Solar Radiation Monitoring Station

In 2006, RESU began a project to directly measure radiation energy from thesun, or insolation, from the roof of Humboldt State University’s library in Arcata, CA. These data are intended for use by residents, solar installers and engineers when designing photovoltaic systems, passive solar designs for new buildings, or planning gardens. Reliable measurements of local solar energy are useful for determining solar array sizing, battery storage requirements, andproject payback including carbon dioxide emission offsets.

Due to the highly localized weather in the coastal zones, also known as microclimate, it can be difficult to accurately model the available insolation in these regions. The Solar Radiation Monitoring Station (SoRMS) project is our solution to the need for measured solar radiation data on the North Coast.

The HSU library roof is equipped with two Eppley Precision Spectral Pyranometers. One measures global radiation, or total solar radiation, on a horizontal surface and the other measures diffuse radiation. Diffuse radiation is light reflected by the sky, the ground, or any other surface. A "shadowband" is positioned over the second pyranometer to block the direct light from the sun so that only diffuse radiation is measured. Subtracting the diffuse radiation from the global radiation gives the direct beam component of the total insolation. Direct beam radiation on a horizontal surface is reported in Watts per square meter (W/m2) and is the basis for solar calculations.

The data from the two pyranometers are logged using a Campbell Scientific CR510 data logger which is connected to the Internet by a NL-100 network link interface. The system is powered by two 15W solar panels connected to a charge controller and a small battery.   Data are automatically downloaded and posted to the NREL website on an hourly basis.

This project was made possible through the support of the HSU Sponsored Programs Foundation, the National Renewable Energy Laboratory, Redwood Alliance, Schatz Energy Research Center, HSU Environmental Resources Engineering department, HSU Plant Operations, Marty Reed - HSU Equipment Technician, and the HSU library staff.

More information about SoRMS is available on Appropedia.