Enhanced intertrip service backed to save millions in curtailment costs

Four battery developers have teamed up to encourage National Grid Electricity System Operator (ESO) to enhance its intertrip services.

They claim that energy storage can be used to increase intertrip capacity on the network, which would dramatically cut curtailment costs.

A record £920 million was added to customer bills last year to cover the costs of curtailment, with the ESO recently predicting that figure will rise to more than £3 billion by the end of the decade.

In particular, the developers – Eku, Field, Kona and Zenobe – are calling for the ESO to:

• Increase the size of the intertrip capacity procured via the Constraint Management Pathfinder in line with increasingly large infeed losses seen from energising increasingly larger low carbon energy infrastructure.
• Procure more inertia, response and reserve to enable the electricity system to withstand a larger instantaneous loss, allowing an even larger capacity via the intertrip service.
• Apply the intertrip to all storage behind constraints, providing more operational capacity and choice, and only arming batteries when exporting.

The developers claim that using batteries will also allow the ESO to increase existing network capacity.

During thermal constraints in Scotland, the ESO does not currently use the maximum boundary transfer capabilities due to a need to keep reserve capacity, or headroom, on the network.

This means that instead of having the maximum 12GW of capacity the B6 boundary typically operates with a maximum capacity of 5.6GW – which inevitably leads to constraint costs as generators in Scotland are instructed to turn down.

To enable the ESO to maximise use of existing network capacity, the four developers recommend using batteries as a “shock absorber” to import power during high winds and export power during lulls.

They claim this will enable the ESO to keep less reserve capacity at constraint boundaries and increase power flows across them.

The developers have also suggested:

• Pairing storage systems across constraint boundaries to manage imbalances between constrained and unconstrained zones.
• Installing a battery on the demand side of the constraint, directly connected via an intertrip similar to the generation on the other side of the constraint.
• Using battery storage systems as a demand initiation service to operate as a pre-fault service with a battery on standby ready to charge.

Zenobe head of business development Tom Palmer told Utility Week: “In a nutshell, the intertrip gives National Grid the ability to reduce generation very, very quickly in the event of a fault. I think it has been great, but it could be better.

“In its simplest form, what we are calling for is kind of the opposite; it’s the ability to turn generation on very, very quickly in the event of a fault.”

Palmer added: “These solutions that we are pushing for do not really require any technological changes, it’s just using the existing solution in a different way that can save consumers money.”

The developers also claim that expanding the intertrip service in this way would be quicker to implement than current plans to build additional network capacity – specifically the Eastern Green Link projects dubbed “Electricity Superhighways”.

Field technical director Chris Wickins added: “National Grid has plenty of projects in the works. And I don’t think anyone here is saying that we don’t need to build a lot more network, because we do. But hopefully, with our solutions we can avoid building the most expensive bits of the extra network.”

Wickins added that while the first of the Electricity Superhighways is slated to come online in 2030, the energy storage proposal could be up and running three years sooner.

Palmer added: “Let’s face it, it’s really difficult to build network but storage is probably one of the fastest technologies to actually get built and get deployed.

“The bit we can’t evaluate is what the interactions are for National Grid in terms of systems, controls and processes – that’s the bit we need them to do and then the industry is pretty nimble in responding if there’s an opportunity.”

The four developers came together following their individual submissions to the ESO’s Constraints Collaboration Project to explore opportunities for new services that can unlock the value of battery storage to alleviate constraints.

When the ESO published its response to submissions, the developers realised that they had all submitted similar proposals. Therefore, they took the decision to unite in their efforts.

Wickins said that the initial response from the ESO has up until now been “understandably cautious”.

“National Grid are doing a good job on probably one of the hardest electricity systems to operate globally,” Wickins said. “We’re a long thin island grid and that makes it particularly difficult to manage with the amount of renewable energy that we now have. So credit to them.

“But they also have a responsibility to keep the lights on. So I think you would expect some cautiousness.”

He added: “We’re feeling some cautiousness through this exercise. But they (ESO) want to make sure it is genuinely useful and doesn’t cause other problems.

“National Grid are probably the only people that understand it well enough to say whether or not these ideas work.”

Having given initial feedback on ideas submitted, the ESO has commissioned Barringa to carry out a quantitative assessment of the impact of the proposals.

It comes amid concerns that the acceptance of batteries in the Balancing Mechanism is still being held back by the ESO’s fears over their sustained availability across consecutive settlement periods.  

William Stephenson, a senior associate at Aurora Energy Research, recently told Utility Week that the issue may not be resolved until the year after next meaning he is “sceptical” that the ESO will achieve its target of being able to operate the power grid without any fossil fuel generation by 2025.