Reflected Radiation Onto a Collector. Continue Examples 7.9 and 7.10 and find the reflected radiation on the panel if the reflectance of the surfaces in front of the panel is 0.2. Recall that it is solar noon in Atlanta on May 21, the altitude angle of the sun β is 76.4º, the collector faces 20º

Question

Reflected Radiation Onto a Collector. Continue Examples 7.9 and 7.10 and find the reflected radiation on the panel if the reflectance of the surfaces in front of the panel is 0.2. Recall that it is solar noon in Atlanta on May 21, the altitude angle of the sun β is 76.4º, the collector faces 20º toward the southeast and is tipped up at a 52º angle, the diffuse sky factor C is 0.121, and the clear-sky beam insolation is 902 W/m².

Accepted Answer

From (7.31), the clear-sky reflected insolation on the collector is

[latex]\begin{matrix} I_{RC} & = \ ho I_{B}\left(\sin \ \beta \ + \ C ight) \ \left(\frac{1 \ - \ \cos \ \Sigma}{2} ight) \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \ & = \ 0.2 \ \cdot \ 902 \ {W}/{m^{2}} \ \left(\sin \ 76.4º \ + \ 0.121 ight) \ \left(\frac{1 \ - \ \cos \ 52º}{2} ight) \ = \ 38 \ {W}/{m^{2}} \end{matrix}[/latex]

The total insolation on the collector is therefore

[latex]I_{C} \ = \ I_{BC} \ + \ I_{DC} \ + \ I_{RC} \ = \ 697 \ + \ 88 \ + \ 38 \ = \ 823 \ {W}/{m^{2}}[/latex]

Of that total, 84.7% is direct beam, 10.7% is diffuse, and 4.6% is reflected. The reflected portion is clearly modest and is often ignored.

Question 7.11: Reflected Radiation Onto a Collector. Continue Examples 7.9 ......

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