Volume 4 fuel cells and hydrogen technology 4 02 – current perspective on hydrogen and fuel cells

Volume 4 fuel cells and hydrogen technology 4 02 – current perspective on hydrogen and fuel cells Volume 4 fuel cells and hydrogen technology 4 02 – current perspective on hydrogen and fuel cells Volume 4 fuel cells and hydrogen technology 4 02 – current perspective on hydrogen and fuel cells Volume 4 fuel cells and hydrogen technology 4 02 – current perspective on hydrogen and fuel cells

4.02 Current Perspective on Hydrogen and Fuel Cells K Burke, NASA Glenn Research Center, Cleveland, OH, USA Published by Elsevier Ltd 4.02.1 4.02.1.1 4.02.1.1.1 4.02.1.1.2 4.02.1.1.3 4.02.1.1.4 4.02.1.1.5 4.02.1.1.6 4.02.1.2 4.02.1.3 4.02.1.4 4.02.1.4.1 4.02.1.4.2 4.02.2 4.02.2.1 4.02.2.2 4.02.2.3 4.02.3 4.02.3.1 4.02.3.1.1 4.02.3.1.2 4.02.3.1.3 4.02.3.1.4 4.02.3.1.5 4.02.3.2 4.02.3.2.1 4.02.3.2.2 4.02.3.2.3 4.02.3.2.4 4.02.3.2.5 4.02.4 References Space Applications of Hydrogen Space Propulsion Atlas–Centaur Apollo Saturn Space Shuttle Delta IV Other LH2/LOX-powered rockets Advanced space propulsion technology Space Battery Power and Energy Storage – NiH2 Batteries Astronaut Environmental Control and Life Support Scientific Instrument Cooling Wide-Field Infrared Survey Explorer Planck Space Applications of Fuel Cells Gemini Apollo Space Shuttle Other Current Uses of Hydrogen and Fuel Cells Current Uses of Hydrogen Ammonia production Oil refinery use Methanol production Other chemical manufacturing Other uses Current Uses of Fuel Cells Electric power generation Backup power supplies Portable electronics Motor vehicles Other markets Conclusion 29 30 30 30 32 34 36 37 39 42 42 43 43 45 45 48 49 50 51 52 52 53 53 54 56 58 58 58 59 61 62 62 4.02.1 Space Applications of Hydrogen The general public in recent years has been exposed more and more to the topics of hydrogen and fuel cells, and with good reason Worldwide concern about the diminishing supply of hydrocarbon fuels that play a fundamental role in the world energy mix and an equally worldwide concern over the effects on the world’s environment of burning hydrocarbon fuels are two compelling reasons why hydrogen and fuel cells are frequent topics in the world’s daily news Even though hydrogen is produced in great quantities industrially, the general public has little or no direct experience with hydrogen, so the public’s general knowledge is limited to film footage of the Hindenburg burning and crashing and rockets violently leaving the launch pad The gap in knowledge is filled with instinctual suspicion and fear of the unknown This current public perspective on hydrogen is changing as more information about hydrogen and a ‘hydrogen economy’ is available Over time, the image of hydrogen as a future potential fuel in the public mindset is becoming less fearsome and more appreciated for its unique and beneficial characteristics Hydrogen is the ‘cleanest’ of all fuels because as it is oxidized (burned), it produces only water Hydrogen is abundant over the entire planet, but because of hydrogen’s reactivity, it is rarely found in its pure gaseous state Hydrogen is readily produced from methane, or by the electrolysis of water For its mass, hydrogen packs a lot of energy; a fact that makes it a highly used fuel for rockets The public is largely unaware of how critical hydrogen is to the production of commonly used commodities such as gasoline and fertilizer This is probably because the hydrogen is produced where it is used, at industrial sites well beyond public view and awareness Hydrogen today is largely produced from natural gas which is primarily obtained from nonrenewable sources as are other hydrocarbon fuels One of hydrogen’s uses that has been widely appreciated is its use for space travel Hydrogen has been critical to both the propulsion of spacecraft and the generation of electrical power while in space Hydrogen is widely used by the United States, Comprehensive Renewable Energy, Volume doi:10.1016/B978-0-08-087872-0.00402-9 29 30 Current Perspective on Hydrogen and Fuel Cells Table Rocket propellant performance comparison Oxidizer Fuel Mixture ratio fuel to oxidizer Specific impulse (s, sea level) Density impulse (kg-s l−1, SL) Liquid Oxygen Liquid hydrogen Liquid methane Ethanol + 25% water Kerosene Hydrazine Monomethyl hydrazine Unsymmetrical dimethyl hydrazine 5.00 2.77 1.29 2.29 0.74 1.15 1.38 381 299 269 289 303 300 297 124 235 264 294 321 298 286 Notes: Specific impulses are theoretical maximum assuming 100% efficiency; actual performance will be less All mixture ratios are optimum for the operating pressures indicated, unless otherwise noted LO2/LH2 mixture ratios are higher than optimum to improve density impulse Where kerosene is indicated, the calculations are based on n-dodecane Europe, and Japan for rocket propulsion, and will continue to be in the future Hydrogen’s use in fuel cells to make electrical power for spacecraft for nearly 40 years has been and continues for many to be a fascinating and mysterious process The current development of commercial uses for fuel cells that use hydrogen has captured the public’s attention and hopes that the combination of hydrogen and fuel cells might one day help reduce the concerns about the world’s future energy and environment 4.02.1.1 Space Propulsion Hydrogen use as a chemical propellant is unquestionably the most important space application of hydrogen In terms of mass of hydrogen used, the use of hydrogen propellant dwarfs all other space applications of hydrogen combined The reason for the use of hydrogen is that hydrogen is the most efficient propellant Specific impulse is a measure of the change of momentum per unit weight of the propellant on Earth The higher the specific impulse, the less the