KEYWORDS: Solar cells, Solar energy, Sun, Quantum efficiency, Photovoltaics, Lenticular lenses, Lens arrays, Design and modelling, Thin films, Renewable energy
Renewable energy has been on the forefront of our efforts to stop climate change, with solar power being a major focus. Within a given day, solar cell performance is higher around noon and lower during morning and evening hours. To maximize the performance of solar cells, many installations use mechanical tracking arrangements thus adding significant costs while reducing reliability. To improve the efficiency and make them independent of seasonal and daily variation, a novel curved solar cell array contoured to the inside of a hemisphere in conjunction with a specially designed domed lenticular lens is proposed. By contouring the solar cell with a curvature matching the “Petzval curvature” of the full optical system, the efficiency can be increased significantly provided the resulting irradiance remains in balance within the manufactured specification limits. By using proper combinations of curvature and specially designed optical assembly, the need for mechanical systems can be eliminated. Optical modeling was performed to determine optimal curvature and the optimal optical system. Efficiency of the solar cells were measured over three days at two hour intervals, as a base line, and was found to vary from 11.5% to 18%. Then, the optical system consisting of a Fresnel lens was positioned over the curved solar cell array. A 14% increase in peak efficiency was measured. The efficiency during morning and late afternoon also increased significantly over the base line, confirming the benefit of this apparatus. This innovative approach has the potential to increase the efficiency and reduce the cost of future solar panel installations.
The quality of an image captured by the human eye is typically better than that obtained relative to artificial images created by cameras or telescopes. This is because humans have curved retinas. In contrast, conventional imaging cameras have flat sensors that are not well matched to the curved focal surfaces of a camera lens or telescope objective. Thus, the image cannot be at the same focus across the entire sensor field of view. It is hypothesized that as the surface of the sensor approaches the curvature of the camera lens or telescope, the image quality increases. To test this, a commercially available ray tracing software was used. The curvatures were varied from flat (0 mm) to 12 mm. As the curvature reached 9 mm, the Petzval curvature, the quality of the captured images from the camera significantly improved. However, as the curvature increased beyond 9 mm, the quality of the artificial image decreased. In addition, a simulation of a classical Cassegrain telescope was also made. For the telescope, the curvatures were varied from 0 mm to 500 mm. As the curvature approached the telescope’s focal surface curvature of 350 mm, the distortion decreased. In addition to the optical simulations, two images were generated: one with a camera and the other by a reconstruction process. The latter was reconstructed by using the central part of images taken along that curve to create an image. A comparison of these images demonstrates the superior image produced with the latter method. Devices such as cameras and telescopes with curved focal plane array detectors produce images with higher quality than those produced using devices equipped with flat focal plane array detectors.
blair3sat is a student-run team based in Montgomery County, Maryland, developing a 3U CubeSat. The satellite will include the instrument suite SIRVLAS, which contains an optical instrument and a Radio Frequency (RF) instrument. The objective of the mission is to prove that a set of instruments like SIRVLAS in a CubeSatstyle satellite is able to generate a three-dimensional mapping of ionospheric electron density. The optical instrument will measure OI 777.4 nm emissions in the lower ionosphere in a limb view geometry. Since the 777.4 nm wavelength is emitted from the radiative recombination reaction of O+ and e-, its intensity is proportional to the square of the electron density. Therefore, by measuring the intensity of the 777.4 nm emission, electron densities may be calculated. These electron densities will be used as a reference for the data processing of RF signals. Specifically, correlation between the two instruments is performed through constrained optimization of known ray-tracing PDEs. Mappings of electron density in the ionosphere will allow for a better understanding of radio applications including radar and missile tracking, while allowing for the verification of current atmospheric and climatological models.
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