The historical development of Europe’s power transmission infrastructure and its (potential) role in decarbonisation 1900-1921: The establishment of a Verbundsystem to save coal

Author: Thomas Sattich

In the beginning, Europe’s power system consisted of a limited number of small and isolated power plants in major cities such as Berlin or London. Power transmission at that time can be described as low-voltage, fragmented and limited-area distribution, with steam engines at central points, generating the electricity for a few city blocks, with separate circuits for different customers (e.g. street lamps, workshops). But technical developments such as alternating current systems (a.c.), the transformer and the steam turbine soon allowed high voltage transmission and increasing transmission distances (over hundreds of kilometres) at lower losses and costs.

The original power circuits therefore soon expanded from city centres to the suburbs and beyond. Furthermore, technical standardisation (e.g. on grid frequencies and transmission volts) lead to the development of universal systems which unified not only the circuits of individual power stations into one system, but enabled the interconnection of formerly isolated systems of independent companies to more complex networks; moreover, the growing transmission capabilities allowed to connect consumption centres with distant generation units, such as water power sites in mountain areas or thermal plants near coal mines (Hughes 1983:125-129).

With the First World War came fuel shortages and economic nationalism, resulting in state intervention and support for national power pools that interconnect different power plants in one, closed system (Van der Vleuten, Högselius 2012:81). These developments resulted in a meshed network – or grid – which not only connected a (growing) number of consumers, but also different types of utilities that until then functioned independently (Hughes 1983:262). The resulting power pools therefore did not merely provide the growing supply[1] with a broader range of customers, but allowed individual plants, which formerly operated independently from another, to operate in a power pool, with technically and economically interacting components in one single, interconnected system under common control (Ströbele et al. 2012:234).[2]

Hand in hand with the development of this interconnected power pool, technical and political debates began that largely resemble these of today. Rationalization of the power system is the encompassing topic of these debates – back then and today: These debates have been – and again are – based on the fact that interconnected grids not only encourage the exchange of power between power supplier and power consumer, but between different utilities and supply regions, and therefore allow to maximise the use of the existing generation capacity by taking advantage of local differences in peak load and availability of (e.g. at different times). In other words: Interconnection is a prerequisite for maximal rationalisation and economic use of the existing, capital intensive generation infrastructure.

The advocates of large power systems therefore maintain(ed) that costs per unit decrease with the increase of the physical size of the system and a higher load factor. The early debates about the role of power transmission infrastructure in the Verbundsystem hence resemble today’s debate about decarbonisation in five respects: Power transmission infrastructure allows to rationalise the power system by 1) the optimisation of different characteristics of individual power plants; 2) taking advantage of load diversity and demand factors; 3) centralised control of loads and plants in dispatch centres; 4) by better load forecast; 5) lowering installed and reserve capacity (Hughes 1983:370-371).

Intriguingly, the early debate about power transmission infrastructure and the rationalisation of the power system already saw grid expansion as a means to reduce the use of fossil fuels for generation. Main rationale behind this early debate is the fact that interconnected grids not only encourage power exchange between different utilities in order to maximise the use of the existing capacity, but favour more efficient plants; and since coal not only was a scarce and expensive resource in these days, grid expansion constituted a welcome opportunity for system planners to access the huge and so far largely untapped hydropower resources of mountainous areas that were cheap compared to thermal power plants.

But the integration of hydropower into the expanding grid had other advantages, too: As coal supply was considered unreliable due to numerous coal miner strikes access to hydropower also increased security of supply. Moreover, hydropower works complementary and in a symbiotic relationship with thermal power plants, as hydro can provide base load, while thermal power plants (with their ability to respond rapidly to load changes would largely cover the peak loads and times water is in short supply (e.g. at winter times and summer droughts); by night hydropower stations could lower their flow rate in order to refill their water basins, while thermal power plants cover the lower demand at night.[3]

The realisation that power transmission infrastructure not only enables the interconnection of power generation and power consumers, but that the coupled operation of power plants and the complementary use of energy sources allows to combine the different characteristics of thermal and hydroelectric plants on the one hand, different regions on the other, lead to heydays in the technical planning of the future power system. With growing generation capacities and the capability to transmit electricity over larger distances regional power systems, regional power systems flourished during the interwar period, growing into networks that linked cities, towns, and industrial sites.

