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Analysing the Su�ciency of European Gas Infrastructure - the
Tiger Model
byStefan LochnerDr. David BotheMartin Lienert
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Abstract:
Europe's rising demand for natural gas imports will lead to an increased dependency on thegas infrastructure. Nevertheless, research in this �eld so far lacked a comprehensive modelof the European gas transmission system enabling a full assessment of interdependencieswithin the grid. The Tiger model developed by the Cologne Institute of Energy Economicsin combination with a database containing more than 1000 infrastructure elements allowssuch an analysis. As a dispatch model with monthly resolution, Tiger optimizes the supplyof natural gas to the EU-27 countries plus Norway and Switzerland via the transmission gridusing European production, non-European production injected at border points and LNGimported through regasi�cation terminals. The use of storages further allows intertemporaloptimization. Based on di�erent demand and stress scenarios, the su�ciency of the currentinfrastructure including planned extensions is assessed with a focus on the utilization ofassets, the role of storages and security of supply considerations.
Keywords: Natural Gas, European gas market, modellingJEL-classi�cation: Q41, C61, N74, L95
Contact:Institute of Energy Economics (EWI)University of CologneAlbertus-Magnus-Platz50923 CologneGermanyPhone: + 49 (0) 221 - 170 918 14Fax: + 49 (0) 221 - 44 65 37
1 INTRODUCTION 1
1 Introduction
The European natural gas market is confronted with a number of challenges over the
next decades. First, gas production within the EU has passed its peak and is declining;
second, demand for natural gas is increasing and is expected to continue to do so for
the next decade, mainly in the energy transformation sector. As a consequence of
declining indigenous production and increasing demand, import dependency will rise.
Currently, the EU's major foreign supply countries are Norway, Russia and Algeria.
The main import routes are long-distance transmission pipelines. Although the next
decade might see a diversi�cation of the supply because of increasing Lique�ed Natural
Gas (LNG) imports and infrastructure projects linking other production regions with
the EU (e.g. Iran and Azerbaijan through the Nabucco pipeline project), security of
supply concerns remain.
Possible scenarios for supply disruptions include the drop out of pipelines or capacity
reductions in transit countries due to political disputes (as seen in Ukraine in January
2006) or technical problems on a major import route. To cope with such scenarios, the
European Commission's January 2007 Energy Package demands the identi�cation and
elimination of potential bottlenecks within the European transmission grid and envis-
ages the holding of strategic gas reserves in the long term. Therefore, this paper aims
to analyse the su�ciency of the European natural gas transmission system regarding
the e�ect of planned infrastructure projects and the identi�cation of bottlenecks. To
do so, we will employ Tiger (Transport Infrastructure of Gas with Enhanced Reso-
lution), a dispatch model of the European gas market with monthly resolution and a
time horizon of 10 years.
The paper is structured as follows: The next section summarizes the security of
supply situation for the European gas market over the next decade and section 3
presents the Tiger model, its underlying database and the main assumptions of our
reference run. Some results of our analysis are presented in the subsequent section.
Section 5 o�ers some concluding remarks.
2 Natural Gas for Europe
Two simultaneous developments result in the EU's increasing import dependency -
declining indigenous production and rising demand.
Production is already in the decline in all major production regions within the EU.
Especially the forecasted reduction in the UK's production, which is expected to fall
from current levels of more than 90 bcm per year (in 2005) to between 30 and 40 bcm
by 2025 (Gas Strategies, 2006), will cause total European gas production to decline by
one third over the next two decades. Furthermore, production �elds close to growing
2 NATURAL GAS FOR EUROPE 2
markets will increasingly be used to cover seasonal demand peaks only, something one
can already observe at gas �elds in the Netherlands.
Demand forecasts are shown in �gure 1. Although predicted growth until 2015 varies
depending on the scenario between 12 and 40 percent (from 2006 levels), increasing
demand is predicted by all the studies. All outlooks agree that the major share of
this increase is expected from the energy transformation sector, and that in mature
markets (with some minor expections in South Europe) no signi�cant increases can
be expected from the other sectors. However, while the power sector with its rush for
gas �red plants is believed to be a key driver for future European gas demand, this
sector's development has a great amount of uncertainty attached to it. CCGT plants
are currently favoured by the demand for e�cient and �exible generation capacities
in liberalized markets, �exibility requirements to counter volatile feed-in volumes of
renewable energies and not least due to its low carbon intensity. But all these factors are
ultimately determined by political decisions and given the current uncertainty therefore
do not allow any precise forecasts. Scenario calculations hence vary signi�cantly due
to di�erent assumptions.