weight of propellant needed Table shows a comparison of liquid fuel rocket propellants [1] 4.02.1.1.1 Atlas–Centaur The Atlas–Centaur rocket was the first rocket to use the combination of liquid hydrogen/oxygen (LH2/LOX) for propulsion This rocket’s second stage, Centaur, used the RL10 LH2/LOX rocket engine shown in Figure The RL10 manufactured by Pratt and Whitney was the first engine to use LH2/LOX Figure shows a simplified flow schematic of the RL10 engine The RL10 used liquid hydrogen to cool the engine nozzle, and the heat absorbed by the liquid hydrogen caused the hydrogen to expand, after which it flowed through a turbine The rotation of the turbine was mechanically coupled to the LH2 and LOX pumps which pump the propellants to the combustion chamber This synergy of design made the engine lightweight and very reliable The RL10 was first run in July 1959, and was first flight tested with the Centaur on 27 November 1963 The test flight was delayed to allow for the mourning of President Kennedy, who was shot days earlier [4] Upgraded versions of the RL10 are used to currently launch Atlas–Centaur rockets and on the upper stage of the Delta IV rocket being used currently Figure shows a cutaway view of the Centaur rocket The Centaur rocket uses helium to pressurize the hydrogen and oxygen propellants The pressurized propellants rigidize the structure of the rocket which minimizes the mass of the rocket structure Using pressurized propellants to rigidize a rocket’s structure was initially demonstrated during a US Air Force missile project called MX-774 Although this project was cancelled before the development was completed, Charlie Bossart, the MX-774 designer, applied this knowledge to the design of the Atlas Later, this ‘pressure-stabilized’ approach was used by Krafft Ehricke as a key design element of the Centaur [4] Figure shows the dual engine version of the Centaur upper stage Together, the RL10 LH2/LOX rocket engine and the lightweight Centaur structure gave NASA a lightweight powerful upper stage The powerful Centaur upper stage when mated to the lightweight Atlas provided NASA with a launch vehicle capable of putting payloads beyond low Earth orbit (LEO; 160–2000 km altitude) and out into space (>2000 km altitude) Figure shows an exploded view of an Atlas–Centaur rocket 4.02.1.1.2 Apollo Saturn The Apollo missions to the moon used the Saturn V rocket The Saturn V was a three-stage rocket The first stage was to carry the Saturn rocket to an altitude of ∼200 000 feet (61 km) It used five engines that burned kerosene and liquid oxygen as propellant to produce 600 000 lbs (34 000 000 N) of thrust There were no LH2/LOX engines then (or now) capable of producing such enormous thrust Its second and third stages which burned sequentially used LH2/LOX The payloads to be launched required more powerful LH2/LOX engines (200 000 lbs/890 000 N of thrust) than the RL10 LH2/LOX engine (20 000 lbs/89 000 N of thrust) This required the development of the J-2 LH2/LOX by Rocketdyne shown in Figure Current Perspective on Hydrogen and Fuel Cells 31 Figure Pratt and Whitney RL10 [2] LH2 pump Turbine LOX pump Control valves Combustion Chamber Heat exchanger Nozzle Figure RL10A-3 rocket engine flow schematic [3] The second stage of the Saturn V, called SII, used five J-2 engines to provide million pounds of thrust The SII stage had a diameter of 10 m and a length of ∼24.9 m Filled with propellants, its gross mass was ∼480 000 kg, and when empty, a mass of ∼36 000 kg The burn time for the second stage was 367 s [9] Figure shows an illustration of the SII stage, and Figure shows the SII stage being hoisted into a test stand at the NASA Stennis Space Center The third stage of the Saturn V used one J-2 engine, which provided ∼200 000 lbs of thrust The SIII stage had a diameter of 6.6 m and a length of ∼17.8 m Filled with propellants, its gross mass was 119 900 kg, and when empty, a mass of ∼11 000 kg The burn time for the second stage was 475 s [12] An upgraded version of the J-2 engine, called J-2X, is being currently developed for NASA for further exploration of the Moon and Mars The J-2X with 294 000 lbs of thrust will be more powerful than the J-2 engine The J-2X engine requirements call for an exit 32 Current Perspective on Hydrogen and Fuel Cells Equipment module Stub adapter LH2 tank Fuel slosh Radiation shield LOX tank Baffle Intermediate bulkhead Propellant utilization probe Intermediate adapter Helium bottle RL10 engines Figure Cutaway view of Centaur upper stage [5] Figure Dual engine Centaur upper stage From NASA Image Exchange, ID No KSC-00PP-0426, NASA Kennedy Space Center (dual engine Centaur Photo) http://images.ksc.nasa.gov/photos/2000/low/KSC-00PP-0426.gif [6] diameter of ∼47 cm, a length of 72.8 cm, and a mass of 2477 kg [13] The J-2X is to be used in the upper stage of the NASA Space Launch System (SLS) which will launch a crew and cargo into LEO The NASA SLS will also be used to lift exploration craft beyond Earth orbit 4.02.1.1.3 Space Shuttle The Space Shuttle was launched using a combination of two solid rocket motors and three LH2/LOX engines The solid rocket motors burn a solid propellant and cannot adjust their level of thrust, whereas the LH2/LOX engines use liquid propellants and Current Perspective on Hydrogen and Fuel Cells Juno spacecraft Forward load reactor RL10 Centaur engine Payload fairing Launch vehicle adapter Atlas V booster Solid rocket boosters 33 Centaur Boat tail Centaur interstage adapter Booster interstage adapter RD-180 engine Figure Atlas–Centaur rocket [7] Vehicle effectivity J-2 engine 11.1 FT 6.8 FT SA-201 THRU SA-203 SA-204 THRU SA-207&SA-501 THRU SA-503 SA-208 & subsequent; and SA-504 & subsequent Thrust (altitude) 200 000 lb 225 000 lb 230 000 lb Thrust