On the Development of a Low Cost Pyrheliometer

A low cost pyrheliometer, based on a thermoelectric sensor, was developed at the Energy and Sustainability Center at the Florida State University. In addition, an inexpensive double-axis tracking device, capable of autonomous operation, enables the pyrheliometer to operate as a stand-alone system. Widely available off-the-shelf components were used and compromises in accuracy and time responsiveness were made in order to keep the cost low. The obtained data was compared with an Eppley Normal Incidence Pyrheliometer (NIP) using model ST-1 solar tracker. Steady state values of irradiance were measured with an accuracy better than $±2%$⁠. Transient measurements are time delayed by a thermal lag of about 2 min, which leads to a high error for instantaneous measured values. However, the integrated irradiance over the course of any given day yields irradiation values with accuracy better than $±2%$⁠, even on days when the sun and clouds quickly alternate. Based on a manufacturing cost analysis, the prototype pyrheliometer system is anticipated to cost an order of magnitude less than commercially available products if mass-produced.