Solar irradiance maximum

The sun s total radiation output is approximately equivalent to that of a blackbody at 10,350°R (5750 K). However, its maximum intensity occurs at a wavelength that corresponds to a temperature of 11,070°R (6150 K) as given hy Wien s displacement law. A figure plotting solar irradiance versus spectral distribution of solar energy is given in Fig. 9. See also Solar Energy. 

This is the maximum amount of electric power that a PV module is able to generate when it receives 1,000 W/m2 of solar irradiation at 25°C. Recently, people in the industry started to refer to 1 kWp as 1 sun. ... 

Manufacturers provide operating characteristics of photovoltaic modules in standard conditions, which are defined by a solar irradiance value equal to 1000 W/m2 and a photovoltaic module temperature equal to 25°C. The most important of them is the maximum power that can be obtained at these conditions and is used for the determination of the photovoltaic module nominal power. However, in a considered site, solar irradiance changes during the day. In addition, depending on the environmental conditions, due to the internal thermal losses of the photovoltaic module, its temperature also varies. As a result, the maximum extracted power is usually lower than that provided by the manufacturers. 

The value of the global irradiation (Eq. 7.3) varies widely with the time of day, the time of year, the latitude, the altitude, and atmospheric conditions. As indicated previously, the maximum solar irradiation incident on the earth s atmosphere averages 1366 W m-2. Because of scattering and absorption of solar irradiation by atmospheric gases (see Fig. 4-5), S on a cloudless day with the sun directly overhead in a dust-free sky is about 1000 W m-2 at sea level. 

Besides the absorption of the various components of solar irradiation, additional infrared (IR), or thermal, radiation is also absorbed by a leaf (see Eq. 7.2 and Fig. 7-1). Any object with a temperature above 0 K ( absolute zero ) emits such thermal radiation, including a leaf s surroundings as well as the sky (see Fig. 6-11). The peak in the spectral distribution of thermal radiation can be described by Wien s displacement law, which states that the wavelength for maximum emission of energy, A,max, times the surface temperature of the emitting body, T, equals 2.90 x 106 nm K (Eq. 4.4b). Because the temperature of the surroundings is generally near 290 K, A,max for radiation from them is close to... 

Figure 5. Topumm and maximum achievable efficiencies for oxygen production step of the sulfur family solar TCWSCs as a function of the mean flux concentration ratio, Cr, at X= 520 nm and variation of Toptimm vs. X at constant Cr. Direct normal solar irradiance data from Figure (4), AM 1.5.

Maximum energy conversion efficiencies of (/ lax = 0.1086 have recently been measured and verified for dye-sensitized regenerative cells illuminated with air mass 1.5 simulated solar irradiation [27]. The efficiency of photoelectrosynthetic cells must also include contributions from the free energy stored in the chemical products of the reduction and oxidation reactions. 

Figure Jf.,10. Ratio between the solar irradiance at solar maximum and minimum activity conditions (11-year solar cycle) as a function of wavelength (10-400 nm), as estimated by Lean (1997).

Obtain empirical heat build up data for a number of material colors in worst case environments. The producer obtains a number of samples of different colors of his material and exposes them to the worst case environment in his intended market. This environment should have the highest solar irradiance and warmest temperatures the product may be subjected to while in service. The samples should be oriented for exposure resulting in the maximum heat build oriented normal to sun, protected from breezes and insulated from convective and conductive cooling as much as appropriate for the product. Consideration should also be given to reflective surfaces and other heat sources the product may encounter in the field. The producer then carefully measures the temperatures the selected samples reach under these worst... 

Fig. 7.2 Illustration of the spectroelectrochemical characterisation of a laboratory scale DSSC with a nanocrystalline Ti02 film sensitised with the RuN3 dye, measured under simulated AM 1.5G solar irradiation (100 mW cm ) electrolyte composition methoxyproprionitrile with 0.6 M propylmethylimidazolium iodide, 0.1 M Lil, 0.1 M tert butylpyridine, and 0.1 M iodine or guanidium thiocyanate 5 pm thick Ti02 film (9 nm particles) and scattering layer, a J-V curve, b IPCE spectrum (Courtesy of Patricia Jesus, Coimbra Chemistry Centre). In an optimised RuN3 DSSC the /sc reaches a value 20 mV and the maximum incident photon to current efficiency reaches 85 % [25]...

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