BTA CO2 emission of the vehicle under type approval conditions [g CO2/km] $C_{{\mathrm{CO}}_2}$ CO2 savings [g CO2/km] CO2 Carbon dioxide CO2 (Tk) Arithmetic mean of the CO2 emissions of the vehicle measured using NEDC cycle, ambient temperature of 14 °C and engine coolant start temperatures Tk [g CO2/km] deng Temperature decay factor of the engine coolant cool down curve [1/h] dEST Temperature decay factor of the EST cool down curve [1/h] EST Enthalpy Storage Tank K Effective ratio of thermal inertias [-] m Number of measurements of the sample NEDC New European Driving Cycle $\mathrm{NP}\left(T_{\mathrm{eng}}^{\mathrm{ti}}\right)$ Normalised fuel consumption potential at the engine coolant start temperature for the selected parking times ti [-] pt Parking time [h] Teng Temperature of the engine coolant during parking time [°C] Tengmod Theoretical engine coolant temperature after discharging the EST system [°C] TEST Temperature of the EST coolant during parking time [°C] Tcold Cold start temperature [°C] which is 14 °C Thot Hot start temperature [°C] which is the coolant temperature reached at the end of the NEDC cycle SOC State of charge SVSpt Share of parking time distribution [%] as defined in Table 6 WFti Weighting factor for the parking time ti [%] as defined in Table 3

Index ti refers to the selected parking times as defined in Table 1

Index j refers to measurements of the sample

Index k refers to engine coolant start temperatures

The least squares method shall be used for the fitting of the curves. To do that, at least the temperature measurement data of the first 30 minutes after engine cut-off are not to be considered because of the untypical behaviour of the coolant temperature after switching off the coolant system.

Using Formula 1, the engine temperature at specific parking time conditions ( $T_{\mathrm{eng}}^{\mathrm{ti}}$ ) should be calculated and given in Table 1.

Engine temperature at selected parking time conditions

Selected parking time (ti)	t1	t2	t3
pt [h]	2,5	4,5	16,5
$T_{\mathrm{eng}}^{\mathrm{ti}}$ [°C]

where k = 1, 2, …, 5

T1 = Tcold

T2 = Thot

$T_3=T_{\mathrm{eng}}^{\mathrm{t1}}$

$T_4=T_{\mathrm{eng}}^{\mathrm{t2}}$

$T_5=T_{\mathrm{eng}}^{\mathrm{t3}}$

CO2 emission at different engine coolant start temperatures

Engine coolant starting temperature Tk	Tcold	Thot	$T_{\mathrm{eng}}^{\mathrm{t1}}$	$T_{\mathrm{eng}}^{\mathrm{t2}}$	$T_{\mathrm{eng}}^{\mathrm{t3}}$
CO2(Tk) [g CO2/km]

Then, the theoretical engine coolant temperature after discharging the EST system for the selected parking time conditions $T_{\mathrm{engmod}}^{\mathrm{ti}}$ , shall be calculated using Formula 5.

The relative ratio of thermal inertias Kti at the selected parking time conditions shall be defined using Formula 6.

The resulting effective ratio of thermal inertias K is calculated weighting the three results Kti by the share of vehicle stops, as defined by Formula 7.

where

WFti Weighting factor for the parking time ti [-] as defined in Table 3

Weighting parameter for K factor calculation

WFt1 [%]	63,4
WFt2 [%]	14,0
WFt3 [%]	22,6

The theoretical temperature of the engine after discharging the EST system for the parking time condition pt $T_{\mathrm{engmod}}^{\mathrm{pt}}$ shall be calculated using Formula 8.

The calculation results shall be given in Table 4

Theoretical temperature of the engine after discharging the EST system for different parking times

pt [h]	0,5	1,5	2,5	3,5	4,5	5,5	6,5	7,5	8,5	9,5	10,5	11,5
$T_{\mathrm{engmod}}^{\mathrm{pt}}$ [°C]
pt [h]	12,5	13,5	14,5	15,5	16,5	17,5	18,5	19,5	20,5	21,5	22,5	23,5
$T_{\mathrm{engmod}}^{\mathrm{pt}}$ [°C]

The calculation results shall be given in Table 5

Relative CO2 reduction potential ${\mathrm{\Delta CO}}_{2_{\mathrm{pt}}}$ for different parking times

pt [h]	0,5	1,5	2,5	3,5	4,5	5,5	6,5	7,5	8,5	9,5	10,5	11,5
ΔCO2(pt) [%]
pt [h]	12,5	13,5	14,5	15,5	16,5	17,5	18,5	19,5	20,5	21,5	22,5	23,5
ΔCO2(pt) [%]

The CO2 savings weighted by the parking times (pt) shall be calculated using Formula 11.

where:

SVSpt Share of parking time distribution [%] as defined in Table 6

Parking time distribution (share of vehicle stops)

pt [h]	0,5	1,5	2,5	3,5	4,5	5,5	6,5	7,5	8,5	9,5	10,5	11,5
SVSpt [%]	36	13	6	4	2	2	1	1	3	4	3	1
pt [h]	12,5	13,5	14,5	15,5	16,5	17,5	18,5	19,5	20,5	21,5	22,5	23,5
SVSpt [%]	1	3	3	2	1	1	1	1	1	1	1	1

where k = 1, 2, …, 5

T1 = Tcold

T2 = Thot

$T_3=T_{\mathrm{eng}}^{\mathrm{t1}}$

$T_4=T_{\mathrm{eng}}^{\mathrm{t2}}$

$T_5=T_{\mathrm{eng}}^{\mathrm{t3}}$

The standard deviation of the CO2 savings $S_{C_{{\mathrm{CO}}_2}}$ is to be calculated by means of Formula 13.

where

where:

MT Minimum threshold [gCO2/km], which is 1 gCO2/km ${\mathrm{\Delta CO}}_{2_m}$ CO2 correction coefficient due to the mass increase due to the installation of the EST system. For ${\mathrm{\Delta CO}}_{2_m}$ the data in Table 7 is to be used.

CO2 correction coefficient due to the extra mass

Type of fuel	CO2 correction coefficient due to the extra mass ( ${\mathrm{\Delta CO}}_{2_m}$ )[g CO2/km]
Petrol	0,0277 · Δm
Diesel	0,0383 · Δm

In Table 7 Δm is the extra mass due to the installation of the EST system. It is the mass of the EST system fully charged with the coolant.