All-island power-system research by EirGrid and SONI

21 Jun 2010135 Views

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EirGrid and SONI’s analysis suggests the island of Ireland will transit to 40pc electricity supply from renewables by 2020, mainly from wind.

Circa 18 months’ research into Ireland’s and Northern Ireland’s power systems, commissioned by EirGrid and SONI (System Operator of Northern Ireland), has resulted in The All Island Facilitation of Renewables Studies, with the prediction that Ireland has the capacity to live up to its targets and transit to 40pc electricity supply from renewables by 2020.

Initiating in 2009, the studies were conducted by EirGrid and SONI in collaboration with consultancy firms Siemens-PTI, Ecar and DigSilent-ECOFYS. In addition, independent Irish wind-energy experts Prof Mark O’Malley of UCD and Peter Harte of SWS Energy were both involved in the process.

The objective of the All Island Facilitation of Renewables Studies was to more fully understand the technical and operational implications associated with high shares of wind power in the all-island power balance.

Commenting on the studies, EirGrid chief executive, Dermot Byrne, said: “Already, at times, the Irish system has been operated with levels of up to 50pc generation from renewables. These studies are the first of their kind and will help enable us to develop operational strategies to achieve Ireland’s renewable energy targets.”

All-island targets

While the Republic of Ireland has set the target of achieving a 40pc renewables contribution to the total electricity supply by 2020, Northern Ireland is also considering a similar policy target. Over the next decade it is predicted that wind farms will be the dominant contributor to Ireland’s renewable-energy portfolio.

But, according to the studies, because wind-turbine generators are connected to the grid using power electronics, their electrical behaviour differs from that of synchronous generators applied in conventional power plants. Wind turbine generators – by replacing synchronous generators – reduce the rotating mass ("inertia") in the system and affect system robustness during and immediately after contingencies, according to the studies.

The researchers studied the system response to various contingencies for 63 combinations of load and generation dispatches, including power exchange with the UK.

Conclusions

The studies pinpoint key issues as the most important, limiting factors for instantaneous wind-power penetration:

– Frequency stability after loss of power generation (for instance unplanned disconnection of a large power plant); and

– Stability after network faults.

Wind-energy challenges

According to the studies, the increasing share of wind power introduces new challenges for security and cost effectiveness of supply. These challenges include:

Electric location of generation: The All Island Power System has been developed  to deliver electricity from large power plants connected at transmission level to customers connected at sub-transmission and distribution level. Wind farms are dispersed across Ireland and connected at sub-transmission and distribution level. The electric location of generation is shifted to these voltage levels.

Spatial location of generation: Historically, the spatial location of conventional plants was historically determined either by the location of the energy resources, such as coal, gas, oil, peat, or by distance to load centres. Consequently, the electricity network was developed to bring the electricity from those plants to customers. Conversely, renewable energy resources such as wind power, are partly located in other parts of Ireland than conventional resources, with longer distances between generation and load centres a consequence.

Carmel was a long-time reporter with Siliconrepublic.com

editorial@siliconrepublic.com