Principle relationships between RES-E development and network

The European Commission's Communication on energy infrastructure priorities for 2020 and beyond, adopted on 17 November 2010, called for a new EU energy infrastructure policy to achieve the Eu- ropean energy policy goals. More specifically, the Commission acknowledges the need to extend and upgrade the electricity network to maintain the existing levels of system security, to foster market integration, and especially to balance electricity generated from renewable sources (European Commission, 2011a). While this general formulation of the goal is widely accepted, the optimal way forward to gain a more precise picture of the long-term technical infrastructure requirements, the associated timeframe and the required regulatory measures are less clear. This section is dedicated to address the following questions:

• What are the most important parameters that define network requirements? • Why do European network studies lead to a wide range of results?

• What are the most relevant technological options relevant for the future European transmis- sion grid?

• What are the policy and planning steps necessary?

Important parameters for the definition of network investments

The spatial distribution of generation and load is the most important influencing factor for formu- lating the dimensions of the transmission network. The spatial distribution of RES-E plays an espe-

cially important role and the implementation of cooperation mechanisms between Member States (as discussed in the previous chapter) influences network investments. This can be illustrated with two extreme cases:

1. Transmission network extension will be minimised if Member States rely on their own re- sources to fulfil their renewable energy targets and the location of resources is close to cen- tres of consumption (e.g. small photovoltaics)

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The topic discussed in this section is presented in full detail in the report “Network extension require- ments for an enhanced RES deployment” (D13) (Nabe et al., 2011) available at www.reshaping-res- policy.eu.

2. Transmission network extension requirements will be high if cooperation mechanisms are used in order to exploit RES-E at locations with higher resource potentials (outside national borders) and with higher distance to the load centres (e.g. offshore wind).

Beyond generation and consumption patterns and their spatial allocation, several additional param- eters are relevant for the calculation of transmission investment needs. These parameters can be influenced by energy policy and are discussed in the following paragraphs.

Curtailment of RES-E

The traditional planning approach for electricity infrastructure is based on the view that all gener- ated electricity needs to be transported to the consumer at all times. Additionally, a security crite- rion needs to be fulfilled. This structure is based on the view that it minimises costs, which is true for conventional generation.

For RES-E, with supply-driven feed-in characteristics (wind, PV) this is not necessarily true. The maximum output power is only provided in a few hours each year, so the economic optimum of

network extension might be below the extension required to transport the “last kWh”. This results in a certain curtailment of the energy from RES-E. Taking the long development times and public

acceptance problems of new lines into account, the realistic level of network extension is lower, and the “optimum” curtailment level of RES-E higher than the economic optimum.

Demand-side management (DSM) and electricity storage

Demand-side management (DSM) and electricity storage help to align supply with demand. Hence, these measures also influence load flows and therefore parameters for formulating dimensions of the transmission grid. In which circumstances and to what extent these options can reduce network extension requirements, remains to be shown in detail.

Backup capacities

In order to cover the load at every moment of the year, generation, storage and DSM capacities need to be available. It is a policy decision as to whether the maximum load needs to be covered regionally, nationally or within the whole system. The larger the chosen area for load coverage, the lower the required installed capacities, but the higher the required network reinforcements. A number of factors make the calculation of necessary network reinforcements a difficult exercise:

• The European transmission network is very large (about 10,000 nodes and 14,000 branches for the former UCTE22 system). It needs to be simplified to be able to include it in larger power system models.

• In most parts of central Europe the network is heavily meshed, which creates loop-flows. These loop flows increase the computational complexities of market and network models. Therefore, models operate with very simplified assumptions on network flows.

• Framework conditions such as voltage stability, dynamic stability as well as n-1 or n-2 secu- rity is usually represented in a simplified matter.

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Union for the Coordination of Transmission of Electricity, now ENTSO-E

Phase out of Nuclear Power in Europe

– From Vision to Reality Prerequisites and implications for the European electricity sector

• Input parameters such as long-term primary energy prices for oil, gas and coal as well as prices for future CO2-emission rights are highly insecure.

• Investments in generation and transmission have long lead-times, a long lifetime (20-40 years), and are mostly lumpy and difficult to relocate.

The following sections give an overview of the result of recent studies of transmission extension requirements and give some interpretation of the wide range of results based on the factors previ- ously described.