Understanding Fuel Cells and Power Systems

A thorough review of fuel cell technology covering different types with an in depth analysis of Alkaline Fuel Cells like those used in the Apollo and Space Shuttle systems. A full evaluation of spacecraft power system generation, storage and distribution with components explained and an emphasis on understanding power system schematics.
Fuel cells are a unique and historic power storage system. The first fuel cells were developed for the Apollo missions. You will notice that while modern spacecraft have solar panels the Apollo spacecraft did not. This is because they invented a new type of power storage system for the Command Module, which had to operate continuously after launch without recharging for about a week. The Lunar Excursion Module or LEM had regular batteries as it would only be used for going down to the Moon from Low Lunar Orbit and coming back up. It only had to operate for up to 75 hours. This was the longest time spent on the Moon accomplished by Apollo 17 with Eugene Cernan and Harrison Schmidt. The Command Module from the same mission spent six days in orbit with Ronald Evans in command. The journey there and back took three days each way. The launched-on December 7, 1942 and landed on December 19. So, twelve days of continuous operation for the Command Module and three days on the Moon for the LEM. How did they do this without solar panels or an RTG? NASA solved the power problem by inventing a new type of power system. It was called a hydrogen fuel cell and here is how it worked. Usually to produce power we put gasoline in our cars, and it is burned in a piston based internal combustion engine. This engine pulls air into the engine to mix with gas for combustion. This is how we power our cars. The internal combustion engine is over one hundred years old and works very well but it can only use about 38% of the available energy in the gasoline. This was not efficient enough for Apollo. They had to find a better way to generate and store power. The first crude fuel cell had been invented in 1838 by Sir William Grove. It was little more than a curiosity. It used a sulfuric acid solution as an electrolyte with hydrogen and oxygen input lines and wires completing the circuit. So how does a fuel cell work? You apply electricity to separate hydrogen and oxygen or make them another way. You put the hydrogen and oxygen on separate sides of a membrane or other separator. Electrons will try to get from the hydrogen to the oxygen. They can leave the hydrogen allowing the charged hydrogen ion to travel through a membrane that only allows charged particles to travel through it. You make these electrons go through a wire to get around the membrane to the oxygen. Electrons moving through a wire is what we call electricity. Once on the oxygen side they can combine with the oxygen and water to produce a hydroxyl ion. This ion goes through the membrane, combines with the hydrogen, and produces water. This recombination produces a lot of heat unless you use a catalyst to mediate the reaction. Platinum works best but is expensive. Nickel can work also but you must make the pressure of your hydrogen and oxygen gas very high, about 40 atmospheres, or let it operate at a much higher temperature. This system will run as long as you put hydrogen and oxygen in, and the membrane separator stays in good shape. The electrolyte helps to carry the electron across. The 1838 fuel cell used sulfuric acid as an electrolyte. In 1932 Francis Thomas Bacon improved the fuel cell using an alkaline electrolyte. This was the type of fuel cell chosen by Apollo. It is about 70% efficient in converting chemical energy from the hydrogen and oxygen into electricity. So, you can put hydrogen in one side of a fuel cell, oxygen in the other, the hydrogen can only go through the separator if it gives up an electron, the oxygen can only go through if it gains one, this makes the electron go through a wire to get from one side to the other. The moving electron is used as a power source. This worked so well for Apollo that it was continued for the space shuttle program. These fuel cells were fed by hydrogen and oxygen tanks...
References
https://www.nasa.gov/centers/glenn/technology/fuel_cells.html
https://www.energy.gov/eere/fuelcells/types-fuel-cells
https://airandspace.si.edu/collection-objects/fuel-cell-gemini/nasm_A19660646000
https://www.sciencedirect.com/topics/engineering/molten-carbonate-fuel-cell#:~:text=3%20Molten%20Carbonate%20Fuel%20Cells,temperatures%20over%20600%C2%B0C.&text=MCFCs%20use%20an%20electrolyte%20composed,is%20chemically%20inert%20and%20porous.
https://www.youtube.com/watch?v=tNw9rVygWfU
http://nassp.sourceforge.net/wiki/Electrical_Power_System_(CSM)
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090016299.pdf
https://www.hq.nasa.gov/alsj/CSM10_Displays_&_Controls_pp83-86.pdf
http://nassp.sourceforge.net/wiki/CSM_panel_reference

Видео Understanding Fuel Cells and Power Systems канала Terran Space Academy