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**Simple Solar Spectral Model for
Direct and Diffuse Irradiance
on Horizontal and Tilted Planes at the Earth's Surface for
Cloudless Atmospheres** |

Table of Contents
Preface

**SUMMARY**

**Objective**

To present a new, simple model for direct and diffuse spectral irradiance on
horizontal and tilted surfaces at the earth's surface for clear days.

**Discussion**

In a previous report (SERI/TR-215-1781), we described a simple model for
calculating direct normal and diffuse horizontal spectral irradiance for
clear days. In this report, we present a new, simple model that incorporates
improvements to the simple model approach and an algorithm for calculating
spectral irradiance on tilted surfaces. The goal is to provide researchers
with the capability to calculate spectral irradiance for different atmospheric
conditions and different collector configurations/orientations using
microcomputers.

**Conclusions**

A new, simple, spectral irradiance model has been formulated that produces
terrestrial spectra between 0.3 and 4.0 µm with a resolution of approximately
10 nm. Inputs to the model include the solar zenith angle, the collector tilt
angle, atmospheric turbidity, the amount of precipitable water vapor and ozone,
surface pressure, and ground albedo.

List of Figures
Table of Contents

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