View source for Vehicle-specific power

{{Orphan|date=March 2013}}

The concept of '''vehicle-specific power''' ('''VSP''') is a formalism used in the evaluation of [[Exhaust gas|vehicle emissions]]. The idea was first developed by J. L. Jiménez {{harv|Jiménez|1998}} at the [[Massachusetts Institute of Technology]].{{sfn|NAP2001|p=108}}{{sfn|NAP2000|p=184}} Informally, it is the sum of the loads resulting from [[aerodynamic drag]], acceleration, [[rolling resistance]], and hill climbing, all divided by the mass of the vehicle.{{sfn|NAP2001|p=108}} Conventionally, it is reported in [[kilowatt]]s per [[tonne]],{{sfn|NAP2001|p=108}} the [[power (physics)|instantaneous power]] demand of the vehicle divided by its mass.{{sfn|NAP2000|p=184}} VSP, combined with [[dynamometer]] and remote-sensing measurements, can be used to determine vehicle emissions.{{sfn|NAP2000|p=184}}

The [[United States Environmental Protection Agency]] held a "modelling shootout" in 2001, to help with the development of its (then) new MOVES (motor vehicle emissions simulator) vehicle emissions model. Two of the four modelling metholodogies in the shootout, one from [[North Carolina State University]] {{harv|Frey|2002}} and one internal to the EPA, used vehicle-specific power metrics.{{sfn|Barth|Younglove|Scora|2005|p=10}}{{sfn|Huai|Durbin|Younglove|Scora|2005|p=9595}} MOVES was eventually implemented using vehicle-specific power as its primary metric.{{sfn|Huai|Durbin|Younglove|Scora|2005|p=9595}} (See {{harvnb|Koupal|Cumberworth|Michaels|Beardsley|2002|loc=§ 7.1.3.1}} for the EPA MOVES draft VSP specification.)

==Formulae==
Jiménez' own formula is:
:<math>\mathrm{VSP} = \frac{\mathrm{power}}{\mathrm{mass}} = \frac{{\operatorname{d}\over\operatorname{d}t}(E_{\mathrm{kinetic}} + E_{\mathrm{potential}}) + F_{\mathrm{rolling}} \cdot v + F_{\mathrm{aerodynamic}} \cdot v + F_{\mathrm{internal}} \cdot v}{m}</math> {{harv|Jiménez|McLintock|McRae|Nelson|1999}}

VSP can be simplified using typical coefficient values. Haibo Zhai of [[North Carolina State University]] provides the following formula for transit buses:
:{{math|1=VSP = ''v'' × (''a'' + ''g'' × sin ''φ'' + ''ψ'') + ''ζ'' × ''v''<sup>3</sup>}}{{sfn|Zhai|2007|p=56–57}}
where:
;''v'':vehicle speed (in metres per second)
;''a'':vehicle acceleration (in metres per second per second)
;''g'':acceleration due to gravity ([[gravitational acceleration|gee]], in metres per second per second)
;''ϕ'':road grade
;''ψ'':rolling resistance coefficient (metres per second per second)
;''ζ'':drag coeficient (reciprocal metres)

==References==

===Cross-reference===
{{reflist|40em}}

===Sources used===
{{refbegin}}
* {{cite book|ref=CITEREFNAP2000|title=Modeling mobile-source emissions|series=Compass series|author=National Research Council Committee to Review EPA's Mobile Source Emissions Factor (Mobile) Model|publisher=National Academies Press|year=2000|isbn=978-0-309-07088-1}}
* {{cite book|ref=CITEREFNAP2001|title=Evaluating vehicle emissions inspection and maintenance programs|author=National Research Council Committee on Vehicle Emission Inspection and Maintenance Programs|publisher=National Academies Press |date=1 November 2001 |isbn=978-0-309-07446-9}}
* {{Cite journal|ref=harv|last1=Barth|first1=Matthew|last2=Younglove|first2=Theodore|last3=Scora|first3=George|year=2005|title=Development of a Heavy-Duty Diesel Modal Emissions and Fuel Consumption Model|work=California Partners for Advanced Transit and Highways (PATH)|url=http://escholarship.org/uc/item/67f0v3zf}}
* {{cite journal|ref=harv|title=Vehicle Specific Power Approach to Estimating On-Road NH<sub>3</sub> Emissions from Light-Duty Vehicles|first1=Tao|last1=Huai|first2=Thomas D.|last2=Durbin|first3=Ted|last3=Younglove|first4=George|last4=Scora|first5=Matthew|last5=Barth|first6=Joseph M.|last6=Norbeck|journal=Environmental Science and Technology|year=2005|volume=39|pages=9595–9600|url=http://cichlid.cert.ucr.edu/research/pubs/6.pdf|format=[[Portable Document Format|PDF]]|doi=10.1021/es050120c|bibcode=2005EnST...39.9595H}}
* {{cite book|ref=harv|title=Regional on-road mobile source emissions characterization for conventional and alternative vehicle technologies|first=Haibo|last=Zhai|publisher=ProQuest|year=2007|isbn=978-0-549-54985-7}}
{{refend}}

==Further reading==
* {{cite thesis|ref=harv|first=J. L.|last=Jiménez|year=1998|title=Understanding and Quantifying Motor Vehicle Emissions with Vehicle Specific Power and TILDAS Remote-Sensing|degree=Ph.D.|publisher=[[Massachusetts Institute of Technology]]|location=Cambridge, Massachusetts}}
* {{cite conference|ref=harv|first1=J. L.|last1=Jiménez|first2=P.M.|last2=McLintock|first3=G.J.|last3=McRae|first4=D.D.|last4=Nelson|first5=M.S.|last5=Zahniser|year=1999|title=Vehicle Specific Power: A Useful Parameter for Remote Sensing and Emissions Studies|booktitle=Ninth CRC On-Road Vehicle Emissions Workshop, San Diego, California, April 1999|url=http://cires.colorado.edu/~jjose/Papers/Jimenez_VSP_9thCRC_99_final.pdf}}
* {{cite journal|ref=harv|title=A Vehicle-Specific Power Approach to Speed- and Facility-Specific Emissions Estimates for Diesel Transit Buses|first1=Haibo|last1=Zhai|first2=H. Christopher|last2=Frey|first3=Nagui M.|last3=Rouphail|journal=Environmental Science and Technology|year=2008|volume=42|issue=21|pages=7985–7991|doi=10.1021/es800208d|bibcode=2008EnST...42.7985Z}}
* {{Cite journal|ref=harv|first=M.|last=Frey|date=October 2002|title=Methodology For Developing Modal Emission Rates For EPA's MOVES|id=EPA420-R-02-027|url=http://epa.gov/otaq/models/ngm/r02027.pdf|format=[[Portable Document Format|PDF]]}}
* {{Cite journal|ref=harv|id=EPA420-P-02-006|date=October 2002|url=http://epa.gov/otaq/models/ngm/p02006.pdf|format=[[Portable Document Format|PDF]]|title=Draft Design and Implementation Plan for EPA's Multi-Scale Motor Vehicle and Equipment Emission System (MOVES)|first1=John|last1=Koupal|first2=Mitch|last2=Cumberworth|first3=Harvey|last3=Michaels|first4=Megan|last4=Beardsley|first5=David|last5=Brzezinski}}

[[Category:Vehicle technology]]


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