ANNEX

Methodology to determine the CO2 savings of the technology used in a 12 Volt efficient motor-generator for conventional combustion engine and certain hybrid electric passenger cars and light commercial vehicles

1. INTRODUCTION

This Annex sets out the methodology to determine the CO2 (carbon dioxide) emission savings from the use of the efficient generator function of a 12 Volt motor-generator (‘12V motor-generator’) in an M1 or N1 vehicle as specified in Article 1.

2. DETERMINATION OF THE EFFICIENCY OF THE 12V MOTOR GENERATOR

The efficiency of the 12V motor-generator shall be determined in accordance with ISO 8854:2012, with the following precisions.

The manufacturer shall provide evidence to the type-approval authority that the frequency ranges of the 12V motor-generator are the same as or equivalent to those set out in Table 1.

The efficiency of the 12V motor-generator shall be determined on the basis of measurements at each of the operating points listed in Table 1.

The current intensity of the 12V motor-generator at each operating point shall be half the rated current. For each operating point, the voltage and the output current of the 12V motor-generator shall be kept constant during the measurement, with the voltage at 14,3 V.

Table 1

Operating point i Holding time [s] Rotational frequency ni [min–1] Frequency of operating points hi 1 1 200 1 800 0,25 2 1 200 3 000 0,40 3 600 6 000 0,25 4 300 10 000 0,10

The efficiency of the 12V motor-generator at each operating point i ( ) [%] shall be calculated in accordance with Formula 1.

Formula 1

where, for each operating point i,

Ui is the voltage [V]; Ii is the current intensity [A]; Μi is the torque [Nm]; ni is the rotational frequency [min-1].

For each operating point, the measurements shall be performed at least five times consecutively and the efficiency shall be calculated for each of those measurements ( ) with j being the index referring to one set of measurements.

For each operating point, the average of those efficiencies ( ) shall be calculated.

The efficiency of the 12V motor-generator (ηMG) [%] shall be calculated in accordance with Formula 2.

Formula 2

where,

is the average efficiency of the 12V motor-generator determined for operating point i [%] hi is the frequency of operating point i, as set out in Table 1.

3. CALCULATION OF THE CO2 SAVINGS AND THEIR UNCERTAINTY

3.1. Saved mechanical power

The difference (ΔPm) [W] between the saved mechanical power when using the 12V motor generator under real-world conditions (ΔPmRW) and the saved mechanical power when using the 12V motor under type-approval conditions (ΔPmTA) shall be calculated in accordance with Formula 3.

Formula 3

where,

ΔPmRW shall be calculated in accordance with Formula 4 and ΔPmTA in accordance with Formula 5.

Formula 4

Formula 5

where,

ηMG is the efficiency of the 12V motor-generator as determined in point 2 [%] PRW is the power requirement under ‘real-world’ conditions, which is 750 W PTA is the power requirement under ‘type-approval’ conditions, which is 350 W ηB is the efficiency of the baseline alternator, which is 67 %

3.2. Calculation of the CO2 savings

The CO2 savings of the 12V motor-generator ( ) [gCO2/km] shall be calculated in accordance with Formula 6.

Formula 6

where,

ΔPm is the difference between the saved mechanical power under real-world conditions and the saved mechanical power under type-approval conditions, as determined in point 3.1 v is the mean driving speed of the WLTP, which is 46,6 km/h VPe is the consumption of effective power as specified in Table 2 [l/kWh] CF is the conversion factor as set out in Table 3 [gCO2/l]

Table 2

Type of engine Consumption of effective power (VPe) [l/kWh] Petrol- or E85-fuelled other than turbo-charged 0,264 Turbo-charged petrol- or E85-fuelled 0,280 Diesel-fuelled 0,220 LPG fuelled 0,342 Turbo-charged LPG-fuelled 0,363 Consumption of effective power (VPe) [m3/kWh] CNG (G20) other than turbo-charged 0,259 Turbo-charged CNG (G20) 0,275





Table 3

Type of fuel Conversion factor (CF) [gCO2/l] Petrol/E85 2 330 Diesel 2 640 LPG 1 629 Conversion factor (CF) [gCO2/m3] CNG (G20) 1 795

3.3. Calculation of the uncertainty of the CO2 savings

The uncertainty of the CO2 savings calculated in accordance with point 3.2 shall be quantified as follows.

