John I. Yellott

John Ingle Yellott (October 25, 1908 – December 30, 1986) was a mechanical engineer who spent the first half of his career on coal, gas-turbine, and wartime research before switching to solar energy in 1955 at age 47, later becoming one of the founding figures of American passive solar engineering at Arizona State University.

Before solar

M.E. (1931) and M.M.E. with distinction (1933) from Johns Hopkins. Chaired Mechanical Engineering at Illinois Institute of Technology (1940–1943) and directed IIT’s Institute of Gas Technology (1943–1945). During WWII he consulted to the Metallurgical Laboratory at the University of Chicago — the Manhattan Project. From 1945–1955 he directed research for the Locomotive Development Committee of Bituminous Coal Research Inc., developing a coal-fired gas-turbine locomotive with pulverized-coal injection; he held more than 50 patents from this period.

The switch to solar (1955)

Yellott later described the reasoning: “the realization that the entire world, and the United States in particular, was running out of fluid fuels, and that we must find a way to gain economic access to the limitless energy of the sun.” He had moved to Arizona in 1951, helped found the Association for Applied Solar Energy in Phoenix (1954), and founded the Yellott Solar Energy Laboratory in Phoenix (1958).

Skytherm and the Hay collaboration

Yellott’s belief in Harold Hay‘s roof-pond concept gave Hay the opportunity to build the full-scale 1967 Phoenix prototype in the Sonoran Desert — Yellott donated the property, instrumentation, and thermal-comfort engineering expertise that made the first Skytherm test structure possible. Testing surfaced practical issues (mosquito larvae, nesting birds), later addressed with chemical treatment.

Arizona State University

Joined ASU’s College of Architecture (sources place this as early as 1963 in a lecturer role, with a more prominent turn after the 1973 oil crisis when he headed ASU’s solar program); named visiting professor 1973, emeritus 1979; received an honorary doctorate from ASU in 1985. Co-founded ASU’s Master of Science in the Built Environment program.

Other contributions

First chairman of the ASME Solar Energy Applications Group (later its Solar Energy Division). Developed the solar heat gain factor (SHGF) method for glass, now an ASHRAE standard; consulted for Corning, PPG, Libbey-Owens-Ford, and Pilkington. Organized the 1957 “Living with the Sun” competition. Invented a transparent solar pool cover still in commercial use. The “Yellott Number,” used to characterize thermosiphon solar water heaters, is named for him.

Publications: Energy for Our Future (1957); Solar Energy Utilization in North America (1958); Solar Radiation and the Atmosphere (1976); The Fundamentals of Solar Technology (1979); hundreds of articles and papers. His papers are archived at the American Heritage Center, University of Wyoming.

Honors: Member, Order of the British Empire (civil division); inaugural inductee, Solar Hall of Fame (1976); Fellow of ASME, ASHRAE, AAAS, and the Arizona Academy of Science; Benjamin Franklin Fellow, Royal Society of Arts (London). ASME’s biennial “John I. Yellott Award” and ASES’s “John and Barbara Yellott Award for Graduate Solar Research” are both named for him and his wife.

Uncertain

No independent newspaper obituary has been located; family and death details rest on Wikipedia’s unsourced account. The exact year he joined ASU is framed differently across sources (1963 vs. 1973) and hasn’t been reconciled against a single primary ASU record.