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WI and GCV values in European networks

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Wobbe Index and Gross Calorific Value in European networks

Analysis of ranges and variability

1. Background

As a continuation of mandate M400 and supported by the conclusions of the 29th Madrid

forum, CEN continues working on finding an EU agreement for a Wobbe Index band, including

elaborating on the possibility of regional bands.

With that aim, CEN Sector Forum1 Gas working group “Pre-normative study of H-gas quality

parameter” is conducting a study on the impact of H-gas quality parameters not yet or

insufficiently specified in EN16726:2015 (‘Gas infrastructure – Quality of gas – Group H’) on

the whole gas supply chain. The analysis will be undertaken on the basis of technical evidence.

As part of the preparatory work, CEN SFGas WG has arranged a survey to collect Wobbe index

(WI) and (upon request of some end users) the gross calorific value (GCV) measured data from

gas system operators and end users. In this context, ENTSOG has offered to collect input from

its members.

The survey results will be used as basis to decide on possible Wobbe Index scenarios2.

In addition, this document proposes an analysis methodology for the data collected by

ENTSOG with the view of facilitating the choice of potential Wobbe Index ranges and related

parameters (among others, the variability).

2. Scope

The survey on which this report is based was limited to GCV and WI. The data was provided

by ENTSOG members on a voluntary basis covering different types of gases and network points

with a special focus on transmission system exit points. Both points with high variability and

low variability of gas quality as reasonably determined by the TSO have been included.

1 A Sector Forum is a platform aiming at facilitating the exchange of information between the different

stakeholders, coordinating and identifying the standardization needs in a specific field of CEN work. 2 Scenario in this context is meant as description of a set of boundary conditions, which will be assessed for

consequences on the whole gas chain


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The survey period was agreed from 1 January 2015 to 31 December 2016. Hourly data was

welcomed but TSOs were asked to provide data with 15 minutes resolution when available.

3. Disclaimer

This report was prepared in a professional and workmanlike manner by ENTSOG on the basis

of information collected and compiled by ENTSOG. It contains ENTSOG own analysis based

upon this information. All content is provided “as is” without any warranty of any kind as to

the completeness, accuracy, fitness for any particular purpose or any use of results based on

this information and ENTSOG hereby expressly disclaims all warranties and representations,

whether express or implied, including without limitation, warranties or representations of

merchantability or fitness for a particular purpose. ENTSOG is not liable for any consequence

resulting from the reliance and/or the use of any information hereby provided. The reader in

its capacity as professional individual or entity shall be responsible for seeking to verify the

accurate and relevant information needed for its own assessment and decision and shall be

responsible for use of the document or any part of it for any purpose other than that for which

it is intended.

4. Methodology and indicators

For each data set (or point) the following calculations were carried out:

Summary statistics: maximum, minimum, 95 and 5 percentiles, average and standard deviations.

Frequency distribution of values (i.e. the probability of finding a given value within the time series)

Amplitude of variation probability for different time periods (e.g. how frequently a variation of 2 MJ/m3 is found within a 24 hour period).

Maximum amplitude of variation per period (e.g. what is the maximum variation ever registered for a 30 day period).

For the last two indicators the following periods were considered:

15 min when the TSO provided data in such resolution.

Hour, meaning a single measurement (hourly resolution) or every set of 4 adjacent values (15 min resolutions).

Day, meaning every set of 24 adjacent hours (e.g. 7h-7h, 8h-8h, 9h-9h,….).

Month, meaning every set of 30 adjacent days (e.g. 1 Jan – 30 Jan, 2 Jan – 31 Jan, …)

6-month, meaning every set of 180 adjacent days

It should be noted that for producing any of the figures within this report, daily, monthly and 6-monthly values were never averaged. Instead, for given time period (e.g. day) all the measurements were considered as a whole (e.g. 24 values for hourly resolution or 96 values for 15 min resolution).


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5. Summary of participation

Points Points

Belgium 9 Algerian 3

Denmark 8 Biomethane 3

France 8 LNG 8

Germany 25 Libyan 1

Hungary 14 Mix 76

Ireland 4 National production 18

Italy 15 Norwegian 4

Netherlands 9 Russian 23

Poland 14 Total 136

Slovakia 4

Slovenia 3

Spain 10

Ukraine 5

United

Kingdom 8

Total 136

In total , input from 17 TSOs across 12 countries was received (Note: introduce the list of

participating TSOs).

It shall be taken into account that the “Mix” category represents points that may receive any

combination of supply sources. This category can be used at Entry point when applicable, but

in general it has been used for exit points.

