Hydrogen, reacting with oxygen, is a very energetic, non-polluting fuel. Can it be used as a fuel for gas turbines? Two successful and significant examples of its use are reviewed. Surplus renewable electrical energy from solar and wind could be used for electrolysis of water to produce hydrogen to power gas turbine power plants. Serving as a means of energy storage, the hydrogen could be kept in caverns. It could also be added directly to natural gas pipeline systems serving gas turbine power plants, thus reducing greenhouse gas production.
#37 MARCH 2019
“The Role of Gas Turbines in Global Energy Conversion” is the title of a talk I have given to audiences in universities, companies and energy meetings. During recent talks, in the question-and-answer period, I have been asked, can gas turbines run on hydrogen as a fuel, instead of the usual jet fuel, fuel oil or natural gas?
Why hydrogen? As author Peter Hoffman points out in The Forever Fuel: The Story of Hydrogen , hydrogen, a normally invisible, tasteless colorless gas, is the most abundant element in the universe. As a fuel it is very energetic and non-polluting, reacting with oxygen to yield H2O.
For engines, hydrogen is the best of everything . It has low weight and the highest specific heat value of any fuel—about three times greater than jet fuel. However, it is an energy carrier that must be manufactured (like electricity), for instance by electrolysis of water or by steam reforming of natural gas. Recently these properties are being considered to have hydrogen be used as an energy storage fuel for use in gas turbine electrical power generation. More on this later!
Can hydrogen be used to power a gas turbine? A straight forward way to answer this is to retell some early history of the gas turbine in its role as an aircraft jet engine.
The first jet engine powered flight took place on Sunday, August 27, 1939 at the Heinkel aircraft factory airfield along the Baltic coastline, near Rostock, Germany. It was achieved in the Heinkel He 178 single engine aircraft, powered by inventor Dr. Hans von Ohain’s He S 3B jet engine, fueled by gasoline.
The He S 3B, with a thrust of 989 pounds (lbt), had been developed from a hydrogen-fueled project jet engine, designated He S1, He S for Heinkel Strahltriebwerk (Heinkel jet engine). This antecedent 250 lbt, 10,000 rpm jet engine was first run in March of 1937, in ground tests, and was described by then 28 year-old von Ohain  as follows:
“I turned the ignition on and carefully opened the hydrogen valve. The onset of ignition was audible. It sounded like the ignition of a gas water heater. The engine ran under its own power and accelerated easily. At the higher rotating speeds, it began to produce the sound typical of all later jet engines.”
In this 1937 very first German jet engine, von Ohain used hydrogen because of its high flame speed, wide combustion limits and gaseous state (droplet combustion challenges posed by liquid gasoline would be solved later for the H S 3B). Von Ohain explains further:
“We used a whole battery of hydrogen in bottles and we ran the turbojet from two to five minutes until the hydrogen was exhausted. It was in an order of magnitude of minutes. I had no combustion problems with hydrogen but the metal burnout was quite a problem.”
The von Ohain early operation of the first jet engine shows that gas turbine operation on pure hydrogen gas is easily attainable. Some twenty years later, engineers at Pratt & Whitney Aircraft developed a jet engine with afterburner that operated on liquid hydrogen, stored cryogenically at atmospheric pressure and at about - 420°F. This work started in 1956, termed the “304 Suntan Project”, resulted in a 4,700 lbf  jet engine that was to power the proposed Kelly Johnson, Lockheed Skunk Works Mach 2.5, CL-400 reconnaissance aircraft.
Dick Mulready’s account  of the hydrogen-fueled 304 engine is a fascinating story. The early testing and subsequent production of five 304 engines took place in East Hartford, Connecticut, from 1956 to about 1959. Extensive testing was then carried out at the company’s new Florida Research and Development Center, located inland west of West Palm Beach in 7000 acres of swamp land. The area of the 304 test stand had the colorful name of the Loxahatchee slough. A 304 engine test run was dubbed the “Swamp Monster”, characterized by a low frequency howl that would increase in pitch with throttle advance until it became inaudible at full thrust . Test results showed the turbine inlet temperature profile was flat, giving a profile superior to existing hydrocarbon fueled engines.
The Suntan 304 engine was a success, but the proposed CL-400 aircraft was a bust. As Jack Connors  relates, the airplane would be a flying thermos bottle to cryogenically contain the liquid hydrogen fuel, giving it little flying range. Instead, Lockheed and P&WA set off on a different path to develop what became the Blackbird SR-71, with its JP-7 jet fueled J58 turbojet/ramjet engine. Aircraft range could be achieved by packing the hydrocarbon fuel in every available volume in wings and fuselage—not achievable with liquid hydrogen.
Energy Storage With Hydrogen
So, why is there a current interest in hydrogen-fueled gas turbines? It has to do with the increased use of renewable energy, i.e. the electric power produced by wind turbines and solar devices. When the wind blows and the sun shines, electricity is produced, but what happens when customer demand falls short of its supply? The surplus renewable energy could be stored for future use, but how?
Turner , among others, has advocated that surplus renewable energy from solar and wind could be used for electrolysis of water to produce hydrogen (and of course, oxygen). Just to get an estimate on how much water, he points out that 100 billion gallons of water/year could supply hydrogen to power the U.S. light-duty fleet of some 250 million vehicles, if all were fuel cell equipped. By comparison the U.S. uses about 300 billion gallons of water/year for gasoline production alone, three times that conjectured for hydrogen generation.
Hydrogen so produced could be stored in underground caverns (natural or man-made salt caverns) to be used as fuel in many existing gas turbine power plants (or directly in the rarer fuel-cell power plants).
Currently, there is considerable research going on (especially in Europe and Japan) to inject the hydrogen produced from electrolysis directly into existing natural gas networks (pipelines, storage tanks, etc.) that already feed gas turbine power plants. This would use the surplus renewable energy to directly reduce carbon dioxide power plant production.
Questions about combustion problems arising from the addition of hydrogen to the natural gas that might increase production of nitrous oxides need to be addressed. Current results indicate that up to 5-8% of hydrogen in gas turbine natural gas fuel will not be a problem for NOx production. In Japan, Mitsubishi  has successfully fired a 30% hydrogen natural gas fuel mix in a gas turbine.
The ideal economic model for energy storage is “buy low, sell high”. Cheap stored hydrogen fuel for use in gas turbine power plants should fit that economic model!