Spoiler, it was.
* Dan and Denise make solar Fresnel Lenses, Parabolic Mirrors, and other intriguing things all towards their passion for alternative energy options.
** A fresnel lens is composite compact lens originally developed by French physicist Augustin-Jean Fresnel (1788–1827) for lighthouses. It has been called "the invention that saved a million ships."
The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet.