Critical perspective of using natural gas for vehicles
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Critical perspective of using natural gas for vehicles Critical perspective of using natural gas for vehicles Document Transcript

  • 11 Critical perspective of using natural gas for vehicles Jeremy Horne, Ph.D.Current technology in contextTwo factors have spurred the manufacturer of compressed natural gas (CNG) and liquefiednatural gas (LNG) vehicles – fuel economy and environmental factors. A frequent confusionneeds to be cleared up, the difference between the two forms of the gas. CNG is similar toLPG, in that it too is a fossil fuel and is methane. However, the central difference is that theformer is a highly compressed gas – signified by the “C”, and the latter is an uncompressedvery cold liquid, as the “L” means.When not transported by pipeline, LNG (CH4, or methane), is liquefied as a result of extremecompression. (25 kPa/3.6 psi) to about 1/600 of its natural volume and is stored in thick-walled cylinders at about −162 °C (−260 °F). Contaminants, such as dirt, helium, heavyhydrocarbons, gases with acid, and water are removed in the processing. Odorants are addedto this otherwise odorless, non-toxic, and colorless gas so as to make it detectable [1]. Inthat form it is safe, but when the gas is let out or escapes, it expands and is subject toignition at a 5-15 percent gas-to-air concentration. While the storage cylinders are veryefficiently insulated, there is a tendency for the gas to warm. Temperatures are kept atstorage levels by a small continuous boil-off called “cryogenic boiling”. This purposeful leakingsubtracts heat from the remaining gas, in a similar manner that heat passes from water tocreate steam.Natural gas, of course, is a fossil fuel, a hydrocarbon, subject to the same restraints asregular gasoline, but it does burn much cleaner, hence the original and primary motivation toswitch to it several decades ago. However, it has been found that methane is a greenhousegas, more threatening than carbon dioxide, but is there is less natural gas emitted into theatmosphere at present. On the other hand, natural gas has 20 times the ability to createradiative energy than carbon dioxide. A ton of methane can capture just as much radiation ascarbon dioxide, though it stays in the atmosphere from eight to 40 times shorter [2]. As thepermafrost warms up huge quantities of methane are released, and there is concern that thiscould accelerate global warming. In the event of spillage, natural gas will disperse more 1 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11quickly than gasoline or diesel fuel. LNG comes primarily from Trinidad, Tobago, Algeria,Indonesia, Malaysia, and Qatar. Iran and Russia are potentially large sources, as well. Thecost of LNG plants is high due to lacked of skilled persons construct them, material costs, andgeneral rising prices of petrochemicals.CNG is less than 1% of its original volume in a free state at standard pressure andtemperature and about 42% of the volume occupied by LPG. It is stored in thick walledcylinders or spheres at a pressure of 200–248 bar (2900–3600 psi. Because there is nocryogenic storage as with LPG, CNG costs less to keep on site. An alternative storage methodis adsorbed natural gas (ANG) with pressures around 500 psi, the same as in a natural gaspipeline. The storage tanks contain spongy materials like activated carbon and matrices ofsubstances composed of metals combined with organic materials – organic metal frameworks(MOF). Hence, vehicles can be refueled at sites that don’t need to compress the gas further.As a result of the lower storage pressures, the vehicle tank can be of lighter material, and thewalls do not have to be as thick. The storage containers have thicker walls than those of LPG.It is CNG that is primarily used as a vehicle fuel, there being some 12.6 million worldwide in2010 [3]. Many of these vehicles are bi-fueled, i.e., having the capability of running either ongasoline or CNG. This is to say that the vehicle’s combustive apparatus – injectors, cylinders,emissions control, and so forth are used for either fuel.An advantage of CNG is that it can be mixed with biofuels, such as methane produced fromlandfills and animal waste. Like LNG, CNG does not foul spark plugs as readily andcontaminants don’t befoul crankcase oil. There is 1.6 times the amount of energy in standardgasoline [4]. Like LPG, CNG is in closed spaces, thus doing away with spillage or evaporationas with conventional liquid petrochemicals. However, because of its storage requirements,CNG-powered vehicles need storage space – lots of it – for the tanks, which, at the sametime, are much heavier than conventional tanks used for regular liquid fuels. 