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We demonstrate a prototype for a compact, hybrid daylight harvesting system that collects and transports sunlight to illuminate dark spaces, up to two levels underground. The prototype is designed to have a compact size so that it can be mounted on top of a conventional lamp post at ground level and the system serves an additional purpose of a stre...
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... considerations behind light collection using optical fiber. Section 3 gives a lowlevel system design and fabrication details of the designed prototype. The measurement results for output optical power exiting the system and system performance are discussed in Section 4, followed by concluding remarks and possibilities of future work in Section 5. Fig. 2 shows the schematic of the designed daylight harvesting system. The system employs a clear solid acrylic ball (diameter D = 200 mm, weight 8 kg) as stationary solar collector. The ball acts as a lens and focusses the parallel rays of sunlight into a sharp focused spot at the rear end of the ball. The biggest advantage of using ball ...
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... fiber mount. Ideally, the ND filter should be a square-shaped one with a hole in the center for passage of focused light into the optical fiber, while blocking the light and heat on the sensors. We have cut the ND filter in four rectangular pieces and arranged the pieces onto the metallic plate leaving a square aperture in the middle as shown in Fig. 12. This arrangement covers the light sensors and expose the fiber end-face to capture the focused light ...
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... variation in output power within any two cycles of fine positioning, performed at one-minute time interval is less than 10%. The minimum illuminance variation that is perceptible by human eye is about 50% (Song et al, 2014) and therefore, the chosen one-minute interval (Section 2.3) between two cycles of finetuning the position of the fiber is found to be suitable for the optimum performance of the prototype. The system's performance has been tested ...
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... loss of the fiber is 0.13 dB/m, which amounts to nearly 45% loss in optical power. This loss can be halved if the prototype is used to transport light to one level underground utilizing 10 m length of optical fiber. The expected output optical power in the case of 10-meter fiber length is expected to be 300 Lumens, at 100 kLux solar illuminance. Fig. 20 shows a 2.2 m × 2.2 m × 2.5 m storeroom, before and after illuminated by the developed prototype using 20 m of fiber length; the inset shows the illuminated fiber end-face. The recommended distance between luminaire at ceiling to the ground for underground spaces in Singapore is 2.2 m (Development and Building Control, Singapore, ...
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... than 1 Lux. The maximum illuminance with the daylight harvesting setup was obtained at the point along nadir (a reference direction directly along the luminaire) and was measured to be 69 Lux at incident solar illuminance of 80 kLux. The corresponding instantaneous total optical power output at the fiber endface was measured to be 151 Lumens. Fig. 21 shows the variation of illuminance with distance from nadir and we note that the variation is linear. The radius of the illuminated spot with peripheral illuminance of 10 Lux is measured to be 2 m, corresponding to an illuminated area of 12.5 m 2 . The large, illuminated area can be attributed to the highly multimoded plastic optical ...
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... of 12.5 m 2 . The large, illuminated area can be attributed to the highly multimoded plastic optical fiber with a numerical aperture of 0.68, used in this prototype. The light from the fiber end-face is therefore expected to be diffuse with a superGaussian profile, and exiting in the cone of half-angle sin -1 (0.68) ~42.8 • (refer to inset of Fig. 21). Using this illumination angle, the theoretical estimate for the illuminated radius and corresponding illuminated area, at a work-plane 2.2 m away from the fiber end-face, is expected to be 2.04 m and 13 m 2 respectively. We note that the experimental results agree well with the theoretical ...
Citations
... The principal planes have been designated to coincide with the central point of the spherical lens. In accordance with the paraxial approximation, the determination of significant parameters such as the effective focal length (EFL) and the back focal length (BFL) is facilitated by the following expressions [21][22][23][24]: ...
In biochemistry, the absence of a compact, assembly-free pH sensor with high sensitivity and signal-to-noise ratio has been a persistent hurdle in achieving accurate pH measurements in real time, particularly in complex liquid environments. This manuscript introduces what we believe to be a novel solution in the form of a miniaturized pH sensor utilizing an assembly-free ball lens on a tapered multimode optical fiber (TMMF), offering the potential to revolutionize pH sensing in biochemical applications. A multimode optical fiber (MMF) was subjected to tapering processes, leading to the creation of an ultra-thin needle-like structure with a cross-sectional diameter of about 12.5 µm and a taper length of 3 mm. Subsequently, a ball lens possessing a diameter of 20 µm was fabricated at the apex of the taper. The resultant structure was coated utilizing the dip-coating technique, involving a composite mixture of epoxy and pH-sensitive dye, 2’,7’-bis(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF), thereby ensconcing the tapered ball lens with dye molecules for pH sensing. This study encompassed the fabrication and evaluation of six distinct fiber structures, incorporating the cleaved endface, the convex lens, and the ball lens structures to compare light focal lengths and propagation intensities. Computational simulations and numerical analyses were conducted to elucidate the encompassing light focal distances across the full array of lens configurations. The efficacy of the proposed pH sensor was subsequently assessed through its deployment within a complex liquid medium spanning a pH spectrum ranging from 6 to 8. Real-time data acquisition was performed with a fast response time of 0.5 seconds. A comparative analysis with a pH sensor predicated upon a single TMMF embedded with the fluorescent dye underscored the substantial signal enhancement achieved by the proposed system twice the fluorescence signal magnitude. The proposed assembly-free miniaturized pH sensor not only substantiates enhanced signal collection efficiency but also decisively addresses the persistent challenges of poor signal-to-noise ratio encountered within contemporary miniaturized pH probes.