[1]With the introduction of the steam turbine electricity became available for a much broader range of customers.

[2]One oft he main difficulties in the realisation of such power pools is the agreement on charges for power exchanges between companies independent in terms of ownership rights.

[3]Reversed roles (hydropower for peak, thermal plants for base load is equally possible).


The historical development of Europe’s power transmission infrastructure and its (potential) role in decarbonisation

Author: Thomas Sattich

Still, there is no such thing as the European network Vincent Lagendijk

The role of electricity grids in the power system is largely explained by the fact that storage of electricity is very demanding and costly; put differently: Power generation has to follow changing demand, for example between night and day, or workday and weekend, in order to keep main voltage stable. In order to avoid hazardous fluctuations in the system, system operators therefore keep relatively large and flexible generation capacities in reserve, which the operation of power plants a cost-intensive business. Power transmission infrastructure is one of several ways to optimise this system, as the interconnection of regional subgroups in the power system provides system operators with more flexibility to keep the network stable.

At one end, interconnection helps to limit periods of very low and high demand, as bigger systems feature a flatter load curve than small ones ; on the other, it increases the capacity to react to (local) peak consumption. A more interconnected system therefore helps to limit the need for reserve capacity not only of individual power plants, but of the entire system; Moreover interconnection allows system operators and engineers to obtain a better economic mix between different forms of electricity generation and to make more efficient use individual generation units. The integration of renewables constitutes one of the most dynamic factors in this regard, and hence triggers intensive debates in Europe and elsewhere.

But even though these debates on super-grids, interconnection capacities, grid fluctuations etc. may appear to be of recent date, they are in fact far from being new and date back to the early days of the power system around the late 19th and early 20th century. Of course the power system nowadays is much more complex compared to its beginnings; but many elements of the power system still serve the same purposes. Past debates about the ideal scope of the developing power systems therefore largely resemble today’s deliberations on the role of electricity grids in decarbonisation and the integration of renewables, and therefore provide valuable insights.

This is especially true when it comes to interregional and cross-border interconnection, which did not fundamentally change in their purpose, but still serve the same tasks as 100 years ago. Two items stand out in this regard: Load management on the one hand, and the mix of hydroelectric and thermal power plants on the other. Both date back to the early years of the power system in Europe and still mark two very important cornerstones of the power system. In order to gain a better understanding of the role power networks in EU decarbonisation policy the following section therefore provides a short overview over the historical development of the European power transmission infrastructure, its governance structures, and the development of EU involvement.

The following blog entries aim at a clarification of the power grid’s historical role in the system of power generation, transmission and consumption. This approach is basically based on the assumption, that the early days of a developing system can reveal much about today’s state of affairs: The system may have become more complex, yet it still rests on the same foundations and comparable initial conditions, as 100 years ago. These foundations therefore may be very helpful to understand at what end decarbonisation policy could start to change the system, and what role power transmission infrastructure could play in this process.

Energy dynamics in (Northwest) Europe and Germany’s Energiewende – A think piece

Author: Thomas Sattich

Europe’s energy transition is about to enter a new phase: A turning point has been reached, at which the rapid growth of renewables and the relative decline of traditional energy sources begins to seriously affect the texture of the European energy system. Power generation, distribution, and consumption stands in the centre of this development, as many indicators suggest stronger electrification. A cursory glance at the EU level seems to suggest that the increase of renewables does not interfere with the ability of utilities to keep the pace of growing electricity consumption, as if renewables were a power source just like others. Yet the EU-27 picture is blurred and rather conceals the true dynamics in the European power sector.