Figure 1: Selected demand forecasts for the European market
Comparing these forecasts for European demand and indigenous production draws
the following picture. Declining production and increasing demand lead to rising import
2 NATURAL GAS FOR EUROPE 3
requirements with the EU's import quota increasing from below 60 percent in 2006 to
an average 75 percent in 2020. The development is illustrated in �gure 2.
Figure 2: E.U. import gap
From a security of supply point of view, this raises the question if and how this
increased import demand can be satis�ed. The question whether world-wide reserves
are su�cient to cover the demand can be answered with yes (Bothe/Seeliger, 2006).
Geographically, the EU is in a relative comfortable position. The surrounding regions
including the former Soviet Union (FSU) countries, Iran, Norway and North Africa
(including Nigeria) have known reserves of 150 trillion cubic meters (TCM) which are
accessible today or likely to be so within the next two decades. Discovered resources
which are not economically and/or technical accessible today are believed to exist in
the same magnitude in these regions. The total consumption to be satis�ed with gas
from the named regions until 2030 is estimated at 40 TCM, with the EU's import
requirements in the same time period at 20 TCM. As the mentioned reserves can, by
de�nition, be used economically and technically even today, a physical shortage of gas
in the production regions is highly unlikely in the foreseeable future.
However, physical availability at production sites does not necessary equate to secure
supply in the demand centres. Therefore, an analysis of the transport infrastructure is
required. The increasing demand for imports will lead to a rising utilization of existing
transmission pipelines and LNG import terminals. As of 2005, the import routes from
the EU's major supplying production regions are approaching full utilization (Norway
94 %, FSU 93 %, Africa 100 %). However, a signi�cant number of new infrastructure
projects - or the expansion of existing infrastructure - is being proposed or already
under construction, e.g. the Medgaz pipeline from Algeria to Spain, the Nord Stream
pipeline from Russia through the Baltic Sea to Germany and/or the expansion of the
Yamal pipeline through Belarus and Poland, numerous LNG projects in Italy, Spain,
2 NATURAL GAS FOR EUROPE 4
France, UK and the Netherlands, and amongst others - in the more distant future - the
Nabucco pipeline from Iran and Azerbaijan through Turkey and South-eastern Europe
to Austria and the GALSI pipeline from Algeria via Sardinia to mainland Italy.
On aggregate, it appears that the increase in import capacities in the LNG sector
and regarding transmission pipelines is su�cient to satisfy the EU's rising import needs.
This is illustrated by �gure 3 which shows that even the conservative estimate for total
import capacities is greater than then the highest import-demand forecast for 2010 and
still larger than the average import-demand forecast for 20151.
Figure 3: E.U. import requirements vs. import capacities
However, the �nding that total annual import capacities are greater than the highest
annual demand forecasts does not necessarily allow the conclusion that security of
supply is ensured for all of the EU countries at all times over the next �ve to ten years.
The high seasonal �uctuations of gas demand over the cycle imply that capacities that
are su�cient on average might not be adequate in peak demand times. In a typical
year, up to 13 percent of annual gas consumption in the EU take place in the coldest
month (usually either January or December). Thus, without storages one twelfth of
annual import capacities would need to be able to satisfy one eighth of annual demand.
Looking at the year 2005 in �gure 3 shows that this would not be possible. Thus
storages are important. With a total working volume of 82 bcm in the EU (which
equals the demand of two average months or 1.25 peak months), gas storages appear
to be su�cient to balance seasonal demand �uctuations over the cycle. However, from
1Colors in �gure 3 represent origin of import routes. The di�erences between the optimistic and conservativescenario re�ect di�erent expectations regarding the realization of current projects in terms of date-of-completion andactual capacities and the utilization of LNG terminals.
3 MODEL AND DATABASE 5
a security of supply point of view, they also need to be in the right places.
Furthermore, even when total gas imports and storage capacities are su�cient, bot-
tlenecks in the intra-European gas transmission system might lead to supply shortages
in certain places when demand increases over times. Finally, supply disruptions on
one or more of the import routes lasting just a few days or up to several weeks or
months may or may not occur due to political confrontations, as seen in Ukraine in
January 2006, or technical problems - the consequences of which regarding the security
of supply for the EU are di�cult to determine from aggregated perspective as done
in the previous paragraphs. Therefore, a more thorough analysis of the European gas
transmission system is required. In the following section we will present a tool to do
so in this paper.
