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Double lens collimator solar feedback sensor and master slave configuration: Development of compact and low cost two axis solar tracking system for CPV applications(Solar Energy, Elsevier BV, 2016-08-31) [Article]The conventional CPV systems, as big unit design, are only suitable to be installed in the open regions, like desert areas. This gigantic system design restricts their use on the rooftop of commercial and residential buildings, unlike the conventional PV systems. This paper proposes a compact but highly accurate and cheap two axis solar tracking system, designed for CPV system field operation. The proposed system is designed and verified for tracking accuracy requirement of 0.3 degrees, and has maximum capability of as high as 0.1 degrees tracking accuracy. High tracking accuracy is ensured using in-house built double lens collimator solar feedback sensor, within a fraction of the cost of commercial solar tracking sensors. A hybrid tracking algorithm is developed in C-programming using astronomical and optical solar tracking methods. As compact CPV system design demands larger number of tracking units, for same power capacity of system. Therefore, a master slave control configuration is also proposed for the CPV field operation. Only master tracker will be equipped with the expensive tracking devices, while the required tracking information will be sent to all of the slave trackers using wireless communication through ZigBee devices. With detailed optical design, simulation and control strategy, a prototype of the proposed CPV tracking system is developed, experimentally investigated and verified for tracking accuracy for outdoor operation at the rooftop. (C) 2016 Elsevier Ltd. All rights reserved.
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Nature-Inspired, 3D Origami Solar Steam Generator toward Near Full Utilization of Solar Energy(ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2018-08-15) [Article]Solar steam generation, due to its capability of producing clean water directly by solar energy, is emerging as a promising eco-friendly and energy-efficient technology to address global challenges of water crisis and energy shortage. Although diverse materials and architectures have been explored to improve solar energy utilization, high efficiency in solar steam generation could be accomplished only with external optical and thermal management. For the first time, we report a deployable, three-dimensional (3D) origami-based solar steam generator capable of near full utilization of solar energy. This auxetic platform is designed based on Miura-ori tessellation and is able to efficiently recover radiative and convective heat loss as well as to trap solar energy via its periodic concavity pattern. The 3D solar steam generator device with a nanocarbon composite of graphene oxide and carbon nanotubes being photothermal component in this work shows a very strong dependence between its solar energy efficiency and surface areal density. The device yields an extraordinary solar energy efficiency close to 100% under 1 sun illumination at a highly folded configuration. The 3D origami device can withstand a great number of folding and unfolding cycles and shows unimpaired solar steam generation performances. The unique structural feature of the 3D origami structure offers a new insight into the future development of highly efficient and easily deployable solar steam generator.
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The effect of anneal, solar irradiation and humidity on the adhesion/cohesion properties of P3HT:PCBM based inverted polymer solar cells(2012 38th IEEE Photovoltaic Specialists Conference, Institute of Electrical and Electronics Engineers (IEEE), 2012-06) [Conference Paper]We use a thin-film adhesion technique that enables us to precisely measure the energy required to separate adjacent layers in OPV cells. We demonstrate the presence of weak interfaces in prototypical inverted polymer solar cells, either prepared by spin, spray or slot-die coating, including flexible and non flexible solar cells. In all cases, we observed adhesive failure at P3HT:PCBM/PEDOT:PSS interface, indicating the intrinsic material dependence of this mechanism. The impact of temperature, solar irradiation and humidity on the adhesion and cohesion properties of this particular interface is discussed. First, we have found that post-deposition annealing increases the adhesion significantly. Annealing changes the morphology in the photoactive layer and consequently alters the chemical properties at the interface. Second, solar irradiation on fully encapsulated solar cells has no damaging but in contrast an enhancing effect on the adhesion properties, due to the heat generated from IR radiation. Finally, the synergetic effect of stress and an environmental species like moisture greatly accelerates the decohesion rate in the weak hygroscopic PEDOT:PSS layer. This results in a loss of mechanical integrity and device performance. The insight into the mechanisms of delamination and decohesion yields general guidelines for the design of more reliable organic electronic devices. © 2012 IEEE.