2 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11 Typical CNG storage [5]Even with a redesign of the tank, such as flattening it out and storing it on the roof orunderneath the vehicle, the vertical profile of the vehicle, perforce, will be higher. While thegas is the same, methane, CNG is the method of choice for vehicle, as opposed to LNGbecause there are no cryogenic storage requirements for the former.Now, for the vehiclesAlthough many cars and trucks can be and are run on propane (liquefied propane gas, orLPG) our concern is with natural gas. Propane (C3H8) needs be refined from natural gas, as ismethane, but there is less of it than methane. However, the heat content of propane ishigher, about twice that of methane. Yet, there is more natural gas available. LPG is sold ingallons, while CNG is in cubic feet.As to the mechanics, the engine for both conventional liquid fuels, such as gasoline anddiesel, and natural gas is basically the same, with the driver simply being able to turn aswitch to use either the gasoline or natural gas. 3 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11 CNG fueled engine [6]However, you simply can’t fill up the tank with natural gas and drive away. There arenumerous after-market conversion kits to make a vehicle into a duel use one – both forpropane and natural gas. Installation cannot be done on any car (some cars cannotaccommodate the conversion), there should be a qualified technician to do the work (this isnot shade tree work), conversions in the U.S. must be in according with FederalEnvironmental Protection Act (EPA) law, and generally only newer cars can be candidates [7].These are high pressure systems and incompetent installation can result in fatalities.Conversion costs about $3,000 to $5,000, and one must assess the overall savings in priceper gallon and engine maintenance balanced against this [8]. After-market CNG conversion kit [9] 4 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11A drawback to any duel-fueled car – with both natural gas and gasoline is the need for twotanks, one for each fuel. A natural gas tank can add a good 100 pounds, and the space mustbe found to accommodate it, usually in the car’s trunk. As natural gas uses more space thangasoline, the range of such a vehicle is not as great [10]. Especially for smaller cars, wherethere is not as much room for the required tanks for natural gas, the range on all these carsis less, thus requiring more frequent fill-ups and supporting infrastructure to do so. This is tosay that for long trips across country, as in the case of the U.S., there will be need to benatural gas filling stations, many more so than now. Other maintenance factors should beconsidered in a CNG powered car. A sobering cost factor is that one major brand of carrequires the replacement of its low pressure filter every 10,000 miles at a cost of $122.00 –excluding labor! Every 30,000 the high pressure filter needs replacing, and that is about$52.00 [11].Refilling the natural gas part of the car requires an infrastructure, and currently, there aretwo competing ones, the one for natural gas and the other for propane. In essence, there willneed to be three types of refueling options – gasoline, propane, and natural gas. Propanerequires a smaller jet than natural gas, so the two gases are not interchangeable in a vehicle.However, there is “propane air”, which the manufacturer claims is interchangeable withnatural gas. However, this is for non-vehicle use [12].Environmental impact of CNG and LNGEnergy is required in compressing gas, manufacturing cylinders, etc. No energy is needed inextracting it, as it