The intensity of the incident sunlight is monitored with a broadband optical power meter. Measuring the optical power of a broad-spectrum source like the Sun is most easily accomplished with a spectrally flat thermal sensor such as the Thorlabs S302C (approximately $1100 with the PM100USB interface). However, illuminance measurements (in lux) with a photo-diode-based light level sensor (such as the $60 PASCO PS-2177A) can be converted to irradiance (in W/m2) if the incident and response spectra are known.2 Alternatively, a number of relatively simple thermal experiments for measuring the solar constant have been described.3,4 As a possible extension, we show that a thermal camera (we use a FLIR T300) can be employed to image the temperature of the individual cells under various operating conditions.