Hydrogen aircraft propulsion
The 21st century demands an updated and improved aviation propulsion technology. For over 70 years, kerosene has proven itself safe, reliable, efficient, and most importantly, energy-dense.
Hydrocarbons, being abundant, easy to store, and easily combusted in gas turbines, have resulted in the tremendous aviation industry we have today.
Current hydrocarbon aircraft can suffice, providing sufficient payload and range for most missions, only in special occasions is more capability required. Pochari Hydrogen believes the long-range light business jet is an aircraft category that requires a more powerful and modern propulsion system.
We are rapidly approaching a turning point in aviation history. Efforts to improve aviation propulsion are reaching a wall. Efforts to squeeze every last few percentages points of efficiency in turbines are proving increasingly difficult. The gas turbine’s maximum practically attainable efficiency is around 40%, going above this number is nearly impossible. Efforts to improve aerodynamics have also reached the point of diminishing returns. Reducing airframe weight through the use of composites, mainly carbon fiber, has yielded very minimal reductions in airframe mass, in the order of 5-10%. Thus so far we can state that aviation propulsion and airframe design has reached its peak in terms of technological maturity, there is almost nothing left to do to improve aircraft capability, at least nothing currently considered in the aviation industry.
In summary, we have reached the point of diminishing returns.
If little to nothing remains to improve in the powerplant, airframe aerodynamics, or even the fundamentally design itself, we must begin identifying a superior fuel.
Quite surprisingly, there remains a mysterious, obscure, and powerful propellent, the most powerful of any fuel known to man, that attracts little to no attention in aviation circles, this fuel is nothing other than liquid hydrogen as proposed by G. Daniel Brewer in the late 1970s in Burbank, California, and revived by Christophe Pochari in 2018.
Liquid hydrogen is the most powerful fuel available on earth, with gravimetric energy density unmatched by any other fuel, hydrogen’s only downside compared to hydrocarbon is its low volumetric density, but this proves not to be the least bit of a limitation for subsonic flight. For subsonic flight at high altitude, the dominant form of drag is skin friction, a 20-foot diameter airliner fuselage section (Boeing 787) with a total wetted area of 9500 square feet is only subjected to 4400 lbf of drag with an air density of 3.5 Psi and a cruise speed of 560 mph. (http://www.lissys.demon.co.uk). This small amount of drag present in subsonic flight allows us to store ample quantities of hydrogen while adding minimal drag, provided we choose a configuration with the lowest possible surface/volume ratio.
The turbine powerplant itself remains nearly identical, having only slightly modified combustors designed to take advantage of hydrogen’s much higher flame speed. “Hydrogen is a beautiful fuel for turbines” -Willis Hawkins.
Vaporized or liquid hydrogen is delivered from the LH2 tank to the turbine with aluminum piping from dual high-speed centrifugal liquid hydrogen pumps directly attached to the rear of the tank. The boil-off rate in cruise is nearly half of the cruise fuel flow, the difference is provided by vaporizing liquid hydrogen in the fuel supply line or combusting it liquid.
An electric heater maintains a certain vaporization rate to maintain 20 psi in the tank on the ground, and 15 psi during cruise, if the pressure exceeds this, the tank is vented.
Liquid hydrogen can also be combusted directly in the turbine just as gaseous hydrogen can. During takeoff, when the fuel flow required is at a much higher rate than the natural boil-off, the electric heater is turned up to increase the vaporization rate to maintain pressure, shortly after, when fuel flow is reduced to cruise level, the heat is turned down. Turbine compressor bleed air is cooled by the -423 degree LH2, through a light-weight aluminum heat exchanger. Thisallow for higher turbine inlet temperature, and reduced compressor bleed air mass flow, reducing compressor work require, this contributes to a 5% reduction in SFC (Brewer, G. D, 1991)
The total ratio of SFC is reduced by 2.93x over the 2.8x difference from the calorific value difference alone. (Brewer, G. D, 1991)
The liquid tanks are integral with the fuselage. The fuselage material is made of carbon fiber, the tank material is aluminum-lithium, fastened directly to the carbon fiber fuselage with adhesive. 12.7mm of insulation is placed between the carbon fiber skin and aluminum tank wall. Foam insulation is blown inside the frame and between the frame-wall seams where the vacuum panels end. Tank boil-off is 5% per hour on the ground. A specially designed fuel truck connects a flexible hose to the tank when the aircraft is on the ground to vent the boil-off, keeping tank pressure at 21 psi. Hydrogen aircraft are fueled just before take-off, to minimize losses.
The higher energy density of hydrogen allows for a dramatic increase in aircraft range, exactly what business aircraft need. With our hydrogen propulsion system, a 35,000 lb GW aircraft can fly up to 9000 miles non-stop with a 2700 lb payload, whereas the comparable class kerosene-fueled aircraft can only fly 4700 miles, if it were to attempt to fly the equivalent kerosene-fueled aircraft, the fuel load would exceed the useful load by 160%.
Willis Hawkins (C-130 designer) and a strong proponent of hydrogen aircraft, argued nearly a doubling of range is easily achieved with liquid hydrogen propulsion, this turns out to be exactly correct.
There are two fundamental ways to design a hydrogen-powered aircraft, depending on the incentives and aircraft capability required.
The first way is to essential reconfigure existing aircraft types to hydrogen propulsion, by incorporating an in-fuselage tank. This can be done by simply stretching the fuselage, without needing a design an entirely new clean-sheet aircraft. This design may not necessary increase range or payload, since the tank capacity may be limited by the fuselage volume. This type of hydrogen aircraft design would fly approximately the same distance and carry the same payload as kerosene aircraft. The rational to develop this type of hydrogen aircraft would mainly be emission and environmental impact reduction. The only emission from hydrogen combustion in properly designed gas turbine engines is minimal nitrogen oxides, less than 50 ppm. No CO2, CO, PM or any other emission is produced.
The second way to design a hydrogen aircraft is to tailor the design around hydrogen’s improved range capability. This is the option that makes the most sense, as it takes advantage of hydrogen’s superiority as a propellent, allowing the designer to create an aircraft specifically tailored to utilize hydrogen’s enormous performance benefits. Our design is what we term a “flying rocket” which refers to the hydrogen tanking up 85% of the of the aircraft’s volume. This aircraft dubbed the “flying rocket” is a light-jet, under 35,000 lbs gross weight, designed to fly almost 9000 miles (17 hours of flight time) non-stop while carrying a 2500 lb payload, which translates into 6 persons, two pilots, and ample luggage capacity. This ultra-long-range in a relatively small aircraft can only be accomplished with hydrogen, no hydrocarbon fuel possesses the gravimetric energy density. Hydrogen’s outstanding properties as a propellent allow for the creation of an entirely new class of aircraft, that is the small ultra-long-range jet, previously impossible with hydrocarbon fuel.
Hydrogen is a far superior, for more powerful propellant for all aircraft alike, but it improves the capability of smaller aircraft even more. Since lift to drag ratios decrease with size, and specific fuel consumption increases, smaller aircraft gain more from high energy density of the fuel, these two factors have the most influence on how much an aircraft improves with hydrogen. As G. D Brewer said, “the more energy required to perform the mission, the greater the advantage to be gained by using a high energy fuel”
Six factors that determine the performance increase with hydrogen.
#1 L/D ratio
#2 Powerplant SFC
#3 Desired endurance
#4 EW/GW ratio
#5 Tank parasitic drag penalty
#6 Tank surface/volume ratio (Blended wing body aircraft (BWB) or flying wings unsuited for hydrogen propulsion, since multiple small tanks are required)
Hydrogen aircraft propulsion FAQ
#1 Why has no one done this before?
For three reasons.
#1 kerosene remained extremely cheap up until the 21st century, discouraging the development of alternatives, that is hydrogen, despite the performance gains attainable. The price of kerosene still remains under $2/gal, thus we are strongly incentivized to use hydrogen from low-cost energy sources, mainly hydropower, with the lowest levelized cost of $0.85 cents/kwh. Liquefaction adds $1/kg, electrolyzer CAPEX is $0.50/kg, in total we can confidently state hydrogen can be produced for $2/kg for from clean sources, and $1/kg from waste or coal gasification.
#2 The aerospace industry is highly conservative, and unwilling to experiment with unproven technology, capital investment requirements are often very high, and with certification costs, it may take 10 or more years to fully recuperate the development costs, disincentivizing the development of new propulsion technology, especially “unproven” ones.
#3 Most experts in the aerospace industry are not even aware of this obscure and forgotten propulsion technology, G. Daniel Brewer’s book remains in complete obscurity. Prior to Christophe Pochari’s efforts to revive Brewer’s ideas, virtually no attention was paid to hydrogen. Quoting Allan Epstein from Pratt and Whitney “no one has been able to store hydrogen at less than 10% hydrogen by weight, the rest is the tank” His comment summarizes the stance of the current aviation establishment, and indicates the broader industry being almost completely unaware of G. Daniel Brewer’s work and research, of which is freely available on the internet.
#2 Is it safe?
Safety concerns are likely to arise as an argument against a hydrogen propulsion system. Hydrogen will combust at a significantly higher rate than Kerosene. An Ignition source is most likely to occur as a result of a hard impact from a crash. The minimum ignition of energy (MIE) of hydrogen and kerosene is well below even the lowest level impact force that would cause an ignition. In other words, a violent impact, lightning strike, engine failure, foreign object damage, drone strike, or an onboard fire, will ignite kerosene just as easily as liquid hydrogen. A sufficiently violent impact will cause a fracture in the fuel tank regardless of whether it is hydrogen or kerosene. The only major difference will be the manner in which hydrogen will detonate compared to kerosene. Kerosene will detonate, and then slowly burn in a deflagrative manner. Hydrogen will almost immediately detonate completely leaving no residual fuel to burn. G. Daniel Brewer was firm in his belief that hydrogen-fueled aircraft would be significantly SAFER than kerosene-fueled aircraft, thanks to the high flame speed of hydrogen, long periods of deflagration upon impact inherent to jet fuel is no longer an issue with hydrogen, allowing more time for passengers to escape.
#3 Is it really possible to double the range?
This all boils down to how smart the designer is.
If the designer chooses a tank with a fuselage integral tank with a low surface/volume ratio, then yes the designer can realize tremendous increases in range, doubling is realistic with the same payload as the max range under kerosene.
#4 How do we plan on actually building a jet, is that something only large corporations can do?
Our company is a design and innovation company, led by its founder Christophe Pochari, who is solely credited with reviving and bringing back Daniel Brewer’s work to the mainstream of aerospace propulsion. Our company will use established aerospace manufacturers to carry out the manufacturing and assembly in China and India, Pochari Hydrogen provides only the basic design and idea, albeit a revolutionary and game-changing idea. Our main goal is to promote this technology and idea, and find people with the necessary manufacturing capability.
