Distribution scale battery support becomes a realistic option

Saft and ABB have developed the world’s first high voltage Li-ion (lithium-ion) battery backed system designed to improve the stability of power distribution grids. The new system combines dynamic energy storage provided by Saft’s 5.2 kV battery, which will help the distribution system respond to disruptions in the network, with ABB’s SVC (static var compensation) Light technology for dynamic voltage control. ABB’s SVC Light is a power semiconductor technology based on the high power IGBT (insulated gate bipolar transistor), a compact switching device which allows high frequency switching. In combination with dynamic energy storage it will enable simultaneous voltage control and control of active power flow in the grid. The 11 kV pilot system (see below) can deliver 600 kVAr reactive power as well as 600 kW of active power for a few minutes or 200 kW for an hour.

Potential applications include industries with high short term power demands as well as utility grids fed by a high percentage of power from variable renewable energy sources, especially wind power.

However, while current FACTS technology (flexible AC transmission system, currently the standard for AC transmission management) is focused primarily on stabilising grid voltage, the addition of energy storage now broadens its scope to cover short term load or supply variations.

‘The key aim of this project is to demonstrate the feasibility and added value of incorporating Li-ion energy storage within a FACTS system’ said Per Eckermark, head of ABB’s FACTS system group. It could play a vital role in ensuring the stability of utility grids as the penetration of wind power increases.

This is by no means the first such collaboration between ABB and Saft. In September 2003 they brought on line a record-breaking battery energy storage system in Alaska to reinforce the Golden Valley Electric Association grid against power outages. That system was capable of delivering 50 MW for a short time and was based on Saft NiCd rechargeables and a converter designed and supplied by ABB.

Initially at least this new system and others like it will provide considerable levels of grid stability against fluctuations in demand and supply. Their main value is in effect to buy time. However it is not impossible, given the pace of development of battery storage power, that load clipping and other storage functions currently supplied mainly by pumped hydro could fall within the range of battery systems. And more and more such storage is going to be needed in the future as the renewables component in the supply increases, in particular when it reaches that tipping point where significantly increased amounts of conventional back up would be needed, a point generally accepted as being when 20% of capacity is intermittently generated.

Field testing

The two partners are working together in qualification and field testing of the complete system. It has already completed commissioning and bench testing at ABB’s facilities in Sweden, where its performance to specification was confirmed.

The next stage, for competion in 2009, is for an SVC Light with dynamic energy storage to be installed in a field application in order to demonstrate its capability under a variety of network conditions, including operation with nearby wind generation.

Martham pilot project

The first installation of anything near commercial size will be at Martham substation in the UK, and will use a 5.6 kV version of the new high voltage batteries combined with SVC Light, a project on which ABB has been working in collaboration with EDF Energy Networks. A FACTS system incorporating SVC Light with dynamic energy storage in the form of Saft’s new battery will be installed in EDF’s distribution network on the Norfolk coast, an area with a high penetration of wind power, to level out load peaks and improve access to wind power.

The agreed contract amounts to a collaborative research, development and demonstration project in the UK. It will provide dynamic voltage control on an 11 kV distribution system and at the same time enable dynamic storage of surplus energy from wind farms, which can be utilised to level out peaks in grid loading. Using this strategy, the power harnessed from the wind can be put to more efficient use than would otherwise be possible.

The system with its high-tech lithium-ion batteries will be constructed in Hemsby, Norfolk, and connected to the distribution network between Ormesby and Martham. It will be in operation by the end of next year, 2009.

Allan Boardman, EDF Energy Networks planning engineer said: ‘This project will make a difference, because it will allow more renewable generation connections to existing electricity networks, and it will also demonstrate the value of energy storage’.

‘The installation will improve the usability of power from wind farms and avoid the destabilising effect it can have on the grid.’ said Per Eckemark, head of ABB’s FACTS System Group. ‘It will also provide a useful reference project for energy storage’.

ABB and EDF Energy Networks also say that this project, which is being financially supported through industry regulator Ofgem’s Innovation Funding Incentive scheme, is evidence of their commitment to addressing climate change issues by improving network access to renewable electricity production. The benefits may include a reduction in the amount of carbon produced by the UK power industry.