duration 500 s 500 s 500 s Specific impulse 421 418 419 (lb-s/lb) 480 lb 492 lb 480 lb Engine weight dry Engine weight 609 lb 609 lb 621 lb burnout Exit to throat area 27.5:1 27.5:1 27.5:1 ratio LOX and LH2 LOX and LH2 LOX and LH2 Propellants 5.00 ± 2(%) 5.50 ± 2(%) 5.50 ± 2(%) Mixture ratio Contractor: NAA/Rocketdyne Vehicle application: SAT IB/S-IVB STAGE (one engine) SAT V/S-II STAGE (five engines) SAT V/S-IVB STAGE (one engine) Figure Rocketdyne J-2 rocket engine From NASA Image Exchange, ID No MSFC-9801770, NASA Marshall Space Flight Center (J2 Engine Slide) http://mix.msfc.nasa.gov/IMAGES/MEDIUM/9801770.jpg [8] have their thrust adjusted during the ascent Unlike the Saturn V where the first stage is nearly complete with its burn when the second stage starts its burn, the Space Shuttle’s propulsion combination propelled the Space Shuttle simultaneously until the solid rocket motors completed their burn The solid rocket motors then separated from the Space Shuttle and fell back to Earth where they were recovered, refurbished, and reused The three LH2/LOX engines then continued to burn, eventually lifting the Space Shuttle into LEO Figure shows the Space Shuttle shortly after liftoff with both the solid rocket motors and the LH2/LOX engines operating The large orange tank shown in Figure is the LH2/LOX storage tank This tank was the only expendable portion of the Space Transportation System, separating from the Space Shuttle after the LH2/LOX engines completed their burn Unlike the Saturn V and all previous rockets, the Space Shuttle was reusable Following its 1–2-week mission, the Space Shuttle reentered the Earth’s atmosphere, glided, and then landed on a landing strip 34 Current Perspective on Hydrogen and Fuel Cells Second stage (S-II) Saturn V Manhole cover LH2 Tank pressure line Cable tunnel Gas distributor LOX vent line Mast Second separation plane Work platform Fuel level sensor J-2 engine Heat shield Ring slosh baffle LOX sump LH2 suction line Ullage rocket Saturn V Figure Saturn V second stage, SII From Marshall Space Flight Center Image Exchange, Photo No 9801810 http://mix.msfc.nasa.gov/IMAGES/ MEDIUM/9801810.jpg [10] Figure SII lifted into test stand From NASA Image Exchange, ID No 67-701-c, NASA Stennis Space Center (SII stage of Saturn V rocket photo) http:// www.ssc.nasa.gov/sirs/photos/history/low/67-701-c.jpg [11] The Space Shuttle Main Engine (SSME) was unique, in that it was the only reusable LH2/LOX engine in the world It was designed for 7.5 h of operation over an average life span of 55 starts [15] The SSME was much more powerful than the J-2 engine (470 000 lbs of thrust (at vacuum) vs 200 000 lbs) The SSME consumed 4420 kg per minute of LH2 and 26 450 kg per minute of LOX for ∼8.5 The SSME had an exit diameter of 230 cm, a length of 427 cm, and a mass of 3526 kg [16, 17] Figures 10 and 11 show the SSME [18, 19] The SSME is one of the rocket engines being considered for the first stage of NASA’s new SLS 4.02.1.1.4 Delta IV The Delta family of rockets started with the first launch of a Delta rocket on 13 May 1960 The early Delta rockets did not use LH2 as a propellant The Delta rocket evolved through continuous improvement from a Delta A rocket in 1962 through a Delta N rocket in Current Perspective on Hydrogen and Fuel Cells 35 Figure Space Shuttle after Liftoff From NASA Image Exchange, ID No STS062(S)055, NASA Johnson Space Center http://images.jsc.nasa.gov/lores/ STS062(S)055.jpg [14] Figure 10 Space Shuttle Main Engine From NASA Image Exchange, ID No KSC-04PD-1643, NASA Kennedy Space Center http://images.ksc.nasa.gov/ photos/2004/low/KSC-04PD-1643.gif [18] 36 Current Perspective on Hydrogen and Fuel Cells Figure 11 Test firing of the SSME From NASA Image Exchange, Photo No MSFC-7995081 http://mix.msfc.nasa.gov/IMAGES/ MEDIUM/7995081.jpg [19] 1972 This improvement continued through 1972–89 with Delta Series 904, 1000, 2000, 3000, 4000, and 5000 This in turn was followed by the Delta II Series 6000 and 7000 from 1989 through 2000 After two failures, a Delta III was successfully launched on 23 August 2000 [20] The Delta III used the Pratt and Whitney RL10 LH2/LOX engine for the upper stage This was however the only successful launch of the Delta III as it was quickly replaced by the higher performance Delta IV The first Delta IV was launched on 20 November 2002 [21] The Delta IV series continues to be launched The Delta IV series uses the RS-68 LH2/LOX engine for its first stage The Delta IV-4M (Medium Lift) uses a single RS-68 LH2/LOX engine, whereas the Heavy Lift version uses three RS-68 LH2/ LOX engines [22] The RS-68 LH2/LOX rocket engine was developed by Rocketdyne in 1998 The RS-68 is the largest and most powerful LH2/LOX engine in the world The RS-68 is more powerful than the SSME engine (758 000 lbs of thrust vs 470 000 lbs) The RS-68 is ∼244 cm in diameter and 521 cm in length, and has a mass of 6761 kg [23] Figure 12 shows the RS-68 being test fired [24].The RS-68 is a candidate for possible use in NASA’s new SLS 4.02.1.1.5 Other LH2/LOX-powered rockets Only recently, nations other than the United States have started to produce LH2/LOX engines The Japanese have produced two engines which are used for first and second stages The LE-5 is used for the second stage, and had its first flight in 1986 The LE-5 produces 23 100 lbs of thrust and has a diameter of 2.49 m, a length of 2.68 m, and a mass of 245 kg [25] Figure 13 shows the LE-5 [26] Japan also produced the LE-7 designed for a first stage, and had its first flight in 1994 The LE-7 produces 242 000 lbs of thrust and has a diameter of m, a length of 3.4 m, and a mass of 1714 kg [27] Figure 13 also shows the LE-7 [26] Japan’s H-II unmanned expendable launch vehicle uses one LE-7A engine in its first stage and