Computational fluid dynamics is done with Patrick Hanley’s Stallion 3D, Patrick Hanley is a follower of Christophe Pochari on Twitter. Composite fuselage design and fabrication is done in China. Powerplants, small turbofans, are built in house using turbomachinery parts from Shandong Yili Power technology LTD. The turbofan is based off the proven all centrifugal compressor PW100 turboprop architecture, converted to a turbofan.
#5 What are the main differences between hydrogen and jet-fueled aircraft?
The powerplant differences are minimal.
The combustors are slightly different for hydrogen fuel, the principle difference is they are significantly shortened. Nothing in the powerplant itself changes except the fuel delivery system changes. Liquid hydrogen is pumped from the tank with two high-speed centrifugal pump, then the liquid hydrogen flows through the supply line to the engine vaporizing along the way and subsequently raising the gas pressure until reaching 150 psi where it is injected in the combustor. A separation between the low-pressure liquid tank and the higher pressure gaseous hydrogen is required, dual centrifugal pumps provide this separation.
The liquid hydrogen pump is placed right outside the rear of the tank towards the end of the aircraft, the pump is mounted directly to the tank, the second pump adjacent to the first pump, the higher pressure liquid is then routed to the engine in small diameter aluminum piping, serving essentially as a makeshift heat exchanger to vaporize until sufficient pressure is reached. Only a certain margin above the combustion chamber pressure is required, this is in the range of 100-200 psi.
#2 Airframe and aircraft architecture.
The main difference with the airframe and fuselage is the integration of the liquid hydrogen tank. The fuselage is designed with an optimal surface/volume ratio, enabling sufficient volume to store the liquid hydrogen necessary to perform ultra-long-range missions.
The basic aircraft architecture remains identical.
The architecture is a pressurized tubular fuselage with a low wing monoplane configuration with a T-tail with rear-mounted engines. The center of gravity is not altered, in fact the elevator authority is increased due to the longer fuselage. The only possible disadvantage to hydrogen aircraft is reduced agility due to the larger fuselage, which makes the aircraft “fatter” resulting in more drag, which impairs agility, business jets are not fighter jets, smooth flight characteristics are desired, so this is not an issue.
#3 Fuel containment and tank design
Tank design is arguably most critical element of a hydrogen aircraft.
We want to maintain the lowest pressure possible in the tank, to reduce stresses on the tank wall skin, but we also need to achieve sufficiently high pressure to overcome the pressure inside the combustor through vaporizing liquid hydrogen pumped from the tank. To reduce tank wall stress, the fuselage-tank section is pressurized to 11 psi, while maintaining 21 psi in the tank. In the absence of pressurization, significantly more stress is imposed on the thinner less strong aluminum tank wall. By pressurizing the tank-fuselage section, we transfer the majority of the pressure differential stresses to the stronger carbon fiber skin.
The fuselage-tank section is comprised of a 3mm thick outer skin, made of Toray T1100 carbon fiber, a spacing to separate the insulation from the skin and the tank.
The carbon fiber is sheltered from the low-temperature tank and insulation by a layer of air. The monocoque structure comprised of the outer carbon fiber skin and aluminum tank results in an extremely rigid fuselage-tank section.
The tank is fastened to the outer skin with high strength epoxy, no mechanical fasteners are used. Stringers are bonded to the carbon fiber skin, then to the aluminum tanking, forming a fully integral tank structure.
Carbon fiber, although much stronger than aluminum, is not attractive for continuous use at cryogenic temperatures, carbon fiber becomes brittle at low temperature, microcracks can also develop due to the differential in the coefficient of thermal expansion of the individual fibers. In addition, most resins used to bond composites become brittle at low temperature. Thus metal is the most attractive, among the different alloys available, aluminum-lithium provides the highest specific strength, or commonly referred to as strength-weight ratio. Aluminum-lithium is higher even than titanium, the second most attractive option for tank wall material. Aluminum lithium 2195 actually becomes stronger at cryogenic temperatures.
The insulation is placed directly on the outside of the aluminum tank. Vacuum panels insulation, comprised of a membrane wall, used to prevent air from entering the panel, a panel of a rigid, highly-porous material, such as fumed silica, aerogel, perlite or glass fiber, to support the membrane walls against atmospheric pressure once the air is evacuated. These panels manufactured by NanoPore Incorporated, Albuquerque, NM, provide the lowest thermal conductivity with the lowest weight. The thermal conductivity, when accounting for the extremely low surface temperature when the tank is full of liquid hydrogen on the ground, can be as low 0.0025 W/m-K. These vacuum panels provide lower thermal conductivity to mass ratios than S-180 spray-foam insulation. The vacuum panels are specially formed to take the shape of the tank, and fit between the frames/stringers. Foam is sprayed around the seams and inside the frame volume, minimizing thermal bridging.
In summary, the tank is actually very simple and based on mature and proven technology and structural configurations. The insulation is light-weight and provides manageable boil-off when the aircraft is not in flight. The weight of the entire fuselage-tank section weighs 1.18 lbs/ft3. This translates into 2700 lbs for a 4700 kg tank, providing nearly 17 hours of flight time, or 8700 miles. The additional drag (Flat plate drag based solely on wetted area) from the 1200 square foot wetted area is 0.46 lbf/ft2, resulting in 550 lbs of additional thrust required, resulting in a fuel burn of 58 kg/hr, 22% higher than without the hydrogen tank, this reduces the L/D from 17 to 13.2, approximately the same that G. D Brewer found. This calculation is very easy to perform, simply by taking the total zero-lift drag and dividing by the wetted area, then multiplying by the wetted area increase.
main focus is the development of an ultra-long-range light business
jet, but many other types of aircraft would benefit tremendously from
hydrogen propulsion, mainly narrow-body airliners and
In the case of a narrow-body airliner, such as an A319, we could extend the range with an acceptable payload from 3300 miles to over 7600 miles, allowing small narrow-body aircraft to fly much more profitable transpacific routes. This would give airlines the option to purchase a more affordable and smaller aircraft, that can land and operate from smaller airports with lower landing fees. Another benefit of narrow-body aircraft is it’s much easier to fully occupy the aircraft in a shorter period, allowing for higher and more profitable utilization. In summary, this narrow-body would give airlines a viable alternative to wide-bodies for transpacific flights.
Helicopters could be designed to fly longer range offshore oil and gas missions, or fly similar distance with more payload.
The main application of civilian helicopters is off-shore oil/gas, which currently suffers from depressed activity, when this improves, Pochari Hydrogen will begin designing a hydrogen-powered 10,000 lb class rotorcraft for long-range missions. Currently, the longest range civilian rotorcraft is the Leonardo AW139, capable of flying 750 miles with a sufficient payload to carry 15 oil and gas workers, we can improve this to 1400 miles.
The third type of aircraft would be a supersonic business or passenger jet.
This type of aircraft was demonstrated to the most attractive application of liquid hydrogen by Daniel Brewer (1975), but more recent analysis from computational fluid dynamics, and better understanding of wave drag, may result in this not being entirely correct.
The reason is simple, at supersonic speeds, a turbofan engine cannot function, a turbojet or very low-bypass turbofan is required, typically these engines have much higher specific fuel consumption, typically over 1 lb-lbf-hr, instead of 0.70 lb-lbf-hr for subsonic turbofans. As a result, the higher fuel consumption adds up the course of the flight, resulting in the fuel load fraction being much higher, incentivizing to a greater degree the use of a higher energy fuel.
But there’s a caveat, as we previously illustrated, in subsonic flight, the airliner fuselage, 20 feet in diameter, with a wetted area of 9500 square feet, is only subjected to 4400 lbf, but in supersonic flight, this is increased tremendously, to 80,000 lbf (Bjorn, Fehrm, 2018).
The source of drag changes from subsonic to supersonic, skin friction is no longer the dominant form of drag, rather, wave drag appears, in great magnitude. This necessitates a much higher fineness ratio, forcing us to reduce the fuselage diameter, and elongate the fuselage, the goal is minimizing the frontal area as much as possible to minimize wave drag, the theoretically lowest wave drag shape is a Sears/Haack body. The “area rule” “Whitcomb rule” is also critical for minimizing wave drag, but since this forces the designer to reduce the thickness of the fuselage to accommodate the increasing frontal area of the wing, this means our hydrogen tank is forced to be smaller.
In supersonic flight, the ideal fineness ratio is over 20, for subsonic, it’s only 4. (Roskam, Jan, 2017). The low ideal fineness ratio allows for very low surface/volume ratio LH2 tanks, reducing weight and wetted area penalty.
The total drag penalty in supersonic flight is much higher, and not fully compensated by the additional fuel consumption. As a result, supersonic aircraft powered by hydrogen will provide a smaller advantage over kerosene.
The fourth applications is defense-related, mainly long-endurance fixed-wing UAVs, such as Predator drone type aircraft, an increase in the flight-endurance of 100% could be more than attainable. The second defense application would long-range bombers and strategic air-lifters, allowing for more payload and flight endurance in the case of bombers.
These defense aircraft are obviously out of the development scope of small civilian aircraft manufacturers, but nonetheless remains very promising business opportunities. Daniel Brewer (1991) argued liquid hydrogen was extremely promising for military aircraft.
35,000 lb GW multi-purpose ultra-long range light jet with liquid hydrogen propulsion
GW: 35,000 lbs
EW: 19,300 lbs
EW/GW fraction: 55%
Max L/D cruise: 13.2, 22% lower than Jet Fuel equavelant.
Overall length: 76′
Cabin length: 12′
Cabin height: 5′
Cabin volume: 400 ft3
Wing loading: 74 lbs/ft2
Airfoil: Supercritical (NACA)
Useful load: 15,700 lbs
Fuel burn: 263 kg LH2/hr
Cruising altitude: 51,000 feet
LH2 capacity: 4700 kg
LH2 tank weight: 1.2 lbs/ft3: 13,180 lbs system weight total
Range: 17.8 hours, 7800 nmi, 9000 miles
Cruise speed: 440 kts
Additional surface wetted: 1237 ft2, 55% wetted/volume
Drag force FL370: 58 kg/hr (0.46 lbf/ft2/S wt)
Drag force FL450: 47 kg/hr (0.36 lbf/ft2/S wet)
Payload at max range: 2,500 lbs
Passenger capacity: 6
Powerplant: 2x 5500 lbf (take-off) turbofan
Powerplant model: In-house centrifugal compressor single spool, single crystal HP turbine blades (architecture based on PW100 core)
Take-off SFC: 0.407 lb/lbf-hr
Cruise SFC: 0.685 lb/lbf-hr
LH2 Tank material: Aluminum-Lithium 2195
Fuselage material: Toray T1100 Carbon fiber
Tank-fuselage pressurization: 4-7 psi at 51,000 feet.