These are to be found at deeper layers of the still diverse European power system: Due to a widely meshed infrastructure, the dynamics caused by the introduction of RES are to be observed at the national and regional, rather than at the EU-27 level. Here it is the interface between national power systems, where the most compelling aspects of Europe’s energy transition can be observed, namely the progressive intermingling of different national power systems and markets. Renewables play a key role in this process, as their operation increases the interplay between national systems. Growing swaps of electricity are the result, causing unintended economic and technical consequences, and therefore increasing the demand for regional solutions.

In order to grasp the consequences of RES policy in Europe, four different aspects have to be taken into consideration: 1.) Time: Due to fluctuating natural forces, renewables disrupt the necessary balance between consumption and generation; 2.) Power sources: Once set up, low marginal costs of renewables undercut wholesale prices of other power sources; merit order effects may lead to premature phase-out of gas plants, necessary as flexible backup reserve, while coal plants can still operate under the given market conditions; 3.) Geography: The spatial distribution of RES power stations differs considerably from fossil and nuclear plants; 4.) Market shares: The logic of financial incentives for RES comes with the advantages and disadvantages of industrial policy.

These different aspects of renewables in the power system do not only relate to the national level, but also for the transnational context. For several reasons Northwest Europe is an interesting test case in this regard: 1.) With France and Germany two main players in European energy policy are parts of the region (and seem to pursue opposite approaches when it comes to energy policy); 2.) The North Sea region is a hotspot for renewables and gas alike; in both cases Northwest Europe is representative for the EU-27; 3.) Political negotiations to integrate markets and to update the infrastructure are already relatively advanced (e.g. NSCOGI, Pentalateral Energy Forum) and may serve as an example for other European regions (e.g. the Mediterranean).

Moreover, with strong interactions between the Dutch and German energy system, one of the main axis of market and power system integration in Europe is also part of the region. Yet at this point the varying size of European nations comes into play, as bigger countries tend to disregard their surroundings due to an inward-looking perspective (which can be described as national selfsufficiency), whereas the awareness of smaller nations for their neighbourhood  is better developed. Germany’s neglect of the wider European context during the first years of its Energiewende project can be regarded as a prime example for this phenomenon, and should therefore be studied in greater detail in order to grasp the transnational dimension of RES policy.

The Energiewende’s impact on the regional context should hence be examined on the four above outlined dimensions:

1.) Time: To what extend does Germany’s Energiewende disrupt the balance between consumption and generation in neighbouring countries?

2.) Power sources: In what way does the transition of Germany’s energy sector affect the energy mix of neighbouring countries?

3.) Geography: How does the Energiewende affect the spatial distribution of the regional power system and transmission infrastructure?

4.) Market shares: Does Germany’s energy transition have an impact on the broader economic situation in Europe?

Meaningful results require the assessment of probable trends. Studying the Energiewende’s regional impact therefore also includes the evaluation of the likely course of German energy policy: The “landscape” of German energy policy should be screened for actors who take an active (or passive) position towards the above outlined points; structures between these actors should be highlighted for coherent groups, their position in and their influence on the broader field of German energy policy should be identified (for a possible procedure see:, pp. 10-15). This approach should allow the evaluation of Germany’s future course in energy policy.

Import/Export of electricity in Northwest Europe in 2012 (data source: ENTSO-E)
Import/Export of electricity in Northwest Europe in 2012
(data source: ENTSO-E)

Decarbonisation of Europe’s power sector – some considerations

Author: Thomas Sattich

In October 2009, the European heads of state and government agreed on an ambitious long-term climate policy objective in order to prevent dangerous anthropogenic interference with the climate system and to ensure the European Union (EU) plays its part in limiting global temperature increases to 2°C. Moreover, European policy makers decided to bring the European Union on a demanding decarbonisation path, with the  objective to reduce greenhouse gas (GHG) emissions by between 80 and 95 per cent by 2050, as compared to 1990 levels.

