WIP: Exploring light bulb technologies to teach energy conservation, numerical integration, and consumer consciousness

In a freshman engineering course, one objective is to introduce multidisciplinary teams of engineering students to unifying engineering and science principles such as mass, momentum and energy balances; materials; thermodynamics, and electricity and magnetism using a consumer product or engineering process as a test bed. In several of the course sections, the test bed was a Net Zero Energy Building (NZEB). A NZEB is a building that, over the course of a year, produces as much energy as it consumes. One lab activity associated with this project was experimentally determining the most energy efficient of several types of light bulbs. Students measured the visible light output, power consumption, and surface temperature of four different bulb types (incandescent, halogen, compact fluorescent, and LED) and then determined the efficiency of the bulbs and considered the implications for a NZEB and their own home. In the lab, student teams measured illuminance as a function of angle for each bulb, converted that illuminance to a luminous flux using numerical integration, and then converted to radiant flux and power. Students then calculated the fraction of the power consumed by the bulb that was used to produce light. Students' results showed LED bulbs were the most efficient and incandescent bulbs were the least efficient. While this is, perhaps, an obvious finding, the addition of the bulb temperature measurement brought to life the First Law of Thermodynamics. In their reports students commented on the inverse relationship between efficiency and bulb temperature and related their results to NZEBs, indicating that LED bulbs would be preferable not only for their high energy efficiency, but for their low residual heat. This paper will describe the details of the laboratory set up and assignment, highlight the intellectual scaffolding that was provided to students, and present future assessment plans.