COPERT Micro: A Tool To Calculate The Vehicle Emissions In Urban Areas

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About

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This is somehow a special post: from Sunday till previous Tuesday I was in Brussels in order to participate at CONCAWE’s 10th Symposium. A special feature of this event was the “Young Researcher” poster competition.  The call for abstracts was at the previous November, so I submitted my proposal, which was finally selected after an initial selection. In the poster completion there were 14 posters from 10 European countries.

In the next paragraphs you can read a text version of the poster that I presented in the Symposium and you can download if you like the original pdf version that I submitted. So, although this post is quite different than the typical posts I write in this blog, please give it a try. You might find it interesting.

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Introduction

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Methodology

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Exhaust emissions from road transport arise from the combustion of fuels such as gasoline, diesel, liquefied petroleum gas (LPG), and natural gas in internal combustion engines. The air/fuel charge may be ignited by a spark, or it may ignite spontaneously when compressed. The total emissions from road traffic include:

Figure 1. Emissions from road transport.

COPERT Micro was developed focusing primarily on hot exhaust emissions. The vehicle fleet of each traffic link is divided into 230 different categories according to the fuel used, the engine size, the weight and the technology level of the vehicle.

Figure 2. 230 vehicle categories are used in COPERT Micro.

The emission factors for each pollutant and for every vehicle category are obtained experimentally in laboratory by measuring the exhaust emissions of various vehicles at different speeds. The measured emissions are plotted against speed and based on the trend line with the highest value of R2 the equation of the emission factor is derived.

  

Figure 3. NOx emission factor for gasoline Euro 3 passenger cars.

Contrary to other average speed models, COPERT Micro is used in micro level (per traffic link). COPERT Micro incorporates the most up to date emission factors database of COPERT IV complemented by emission factors of TRANSPHORM’s database.

The equations below summarize the basic methodology that is used in COPERT Micro during hot exhaust emissions calculation.

•  EFi = fk(V)     [g//km]
•  Emissionsi,j = Lj x N x Pvehcile category x EFi (V)     [g]
•  Emissionsi,Area = ∑Emissionsi,j     [g]

Where:
EFi (V): emission factor per vehicle category for average speed V [g/km]
fk: polynomial function (derived from trend line)
Emissionsi,j: hot exhaust emissions of pollutant i produced by N vehicles that circulate on the link j [g]
i: pollutant of interest (CO, VOC, NOx, EC etc.)
Lj: length of the link j [km]
N: number of vehicles circulating on the link j
Pvehcile category: percentage of vehicles per vehicle category
Emissionsi,Area: emissions of the entire simulated area

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Results

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COPERT Micro has been successfully used in the following cases:

• The emissions inventory of Athens and Thessaloniki, using PTV VISUM for traffic modelling.
• In two other smaller case-studies COPERT Micro was used to calculate the hot exhaust emissions from Kipseli and Piraeus.
• More recently, it was used to calculate the contribution of different fuels in the CO2 emissions produced by private and public vehicles in the municipality of Thermaikos.

Figure 5. Daily CO2 emissions distribution per fuel produced by private vehicles in the municipality of Thermaikos (October 2011).

In the emissions inventory of Athens, the hourly records of traffic load (vehicles/hour) and average speed from 560 measuring stations were imported to PTV VISUM, as well as the vehicle split composition and the GIS road network of Athens. The output of traffic modelling was the hourly vehicle load, the average speed and the vehicle split composition for 81880 links of the network for a typical Tuesday of October 2010.

Using the output of PTV VISUM as an input to COPERT Micro, the hourly and daily emissions were calculated for all the links of the network. The output emissions from COPERT Micro were imported to a GIS grid in order to be further processed with the atmospheric dispersion model.

Figure 7. Daily CO emissions (kg) on a 100 x 100 (500 x 500 m2) grid (up) and links contribution to daily CO emissions (down) for a typical Tuesday of October 2010 in Greater Athens Area.

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Current Status & Future Development

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• Only hot emissions from vehicles fuelled with gasoline, diesel and LPG can be calculated.
• The calculation of cold start and evaporation emissions will be incorporated in the future.
• Advanced vehicles – such as hybrid and electric cars – will be introduced, as well as vehicles fuelled with alternative fuels, such as biofuels.