Many decisions taken today influence the EU’s ability to meet these goals. Energy policy is one of the main fields in this regard, as decarbonisation of Europe’s economy in only a few decades implies a major and swift transition of Europe’s energy sector in order to reach almost zero GHG emissions from energy production, transportation and consumption. The electricity sector plays a particular role in this regard, as renewably-generated electricity has to a large extent replace fossil fuel consumption according to the decarbonisation plans.

EU’s energy transition in a nutshell

A look at different reference values of Europe’s energy system reveals remarkable shifts and trends. Most importantly the, the mix of energy carriers which supplies industry, utilities, transport and households with necessary fuels, is in flux and seems to indicate an on-going transition from carbon-based (e.g. coal, gas) to renewable sources (see Fig. 1). If this trends continues, renewables might soon cover a significantly higher share of Europe’s energy mix and deliver a main part of the energy necessary for daily life and business (Commission 2011:5). Increasing depletion of indigenous oil and gas reserves might foster this process.

The greenhouse gas emission intensity of EU’s energy system is following this development and fell of about 9 per cent over the last decade (see Fig. 2). Power generation, distribution, and consumption stands in the centre of this development, as many indicators suggest stronger electrification across the end-use sectors like industry, transport and buildings (Sugiyama 2012). In this segment of the energy system renewables grew of about 70 per cent over the last decade (see Fig. 3). In sum renewables today account for about 20 per cent of electricity generated, which equals the burning of about 409 million barrels (65bn litres) of crude oil (Share of electricity generated from renewable sources in the EU-27 (2011): 20.44 per cent = 670344.108 GWh = 57639218.229 toe = 409.814.841,61 barrel of oil equivalent = 651.553.551.68 l of crude oil (data: Eurostat)) or 4.5 times the world’s daily oil production (BP 2013:8).

Hence, a cursory glance at the EU level might suggest a successful decarbonisation policy. Moreover, figures seem to indicate a relatively smooth integration of renewables into the power system, with no interference of the newly introduced RES power stations with the overall capability of utilities to uphold supply (see Fig. 4 and 5). Yet the trends which seem to underpin such an inference have to be treated with great caution. In fact a deeper analysis shows that Europe’s energy transition is about to enter a new phase in which the rapid growth of renewables and the relative decline of conventional energy sources will probably meet serious constrains (Commission 2013:2).

Greenhouse gas emissions intensity EU-27

The inclusion of RES plants (RES= Renewable Energy Sources, e.g. wind farms) into the existing power system and the alignment of the given infrastructure to their operation is one of the most significant of these constrains. At the bottom of this assumption are some characteristics of renewable energy (see below), which run contrary to the inherited logic of the power system. Further  recourse on renewables therefore will be more than a mere replacement of old power plants, but imply a significant reorganisation of the established system of power generation, distribution and consumption.

Further increase of renewables will hence be constrained by the fact that such a policy  can only partly rely on the established structure of the power system, because the latter is designed for the characteristics of the still largely dominant conventional plants (These include carbon-based power stations (e.g. coal, gas, oil) as well as low-carbon or carbon free plants (e.g. hydro, nuclear).) and not for the operation of some (but not all) forms of electricity generation from renewable sources. The necessary transformation of the power system therefore does not stop at the construction of new power generation units, but implies the necessity to adapt the environment in which these units operate.

Fig. 3: Share of electricity generation from renewable sources in the EU-27 (per cent, data: EUROSTAT)

Yet as the European level in many respects is only the thinnest layer of Europe’s energy system, these constrains for the integration of renewables into the power system mainly relate to the national, not the EU level: Due to limitations in the cross-border power transmission infrastructure, unsolved regulative and technical provisions and the particular nature of electricity as a commodity, lead to a situation where the overwhelming proportion of power is generated and consumed on a national (and subnational, regional) basis: Exchange between the different national systems varies between 7 and 10 per cent and can therefore be described as limited (see Fig. 6).