one LE-5 is used on the upper stage Snecma Moteurs (France) has produced the Vulcain, an LH2/LOX engine designed for a first stage, and had its first successful flight in 1997 [28] The Vulcain produces 256 760 lbs of thrust and has a diameter of 1.76 m, a length of 3.0 m, and a mass of 1700 kg [29] Figure 14 shows the Vulcain [28] The Ariane launch vehicle uses a single Vulcain as its first stage engine The Energia–Buran shown in Figure 15(a) is a Russian-built launch system whose second stage (shown in Figure 15(b)) is fueled by LH2/LOX The second stage is powered by four RD-0120 engines shown in Figure 16 The RD-0120 was similar in performance to the US-built SSME used in the US Space Shuttle The Energia flew only two flights The first of these was on 15 May 1987 with Polyus spacecraft as the payload The second and final launch was with the Russian shuttle vehicle, Buran, on 15 November 1988 The fall of the Soviet Union ended the flights of the Energia and the use of the RD-0120 engines In the 1990s, several other launchers were designed with an Energia core stage, but none were ever built Starting in 2001, another Russian LH2/LOX engine, the RD-0146, was developed, but as of 2010 had not yet flown Current Perspective on Hydrogen and Fuel Cells 37 Figure 12 RS-68 test firing From NASA Image Exchange, Photo No MSFC-0700063 http://www.nasa.gov/images/content/ 148709main_d4_testing_08.jpg [24] LE-5/5A/5B (LOX/LH) LE-7 (LOX/LH) Figure 13 Japan’s LE-7 LH2/LOX engine [25] 4.02.1.1.6 Advanced space propulsion technology Unlike all previous mentioned rocket engines that use hydrogen, advanced space propulsion that uses hydrogen does not combust the hydrogen Instead, the hydrogen is heated to high temperatures from high-energy sources and then the hydrogen exits the engine at a high velocity The specific impulse from these engines varies depending on the temperature to which the hydrogen is heated, but in general the specific impulse is much higher than that of conventional hydrogen/oxygen engines One common drawback to this 38 Current Perspective on Hydrogen and Fuel Cells Figure 14 Vulcaine rocket engine [28] (a) Figure 15 (a) Energia–Buran (b) Energia second stage [30, 31] (b) Current Perspective on Hydrogen and Fuel Cells Nickel backplate diaphragm section 49 Teflon seal Oxygen Nickel + nickel oxide electrode Nickel electrode Welds Oxygen Hydrogen Potassium hydroxide Nitrogen Nitrogen Nitrogen Spacer Figure 32 Apollo fuel cell – Cross section (two cells) From NASA Apollo Command Module news reference North American Aviation, 1968, p 108 http://history.nasa.gov/alsj/CSMNewsRef-Boothman.html [60] consisted of a stack of 31 cells in electrical series Each cell had a diameter of 20 cm The stack of cells was placed inside a pressurized nitrogen jacket Above the stack was an accessory section that contained the hydrogen pump/separator, the coolant pump, the coolant accumulator, and the reactant pressure controls The Apollo fuel cell system shown in Figures 34 and 35 was about 112 cm in length and 57 cm in diameter and weighed about 109 kg Three fuel cell systems were connected electrically in parallel to share the electrical load for the Apollo spacecraft The Apollo fuel cell system flow schematic is shown in Figure 36 Each fuel cell system was capable of steadily producing 1420 W within the normal voltage range of the Command Module voltage bus (27–31 VDC) The Apollo fuel cell system circulated the hydrogen through the cell stack which both removed the water that was formed as well as the waste heat The water was condensed from the circulating hydrogen and the condensed water was dynamically separated and pumped out by hydrogen pump/separator During the test flights AS202, AS501, AS502 and the flights of Apollo 7, and 9, ∼450 kg of potable water was produced by the fuel cell systems Of this, about 60% was consumed directly by the crews The average mission power level required from each fuel cell system was 600W, so in the event of two system failures, a single fuel cell system could still meet the power demands of the mission [65] 4.02.2.3 Space Shuttle The Space Shuttle was a substantially larger, more versatile, and more complex spacecraft than the Apollo The nominal power consumption of the Space Shuttle was 7000 W (plus additional power required for payloads it was carrying) and that of the Apollo was ∼1690–4260 W A more highly developed and improved version of the Apollo fuel cell was selected to provide the on-board power of the Space Shuttle because, while advances in membrane technology had been made by the early 1070s, the potassium 50 Current Perspective on Hydrogen and Fuel Cells To regulator Hydrogen regeneration To condenser Oxygen purge manifold Hydrogen exhaust manifold Oxygen intake manifold Hydrogen, water Primary bypass valve Hydrogen intake manifold Torsion rod Figure 33 Apollo fuel cell module From NASA Apollo Command Module news reference North American Aviation, 1968, p 110 http://history.nasa.gov/ alsj/CSMNewsRef-Boothman.html [61] hydroxide fuel cell still offered the best option to meet the Space Shuttle life and performance requirements The Space Shuttle fuel cell is shown in Figures 37 and 38 Each cell contained an active area of 465 cm2 (21.6 cm  21.6 cm) The Space Shuttle fuel cell used an alkaline 35% KOH electrolyte contained within an asbestos matrix, and operated at a nominal temperature of 93 °C and a pressure of ∼4 atmospheres To accommodate the changing volume of electrolyte, an electrolyte reservoir plate (ERP) made of sintered nickel contacted the fuel cell anode (hydrogen consuming electrode for alkaline cells) The ERP also formed the hydrogen compartment of the cell The cell assembly consisted of the cell and two separator plates The power section of the Space