LH2 tank Insulation: 0.5” 0.0025 W/m-K Nanopore vacuum insulated panels with JFOAM™ S-180 foam filler between frames
Tank boil-off rate on ground: 4.8%/hr
LH2 boil-off on ground: 214 kg/hr
Boil percentage of cruise fuel flow: 55%
Max fuel flow at take-off: 700 kg/hr
Total tank heat flux at ambient temperature: 19,000 BTU/hr
Operating cost: $1600/hr
Runway takeoff distance: 4000 ft
LH2 system weight breakdown in Lbs and percentage
For a 35,000 lb business jet. JET FUEL aircraft L/D: 17 LH2: 13.2. SFC cruise: 0.685 lbs/hr, EW/GW: 55%
Pochari Hydrogen has invented a revolutionary propulsion technology for trucking applications. A zero carbon and zero nitrogen oxide emission powerplant that does not use fuel cells or lithium-ion batteries. This powerplant is called the Pochari closed-cycle hydrogen engine. This closed-cycle power semi-truck will utterly dominate the global trucking industry. The world needs a zero-emission yet affordable powerplant, so far those do not go together: Enter Pochari Hydrogen. More information available here https://pocharihydrogen.com/2019/03/01/closed-cycle-hydrogen-internal-combustion-engine-technology/
Pochari Hydrogen’s CHP701 is the world’s first liquid hydrogen powered turbine helicopter. Development will begin in the early 2020s. Pochari Hydrogen utilizes hydrogen stored in “cryogenic” state in carbon fiber tanks lined with an aluminum liner to minimize permeation. The liquid hydrogen is pumped via a “cryopump” from the liquid tank into a heat exchanger connected to the exhaust pipe from the turboshaft engine. Once the liquid has vaporized it immediately rises in pressure to up to 1000 psi where is it injected into modified combustors designed for hydrogen’s unique combustion characteristics. A small helium tank is used to store sufficient quantities of helium gas that serves as a pressurant. The liquid hydrogen tanks needs to maintain a minimum pressure of approximately 30 psi. Due to the nature of cryogenic systems, a very elaborate insulation system is required to minimize excessive “boil-off”. The insulation used is a state of the art vacuum insulated panel system that is lined around the outside of the tank. The insulation is formed in two large uniform shells that are joined in the middle. The middle seam is sealed with a recessed strip of vacuum panel. The uniform shell design is meant to minimize thermal conductivity by eliminating gaps and seams. The tank is fully “modular” meaning it is detachable and can be easily replaced, refilled and maintained. The modularity also allows for the pilot to release the tank in flight in the case of an emergency event that could lead to an impact violent enough to cause a potential detonation. The tank wall is 0.15″ thick aerospace grade carbon fiber reinforced polymer. The tank is designed as a semi-monocoque structure, providing excellent rigidity. “Bulkheads” or formers are placed every 18″. The tank both suspends from the upper cantilevered structure and bears at the bottom section of the airframe. The tank is attached to the airframe via UHMWPE straps wrapped underneath the insulation. The tank is isolated from the vibrations of the rotorcraft via multiple small air isolation mounts. The tank can be easily released and carried with a special dolly cart. The estimated cost of the modular tanks is $100,000. The tanks have a lifetime of around 4-5 years. A forward facing tank is the ideal configuration to minimize structural weight and to allow clamshell doors in the rear of the aircraft which is highly useful for air medical operations. This unorthodox configuration requires a “virtual” flight control system as the tank is placed directly where the cockpit would be. Since autonomy and remote control appear to be the future, this not a significant issue. Three smaller tanks can be installed externally, under the fuselage, and on both sides similar to auxilary fuel tanks on the UH-60. Pochari Hydrogen has considered this configuration but due to the lower volume/surface ratio (a number very important for cryogenic hydrogen aircraft) is much lower resulting in tanks approximately 30-40% heavier than fuselage mounted tanks. Thus we have concluded this is an unattractive option.
Pochari Technologies is planning to develop fully remote controlled conventional helicopters intended to operate in dangerous and challenging missions .
Pochari Technologies has invented a revolutionary new type of piston engine with hugely improved power density. The engine is a conventional piston engine where a single cylinder serves as two separate combustion chambers. A single piston reciprocates in a two stroke cycle or four cycle providing compression in the opposing chamber each power stroke in opposite chamber for two stroke operation, and every other in four stroke operation. A single cylinder, with the same stroke length as a conventional engine, can provide the equivalent amount of power as two cylinders. By eliminating one set of connecting rods, crankshaft, piston and cylinder we can reduce engine weight significantly. This invention allows for increased volumetric power density, and most importantly, a gravimetric power density increase by almost a factor of 2. This technology will be most attractive for weight sensitive applications, such as aviation. The engine can operate on an Otto cycle, Diesel cycle, or a Pochari cycle (closed cycle hydrogen/oxy combustion. We envision this engine being the most attractive for an Otto cycle, since this engine is most attractive for aviation. The engine will be designed firstly on rich mixture spark ignited hydrogen open cycle operation, for use in Pochari Hydrogen general aviation aircraft. For those interested in licencing, please contact Christophe Pochari at email@example.com.
Pochari hydrogen has invented a revolutionary new type of combustion system. Pochari hydrogen believes the hydrogen compression ignition engine is more than feasible. Despite little active research in this field, due to the overwhelming interest in fuel cells or batteries, previous research has found hydrogen compression ignition to be nearly impossible. A compression ratio of 20:1 provides air temperatures up to 450 Celsius, significantly below the 600 Celsius required for hydrogen. Pochari hydrogen has solved this problem with its closed-cycle system, by using Argon, with the same compression ratio, 750 Celsius, providing a sufficient 150-degree margin above the autoignition temperature of hydrogen without needing to increase the compression ratio, allowing standard diesel engines to operate on hydrogen. Despite the sufficient autoignition temperature, there is still one challenge that remains in the way of hydrogen compression ignition. This challenge is rapid pressure rise due to hydrogen’s 7x higher laminar flame velocity. This can be an advantage, since less heat is lost through the cylinder wall, but it can pose challenges to engine design. Modern diesel engines are designed for 2000 psi peak cylinder pressure, with hydrogen this is significantly increased. Another issue is the very low MIE (minimum ignition energy), hydrogen may combust spontaneously prior to TDC, or even in the intake manifold, resulting in sporadic uncontrolled combustion which may cause serious performance and reliability issues. Pochari Hydrogen’s invention solves this problem altogether. Our engine uses an argon- hydrogen mixture in the intake, during the power stroke, a special injector sprays a specific amount of oxygen to fully combustion the hydrogen stoichiometrically, but injecting oxygen gradually to allow smooth combustion. Until oxygen is injected, no combustion can occur, even above its autoignition temperature, the hydrogen will not combust, due to the absence of an oxidizer. In conclusion, this technology utilizes oxygen to achieve and maintain precise combustion control, allowing for perfect stoichiometric combustion of hydrogen and maintaining just enough oxidizer at any given time to achieve smooth and gradual combustion, avoiding a sudden detonation and resultant surge in cylinder pressure inherent to hydrogen combustion.
Pochari Technologies’ has designed a novel and innovative multistage steam turbine. Pochari Technologies’ multi-spool rankine turbogenerator is designed to allow each individual turbine stage to rotate at its own optimal speed reducing losses from turbulence. On a conventional steam turbine, all stages are connected to the main shaft, forcing each turbine stage to rotate at the exact same speed. By freeing each turbine stage to spin freely at its own optimal speed, isentropic efficiency is increased, mainly resulting from optimizing the velocity differential between the airfoil and fluid thereby reducing turbulence inherent to turbomachinery. Studies show that multi-spool compressors raise efficiency by up to 5%. Much research effort has gone into developing multi-spool compressors for gas turbines, results show considerable increases in efficiency. Therefore we believe this concept can be successfully applied to steam turbogenerator technology. Each turbine wheel is connected to an independent axial flux generator. Each subsequent stage will operate at lower speed, so the generator output will progressively decline, so each generator’s electrical capacity is tailored to the specific speed of each turbine stage. A bulk of the electrical output will come from the initial high-speed turbines.
The world desperately needs a more mobile and versatile type of crane for applications that require significantly greater operating radius, unlimited mobility, greater operating flexibility, quick setup and turn around time, and where ground-based cranes simply cannot perform. Situations where the terrain is unlevel, rugged, rocky and unstable, where road access is poor, or situations that require transportation over rivers, lakes, or even over the ocean. Densely wooded areas where trees prohibit road access, highly confined urban areas fully of obstacles, where narrow access prohibiting driving a large crane in, or situations where there is insufficient time to install a permanent tower crane. Prime applications include pre-fabricated modular construction, installing offshore wind turbines, installing wind turbines in mountainous terrain, moving air conditioning units atop a building, pouring concrete in mountainous regions, transporting an excavator atop a high rise building for demolition, transporting shipping containers from ports, installing solar farms, bridge construction, moving large stones from a quarry, mining operations, offshore oil and gas rig construction, or moving large stationary power generators or transformers from rural areas. The aerial crane shines in virtually any situation where heavy objects, building materials, or construction equipment need to moved fast, and most importantly anywhere regardless of terrain conditions. Currently, conventional helicopters are prohibitively expensive to purchase and operate: Enter the Pochari Aerial crane. Designed as a crane, not a manned helicopter, we bypass all of the costly requirements that make helicopters so expensive. By eliminating the pilot, we can remove the entire cockpit section, and the risk of loss of life. In addition, all of the necessary instruments and flight control systems are replaced with a simple remote-control system. By designing the aerial crane to be moved and transported by truck, instead of ferrying over by flying, we can avoid operating over populated areas, eliminating the need for certification. Once again, the aerial-crane is not an aircraft that is certified by government aviation agencies, rather it’s designed as a highly-mobile job site crane. Its operation is strictly limited to construction and work sites, or any job site for that matter which is only occupied by trained personnel, if any time the aerial-crane is going operate over populated areas, all occupants must be evacuated. No ferrying or flying in the airspace is allowed. By eliminating the need for aviation certification, the cost is reduced by an enormous margin. Certifying a helicopter can cost $200,000,000, a huge investment that needs to be recuperated, by charging a large markup on each aircraft above and beyond the bare manufacturing cost. Only certified suppliers can manufacture parts for a certified aircraft. The aerial crane on the hand has none of these requirements, therefore any machine shop in the world can produce parts, allowing very affordable manufacturing of dynamic components, including the main rotor gearbox, turbomachinery, rotor head, and rotor blades. These components are all very simple, manufacturing can be easily performed by non aerospace specialized companies. Any CNC machine shop in the world can machine a rotor grip or epicyclic gear set, relatively easy to machine components. In addition, certified aircraft of course also have to use certified powerplants. An Arriel 1D1, a commonly used helicopter engine, costs $650,000, over $1000/hp. An equivalent non-certified ground-based turbine generator costs only a fraction of this. To manufacture the equivalent turbine in-house using CNC machined centrifugal impellers, and blisk power turbines, can be performed for less than $50,000 for a 700 hp turboshaft. This price difference may at first glance seem to be hard to believe, but upon closer examination it becomes understandable, by eliminating the extremely high safety and performance standards required for passenger-carrying aircraft, manufacturing costs is dramatically reduced. The aerial crane will be sold for only $1,000,000, only twice the cost of the equivalent capacity tower crane. The capacity of the aerial-crane is 10 tons, or 20,000 lbs, 9000 kg. The range without aerial refueling is 50 miles or one hour of operation. That means our aerial crane can carry 10 tons, over 50 miles! The crane can operate for up to 24 hours at a time with aerial refueling provides by an unmanned ducted fan drone. Conventional cranes are nearly made obsolete in the of the aerial crane.
