Leonard L. Northrup Jr.

The early success of these concentrating collectors was due in part to grants from the Department of Energy and its predecessor the Energy Research and Development Administration. They created a good deal of publicity for Northrup, Inc., including the cover of Popular Science Magazine and an article in Fortune Magazine that noted, "By squeezing (sic) sunshine optically, Lynn Northrup's unique new rooftop solar collector produces higher temperatures than are obtainable from most solar heating systems now on the market". Technically, these concentrating collectors were among the first commercially successful “east-west” tracking solar collectors. The fundamentals of their systems are still in use in daily azimuth and elevation tracking parabolic collectors. Most linear concentrating collectors are, as of this writing in 2010, of the less costly and less complicated seasonal tracking variety in the form of parabolic troughs.

Northrup's May 2006 patent describes a method with the potential for using water as a general refrigerant, as well as an economical method of desalinating water.

Emboldened with his success in concentrating collectors, Northrup turned his attention to achieving higher temperatures, with azimuth and elevation tracking mirrors "heliostats" focused on a central boiler – ie. solar thermal power towers. The most advanced power tower at the time was an experimental tower in France, the Solar furnace at Odeillo, in the Pyrenees Orientales, which like other power towers, had been used solely for scientific purposes. Northrup attended a conference there in 1973 along with Professor Yellott and Floyd Blake, a former Martin Marietta senior aerospace engineer who had become interested in solar thermal research.

During the mid-1970s, Northrup became interested in boosting the efficiency of air conditioning systems, and began looking at novel approaches, including water-source geothermal heat pumps, and the innovative use of scroll compressors in split system central air conditioning systems to achieve a higher efficiency rating, which have since become the standard compressor for high-efficiency residential air conditioning equipment.

In the early 1970s, before the Arab Oil Embargo and the spike in oil prices, Northrup became interested in the commercialization of solar thermal systems, particularly for heating potable water and swimming pools. Such systems had already been commercialized in other countries where climatic conditions were favorable, energy costs were high, and there was a tradition of scientific innovation notably solar power in Israel. Work in the United States had been limited to academia and a few companies in Arizona, Texas, and California. Northrup began experimenting with solar collectors to heat air, using finned heat exchangers, and engaged solar pioneer Professor John Yellott as a consultant on the absorptivity and emissivity or various surfaces and configurations, and on the transparency of various glasses and glazing material that exhibit the "greenhouse effect" - transparent to incoming solar radiation, but opaque to the re-radiation of infrared from the heated surface - hence a thermal trap or collector that exhibits the "greenhouse effect".

By the late 1970s, just five years after testing the first low temperature solar thermal collectors, Northrup Energy had become the preeminent developer of solar thermal technology. This attracted the attention of investors, and suitors, including the Atlantic Richfield Company, “ARCO”. ARCO's Chairman, Robert O Anderson was personally interested in solar technology and visited the Northrup Energy facility. Northrup, Inc. merged with Atlantic Richfield, and ARCO Ventures changed its name to ARCO Solar. The Northrup Energy team under Floyd Blake and Jerry Anderson went on to design and build some of the first commercial solar power tower installations, notably "Solar One" near Barstow, California. The heat from another project was used to generate steam for tertiary oil recovery in Kern County, California and for electric power generation. Some heliostats were built to directly track the sun with arrays of photovoltaic cells to generate power for the utility grid, near Hesperia, California. The seven million watt installation near Barstow was later dismantled and shipped to Europe's first commercial solar thermal power station. This unit was the largest solar electric power generation facility in the world. Northrup and Blake were then featured in a documentary on solar energy, Harnessing the Sun, narrated by actress Joan Hackett.

In the late 1960s, Northrup bought a controlling interest in Donmark Corporation, a manufacturer of residential air conditioning and heating equipment from Curtis Mathes, his lifelong friend. Northrup promoted the use of “all electric” central heating and cooling equipment, building a manufacturing facility in Dallas and later in Hutchins, Texas and selling primarily to apartment developers. In designing these systems, Northrup focused on the total installed cost of the unit, including the framing and plumbing costs.

After the War, Northrup went to work for Storm Vulcan, a Dallas company, where he invented a machine to clean aircraft engines. He also embarked on a venture to fit cars with air conditioning equipment, putting the machinery in the trunk and piping the cooled air through tubes in the headliner. This caught the interest of engineers from General Motors, who copied the system in Cadillacs in the late 1940s. "After market" automotive AC units were manufactured in Texas until the 1980s. He also sold some of the first air conditioning units, built by the Curtis Mathes Corporation, an early leader in manufacturing window units. Northrup married Jane Keliher and started a family in Dallas, where he designed and built one of the first single-family houses in the United States with central air conditioning. He founded a company to install air conditioning in residential and commercial buildings. With a Marketing Plan from G F Sweetman (CEO of American Awards Co), he became one of largest suppliers of Curtis Mathes fans and compressors in the nation. He also developed a company to manage, install, update, and clean air filtration systems.

Leonard "Lynn" L. Northrup Jr. (March 18, 1918 – March 24, 2016) was an American engineer who was a pioneer of the commercialization of solar thermal energy. Influenced by the work of John Yellott, Maria Telkes, and Harry Tabor, Northrup's company designed, patented, developed and manufactured some of the first commercial solar water heaters, solar concentrators, solar-powered air conditioning systems, solar power towers and photovoltaic thermal hybrid systems in the United States. The company he founded became part of ARCO Solar, which in turn became BP Solar, which became the largest solar energy company in the world. Northrup was a prolific inventor with 14 US patents.