Wind Power: What impact on the European Grids?

Europe continues to observe a steady growth in wind generation: from 41 GW of installed power in 2005 to more than 67 GW in 2008. Although wind is a great resource for sustainable power, its unstable behavior is also making the existing power distribution networks less easy to manage.

The decentralized nature of wind power comes into contradiction to historical structure for centralized national grids.

Areas for wind turbines implementation are carefully chosen in regard of wind potential, environmental criteria and population acceptance. Few consider proximity to consumer prospects or network characteristics. Consequently issues might show up:

• Long distance transport of electricity, increasing the line losses.
• New projects require building new connecting lines.
• Wind Farms can not always be connected to the transmission network [1,2] which impacts quality information of energy production.
• In case of heavy winds, amount of energy coming from production areas to consumer spots could overheat the transmission lines. When wind generation in north of Germany is important, an great current is transmitted through the South producing undesired network congestions, diminishing cross-border commercial transactions.

The thereafter illustrated figure, presented by ETSO [3], considers the extra flows of power on the European Grid generated during heavy winds in the North of Europe. The scenario is based on a wind production of 80% of total Danish, Dutch and German capacities.

[3]

This phenomenon make some rules appear to be unadapted for wind generation. The “no-limit wind��? policy in Germany for instance didn’t consider the physical properties of European Grids.

Unstable and unforeseen characteristics of wind production make the Transmission System much more difficult to manage:

• Need of side-production capacity or energy storage in order to compensate low level of wind generation.
• Need to balance frequency and offer/demand equilibrium. Wind power does not take part to those mechanisms.
• Need of compensators to regulate reactive power. As the opposite of classic power plants (thermal, nuclear, hydraulic), wind farms (mainly induction generator wind turbine) do not produce reactive power to balance voltage at points of injection.

For all those reasons, above 20% to 30% of total energy mix, wind generation and its fluctuations become really complex to manage. However, dedicated access and management rules could increase the amount of wind capacity a network is able to support without damaging security. Today, three countries reached critical size in matter of wind production:

• in Denmark, total installed power is around 3,1 GW, or 24,4% of the national energy mix, and represents 14,1% in effective daily production[4];
• in Germany, total installed power is around 20 GW (larger wind generation in the world), or 14,8% of the national energy mix, and represents 5,1% in effective daily.
• in Spain, total installed power is around 11 GW, or 14,1% of the national energy mix, and represents 7,9% in effective daily production.

[5]

Incentives for wind are common in those three countries as the obligation for energy providers to cover a ratio of their sales with wind power. However those measures that benefit mainly producers, doesn’t encourage wise management [6]: in Germany, maintenance costs are supported by the TSO, which pass the charges on the transportation fees paid by the end-users and not the producers.

How to improve penetration of wind power?

In order to secure European Grids, coordination between incentives for and limits of wind production is necessary:

• Need for TSO to be able to switch wind power in case of risks.
• Need to replace buy-back guarantee by market mechanism (CO2 quotas, green certificates…) in well wind-supplied countries.
• In parallel, need for producers to support maintenance costs in order to make wind farms more efficient.

The main objective is to implement wind farms not only on locations that are environmentally-advantageous but also by considering network and financial aspects. Such management would increase penetration of wind power and maximize ecological benefits.

Similarly, ETSO[7] likes to insist on the importance to improve cooperation between TSO, investors and regulators during projects in order to manage impacts on the grids. The best would be to define development of wind power in regard with needs and grids.

At the European level, a harmonization of access rules for producers is necessary in order to better distribute wind farms across countries, regions and not only in place where favorable legal environments give enormous advantages for implementation. Indeed, a wide distribution of turbines would reduce significantly global variation in energy production.

Regarding wind farms, access rules should be stricter in order to avoid new wind turbines switching off in case of low frequencies. Technological innovations [8] based on power electronics will soon help to control production and maintain constant voltage remotely.

Toward Smart Grids?

All together, those measures will enforce stronger development of wind power and renewables in general. Technological progress will also take part in the management of wind power. Heavy incentives regarding, for instance energy storage, help positively R&D in the sector. A real-time knowledge of energy flows on the grid and optimization of energy use are keys in grid improvement and are currently developed. Also auto-adjust device will support automation of voltage, frequency and harmonic filtering in the future.

Sia Conseil

Notes:

[1] The transmission system is managed by the TSO, which owns all the High Voltage Lines and balances constantly offer and demand.
[2] The distribution system is managed by DGOs, which owns medium and low Voltage Lines and are in charge to provide electricity to the end-users.
[3]ETSO : European Transmission System Operators association, founded in 1999, represents 35 TSO from 27 countries in Europe.
[4] Average real power generated by wind turbines is approximately equal to 25% of total installed power.
[5] EWIS
[6] Maintenance cost: necessary costs linked to connections, adjustments and back-up capacity costs.
[7] Website of L2EP laboratory from Lille

Sources:

- European Commission
- European Transmission System Operators association (ETSO)
- Ademe
- Council of European Energy Regulators (CEER)