Ireland pursues ambitious target

IRELAND: Anyone who has visited the island of Ireland, especially to the north or west, knows that windy days and nights are the norm.

Built for sharing: An AC/DC converter station at either end of the new Ireland-UK connector will enable bulk power transfer
Built for sharing: An AC/DC converter station at either end of the new Ireland-UK connector will enable bulk power transfer

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Indeed, the island is consistently ranked highly among European nations for its wind resources. Since the same cannot be said of its solar energy and biomass resources, it is no surprise that wind is likely to contribute almost all of the electricity required to meet Ireland's 2020 renewable energy target of around 40% of consumption.

There are two almost entirely separate electricity networks on the island of Ireland, one in the Republic of Ireland (RoI) and one in Northern Ireland (NI). EirGrid manages the former, while System Operator for Northern Ireland (Soni) oversees the latter.

There is little power exchange between the two networks, with just one 500MW interconnector in operation plus a couple of smaller lines. A second 500MW interconnector cable is being considered by planning authorities on both sides of the border. EirGrid and Soni are committed to working jointly and to introducing uniform policies, which over time should make it easier for the two networks to become one.

Interconnection with the British mainland electricity network is also limited, with 450MW flowing from Scotland to NI and 80MW going the other way. But a new 500MW interconnector should be in operation by the end of the year linking the RoI with the UK mainland.

Looking further ahead, additional interconnection between Ireland and Britain and/or France is a possibility, as is direct connection between the British grid and any new offshore capacity built in RoI waters.

The 40% challenge

The all-Ireland energy mix was 64% gas, 16% coal, 12% renewables, 6% peat and 2% oil in 2010. Based on current electricity demand, which has recently declined due to economic contraction, the 40% target equates to about 3.6GW of renewable installed capacity in the RoI and about 1GW in NI. Total installed wind energy capacity stands at about 1.63GW in RoI and 398MW in NI.

The 40% target presents a host of challenges to the grid operators, primarily because achieving an annual average of 40% means there will often be times when a far greater proportion of wind energy will be on the system. Can the networks cope with instantaneous wind-energy penetration at levels of, say, 75% or greater? Currently, EirGrid and Soni limit wind penetration levels to 50% to protect network integrity. They do this by curtailing wind to maintain network stability and replacing it with other flexible resources, primarily gas.

Understanding the hurdles

The grid operators went back to first principles, commissioning research from some of the best minds in Europe to fully understand the technical, operational and policy hurdles as increasing wind capacity connects to the island's grids. This has resulted in a three-year programme, which began in 2011, that will gradually transform how all electricity generators across the island operate and are regulated, and how the networks are managed. "Currently, we won't let wind go above 50% on the network, but we think 75% in instantaneous, real-time penetration is possible," says Jonathan O'Sullivan, EirGrid's manager of sustainable power systems. "We've created the DS3 programme — delivering a secure, sustainable electricity system — whose raison d'être is to do just that."

An initial priority is to improve monitoring of all electricity generators' actual performance and, once the data has been analysed, to set and enforce new grid-code standards. This is essential because greater wind-energy penetration entails an increased risk to a network's dynamic stability and its ability to manage frequency response. One way to minimising such risks is to improve the predictability of generators' output.

While generators are already subject to performance standards, it will become increasingly important for them to meet performance objectives, to communicate with network operators clearly, and "to serve the needs of the system", says O'Sullivan. The introduction of incentives and penalties may be on the horizon.
O'Sullivan sees stronger performance monitoring as the first step towards a full-scale cultural change within the all-Ireland electricity sector. Discussions have recently begun between network operators and electricity generators with a goal of agreeing new grid-code standards over the next three years.

Also on the agenda is a review of the rate of change of frequency (RoCoF) capability of both generators and distribution networks. This is expected to lead to a programme of technical upgrades, which is likely to require wind-farm operators to maximise their RoCoF. This is necessary, O'Sullivan says, because research has clearly shown that without RoCoF improvements, "our capability of controlling voltage and frequency deviation would be comprised in future."

But tighter regulation and technical fixes are not all that needs to change. As the market moves toward unprecedented levels of wind-energy penetration regulators are considering profound changes to the incentives for wind-farm operators.

Serving the system

One question being asked is: instead of using financial incentives to encourage wind-farm operators to generate as much energy as possible as often as possible, why not make use of wind's natural variability to maintain the networks' energy balance? "We are expecting wind farms to run flat out, but they are very good at coming on and off and at maintaining energy balance. They can be part-loaded, but they need to be paid to do so," explains O'Sullivan.

What O'Sullivan is describing implies an overhaul of financial incentives for wind energy, one that would pay operators to provide "system services" in addition to — and sometimes instead of — simply generating electricity. If the goal of 40% renewable electricity by 2020 is maintained, such a radically different approach could simultaneously support increased wind-energy generation and use wind farms to strengthen, rather than threaten, network security. The trick will be to create the right incentives, set at the right price — and that is no easy task.

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