What happens when the duck curve becomes a canyon?

While it may seem unlikely — given the unending wet winter the UK has just experienced — things are coming up sunny.

New data shows that solar and wind generation are growing faster than ever expected. Much faster. Having hit 1000TWh in just 8 and 12 years respectively, these energy sources have scaled up quicker than any other in history.

Setting aside the caveat that, yes, energy needs have grown considerably since the advent of gas and coal generation, solar and wind are exceeding their historical competitors by some distance.

Yet, despite abundant sunshine, many countries continue to overlook their solar potential. Two-thirds of the world’s countries generate less than 5% of their electricity from solar. The likes of Germany and the Netherlands — neither places you’d think of as especially sun-kissed — are showing that grey skies hold gold too.

The problem, as I’ve outlined before, is more to do with demand: no matter how cheap and powerful and plentiful solar generation gets, you'll still face the fundamental issue that you can't use it when you most need it. Energy demand patterns — as illustrated by the infamous ‘duck curve’ that peaks in the mornings and evenings — mean that solar is least in demand when its supply is at its peak, in the middle of the day.

Moreover, as the broader mix of energy types has diversified in weighting, and solar generation in particular has intensified, that duck curve has taken on the shape of a canyon. This has further challenging implications for managing a green transition, as the steeper canyon walls require solutions that can kick in quickly to meet energy demands. Solutions like burning gas.

So solar’s sprint to 1000TWh is impressive. But this is a marathon.

In fact, there’s a very real chance that the overproduction of solar will result in a shortening of its deployment. Global photovoltaic capacity is predicted to quadruple by 2030, to 3.TW. If surplus solar energy keeps going to waste, appetites for solar will shrink, and decarbonising the grid will be taking a backward step.

To make the most of all of this solar potential, we need to be able to bundle renewable generation with affordable storage.

In California, the fruits of a 10-year storage building effort are bearing fruit. April saw Governor Gavin Newsom announce that installed battery capacity in the state had hit the 10GW mark. All the data from the grid manager — the California Independent System Operator, who in fact coined the ‘duck curve’ term back in 2013 — points in a positive direction and confirms what those of us toiling in storage have been arguing for years. As April rolled over into May, the state’s battery fleet kicked in around 6pm and ran beyond midnight — hitting a 7GW record for most power delivered before 8pm in the process.

California, though, remains an outlier. The richest state in the US is far from representative of the rest of the world. But as both proof of concept, and worthiness of investment, its battery success should be a beacon to leaders seeking a clean, just transition.

Currently, battery energy storage systems tend to be used to balance the grid in real time — integrating renewables into minute-by-minute fluctuations and keeping the grid frequency in check. This is a lucrative business so whilst it is clear longer-term storage, of greater and greater amounts of solar energy will be needed, our batteries and energy storage systems will also require tailoring, more cost effective, and less extractive.

Lithium ion costs are coming down, enabling the sector to meet the demand for more long-term storage (and reduce the need to cast off excess solar power generated, as is currently happening in places like Texas). But our clean energy transition demands further innovation, so that its benefits can be felt beyond the Golden State.