curved light shelves. 2) The daylighting performance of curved light shelves is superior to that of flat light shelves; however, high curvature angles degrade the daylighting performance. 3) Installing PV modules on the top of flat light shelves saves energy by concentrating light; however, this approach reduces the area for reflectors and hinders the daylighting performance. 4) Installing PV modules on the bottom of curved light shelves saves energy by 6.1%–25.3% compared with conventional light shelves and creates a comfortable light environment.

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Topics: Daylighting (60%)
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Journal ArticleDOI: 10.1016/J.APENERGY.2014.04.106
15 Sep 2014-Applied Energy
Abstract: This study evaluates the effects of electrical and optical parameters of building integrated photovoltaic (BIPV) windows with a semi-transparent solar cell on the overall energy performance of a typical mid-sized commercial building in various climate conditions. For precise evaluation of thermo-optical performance of the BIPV windows, we have fabricated semi-transparent amorphous silicon (a-Si:H) solar cells in various conditions and evaluated optical properties of the cells in addition to the energy conversion efficiency. More importantly, we have taken optical parameters of the cells in different sun wavelength spectra on the front and back side of the cell because optical response at each wavelength affects differently on the energy conversion efficiency of the cell and thermal properties of BIPV windows. By using three different semi-transparent solar cell types, the annual whole building energy simulation was performed to evaluate the BIPV window performance in six different climate conditions. A significant change in the overall building energy consumption was observed by varying the thermo-optical characteristics of BIPV windows. Our results suggest it is required to customize the BIPV window characteristics with real optical data through sun wavelength spectra which is sensitively varying by the fabrication conditions of solar cells, in order to maximize building energy performance for different climate conditions at the building location.

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166 Citations


Journal ArticleDOI: 10.1016/J.ENBUILD.2017.01.068
Ganga A. Warrier1, Benny Raphael1Institutions (1)
Abstract: This paper aims to objectively evaluate the potential of light shelves to improve daylighting and visual comfort. This study consists of two parts. The first part is experimental and involves measurements taken on a scaled prototype. More than one million data points were collected using illuminance sensors installed on a test chamber. The data was analyzed statistically and the performance of the light shelf was evaluated for various configurations. A horizontal light shelf is found to increase the illuminance in the interior by an average of 21%. By rotating the external light shelf to an optimal angle, up to 300% increase in illuminance can be achieved. The second part of the study consists of purely theoretical simulations. Some new metrics such as useful daylight enhancement (UDLE) were developed specifically to evaluate the daylighting performances of light shelves. A case study of a hypothetical building in Chennai is taken and simulations are performed using Radiance lighting simulation software. 1080 simulations were performed under various configurations. It is found that most of the common assumptions about the performance of light shelves are not supported by simulation results. Even though, in many cases, the horizontal light shelf is able to improve illuminance at distances greater than the height of the window, the area where there is useful daylight enhancement is low. It is commonly assumed that light shelf provides shading near the window, thus eliminating glare. However, in 30% of the simulated cases, horizontal light shelves are found to increase the illuminance near the window, thereby increasing the possibility of glare. Light shelf is also found to decrease the uniformity in illuminance. These problems can be eliminated by using a rotatable light shelf.

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Topics: Daylighting (61%), Illuminance (54%), Daylight (51%)

27 Citations


Journal ArticleDOI: 10.1016/J.RENENE.2019.12.133
Somil Yadav1, Sarat Kumar Panda1Institutions (1)
01 May 2020-Renewable Energy
Abstract: In the present study, the thermal performance has been evaluated for optimally tilted semi-transparent BIPV panel, which is fixed as a roof system on a two-storied single room sample building. In the mathematical model, the periodic nature of insolation, ambient air temperature, BIPV cell temperature, intermittent slab temperature, and room temperature have been considered while solving energy equilibrium differential equations. The insolation values used in the model are computed by using periodic HDKR (Hay, Davies, Klucher and Reindl) model, which is based on anisotropic sky concept. The influencing parameters i.e., air changes in both rooms of the two-storied BIPV thermal system, packing factor of the BIPV panel and the thickness of slab between rooms are considered for finding the thermal performance. It is observed that the most critical day of the year i.e., on 15th May, the upper storey and lower storey of the proposed BIPV system attains the highest room temperature of 47.3 °C and 42.6 °C, respectively. The air changes in the rooms reduce the above peak temperature for making it more comfortable. The BIPV cell temperature also reaches up to 65 °C resulting reduction of the efficiency by 18% than that of standard test condition.

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14 Citations



Open accessJournal ArticleDOI: 10.3390/EN13102549
18 May 2020-Energies
Abstract: Based on a method to reduce energy consumption suggested in a real energy audit carried out in an industrial plant located in Poznan (city in Poland), the potential of using photovoltaic (PV) panels as wall cladding was analyzed, in order to reduce energy (electric and thermal) consumption and financial expenditure. The authors’ concept of using building integrated photovoltaic installation (BIPV) was presented and tested. This study checked whether the presence of PV modules would also affect heat transfer through the external wall of the building on which the installation is located. The analysis consisted of determining, for two variants, the heat transfer coefficients across the partition, in order to estimate the potential thermal energy savings. The first variant concerned the existing state, i.e., heat transfer through the external wall of the building, while the second included an additional partition layer in the form of photovoltaic panels. As a result, the use of panels as wall cladding allowed the improvement of the thermal parameters of the building wall (by increasing the thermal resistance of the wall), and the reduction of gas consumption for heating. The panels also generate electricity for the factory’s own needs. Payback time, compared to calculations which do not include changes in thermal parameters, was shortened from 14 to 11 years. The main reason for this is that gas consumption is reduced due to the improved heat transfer coefficient of the wall and the reduction of the heat loss of the facility. This aspect is usually overlooked when considering photovoltaic installations and, as argued by this paper, can be important.

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Topics: Building-integrated photovoltaics (62%), Thermal energy (59%), Heat transfer (56%) ... read more

14 Citations


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