3 Model and database
In order to enable an integrated assessment of the di�erent infrastructure components
(pipeline, storages, terminals) and their interaction with regards to a comprehensive
analysis of the supply situation, a new tool was developed. Tiger is a dispatch model
optimizing natural gas supply to all European countries using all available infrastruc-
ture. The latter is stored in a ditto newly compiled database called Edgis (European
Database of Gas Infrastructure).
3.1 The Edgis database
The model requires detailed information regarding the European gas market. These are
obtained from the Edgis2 database. Speci�cally, the database contains the following
elements:
• the European transmission gird consisting of pipelines/networks run by 34 TSOs
and the respective interconnector capacities between the networks, which in total
equates to
• more than 400 nodes and more than 500 pipeline sections (including pipeline
projects being planned or under construction) with their individual characteristics
(diameter, pressure, capacity, length),
• European gas production aggregated to 12 European production regions,
• non-European production from 8 regions which enter the system at its border
points or through Lique�ed Natural Gas (LNG) import terminals,
• 126 gas storage facilities and 17 soon-to-be completed storage projects with indi-
vidual working gas volumes and injection and withdrawal rates,
2Edgis is owned and maintained by the Cologne Institute of Energy Economics (EWI).
3 MODEL AND DATABASE 6
• 22 LNG terminals and terminal projects with individual import, LNG storage and
regasi�cation capacities,
• monthly European gas demand broken down into 44 demand regions and assigned
to individual nodes
• and 57 demand pro�les distinguished by country and sector to allow for charac-
teristic demand cycles in each demand region and di�erent demand growth paths
in the sectors (i.e. power generation and domestic consumers).
In order to provide an easy overview on parameters and to enable a comprehensive
visualization all infrastructure elements are geocoded and can therefore be included
in automatically generated maps. (For an example of the graphical analysis of the
scenario, see �gure 7 in section 4 on page 12.)
Figure 4: European gas infrastructure (pipelines, storages, LNG terminals)
3.2 The Tiger model
Tiger is a dispatch model optimizing natural gas supply to the European market.
As a linear model, it minimizes the total cost of gas supply over the 10 year time
3 MODEL AND DATABASE 7
period it models on a per-month base. Total costs comprise of transport, storage and
production costs. The reason for exogenously including region-speci�c production cost
is to allow the model to choose the cost minimal supply mix for Europe subject to
the gas transmission system instead of pre-specifying the mix of supply countries. The
transport and storage cost components only consist of operating cost. In a dispatch
model, only existing infrastructure or exogenous additions are used, capital costs do
not need to be taken into account.
To realistically model the European natural gas market, the cost minimization is
subject to the following constraints.
Production constraint : For each month, production in a production region cannot
exceed the maximum monthly production (exogenous) capacities in the speci�c region.
Input-output balance : At each of the 400+ nodes in the system, in�ows and out�ows
have to be balanced in each period. In�ows consist of gas transports to the respective
node from other nodes and, if applicable, production at the node or �ows out of storages
or regasi�cation terminals; out�ows equal �ows to other nodes or into storages as well
as demand at the speci�c node.
Storage constraint : The volume of gas in a storage equals its volume in the previous
period plus injections (less compressor consumption) and minus withdrawals from the
storage.
Supply constraint : The total volume of gas supplied to nodes within a demand region
has to equal total demand in that region for each time period.
Capacity constraints ensuring that gas supply is subject to the characteristics of the
European gas infrastructure system apply for all the elements. These constraints are
posed by pipeline capacities, maximum storage volumes and injection and withdrawal
rates and LNG import, storage and regasi�cation capacities. All infrastructure ele-
ments encompassed in Tiger are illustrated in �gure 4.
3.3 Reference Case Assumptions
For the analysis in this paper, we make the following assumptions regarding infrastruc-
ture, production and demand.
