  The global transition towards cleaner and more sustainable energy production
is a major challenge. We present an innovative solution by utilizing smartphone
light sensors to measure direct normal solar irradiance, the primary component
of ground-level solar radiation. We provide comprehensive guidelines for
calibrating the sensor using two methods: a professional reference measurement
and clear-sky satellite estimates. The latter method is particularly
advantageous in resource-constrained environments. Once calibrated, the
smartphone becomes a valuable tool for measuring the solar resource. We propose
an instructional laboratory focusing on the physics of solar radiation and its
interaction with the Earth's atmosphere, exploring solar variations across
locations, cloud conditions, and time scales. By integrating irradiance values
measured throughout a day the daily irradiation can be estimated. This approach
enhances students' understanding of solar radiation attenuation and its
relationship with atmospheric interactions. This method offers a practical and
educational solution for promoting renewable energy knowledge and addressing
the challenges of the energy transition.