emerges naturally from the ground. Both the facilities required to producegasoline by fractional distillation and those for compressing gas involve energy expenditure,and to assess the overall net energy gain, the complete production cycle needs to beassessed. There is much carbon dioxide emission involved with gas compression andtransport. However, in transport there are fewer LNG carbon dioxide emissions than thosefrom pipelines per kilometer [13].Petroleum is petroleum is petroleum, no matter whether it is LNG, CNG, propane, diesel, orgasoline. Continued extraction of natural gas or petroleum faces increasing demand and thesupply may be a constraint on further development of petroleum and gas powered vehicles, 5 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11despite industry claims to the contrary [14]. The Argonne National Laboratory’s EnergySystems Division states that “…the issue of natural gas availability in the United States is nota near-term concern [15]”, although there are no sources given, other than the U.S. EnergyInformation Administration (U.S. EIA), itself [16], which cites industry sources, such as theNational Petroleum Council and the Potential Gas Committee. The National Petroleum Council,which, it can be expected, is going to paint a rosy picture of the situation [17] as well as thePotential Gas Committee, largely made up of industry representatives [18]. Even theproponents of natural gas are self contradictory in their statements. For example, the websiteNaturalGas.org states, “…no one really knows exactly how much natural gas exists until it isextracted”, but then says, “A common misconception about natural gas is that we are runningout, and quickly. However, this couldnt be further from the truth.” And, then, “…analysts usedifferent methodologies and systems of classification in various estimates.” For sources of itsdata, this website refers to the U.S. EIA [19].“ The point is one must not simply acceptfigures, especially from industry sources that have an “axe to grind”, because they are simplyissued but be critically thoughtful and ask who is using the information and why. Often, thereis a middle ground between opposing sides.Even if there is an ample supply of fossil-based natural gas, how is all this natural gas to beextracted? As each year passes, the amount of effort to extract fossil fuels increases. A majorcontroversy has been with hydraulic fracturing, or “fracking”, a method of extracting naturalgas by injecting and pressuring a fluid through sedimentary layers, causing new rockfractures through which the gas can be released. A common problem is that that injectedsubstances used to force the gas out will emerge in the water table, along with the gas andtoxic metals, such as arsenic, and subsequently be discharged through plumbing. There arenumerous cases of petrochemicals actually coming out of water faucets in areas where thisfracturing takes place [20].Other than fossil-fuel based natural gas, the renewable potential is with biogas, or methanegenerated such as that from animal wastes and landfills. This offers a realistic transition fromhydrocarbon fuels to something even more renewable, such as solar power. At this point,however, storage technology has not been developed satisfactorily to make electricity a viableoption for long-distance travel or heavy vehicle use. 6 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11The future of CNG and LNG-powered vehiclesThere are some 12 million natural gas-powered vehicles in the world today [21], a paltrynumber, compared to the some billion conventionally-fueled ones. The use of natural gas as afuel will rise, but there is the reality of peak oil and the advent of electric-powered vehicles.Natural gas has been and will continue to be a seemingly desirable partial solution to the airpollution problem but only in a limited sense. While it is true that engine life can be extendedby this cleaner burning fuel and there are fewer contaminants, what needs to be determinedis the overall energy output required to produce the gas as balanced against the output. Werarely see discussions along these lines. That is, what is the nature of the complete energycycle involved