Infrastructure data is taken from the Edgis database. All existing pipeline, LNG and
storage capacities are available for usage. For new infrastructure projects, we make the
following conservative assumptions:
3 MODEL AND DATABASE 8
• the �rst line of the Baltic Sea pipeline Nord Stream will go into operation in 2011,
one year later than planned, the second line (proposed for 2012) will not enter
service over the course of the considered time period (up to 2016),
• capacity of the Yamal pipeline will not be expanded,
• the Algeria-Sardinia-Italy pipeline (GALSI) will be available in 2012 (one year
delay regarding the announced date-of-completion),
• the �rst construction phase of the Nabucco pipeline (with capacities of 8 bcm to
Baumgarten) will enter service in 2013 (i.e. with a one year delay) with the �nal
sections in Austria and Hungary only completed in the second half of the year
(1.5 year delay), the second construction phase supposed to more than double
available capacity around 2015 is not considered,
• the Italy-Greece-Interconnector (IGI) will be available in 2012 (one year delay),
• the Baltic-Gas-Interconnector between Germany and Sweden and Denmark is not
considered as the project is currently blocked by the Danish government,
• the Wilhelmshaven LNG project is not considered,
• and the later capacity expansion of the Brindisi LNG terminal (from 8 to 16 bcm)
and the construction of two LNG terminals in the Netherlands will be delayed by
one year each.
Demand is assumed to be equal to the the Gas Strategies Central Case Demand
(GasStrategies, 2006) which is an 'above average' demand scenario (see �gure 1, page
2) assuming an increase in excess of 20 percent over the time period for the selected
countries.
Production capacities for the time period were estimated using the results of the
forecast-model EUGAS (Perner, 2002) and annual production output estimations from
GasStrategies (2006). This allows us to exogenously specify installed capacities in each
year of the optimization. (It is important to di�erentiate between production capacities
and marketed production as production capacities determine peak production while
marketed production is determined by the utilization of production facilities over the
cycle. This is especially important for production regions with high output �uctuations
over the cycle such as the Netherlands.) Production costs are taken from the EUGAS
model as well (Perner, 2002). The only exception is the Netherlands. To model the
declining reserves in Dutch gas �elds which imply a higher value of the remaining gas,
thus allowing producers to charge higher premiums and operate as swing supplier in
time of high demand, a signi�cant mark-up for Dutch gas above production costs is
assumed.
4 RESULTS 9
4 Results
4.1 Reference Run
In the reference run with the above assumptions, there appears to be only one severe
- but on a European level minor - bottleneck. This bottleneck between Sweden and
Denmark is a consequence of the reference case's assumption not to consider any plans
regarding a Baltic-Gas-Interconnector supplying gas from Germany to Sweden due to
a lack of political support from the parties involved at this point of time. (Other
options for gas to Sweden, as a once-proposed LNG terminal near Stockholm or a link
to Russian gas via Finnland or the Nord Stream were not included as they do not
seem any more likely than the BGI.) Therefore, increases in Swedish demand - which
GasStrategies estimates to be as high as 100 percent over the next decade - have to
be solely covered through the existing links from Denmark which current capacities
are not capable of doing. Furthermore, the analysis shows that even increasing this
capacity cannot be the solution as although Danish gas production is su�cient to supply
Denmark and Sweden when considered on an annual level, the two countries lack the
storage capacities to balance out demand �uctuations over the cycle. Therefore, if
Denmark were to remain Sweden's sole gas supplier and Swedish demand would rise as
expected, either storage capacities in the two countries or the reverse �ow capacities
on the Denmark-Germany pipeline (DEUDAN) would have to increase.
Other than that, the European gas infrastructure appears to be su�cient to cope
with average demand scenarios as assumed in the reference run. Even more, LNG
terminals of which there may be as many as 20 by 2013, only show an average utilization
of 41 percent (of 184.8 bcm total capacity) in the same year in a cost minimizing world
(although this �gure will increase to up to 70 percent in winter months, see �gure
5). That shows that this import option is not fully used and allows further imports
to most European countries on this 'route' without further expansions. As for the
Figure 5: Monthly utilization of European LNG import capacities (2013)
4 RESULTS 10
pipeline import routes, existing transmission pipelines from Algeria are fully utilized
during the whole optimization period, new ones (GALSI, Medgaz) as soon as they
enter operation. Norway is operating at or close to full production capacity each year.
