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24 June 2021

UK’s smart grid pilot reports findings

The Power Potential project has reported its findings, having run from 14th October 2020 to 28th March 2021. According to participant UK Power Networks, a reactive power market would allow an extra 1.5 GW of renewable capacity to participate on the grid in England’s South East region – quite significant for a region with a population of 9 million.

While private company ZIV Automation developed the control system, both National Grid Electricity Systems Operator (ESO) and UK Power Networks were heavily involved. Predictions made by the National Grid prior to running the pilot saw up to 4 GW potentially enabled in the region.

Duncan Burt, the Director of Operations at National Grid, has called Power Potential “a world-leading project… the first regional balancing market, we think, in the world, where participants and stakeholders will be able to come in and bid services to both UKPN as the Distribution System Operator (DSO) and to National Grid as the System Operator”.

The project involved wind, solar and battery assets across south-east England, organized into a Distributed Energy Resources Management System (DERMS) developed by ZIV Automation. Requirements for participating assets included capacity of over 1 MW, connected at 33 kV or above, with under two seconds reaction time for changes in target voltage set by the control system, and under ten seconds for voltage droop control and power factor control. This portfolio provided reactive power services – stabilizing voltage on the national grid, an increasingly important role as ever more intermittent power sources are added to the grid.

Besides gaining experience on the running of a smart grid, this Power Potential project is a step towards fully commercializing a neglected sector. The ESO will be looking into tapping more reactive power through its Future of Reactive initiative, especially on the south coast.

These initiatives are primarily located in the south of England because that region holds a disproportionate amount of British solar plants, and because it has 2 GW of crossborder connections with continental European power grids, set to rise to 5 GW in future.

It should also be noted that the UK’s demand is slanted towards the south, compared to its sources of power generation more of which are located in the north. In 2014 there was a typical north-south flow of 12 GW, and this has doubtless grown since. Onshore wind will keep increasing this disparity as Scotland has the best natural resource and may reach a generation capacity of 25 GW despite its own demand being under 6 GW.

Unlike active power, the normal electricity transmitted on the grid to be expended by customers, reactive power is first transferred from source to load, then back again. The role of reactive power compensation is merely to keep system voltage within appropriate limits, called voltage droop control by the ESO.

Synchronous condensers, shunt capacitors, inductors, Flexible Alternating Current Transmission Systems (FACTS), and demand response are other ways to handle reactive power services. The Energy Policy Research Group has concluded that a reactive power market would save almost $140 million across Great Britain through to 2050 compared to the cost of investing in traditional devices, though synchronous condensers were included in the Power Potential project.

As with difference in predictions for potentially enabled renewable capacity, the National Grid’s original prediction for monetary savings was $570 million saved nationwide by 2050, far higher than the $140 million touted by UK Power Networks, so perhaps there is some difference in accounting which will be ironed out at today’s “virtual showcase event” to be held online by UK Power Networks.

Yesterday the National Grid made a related announcement: it has begun a power system stability contract which will see two turbines in a natural gas plant – Deeside Power Station – repurposed to provide inertia and reactive power. This will be done without generating any electricity, and is claimed to be a world first conversion of a gas turbine rotor to provide such services.

For its part, UK Power Networks announced in May that it was laying out plans for 2030, for a virtual power station running off EV batteries. It expects that if just 10% of the UK’s 4.5 million EVs at that time participates in that flexibility market, that will amount to a 1.3 GW capacity – but we at Rethink Energy expect the UK to have 7.8 million cars then, so more like 2.25 GW.