Shuttle fuel cell power plant, shown in Figure 39, consisted of 96 cells, arranged in three substacks of 32 cells each The 96 cells used common hydrogen, oxygen, and coolant manifolds The three substacks of 32 cells each were connected electrically in parallel as shown in Figure 40 At one end of the power section was an accessory section that contained the hydrogen pump/separator, the coolant pump, the coolant accumulator, the coolant control valves, the reactant pressure controls, and the electrical control unit Three fuel cell systems were connected electrically in parallel to share the electrical load for the three power buses onboard the Space Shuttle Each Space Shuttle fuel cell system, shown in Figures 41 and 42, was about 101.6 cm long, 35.6 cm high, and 38.1 cm wide, and weighed about 116 kg Each fuel cell system is capable of steadily producing 7000 and 12 000 W for a 15 period and still operates within the normal voltage range of the Space Shuttle voltage bus (27.5–32.5 VDC) In the event of two fuel cell system failures, a single fuel cell system can provide sufficient power to operate the Space Shuttle The location of the fuel cell systems aboard the Space Shuttle is shown in Figure 43 The Space Shuttle fuel cell system flow schematic is shown in Figure 44 Like the Apollo fuel cell system, the Space Shuttle fuel cell system circulated the hydrogen through the cell stack which removed the water that was formed The water was condensed from the circulating hydrogen and the condensed water was dynamically separated and pumped out by hydrogen pump/separator A liquid coolant (FC-40) was circulated through the cell stack to remove heat Each fuel cell system was serviced between flights and reused until a total of 2000 h of online service time had been accumulated 4.02.3 Other Current Uses of Hydrogen and Fuel Cells Hydrogen and fuel cells are currently being used for purposes other than space applications Hydrogen plays a key role in agriculture (the production of ammonia), energy (oil refining), and other chemical production (methanol and other Current Perspective on Hydrogen and Fuel Cells Weight 245 lb 51 Efficiency kw h electricity per 0.77 lb of reactant Rating 1.42 kw 29 ± V Accessory section 44 IN Shock mount (3) Module support assembly Plumbing connections Electrical connections Pressure jacket 22 in Figure 34 Apollo fuel cell system From NASA Apollo Command Module news reference North American Aviation, 1968, p 100 http://history.nasa.gov/ alsj/CSMNewsRef-Boothman.html [62] chemicals) In many cases, the quantity of hydrogen used is great enough that it is generated on-site as opposed to being delivered to the point of use by pipeline or bottles This on-site generation and on-site usage is the norm rather than the exception Fortunately, hydrogen is easily and cheaply produced from either hydrocarbon sources (principally methane) or electrolysis of water The fuel cell industry is a new industry that is in the process of commercializing fuel cells The US Fuel Cell Council, a nonprofit trade association dedicated to the commercialization of fuel cells, was formed in 1998 [71] Much of the fuel cell industry effort has been in research and development, prototype development, pilot-scale demonstrations, small fleet demonstrations, and the like Recently, true commercial deployments of fuel cell products have happened, but the industry still faces challenges with incumbent power technologies, lack of public hydrogen infrastructure, underdeveloped municipal codes and safety standards, and a general lack of awareness by the public and industry about the benefits of adopting this alternative power source Fuel cells are finding use as stationary electric power generation sources, as backup electrical power sources, in portable electronics, and in motor vehicles The quiet, nonpolluting characteristics of fuel cells and their ability to produce substantial amounts of power are key to their present adoption 4.02.3.1 Current Uses of Hydrogen Figure 45 is a summary of the major applications of hydrogen use, the quantity of use, and the approximate value of the economic market for hydrogen 52 Current Perspective on Hydrogen and Fuel Cells Nitrogen storage tank Glycol accumulator Bay Nitrogen fill valve Glycol pump Negative power lead Pressure tank Support cone Nitrogen pressure transducer Bay Bay Nitrogen pressure regulator Nitrogen sampling valve Positive power lead Power Glycol from radiator Glycol to radiator Hydrogen vent Nitrogen fill Water out Oxygen vent Oxygen supply Hydrogen supply Heaters Controls Instrumentation Figure 35 Apollo fuel cell system accessories From NASA Apollo Command Module news reference North American Aviation, 1968, p 106 http:// history.nasa.gov/alsj/CSMNewsRef-Boothman.html [63] 4.02.3.1.1 Ammonia production Ammonia production is the largest consumer of hydrogen Almost half of the hydrogen produced in the world is used for this purpose [74] Hydrogen is typically produced on-site from methane Methane is reacted with steam in a process called steam reforming This reaction produces hydrogen and carbon monoxide The carbon monoxide is then reacted with more steam in a reaction called the water gas shift reaction to produce carbon dioxide and more hydrogen The hydrogen produced by these processes is used in a process called the Haber process, named after its inventor, Fritz Haber [75], which reacts the hydrogen with nitrogen at high temperature and pressure to produce ammonia as shown below N2 gị ỵ H2 gị is in equilibrium with NH3 ðgÞ at 150−250 bar; 300−550 ˚C The ammonia is for use primarily as a fertilizer The demand for ammonia is expected to grow as the world population grows 4.02.3.1.2 Oil refinery use Hydrogen is used by oil refineries to break down the hydrocarbons in