The aerial crane is transported to the jobsite by a specialized truck which serves as a landing platform. If a road is not located nearby, the crane is set up and flown over a non-populated route to the jobsite. The crane itself cannot land on terrain, the reason is landing gear adds a significant amount of weight, therefore we decided to eliminate all on-board landing gear. The crane is required to land directly on the truck-based platform. Once landed on the truck-based platform, the rotor blades can be removed, allowing the main module (power module), consisting of the powerplant, gearbox, driveshaft and flight control system, to be placed flat down and carried on a flatbed truck. Set-up time is less than an hour.
The powerplant consists of 6x in-house developed turboshafts. The compressor is all centrifugal, to reduce cost, as centrifugal compressors are easily machined by any machine shop with a 5 axis CNC. A centrifugal compressor design is much simpler, eliminating stators. The power turbine is a “Blisk” design cast or machined out of Haynes Hastelloy X. A Blisk design reduces cost and complexity by machining or casting the entire unit in one single component, both blades and disc, eliminating the need to machine individual blades and “firtree” in the disk. The mass flow rate is 3.5 kg/sec. Bearings are standard high-speed oil lubricated roller bearings. The turboshaft is rated for 1000 takeoff-horsepower, and 850 continuous. The turboshaft is multi-fuel capable, with both gaseous and liquid fuel combustors available. In regions where liquid natural gas is readily available for low cost, a gaseous version is available. In regions where liquid fuels are inexpensive, diesel fuel is used since no high-altitude gelling requirements are present. Liquid hydrogen is also an available fuel option. The main rotor gearbox includes a bevel gear for the co-axial rotor drive, and epicyclic gears for reduction. The turboshafts are placed around a 4 stage large epicyclic gearbox, providing 250x reduction from 50,000 rpm down to 200 rpm for the main rotor. The rotor system incorporates Pochari Hydrogen’s innovative independent rotor control, where hydraulic pitch-link actuators provide rotor pitch actuation without a swashplate. Hydraulic fluid is transmitted via slip-ring for the lower rotor, and via an on-board hydraulic pump for the upper rotor. All flight controls are fly-by-wire. Each actuator is independently activated electronically via remote control. The second option, which the design team is considering as a simpler solution, is a conventional swashplate rotor pitch actuator system. The main rotor hub is manufactured from lay-up sheets of 300,000 psi T800 Toray aerospace-grade carbon fiber. The main rotor grips are titanium, as well as main rotor shaft. The gearbox housing is Aluminum 7075. The bevel gear and epicyclic gears are made of 4340 steel. The rotor system is semi-articulating, with elastomeric bearings providing lead-lag and flap. The main rotor blades are made of Toray T800 carbon fiber and Nomex honeycomb, with a stainless steel leading edge and straight non-swept tips to reduce manufacturing cost, the blade root is also a basic straight end instead of a narrower root design typically found in modern helicopter rotor blades. with a weight of 250 lbs each. Assembly and prototype testing is performed in Chennai, India, with certain components coming from all over China. Turbomachinery is manufactured in China by Shandong Yili Power Technology Co Ltd. and Zhenjiang Supersoar Machinery Co Ltd.
Cranes will be available for purchase in early 2022. The purchase price is $990,000 for the turbine version, and $800,000 for the electric version. The hourly operating cost is $720/hr for the turbine version, and $330/hr for the electric version.
Specifications: Unmanned heavy lift mobile aerial crane (non-certified experimental) Use over populated areas is strictly prohibited
Crane is designed solely as a heavy lift machine for construction sites and worksites with only trained personnel present.
Powerplant: Gas turbine or fully electric.
Fully Electric corded version for short radius: 500 feet. The electric powerplant consists of 16x 300 hp axial flux electric motors arranged in a stack of four arranged around an epicyclic gearbox horizontally. Three Aluminum alloy 1350 2000 MCM power cables (weighing 3100 lbs, only half the weight carried by the aerial crane) are carried by an intermediate lifter craft 100 ft above the ground-based power unit, the cable then spans from the lifter craft to the aerial crane up to 500 feet. When more radius is needed, the ground power unit can be moved closer, think of the aerial electric crane as a tower crane on wheels.
A gas turbine-powered version for long working radius, 50 miles, 80 km.
Powerplant specifications for turbine version: 6x 800 shp dual centrifugal compressor dual power turbine reverse flow turboshaft. Turbine inlet temperature: 1560 °F
Combustor: Dual-fuel gaseous-liquid reverse flow
Compression ratio: 14:1
Compressor: Three centrifugal 304 stainless steel
Power turbine: 1x HP, 1x LP Dual 40 blade Blisk Hastelloy X
Specific fuel consumption: 0.55 lbs/shp-hr
Weight: 250 lbs
Shaft ouput speed: 55,000 rpm
Power output: 1000 shp take off, 850 continuous
Fuel consumption at 70% torque: 280 gallons/hr
Fuel consumption at 130% torque: 402 gallons/hr
6x 23″ x 265″ 250 lbs/ea
Gearbox: 250x reduction helical gear epicyclic, helical bevel gear for coaxial.
System weight and capacity:
Gross take-off weight: 33,000 lbs
Unit empty weight with 1-hour fuel: 10,500 lbs
Net lift capacity: 22,500 lbs
Maximum operating altitude without airspace permission: 400 ft
Maximum non-stop endurance: 24 hours.
Maximum travel distance over ocean or non-populated area: 480 miles, 770 km.
Overall unit width and length: 51′
Overall unit height: 190″
Power module dimensions: 35″ width by 68″ height
Power module weight without rotors: 6700 lbs
Rotor drive module dimensions: 88″ width, 130″ length
Power module with drive module separated can be easily transported in a box truck.
Purchase price: $990,000
Hourly operating cost: $750/hr
Pochari Hydrogen’s in-house development 1000 horsepower turboshaft.
World’s first and only closed-cycle pure hydrogen diesel engine technology with NH3 derived on demand H2 production.
Pochari Systems in designing the next generation of diesel propulsion by building on the proven diesel engine and applying innovative solutions to fully eliminate all emissions while simultaneously increasing engine performance and efficiency by a large margin.
The diesel engine has accumulated a rather poor image due to their perceived toxic pollution, primarily particulate matter but also substantial quantities of nitrogen oxides.
Diesel is a combustion cycle, not a fuel per se. The diesel engine can theoretically run on any flammable fuel, provided there is sufficient temperature for autoignition. There is no reason or believe the diesel engine is destined to be polluting if designers and engineers choose to embrace this simple solution.
It so happens hydrogen is an ideal fuel for a compression ignition engine provided these innovative solutions are employed to overcome some inherent technical challenges.
This innovative solution is what we term the closed-cycle, the closed-cycle can be thought of a multi-faceted series of solutions to problems inherent to hydrogen engines.
The closed-cycle solves four major limitations faced by both conventional hydrogen engines and also non-combustion hydrogen systems, mainly PEM fuel cells.
#1 How does it work?
A conventional internal combustion engine which does not consume atmospheric air, thus stores oxygen onboard (for mobile applications) and recycles a working fluid, a non-nitrogen inert gas. The exhaust of a hydrogen engine is nothing but water vapor, no carbon dioxide is produced, therefore there is no need for exhaust, as there is no pressure buildup from carbon dioxide gas being released with the combustion of hydrocarbons. Steam is the only bi-product. Steam is condensed in a specially designed condenser. Hydrogen engines inherently want to operate on a closed cycle, thus, any hydrogen engine designer not running on a closed-cycle is failing to realize a potential 50% increase in efficiency, and not fully exploiting hydrogen’s unique properties to eliminate all pollutants.
The basis of our technology is the conventional two or four stroke diesel engine. Interestingly, the closed-cycle does not benefit at all from the 4-cycle the way conventional atmospheric engines do. As such, our engines will be designed as opposed-piston two stroke, similar to the Junker Jumos or the more recent Archates power. Conventional atmospheric engines need to ingest as much air as possible during each intake stroke, then expel as much exhaust (primarily carbon dioxide gas) as possible during the exhaust stroke. Since there is insufficient time during the end of the power stroke and beginning of compression stroke, efficiency is reduced, due to a shortage of oxygen and excessive concentrations of inert exhaust gas possessing a lower specific heat ratio.
In addition to an efficiency penalty, this two-cycle process results in more incomplete combustion, increasing particulate emissions. This alone has forced the major manufacturer of two-stroke diesel engines to completely abandoned production in the mid-1990s.
Despite these disadvantage, the two-stroke possesses the major advantage of requiring 50% less weight and displacement to achieve the equivalent power output of its 4-stroke contemporary. All the disadvantages of the two-cycle are only present with atmospheric engines.
With the closed-cycle, all of these problems are fully solved.
Theoretically, a closed-cycle engine does not even need an intake valve or an exhaust valve, as the oxygen and hydrogen are directly injected, and the water vapor can be purged with small ports.
When hydrocarbon is combusted, a very large amount of carbon dioxide gas is produced, requiring a high volume exhaust system, either large wall port valves in the case of a two-stroke, or adding two additional strokes to further complete the exhaust and intake process.
In order to increase the power output of a conventional atmospheric engine, a large quantity of oxygen is required, typically provided by a turbocharger for diesel engines. This large intake massflow necessitates large overhead valves. With a closed-cycle, only a method to remove and condense water vapor is required. A conventional wall port valve two-stroke (Detroit diesel architecture) but without overhead intake valves, is all that is required for efficient operation on a closed-cycle. A smaller exhaust and intake port is used to flush out a certain percentage of the water vapor produced each power stroke, freshly separated argon gas is circulated back into the same wall port valves, to replenish the argon in the chamber.