But even though the cross-border exchange of electricity is still very limited (as are the means of EU-level policy making when it comes to energy), it is nevertheless of great importance for the integration of renewables and will play a key roles in the transformation of the European power system. The question is, how and where decarbonisation (i.e. the increase of renewables) concerns cross-border issues, how the EU could intervene, what measures actually have been taken and envisaged, and whether these are effective and sufficient.

In order to answer these questions, the following section attempts to determine the relation between the integration of renewables into the power system and cross-border power transmission infrastructure in Europe. Regardless of the details, it is obvious that this issue is of great relevance, since it is not only concerns the attempts to decarbonise Europe’s energy system, but touches national sensitivities. Because of it’s strategic relevance, policy makers have to treat the issue of cross-border power transmission with great care when deciding and implementing further decarbonisation initiatives.

Fig. 5: Excess generation in the European Union (per cent; data: ENTSO-E)

Conventional electricity generation, renewables and cross-border power transmission

The existing system of power generation, transmission and consumption is largely defined by so called conventional power plants; these have two main characteristics: Dispatchable generation on the one hand, and centralized generation on the other. Whereas the first item describes the capability to adjust the power output to the system’s varying demand,[1] the second refers to the limited number of central plants which provide the electricity for a (geographically) defined part of the power grid. In both regards some aspects of renewables runs contrary to the logic of the system in which they are supposed to operate;  their integration into the existing power system therefore does not only imply the phase-out of old power plants and their replacement with new ones, but the reorganisation of large parts of the power sector, which is very demanding[2].

By and large the necessary reorganisation process to accommodate large numbers of renewables is defined by the weight of conventional, carbon-based electricity generation plants in the existing system on the one hand, and the specific requirements of power generation from renewable energy carriers on the other. But whereas a definition of the first is relatively easy[1], the term renewables is rather vague description for the true spectrum of technologies which it encompasses.[2] Yet the different forms of renewables impact the power system in very different ways when it comes to dispatchable and centralized generation. Clarity therefore is vital for any further analysis.

For one thing, not all forms of power generation from renewable sources rely on the combustion of energy-rich materials: Only about six per cent of power generation from renewable sources in the EU relies on combustion, with biogas, bioliquids and biomass as energy carriers (see Fig. 6). Regarding dispatchable generation, these should fit relatively well with the established power system, as their output can be controlled and their use should only require slight adaptations of the infrastructure in place. The combined combustion of coal, gas and biomass in modern power plants, or the utilization of the local gas distribution networks  are good example in this regard.

Yet the rest of renewables accounts for forms of power generation, where combustion no longer is the driver of electricity production: Wind, solar and hydro power are the main examples in this respect. In these cases the combustion of carbon-based energy carriers is replaced with wind flows, water streams and solar energy to drive power generation, which is why these forms of electricity do not emit greenhouse gases. This may be the intention behind their introduction into the power system; however, the carbon-neutrality of these technologies comes with a price, as these alternative forms of power generation are not to the same extent dispatchable as conventional (carbon based) power plants.

Put differently: Since the energy which drives these renewables is difficult or impossible to control and varies largely over time (see Fig. 7), the resulting power output equally varies and hardly ever coincides with the momentary demand. Because of the strong variations of wind-, solar- and hydroelectricity, these forms of power generation are therefore also labelled intermittent renewables. But again, there are differences: Whereas (pumped) hydropower stations with a reservoir (hydroelectric dams) are dispatchable by means of the water stream passing through the plant,[3] the same is much less given in the case of tidal, wave and ocean power, where the passage of water is much more difficult to control.

