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Borate
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
The air mass quantifies the drop in the power of solar radiation when it passes through the atmosphere and is absorbed by air and dust. The AM is defined as AM=1cosθ where θ is the angle from the vertical (zenith angle). An easy method to determine the air mass is from the shadow of a vertical pole. AM is the length of the hypotenuse divided by the object height (h): AM=1+(sh)2
Solar Energy Resources
Published in Radian Belu, Fundamentals and Source Characteristics of Renewable Energy Systems, 2019
Solar intensity at the collector reduces with increasing air mass coefficient, in a nonlinear fashion due to the complex and variable atmospheric factors involved. For example, almost all high energy radiation is removed in the upper atmosphere (between AM0 and AM1) and so AM2 is not twice as bad as AM1. Furthermore, there is great variability in many of the factors contributing to atmospheric attenuation, such as water vapor, aerosols, smog, and the effects of temperature inversions. Depending on level of pollution in the air, overall attenuation can change by up to ±70% toward the horizon, greatly affecting performance particularly toward the horizon, where the effects of the lower layers of atmosphere are amplified by many folds. At AM = 1, after absorption has been accounted, the global radiation intensity is reduced from 1367 W/m2 at the top of the atmosphere to just 1000 W/m2 at sea level. Hence, for an AM = 1 path length, the sunlight intensity is reduced to 70% of its original AM = 0 value. Assuming that the absorption constant depends on the air mass, this observation can be expressed as: () I=1367⋅(0.7)AM
Radiometer Calibrations
Published in Frank Vignola, Joseph Michalsky, Thomas Stoffel, Solar and Infrared Radiation Measurements, 2019
Frank Vignola, Joseph Michalsky, Thomas Stoffel
Values of air mass (m) depend on the apparent solar position in the sky and is approximately equal to the secant of the solar zenith angle (e.g., m is 1.5 for a solar zenith angle of about 48.2°). The atmospheric optical depth varies with the wavelength of the incident radiation (e.g., at 550 nm, an aerosol optical depth (AOD) value of 0.01 represents an extremely clean and cloudless atmosphere and a value of 0.4 or more corresponds to very hazy conditions. Average monthly values of estimated AOD range from 0.1 to 0.15 for the USA and exceed 0.8 for parts of Africa and Asia based on satellite observations.10
Photovoltaic thermal solar air heater under external recycle: A performance study
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Ajay Kumar, Shubham Silswal, Prashant Dhiman
The effectiveness of the thermal is concerned by the thermal heat produced from the photovoltaic cell. The rise in air mass flow rate augments the heat transfer coefficient, improves the thermal gain of air per unit mass from the collector plate containing the PV cell, and provides higher thermal efficiency. The growth in thermal efficiency improves with a massive surge in the recycling ratio over the constant mass flow rate. However, the gain is more significant at a lower recycling ratio. The thermal efficiency rise by 39% compared to without recycling at a high mass flow rate, as shown in Figure 4(a). The electrical efficiency is entirely reliant on photoelectric cell temperature, as discussed in previous sections. Evidently, for different recycling ratios of a particular air mass flow rate, the PV cell’s temperature decreases and thus, simultaneously improving power efficiency. The temperature limitation of the photoelectric cell is the air inlet temperature. Because of this limitation, the heat transfer rate decrease due to a drop in temperature between the air inlet and the collector plate containing the photovoltaic cell. Therefore, with an increment in the recycling ratio (0.31.8), the gain in electrical efficiency is reduced. The electrical efficiency rise by 13% compared to without recycling along with a high mass flow rate, as demonstrated in Figure 4(b).
Blue skies and red sunsets: Reliability of performance parameters of various p-n junction photovoltaic module technologies
Published in Cogent Engineering, 2019
Edson L. Meyer, Ochuko K. Overen
Standard test conditions (STC: 1000 W/m2 irradiance, 25°C cell temperature and AM 1.5 global spectrum) were adopted for the purpose of comparing photovoltaic (PV) cells and modules under specific reference conditions. The irradiance represents peak sunlight and the 25°C cell temperature is representative of room temperature in most laboratories. The air mass (AM 1.5) is the ratio of the atmospheric mass in the actual observer-sun path to the mass that would exist if the observer were at sea level, at standard barometric pressure with the sun directly overhead. If, however, PV cells and modules are operating outdoors, meteorological conditions are usually far from STC. Under these outdoor conditions, STC module characteristics are no longer a reliable performance indicator. The three factors influencing module characteristics the most are temperature, irradiance and spectral changes. Knowledge of the influence of these factors on module performance is therefore essential, especially for system designers and consumers, to determine module suitability.
Experimental evaluation of the performance of latent heat storage unit integrated with solar air heater
Published in International Journal of Ambient Energy, 2022
Jatin Patel, Dhyey Shukla, Harshil Raval, Anurag Mudgal
Various instruments were utilised to measure different operating parameters of the system described. PT-100 type temperature sensors with accuracy ± 0.2°C and a pyranometer [Make: Hukseflux; Model: SR20-D1; Non – linearity: <1% (up to 1500 W/m2)] were connected to a data acquisition (Thermo Fisher – DT80) to log the temperature of air at different locations of the heating system and the solar radiation intensity, respectively. The air mass flow rate was measured using an orifice metre which was mounted at the inlet of solar air heater. An energy metre counted the total electrical unit consumed by the blower during the test period.