crude oil into lighter hydrocarbons, such as diesel and gasoline Hydrogen is also used by refineries to remove undesirable contaminants such as sulfur and nitrogen from the hydro­ carbons that contain these elements Hydrogen replaces the sulfur or nitrogen in the hydrocarbon and in the process produces hydrogen sulfide (when removing sulfur) or ammonia (when removing nitrogen) The hydrogen used by refineries is typically produced on-site by the same process used by the ammonia producers Some hydrogen is also produced during the catalytic reforming of naphtha The use of hydrogen is expected to increase because of the demand for low sulfur fuel, greater consumption of low-quality crude, and greater consumption of hydrocarbons in developing economies [76] Current Perspective on Hydrogen and Fuel Cells Potable water pH sensor 53 Hydrogen pump Hydrogen regenerator Inline heater circuit − LOAD + Hydrogen and Fuel cell water (one shown - 31 in series) Hydrogen Check valve Water separator Temperature sensor steam Condensor Nitrogen Bypass valve Temper­ ature sensor H2 steam Nitrogen sampling (for test only) KOH O2 Oxygen Purge valve Hydrogen Coolant pump Coolant regenerator Hydrogen pre heater Orifice Fuel cell module Oxygen regulator Hydrogen regulator Oxygen pre heater Bypass valve Overboard Glycol Glycol accumulator Two step nitrogen gas regulator Glycol Tank Glycol from radiator Glycol to radiator Reactant sov Hydrogen vent N2 Hydrogen feed 245 psi Oxygen feed 900 psi Oxygen vent Nitrogen regulator Nitrogen vent Nitrogen supply solenoid valve Nitrogen Reactant sov Oxygen flow sensor Hydrogen flow sensor Figure 36 Apollo fuel cell system flow schematic From NASA Apollo Command Module news reference North American Aviation, 1968, p 109 http:// history.nasa.gov/alsj/CSMNewsRef-Boothman.html [64] Cathode Matrix Anode Cell ERP Moving electrolyte interface Figure 37 Fuel cell and electrolyte reservoir plate From Orbiter Fuel Cell Powerplant Review and Training course Presented to United Space Alliance, Houston, Texas [66] 4.02.3.1.3 Methanol production Hydrogen is used to make methanol, with the hydrogen typically being produced from methane on-site in the same manner as for ammonia production and oil refining The mixture of hydrogen and carbon monoxide (called syngas) from the steam reforming process is then reacted on a different catalyst to form methanol Roughly, million tons of methanol are produced in the United States each year Methanol is a widely used solvent and is used to produce paints, adhesives, inks, varnishes, paint strippers, and other products About 40% of the methanol is used to produce formaldehyde, which is used to produce plastics, plywood, paints, explosives, and permanent press textiles 4.02.3.1.4 Other chemical manufacturing Hydrogen is used for other chemical manufacturing, most notably the hydrogenation of unsaturated carbon bonds Unsaturated carbon bonds are double bonds between two carbon atoms The double carbon bond reduces the bonds that exist between carbon 54 Current Perspective on Hydrogen and Fuel Cells Figure 38 Space Shuttle fuel cell assembly From Orbiter Fuel Cell Powerplant Review and Training course Presented to United Space Alliance, Houston, Texas [66] Figure 39 Space Shuttle fuel cell power section From Orbiter Fuel Cell Powerplant Review and Training course Presented to United Space Alliance, Houston, Texas [66] and hydrogen in hydrocarbons These hydrocarbons are referred to as ‘unsaturated’ Single bonds between carbon atoms maximize the hydrogen content in hydrocarbons, and are referred to as ‘saturated’ A common hydrogen application is the hydrogenation of unsaturated animal fats and oils The conversion of these unsaturated compounds to saturated compounds increases their melting point, and makes them more stable for use in frying foods 4.02.3.1.5 Other uses Other hydrogen uses generally not need the large quantities of hydrogen as the applications mentioned above The methods for obtaining the hydrogen for these other uses are also generally different In these other applications, the hydrogen is delivered either in bottles or in tube trailers In some instances, local hydrogen production via water electrolysis provides a better economic solution Hydrogen is used in the metal industry to provide a reducing atmosphere to prevent metal oxidation during various metal production or fabrication operations such as annealing, welding, heat treating, sintering, and brazing Current Perspective on Hydrogen and Fuel Cells Cell #96 (+) Power take off cables (+) (−) (−) 55 (+) (+) (−) Cell #1 (−) Power take off cables Figure 40 Space Shuttle fuel cell power section electrical power connections From Orbiter Fuel Cell Powerplant Review and Training course Presented to United Space Alliance, Houston, Texas [66] Figure 41 Space Shuttle fuel cell system From NASA Image Exchange, NASA Johnson Space Center, Photo No S83-28219 http://images.jsc.nasa.gov/ lores/S83-28219.jpg [67] Figure 42 Space Shuttle fuel cell preflight preparation From Kennedy Space Center Multimedia Gallery, Photo No KSC-06PD-0005 http://mediaarchive ksc.nasa.gov/detail.cfm?mediaid=27656 [68] Hydrogen is used in the semiconductor industry Hydrogen is used as an impurity to change the behavior of semiconductors Hydrogen binds to native defects or to other impurities that eliminate their electrical activity (a process called passivation) CMOS devices require passivation of the Si/SiO2 interface to provide reliable operation A hydrogen atmosphere is often used during the 56 Current Perspective on Hydrogen and Fuel Cells Product water valve module Fuel cell power/environmental control and life support system heat exchanger Prelaunch umbilical (disconnected at T:4 hours) Water vent Oxygen dewars Hydrogen dewars