Flexible demand is better than building more generation plant

With fossil fuel generation being shut down, its up to flexible demand to balance the grid – and that’s just what it’s doing.

Over the early May bank holiday weekend, National Grid gave one of its newer acronyms its first outing of the year. On the Saturday, the company issued a Negative Reserve Active Power Margin (NRAPM) system warning. This means there’s a lot of inflexible generation on the system given the expected demand, and there aren’t enough options for turning stuff down.
This was a localised event. Up in Caithness, it was both sunny and windy, and there wasn’t enough capacity in the wires to get the power south. But these warnings can be national in reach. Minimum electricity demand is below 20GW. With up to 8.7GW of inflexible nuclear power stations potentially running, wind exceeding 5GW more than half the time, and another gigawatt of cascade hydro on the system, it doesn’t take much from the solar farms to soak up all the space that would otherwise be left to gas, coal and biomass. According to the University of Sheffield’s pvlive model, the solar output record of 9.4GW was set a year ago, and we’ve installed more capacity since then.

National Grid doesn’t yet know how to run a system that’s just nuclear and renewables. It’s always relied on coal and gas to provide operating margin on a continuous basis – a dial that it can turn up or down at will to keep things level. But fossil fuel generators can only flex when they’re running, and increasingly, they’re not. Fossil load factors may never have been so low.
On the other side of the Irish Sea, the all-island market can now take up to 65 per cent of demand from “simultaneous non-synchronous penetration”, which basically means wind and solar. Eirgrid – which has fewer options than highly-­interconnected rivals in Denmark and Germany – has chalked this up as a world first. This progress is the result of the DS3 programme, which includes measures to bring customer-side flexibility into the energy markets.

There’s a pattern here that we see everywhere. Large-scale growth in renewable resources is accompanied by falling fossil burn, and growing flexibility at customers’ sites. If it weren’t for lingering regulatory fankles, demand response would be the single most important new balancing resource worldwide.

In Britain, one of those fankles is the definition of winter in the triad system, which both pays for transmission networks and reduces the cost of them. With winter declared over on the last day of February, triad management ceased, and the Beast from the East delivered the highest demand of the year on the first day of March.

But note – contrary to the strongly held views of armchair system operators – renewables weren’t idle. Wind (small and large) set a new record of 13.8GW on 1 March, holding steady throughout the day and providing 29.6 per cent of total electricity demand over the 24 hours.

Who cooked Christmas dinner? Since Flexitricity never closes, we can often claim that we did. As millions of ovens warm up ready for roasting, it’s not uncommon for our control room to receive a mid-morning call for reserve power. Last year should have given us a three-in-a-row claim, because Staythorpe CCGT unexpectedly dropped around 430MW at just the wrong moment. But although our fastest sites did respond to a brief frequency wobble, it was no big deal.

The reason? Sunshine. When Staythorpe sat down, PV was rapidly ramping up. Late morning, at peak turkey, solar generation hit nearly a gigawatt. Remember, this was Christmas Day, just after the winter solstice.

This summer, the demand response industry is hoping to set another record, for the largest volume of negative reserve delivered during high renewable periods. Demand Turn-Up, which launched two years ago, is the contract under which energy users can turn consumption up when renewable resources are delivering more than the market could otherwise take.
This will be one of the main jobs of demand response in the future, and is a direct answer to the negative reserve warning we saw over the long weekend. Working across industry, commerce and the public-sector, flexible electricity users are putting green energy to work. This is just as well, because there’s lots of it.