Airborne Brake Wear Emissions from a Battery Electric Vehicle

Abstract

Although traffic exhaust emissions in Europe have been drastically reduced, airborne particle emissions caused by brakes and tires are still increasing with the number of vehicles. The measurement of non-exhaust emissions is an emerging technological challenge. We present a custom measurement setup to investigate the brake- and tire-wear emissions of an in-use battery electric vehicle. A separate brake housing and HEPA ventilation enabled airborne brake wear emissions to be measured under realistic conditions without external influences. The emission tests on a chassis dynamometer included particle number concentrations and particle size distribution for diameters of 4 nm to 10 μm. Emission indices were determined for three driving cycles: WLTC Class 3b, WLTC Brake Part 10, and a real driving cycle. Further investigations focused on emission control through regenerative braking and brake coating. Driving with regenerative braking reduced emissions by up to 89.9%, which related to the concentration of particles in the ultrafine/fine size range. Hard-metal brake coating led to a further significant reduction in emissions of up to 78.9%. The results point the way to future RDE measurement of non-exhaust emissions and show the potential of regenerative braking and brake coating to reduce airborne brake wear emissions.

A Practical Approach for On-Road Measurements of Brake Wear Particles from a Light-Duty Vehicle

“…The critical temperature varies between studies but is on the order of 170-300 • C. Men et al [13] observed a large increase in ultrafine particles around 170-270 • C, which were attributed to organic materials in the pad evaporating. Nosko and Olofsson [14] found that the mass fraction of ultrafine particles in PM 10 is negligible at temperatures below 185 • C but stated that it increased to tens of a percent at temperatures above 200 • C. Peaks in ultrafine particles were found at similar critical temperature ranges by Bondorf et al [5] (200-245 • C) and Hesse et al [15] (180-200 • C). The critical temperature may vary with brake material.…”

“…Regenerative braking systems in electric vehicles can reduce brake emissions. Bondorf et al [5] measured particle emissions from brakes on a battery electric vehicle (BEV) with regenerative braking activated and disabled. They found that, during a real-world driving cycle, PN emissions with a size range of 4 nm to 3 µm were reduced by 89.9% when regenerative braking was activated.…”

The Assessment of PM2.5 and PM10 Immission in Atmospheric Air in a Climate Chamber during Tests of an Electric Car on a Chassis Dynamometer

“…In the context of future environmental policy and the development of electric vehicles, the issue of non-exhaust emissions is becoming increasingly important. The problem of dust emissions from tires, brakes and road surfaces has been the subject of many papers [16][17][18][19][20][21][22][23][24][25][26]. In them, the authors focused on the problem of measuring dust emissions from these non-engine sources under laboratory and road conditions [16].…”

“…Laboratory analysis: Brake pad dust can also be collected and analyzed in the laboratory, which allows for the accurate determination of its chemical and physical composition [17,20,24]. 4.…”

Measurement and Analysis of Brake and Tyre Particle Emissions from Automotive Series Components for High-Load Driving Tests on a Wheel and Suspension Test Bed

“…The contribution of BW to NEP emissions ranges from approximately 16 to over 50 per cent [3,5,6], and the contribution of TW to NEP emissions ranges from approximately 5 to over 30 per cent [6,7]. An almost equal contribution of NEP and exhaust emissions to total traffic-related PM10 was already known 10 years ago [5], and the ever-increasing and eventually overwhelming proportion of electrified vehicles (EVs) will continuously increase this fraction as the emission of NEPs is also relevant for EVs [8][9][10]. As a consequence of these trends, initial regulatory efforts resulted in a harmonised procedure for the laboratory measurement of brake emissions for light-duty vehicles, specified in Global Technical Regulation (GTR) 24 of the UNECE.…”