A Physics-Based DNI Model Assessing All-Sky Circumsolar Radiation

Yu Xie; Manajit Sengupta; Yangang Liu; Hai Long; Qilong Min; Weijia Liu; Aron Habte

doi:10.1016/j.isci.2020.100893

A Physics-Based DNI Model Assessing All-Sky Circumsolar Radiation

iScience. 2020 Mar 27;23(3):100893. doi: 10.1016/j.isci.2020.100893. Epub 2020 Feb 8.

Authors

Yu Xie¹, Manajit Sengupta², Yangang Liu³, Hai Long⁴, Qilong Min⁵, Weijia Liu⁶, Aron Habte²

Affiliations

¹ Power Systems Engineering Center, National Renewable Energy Laboratory, Golden, CO 80401, USA. Electronic address: yu.xie@nrel.gov.
² Power Systems Engineering Center, National Renewable Energy Laboratory, Golden, CO 80401, USA.
³ Environmental and Climate Sciences Department, Brookhaven National Laboratory, 99 Rochester St., Upton, NY 11973, USA. Electronic address: lyg@bnl.gov.
⁴ Computational Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA.
⁵ Atmospheric Sciences Research Center, State University of New York, 251 Fuller Road, Albany, NY 12203, USA.
⁶ Environmental and Climate Sciences Department, Brookhaven National Laboratory, 99 Rochester St., Upton, NY 11973, USA; School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing, China.

Abstract

By investigating the long-term observations at Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP), we find that the routinely used Beer-Bouguer-Lambert law and the models that empirically separate direct normal irradiance (DNI) from measurements of global horizontal irradiance (GHI) have dramatic and unexpected bias in computing cloudy-sky DNI. This bias has led to tremendous uncertainty in estimating the electricity generation by solar energy conversion systems. To effectively reduce the bias, this study proposes a physical solution of all-sky DNI that computes solar radiation in the infinite-narrow beam along the sun direction and the scattered radiation falls within the circumsolar region. In sharp contrast with the other DNI models, this method uses a finite-surface integration algorithm that computes solar radiation in differential solid angles and efficiently infers its contribution to a surface perpendicular to the sun direction. The new model substantially reduces the uncertainty in DNI by a factor of 2-7.

Keywords: Energy Resources; Environmental Science; Radiation Measurement.