... These varieties of (CPS) concentrators must be oriented in the direction of the sun in the sky. As a result, the system necessitates bulkier movement and heavy-duty motors with higher electrical energy consumption [8]. Andre Broessel created a spherical sun-tracking solar energy generator to generate sustainable energy while minimizing the use of tracking energy. ...
This research evaluates the optical properties of an inhomogeneous and non-paraxial system using a solar ball lens (SBL) as a new thermal solar concentrated collector. This evaluation is based on detecting a diacaustic curve in a straightforward and accurate manner, with the diagnostic relying on image processing as a computational tool using the MATLAB program rather than a complicated numerical analytic procedure. The circle of least confusion (CLC) of the (SBL), (Fluorinated ethylene propylene (FEP) polymer – water core), was calculated. Furthermore, the study evaluated the maximum geometrical concentration ratio (G C) of refracted solar radiation that can be captured by a receiver of the (SBL). Without energy losses due to spherical aberration, the (G C) ratio was (14.10) at (h/r) ratio, circular aperture radius to ball radius, around (0.6). The investigation also revealed an aplanatic point for preventing the development of optical envelope inside the solar ball lens at (h/r) equal to 0.8638, as well as a maximum (h/r) value of 0.7351 for collecting solar radiation.
The daylighting systems via polymethylmethacrylate (PMMA) plastic optical fibers have obvious cost advantages and have been widely studied. However, there is light leakage when PMMA optical fibers transmit concentrated sunlight, resulting in a transmission efficiency lower than the theoretical value. This research aims to quantitatively study the light leakage effect of PMMA optical fibers. Concentrated sunlight was used as the sunlight source instead of a monochromatic laser. An adjustable diaphragm was used to adjust the angle of the incident light, and the infrared filter and heat-absorbing glass were used to solve the overheating problem of PMMA fibers. The results show that when the incident angle is greater than 13°, the relative transmission efficiency of the fibers drops rapidly, which means that the light leakage deteriorates. The data also show that the angle of the output beam of PMMA optical fibers is ±30°, which is independent of the angle of the incident beam. Based on this conclusion, a PMMA optical fiber daylighting system with an incident angle of 13° was developed, which has higher transmission efficiency than previously developed systems. This study indicates that the angle effect of light leakage should be considered in the design of a plastic optical fiber daylighting system.
Translucent concrete (TC) is promising to transmit daylight into buildings with high thermal performance and energy-saving potential. However, most of the existing studies on TC omit its dynamic transmittance. More research is required to analyze the impact of dynamic transmittance on the optical and thermal performance of TC walls, and to investigate how to take advantage of this distinctive feature so that the building energy-saving potential of TC walls can be fully exploited. In this study, an optical and thermal model of TC embedded with optical fibers (OFs) was developed considering the dynamic transmittance of TC under the influence of solar incidence angle. The model was validated with experimental data. By using the model, the effects of numerical aperture (NA), fiber volumetric ratio (FVR) and solar incident angle on TC were revealed. In addition, a kind of novel TC with inclined OFs was proposed to achieve improved climate-responsive transmittance, which can reduce the dependence on high NA OFs. It was found that in Changsha the direct radiation transmittance of an OF (NA = 0.51, tilt angle = 60°) embedded in TC walls can be controlled within 0.20 in summer, while it can increase up to 0.90 in winter. Though the inclusion of OFs imposes an adverse effect on the wall insulation, TC walls can reduce daily heat loss by about 9.14% and increase daily heat gain by about 51.66% in winter, contributing to energy conservation in buildings.
Sunlight Concentrated and transmission for daylighting via optical fibers is a booming technology of direct utilization of solar energy. It uses optical fibers to introduce sunlight deep into building interior. In this work, a sunlight concentrating and transmitting system via plastic optical fibers was developed and tested. This study addressed the cooling problem of the plastic optical fibers under highly irradiation. Polymethylmethacrylate (PMMA) plastic fibers have a strong absorption effect on infrared light, which means that plastic fibers heat up so much when they transmit focused sunlight that they burn. In this study, a comprehensive cooling approach was developed to solve the overheating problem of plastic optical fibers, which consists of an infrared filter, cooling water and a homogenizer. The transmission efficiency of the system was measured to be about 15%. Experiments show that the comprehensive cooling measures developed can ensure that PMMA plastic optical fibers are in a safe temperature range. This shows that it is feasible to use low-cost plastic optical fibers instead of expensive silica fiber to transmit high flux for daylighting.
