Solar radiation calculation

Fig. 4.2. Photon current densities per photon energy of AMO (dotted line) and AM 1.5 (solid, line) solar radiation, calculated from data in Fig. 4.1...

A large surface has a = 0.6 for long-wavelength radiation and a = 0.95 for solar radiation. Calculate the radiation equilibrium temperature of the surface if its back side is insulated and top side is exposed to a solar radiation flux of 950 W/m2 and an environment at 300 K with h = 12 W/m2 °C. 

From Equation (5), it is clear that the basic parameter that decides the light harvesting ability of the photocatalyst is its band gap. The ideal limiting efficiencies for conversion of solar radiation calculated by Equation (5) as a function of the band-gap wavelength for standard AM 1.5 solar irradiation in a single band-gap device are represented in Figure 9. 

At 25°C, pH 7.5, 1.5 ppm FAC, and 25 ppm cyanuric acid, the calculated HOCl concentration is only 0.01 ppm. Although the monochloroisocyanurate ion hydrolyzes to only a small extent, it serves as a reservoir of HOCl because of rapid hydrolysis. Indeed, this reaction is so fast that HClCy behaves like FAC in all wet methods of analysis. Furthermore, since HClCy absorbs uv only below 250 nm, which is filtered out of solar radiation by the earth s atmosphere, it is more resistant to decomposition than the photoactive C10 , which absorbs sunlight at 250—350 nm and represents the principal mode of chlorine loss in unstabilized pools (30). As Httie as 5 ppm of bromide ion prevents stabilization of FAC by cyanuric acid (23) (see also Cyanuric and ISOCYANURIC acids). 

In our sample calculations (Example 3 1.1) we have chosen the colour of the outdoors surface as light grey and taking the vveathering effect into account, have considered the coefficient of both absorption and emission as 0.65. The manufacturer, depending on the colour and site conditions, may choose a suitable coefficient. It is, however, advisable to be conservative when deciding the temperature rise due to solar radiation to be on the safe side. 

The outdoor part of the enclosure has to perform more onerous duties as it has to withstand weather conditions and also absorb solar radiation. It has also to dissipate the heat of the conductor in addition to its own. It is therefore possible that the surface area of enclosure so chosen may have to be increased, and this will be revealed during thermal calculations which are carried out to check its suitability. 

Solar radiation through windows has no time lag and must be estimated by finite elements (i.e. on an hour-to-hour basis), using calculated or published data for angles of incidence and taking into account the type of window glass (see Table 26.1). 

Calculate the beating due to solar radiation on the flat concrete roof of a building, 8 nr by 9 m. if the surface temperature of the roof is 330 K. What would be the effect of covering the roof with a highly reflecting surface such as polished aluminium ... 

If basic calculations such as those presented are to be conducted, it is important to collect enough weather parameters to calculate reference evapotranspiration ETf). An on-site weather station should be considered a basic requirement minimum sensor requirements to calculate a Penman equation would include solar radiation, wind speed, relative humidity or actual vapor pressure, and air temperature. An on-site rain gauge is essential but it is also a good idea to have a rain gauge on the weather station even if it is not directly on-site. The most accurate variations of the Penman equation calculate Tq on an hourly basis. However, Penman routines using daily summaries are typically satisfactory for the purpose of calculating soil-water recharge. 

Significant economies of computation are possible in systems that consist of a one-dimensional chain of identical reservoirs. Chapter 7 describes such a system in which there is just one dependent variable. An illustrative example is the climate system and the calculation of zonally averaged temperature as a function of latitude in an energy balance climate model. In such a model, the surface temperature depends on the balance among solar radiation absorbed, planetary radiation emitted to space, and the transport of energy between latitudes. I present routines that calculate the absorption and reflection of incident solar radiation and the emission of long-wave planetary radiation. I show how much of the computational work can be avoided in a system like this because each reservoir is coupled only to its adjacent reservoirs. I use the simulation to explore the sensitivity of seasonally varying temperatures to such aspects of the climate system as snow and ice cover, cloud cover, amount of carbon dioxide in the atmosphere, and land distribution. 

Figure 2, Plots of the efficiencies tje, rjY, rfp, and -qc as a function of the wavelength Xg corresponding to the band gap E. The distributions have been calculated for AM 1.2 solar radiation (taken from distribution T/S of Ref. 6). Curves, E, Y, P, and C are plots of -qEy my VPy rjc as defined in Equations 3,8,12, and 16, respectively. Tfc has been calculated for 0.6, 0.8, and 1.0 eV energy loss, respectively, as...

Curve P is quite general and rip represents a realistic maximum conversion efficiency for any device seeking to convert solar energy directly to electricity or stored chemical energy. Boss and Hsiao (3 ) have calculated curves E, Y and P for AM 0 solar radiation. 

One can thus estimate the total light intensity incident on a given volume of air in the troposphere due to direct solar radiation, scattering, and reflection. The light absorbed in that volume can then be calculated... 

Concentration profiles of H2, He, CH4, and NH3 at 150 K and with the < tldy diffusion coefficient K = 3 x I05 cm2 sec-1 have been calculated by Strobel (943) and are given in Fig. VIII—15. Because of the presence of CH4 ibove the layer of NH3, solar radiation of wavelengths only above about 1600 A is effective in photodissociating NHj. 

Davies. J. E. and Hay. J. E. (1980) Calculation of solar radiation incident on a horizontal surface, Ptoc. 1st Canadian Solar radiation Data Workshop. 

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