Imports from Azerbaijan/Iran after Nabucco goes on line do not play an important role
over the next 10 years - especially as a large part of the Nabucco capacitiy may only
be available towards the end of that time period. In a cost-minimizing environment,
the import pipelines from Russia are not fully utilized as the long-range transport from
the gas �elds in Western Siberia makes Russian gas more expensive than Norwegian
or Algerian imports. However, due to increasing demand, the aggregated �ow through
the three major Russian export pipelines (Yamal, Transgas, Nord Stream (as of 2011))
increases over time. The development of the utilization of these pipelines over the cycle
is illustrated in �gure 6 which depicts the changes between 2008 (without Nord Stream)
and 2015. Noteworthy is that while the utilization of Yamal increases due to improved
connections and rising demand in Germany and Nord Stream is fully utilized all year by
the middle of the next decade, Transgas usage - especially during the summer months
- is cannibalized by the increased usage of the more Northern routes.
Figure 6: Comparison of monthly utilization of import pipelines in 2008 and 2015
To investigate our previous �ndings of future overcapacities into Europe on an ag-
gregated level with regard to the factual infrastructure situation, we modelled an ad-
ditional run leaving out all new pipeline projects mentioned in the previous section
(GALSI, IGI, Nord Stream, Nabucco).
The main results of that alteration of the reference run is that natural gas supplies
to Europe are still secure (regarding the su�ciency of available infrastructure) until
the end of the model time period in 2016. Of course, due to a lack in increased pipeline
capacities, LNG will play a more signi�cant role. However, although total LNG imports
climb by about one third, average utilization of LNG import capacities still remains low
4 RESULTS 11
(below 60 percent on average). Although the alteration meant a reduction of Russian
export capacities by 27 bcm per year, the country's exports decreased by only 9 bcm
per year in 2012. This is a consequence of the previous discovery that these capacities
are not fully utilized in a cost minimizing world.
4.2 High demand case
Di�erent to the reference run, for this scenario we assume that gas consumption in
Europe will increase according the the GasStrategies high case demand. This scenario
predicts a rise of gas consumption in excess of 40 percent until 2015 which is the largest
increase of all aforementioned forecasts (compare �gure 1).
In contrast to the reference run there are now a number of bottlenecks in the Euro-
pean gas pipeline grid. And they are not regionally limited like in the previous scenario
but e�ect most of Western Europe. Remarkably, most of the bottlenecks are at bor-
der points between di�erent networks and not within a network in a speci�c country.
Bottlenecks at border points occur between
• the Netherlands and Germany (Bunde),
• the Netherlands and Belgium ('s Gravenvoeren),
• Belgium and France (Blaregnies/Taisnieres),
• Belgium and Germany (from Eynatten into both, the E.ON Ruhrgas and Wingas
grids),
• Austria and Germany (Oberkappel and Burghausen),
• Spain and Portugal (Badajoz),
• and within Germany at connections between the E.ON Ruhrgas and Wingas grids
(speci�cally in Reckrod).
A graphical illustration of these bottlenecks is presented in �gure 7 (page 12).
Additionally, minor bottlenecks within the domestic grids in Germany, Greece and
the Netherlands interrupting gas supply in some areas occur in our simulation. Fur-
thermore, the issues regarding the supply situation of Sweden described in the previous
section remain. However, total import capacities of the investigated countries do not
seem to be an issue.
4.3 Stress Scenario
From identifying potential bottlenecks in the case of high demand increases in the
previous subsection, we now return to an analysis of the reference demand with a focus
on a stress scenario.
4 RESULTS 12
Figure 7: Bottlenecks at cross-border points in the high demand scenario in 2015
As an example for our investigation, we chose a drop out of the Yamal pipeline in
Belarus after 20113 and focus our analysis on the consequences for the EU without
Poland. The reason is that the case for security of supply within Poland in such a
scenario is fairly trivial and solely depends on storage volumes within the country
at the time. Cross-border capacities with neighbouring countries are by no means
su�cient to satisfy Polish demand over a longer period of time. (However, this may
change when a new link with Northeastern Germany - and thus, access to Nord Stream
supplies - or an aspired pipeline to Denmark or LNG import terminal near Gdansk are
realized.)
For the consequences of such a scenario on the rest of the Europe, in addition to
the duration of the drop out, this largely depends on two factors: (a) the timing of the
incident and (b) institutional requirements regarding storages.
