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Fundamentals of Solar Radiation
Published in D. Yogi Goswami, Principles of Solar Engineering, 2023
Two basic types of instruments are used to measure solar radiation: pyranometer and pyrheliometer. A pyranometer has a hemispherical view of the surroundings and therefore is used to measure total, direct, and diffuse solar radiation on a surface. A pyrheliometer, on the other hand, has a restricted view (approximately 5°) and is, therefore, often used to measure the direct or beam solar radiation by pointing it toward the sun. Pyranometers are also used to measure the sky diffuse radiation by using a shadow band to block the direct sun view. A detailed discussion of the instrumentation and calibration standards is given by Iqbal (1983) and Zerlaut (1989). A more recent book on “Solar and Infra-Red Radiation Measurements” by Vignola et al. gives detailed information on solar radiation measurements (Vignola et. al. 2012).
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.
Thermal Radiation
Published in Abdul Al-Azzawi, Photonics, 2017
Solar radiation measurements often include total (beam and diffuse) radiation, in energy per unit time per unit area, on a horizontal surface. The measurements are made by a pyrheliometer using a collimated detector for measuring solar radiation for a small portion of the sky including the Sun (i.e., beam radiation) at normal incidence. Also the radiation measurements made by a pyran-ometer measure the total hemispherical solar (beam + diffuse) radiation, usually on a horizontal surface, as shown in Figure 3.6(a). If shaded from the beam radiation by a shade ring, it measures only the diffuse radiation, as shown in Figure 3.6(b). The primary meteorological measurements, done in virtually every weather network stations, are those of global solar radiation and of sunshine duration, using pyranometers. Pyranometers are radiometers designed for measuring the irradiance on a plane surface, normally from solar radiation and lamps, for measuring photosynthetically active radiation (PAR) in natural daylight or for measurement of illuminance, for the measurement of sunshine duration. There are many types of pyrgeometers designed to measure meteorological radiation parameters. Pyrgeometers are designed for IR (infrared) radiation measurement. Sunshine duration is defined by the World Metrological Organization (WMO) as when the solar radiation exceeds the level of 120 W/m2.
Thermal performance of the steam boiler based on Scheffler solar concentrator for domestic application: Experimental investigation
Published in Australian Journal of Mechanical Engineering, 2021
Vikrant Kamboj, Himanshu Agrawal, Anish Malan, Avadhesh Yadav
The different devices and instruments used in the experimental investigation are as follows: Pyranometer (model CM11 manufactured by Kipp and Zonen, Holland) is used to measure the solar intensity. The Pyranometer has an accuracy of about ±1% with regular calibration.Thermocouple RTD PT 100 integrated with digital temperature indicator having a least count of 0.1°C is used for measuring the ambient temperature, glazing temperature, surface temperature of steam boiler (receiver) and water/steam temperature. In this experimental analysis works an RTD PT 100 thermocouple in the range from 0ºC to 200ºC.The anemometer measures wind speed at the time of experimentation having an accuracy of ±0.1m/s.Pressure gauge of 2.1 bar is used to measure the steam pressure inside the steam boiler with an accuracy of ±1.6% of full span.
Heat transfer and fluid flow investigation in dimple roughened solar duct arranged in multiple arc pattern
Published in International Journal of Ambient Energy, 2022
Ahmad Kamal Hassan, M. Muzaffarul Hasan, Mohammad Emran Khan
An investigation is conducted to obtain experimental values of ‘Nur & fr’ in dimple shape arranged in arc pattern roughened collectors. The test rig was fabricated and calibrated properly before taking data for roughened and non-roughened ducts. The test rig had two ducts capable of accommodating roughened and non-roughened absorbers simultaneously. The various sets of data recorded from the test rig include air and plate temperatures at various locations, frictional penalties at duct, orifice and solar insolation. The test facility is developed as per ASHRAE standards (1977). Figures 1 and 2, respectively, shows schematic and actual photograph of the test rig. A 5 HP, 3.5 kW blower with an electric motor was provided to suck air from the atmosphere through the test sections. The rectangular duct is having dimensions of 2150 × 330 × 30 mm for which, test section being 1200 mm, entry and exit length being 650 and 300 mm marked. The entry section is made of bell-mouthed shape at the inlet side to avoid loses at entry. Each test section contains a glass cover of 4 mm thickness at the top and a backplate of 2 mm thick G.I sheet at the bottom. Calibrated orifice is installed to find flow rate through roughened ducts. A copper constantan thermocouple is provided at various locations to measure plate temperatures. A digital pyranometer system is used to measure solar radiation, wind velocity, ambient temperatures. Figure 3 depicts a schematic diagram of multiple arc dimple roughened absorber used under the present study. Figure 4 shows a schematic diagram of roughened and non-roughened ducts. Figure 5 shows thermocouple’s positions.
Performance analysis of a solar parabolic trough collector fitted with a helical coiled tube absorber
Published in International Journal of Ambient Energy, 2023
K. Syed Jafar, R. Venkatesaperumal, N. Beemkumar, M. Santhoshkumar, T. V. Rajamurugan
A small powered pump helps to maintain the flux through the spiral tubes. Various temperatures, including water and absorber, are measured with the help of chromel ± alumel thermal pairs connected to digital micro-volts. The pyranometer measures solar radiation intensity.