Coolant loop service panel Main bus distribution assemblies, typical (three places) Fuel cell power plants (3) Figure 43 Space Shuttle fuel cell power plant location From National Aeronautics and Space Administration NASA History Office SP-407 http:// history.nasa.gov/SP-407/p63.htm [69] growth of semiconductors Several semiconductor growth techniques such as vapor-phase transport, hydrothermal growth, and metal-organic chemical vapor deposition include great quantities of hydrogen in the growth environment [77] 4.02.3.2 Current Uses of Fuel Cells Figure 46 is a summary of the US fuel cell market, the major applications that use fuel cells, and the approximate value of the fuel cell economic market Current Perspective on Hydrogen and Fuel Cells Figure 44 Space Shuttle fuel cell power plant flow schematic [70] World hydrogen usage $50 billion yr–1, 478 × 109 m3 yr–1 (2013 forecast) 6.0% 6.4% Ammonia production 10.0% Oil refinery use 40.3% Methanol production Other chemical manufacturing 37.3% Other uses References [72],[73] Figure 45 World hydrogen usage [72, 73] US fuel cell usage $975 million yr–1 (2012 forecast) Electric power generation 9.0% Backup power supplies 11.0% 13.0% 46.0% Portable electronics Motor vehicles 21.0% Other markets References [78] Figure 46 US fuel cell usage [73, 78] 57 58 Current Perspective on Hydrogen and Fuel Cells 4.02.3.2.1 Electric power generation Fuel cells are being used as power generators that are independent of the electrical grid or are supplemental to grid electrical power These systems are being used for industrial, commercial, and residential electrical power generation Sometimes, the waste heat produced by the fuel cell system is used for space heating and for producing hot water, which can potentially reduce a user’s energy service cost by 20–40% over conventional services The amount of power these systems produce varies depending on the application Figure 47 shows a commercial/industrial sized phosphoric acid fuel cell unit that produces about 400 kW of electrical power and 500 kW of heat recovery Typically, these systems use natural gas or propane Fuel cells are being used industrially in instances where a gas product is being generated that would otherwise be discarded such as landfill gas, anaerobic digester gas, or industrial hydrogen or hydrocarbon by-products Fuel cells are being used residentially as a combined heat and power units, referred to as CHP units Figures 48 shows two residential sized CHP units The solid oxide fuel cell unit on the left in Figure 48 produces about kW of electrical power and kW of thermal power, and is 55 cm  55 cm  160 cm The high-temperature PEM fuel cell unit shown on the right in Figure 48 produces between 0.5 and kW of electrical power and 7–25 kW of thermal power, and is 101 cm  71 cm  122 cm 4.02.3.2.2 Backup power supplies Fuel cell systems are finding use as backup power systems for customers that require high reliability power for such applications as telecommunications, hospitals, computer centers, emergency response systems, national defense, and homeland security Fuel cell systems are preferred over other alternatives because of their efficient, quiet, and nonpolluting characteristics These systems are essentially identical to those above, except that in these instances the fuel cell system is a secondary power source 4.02.3.2.3 Portable electronics Fuel cell systems are being used for portable applications either as the direct power source for these items or as a portable recharger for the batteries contained in the product As the power of portable products increases and the desire to have these products run longer between recharges becomes stronger, battery technology is not keeping up with the needs of the marketplace Fuel cells are finding a niche to fill in this area because fuel cell systems have the potential to provide specific energy densities (W-h kg−1, W-h l−1) that are much greater than that of battery systems Figure 49 shows two PEM fuel cell-powered portable power sources The product on the left in Figure 49 shows a portable PEM fuel cell system capable of producing 150 W of continuous power for h from the hydrogen produced by the sodium borohydride canisters shown It measures 21.6 cm  34.8 cm  41.1 cm and weighs ∼10.4 kg The PEM hydrogen–air fuel cell product on the right in Figure 49 is designed for recharging of small consumer products, and as of 1 Fuel processor (reformer) The fuel processor reforms the fuel (natural gas) to hydrogen gas to feed the fuel cell stack Fuel cell stack Hydrogen gas and air are combined in an electrochemical process that produces direct current (DC) power, pure water, and heat The by-product water is utilized in the operation of the power plant The usable heat is available for meeting other facility energy requirements (e.g., hot water, space heating, air conditioning, and cooling) Figure 47 Commercial/industrial 400 kW fuel cell system [79] Power conditioner The DC power provided by the fuel cell stack is conditioned to provide high-quality alternating current (AC) power output Current Perspective on Hydrogen and Fuel Cells 59 Figure 48 Residential-sized fuel cell systems From Hexis Ltd Galileo product brochure http://www.hexis.com/downloads/HEXIS_Galileo1000N.jpg [80] and Plug Power Inc Gensys high-temperature fuel cell system for residential applications brochure http://www.plugpower.com/userfiles/file/ GenSysHT-03-09.pdf [81] Figure 49 Portable fuel cell power systems From Horizon Fuel Cell Technologies Pte Ltd Minipak product brochure http://www.horizonfuelcell.com/ file/MiniPak_brochure.pdf [82] and US Fuel Cell Council Industry Overview 2010, p 22 http://www.fchea.org/core/import/PDFs/Technical%20Resources/ IndustryOverview2010.pdf [83] 2011 retailed for