Project-based learning has been shown to be an effective pedagogical strategy that motivates students and thus promotes learning. In this article we describe a project-based unit centered on the physics of solar cookers (Fig. 1 and 3). Our goal was to elevate the solar cooker from a summer camp activity to a college-level project that could be used to teach thermodynamics in a more engaging way. Solar cookers are used by people in developing countries as an alternative to wood fires and dangerous kerosene stoves, which motivates students to study the thermodynamics of solar cookers. In this unit, students engage in the engineering design process by designing, building, and testing a solar cooker. To do this, the students learn about the physics necessary to understand how the solar cookers absorb and lose energy, including heat transfer mechanisms, blackbody radiation, reflection, and the greenhouse effect. © 2018 American Association of Physics Teachers.