Low Liquid Hydrogen Energy Density Presents Gas Tank Challenges

September 25, 2008

Lawrence Livermore National Laboratory has claimed a world record for hydrogen-fueled car endurance. Using a modified Toyota Pruis, researchers drove 1,050 kilometers (about 653 miles) on 150 liters (about 40 gallons) of liquid hydrogen. That’s 105 km/kilogram on a per-mass basis or 7 km/liter (16.3 miles/gallon) on a per-volume basis. This feat is reported in “H₂ Going the Distance” from ASME’s Mechanical Engineering Magazine and is detailed in “Setting a World Driving Record With Hydrogen” from Science and Technology Review (S&TR).

Not surprisingly, on a per-volume basis, the Livermore numbers come out low compared to gasoline-fired automobiles. According to fueleconomy.gov, the 2008 Prius gets over 45 miles/gallon of gasoline on the highway. The number disparity becomes clearer when comparing the energy density of gasoline (922 BTU/ft³) to liquid hydrogen (270 BTU/ft³). To put the Lawrence Livermore accomplishment in perspective, if their Prius were running on a fuel with the same energy volume density as gasoline, it would have gone over 3.4 times farther, topping 55.6 miles per gallon. So, compared against the 45 mpg rating of an assembly line Prius, the Livermore hybrid is an overachiever.

Despite hydrogen being among the most energetic fuels on a per-mass basis, liquid hydrogen contains only about 29% of the energy on a per-volume basis as gasoline. So, while hydrogen fuel weighs less than tank gasoline with the same total energy, it takes a much larger volume to store. Unfortunately volume is at a premium in today’s small, efficiency-focused automobiles.

Another major liquid hydrogen drawback is the energy required to liquefy it (~ 30 percent of the energy content of the hydrogen molecule, according to S&TR). Moreover, to maintain its liquid state, hydrogen must be vented to remove latent heat and keep the tank from an overpressure explosion. So, liquid hydrogen vehicles “burn” fuel even when sitting parked and off in a driveway. While insulation can be added surrounding the fuel tank to reduce fuel bleed off, insulation eats up precious volume.

Despite these challenges, the Livermore team has made some impressive advances in liquid hydrogen fuel tank technology. Their pressure vessel is 47 inches (120 cm) long and 23 inches (58 cm) in diameter. It is smaller than previous tanks and yet stores more hydrogen due to its design: a carbon-fiber-coated aluminum vessel holds pressure and is surrounded by a vacuum space filled with reflective plastic.

Hydrogen storage technology still requires a long evolution to become commercially viable for automobiles, but the Lawrence Livermore team has provided a glimpse at a possible hydrogen-fired transportation future.

Posted by Matthew Traum on September 25, 2008 | Comments (3)

October 29, 2009

In response to: Low Liquid Hydrogen Energy Density Presents Gas Tank Challenges
Info commented:

THERMOVOLTAIK
STROM AUS WÄRME
Thermovoltaik, die umweltfreundliche Technologie
Add-Thermogeneratoren für die Stromversorgung sind effizient mit kompakt geballter Energie auf kleinem Volumen. Mit einem Wirkungsgrad von 48% ist die Umsetzung von Wärme in elektrische Energie sehr kostengünstig. Zusätzlich wird durch die gespeicherte Wärme des Generators nur die Menge an Kraftstoff nachgeführt, die ein gut isoliertes Generatorgehäuse als Wärmeverlust an die Umgebung abgibt.
Die Thermovoltaik ist das Arbeitsgebiet der Physik, das sich mit der Umwandlung von Wärmeenergie in elektrische Energie befasst. Wenn zwei unterschiedliche Metalle zusammen kontaktiert und erhitzt werden, entsteht eine elektrische Spannung mit relativ hohen Stromwerten.
Ein Add-Thermogenerator besteht aus mehreren in Reihe als Dünnfilmschichten flächig kontaktierten Thermozellen und bildet einen Säulenblock. Eine Thermozelle ist aus mehreren Dünnfilmschichten unterschiedlicher Materialien gefertigt. Wird einem Thermosäuleblock Wärme zugeführt, ist durch Additivmethode die Gesamtspannung die Summe aller einzelnen Thermozellen.
Die Ausgangsleistung ergibt sich aus den Gesamtspannungen, der Grösse der Zellenflächen (Ampere/mm²), sowie der zugeführten Temperaturhöhe. Die elektrische Leistung ist linear proportional zur Generatortemperatur.
Die Wärmeenergiezufuhr ist mit allen Brennstoffarten möglich. Durch Kraft-Wärme-Kopplung, Biogas, Sonneneinstrahlung mit Thermo- und Photovoltaik-Solarzellenkopplung, mit Wasserstoff oder Geothermie.
Durch die kompakte Bauform der Generatoren sind die Anwendungen vielfältig, angefangen vom Herzschrittmacher bis Megawattkraftwerke in der Industrie, Haushalt, Luft-, Raum- oder Seefahrt.
Ein HOCHSTROMWECHSELRICHTER (HSWR), DC/AC-Inverter, wandelt die Gleichspannung der Thermogeneratoren in Wechselstrom um. Dieser HSWR unkonventioneller Bauart ist in Miniaturbauform für Elektronikplatinen oder dimensioniert als Wechselrichter für extrem hohen Stromdurchlass für Megawattleistungen anwendbar und ist für alle Gleichstromquellen geeignet.
Die Additivmethode bietet zudem neue Applikationen in der Sensorentechnik mit höheren Empfindlichkeiten. Generator und Hochstromwechselrichter Patent DE 43 13 827 A1.