under US$100 The hydrogen is contained in small, rechargeable metal hydride cylinders (shown in Figure 49) This unit produces W of power and has the energy of 20 typical AA batteries Prototype fuel cells are being developed as the power source for small handheld electronics such as cell phones Figure 50 shows a prototype of this PEM fuel cell that doubles the time between recharges 4.02.3.2.4 Motor vehicles There has been significant development of fuel cells, particularly PEM fuel cells, for motor vehicle applications The reasons for this are twofold: First, the hydrocarbon fuel for motor vehicles has continued to escalate in cost to the general public, and the adequacy of its future supply is uncertain Fuel cells that can operate on hydrogen offer a solution to this potential worldwide problem The second reason is that the hydrocarbon fuels used in motor vehicles produce undesirable environmental effects These effects range 60 Current Perspective on Hydrogen and Fuel Cells Figure 50 Prototype fuel cell for consumer handheld products From US Fuel Cell Council Industry Overview 2010, p 22 http://www.fchea.org/core/ import/PDFs/Technical%20Resources/IndustryOverview2010.pdf [83] from local pollution effects in vehicle dense metropolitan areas (particularly in developing countries) to worldwide pollution effects from the production and accumulation of greenhouse gases The low pollution footprint of fuel cells provides an attractive alternative to current technology Figure 51 shows a fuel cell-powered bus Buses are an early adopter market for fuel cells because buses are fleet vehicles that have centralized refueling stations This makes the issue of hydrogen refueling stations less problematic Buses are typically owned and operated by municipalities that can subsidize their operation through government grants Passenger cars are another market for fuel cells Major car companies have developed prototypes and produced small numbers of cars to evaluate performance Fuel cell-powered passenger cars have been built that have the driving characteristics, speed, and driving range of internal combustion engine-powered automobiles Figures 52 and 53 show a pilot production model of a fuel cell-powered automobile Forklifts are another promising market area for fuel cells Fuel cell-powered forklifts are gaining acceptance because these vehicles can be refueled much more rapidly than the recharging of battery-powered forklifts This allows the forklifts to be put back into service rather than being idled while recharging Fuel cell-powered forklifts also not produce the exhaust that hydrocarbon-fueled forklifts produce As with forklifts, economics are driving the acceptance of fuel cell-powered transit buses As Figure 51 Fuel cell-powered bus [76] Current Perspective on Hydrogen and Fuel Cells 61 Hydrogen storage tank Stores hydrogen gas compressed at extremely high pressure to increase driving range Power control unit Governs the flow of electricity High-output battery Electric motor Fuel cell stack Propels the vehicle much more quietly, smoothly, and efficiently than an internal combustion engine and requires less maintenance Converts hydrogen gas and oxygen into electricity to power the electric power Stores energy generated from regenerative braking and provides supplemental power to the electric motor Figure 52 Fuel cell-powered passenger car major components [77] Courtesy of American Honda Motor Co., Inc Figure 53 Fuel cell-powered passenger car on display [78] the price of diesel fuel rises, the high efficiency of fuel cell power systems relative to internal combustion engines is bringing the life cycle costs of the higher priced fuel cell buses in line with conventional diesel-powered buses Also, as with lift trucks, transit buses operate as fleets from a central location, and thus, the hydrogen supply and infrastructure is simplified The passenger car market is the most difficult to enter However, the major manufacturers are on record to offer the driving public fuel cell-powered cars in the near future It is expected that initially the offerings will be fleet operations clustered around available hydrogen fueling facilities, but the offerings will expand as the hydrogen infrastructure is expanded Figure 54 shows two instances of fuel cell-powered forklift use 4.02.3.2.5 Other markets Fuel cells are being introduced to other markets The military is considering the use of fuel cells because their quiet operation permits the stealth transport and operation of troops, whereas the use of diesel engines does not Additional development drivers for the military are cost and risk reduction The cost of delivering diesel to remote base locations can be prohibitively high and in a war zone can come at a significant risk to the supply personnel On-site generation of hydrogen fuel for fuel cell systems can be very cost effective and the risk of injury and fatalities of the supply personnel can essentially be eliminated The military is also interested in fuel cells as power sources for unmanned aerial vehicles (UAVs) and unmanned underwater vehicles (UUVs) In most cases, fuel 62 Current Perspective on Hydrogen and Fuel Cells Figure 54 Fuel cell-powered forklifts [79] From Hexis Ltd Galileo product brochure http://www.hexis.com/downloads/HEXIS_Galileo1000N.jpg [80] cells would replace battery systems and would provide increased operating ranges of the vehicles The use of fuel cells for power generation in space continues to be a highly visible market 4.02.4 Conclusion Hydrogen is a critical part of the current economy in the areas of fertilizer manufacturing and to the refinement of hydrocarbon fuels, yet despite this the public has been oblivious to hydrogen because 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