Points Points

Biomethane injection 3 15 min 37

City gate 55 hourly 99

EU import point 11 Total 136

Industrial - combustion 3

Industrial - non combustion 3

Interconnection point 27

LNG terminal 7

Power generation 4

Production point 6

Transit 14

UGS (underground storage) 3

Total 136


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It shall be recognised that the results of the present report might be influenced by the

selection of the points.

6. Wobbe Index ranges

6.1. By country

Figure 1

The graph above shows WI range information by country. For a given country, the maximum

value represents the highest maximum of all datasets, same applies for 95 percentile;

similarly, the minimum value represents the lowest minimum of all datasets, same applies for

5 percentile.

12.6

13.1

13.6

14.1

14.6

15.1

15.6

16.1

43.0

45.0

47.0

49.0

51.0

53.0

55.0

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

WI Measured ranges by country

Minimum Maximum 5 percentile 95 percentile


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Figure 2

In the map above, the darker the blue is, the lower the Wobbe Index 5 percentile is.

Figure 3

In the map above, the darker the red is the higher the Wobbe Index 95 percentile is.

1Wobbe Index 5 percentile

MJ/m3

(15/15)

52.75

52.00

51.25

50.50

49.75

49.00

48.25

47.50

46.75

46.00

45.25

1Wobbe Index 95 percentile

MJ/m3

(15/15)

52.75

52.00

51.25

50.50

49.75

49.00

48.25

47.50

46.75

46.00

45.25


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6.2. By source

Figure 4

The graph above shows WI range information by type of gas. For a given type, the maximum

value represents the highest maximum of all datasets, same applies for the 95 percentile;


the 5 percentile.

Figure 5

The graph above shows LNG WI range information by country. For a given country, the

maximum value represents the highest maximum of all datasets, same applies for 95

12.6

13.1

13.6

14.1

14.6

15.1

15.6

16.1

43.0

45.0

47.0

49.0

51.0

53.0

55.0

Algerian Libyan LNG Nationalproduction

Norwegian Russian

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

WI Measured ranges by source


12.6

13.1

13.6

14.1

14.6

15.1

15.6

16.1

43.0

45.0

47.0

49.0

51.0

53.0

55.0

France Italy Poland Spain United Kingdom

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

LNG WI Measured ranges by member state



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percentile; similarly, the minimum value represents the lowest minimum of all datasets, same

applies for 5 percentile.

It should be noted that LNG values correspond to send out point of terminals. Therefore, the

WI range of the LNG received by cargo may differ. In addition, the relatively low degree of

utilisation of LNG terminals across Europe in the last two years, which is the period of the

survey, may influence the results.

Figure 6

The graph above shows WI range information for conventional national production by

member state. For a given member state, the maximum value represents the highest

maximum of all datasets, same applies for 95 percentile; similarly, the minimum value

represents the lowest minimum of all datasets, same applies for 5 percentile.

It should be noted that datasets from Ireland correspond to a mixture of imports and national

production.

For more information on gas quality inputs to the EU, please refer to the long-term gas quality

monitoring outlook of ENTSOG.

12.6

13.1

13.6

14.1

14.6

15.1

15.6

16.1

43.0

45.0

47.0

49.0

51.0

53.0

55.0

Denmark Germany Hungary Italy Netherlands Poland UnitedKingdom

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

National production WI measured ranges by member state


https://www.entsog.eu/public/uploads/files/publications/TYNDP/2017/entsog_tyndp_2017_Annex_G_GQA.pdf

https://www.entsog.eu/public/uploads/files/publications/TYNDP/2017/entsog_tyndp_2017_Annex_G_GQA.pdf


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6.3. By type of point

Figure 7

The graph above shows WI range information by type of point. For a given type, the maximum

value represents the highest maximum of all datasets, same applies for 95 percentile;


5 percentile.

Figure 8

12.6

13.1

13.6

14.1

14.6

15.1

15.6

16.1

43.0

45.0

47.0

49.0

51.0

53.0

55.0

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

WI measured range by type of point


12.6

13.1

13.6

14.1

14.6

15.1

15.6

16.1

43.0

45.0

47.0

49.0

51.0

53.0

55.0

BE2

51

BE2

34

BE2

36

DE2

59

DEA

2D

DED

21

DE2

19

DE5

DK

03

2

ES2

43

FR2

52

FR8

24

HU

21

1

HU

31

1

HU

33

2

IE0

11

ITC

46

ITF4

3

ITI1

2

NL1

13

NL3

22

PL3

PL1

4

PL2

1

UA

01

UA

07

BE DE DK ES FR HU IE IT NL PL UA UK

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

WI Measured ranges at exit points by country



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The graph above shows WI ranges for exit points (city gates, industrial consumers, power

generation, transit and UGS point types) grouped by regions (NUTS3 level, which is normally

the province or county).

