A hybrid flyback LED driver with utility grid and renewable energy interface
In renewable energy sources, the objective is maximum extraction and utilization of the available power. In this paper a hybrid flyback converter with multi ports-an AC Grid, a PV and a DC LED ports — is proposed to be used as an LED driver. The converter has the capability to achieve two objectives: first to maintain a continuous supply to the LED lighting system either from the Photovoltaic (PV) panel or the grid, and second to achieve maximum utilization of the solar PV panel by tracking the maximum power point and exporting surplus power to the grid, or getting the power deficit from the grid. The topology of the converter, operating principle, modes of operation and control structure are presented in this work. The concept of the hybrid flyback converter is verified using Matlab Simulink®. An experimental prototype is developed and tested for a 120-watt system, with 35 VDC solar panels, 120 Vrms 60 Hz grid and 24 VDC LED lights.
Energy-Saving Systems Using Photovoltaic Modules
The chapter presents the results of the development of two systems. The first is a photovoltaic system parallel to the power supply network of LED lamps. The algorithms of the system operation for both working and emergency lighting are shown. The basic operating modes of the system are considered taking into account the criterion of the minimum cost of electricity generated. These modes provide the most complete use of solar energy in the working day with minimal additional costs, allowing the consumer to save on electricity and increase the reliability of the emergency lighting system. The second system is a solar photovoltaic module built into a standard double-glazed window sash size 730x700 (mm), which is designed to charge a block of lithium-ion batteries with a capacity of 6.8 Ah with an output voltage of 5.25 V, the energy of which can be used to power any device having a USB 2.0 connector. The results of calculation of the required peak photovoltaic power of the module are presented; the technology of its sealing is described. Energy-Saving Systems Using Photovoltaic Modules
Turbulent boundary layer wall‐pressure fluctuations downstream from an abrupt change in surface roughness
Spectra of wall‐pressure fluctuations beneath a turbulent boundary layer have been investigated immediately downstream from an abrupt change in surface roughness, from slightly rough to very rough. Over the measurable frequency band (400 Hz to 7 kHz), the spectra in the first 150 mm scale on wall variables. This indicates that the motions responsible for the pressure fluctuations measured in this region are very close to the wall. Farther downstream this scaling procedure breaks down. It is suggested that the initially thin internal layer behaves independently of the flow external to it until it has grown appreciably and only then interacts with the outer boundary layer. It was found that, for all frequencies measured, the dimensional spectral level decreases initially then rises to a maximum at 250 mm from the roughness change before decreasing once more. The position of the maximum is close to where the internal layer ceases to have a distinct edge.