ANNEX

METHODOLOGY TO DETERMINE THE CO2 SAVINGS OF A 12 V EFFICIENT ALTERNATOR FOR CONVENTIONAL COMBUSTION ENGINE POWERED N1 VEHICLES

1.   Introduction

In order to determine the CO2 savings that can be attributed to the use of an efficient alternator in an N1 vehicle, it is necessary to specify the following:

(1)	The testing conditions;

(2)	The test equipment;

(3)	The determination of the efficiency of the efficient alternator and the baseline alternator;

(4)	The calculation of the CO2 savings;

(5)	The calculation of the statistical error.

Symbols, parameters and units

Latin symbols

	—	CO2 savings [g CO2/km]
CO2	—	Carbon dioxide
CF	—	Conversion factor (l/100 km) - (g CO2/km) [gCO2/l] as defined in Table 3
h	—	Frequency as defined in Table 1
I	—	Current intensity at which the measurement shall be carried out [A]
m	—	Number of measurements of the sample
M	—	Torque [Nm]
n	—	Rotational frequency [min– 1] as defined in Table 1
P	—	Power [W]
	—	Standard deviation of the eco-innovative alternator efficiency [%]
	—	Standard deviation of the eco-innovative alternator efficiency mean [%]
	—	Standard deviation of the total CO2 savings [g CO2/km]
U	—	Test voltage at which the measurement shall be carried out [V]
v	—	Mean driving speed of the New European Driving Cycle (NEDC) [km/h]
VPe	—	Consumption of effective power [l/kWh] as defined in Table 2
	—	Sensitivity of calculated CO2 savings related to the efficiency of the eco-innovative alternator

Greek symbols

Δ	—	Difference
η	—	Baseline alternator efficiency [%]
ηEI	—	Efficient alternator efficiency [%]
	—	Mean of the eco-innovative alternator efficiency at operating point i [%]

Subscripts

Index (i) refers to operating point

Index (j) refers to measurement of the sample

EI	—	Eco-innovative
m	—	Mechanical
RW	—	Real-world conditions
TA	—	Type approval conditions
B	—	Baseline

2.   Test conditions and equipment

The testing conditions shall fulfil the requirements specified in ISO 8854:2012 (1).

The test equipment shall be in accordance with the specifications set out in ISO 8854:2012.

3.   Measurements and determination of the efficiency

The efficiency of the efficient alternator shall be determined in accordance with ISO 8854:2012, with the exception of the elements specified in the present paragraph.

The measurements shall be conducted at different operating points i, as defined in Table 1. The alternator current intensity is defined as half of the rated current for all operating points. For each speed the voltage and the output current of the alternator are to be kept constant, the voltage at 14,3 V.

Table 1

Operating points

Operating point i	Holding time [s]	Rotational frequency ni [min– 1]	Frequency 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 shall be calculated in accordance with to Formula 1.

Formula 1

All efficiency measurements are to be performed consecutively at least five (5) times. The average of the measurements at each operating point (

) has to be calculated.

The efficiency of the eco-innovative alternator (ηEI) shall be calculated in accordance with Formula 2.

Formula 2

The efficient alternator leads to saved mechanical power under real-world conditions (ΔPmRW) and type approval conditions (ΔPmTA) as defined in Formula 3.

Formula 3

Where the saved mechanical power under real-world conditions (ΔPmRW) is calculated in accordance with Formula 4 and the saved mechanical power under type-approval conditions (ΔPmTA) in accordance with Formula 5.

Formula 4

Formula 5

where

PRW : Power requirement under ‘real-world’ conditions [W], which is 750W

PTA : Power requirement under type-approval conditions [W], which is 350W

ηB : Efficiency of the baseline alternator [%], which is 67 %

4.   Calculation of the CO2 savings

The CO2 savings of the efficient alternator are to be calculated with the following formula.

Formula 6

where

v: Mean driving speed of the NEDC [km/h], which is 33,58 km/h

VPe : Is the consumption of effective power specified in the following Table 2

Table 2

Consumption of effective power

Type of engine	Consumption of effective power (VPe) [l/kWh]
Petrol	0,264
Petrol Turbo	0,280
Diesel	0,220

CF: Is the factor specified in the following Table 3

Table 3

Fuel conversion factor

Type of fuel	Conversion factor (l/100 km) - (g CO2/km) (CF) [gCO2/l]
Petrol	2 330
Diesel	2 640

5.   Calculation of the statistical error

The statistical errors in the results of the testing methodology caused by the measurements are to be quantified. For each operating point the standard deviation is calculated as defined by the following formula:

Formula 7

The standard deviation of the efficiency value of the efficient alternator (

) is calculated in accordance with formula 8:

Formula 8

The standard deviation of the alternator efficiency (

) leads to an error in the CO2 savings (

). That error is calculated in accordance with formula 9:

Formula 9

Statistical Significance

It has to be demonstrated for each type, variant and version of a vehicle fitted with the efficient alternator that the error in the CO2 savings calculated in accordance with Formula 9 is not greater than the difference between the total CO2 savings and the minimum savings threshold specified in Article 9(1) of Regulation (EU) No 427/2014 (see Formula 10).

Formula 10

Where:

MT: minimum threshold [gCO2/km]

: total CO2 saving [gCO2/km]

: standard deviation of the total CO2 saving [gCO2/km]

: CO2 correction coefficient due to the positive mass difference between the efficient alternator and the baseline alternator.

is calculated following Table 4:

Table 4

CO2 correction coefficient due to the extra mass
Petrol ( ) [g CO2/km kg]	0,0277 · Δm
Diesel ( ) [g CO2/km kg]	0,0383 · Δm

In Table 4 Δm is the extra mass due to the installation of the efficient alternator. It is the positive difference between the mass of the efficient alternator and the mass of baseline alternator. The mass of the baseline alternator is 7 kg. On the evaluation of the extra mass the manufacturer must hand over verified documentation to the Type-Approval Authority.

Test and evaluation Report

The report shall include:

—	Model and mass of the tested alternators

—	Description of the bench

—	Test results (measured values)

—	Calculated results and corresponding formulae

The efficient alternator to be fitted in vehicles

The type approval authority is to certify the CO2 savings based on measurements of the efficient alternator and the baseline alternator using the test methodology set out in this Annex. Where the CO2 emission savings are below the threshold specified in Article 9(1), the second subparagraph of Article 11(2) of Regulation (EU) No 427/2014 shall apply.

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(1)  ISO 8854:2012 Road vehicles – Alternators with regulators – Test methods and general requirements

Reference number ISO 8854:2012, published on 1 June 2012.