Fig. 6: Share of power generation from renewable sources in 2011 (data: EUROSTAT)

Regarding dispatchable generation, the characteristics of (pumped) hydropower (with reservoir) therefore equal those of conventional carbon-based electricity generation units; its historic role in the power system proves that. The same is, however, not true for other forms of hydroelectricity such as ocean power (see above). But the latter only play a minor role in the power system. The intermittency of wind and solar power otherwise represent one of the main main challenge for the large-scale integration of renewables into the power system, as they can be only insufficiently dispatched to the need of grid operators.

According to the International Energy Agency (IEA) and the European Commission, network balance is considered to be in jeopardy if intermittent renewables exceed 5 per cent in the power system. Whereas the existing power system does not face balancing problems with less than 5 per cent intermittent renewables, more than 5 per cent of wind, solar and intermittent hydropower require measures to ensure grid stability (Commission 2012:8). Yet in 2011 intermittent renewables already amounted to 35 per cent of electricity from renewable sources generated in the EU-27 (compared to 9 per cent in 2002). By 2020 this figure will rise to 49,7 per cent (ECN 2011:14, see Fig. 7).

Fig. 7: Share of intermittent and non-intermittent renewables in the EU (per cent; data: EUROSTAT; 2015, 2020: calculated capacity; data: ECN)

Intermittent renewables therefore already represent about 7 per cent of all electricity (renewable and conventional) generated in the European Union. According to observable trends and the existing national renewable energy action plans, this figure  will rise to about 17-20 per cent by 2020. Without a sufficient infrastructure which provides the power system with the necessary capacity to counter and equalize the erratic ups and downs in the grid caused by intermittent renewables, the further decarbonisation therefore will soon meet serious constrains.

The importance of this growing intermittency in the power system due to increasing numbers of renewables can hardly be overstated, as it not only will progressively disrupt the balance of generation and consumption on the local level, but is also highly relevant for the issue of cross-border power transmission (see below). But there is no one-off measure to tackle the growing intermittency, the actions to be taken will thus include all levels of the power system such as electricity markets, transmission infrastructure and generation. In sum these measures have to provide the system with enough capacity to compensate for the enormous variations of intermittent renewables.

Fig. 8: Wind power generation in Germany, 2012 (source: Fraunhofer Institute; data: EEX)
Fig. 8: Wind power generation in Germany, 2012 (source: Fraunhofer Institute; data: EEX)

Flexible generation (to cover periods of low RES production), storage facilities (to take up RES generation surplus) and power markets which enables the immediate reaction of consumers to the current generation of electricity are the corner stones of this idea. The power distribution and transmission infrastructure interlinks these different parts of the power system; new investments in the grid are therefore widely believed of being vital to achieve the necessary increase in the flexibility of the entire system and hence play an important role in the decarbonisation process.

The adjustment of the grid infrastructure is closely related to the geographical distribution of intermittent RES generation in the power system. In this regard the transition from (carbon-based) conventional to renewables not only results in greater intermittency of electricity generation, but changing locations of the power generation plants: Whereas conventional utilities in most cases are designed as central units which provide the electricity for a large part of the power grid, renewables mostly follow a different approach, with numerous generation dispersed over large territories.

The differences between the two approaches are considerable and do not only relate to intermittent renewables, but with the exception of hydropower all forms of RES electricity generation. Further increasing numbers of renewables therefore imply the necessity to construct new power lines in order to channel the electricity to the consumer. And since the location of new, decentralized renewable generation units on the one hand, and centralized conventional plants on the other can vary greatly, this implies major investments into the power grid.

Yet stronger interconnection is not only supposed to connect RES plants to the power system, but is also expected to provide the system with the needed capacity to react flexibly to the ups and down caused be intermittent renewables. This approach follows three different assumptions:

1) New power lines could connect the power generation with storage facilities such as pumped hydro or power to gas facilities (and these with consumption centres);

2)   together with smart metering and flexible market models an advanced distribution grid could enable the flexible reaction of consumption to changes in the power output;

3)   new power would provide the power system with  more capacity for exchange between different regions with excess electricity/low consumption on the one hand, and such with (currently) low generation/high consumption (or available storage). The more distant the interconnected regions are, and the more efficient electricity transmission, the better the absorption of variations in the grid.