7. Wobbe Index frequency distribution

7.1. By source

Figure 9

The graph above shows the frequency distribution of WI values for different supply sources.

While several sources are characterized by a narrow WI range (Algerian, Russian, Libyan …), their average values are different. In addition, other sources are characterized by a much wider WI range (national production, biomethane …). As a consequence, the WI range of the gas that is distributed in Europe3 (see “Mix” category) corresponds roughly to the wide EASEE-gas range (46,46 54 MJ/m³).

3 For the points studied in this report

13.2 13.4 13.6 13.8 14 14.2 14.4 14.6 14.8 15 15.2 15.4 15.6 15.8 16

0

10

20

30

40

50

60

70

80

90

45 46 47 48 49 50 51 52 53 54 55

kWh/m3 (25/0)

MJ/m3 (15/15)

Frequency distribution of Wobbe index

Algerian Biomethane LNG Libyan

Mix National production Norwegian Russian


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The following graphs illustrate the relative Wobbe Index frequencies by country. Attention shall be paid to the fact that the following figures have been obtained by averaging all points within a country without taking into account flows.

Figure 10

Figure 11

13.2 13.4 13.6 13.8 14 14.2 14.4 14.6 14.8 15 15.2 15.4 15.6 15.8 16

0

10

20

30

40

50

60

70

80

90

45 46 47 48 49 50 51 52 53 54 55

kWh/m3 (25/0)

MJ/m3 (15/15)

Wobbe Index frequency distributions by country

Belgium Denmark France Germany Hungary Ireland Italy

13.2 13.4 13.6 13.8 14 14.2 14.4 14.6 14.8 15 15.2 15.4 15.6 15.8 16

0

10

20

30

40

50

60

70

80

90

45 46 47 48 49 50 51 52 53 54 55

kWh/m3 (25/0)

MJ/m3 (15/15)

Wobbe Index frequency distributions by country

Netherlands Poland Slovakia Spain Ukraine United Kingdom


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8. Wobbe Index variability

8.1. By source

Figure 12

The graph above shows the probability of different step changes in a period of 15 minutes (data from FR, IE, NL, SK and UK). The probability has been calculated by dividing the number of changes that are bigger than a given threshold (e.g., 0.5 MJ/m3) by the total number of registered measurements. For example, the probability of seeing a change of 0.5 MJ/m3 in 15 min for points supplied with Russian gas is less than 0.01%. When a data series stops at a given point (e.g., Russian stopping at 1 MJ/m3), it means that no changes greater than the next threshold (e.g., 1.5 MJ/m3) have been observed. In general the more the curve is extended to the right, the wider the variations are. The higher the curve, the more frequent the variations are.

Alternatively the graph below shows the probability as individually computed for every single point (only those reported with 15 min resolution data). This analysis shows for example that only 2 points out of 29 registered changes greater than 3 MJ/m3 in a 15 min period.

0.00 0.15 0.29 0.44 0.59 0.73 0.88 1.02 1.17 1.32 1.46 1.61 1.76

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

kWh/m3 (25/0)

MJ/m3 (15/15)

Range of change probability within 15 min

LNG Mix National production Norwegian Russian Algerian


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Figure 13

8.2. By period

Figure 14

The graph above illustrates how the probability of a given change increases with time. For example, in this case, for points receiving different gas mixes, while there are no records of daily changes greater than 5.5 MJ/m3, that threshold may be trespassed if a period of one month is considered.

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 0.15 0.29 0.44 0.59 0.73 0.88 1.02 1.17 1.32 1.46 1.61 1.76

MJ/m3 (15/15)

kWh/m3 (25/0)

15 min probability change (all points)


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The graphs in the following pages illustrate the same phenomenon for the different gas types. In general, they will show more stable behaviour than mixes, which are typically distributed to end users, and which are combining several sources.

Figure 15

Figure 16


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Figure 17

Figure 18


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Figure 19

Figure 20


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Figure 21

The graph below presents a summary of the maximum ranges of change that have been observed among all points, categorised by period and supply source.

Figure 22

Remarkably, only 3 types of gases (Russian, Libyan and Algerian) remain within a 3 MJ/m3 range for the 2 years. Norwegian gas may trespass that threshold on monthly periods while LNG and biomethane may do it within a day.

