ANNEX
Methodology to determine the CO 2 savings of a 12 V efficient alternator in passenger cars and light commercial vehicles with internal combustion engine powertrain (fulfilling the conditions specified in Article 1 by reference to the Worldwide Harmonized Light Vehicle Test Procedure)
1. INTRODUCTION
In order to determine the CO 2 savings that can be attributed to the use of a 12 V efficient alternator in a passenger car and light commercial vehicle with internal combustion engine powertrain, it is necessary to specify the following:
(1)
the testing conditions;
(2)
the test equipment;
(3)
the procedure to determine the total efficiency;
(4)
the procedure to determine the CO 2 savings;
(5)
the procedure to determine the uncertainty of the CO 2 savings.
2. SYMBOLS, PARAMETERS AND UNITS
Latin symbols
-
CO 2 savings [g CO 2 /km]
CO 2
-
Carbon dioxide
CF
-
Conversion factor (l/100 km) - (g CO 2 /km) [gCO 2 /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]
s ηEI
-
Standard deviation of the eco-innovative alternator efficiency [%]
-
Standard deviation of the eco-innovative alternator efficiency mean [%]
-
Standard deviation of the total CO 2 savings [g CO 2 /km]
U
-
Test voltage at which the measurement shall be carried out [V]
v
-
Mean driving speed of the Worldwide harmonised Light-duty vehicles Test Cycle (WLTC) [km/h]
V Pe
-
Consumption of effective power [l/kWh] as defined in Table 2
-
Sensitivity of calculated CO 2 savings related to the efficiency of the eco-innovative alternator
Greek symbols
Δ
-
Difference
η
-
Baseline alternator efficiency [%]
η EI
-
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
3. TEST CONDITIONS
The testing conditions shall fulfil the requirements specified in ISO 8854:2012 ( 1 ) .
4. TEST EQUIPMENT
The test equipment shall be in accordance with the specifications set out in ISO 8854:2012 ( 1 ) .
5. MEASUREMENTS AND DETERMINATION OF THE EFFICIENCY
The efficiency of the 12 V efficient alternator shall be determined in accordance with ISO 8854:2012 ( 1 ) , 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 point
i
Holding time
[s]
Rotational frequency
n i [min -1 ]
Frequency
h i
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 Formula 1.
Formula 1
Formula 1
All efficiency measurements shall 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 (η EI ) shall be calculated in accordance with Formula 2
Formula 2
Formula 2
The efficient alternator leads to saved mechanical power under real-world conditions (ΔP mRW ) and type approval conditions (ΔP mTA ) as defined in Formula 3.
ΔP m = ΔP mRW - ΔP mTA
where the saved mechanical power under real-world conditions (ΔP mRW ) is calculated in accordance with Formula 4 and the saved mechanical power under type-approval conditions (ΔP mTA ) in accordance with Formula 5.
Formula 4
Formula 4
Formula 5
Formula 5
Where:
P RW
:
Power requirement under real-world conditions [W], which is 750W
P TA
:
Power requirement under type-approval conditions [W], which is 350W
η B
:
Efficiency of the baseline alternator [%], which is 67%
6. CALCULATION OF THE CO 2 SAVINGS
The CO 2 savings of the efficient alternator are to be calculated with Formula 6.
Formula 6
Formula 6
Where:
v
:
Mean driving speed of the WLTC [km/h], which is 46,60 km/h
V Pe
:
Consumption of effective power specified in the following Table 2:
Table 2
Consumption of effective power
Type of engine
Consumption of effective power (V Pe )
[l/kWh]
Petrol
0,264
Petrol Turbo
0,280
Diesel
0,220
CF: Factor specified in the following Table 3:
Table 3
Fuel conversion factor
Type of fuel
Conversion factor (l/100 km) - (g CO 2 /km) (CF)
[gCO 2 /l]
Petrol
2 330
Diesel
2 640
7. CALCULATION OF THE STATISTICAL ERROR
The statistical errors in the results of the testing methodology caused by the measurements shall be quantified. For each operating point the standard deviation shall be calculated in accordance with Formula 7:
Formula 7
Formula 7
The standard deviation of the efficiency value of the efficient alternator (s ηEI ) shall be calculated in accordance with Formula 8:
Formula 8
Formula 8
The standard deviation of the alternator efficiency (s ηEI ) leads to an error in the CO 2 savings (
). That error shall be calculated in accordance with Formula 9:
Formula 9
Formula 9
8. 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 CO 2 savings calculated in accordance with Formula 9 is not greater than the difference between the total CO 2 savings and the minimum savings threshold specified in Article 9(1) of Regulation (EU) No 725/2011 (see Formula 10).
Formula 10
Formula 10
Where:
MT
:
Minimum threshold [gCO 2 /km]
:
Total CO 2 saving [gCO 2 /km]
:
Standard deviation of the total CO 2 saving [gCO 2 /km]
:
CO 2 correction coefficient due to the positive mass difference between the efficient alternator and the baseline alternator.
shall be calculated following Table 4:
Table 4
CO 2 correction coefficient due to the extra mass
Petrol (
) [g CO 2 /km kg]
0,0277•Δm
Diesel (
) [g CO 2 /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.
9. 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.
10. THE EFFICIENT ALTERNATOR TO BE FITTED IN VEHICLES
The type-approval authority shall certify the CO 2 savings based on measurements of the efficient alternator and the baseline alternator using the test methodology set out in this Annex. Where the CO 2 emission savings are below the threshold specified in Article 9(1), the second subparagraph of Article 11(2) of Regulation (EU) No 725/2011 shall apply.
( 1 ) ISO 8854:2012 Road vehicles – Alternators with regulators – Test methods and general requirements Reference number ISO 8854:2012, published on 1 June 2012.