Environmental Engineering Reference
In-Depth Information
For example, Denmark currently has a wind energy penetration level of 28 per cent,
although proposals exist for a 35 per cent contribution by 2015, and a 50 per cent
contribution by 2030 (Sorensen et al. , 2004). Spain has a current (2012) wind
penetration of 16 per cent, up from 6.5 per cent in 2004. In Germany, the federal
government has declared that renewable sources shall provide 20 per cent of elec-
tricity needs by 2020. Similarly, in California a standard was passed in 2002 requiring
energy from renewable sources to increase to 20 per cent by 2017.
It remains clear that beyond a certain level, significant levels of wind gen-
eration will impact on system dynamics and, therefore, must affect the manner in
which generating units are scheduled and spinning reserve targets are set and
apportioned across the system. In response to this changing environment many
TSOs and DSOs are introducing new guidelines for the connection of wind power
(EWEA, 2005; Jauch et al. , 2005; Johnson and Tleis, 2005). In order that safe
and reliable operation of the electricity network can be assured, all users of that
network are required to fulfil the requirements of a grid code (see Chapter 4).
The grid code assigns responsibilities to parties and regulates the rights of all those
involved in generation and supply. Some grid codes provide unified requirements
for all generators, while others treat wind generation, for example, as a special case.
The general tone of these documents is that wind turbines should behave in a
manner akin to conventional generation, e.g. predictable and controllable real and
reactive power output. Chapter 4 examined wind generation's potential support
for reactive power and voltage control, required operation under network fault
conditions (fault ride-through), and contribution to transient stability. Here, issues
relating to load-frequency control, reserve provision and longer-term system balancing
will be addressed.
The following section summarises the Irish system and current wind genera-
tion. This will provide useful background for the more generic approach of later
sections, which will draw on examples based on the Irish experience of wind power
integration to date.
5.3.2 Wind power in Ireland
The island of Ireland, comprising Northern Ireland and the Republic of Ireland,
provides an interesting case study to quantify wind variability. Ireland is unusual
in having an excellent wind resource, but limited interconnection with other
power systems. Unlike Denmark or regions of Germany and Spain, with higher
wind penetrations at present, Ireland cannot conveniently exploit external links
for energy balancing and system support. The Irish TSOs therefore have to face,
and solve, a number of operational and planning problems latent in other parts of
the world.
The Northern Ireland power system, operated by Northern Ireland Electricity
(NIE) in co-ordination with System Operator Northern Ireland (SONI), is a med-
ium-sized network comprising 700,000 customers, with a system demand ranging
from a summer minimum of 600 MW to a winter peak of 1,700 MW. The Republic
of Ireland power system is owned by Electricity Supply Board (ESB) and operated
by EirGrid, and the system demand for the 1,900,000 customers ranges from
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