the production of alternate forms of powers, such as natural gas in its diverseforms of distribution, as balanced against the energy output of that fuel? There is the issue ofthe infrastructure of filling stations, as well as an assembly-line production of these vehicles.In December 2011, Obama signed a tax bill that gives a $30,000 credit to gasoline fillingstations for adding a natural gas pump [22], and this very well may spur growth in naturalgas usage. Numerous automobile manufacturers are beginning to produce hybrid gasoline-natural gas vehicles [23]. By the time – and even if – the infrastructure is finally put intoplace, the looming question still remains of how available fossil fuels will be. Of course,electric cars have their limitations, not the least of which is limited range and power storageissues, i.e., battery technology. Electric vehicles very well may be the future, but in theinterim, one may expect electric-gas hybrids, another step away from gasoline poweredvehicles. With electric cars, too, one has to compute how much energy it requires to generatethat electricity (for recharging) and the associated environmental costs, given that mostpower generating plants still run on fossil fuels. No comprehensive study has been donecomparing the cost, vehicle needs, required and existing infrastructure, and environmentalissues [24]. What is the end-to-end cost to produce various fuels as opposed to benefitderived?We cannot delude ourselves and jump from fad to fad, such as LNG or electric cars, withoutappreciating the overall picture. It is clear that alternatives to the present reliance on fossilfuels need to be found, not only because of their dwindling supply but because of globalwarming. Many persons discussing the “wow” of natural gas vehicles fail to think critically andaccount for the wider context of the alternative power sources both of electric and fossil fuel 7 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11powered cars. One simply has to separate out the marketing hype from the reality in askingwhat really is “green”. If we don’t think critically about all this we will be deluding onlyourselves.Another constraint is the use of private vehicles, themselves. As traffic congestion grows, ithas to be asked how many more individual vehicles can be added, to say nothing of theadded environmental contamination. That 20% of the world’s population consumes 80% ofthe world’s resources [25], the stark and non-economic reality is that there is going to be alimit to how many vehicles can be produced. Just because of the congestion andenvironmental constraints not everyone may be able to have a personal occupancy vehicle,just because, alone, the planet will not support it. Rather, alternatively powered vehiclesmore likely will be oriented towards mass transit. So, even if there were an unlimited reserveof gas, these two factors alone - strain or the Earth’s resources and congestion - will radicallyshape the direction of any-powered vehicles. Want to learn more about Natural Gas Vehicles? Visit our Download Centre for more articles, white papers and interviews: http://bit.ly/natural-gas-vehiclesReferences(Subject is indicated by URL – accessed 18 September 2011)https://docs.google.com/viewer?url=http://www.controlsouthern.com/documents/regulators/Literature/Bulletins/D103095X012.pdf&embedded=true&chrome=truehttp://en.wikipedia.org/wiki/Methane, http://en.wikipedia.org/wiki/Natural_gashttp://en.wikipedia.org/wiki/Compressed_natural_gashttp://en.wikipedia.org/wiki/Compressed_natural_gashttp://en.wikipedia.org/wiki/File:Carroagas.jpghttp://www.cngnow.com/EN-US/Vehicles/Pages/ConverttoCNG.aspxhttp://cngchat.com/forum/showthread.php?1767-quot-Can-I-convert-my-____-to-run-on-CNG-quot old 6http://www.cartalk.com/content/eco/fringe.htmlhttp://www.ewsews.com/cnghome.htmlhttp://stevemark122000.hubpages.com/hub/Pros-and-Cons-of-Natural-Gas-Carshttp://www.cngcivic.com/CIVIC_GX_CNG_Filters.phphttps://docs.google.com/viewer?url=http://standby.com/propane/pdf/ixpv_05172005.pdf&e 8 