(a) Timing thereby refers to the question, whether the drop out occurs in a period
of high or low demand (i.e. summer or winter). Our analysis shows that such a
situation in the summer months (May to July) can be fairly easily coped with - even
over a longer period of time. The remaining import capacities are su�cient to meet
the demand which would have otherwise been met with volumes transported through
the Yamal pipeline. Even the highly unlikely event of a continued loss of that import
route throughout the winter could be coped with as storages would be �lled su�ciently
in anticipation of the reduced Russian imports during winter. However, if there is no
anticipation of such an event and the drop out were to occur surprisingly during the
winter months, supply shortages in Western Europe would be the result. This assumes3When Nord Stream line 1 is in operation.
4 RESULTS 13
that �rms just �ll their storages to meet the usual winter demand not met through
imports. Reduced imports would lead to shortages. (In the model, this will always
take place due to the cost-minimization approach with perfect foresight.) However, this
looks di�erent if strategic storages were held in each country - as recently proposed by
the European Commission.
Figure 8: Total storage volumes in the EU 2010 to 2015
(b) In 2007, total available storage capacity in the EU countries covered by our model
is 82 bcm. With a mean demand assumption of 560 bcm for the same year, this equals
about 15 percent or less than two average months' demand or less than the demand of
1.25 winter months. As shown in section 2 the import requirements in a peak demand
month (winter) are higher than the maximum monthly import capacities. Therefore,
storages are required to balance demand between summer and winter and cannot be 're-
served' as strategic storages. The Tiger reference run extended to strategic storages
shows that even with perfect foresight, the system could not sustain its equilibrium
(supply equals demand in each demand region at each time) in 2007 as soon as a
strategic reserves-holding obligation in the magnitude of half a month's demand on an
EU level is implemented4. Therefore, in order to be able to use storages as strategic
storages, an increase in either working volumes of storages or import capacities is nec-
4Such obligations on a national level would be even less possible as storage capacities are not equally (i.e. relativeto gas demand) distributed among the member states.
5 CONCLUSION 14
essary. Again, as observed in section 2, the increase in import capacities actually takes
place. Therefore, instead of looking at 2007, we will look at the situation after Nord
Stream went into operation. The analysis now yields that holding minimal reserves
requirements (0.5 average months' demand) will be possible without destabilizing the
system. Storage volumes with and without minimum reserves requirements are illus-
trated in �gure 8. Now, returning to our scenario, if Yamal drops out in winter leading
governments to lift the reserves requirements and 'freeing' stored gas volumes, demand
shortages will not occur5. Figure 9 shows how storage volumes evolve in such a scenario
of a Yamal drop out for up to three months starting November 2012. The signi�cant
reductions in storage volumes (of roughly 50 bcm) until February 2013 demonstrate
that such an incident could not have been compensated in a model world without min-
imum reserves (compare �gure 8 where, without minimum reserves, winter storages
volumes are much lower than in this case required, even on an aggregated level).
Figure 9: Total storage volumes 2011 to 2013 in case of import pipeline dropout
5 Conclusion
Declining indigenous production and rising demand will cause Europe's import depen-
dency in natural gas to rise over the next ten years. In this paper, we use the features
and potential of a newly developed model, Tiger, in order to assess this situation in
detail regarding the su�ciency of available gas infrastructure. With more than 1000
infrastructure elements, the dispatch model uses a realistic representation of the Euro-
pean gas infrastructure including all production and demand regions, all major existing
and planned transmission pipelines, storages and LNG import terminals. Optimizing
5At least if that happens before 2014 in our simulation. After that, demand is too high but storage projects not yetincluded in our model will likely have been completed.
Bibliography 15
natural gas supply to Europe taking these elements into account, we �nd that - with
a few exceptions - current European infrastructure is su�cient to meet rising demand
according to an average growth forecasts over the next decade. Furthermore, we have
shown that with the extensions to the grid planned within the next �ve years, Europe
will be in a position to partly use its current seasonal storages as strategic storages
which would then be able to secure European supply in the event of an extended drop
out of one of the major import pipelines in peak demand times. When assuming very
high demand growth over the next ten years, a few bottlenecks in the European gas
grid will become critical. However, the majority of them is at border points between
di�erent national or intra-national transmission systems meaning that security of sup-
ply in times of high demand or supply interruptions could signi�cantly be improved by
increasing these transfer capacities.
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Perner, Jens (2002): Die langfristige Erdgasversorgung Europas - Analysen und Simula-tionen mit dem Angebotsmodell EUGAS. Schriften des EnergiewirtschaftlichenInstitutes, Band 60, Munich.
