Application of Solar Energy in Production and Life in Ho Chi Minh City

Solar energy is one of the largest energy sources that people can take advantage of as it is a clean, almost endless source of energy and easily applied in many places. This energy source is used more and more to replace traditional energy sources that are gradually becoming scarce and exhausted, and also contribute to saving energy and reducing emissions to the environment. Therefore, it is necessary to develop renewable energy sources to meet the electricity demand for economic activities, people's living activities as well as ensure environmental safety in the context of global warming. This article will present research results on the application of solar power in life and production in Ho Chi Minh City. The equipment system includes a mirror to concentrate solar radiation, the great potential and deployment direction of solar power application in the future urban model of Ho Chi Minh City as well as other provinces in Vietnam.

Optical Analysis of a Window for Solar Receivers Using the Monte Carlo Ray Trace Method

Concentrated solar power (CSP) systems use heliostats to concentrate solar radiation in order to produce heat, which drives a turbine to generate electricity. We, the Combustion and Solar Energy Laboratory at San Diego State University, are developing a new type of receiver for power tower CSP plants based on volumetric absorption by a gas-particle suspension. The radiation enters the pressurized receiver through a window, which must sustain the thermal loads from the concentrated solar flux and infrared reradiation from inside the receiver. The window is curved in a dome shape to withstand the pressure within the receiver and help minimize the stresses caused by thermal loading. It is highly important to estimate how much radiation goes through the window into the receiver and the spatial and directional distribution of the radiation. These factors play an important role in the efficiency of the receiver as well as window survivability. Concentrated solar flux was calculated with a computer code called MIRVAL from Sandia National Laboratory which uses the Monte Carlo Ray Trace (MCRT) method. The computer code is capable of taking the day of the year and time of day into account, which causes a variation in the flux. Knowing the concentrated solar flux, it is possible to calculate the solar radiation through the window and the thermal loading on the window from the short wavelength solar radiation. The MIRVAL code as originally written did not account for spectral variations, but we have added that capability. Optical properties of the window such as the transmissivity, absorptivity, and reflectivity need to be known in order to trace the rays at the window. A separate computer code was developed to calculate the optical properties depending on the incident angle and the wavelength of the incident radiation by using data for the absorptive index and index of refraction for the window (quartz) from other studies and vendor information. This method accounts for regions where the window is partially transparent and internal absorption can occur. A third code was developed using the MCRT method and coupled with both codes mentioned above to calculate the thermal load on the window and the solar radiation that enters the receiver. Thermal load was calculated from energy absorbed at various points throughout the window. In our study, window shapes from flat to concave hemispherical, as well as a novel concave ellipsoidal window are considered, including the effect of day of the year and time of the day.

Exergy, Energy, and Dynamic Parameter Analysis of Indigenously Developed Low-Concentration Photovoltaic System

Piecewise linear parabolic trough collector (PLPTC) is designed and developed to concentrate solar radiation on monocrystalline silicon based photovoltaic module. A theoretical model is used to perform electrical energy and exergy analysis of low-concentration photovoltaic (LCPV) system working under actual test conditions (ATC). The exergy efficiency of LCPV system is in the range from 5.1% to 4.82% with increasing rate of input exergy rate from 30.81 W to 96.12 W, when concentration ratio changes from 1.85 to 5.17 Sun. Short-circuit current shows increasing trend with increasing input exergy rate of≈0.011 A/W. Power conversion efficiency decreases from 7.07 to 5.66%, and open-circuit voltage decreases from 9.86 to 8.24 V with temperature coefficient of voltage≈-0.021 V/K under ATC. The results confirm that the commercially available silicon solar PV module performs satisfactorily under low concentration.

A Novel Lens-Walled Compound Parabolic Concentrator for Photovoltaic Applications

A compound parabolic concentrator (CPC) is a nonimaging concentrator that can concentrate solar radiation coming within its acceptance angle. A low concentration CPC photovoltaic system has the advantages of reduced Photovoltaics (PVs) cell size, increased efficiency and stationary operation. The acceptance angle of a CPC is associated with its geometrical concentration ratio, by which the size of PV cell could be reduced. Truncation is a way to increase the actual acceptance angle of a mirror CPC, but it also reduces the geometrical concentration ratio. On the other hand, a solid dielectric CPC can have a much larger acceptance angle, but it has a larger weight. To overcome these drawbacks, this study presents a novel lens-walled CPC that has a thin lens attached to the inside of a common mirror CPC or has the lens to be mirror coated on its outside surface. The shape of the lens is formed by rotating the parabolic curves of a CPC by a small degree internally around the top end points of the curves. The refraction of the lens allows the lens-walled CPC to concentrate light from wider incidence angle. The commercial optical analysis software PHOTOPIA is used to verify the principle of the presented lens-walled CPC and examine its optical performance against the common CPCs. As an example, the simulation is aimed to evaluate whether a lens-walled CPC with a geometrical concentration ratio of 4 has any advantage over a common CPC with a geometrical concentration ratio of 2.5 in terms of actual acceptance angle, optical efficiency and optical concentration ratio.

Response of Monocot and Dicot Weed Species to Fresnel Lens Concentrated Solar Radiation

Fresnel lenses are used to concentrate solar radiation to a line or point. A linear Fresnel lens (0.91 by 1.52 m, 0.74-m focal length, 0.01- by 1.52-m line focus) was investigated as a method for weed control. Field experiments were conducted to assess the effect of Fresnel lens concentrated solar radiation at various exposure times, stages of plant growth, and soil surface moisture conditions. On a dry soil surface exposure times of 1 to 10 s at 290 C resulted in control of redroot pigweed from 100% for a 1-s exposure at the cotyledon stage to 89% for a 10-s exposure at the 10-leaf stage. Redroot pigweed and kochia control was similar at exposures of 3 to 10 s, but less for kochia at 1 and 2 s. Green foxtail control was less than that of kochia and redroot pigweed. Control was reduced on a moist compared to a dry soil surface. Concentrated solar radiation holds the greatest potential for control of small dicot weeds on a dry soil surface.