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11mbedded=true&chrome=truehttp://www.ipcc.ch/pdf/special-reports/spm/sres-en.pdfhttp://www.theoildrum.com/node/5247,http://www.pennenergy.com/index/articles/display/0663918147/articles/pennenergy/microblogs/rafael-sandrea/natural-gas-supply--potential-setbacks.html,http://ideas.repec.org/a/eap/articl/v39y2009i2p255-270.html ,http://www.ourbusinessnews.com/natural-gas-supplies-within-5-year-average ,https://docs.google.com/viewer?url=http://www.postcarbon.org/reports/PCI-report-nat-gas-future-plain.pdf&embedded=true&chrome=true , andhttp://environmentalheadlines.com/ct/2011/05/12/the-truth-about-natural-gas-supply-costs-environmental-impact/ , as exampleshttp://www.ngv-conference.com/uploadedFiles/EventRedesign/Germany/2011/December/12116003/Assets/Natural-Gas-Vehicles-Status-Barriers-and-Opportunities.pdf, p. 20http://www.eia.gov/dnav/ng/ng_enr_sum_dcu_NUS_a.htmhttp://www.naturalgas.org/overview/resources.asphttp://www.earthisland.org/journal/index.php/elist/eListRead/how_neutral_is_the_potential_gas_committee/http://naturalgas.org/overview/resources.asphttp://en.wikipedia.org/wiki/Hydraulic_fracturing ,http://www.youtube.com/watch?v=dEB_Wwe-uBM , http://what-the-frack.org/2011/08/20/chip-northrup-speaks-about-the-dangers-of-hydrofracking/ ,http://www.eeb.cornell.edu/howarth/Marcellus.html , andhttp://www.fedflyfishers.org/LinkClick.aspx?fileticket=iHCRIpvS7W8%3D&tabid=5095&mid=4733 , http://www.cfg.cornell.edu/http://www.cnbc.com/id/40794709/Natural_Gas_Vehicles_On_The_Road_To_AcceptanceIbid.http://www.greencarcongress.com/natural_gas/ http://www.greencarcongress.com/2011/06/mit-and-iea-reports-take-different-views-of-the-future-of-natural-gas-in-transportation.html#morehttp://www.sustainablesettlement.co.za/issues/resources.html ,https://docs.google.com/viewer?url=http://www.worldresourcesforum.org/files/fischer-kowalski.pdf&embedded=true&chrome=true , http://articles.cnn.com/1999-10-12/us/9910_12_population.cosumption_1_global-population-worlds-scientists?_s=PM:USResources(Subject is indicated by URL – accessed 18 September 2011)http://en.wikipedia.org/wiki/Natural_gas_vehiclehttp://en.wikipedia.org/wiki/Compressed_natural_gashttp://en.wikipedia.org/wiki/Liquefied_natural_gashttp://www.lngpollutes.org/article.php?list=type&type=13 9 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11http://www.naturalgas.org/lng/lng.asphttp://ferc.gov/industries/gas/indus-act/lng.asphttp://www.beg.utexas.edu/energyecon/lng/http://www.beg.utexas.edu/energyecon/lng/documents/CEE_INTRODUCTION_TO_LNG_FINAL.pdfhttp://www.beg.utexas.edu/energyecon/lng/documents/NGC_Interchangeability_Paper.pdfhttp://www.beg.utexas.edu/energyecon/lng/documents/CEE_Role_of_LNG_in_Nat_Gas_Supply_Demand_Final.pdfhttp://www.propane.pro/lpg/15890127/http://en.wikipedia.org/wiki/Natural_gashttp://en.wikipedia.org/wiki/Special_Report_on_Emissions_Scenarios#B2http://www.grida.no/publications/other/ipcc_sr/?src=/climate/ipcc/emission/http://www.cnbc.com/id/40794709/Natural_Gas_Vehicles_On_The_Road_To_Acceptancehttp://www.nextgreencar.com/lpg-cng.phphttps://docs.google.com/viewer?url=http://www.norriseal.com/files/comm_id_47/Norriseal_6300_tech_brochure.pdf&embedded=true&chrome=truehttp://www.ngvaeurope.eu/members/weekly-news/brochure_NAtural_Gas_Vehicle_conference_22_08_2011.pdfhttp://www.ngv-conference.com/uploadedFiles/EventRedesign/Germany/2011/December/12116003/Assets/ISSUES-RELATED-TO-THE-TRANSITION-TO-NATURAL-GAS-UTILIZATION.pdfhttp://www.ngv-conference.com/uploadedFiles/EventRedesign/Germany/2011/December/12116003/Assets/Natural-Gas-Vehicles-Status-Barriers-and-Opportunities.pdfhttp://www.ngv-conference.com/uploadedFiles/EventRedesign/Germany/2011/December/12116003/Assets/Natural-Gas-Vehicles-Fueling-Infrastructure-and-Economics.pdfhttps://docs.google.com/viewer?url=http://www.cleanvehicle.org/committee/technical/PDFs/Conversion_Press_Release.pdf&embedded=true&chrome=true 10 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de
  • 11http://www.racq.com.au/motoring/cars/car_advice/car_fact_sheets/lp_gashttp://www.youtube.com/watch?v=W-uhCIpPhwshttp://www.fueleconomy.gov/feg/bifueltech.shtmlhttp://www.greencarcongress.com/natural_gas/ . 11 IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: eq@iqpc.de | w: www.iqpc.de Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: www.iqpc.de