The trial of a 6MW/10MWh ‘Big Battery’ has proven energy storage can help Britain’s electricity network, but the next crucial phase is to assess the business case, the grid operator which commissioned it has said.
Despite the nickname which was picked up by mainstream media, the system is officially titled the Smarter Network Storage project for UK Power Networks, one of the 10 distribution network operator (DNO) companies tasked with keeping the lights on in Britain and Ireland.
“The data acquired, stored and analysed during the 1.5 years of operation have provided invaluable and ‘UK first’ insights in assessing the technical and commercial operation of grid scale storage systems in electricity networks,” Adrian Laguna-Estopier, a consultant at UKPN, told Energy-Storage.News.
UK Power Networks has released a series of reports from the project already, with the most recent, ‘Successful demonstrations of storage value streams’, published in March.
Perhaps fittingly located not far from Bletchley Park, the famous wartime centre of code-cracking in the East of England, the innovative project is trialling the use of lithium-ion batteries to provide a number of grid services. The first, completed phase of testing analysed the provision of single services, the second still to come will combine a number of applications.
System integrator S&C Electric provided the energy storage system (ESS), with batteries supplied by Samsung SDI and a battery management system by Berlin-headquartered Younicos.
System capable of performing in testing
Switched on in 2014, the project has already proven the ESS can provide multiple services to the grid, including solutions to voltage issues at transmission entry points caused by the addition of distributed generation sources, including solar.
Frequency response, keeping the grid at 50Hz, is the most lucrative of those services, and a one there is an increasing need for in the UK, due in part to this addition of DG (distributed generation) and to the closing down of fossil fuel plants.
Smarter Network Storage (SNS) was trialled for different types of frequency response, finding that dynamic firm frequency response (DFFR) could be profitable, as could static (SFFR), but that the lower energy use required in providing the latter made it more so. The degradation of the battery was also thought to be higher on the DFFR trial, although the report states that the economic value of the degradation was not enumerated.
The battery is also suitable for providing a peak shaving service to the DNO, reactive power support at substation level, and to provide short term operating reserve (STOR), another form of TSO grid-balancing that requires active power of at least 3MW to be supplied at minimum two hour output and within 30 minutes of a call from the TSO or aggregator.
Next step: Revenue stream stacking trials
The results so far clearly show that the battery system works in delivering a number of services at both individual user and system level.
UKPN team described the real challenge in terms of economics that the next phase of the trial is to investigate; that such large-scale batteries are only cost-effective if used to provide several different services at once – so-called ‘benefit stacking’ or ‘revenue stream stacking’.
“…A single service provision from energy storage is not economical and investment in storage systems based on current market prices – both in terms of systems procurement and services remuneration – cannot be clearly justified with a single application,” Adriana Laguna-Estopier, one of the report’s authors and a manager for low carbon technologies at UK Power Networks, said.
“The current database comprises of a multitude of data points with large datasets from individual services trials that were completed in March 2016.
Since then, the project has moved into optimised operation that combines different applications to stack services and maximise the value of the storage system.”
Laguna-Estopier said the continued testing will include “new, unproved use cases for energy storage”.
Infrastructure and energy services specialist AMT Sybex provided the Forecasting, Optimisation and Scheduling System (FOSS), software driven controls to the project, adding what Georgina Dingley, a business development consultant at the company calls the “enabling layer” for the storage system to not only execute tasks but to also stack applications.
“The technology for energy storage has been there for a long time in terms of batteries, but this actually unlocks it. Now you can stack revenue streams, now you can use it instead of [paying more for] a network reinforcement. Now you can see it as a viable investment, because you can access all those different things.
Dingle said FOSS, for example, charges and discharges the battery optimally around the commercial needs of the system operator or network, whichever it is called to provide a service to and allowed for a level of detailed scheduling that could make big batteries pay back within as little as three years in some cases.
There are three service beneficiaries to the project: the DNO, the TSO and electricity supplier. The Big Battery is grid-connected in the DNO’s (UK Power Networks’) service area, which sits on National Grid’s transmission system. Meanwhile ancillary services are sold to the grid via an aggregator, Kiwi Power, a company with a background that includes demand response provision.
Electricity is bought and sold by supplier Smartest Energy, which provided arbitrage services under a complex commercial arrangement called tolling. The project found also that while the battery is capable of providing arbitrage services to an electricity supplier to trade in the wholesale market, market design makes this a less profitable application compared to others.
It is not hard to see that with several levels of stakeholder, the issue of what role energy storage, in this case batteries, can play in a reliable, low cost and low carbon future energy network. It appears that from a technical level, it is feasible, as those reporting from the project attest and the results to emerge after the trial’s current phase completes in December will be watched with great interest.
UK Power Networks' Adriana Laguna-Estopier and AMT Sybex's Georgina Dingley will speak about the project among other case studies at Solar Media's Energy Storage Summit this Thursday, 28 April, at Twickenham Rubgy Stadium, London.