Gas mixes and national production will have higher variations in any time frame, even overcoming 7 MJ/m3 within a month. Notably, even if each supply source has a quite stable

0

0.5

1

1.5

2

0

1

2

3

4

5

6

7

8

15 min hour day month 6-month 2-year

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

WI absolute maximum (among all points) range of change per time interval and source

Algerian

Biomethane

LNG

Mix

National production

Norwegian

Russian

Libyan


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gas quality, the variations in output quality can be wider and faster than the variations on the sources due to comingling or changes in sources of supply to a particular (exit) point.

Below the same analysis is carried out for all input and exit points separately. It can be observed that while variations at nearly all entry points are within 4 MJ/m3, on exit points, where mixes are distributed, the situation is quite different with much wider short and long-term variations.

Figure 23

Figure 24


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9. Gross Calorific Value

As the main topic under consideration in the standardisation work of CEN is Wobbe Index, the

analysis of GCV has been done on a higher level. This is justified on the fact that, generally, WI

presents greater amplitude of variation.

9.1. By country

Figure 25

The graph above shows GCV range information by country. For a given type, the maximum

value represents the highest maximum of all datasets, same applies for the 95 percentile;


the 5 percentile.

The graphs on 8.2 and 8.3 follow the same approach.

10.2

10.7

11.2

11.7

12.2

12.7

34.9

36.9

38.9

40.9

42.9

44.9

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

GCV Measured ranges by country

Minimum

Maximum

5 percentile

95 percentile


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9.2. By source

Figure 26

9.3. By type of point

Figure 27

10.2

10.7

11.2

11.7

12.2

12.7

13.2

34.9

36.9

38.9

40.9

42.9

44.9

Algerian Biomethane Libyan LNG Nationalproduction

Norwegian Russian

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

GCV Measured ranges by source


10.2

10.7

11.2

11.7

12.2

12.7

13.2

34.9

36.9

38.9

40.9

42.9

44.9

kWh

/m3

(25

/0)

MJ/

m3

(15

/15

)

GCV measured range by type of point



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10. GCV frequency distribution

10.1. By source

Figure 28

11. GCV variability

Figure 29

10.22 10.42 10.62 10.82 11.02 11.22 11.42 11.62 11.82 12.02 12.22 12.42 12.62 12.82 13.02 13.22

0

10

20

30

40

50

60

70

80

90

34.9 35.9 36.9 37.9 38.9 39.9 40.9 41.9 42.9 43.9 44.9

kWh/m3 (25/0)

MJ/m3 (15/15)

Frequency distribution of GCV

Algerian Biomethane LNG Libyan

Mix National production Norwegian Russian

0

1

2

3

4

5

6

7

8

15 min hour day month 6-month 2-year

MJ/

m3

(15

/15

)

GCV absolute maximum (among all points) ranghe of change by time interval and source

Algerian

Biomethane

LNG

Mix

National production

Norwegian

Russian


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12. Conclusions

The data in this survey level includes more than 120 data sets from 17 TSOs across 13

countries. Therefore, the study is considered representative for the purposes of gas

quality analysis.

WI ranges arising from the data collected in the survey show a great variety depending

on the supply source. That variety is also present at exit points, which are very often

supplied with different gas mixes (see Figure 8). While imports to EU may be within a

5 MJ/m3 range, national production includes extremely low values (below 45.7 MJ/m3

4, see Figure 4).

The probability distribution of WI values in a given point of the network is strongly

influenced by the supply source or sources (see Figure 9).

The amplitude of variation for WI will be significantly wider the longer the period of

examination is (see 8.2). Regarding entry points, there is also a strong dependency with

respect to the given supply source. Some of the most relevant ones may be able to

guarantee a narrow range (3 MJ/m3) over time but other sources are within a relatively

wide range (5 MJ/m3). On the other hand, indigenous European production appears to

be linked to the most extreme variations. Finally, (exit) points supplied with mixes of

different gas sources may also be faced with very wide variations (above 6 MJ/m3, see

Figure 22).

GCV ranges present also a wide variety across Europe. Generally speaking the range of

change appears to be slightly more restrained with maximums of 6MJ/m3 for the 2

year period (Figure 29).

Regarding the long term Gas Quality Outlook, the values collected in this survey may

be used to update the input ranges assigned to different supply sources. The data

gathered for biomethane will be used to consider this source independently from

indigenous conventional production.

4 The lowest value in EN 437: Test gases. Test pressures. Appliance categories.

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