It’s desirable to maintain below a certain level of water vapor concentration in the chamber.
Oxygen is directly injected with the hydrogen at a perfect stoichiometric ratio, this way, no oxygen is present during the compression stroke, allowing only pure argon gas to reach very high temperatures, if oxygen is mixed with the argon, the compression temperature is reduced as function of the lower specific heat ratio of the oxygen. Any unburned hydrogen or oxygen is recirculated to combusted, achieving 100% combustion efficiency.
#2 What are the major major advantages?
The first major advantage is the elimination of the only pollutant produced from hydrogen combustion: NOx. This finally makes hydrogen engines fully clean, as they currently are “quasi” zero-emission, producing no carbon dioxide or monoxide, as hydrogen contains no carbon, but still producing high quantities of nitrogen oxides, especially at stoichiometric air-fuel mixtures. The NOx emissions are especially exacerbated beyond acceptable levels if a diesel cycle is used. NOx emissions cannot be brought to acceptable levels without a very low equivelance ratio Otto cycle, resulting in unacceptably low power density. For a diesel cycle running on a high hydrogen mixture, NOx emissions are as high as 920 ppm (R Kavtaradz 2019). A closed-cycle can be thought of as an extreme form of emission control technology, but with the added benefit of unexpected performance increases to be discussed below. In conventional hydrocarbon engine design, there is strong conflict of interest between power, efficiency, reliability and acceptable emission levels.
The second major advantage is the ability to use pure hydrogen in a diesel cycle. Currently, hydrogen cannot be used in a diesel engine due to the very high auto-ignition temperature, which necessitates a 35:1 compression or 200 °C intake air temperature to achieve sufficient compression temperature for auto-ignition. Neither of these options is feasible. Pilot fuel can be used, but must be a hydrocarbon fuel since a high cetane number is required. The reason we want to use a diesel cycle is due to the great efficiency advantage over the Otto cycle, decreasing operating costs.
A Hydrogen direct injection compression ignition engine with heated intake air (non-closed cycle nitrogen-oxygen) was demonstrated to achieve a tremendous 53% efficiency advantage over diesel fuel using a 10 hp test engine. The diesel engine was 27.9% efficient, vs 42.8% for the same engine with hydrogen injection. The power output of the hydrogen injection version was 15% higher. A hydrogen fuel injector was custom built in place of a swirl-chamber diesel injector. (JMG Antunes, R. Mikalsen, A.P. Roskilly, Newcastle University, International Journal of Hydrogen Energy, 2009). Even better, Homan et al, 1979, found an astounding 60-100% efficiency increase using a large diesel engine (Caterpillar D399, V16, 1200 hp, 64 liter) with glow plugs for ignition assistance. The engine used port injection.
The huge increase in efficiency is mainly a function of the much higher cylinder pressure rise due to hydrogen’s higher flame speed. The cylinder pressure rise is in the order of 2.10x higher using hydrogen fuel over diesel fuel (Homan, Reynolds, De Boer, Mclean, IJHE 1979). Thanks to the faster cylinder pressure rise, more work is accomplished in a much shorter period of time, this results in less heat lost by conduction through the cylinder wall, since there is less time for conduction to occur. Heat loss through the cylinder wall into the coolant was estimated to be 42% of the total energy input for the diesel version, but only 17% for the hydrogen direct injection version. (JMG Antunes, R. Mikalsen, A.P. Roskilly, Newcastle University, International Journal of Hydrogen Energy, 2009). The engine was 10 KW single cylinder indirect injection diesel engine (modified for direct injection H2)l
This data illustrates that hydrogen is a far superior combustion engine fuel, despite “experts” claiming only fuel cells can be used with hydrogen, and that combustion engines are not appropriate. No other fuel available can increase the efficiency of a diesel engine by 53-60% other than hydrogen.
The third major advantage is an across the board increase in efficiency of 25% regardless of whether a spark ignited or diesel engine is used. (P.C.T De Boer, J F. Hulet, International Journal of Hydrogen Energy, 1980). The reason for the increase in efficiency is due to the higher heat of the non-nitrogen gas under the same compression, resulting in higher combustion temperature and greater power produced. With this increase in efficiency, a spark ignited engine can be 45% efficient, vs 35% for conventional Otto cycles. A diesel engine version could be 55%, making hydrogen engines equally efficient as fuel cells, yet at a fraction of the cost.
The fourth major advantage is the ability to use ammonia derived hydrogen. Virtually all hydrogen used for ground-transport will utilize ammonia as a storage mechanism, allowing for the elimination of costly and heavy high-pressure tanks, and the elaborate and very costly infrastructure required for fueling. Using onboard microreactors to convert ammonia back into pure hydrogen, to use in our closed-cycle engine, this allows a hydrogen vehicle to be fueled at home, and drastically reduces the cost of infrastructure conversion to build out a hydrogen mobility world. Ammonia is liquefied at 8-10 bar depending on temperature, and can be stored in plastic tanks. The fueling infrastructure is an order of magnitude less complex and costly than current high-pressure hydrogen systems. Small scale ammonia crackers bases on either micro-reactor technology (MRT) or monolith reactors have been demonstrated to be feasible. (Kordesch, K, Hacker, V 2001, Wang 2009, Lu 2007, Chiuta, S 2015, 2013, Zamfirescu and Dinçer 2011, Sankir, M, 2017). The ammonia cracker Pochari Hydrogen will use is based on monolith microfibrous technology, decreasing volume by a factor of four over packed-bed 2mm pellet backed bed reactors. Microchannel reactors are also an attractive option, as they increase heat transfer rates by a factor of 50-100 over fixed-bed reactors (Chiuta, 2015). Higher heat transfer reduces energy consumption. Ultimately, Pochari Hydrogen will use micro-channel reactor technology combined with micro-fibrous catalysts.
The monolith ammonia cracker used for our example uses ceric oxide as a catalyst promoter, nickel microfibers as the main catalyst, along with aluminum oxide. The micro-fiber reactor operates at 600 degrees Celsius, but only 400 Celsius is sufficient for a 99.10% conversion rate. The energy consumption is 10.5 kw kg-hr, of which represents electrical energy as the reactor was designed with electric heating rods, only heat energy is required, of which a majority can come from the hot exhaust gases from the internal combustion engine (Zamfirescu and Dinçer 2011). The volume for a 20 kg/hr cracker would be only 4.2 cubic feet (Wang, 2009). The weight of the cracker is 23 lbs per kg/hr of hydrogen required. The volume is only 0.21 cubic feet/kg of H2/hr. During operation at higher throttle setting, a fully loaded semi cruising at highway speeds produces after turbo exhaust temperature of 750 C, of which is much higher at the exhaust manifold where the reactor will be located. As a result, almost all the energy supplied to the ammonia reactor is free. During lower throttle operation, a small combustion chamber using hydrogen combusted with oxygen only, preventing NOx formation, can supply high temperature directly to the catalyst bed, around 0.35 kg of H2 is required for 1 kg of H2 disassociated, (1 kg H2 provides 33.3 kw of heat energy, at 95% combustion efficiency, this is reduced to 31.6 kwh, 11 kwh is required for every kg, thus requring 0.35 kg of H2 along with 2.5 kg of O2 for stoichiometric combustion. 55% of the energy consumed by the cracking process is provided by the exhaust gas, this is calculated by estimating the total heat energy provided by the exhaust gas adjusting for the greater exhaust loss portion rather than cylinder wall losses due to hydrogen’s higher LFS over diesel, resulting in a much greater percentage of losses through exhaust rather than coolant.
The oxy-hydrogen combustor chamber is closed-off from gaseous nitrogen produced from ammonia decomposition, preventing any NOx formation. The combustion chamber burn rate varies depending on the availability of exhaust energy, dependent on engine throttle. The oxy-combustion chamber provides very high combustion temperatures directly to the reactor, by burning the hydrogen in a pure oxygen environment. The combustor located in the module of which contains the reactor, which serves as the exhaust manifold, passing the hot exhaust gases through the heat exchanger tubes containing the reactor bed. Our closed-cycle engine, due to utilizing a high-specific heat ratio inert gas, would have significantly hotter exhaust gas than with conventional engines, both since the compression temperature is much, as well the intake temperature, since the exhaust is routed back into the intake, but also since there is no CO2 to absorb heat, and since argon has half the specific heat capacity of air, the result is the exhaust temperature is likely to be 30% higher with a closed-cycle. The peak compression temperature of our engines will reach 950 C, 125% higher than with air.
The nitrogen bi-produced is vented into the atmosphere after separation from the hydrogen, no oxidization occurs. The nitrogen-hydrogen gas, 75% hydrogen by volume, is passed through a PSA system to purify the hydrogen to 99.9% before being combusted in the engine, in order to minimize trace amounts of nitrogen oxidized during combustion.
Storing hydrogen as ammonia is a game changing solution, immediately rendering the entire current hydrogen mobility industry obsolete. The high-pressure tanks, high-pressure fueling stations and PEM fuel cells manufacturers are faced with total obsolescence when closed-cycle ammonia fed hydrogen engines are available. The ammonia cracker can only realistically achieve a certain level of purity, small concentrations of ammonia will remain in the hydrogen, in excess of 500-1000 ppm being typical, increasing with lower temperature. The maximum concentration of Ammonia tolerable by PEM fuel cells is in the order of 2.1 ppb (Gomez, 2018), that is parts per billion, and the ammonia concentration out of the cracker is 500-1000 parts per million, this is in the order of 240,000x more than the maximum purity requirement! this means there is an immense, possibly impossible filtration requirements in order to make PEM fuel cells compatible with ammonia derived hydrogen. If the concentration reaches 100 ppb, the membrane is damaged beyond repair (HMA Hunter, 2016). This 500-1000 ppm concentration of ammonia will cause almost immediate and serious damage and quickly result in the complete malfunction and destruction of the Nafion membrane critical to the operation of PEM fuel cells (FH Garzon, 2009, K Hongsirikarn, 2010). Thus PEM fuel cells cannot practically use hydrogen derived from onboard ammonia crackers without elaborate filtration systems to eliminate traces of undecomposed ammonia. As a result, PEM fuel cells may eventually be made obsolete. Alkaline fuel cells can tolerate ammonia, but have poor longevity and durability, illustrated by complete abandonment of Alkaline fuel cells by the current hydrogen mobility industry. Alkaline cells have a lifetime of 5000 hours only, compared to 10,000 or more for diesel engines. In addition to poor durability and higher cost, fuel cells, both Alkaline and PEM, do not provide anywhere near the level of waste heat to utilize for cracking the ammonia. As a result, much more energy will be required for ammonia decomposition if a fuel cell is to be used instead. An internal combustion engine (especially a closed-cycle) is a perfect match for an ammonia derived hydrogen vehicle. When the consumption of additional hydrogen required for NH3 disassociation is accounted for, the net efficiency of a fuel cell a starting efficiency of 50% (Jiangsu Ice-City Insulation Materials Stock Co. Ltd), the net efficiency is reduced to 31.4% after NH3 cracking, compared to 39% for the closed-cycle with the same starting efficiency of 50%. The Ammonia cracker consumed 11.3 kw/kg-hr of H2 produced, translating into an efficiency of 66%. All Pochari Hydrogen closed-cycle engines will use on-board ammonia crackers, dispensing with liquid or high-pressure. The ammonia cracker requires 10-20 minutes of start-up time before coming operational, reduced by using multiple microreactors. The startup time driving is provided by a small 90 kw Lithium-Titanate battery pack providing 30 minutes of driving or 4.3% of the 2100 kwh of total energy used for full range, our class-8 trucks have a range of 1380 miles, carrying a total of 185 kg of hydrogen as NH3. No high-pressure tanks are used.
