The e-highway2050 scenario development assumes two major policy orientations set at European Union level to shape a challenging 2050 horizon:
reducing GHG emissions between 80-95% by 2050, compared to the estimated 1990 levels,
assuming that renewable energy, energy efficiency and smarter energy infrastructures are “no regrets” technology options for transforming the European energy system in accordance with the three pillars of the European energy policy, viz. ensure security of supply, energy market efficiency and sustainability.
The scenario building approach is a four-step bottom-up filtering process which scans a plethora of possible options and uncertainties, before sorting out the most challenging scenarios to be dealt with by network operators: these are the limiting cases under which they may have to operate the European electricity system.
The first step of the developed scenario building approach sets the foundations for scenario building by answering three questions:
What are the options that decision makers have in hands to shape the energy strategies  in line with the 2050 policy orientations? These options can be technical, socio-economic or political: some of them need R&D investments to clarify and validate candidate options before their real life deployment occurs within a time frame to be defined.
What are the uncertainties that decision makers may have to cope with in order to allow for the proper implementation of the defined strategies? These uncertainties have also a technical, socio-economic or political content: they can impact the R&D investment outputs or outcomes within the same time frame (R&D priorities can also be used to mitigate uncertainties).
What are the boundary conditions that narrow down the options available to build strategies and the uncertainties expected to build possible futures ? These boundary conditions impact the potential of the listed options and futures.
The points of view of all TSOs operating in the 28 Member States (and beyond, e.g. Norway and Switzerland) at the time of performing the analysis (2012/2013) were taken into account, with uncertainties and options ranked according to the following criteria:
an e-Highway2050 scenario is relevant when it challenges the whole European electricity system of today, not only the grid,
the selected e-Highway2050 scenarios should substantially differ from each other, after having accounted for the identified boundary conditions,
some of e-Highway2050 scenarios should challenge the electricity system in a way which differs from what happens today.
Following a workshop with external stakeholders, five futures and six strategies were identified, defining a set of thirty potential energy scenarios which the pan-European transmission network may have to face, see Table 1.
The second step aims at cancelling spurious energy scenarios on the basis of contradictions between the defined futures and strategies. Fifteen scenarios can be cancelled since unfeasible according to the following four criteria, cf. Table 1:
(NUC) scenarios which cannot occur due to conflicts between the public acceptance
of nuclear electricity generation in the futures and nuclear deployment in the strategies,
(CCS) scenarios which cannot occur due to conflicts between the maturity of CCS technology in the futures and CCS deployment in the strategies,
(No-policy) scenarios which are unlikely to occur within a predominantly market-driven future since the corresponding strategy implementation requires a strong policy framework,
(Non-logical) scenarios which are cancelled since a large-scale strategy does not fit in a future with predominantly small-scale local preferences and conversely.
This process leads to a remaining set of 15 possible scenarios as listed in the table below.
Table 1: the 15 remaining scenarios (in green).
Big is beautiful
Small things matter
The third step of the energy scenario selection process aims at:
keeping the scenarios with contrasted impacts on the electricity system, since capturing a wide range of possible situations by 2050, while respecting the boundary conditions of the possible transmission grids under this long-term horizon,
defining the impacts of the different scenarios on the transmission grid, thus identifying possible redundancies between the fifteen remaining scenarios, while considering the opportunity to merge some of them,
supporting transmission network operators at pinpointing the most impacting challenges, where it is assumed that only challenges  coming from generation, demand, and electricity markets (i.e. power exchanges within the ENTSO-E or beyond its borders) are addressed.
Ten parameters were identified as “key parameters” describing the generation, demand and exchange constraints which are imposed on the pan European transmission grid:
1- the level of decentralized renewable energy (generation),
2- the level of centralized renewable energy (generation),
3- the level of nuclear energy (generation),
4- the level of fossil fuel energy (generation),
5- the level of centralized storage (generation and demand),
6- the level of electricity exchanges outside Europe (exchanges),
7- the level of transnational initiatives inside Europe (exchanges),
8- the level of GDP and population (demand),
9- the level of demand according to new uses (demand),
10- the level of energy efficiency (demand)
Analysing the correlations between the remaining options and uncertainties and the above parameters allows answering the following questions:
how much does generation change /where and how is generation changing (spatial distribution and variability)?
how much does demand change / where and how is demand changing (volume and flexibility)?
how do power exchanges within EU-27 member states and with third countries change (internal and external exchanges)?
Finally, a close examination of the remaining scenarios and comparisons with other long-term energy planning approaches
lead to five scenarios in line with the main selection process assumptions.
X5 - Large scale RES deployment: the strategy focuses on the deployment of large-scale RES technologies, e.g. large scale offshore wind parks in the North Sea and Baltic Seas as well as solar projects in North Africa (large-scale PV power for instance). A lower priority is given to the deployment of decentralized RES (including CHP and biomass) solutions. A high priority is given to centralized storage solutions (large-scale storage technologies such as pumped hydro storage and compressed air energy storage) accompanying large-scale RES deployment. Decentralized storage solutions are not prioritized since insufficient to support large-scale RES deployment.
X-10 High GDP growth and market-based energy policies: common agreements/rules have been set for transnational initiatives regarding the functioning of an internal EU market, EU wide security of supply and coordinated use of interconnectors for cross-border flows exchanges in EU. Yet, there is a special interest about large-scale decentralized solutions for RES deployment and storage. CCS technology is assumed mature while electrification of transport (for instance Integration of EVs), heating and industry is considered to occur mainly at centralized (large scale) level.
X-13 Large fossil fuel deployment with CCS and nuclear electricity: electrification of transport, heating and industry is considered to occur mainly at centralized (large scale) level. Energy efficient options (including demand-side management and flexibility of EV use) are deployed only at medium level, mainly aiming at reducing energy demand. No further flexibility is needed since variable generation from PV and wind is low. Public acceptance towards deployment of RES technologies is indifferent in the EU.
X-7 100% RES electricity: in this scenario, Europe's electricity system becomes 100% based on renewable energy. To reach this target, both large scale and small-scale options are used: offshore wind parks in the North Sea and Baltic Seas and projects in North Africa, combined with EU-wide deployment of de-centralized RES (including CHP and biomass) solutions. Neither nuclear nor fossil fuels with CCS are used. Thus, both large-scale storage technologies and small-scale storage technologies are needed to balance the variability in renewable generation.
X-16 Common agreements/rules for transnational initiatives regarding the functioning of an internal EU market, EU wide security of supply and coordinated use of interconnectors for transnational energy exchanges have not been reached. The focus is on local solutions dealing with de-centralized generation and storage and smart grid solutions mainly at distribution level. Due to a somehow heterogeneous European landscape of energy strategies, some Member States still rely on energy imports from outside the EU.
The developed scenarios are used by the e-Highway2050 project as a basis for network simulation tools to propose candidate network architectures which are able to meet a variety of challenges of electricity markets between 2020 and 2050. Beyond the e-Highway2050 project, the bottom-up scenario development methodology can be used in grid long-term planning studies at national or EU levels.
It should be noticed that the e-Highway2050 scenarios are neither predictions nor forecasts about the future. The authors do not conclude that one scenario will be more likely to happen than another, nor that one scenario is more preferred or "better" than another. Rather, each e-Highway2050 scenario is one alternative image of how the future of European Electricity Highways (EHS) could unfold.
 Strategy: a set of different options.
 Future: any combination of uncertainties will create a possible future.
 Thus forgetting about natural hazards and human threats