Renewable energy, power supply, energy efficiency
Rational energy production Miscellaneous Renewable energy
Thermovoltaik - current from warmth
ADD THERMAL GENERATORS (Addition-thermocouple-voltage) - Decentralized current supply for each household.
Thermovoltaik, the environmentally friendly technology thermo-generators for power supply are efficient compact with energy concentrated in a small volume. With an efficiency of 48% the transformation of heat into electrical energy is very cost-effective.
Additionally, by the stored heat of the generator only the quantity of fuel has to be supplied, a well-isolated generator housing normally delivers as a heat loss to the environment.
The Thermovoltaik is the work area of physics that deals with the conversion of thermal energy into electrical energy. If two different metals are together contacted and heated a voltage electricity with relatively high levels develops.
An Thermo generator consists of several thermo cells in row as laminar contacted thin film coatings forming a pillar block.
A thermo cell is made of several thin film coatings of different materials. If heat is added to a thermo pillar block by the additive method the total voltage the sum of all individual cells.
The output power derives from the general tensions, the size of the cell surfaces (ampere / mm ²),and the temperature the amount supplied.
The electric power is linear proportional to the generator temperature.
The thermal energy supply is compatible with all fuel types. Through power-heat-coupling, biogas, solar radiation with thermal and photovoltaic cells, solar power, hydrogen or geothermal energy.
The compact design of the generators are the diverse applications, ranging from cardiac pacemakers to megawatt power plants in the industry, household, air, sea or space.
A high current inverter, DC / AC inverter converts DC power of the generators in to AC power.
This inverter of unconventional design, is applicable in miniature size for circuit boards for electronics or as inverter for passage of extremly high current for consumer of megawatt power and is applicable to all DC sources.
The additive method also offers new applications in sensor technology with higher sensitivities. High electricity generator and inverter patent DE 43 13 827 A1.
RUDOLF ZOELDE
INNOVATIVE TECHNOLOGIES
03180 Torrevieja, Spain
Tel./Fax: +34 965708941
Mobil +34 600211643
r.zoelde@gmx.eu
rzinnova@gmail.com
www.thermogen.ws24.cc

January 11, 2009

In response to: Low Liquid Hydrogen Energy Density Presents Gas Tank Challenges
Jim Harrison commented:

Excellent practical breakdown and comparison of hydrogen vs gasoline on the basis of energy density by volume. This is what supporters of the Hydrogen economy fail to realize. Hydrogen due to its extremely high energy density by mass seems to be the ultimate energy source, not to mention that it\’s the most abundant element in he universe. HOWEVER, when one considers the production of hydrogen (gas or liquid), storage, compression, reactivity and actual energy density by Volume it becomes much clearer how far away Hydrogen is as an ideal solution. I saw a great comparison in this site - fuelcellsforpower.com/Energy-Density.html

December 16, 2008

In response to: Low Liquid Hydrogen Energy Density Presents Gas Tank Challenges
Mike commented:

Is the aluminum portion of these carbon fiber coated aluminum tanks castings?

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