The micro onboard NH3 cracker cannot rapidly adjust the hydrogen flowrate unless the cracker is set at its maximum rated ouput, and the NH3 flowrate is simply throttled. The issue with this method is that significant heat energy from the oxy-hydrogen combustor would be wasted, as the cracker would need to be set to the highest power setting at all time, as the driver frequently needs to accelerate rapidly drawing more fuel flow, but on average, the driver will demand less fuel flow than the cracker is set for. If the cracker is set at a lower power output, the hydrogen flowrate is limited, and will prevent the driver from rapidly demanding more power. For the cracker to operate at optimal efficiently, it should be set at a constant temperature and flowrate, as constantly fluctuating the combustor heat output, and subsequently oscillating the catalyst bed temperature will increase energy consumption.
This issue obviously poses a serious limitation for the driver, as a result, Pochari Hydrogen has to search for a solution.
Enter the electric drivetrain.
Often touted as the future of mobility, in reality, the hybrid electric drive train is an old technology which has been widely employed in rail and marine propulsion. The “prime” mover is a diesel engine (closed-cycle H2 CI DI), operating at a constant speed, which improves longevity and increases efficiency, as the engine is able to operate in its optimal BSFC spot in the power curve. The prime mover powers a three phase AC alternator, which is synchronized to the speed of the diesel engine, which provides current to a single or multiple electric motors. A transmission and clutch is not required, as electric motors provide full torque at 0 RPM. Thus the main transmission is eliminated, the electric motors can either be located in place of the main transmission, turning the driveshaft, or directly coupled parallel to the axle, eliminating the rear differential. A mini lithium-titanate battery (4% of the total full range power capacity of vehicle) is continuously charged by the prime-mover, this allows the driver to demand full power from the vehicle at any time, when the battery begins depleting, the prime-mover engine slowly increases in throttle, and recharges the battery. When the depletion rate of the battery decreases with less power demand, the prime mover engine throttle is decreased. This allows for a significant gap in power output to exist between the prime mover, dictated by the NH3 cracker flowrate, and the vehicle power demands at any given time, dictated by driving conditions.
#3 Why can our engine operate on a diesel cycle whereas other hydrogen engines such as Keyou and BeHydro cannot?
Thanks to the closed-cycle, we can use an inert gas (not nitrogen and air) which heats up to a much greater degree under the same compression (called the specific heat ratio) allowing us to attain a temperature sufficient to auto-ignite hydrogen, without requiring a high cetane number hydrocarbon pilot fuel, Dimethyl Ether, Biodiesel B100, or straight diesel fuel can be used, but not in a closed-cycle, as CO2 buildup will be unmanageable. With Argon gas, with an intake temperature of 100 °C, a 17:1 compression ratio results in a temperature of 900 °C, 300 °C over the auto-ignition temperature (Checalc.com, using Peng-Robinson EOS). With a 22:1 CR, the compression temperatures reaches 1045 C, resulting in very short ignition delays. JMG Antunes et al found that under 830 C, the ignition delays is longer with hydrogen than for hydrocarbon fuels, but at or above 830 C, the ignition delay is much shorter. Argon, can be seen as an enabler to hydrogen compression ignition, (Mansor and Shioji 2012). The higher intake temperature is a result of the closed cycle system, which routes the exhaust right back into the intake, instead of cooler ambient intake air in an open-cycle. With an intake air temperature of 70 °C, a compression ratio of 35:1 is required to auto-ignite hydrogen with an oxygen-nitrogen mixture, making hydrogen compression hydrogen engines nearly impossible, limiting hydrogen engines to Otto cycles, which are limited to 35% efficiency.
#4 How is our engine different from existing internal combustion engines?
It is not different at all. The engine can either be spark ignited, or compression ignited, exactly the way current engines reciprocating engines operate. In compression-ignition versions, the fuel (hydrogen) is injected directly like conventional diesel engines, oxygen is mixed with the recycled intake argon at the stoichiometric ratio. In spark-ignited versions, the hydrogen is injected in the intake manifold in the same fashion natural gas engines operate. The engine type can be 4-stroke, 2 stroke, a gas turbine or Wankel. Just about any combustion engine can operate on our closed-cycle. Any combustion cycle, including Brayton, Otto, Diesel, Atkinson, and Rankine (external combustion) can be used.
#5 Since it’s a closed cycle and does not consume atmospheric air, we have to consume oxygen, does this increase the cost? Short answer: On the contrary, it significantly reduces operating costs thanks to higher efficiency.
Oxygen both in high pressure gaseous (890 kg/m3 at 700 bar, 1140 kg/m3 liquid) and liquid state is very dense. 1kg of hydrogen requires 7.4 kg of oxygen for complete combustion, what we call the stoichiometric ratio. For atmospheric air, this ratio is 2.9% hydrogen to atmospheric air by mass. This small ratio is what makes the closed-cycle so attractive, very little oxygen is actually required compared to the engines mass airflow in conventional operation, this is because diesel engines run very lean, low equivalence ratio, to minimum NOx formation. Thus if our engines consumed 11 kg of hydrogen per hour or per 60 miles (based on 5.9 mpg for a typical semi-truck) we only need 80 kg of oxygen. Storing enough oxygen to drive 850 km only requires 580 liters for liquid storage.
The weight of the oxygen storage is also minimal for mobility use. For a hypothetical 9000 lb light-duty truck (Ford F-450) with a 500 miles range, the oxygen tank weighs 240 lbs, plus 440 lbs for the oxygen, representing only 4.5% of the vehicle’s GVWR. Thus, storing liquid oxygen onboard a vehicle, may at first seem almost science-fiction-like, but in reality, is it least of the operators’ worries.
For stationary applications, oxygen can be stored in large spherical liquid tanks or can be piped directly in low-pressure gaseous form. For stationary storage, due to oxygen’s very high density, the “boil-off rate” is minimal, 1.5%/day for a 200L dewar. The liquefaction of oxygen is easily accomplished with low cost commercially available equipment. Due to oxygen having an inversion temperature above ambient, it requires no pre-cooling required with hydrogen liquefaction. Liquefyng oxygen for transportation and storage is not only cost effective, but technically simple, requiring only compressors and expanders, all of which are widely available on Alibaba.com.
The cost of oxygen, either liquid or gaseous is very low due to its abundance. Liquid oxygen costs only $0.05/kg in India (Metals and Minerals Trading Corporation of India, 2016) and $0.09/kg in the U.S. (Matheson Tri-Gas, 2017) Resulting in hourly operating costs of $4 and $7.3 respectively for a 300 hp engine.
A hypothetical 1000 hp (750 kw) diesel generator with a BSFC of 0.33 lbs/bhp-hr (41% efficiency) would consume 47.6 gallons of diesel fuel per hour, with the efficiency improvements from the closed cycle, this would be reduced to 40 kg of H2 per hour, requiring 254 kg of oxygen, at a cost of $14.8 per hour, contrasted to $140/hr for $3.5/kg clean hydrogen from electrolysis. Netting an electricity cost of $0.020/kwh. In comparison, a spark-ignited non closed cycle engine with a BSFC of 0.4 lbs/bhp-hr (34% efficiency) would consume 66 kg of H2 per hour, costing $231/hr, netting an electricity price of $0.31/kwh. This clearly illustrates that for any application, mobility or stationary power generation, the closed-cycle is much more cost effective and would yield operators much greater profits. A fuel cell powerplant, averaging over $2000-5000/kw, is not even comparable, as the acquisition cost for a 750 kw unit would be astronomical, totaling over a million and half dollars.
#6 What are the necessary modifications required to convert an engine to closed-cycle?
That depends on whether a spark-ignited or diesel engine is used. For spark ignition, the first modification required is a compression ratio reduction to 5.5:1 for a typical 11:1 compression ratio gasoline or natural gas engine. Reducing the compression ratio simply involves raising the cylinder head a small distance, this can be done by installing a thicker metal cylinder head gasket. The increase in height is around 0.2”. The fuel system on the conventional spark-ignited engine is removed and replaced with low-pressure constant flow hydrogen injection in the intake manifold. No specialized injectors are needed, simply a constant flow of low-pressure hydrogen is fed into the intake manifold.
Regardless of whether diesel or spark-ignited, proper crankcase ventilation is required for any hydrogen engine to ensure no build-up of hydrogen in the crankcase occurs. This can be accomplished by inserting a small vent in the crankcase, equipped with a hydrogen sensor, to monitor the potential accumulation of concentration of unburned gas.
The second modifications after the fuel system is the exhaust system. The exhaust tubing, condenser, and dual argon-CO2 vent tanks are filled up with argon, which is continuously recycled. Two tanks are used in order to maintain a 15% CO2 to argon ratio, as a small amount of lube-oil is burned, releasing CO2, the dual tanks are continuously switches, when one tank reaches 15% CO2 concentration, it is emptied and refilled with pure argon. More on this can be found on question #9.
The water vapor condenser is installed just before the intake, so that the exhaust gases have had sufficient time to cool down to the 100 °C intake temperature, allowing a certain percentage of the water vapor to have condensed. For vehicle use. The liquid oxygen is used to accelerate the condensing of the water vapor, for stationary applications, where space is not as constrained, a larger condenser is used, eliminating the need for cooling.
The third modification required is the installation of an oxygen regulator. The oxygen regulator is located on the oxygen intake hose, which can be a low-pressure flexible line, connected to a high-pressure storage vessel for vehicle use, or a low-pressure supply line for stationary applications. The oxygen regulator is calibrated to provide a 7.4:1 ratio of oxygen to hydrogen by mass at any given engine speed. The regulator can be electronic or mechanical.
The fourth modification is the installation of two hydrogen sensors. A hydrogen sensor is installed in the crankcase, to warn the operator if any gaseous hydrogen has accumulated in the crankcase due to a blockage in the venting system.
