This conclusion comes from an extended technical analysis of the future power system, performed by Ecofys, Siemens PTI, Ecar Ltd and DIgSILENT in collaboration with Eirgrid and SONI engineers as well as using independent Irish wind energy experts Professor Mark O’Malley, UCD, and Peter Harte at SWS Energy.
The Republic of Ireland has set itself a binding target to achieve a 40% renewable energy share of total electricity supply by 2020. Northern Ireland is considering a similar policy target.
Wind power is expected provide the dominant share of the total renewable energy generation.
The All Island Facilitation of Renewables Studies have been commissioned by the Irish and Northern-Irish transmission system operators EirGrid and SONI.
The studies investigated the technical issues specifically around the dynamic and frequency stability associated with an increasing share of wind power in the instantaneous power balance of the system.
Additionally, the studies proposed potential operational metrics to maintain secure and reliable operation of the power system.
Ecofys and consortium members studied the system response to various contingencies for 63 combinations of load and generation dispatches, including power exchange with the UK. In that way the consortium identified and qualified the key issues for reliable operation of the power system.
Conclusions
Two key issues have been identified 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.
For wind power penetrations up to 60-80% of the instantaneous electricity demand potential stability problems can be controlled by applying adequate technical mitigation measures.
A crucial precondition for enabling this operational range is that the power system capability of generators meet pre defined standards in a reliable and consistent manner.
In addition a review of the standard distribution connected generator loss of mains protection is required as well as the ability of generators to deal with large frequency deviations.
The studies suggest that above the 60-80% instantaneous penetration level of wind power has to be temporarily curtailed. Otherwise there is a risk that system stability and, hence, reliability of electricity supply are compromised.
Temporary curtailment of wind farms is associated with losses in energy yield. However, the study indicated that respective yield losses on an annual base are limited. The identified operational range in combination with the highlighted technical improvements will allow meeting the 40% renewable electricity target for the All Island Power System in Ireland.