Добірка наукової літератури з теми "Solar Photo-Voltaics"

This article discusses Artificial intelligence based Maximum Power Point Tracking (MPPT) for solar Photo-voltaics based system. MPPT is used to improve the efficiency as well as to raise the output through the photovoltaic system through continuous tracking of MPP. The work demands the use of fuzzy logic control technology; hence the PV-cell is interfaced with a DC step-up converter connected with a dc load. Boost converters convert the output of low voltage DC to output of high voltage DC. Following taken through the solar panel are thermal factor like temperature and isolation. The validation of the proposed controller is also discussed.

Abstract Antimony selenide (Sb2Se3) is a promising absorber material for thin-film photo- voltaics. However, certain areas of fundamental understanding of this material remain incomplete and this presents a barrier to further efficiency gains. In particular, recent studies have highlighted the role of majority carrier type and extrinsic doping in dras- tically changing the performance of high efficiency devices.1 Herein, Sn-doped Sb2Se3 bulk crystals are shown to exhibit p-type conductivity using Hall effect and hot-probe measurements. The measured conductivities are higher than those achieved through native defects alone, but with a carrier density (up to 7.4 × 1014 cm−3) several orders of magnitude smaller than the quantity of Sn included in the source material. Addition- ally, a combination of ultraviolet, X-ray and hard X-ray photoemission spectroscopies are employed to obtain a non-destructive depth profile of the valence band maximum, confirming p-type conductivity and indicating a majority carrier type inversion layer at the surface. Finally, these results are supported by density functional theory calcu- lations of the defect formation energies in Sn-doped Sb2Se3, showing a possible limit on the carrier concentration achievable with Sn as a dopant. This study sheds light on the effectiveness of Sn as a p-type dopant in Sb2Se3 and highlights avenues for further optimisation of doped Sb2Se3 for solar energy devices.

Luminescent solar concentrators (LSC's) are promising candidates for reducing the cost of solar power generation. Conventional LSC's are slab waveguides coated or doped with luminescence materials for absorption and guiding of light to the slab edges in order to convert optical energy into electricity via attached photovoltaic (PV) cells. Exploiting the advantages of optical fiber production, a fiber LSC (FLSC) is presented in this thesis, in which the waveguide is a polymeric optical fiber. A hybrid fiber structure is proposed for an efficient two-stage concentration of incident light, first into a small doped core using a cylindrical micro-lens that extends along the fiber, and second to the fiber ends by guiding the fluoresced light from the active dopants. Flexible sheets are assembled with fibers that can be bundled and attached to small-area PV cells. Small dimensions and directional guiding of the fibers allow for approximately one order of magnitude geometrical gain improvement over that of existing flat LSC's. In addition, the undesired limit of LSC size is eliminated in one direction. Modeling and optimization of an FLSC design is presented using polarization-ray tracing under realistic conditions with solar spectrum radiation and broad-band absorption and emission spectra of fluorescence materials with their inevitable self-absorption effect. Methods and results of fabrication and accurate optical characterization of such FLSC using two off-the-shelf organic dyes and a commercially available polymer, COP, are discussed in detail. Fiber preforms, fabricated under optimized conditions for low light transport loss, are thermally drawn into sub-millimeter-size fibers. Characterization of several samples with various concentrations of the two dyes shows an optical-to-optical conversion efficiency of 9.1% for a tandem combination of two 2.5-cm-long fibers with the efficiency gradually decreasing to 4.9% with increase in fiber length to 10 cm.
Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering

Grid reliability and power outages are key concerns today, due to the ever-increasing energy demand. Traditionally, Uninterruptible Power Supplies (UPS) with battery storage have been employed to contend with grid outages. For renewable power production, Solar-Photovoltaics (SPV) based Distributed Energy Resources (DERs) have been integrated with the grid using a power electronic Grid-Tied Inverter (GTI). A typical GTI by design, engages in power conversion only when the grid is present, and ceases operation during a power outage to avoid a local unintentional island formation. Thus, solar energy is left unutilized by the GTI during a power outage, where the UPS steps in, to power critical loads. Recently, hybrid-PV or dual-mode inverter systems, that combine the complementary functional properties of UPS and GTI, have been in the focus of research due to their ability of standalone system operation during an outage while accessing solar power. Such a hybrid approach, although meets the desired operational objectives, requires the design, sizing, and control of the entire system, that comprises of multiple power converters, battery-banks, and SPV, to be carried out in a unified manner. This work enhances the existing methods of solar energy access during a power outage, where the GTI is kept as an independent system from the UPS. A reconfigurable battery/grid tied inverter (RBGTI) scheme is proposed, that ties to the grid and functions as a regular DCAC GTI when grid is present. However, during a power outage, it reconnects to the batterybank of an existing UPS present in a facility, where it functions as a DC-DC converter to provide PV based energy support. However, such an operation of RBGTI requires several questions to be resolved in terms of hardware configuration, islanding behavior, battery management, and overall system control, which are addressed in this work. For the islanding behavior in grid-tied mode, a dynamic-phasor based GTI system model is proposed that captures the system dynamics accurately after unintentional islanding and allows systematic stability study based on eigenvalue analysis. In the battery-tied mode, a dynamic model of the PV fed battery charge-controller system is proposed which facilitates the systematic design of a maximum-power-point tracking (MPPT) controller and a load current tracking controller for the RBGTI, that achieves the effect of a virtual PV based batterybank in parallel with the physical UPS battery. A supervisory RBGTI control scheme is proposed that ensures stable system operation during dynamic conditions of load power and solar insolation changes while reducing discharge burden on the UPS battery. A discrete IGBT converter hardware platform is developed, where the proposed analytical models, controls and the RBGTI performance are verified on a 4.5 kW experimental setup