The second hydrogen sensor is installed in the exhaust line, to measure combustion efficiency. If a high concentration of unburned hydrogen is observed, the oxygen regulator could be malfunctioning and the engine could be running too rich, the oxygen regulator is recalibrated to increase oxygen flow, until the unburned hydrogen concentration is reduced to normal levels.
For a diesel cycle, the modifications required are somewhat more elaborate but isolated to the injection system. In a diesel engine, precise injection of the fuel is critical for smooth and reliable operation. Intake injection is possible, through what is called homogeneous charge compression ignition (HCCI). Fuel is mixed with the intake air, in this case hydrogen, oxygen and argon, then compressed until auto-ignition. This cycle is highly efficient, one study shows up to 12% more efficient than direct injection. (JMG Antunes, R. Mikalsen, A.P. Roskilly, Newcastle University, International journal of hydrogen energy, 2008). The main issue with HCCI is timing difficulty which results in rough and sporadic operation. Currently, no HCCI engine is in operation. Pochari Hydrogen strongly believes direct injection is the best option.
To perform the closed-cycle conversion for diesel, the first step is to remove the fuel injection system. The unit injectors, injection pump, fuel lines and ECM are removed. Newly built hydrogen injectors designed to fit in the same slot are installed. A new ECM is designed for injection timing, and in some cases, a mechanical timing system could be used. Modern diesel injection systems are designed primarily to minimize particulate emissions. Multiple injection cycles per stroke are common, very high pressure is used to atomize the fuel as much as possible to ensure complete combustion. All of this requires precise electronic timing. A large portion of the modern electronic diesel injection system is solely designed for emission requirements, not for performance or efficiency. With a closed cycle hydrogen engines, all current efforts to minimize emissions, often at the expense of performance, can be completely eliminated, freeing the designer to focus solely on performance and efficiency. This should not be understated, as basically all constraints of the diesel engine result from emission limits, with the closed-cycle, we’re liberated completely to design the world’s most powerful and efficient engine, no compromises are made whatsoever.
Two types of hydrogen injectors are available.
A “common rail” version where the hydrogen line is pressurized to the final injection pressure, the injector essentially serves only as a valve, to spray a certain amount of already high pressure gas in the chamber. This type of injector does not incorporate a plunger used to pressurize the fuel just prior to injection. Hydrogen injection pressurization is required due to the very high cylinder pressure found in diesel engines, up to 2000 psi, thus 3000 psi is required for a sufficient margin.
This type is most attractive where high-pressure hydrogen gas is available, such as a vehicle which uses high-pressure or liquid tanks.
For stationary engines, which may run off low-pressure gas, a different type of injection system can be used. This system works whereby the low-pressure gas is fed to the injector, and a plunger pressurizes the gas to around 3000 psi, 1000 psi above peak cylinder pressure. This type of injector is more complicated, but is more attractive for stationary engines that that run off low-pressure hydrogen as it eliminates the requirement of having a micro hydrogen compressor on the engine.
If the first injection system is used where high-pressure gas is unavailable, an on-board compressor is required to pressurize the hydrogen to 3000 psi, serving essentially as a gaseous injection pump.
Regardless of the type of injector chosen, the injectors need to be custom made for the particular engine converted, as no manufacturer currently offers hydrogen injectors for sale. The existing injector profile area can be copied to design the new injector, so the newly built hydrogen injector fits in the existing slot and hole in the cylinder head, eliminating the need to make modifications to the cylinder head, which is inadvisable.
Three types of injectors are available
#1 Piezoelectric crystal actuation
#2 Electromagnetic solenoid actuation
#3 Hydraulic, mechanical or electronic actuation.
The hydrogen injectors do not greatly differ from a conventional liquid fuel injector. No fuel atomization is required, eliminating the need for extremely high operating pressures commonly found in modern diesel engines, this reduces the design requirements on the injector.
A few challenges arise with hydrogen injection.
The first issue is embrittlement of many metals caused by contact with high-pressure gaseous hydrogen. Stainless steel, carbon steel and titanium are susceptible to embrittlement among other, aluminum alloys appear to be quite resistant to embrittlement. To minimize embrittlement, the inside of the injector can be coated with a liner made of high-density ceramic or epoxy, eliminating contact between the gas and the metal.
The second potential issue is the lack of lubricity with a gaseous fuel, but this has not proven to be an issue as many natural gas injectors have been successfully implemented and have proven to be reliable.
In summary, hydrogen injectors are not a major technical challenge compared to liquid fuel injectors, and do not differ greatly from existing natural gas injectors, with the exception of requiring special attention to embrittlement.
Pochari Hydrogen is currently designing a hydraulic, mechanically actuated unit injector. This injector is based on proven Caterpillar hydraulic electronic unit injector (HEUI) technology.
#7 Why use this cycle over conventional spark-ignited hydrogen engines?
Previous experiments with spark-ignited hydrogen engines have not shown promising results for one single reason. Hydrogen is very attractive as a means to reduce emissions, but in the absence of a closed-cycle, high amounts of nitrogen oxides are formed due to hydrogen’s high combustion temperature. Nitrous Oxide, one of the seven oxides of nitrogen, is an extremely potent GHS.
Nitrogen oxidization is a function of combustion temperature and dwell time, essentially how long the combustion occurs. The formation of NOx increase dramatically above 2500 F, peak flame temperature in diesel combustion can reach 4000 F, resulting in very high NOx formation, up to 1000 PPM. Thus any attempt to design a dual-fuel hydrogen-diesel engine such as BeHydro will be a failure. In the case of hydrogen, dwell time is reduced due to much higher flame speed (7-8 higher laminar flame speed). In the case of combustion temperature, hydrogen tends to burn hotter than liquid hydrocarbon fuels, which results in more NOx formation. As a result, hydrogen engines which run at a stoichiometric ratio, 2.9% hydrogen to air by mass, emit excessively high NOx emissions, defeating the purpose of using hydrogen in the first place. As a result, hydrogen engine designers typically run the engine at a 0.5 Equievelant ratio, or twice the amount of air than stoichiometric. This leads to a drastic reduction in power output, around 50% less power is developed. An example of this is the MAN hydrogen engine developed for buses in 2006. The engine was a spark-ignited,12:1 compression ratio, direct injection, but only produced 270 hp at 2200 rpm with 13 liters. The port injection version of this engine only developed 200 hp! This is about half the power produced by modern diesel engines of similar displacement. As a result, a customer that requires a 500 hp engine, be it for a truck or generator, would need 26 liters, doubling the weight and volume of the engine and doubling the acquisition and maintenance cost. The other obvious reason aside from the reduction in power density is the fact that currently, hydrogen cannot be used in diesel engines, limiting hydrogen to 35% efficient Otto cycle engines. In summary, conventional spark-ignited lean-burn hydrogen engines are very unattractive compared to conventional hydrocarbon engines, and completely uncompetitive and obsolete when a closed-cycle is available.
#8 Why hasn’t it been done before?
Mainly because all the research and interested is focused on batteries, and if there is any interest in hydrogen, it’s almost invariably focused on fuel cells. As a result, the easiest and simplest solution was ignored. Apart from us, no one aside from Keyou Gmbh and more recently a newly formed company BeHydro, is focusing on hydrogen engines, and no one in the world yet is working on closed-cycle direct injection compression ignition hydrogen engines. We encourage engineers, designers and inventors to build this technology as soon as possible, so we have made it open source.
The main applications for the closed-cycle is for mobility, mainly cars, light-duty trucks, heavy-duty trucks, marine, freight trains and also for non-mobilty, mainly decentralized power generation.
#9 Is lube-oil combustion and subsequent CO2 buildup in the closed-cycle going to be an issue?
Not at all. Modern diesel engines consume between 0.2-0.8 grams of lube oil per Kwh. This means if we have a 100 kw engine or 134 hp, we consume 0.176 lbs of lube oil/hr, that equates to 0.025 gal/hr, which produces 23.62 lbs CO2 per gallon (EIA), equating to 0.6 lbs CO2/hr, resulting in a volume of 3.35 ft3 per hour (CO2 density at 30 PSI and 100 °C is 2.87 kg/m3. The CO2 argon mixture is allowed to build up to 15% CO2 concenteation, then vented into the atmosphere and switched to a secondary tank of pure argon, once the secondary tank again reaches 15% CO2, the tank is switched back, and this cycle is repeated every 30 minutes, maintaining a 15% CO2 concentration maximum, with an average of much less. The argon tanks are sized to provide this ratio maximum, and switched every 30 minutes. Argon consumption per hour is 1.6 kg, at a cost of $0.11/kg for liquid argon (Metals and Minerals Trading Corporation of India, 2016) resulting in $0.18/hr cost). The argon density at 30 psi and 100 °C is 2.57 kg/m3.
Thus claims that the closed-cycle “cannot work” due to CO2 buildup from lube-oil consumption are incorrect. P.C.T De Boer, the first person to experiment with a closed-cycle hydrogen engine, used the same solution for dealing with CO2 buildup. A small 1 cubic foot (28 liter) tank at 35 mpa, will store enough argon for 8 hours of driving. Thus argon consumption, or CO2 build-up, is a non-issue.
#10 What are the advantages of NH3 storage over high-pressure hydrogen?
Virtually all attention paid to alternative low emission mobility today is focused on either fully electric vehicles, where all the energy stored in heavy and slowly rechargeable batteries. If one mentions hydrogen, we immediately think of ultra-high pressure composite hydrogen vessels to power proton exchange membrane fuel cells. These two technologies both face major technical and economic limitations that hinder future large scale deployment. The technical limitation face by lithium-ion batteries is great in scope, and will require a seperate detailed analysis.
Since our focus in on hydrogen mobility, we will spend most of our time analyzing current hydrogen mobility systems.
The major limitation faced by hydrogen mobility is storage, both onboard the vehicle and during stationary storage for distribution.
The current industry almost exclusively uses carbon-fiber and aluminum lined composite cylinders. These cylinders are very heavy, weighing around 0.46 kg/liter of water capacity, and cost over $50/liter. The major limitation of these systems is primarily low market competitiveness, stemming from high manufacturing costs.
In order to store enough hydrogen at 350 bar for 1380 miles of range, we would need over $330,000 worth of cylinders.
The cost of these vessels is in the order of $50 per liter (Liaoning Alsafe Technology Co), whereas liquid oxygen dewars with a very low 1.5% boil-off rate cost only $6 per liter (Shijiazhuang Minerals Equipment Co).
This is mainly due to the fact that although liquid dewars must withstand moderately high pressures to ensure a minimum safety factor in the event of a high rate of evaporation, the pressure requirements are manageable with conventional engineering materials, mainly stainless steel utilizing vacuum flask insulation technology.
