ANNEX

Methodology to determine the CO2 savings of the technology used in a 48 Volt efficient motor-generator combined with a 48 Volt/12 Volt DC/DC converter 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 a 48 Volt efficient motor-generator (‘48V motor-generator’), combined with a 48 Volt/12 Volt DC/DC converter ‘48V/12V DC/DC converter’), in an M1 or N1 vehicle as specified in Article 1(a)).

2. DETERMINATION OF THE EFFICIENCIES

The efficiency of the 48V motor-generator and the 48V/12V DC/DC converter is to be determined separately as specified in points 2.1 and 2.2. The resulting values are to be used as input for the calculation of the total efficiency of the 48V motor-generator combined with the 48V/12V DC/DC converter in accordance with point 2.3.

2.1. 48V motor-generator efficiency

The efficiency of the 48V 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 48V motor-generator are the same as or equivalent to those set out in Table 1.

The efficiency of the 48V 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 48V motor-generator at each operating point shall be half the rated current. For each operating point, the voltage and the output current of the 48V motor-generator shall be kept constant during the measurement, with the voltage at 52V.

Table 1

Operating point i Holding time [s] Rotational frequency Frequency of operating points 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 48V 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 are to 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 48V motor-generator [%] shall be calculated in accordance with Formula 2.

Formula 2

where

is the mean efficiency of the 48V motor-generator determined for operating point i [%] hi is the frequency of operating point i, as set out in Table 1.

2.2. 48V/12V DC/DC converter efficiency

The efficiency of the 48V/12V DC/DC converter shall be determined under the following conditions:

— Input voltage of 52 V

— Output voltage of 14,3 V

— Output current: nominal power of the 48V/12V DC/DC converter divided by the output voltage of 14,3 V

The nominal power of the 48V/12V DC/DC converter shall be the continuous output power certified by the supplier in accordance with the requirements specified in ISO 8854:2012.

The efficiency of the 48V/12V DC/DC converter [%] shall be calculated from the current and voltage intensity measurements according to Formula 3.

Formula 3

where

is the input voltage, which shall be set to 52 [V] is the current intensity measured on the input side [A] is the output voltage, which shall be set to 14,3 [V] is the current intensity measured on the output side, which should be equal to the nominal power of the 48V/12V DC/DC converter divided by the output voltage [A]

The measurements and efficiency calculations shall be repeated at least five (5) times consecutively.

The average of those efficiencies shall then be the efficiency of the 48V/12V DC/DC converter [%].

2.3. Combined efficiency

The efficiency of the 48V motor generator combined with the 48V/12V DC/DC converter [%] is calculated in accordance with Formula 4.

Formula 4

: is the efficiency of the 48V motor-generator, as determined in point 2.1 [%] is the efficiency of the 48V/12V DC/DC converter, as determined in point 2.2 [%]

3. CALCULATION OF THE CO2 SAVINGS

3.1. Saved mechanical power

The difference [W] between the saved mechanical power when using the 48V motor generator combined with the 48V/12V DC/DC converter under real-world conditions and the saved mechanical power when using the 48V motor generator combined with the 48V/12V DC/DC converter under type-approval conditions shall be calculated in accordance with Formula 5.

Formula 5

where

shall be calculated in accordance with Formula 6 and in accordance with Formula 7.

Formula 6

Formula 7

where,

is the efficiency of the 48V motor-generator combined with the 48V/12V DC/DC converter, as determined in point 2.3 [%] is the power requirement under ‘real-world’ conditions, which is 750 W is the power requirement under ‘type-approval’ conditions, which is 350 W is the efficiency of the baseline alternator, which is 67 %

3.2. Calculation of the CO2 savings

The CO2 savings of the 48V motor-generator combined with the 48V/12V DC/DC converter shall be calculated in accordance with Formula 8.

Formula 8

where,

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 is the mean driving speed of the WLTP, which is 46,6 km/h is the consumption of effective power as specified in Table 2 [l/kWh] CF is the conversion factor as set out in Table 3

Table 2

Type of engine Consumption of effective power Petrol-fuelled other than turbo-charged 0,264 Turbo-charged petrol-fuelled 0,280 Diesel-fuelled 0,220





Table 3

Type of fuel Conversion factor (CF) Petrol 2 330 Diesel 2 640

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.

For this, the following calculations are needed.

First, the standard deviation of the efficiency of the 48V motor-generator at each operating point [%] shall be calculated in accordance with Formula 9.

Formula 9

where

is the number of measurements j undertaken at each operating point i for the 48V motor-generator efficiency, as referred to in point 2.1 is the efficiency of the 48V motor-generator calculated for an individual measurement j at operating point i as referred to in point 2.1 [%] is the average efficiency of the 48V motor-generator calculated for an operating point i, as determined in point 2.1 [%]

Next, the standard deviation of the efficiency of the 48V motor-generator [%] shall be calculated in accordance with Formula 10.

Formula 10

where

is as determined by Formula 9 [%] hi is the frequency of operating point i, as set out in Table 1.

Then, the standard deviation of the efficiency of the 48V/12V DC/DC converter [%] shall be calculated in accordance with Formula 11.

Formula 11

where

L is the number of measurements l undertaken for the 48V/12V DC/DC converter, as referred to in point 2.2 is the efficiency of the 48V/12V DC/DC converter calculated for an individual measurement l as referred to in point 2.2 [%] is the efficiency of the 48V/12V DC/DC converter, as determined in point 2.2 [%]

Finally, the uncertainty in the CO2 savings of the 48V motor-generator combined with the 48V/12V DC/DC converter shall be calculated in accordance with Formula 12 and shall not exceed 30 % of the CO2 savings.

Formula 12

where

is the power requirement under ‘real-world’ conditions, which is 750 W is the power requirement under type-approval conditions, which is 350 W is the total efficiency of the 48V motor-generator combined with the 48V/12V DC/DC converter as determined in point 2.3 [%] is the consumption of effective power as specified in Table 2 [l/kWh] is the fuel conversion factor as specified in Table 3 is the mean driving speed of the WLTP, which is 46,6 km/h is standard deviation of the efficiency of the 48V motor-generator as determined in accordance with Formula 10 [%] is the efficiency of the 48V motor-generator, as determined in point 2.1 [%] is the standard deviation of the efficiency of the 48V/12V DC/DC converter, as determined in accordance with Formula 11 [%] is the efficiency of the 48V/12V DC/DC converter as determined in point 2.2 [%]

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 48V motor-generator combined with the 48V/12V DC/DC converter that the minimum threshold criterion as specified in Article 9(1)(b) of Implementing Regulation (EU) No 725/2011 and Implementing Regulation (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 13, 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 48V motor-generator combined with the 48V/12V DC/DC converter 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 48V motor-generator combined with the 48V/12V DC/DC converter as certified by the supplier.

Formula 13

where,

MT is 0,5 g CO2/km as specified in Article 9(1)(b) of Implementing Regulation (EU) No 725/2011 and Commission Implementing Regulation (EU) No 427/2014 is the CO 2 savings as determined in point 3.2 uncertainty of the total CO 2 savings as determined in point 3.3 CO 2 correction, in the case of a positive mass difference (Δm) [kg] between the 48V motor-generator combined with the 48V/12V DC/DC converter and the baseline alternator, calculated in accordance with Table 4:

Table 4

Type of fuel CO2 correction Petrol 0,0277 Δm Diesel 0,0383 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 are those calculated in accordance with Formula 14. The CO2 savings shall be recorded in the type approval certificate for each vehicle version fitted with the 48V motor-generator combined with the 48V/12V DC/DC converter.

Formula 14

where,