Draft:Solar thermal automobile
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The first and only solar thermal automobile created was built by Dr. Robert McElroy of American Solar Energy Corp in the late 1970s. With the help of a good friend, Rick Kubis, McElroy began by stripping down the insides of a 1977 Chevrolet Vega station wagon.
Biography
[edit]Dr. McElroy wrote up the initial patent application and sent it to the patent office at Crystal City, VA. Reviewers at the patent office suggested that the final preparation needed to be completed by a qualified patent attorney.Finding a patent practitioner | USPTO They also enquired about whether the thermal battery[1] could be patented as a fuel source due to its high energy density. This is where Dr. McElroy says he first got the idea to patent the battery as a fuel source.
After spending months in the DC area libraries, he finally gained a better understanding of what made solar power efficient and how it worked from an engineering perspective.
The creation of the Solar-Thermal Hybrid Automobile generated a great deal of publicity and media coverage.
While reviewing engineering tables on physical properties of heat and thermal transfer, Dr. McElroy’s attention was drawn to a particular type of wax. It had high specific heat, high specific gravity, and a very large temperature range so that it would remain fluid.
He decided that this would be the ideal material for a thermal battery. Many thermal batteries use molten salt.[2] The system he developed did not use salts to eliminate the corrosive effects. Instead, his thermal battery used the wax product to deal with corrosion.
The two men refitted the car with a 1915 Stanley Steamer engine.[3] They included a monotube flash boiler[4] and a 700-pound thermal battery.[5] The thermal battery, a unique heat sink and the key element in the design, contained a stable, high temperature heat storage material that could be charged or heated by a high temperature solar concentrator such as a parabolic reflector.[6] For the sake of convenience, a small oil burner was used in the design.
Water was pumped through the monotube boiler, which was submerged in the heat storage material. This produced the steam needed to run the engine.
The car had a range of about 35 miles at 55 miles per hour. The solar powered test car represented a basic straightforward propulsion concept; one with the potential to reduce petroleum fuel consumption considerably.
Capturing the energy collected by a high heat storage material in the thermal battery and the energy collected by a high heat solar concentrator such as a parabolic reflector for use in a mobile application was made possible by the heat storage material in the patented thermal battery.
A stable tar-like refinery byproduct trademarked as thermal liquid can be heated to around 1000°F without vaporizing it and without degradation.
In 1981 the Solar-Thermal Hybrid Automobile went on display at the 8th Energy Technology Conference and Exposition at the Sheraton Washington, D.C. Hotel.
The Energy Conference was the first public outing for the Solar-Thermal Hybrid Automobile. Its debut made the front page of the Business Section of the Washington Star.[7] As reported in the Washington Star on March 10, 1981:
“American Solar Energy Corporation of Arlington is displaying a small station wagon powered by a solar thermal fuel system. The automobile sports the inaugural license plate NOGAS.
Design News executives asked McElroy and Kubis to transport the car to Chicago for an appearance on the Phil Donahue Show,[8] which was a popular talk show in those days.
Due to the influence of Big Oil Companies[9] in that day and time, the idea did not readily catch on but today, many inventors and innovators are coming up with similar technology that has the potential to provide fuel to automobiles, trucks and airplanes without the use of fossil fuels.
An Explanation of Thermal Liquid
Capturing the energy collected by a high-heat solar concentrator, such as a parabolic reflector, for use in a mobile application, is made possible by the heat-storage material in the thermal battery. The stable, tar-like, refinery byproduct, trademarked Thermal Liquid, can be heated to upwards of 1000F without igniting, degrading or creating high pressure.
Characterized by high density and high specific heat, Thermal Liquid absorbs and stores a large number of BTUs in a relatively small volume, minimizing the storage container surface area, and thus minimizing area to be covered by insulation against heat loss, and increasing portability.
The Thermal Liquid composition in the Vega built in the late seventies had an auto ignition point of 620F (in oxygen). Today, certain modifiers will raise the auto ignition point to 1000F or more. The material freezes at about 200F.
Though Thermal Liquid performs satisfactorily and is readily available, synthetic lubricants could improve the heat-storage efficiency. Phase-change salts offer some of the properties desired but are considered too corrosive.
Ceramic-fiber insulation surrounded the tank, holding ambient heat loss to 60F per 24 hours, from a 600F charge. There was also a steam release valve at the rear of the insulated, foil wrapped thermal battery.
Today, Dr. McElroy[10] works as a consultant and expert witness for vehicle accident reconstruction. He is also considered an expert at interpreting truck and car Event Data Recorders.[11] Throughout his life, he has worked as an instructor on complex topics like product service training for General Motors[12] in Houston, TX even developing curriculum for GM training programs.
Dr. McElroy is a Triple Certified ASE Master Technician,[13] who has received numerous awards and commendations including the 1998 Distinguished Service Award for Education/Professional from the Traffic Safety Committee of the Palm Beaches. He is considered the Grandfather of Solar Thermal Energy.
References
[edit]- ^ "Thermal energy storage", Wikipedia, 2025-06-23, retrieved 2025-07-12
- ^ "Molten salt", Wikipedia, 2025-07-03, retrieved 2025-07-12
- ^ "The Stanley Steam Engine". www.stanleymotorcarriage.com. Retrieved 2025-07-12.
- ^ "Monotube steam generator", Wikipedia, 2024-03-02, retrieved 2025-07-12
- ^ Slanger, Dan (2025-02-03). "Clean Energy 101: Thermal Batteries". RMI. Retrieved 2025-07-12.
- ^ "Parabolic reflector", Wikipedia, 2024-10-07, retrieved 2025-07-12
- ^ "The Washington Star", Wikipedia, 2025-05-20, retrieved 2025-07-12
- ^ "The Phil Donahue Show", Wikipedia, 2025-06-14, retrieved 2025-07-12
- ^ "Big Oil", Wikipedia, 2025-07-12, retrieved 2025-07-12
- ^ "Dr. Robert McElroy – Speaker, Author, Expert Witness". Retrieved 2025-07-12.
- ^ "Event data recorder", Wikipedia, 2025-02-15, retrieved 2025-07-12
- ^ "Site Maintenance". www.gm.com. Retrieved 2025-07-12.
- ^ "Test Series". ASE. Archived from the original on 2025-06-29. Retrieved 2025-07-12.