First, the standard deviation of the efficiency of the 12V motor-generator at each operating point ( ) [%] shall be calculated in accordance with Formula 7.

Formula 7

where,

m is the number of measurements j undertaken for determining the 12V motor-generator efficiency at each operating point i, as referred to in point 2 is the efficiency of the 12V motor-generator calculated for an individual measurement j at operating point i as referred to in point 2 [%] is the average efficiency of the 12V motor-generator calculated for an operating point i, as determined in point 2 [%]

Next, the standard deviation of the efficiency of the 12V motor-generator ( ) [%] shall be calculated in accordance with Formula 8.

Formula 8

where,

is as determined by Formula 7 [%] hi is the frequency of operating point i, as set out in Table 1.

Finally, the uncertainty of the CO2 savings ( ) [gCO2/km] of the 12V motor-generator shall be calculated in accordance with Formula 9 and shall not exceed 30 % of the CO2 savings.

Formula 9

where,

PRW is the power requirement under ‘real-world’ conditions, which is 750 W PTA is the power requirement under type-approval conditions, which is 350 W ηMG is the efficiency of the 12V motor-generator, as determined in point 2 [%] VPe is the consumption of effective power as specified in Table 2 [l/kWh] CF is the fuel conversion factor as specified in Table 3 [gCO2/l] v is the mean driving speed of the WLTP, which is 46,6 km/h is standard deviation of the efficiency of the 12V motor-generator as determined in accordance with Formula 8 [%] ηMG is the efficiency of the 12V motor-generator, as determined in point 2 [%]

3.4. Rounding

The CO2 savings ( ) calculated in accordance with point 3.2 and the uncertainty of the CO2 savings ( ) calculated in accordance with point 3.3 shall be rounded to a maximum of two decimal places.

Each value used in the calculation of the CO2 savings can be applied unrounded or must be rounded to the minimum number of decimal places which allows the maximum total impact (i.e. combined impact of all rounded values) on the savings to be lower than 0,25 gCO2/km.

3.5. Check against the minimum CO2 savings threshold

The type-approval authority shall ensure for each vehicle version fitted with the 12V motor-generator that the minimum threshold criterion as specified in Article 9(1)(b) of Implementing Regulations (EU) No 725/2011 and (EU) No 427/2014 is met.

When verifying whether the minimum threshold criterion is met, the type-approval authority shall take into account, in accordance with Formula 10, the CO2 savings determined in point 3.2, the uncertainty determined in point 3.3 and, where applicable, a CO2 correction, in the case of a positive mass difference (Δm) between the 12V motor-generator and the baseline alternator.

For the purpose of the positive mass correction, the mass of the baseline alternator shall be set to 7 kg.

The manufacturer shall provide to the type approval authority information on the mass of the 12V motor-generator as certified by the supplier.

Formula 10

where,

MT is 0,5 gCO2/km as specified in Article 9(1)(b) of Implementing Regulations (EU) No 725/2011 and (EU) No 427/2014 is the CO2 savings as determined in point 3.2 [gCO2/km] uncertainty of the CO2 savings as determined in point 3.3 [gCO2/km] CO2 correction, in the case of a positive mass difference (Δm) [kg] between the 12V motor-generator and the baseline alternator, calculated in accordance with Table 4 [gCO2/km]

Table 4

Type of fuel CO 2 correction ( ) [gCO 2 /km] Petrol/E85 0,0277 • Δm Diesel 0,0383 • Δm LPG 0,0251 • Δm CNG 0,0209 • Δm

4. CERTIFICATION OF CO2 SAVINGS

The CO2 savings to be certified by the type-approval authority in accordance with Article 11 of Implementing Regulations (EU) No 725/2011 or (EU) No 427/2014 ( ) [gCO2/km] are those calculated in accordance with Formula 11. The CO2 savings shall be recorded in the type approval certificate for each vehicle version fitted with the 12V motor-generator.

Formula 11

where,