In contrast, composite cylinders must not only withstand immense pressure, in the order of 350 bar, the cylinders must also possess sufficient impact resistance, of which carbon fiber performs very poorly due to its brittle nature.
The safety and certifications requirements for oxygen cylinders are high, but much easier to comply with due to the absence of any flammability risks. In the event of an impact, liquid oxygen will simply vaporize in the event of an impact. Although oxygen is not flammable, it does serve as an oxidizer, and will increase combustion intensity if in direct contact with a flame or source of combustion. In our vehicles, there is virtually no storage of gaseous hydrogen on board, only a small amount is present at any given time in the fuel lines coming out of the NH3 cracker, this amount of hydrogen poses a very small explosive risk compared to the entire hydrogen capacity stored onboard. Due to these reasons, the cost of manufacturing high-pressure hydrogen tanks is very high, resulting in a total cost of $330,000 for total tank capacity enough for a class-8 semi-truck with 1400 miles of range, or roughly 180 kg. The comparable cost of liquid oxygen vessels is only $7000-8000.
The cost of liquid NH3 tanks is minimal.
The NH3 tanks are 0.25″ thick aluminum or stainless steel, weighing only 0.10 kg/L. The tank is designed with a burst pressure of 350 psi, or a safety factor of 2x. The pressure of liquid NH3 is 8-10 bar depending on temperature. No insulation is needed, nor are extremely thick tank walls.
In addition to the high cost of high-pressure hydrogen storage systems is the inferior volumetric density compared to the NH3 system. The volumetric density of the NH3 system is twice that of 350 bar system, taking up more precious volume on the vehicle. This translates into a savings of 100 cubic feet using an NH3 system for a class-8 truck with 1380 miles of range. The volumetric density advantage is due to the use of NH3 as a hydrogen carrier, increasing volumetric density by a factor of 3.9x over 350 bar composite tanks, also translating into tremendous tank weight savings, as NH3 is stored under moderate pressure (8-10 bar) allowing for thin-wall aluminum or stainless steel tanks. NH3 tanks would way 0.10 kg/L, vs 0.5 kg/L for 350 bar.
The limitations of the high-pressure system cannot be isolated to onboard storage
Another major limitation, and arguably the biggest issue so far is found in the transportation, distribution, and compression of gaseous hydrogen. Compressing gaseous hydrogen to 350 or even in some cases 700 bar, is an immensely capital intensive and costly process. The energy consumption is in the order of 3kw/kg to 5000 psi.
The cost of a 7,000 kg/year capacity 300 bar two-stage diaphragm compressor is in the order of $20,000 (Shanghai Davey Machinery Co Ltd).
Reciprocating piston air compressors last on average 10,000 hours before needing major overhaul. A diaphragm compressor uses the diaphragm to protect the metal components from toxic gases through the use of a flexible membrane design to resist damage by toxic gas.
This is especially important for compressing hydrogen, as hydrogen can cause serious embrittlement damage to carbon steels, stainless steel, especially martensitic, Inconel and Titanium. Among the commonly used engineering metals, only aluminum alloys is resistant to hydrogen embrittlement, but aluminum is not suitable due to the high temperature from compressing a moderate heat ratio gas such as hydrogen. Without the diaphragm, the compressor piston and cylinder and cylinder walls of a traditional piston compressor would become badly embrittled and require frequently overhaul. Assuming 10,000 hours for a conventional compressor, we can optimistically assume a diaphragm compressor would last approximately 1.5x longer before overhaul. We assume an overhaul cost of 100% of the purchase price due to the expensive nature of hydrogen diaphragm compressors due to the stringent engineering and manufacturing requirements inherent to systems dealing with flammable gas in closed proximity to urban areas.
Thus, our levelized cost of hydrogen to 5000 psi is $1.62/kg for the first 15,000 hours. The required capital expenditure for a 100 kg/hr fueling station would total $2,400,000 for the compressors alone, not including the elaborate fueling nozzles, of which accurate market prices are not available. Hydrogen fueling nozzles are designed to withstand immense pressure, as a result, leakage is a major issue, posing serious safety hazards to personnel, as a result, the nozzle needs to be perfectly hermetic, causing incredible engineering difficulties, resulting in very high manufacturing cost and short lifecycles especially due to heavy usage by untrained persons.
Hydrogen compressors are already produced in large volume for industrial applications, thus, accurate market prices are available on industrial e-commerce websites such as Alibaba.com, this allowes to reasonable accurately predict the cost of establishing a large scale hydrogen mobility economy.
The equivalent NH3 fueling system would as simple as a large tanker trailer, with flexible composite hoses connected to simple liquid fueling nozzles. The NH3 fueling station could be as cheap as $20,000 for 100kg/day, the price of a 10,000-gallon tanker trailer, including the hose and nozzle system.
With this information in mind, the total cost to install enough fueling stations to serve the entire U.S semi-truck fleet would total $10.5 billion, an equivalent and even further decentralized NH3 system could be built for a tiny fraction.
This number is reached assuming a U.S semi-truck fleet of 2 million operating 10 hours per day, consuming an average of 8 kg of hydrogen per hour traveling at 60 miles per hour. This does not account for the geographic distribution of the fueling stations, and includes only the cost of the compressors, the main component of the fuel station, as high-pressure hydrogen cannot be feasibly transported, this means there must be viable method to transport gaseous hydrogen from production facilities, which through the necessity of requiring low-cost electricity, are often located substantial distances from major urban centers where most consumption occurs. Production through electrolysis requires electricity below $3 cents/kwh to be competitive with hydrocarbon distillates which average under $3/gal.
$3 cents/kwh can be provided by hydropower, geothermal or wind, but preferably nuclear, as nuclear has tremendous scalability potential and can bypass the requirements to transport the gas long distances, small modular reactors are ideal for localized production.
In the absence of localized production capacity sufficient to meet large urban demand, large scale distribution networks must be constructed. Tube trailers suffer from very high transportation costs due to minuscule capacity. Existing natural gas pipelines are the only viable option available, but require elaborate retrofitting, as hydrogen permeates through most surfaces designed for the much larger methane molecule. Hydrogen permeation through conventional pipelines requires expensive retrofitting, which could severely hinder the large scale conversion of natural gas pipelines.
Pochari Systems completely bypasses these virtually insurmountable transportation difficulties of gaseous hydrogen since NH3 is quite dense (113 kg equivalent hydrogen density) which allows for cost-effective long-distance truck transport without the high-boil-off losses and high cost of cryogenic equipment of liquid transport.
To summarize, the major advantage of NH3 over 350 bar compressed storage is as follows
#1 Increased volumetric density by a factor of 2x
#2 An order of magnitude reduction in infrastructure cost to accommodate a large fleet of zero-emission hydrogen vehicles.
#3 Ability to easily refuel the vehicle at home with minimal equipment.
#4 Increased safety from completely eliminating onboard storage of gaseous hydrogen.
#5 Reduced acquisition cost by a factor of 4.4x over a 350 bar composite system
#11 Our engine is dual fuel, how is that important over hydrogen-only mobility systems?
Pochari Systems strongly believes a versatile, cost-competitive, retrofittable, and multi-fuel low emission powerplant is critical to attaining large scale market penetration. Current electric or hydrogen only systems become inoperable in rural regions where fueling infrastructure is scarce, in the case of hydrogen, virtually nonexistent. Thus, a multi-fuel powerplant, that still remains capable of full zero-emission operation, but can switch to using a widely available fuel, will be in great demand, only our technology can provide this, no other fully zero emission system can simultaneously switch to conventional operation.
The important of multi-fuel capability should not be underestimated, as it will take a large investment and a long period of time for a large scale hydrogen (In our case NH3) fueling infrastructure to be fully established.
During this time, having the versatility of being able to quickly switch to diesel fuel operation is critical to high-utilization and profitable operation, of which is demanded by commercial operators.
The vehicle may be eventually exported to less developed countries, if the vehicle can only operate on hydrogen, this lowers the vehicle’s market value in regions with undeveloped hydrogen infrastructure.
Pochari Systems’ hydrogen diesel engines can be switched to diesel fuel operation in less than 5 minutes. The closed-cycle system is opened to the atmosphere, the oxygen intake is closed, and the intake system is open for consuming atmospheric air, using a conventional turbocharger.
The hydrogen injectors are switched to diesel fuel spray mode, as the injectors are developed from the start with dual fuel nozzles, the middle nozzle is both hydrogen and oxygen, and the outer nozzle is liquid fuel. A conventional diesel injection pump is activated, and diesel operation can begin. The entire process can take less than 5 minutes.
This unprecedented versatility and convenience should not be understated. Proponents of low emission mobility often underestimated the sheer time it will take for low emission mobility to make significant inroads in the highly competitive commercial vehicle market. Until the time arrives when a large number of vehicles are operating, thus a widely distributed network of fueling infrastructure is available, dual fuel capability is a necessity to maintain profitable operation, especially in large geographical regions such as the U.S and China and India, the largest markets for commercial vehicles. These countries, due to their sheer size, will prove more difficult in building out fueling infrastructure. Semi-trucks may operate very long distances at a time, more than a thousand miles, this requires the ability to fuel up at existing fuel stations if necessary.
A great benefit of the dual-fuel system is the ability to use hydrogen mode (closed-cycle) in urban areas where pollution from diesel particulate matter is of greater concern.
When the vehicle shifts operation to more rural more sparsely populated areas, diesel fuel operation can commence, as there less concerns with pollution. This scenario can be envision with long distance semi-trucks traveling long distances between major cities, where a majority of their time is spent in rural areas, but at the end of the trip, considerable time is spent loitering in large urban areas, delivering the freight to distribution centers or retailers.
This dual-fuel capability will be one of the strongest selling points of the closed-cycle after NH3 fuel capability over a conventional hydrogen mobility system, comprised of PEM fuel cells and high-pressure tanks. The NH3 tanks an serve as diesel fuel tanks if needed.
The oxygen tank can be simply left on the vehicle and emptied when in diesel operation.
The oxygen tank can also be used to store diesel fuel.
Closed cycle working principle
Closed-cycle engine illustration
Piezoelectric medium pressure inlet hydrogen direct injector
Existing natural gas injector architecture, can be converted to hydrogen
Direct hydrogen injection
A diesel engine for use with a closed-cycle drive-train.
Pochari Technologies’ has invented a new type of rotorcraft rotorhead in early 2017. This new concept has removed the traditional swashplate-pitch link configuration and replaced it with an innovative direct electronic actuation provided by high durability dual electronic actuators. The rational behind the invention is provided by two major benefits. #1: The elimination the swashplate which uses large bearings that wear out fast and require frequent overhaul. #2 The ability to change the pitch of each rotor independently of each other, reducing noise and vibration.