When the Wind Blows

Analysis and Features

Published on: June 2, 2014 1:26 pmBy: ESJ

A 100MW energy storage plant being built in Northern Ireland by AES will help to balance more wind on the grid

According to the Northern Ireland Renewables Group (NIRG) in December 2013, power generated by turbines regularly contributed upwards of 40% of the local electricity demand. Northern Ireland wants alternative energy – especially on- and offshore wind, which are in abundance – to generate 40% of electricity by 2020. But increasing renewables creates new sets of problems for the grid. So AES is planning to install energy storage at Kilroot, on Northern Ireland’s coastline.

The project will deploy the company’s utility-scale energy storage platform, which is based on six years of piloting and scaling battery-based energy storage and management systems for the grid. The Advancion platform, modular in its architecture, has been designed to replace peaking power plants, which provide power at times of high demand, as well as provide grid services.

AES plans to deploy four 25MW units for the 100MW energy storage facility at Kilroot, one of two power stations that the company owns in Northern Ireland. AES bought Kilroot power station in 1992 when Northern Ireland Electricity was privatised. Based on the shore of Belfast Lough, the plant is a dual coal and oil-fired facility, consisting of two generators, each capable of producing 260MW when firing oil. In addition, the plant has black start capability using two 29MW open cycle gas turbine units, which also provide peaking support for the system.


Shock absorber

The 100MW Kilroot energy storage project will enable more wind power to be fed into the grid. Zero emissions energy generators based on wind, and also solar, produce power intermittently, posing the challenge of how to correlate power generated with demand, in real-time. Energy storage can enable renewable energy resources to act more like fossil fuel-based dispatchable reserves. System operators can turn these up or down, depending on demand. As more renewables are fed into the grid, some dispatchable reserves still have to remain operational – albeit at lower levels – to meet demand at times when the sun is not shining or the wind is not blowing.

‘Like a shock absorber, energy storage systems are able to absorb excess electricity generated by renewable energy plants when demand is lower, taking on the jobs that are most taxing and creating overall system efficiency,’ (John Zahurancik, AES Energy Storage)

The energy storage plant will be used to improve the local grid’s flexibility and lower costs, by balancing demand for electricity with increasing amounts of wind power, helping Northern Ireland to meet its ambitious renewable energy targets. The facility should operational in 2015. AES has submitted a connection application to System Operator Northern Ireland (SONI), which operates the electricity grid in Northern Ireland.

‘SONI pays plants for supplying services that support system security and for their assistance during constrained operations. The AES storage facility will supply these same capabilities but without a minimum generating level or associated emissions,’ says Zahurancik.

As more non-dispatchable energy – in the form of wind and solar – comes online, the value and total need for system support services will increase. By enabling the grid to operate more efficiently, costs associated with running the grid are lowered, by reducing the number of dispatchable reserves that have to remain in operation. The Kilroot energy storage facility will also help to eliminate costs associated with wind curtailment, where wind plant generators are paid for the electricity they produce even if it cannot be sent to the grid because demand does not match supply. In Northern Ireland on average at least 2% of wind is curtailed.

Following initial pilots, AES has developed several utility-scale energy storage units over the past five years. AES has 200MW of energy storage capacity operational or in construction, in countries that include Chile and the US and 1GW in the pipeline.

Much of the company’s installed capacity operates at very high levels of availability to provide critical operating reserves, which are similar to the jobs that will be performed in Northern Ireland. ‘Working with large power system operators, such as PJM Interconnection in the US, AES has tuned the performance and capability of its Advancion storage arrays to meet the demanding reliability jobs needed,’ Zahurancik explains.


Going with lithium batteries

To date AES has used batteries made from lithium chemistries in its energy storage installations, worldwide. For Kilroot the energy storage technology has yet to be finalised, though the characteristics will be similar to those used in other AES systems.

‘We interact with about 150 different technology providers. Battery technologies deployed are certified to work within our Advancion energy storage platform. Even though there are a number of advanced battery technologies that could be potentially deployed for Kilroot, we look for batteries that can be deployed in scale. That is one advantage of lithium batteries today. At the utility level of deployment dependability is critical. Lithium batteries are also very efficient.’

In addition to Kilroot, AES’ pipeline of 1GW of energy storage includes a further 100MW for the PJM Interconnection, which operates the world’s largest competitive wholesale electricity market. AES already has 100MW of batteries connected to the grid in West Virginia and Ohio for the PJM Interconnection. The batteries act as efficient ‘peakers’ competing against all other producers’ generators to provide ancillary services in the wholesale power market, for providing frequency control.

Zahurancik says: ‘For frequency regulation batteries compete with peaking units today but as battery prices come down it opens up other jobs that storage can do. Price decline is an accelerator and will help to expand the use of storage.

For transmission system and grid operators energy storage is becoming a real alternative to building another peaking plant and can provide flexibility instead of keeping minimum base loads of fossil fuel generation switched on, especially as more renewable generation capacity is added.’

In addition to the MWs for PJM Interconnection and for Kilroot, the rest of the pipeline includes projects with utilities and system operators in a number of countries on large-scale storage projects. ‘AES completed its pilot projects in 2007 and 2008 and new projects are generally increasing in size to be comparable to what is typically procured for a peaking generator,’ explains Zahurancik.

In deploying advanced storage at increasing scale, AES has worked to ensure high reliability and dependability at utility scale. For example, the company’s control systems have can claim several years of operational experience within large arrays.

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