Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

On the road to ANG vehicles

28.10.2015

Berkeley Lab researchers find a better way to store natural gas as a transportation fuel

With new makes of all-electric and hybrid automobiles seeming to emerge as fast as the colors of fall, it is easy to overlook another alternative to gasoline engines that could prove to be a major player in reduced-carbon transportation - cars powered by natural gas.


The cobalt-bdp MOF features flexible square-shaped pores that expand under pressure to adsorb increasing amounts of methane gas.

Credit: Jeff Long, Berkeley Lab

Natural gas, which consists primarily of methane (CH4) is an abundant, cheaper and cleaner burning fuel than gasoline, but its low energy density at ambient temperature and pressure has posed a severe challenge for on-board fuel storage in cars. Help may be on the way.

Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a variety of metal-organic frameworks (MOFs) - sponge-like 3D crystals with an extraordinarily large internal surface area - that feature flexible gas-adsorbing pores.

This flexibility gives these MOFs a high capacity for storing methane, which in turn has the potential to help make the driving range of an adsorbed-natural-gas (ANG) car comparable to that of a typical gasoline-powered car.

"Our flexible MOFs can be used to boost the usable capacity of natural gas in a tank, reduce the heating effects associated with filling an ANG tank, and reduce the cooling effects upon discharging the gas from the ANG tank," says Jeffrey Long, a chemist with Berkeley Lab's Materials Sciences Division and the University of California (UC) Berkeley who is leading this research.

"This ability to maximize the deliverable capacity of natural gas while also providing internal heat management during adsorption and desorption demonstrates a new concept in the storage of natural gas that provides a possible path forward for ANG applications where none was envisioned before."

Long is the corresponding author of a Nature paper that describes this work entitled, "Methane storage in flexible metal-organic frameworks with intrinsic thermal management." The lead author is Jarad Mason, a member of Long's research group. (See below for a complete list of co-authors.)

The United States holds a vast amount of proven natural gas reserves - some 360 trillion cubic feet and climbing. While compressed natural gas-fueled vehicles are already on the road, the widespread use of natural gas as a transportation fuel has been hampered by cumbersome and expensive on-board gas storage tanks and the cost of dispensing compressed natural gas to vehicles.

The storage issue is especially keen for light-duty vehicles such as cars, in which the space available for on-board fuel storage is limited. ANG has the potential to store high densities of methane within a porous material at ambient temperature and moderate pressures, but designing such high-capacity systems while still managing the thermal fluctuations associated with adsorbing and desorbing the gas from the adsorbent has proven to be difficult.

The key to the success of the MOFs developed by Long, Mason and their colleagues is a "stepped" adsorption and desorption of methane gas.

"Most porous materials that would be used as adsorbents exhibit classical Langmuir-type isotherm adsorption, where the amount of methane adsorbed increases continuously but with a decreasing slope as the pressure is raised so that, upon discharging the methane down to the minimum delivery pressure, much of it remains in the tank," Long says. "With our flexible MOFs, the adsorption process is stepped because the gas must force its way into the MOF crystal structure, opening and expanding the pores. This means the amount of methane that can be delivered to the engine, i.e., the usable capacity, is higher than for traditional, non-flexible adsorbents."

In addition, Long says, the step in the adsorption isotherm is associated with a structural phase change in the MOF crystal that reduces the amount of heat released upon filling the tank, as well as the amount of cooling that takes place when methane is delivered to accelerate the vehicle.

"Crystallites that experience higher external pressures will have a greater free energy change associated with the phase transition and will open at higher pressures," Long says. "Our results present the prospect of using mechanical pressure, provided, for example, through an elastic bladder, as a means of thermal management in an ANG system based on a flexible adsorbent."

To test their approach, Long and his colleagues used a cobalt-based MOF hybrid that goes by the name "cobalt-bdp" or Co(bdp) for cobalt (benzenedipyrazolate). In its most open form, cobalt-bdp features square-shaped pores that can flex shut like an accordion when the pores are evacuated.

Combined gas adsorption and in situ powder X-ray diffraction experiments performed under various pressures of methane at 25°C (77°F)showed that there is minimal adsorption of methane by the cobalt-bpd MOF at low pressures, then a sharp step upwards at 16 bar, signifying a transition from a collapsed, non-porous structure to an expanded, porous structure. This transition to an expanded phase was reversible. When the methane pressure decreased to between 10 bar and 5 bar, the framework fully converted back to the collapsed phase, pushing out all of the adsorbed methane gas.

Long says that it should be possible to design MOF adsorbents of methane with even stronger gas binding sites and higher-energy phase transitions for next generation ANG vehicles. He and his group are working on this now and are also investigating whether the strategy can be applied to hydrogen, which poses similar storage problems.

Moreover, Long says, "Improved compaction and packing strategies should also allow further reductions to external thermal-management requirements and optimization of the overall natural gas storage-system performance."

###

In addition to Long and Mason, other authors of the Nature paper that describes this study were Julia Oktawiec, Mercedes Taylor, Matthew Hudson, Julien Rodriguez, Jonathan Bachman, Miguel Gonzalez, Antonio Cervellino, Antonietta Guagliardi, Craig Brown, Philip Llewellyn and Norberto Masciocchi.

This research was supported by the DOE's Advanced Research Projects Agency - Energy (ARPA-E). The X-ray characterizations were carried out at synchrotron light sources that included the Advanced Light Source and the Advanced Photon Source, both DOE Office of Science User Facilities.

Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit http://www.lbl.gov.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/

Lynn Yarris | EurekAlert!

Further reports about: methane gas natural gas pressure thermal management vehicles

More articles from Power and Electrical Engineering:

nachricht Linear potentiometer LRW2/3 - Maximum precision with many measuring points
17.05.2017 | WayCon Positionsmesstechnik GmbH

nachricht First flat lens for immersion microscope provides alternative to centuries-old technique
17.05.2017 | Harvard John A. Paulson School of Engineering and Applied Sciences

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

Physicists discover mechanism behind granular capillary effect

24.05.2017 | Physics and Astronomy

Measured for the first time: Direction of light waves changed by quantum effect

24.05.2017 | Physics and Astronomy

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>