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Solar Energy
Published in Sergio C. Capareda, Introduction to Renewable Energy Conversions, 2019
As described in the previous section, solar radiation comes in two forms—diffuse and direct solar radiation. Instruments to measure the two are readily available nowadays. The most common is the solar pyranometer. A pyranometer is a device that measures total or global solar radiation or the solar radiation flux density in units of W/m2. It has a sensor that relates the amount of solar energy received from all directions, regardless of form. If one is interested in measuring direct solar radiation, a pyrheliometer is used. This device has a long tube that allows only the direct portion of the solar radiation to be measured. The device tracks the sun perpendicularly through any given time of day. The pyrheliometer is quite expensive to own. One may use two pyranometers, which are relatively cheaper, to measure both the direct and the diffuse portions of the solar radiation. With two pyranometers, one is provided with a shaded ring that blocks the direct solar radiation from hitting the sensor, while the other measures global or total solar radiation. The difference in readings between the two pyranometers is the direct solar radiation received in a given unit of time. PV devices respond very well to direct solar radiation and not to the diffuse solar radiation. Hence, direct radiation data are important for these types of devices. A photo of a simple pyranometer is shown in Figure 2.2.
Direct Normal Irradiance
Published in Frank Vignola, Joseph Michalsky, Thomas Stoffel, Solar and Infrared Radiation Measurements, 2019
Frank Vignola, Joseph Michalsky, Thomas Stoffel
The variable conditions pyrheliometer comparison (VCPC), which was the title and acronym attached to this study, revealed three levels of performance for the instruments in the comparison. This comparison ignores two outliers that performed so poorly that further discussion of them was not considered. One of these was a photodiode pyrheliometer that was not expected to perform well, and the other was a thermopile instrument that was available, but it is uncertain that it was used correctly because there was no instruction manual for operating this instrument. The best performers, as expected, were the ACRs with windows that transmitted all solar wavelengths. The ACRs with windows are called all-weather cavity radiometers. The estimated 95 percent confidence level uncertainty in the measurements made by cavity radiometers without a window is 0.45 percent. A 95 percent confidence level means that 95 percent of the time, the measurements will be made within the uncertainty level expressed. The 95 percent confidence level uncertainty will be referred to as 95 percent uncertainty throughout this book. Transferring the calibration to all-weather (windowed) cavities produced a total 95 percent uncertainty of only 0.5 percent or just slightly more than the uncertainty of the cavities without the window. Several thermopile pyrheliometers performed with a 95 percent uncertainty between 0.7 and 0.8 percent; these were designated to be in the second tier of performance. One manufacturer supplied four versions of the same pyrheliometer model that had 95 percent uncertainties between 1.0 and 1.7 percent. Surprisingly, the 95 percent uncertainties determined in this experiment are better than those claimed by their respective manufacturers.
Performance of inclined heliostat solar field with solar geometrical factors
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Rahul Bhattacharjee, Subhadeep Bhattacharjee
The high precision ground measured solar radiation data have been obtained through pyrheliometer (first-class) which is mounted on a two-axis solar tracker of solar radiation resource assessment station (SRRA) located at National Institute of Technology (NIT), Agartala (Latitude: 23.83° N, Longitude: 91.28° E). An astronomical algorithm is used to control the tracking and a global positioning system (GPS) receiver is also integrated with the system to ensure the clock synchronization precisely. The SRRA station is solar-powered by independent operation and solar sensors are traceable to the world radiometric reference (WRR). Figure 4 shows the DNI profile of the location at the solar extreme days for a particular year. Figure 4(a) shows the instantaneous DNI profile at a particular instant of time (i.e. 8 am, 9 am, etc.) for solar solstice and equinox days, and Figure 4(b) shows hourly average DNI profile throughout the solar solstice and equinox days.
A combined theoretical and experimental performance analysis of a grid-tied photovoltaic system in semi-arid climate : a case study in Ghardaia, Algeria
Published in International Journal of Green Energy, 2020
Layachi Zaghba, Messaouda Khennane, Amor Fezzani, Idriss Hadj Mahammed, Abdelhalim Borni
The meteorological data in this study have been recorded at the enerMENA meteorological instruments station installed in 2012 at the rooftop of the Renewable Energy Applied Research Unit (URAER), the enerMENA station shown in Figure 1, consists of many equipment’s radiometric and meteorological sensors. The Direct normal solar irradiation (DNI) measurements were recorded using a solar tracker (Solys-2 from Kipp & Zonen) with a CHP1 pyrheliometer. In addition, two well-calibrated CMP11 pyranometers (Kipp & Zonen) are mounted on the same solar tracker which measures for diffuse (DHI) and global horizontal irradiance (GHI). This region has semi-arid characteristics. (Gairaa and Bakelli 2013).
Comprehensive solar energy resource characterisation for an intricate Indian province
Published in International Journal of Ambient Energy, 2021
Subhadeep Bhattacharjee, Rahul Bhattacharjee
The total yearly insolation changes with latitude at different locations, season, time of the day and atmospheric conditions (Garg and Garg 1985). Any forecast of solar radiation is subject to an uncertainty due to the natural variability of this phenomenon. Not only the solar radiations are hard to predict, but there are also significant differences between databases (Ramachandra and Subramanian 1997). Complete and precise solar radiation data at a specific location is quite indispensable for solar energy-related activities and research. But the measurement of solar radiation is difficult compared to other meteorological variables. The measurement of solar radiation is mostly involved with systemic error due to sensors and their constructions. In the present work, ground-measured solar radiation data for the year 2016 has been obtained from solar radiation resource assessment station (SRRA) located at National Institute of Technology (NIT), Agartala. Figure 1 shows the various sensors for solar radiation measurement in SRRA station. In order to measure the solar radiation, SRRA consists of a 1.5 m tall tower which houses a two-axis solar tracker equipped with pyranometer (unshaded) (secondary standard), pyrenometer with shading disc (secondary standard) and pyrheliometer (first class) to quantify global horizontal irradiance (GHI), diffuse horizontal irradiance (DHI), and direct normal irradiance (DNI), respectively. An astronomical algorithm has been used for the tracking control which is also integrated with a global positioning system (GPS) receiver which gives it a very precise clock synchronisation. The SRRA station is totally solar powered for independent operation and solar sensors are traceable to the world radiometric reference (WRR).