A reorganisation of the power system according to these three assumptions would cover the local, regional, international level alike. With regard to the European dimension, the third seems to be of particular importance, as the still largely national structure of power grids in Europe make more cross-border exchange capacity a convincing but largely untapped possibility for more exchange and network stabilization. The integration of ever growing numbers of intermittent renewables could therefore result in a deeper integration of the European power sector.

Ideas for such a policy are far reaching and include overlay networks  of transcontinental (the ‘super grid’) or regional scope. The per area generation of intermittent electricity (see Fig. 8) is an interesting figure in this regard, as it reveals sharp differences between the single EU member states: Whereas some countries show only a moderate density of wind, solar and tidal power and intend to keep their numbers limited according to the national action plans submitted to the European Commission, others decided to integrate large numbers of these plants into their systems.

Fig. 9: Calculated per area generation of intermittent electricity (solar, tidal, wind), MWh/km² (data: ECN)

With the density of intermittency, the need for deeper interconnection varies – not only on the national but also the European level. It seems therefore certain that the costs and benefits resulting from a policy to increase intermittent renewables by deeper grid integration would be unevenly distributed among the different member states involved (Sattich 2014); any initiative in this direction – be it national or European – therefore demands great sensitivity towards possible economic, technical and political side effects, with the latter as potentially one of the most  serious constrains for any further increase in intermittent renewables in the European Union.


BP (2013). BP Statistical review of world energy 2013. London: BP. Accessed: 24 October 2013.

Desbrosses, Nathalie (2012). Understanding the electrification of industrial energy consumption in europe. Leonardo Energy. 02 July 2012. Accessed: 18 October 2013.

Commission (2011). Executive Summary of the impact assessment. Energy roadmap 2050. Commission staff working paper. Accompanying document to the communication from the commission to the european parliament, the council, the european economic and social committee and the committee of the regions. SEC(2011) 1566 final. Brussels: European Commission.

Commission (2012). Renewable energy: a major player in the European energy market. Communication from the commission to the european parliament, the council, the european economic and social committee and the committee of the regions. COM(2012) 271 final. Brussels: European commission.

Commission (2013). Renewable energy progress report. Report from the commission to the european parliament, the council, the european economic and social committee and the committee of the regions. COM(2013) 175 final. Brussels: European commission.

ECN (2011). Renewable energy projections as published in the national renewable energy action plans of the european member states. Covering all 27 eu member states with updates for 20 member states. Petten: Energy research centre of the netherlands ECN & European environment agency.

ECN (2011). Renewable energy projections as published in the national renewable energy action plans of the european member states. Summary report. Petten: Energy research centre of the netherlands ECN & European environment agency.

Sattich, Thomas (201). Germany’s energy transition and the european electricity market: Mutually beneficial? Journal of energy and power engineering, forthcoming.

Sugiyama, Masahiro (2012). Climate change and electrification. Energy Policy, 44(5), 464-468.

WEC (2011). Global transport scenarios 2050. London: World energy council.

[1] Centralised, dispatchable power generation units, combusting carbon-based energy carriers – principally coal, lignite, natural gas and petroleum products – to drive turbines and generators.

[2] In this regard renewables are similar to conventional plants, which also rely on a broad variety of fuels to produce electricity such as carbon-based, nuclear or hydro energy.

[3] The limited is the available water in the reservoir, which may vary between the different seasons of the year.

[1] Typically the power demand varies significantly between night and day, over the days of the week and the different seasons. Generation has to be adjusted in real time to avoid blackouts (overcharge) or brownouts (voltage drop).

[2] Others would say problematic.