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CAMBRIDGE, UNITED KINGDOM – NOVEMBER 19: A line of electricity pylons crosses the Essex countryside on November 19, 2009 near Cambridge, United Kingdom. As world leaders prepare to gather for the Copenhagen Climate Summit in December, the resolve of the industrial nations seems to be weakening with President Obama stating that it would be impossible to reach a binding deal at the summit. Climate campaigners are concerned that this disappointing announcement is a backward step ahead of the summit. (Photo by Oli Scarff/Getty Images)
Squashing the duck

Squashing the duck

CAMBRIDGE, UNITED KINGDOM – NOVEMBER 19: A line of electricity pylons crosses the Essex countryside on November 19, 2009 near Cambridge, United Kingdom. As world leaders prepare to gather for the Copenhagen Climate Summit in December, the resolve of the industrial nations seems to be weakening with President Obama stating that it would be impossible to reach a binding deal at the summit. Climate campaigners are concerned that this disappointing announcement is a backward step ahead of the summit. (Photo by Oli Scarff/Getty Images)

The explosion in solar power has had some surprising consequences

Renewable energy is going from strength to strength. Full disclosure: I run a clean energy company so I would say that, but don’t take my word for it. Here are some facts: in 2018, 33 per cent of Britain’s electricity came from renewable sources, a fivefold increase over the past decade. Almost a million UK households now have solar panels on their roofs, up from close to zero in the same period.

Globally, BP forecasts that renewables will meet 30 per cent of the world’s energy needs by 2040, three times more than they do now.

Why this story?

At a Tortoise ThinkIn last month on renewables, one of Britain’s leading clean energy entrepreneurs let slip a piece of jargon that encapsulates a serious challenge and grabbed the attention of the room. We asked Good Energy’s Julia Davenport to explain herself.

This rapid growth is necessary and a cause for celebration, but it comes with challenges. One unexpected consequence has been what’s called “the duck curve”, a term first used in California. Millions of households and businesses have installed solar panels across the state, allowing them to generate their own power, feed it into the the grid when they have more than they can use, and cut carbon emissions in the process. But as the acreage of solar panels grew, people noticed something unexpected happening to energy demand.

Desert Sunlight Solar Farm in the Mojave Desert, California

In the past, demand on a graph would look quite predictable: mornings and evenings were the times of short spikes in energy use; daytime was when it plateaued. However, the impact of large amounts of new solar power (and to a lesser extent wind) was to actually reduce demand on the main grid during the middle of the day. The simple reason is that all those solar panel owners were happily using their own power without need for the state’s grid network.

But why a duck? The increase in solar power changed the daily demand curve so that it would sag around midday. At sunset this demand would suddenly pick up as people went home and switched on appliances, and solar power naturally waned. This line appeared to some analysts to look a bit like a duck. See for yourself:

Californian power demand on a typical spring day

The duck curve matters because it poses a risk to grid stability and means we aren’t getting the most out of renewables. In California there have been times when the system operator has been forced to curtail daytime generation as a result of low demand, only to suddenly ramp it up at dusk to accommodate the needs of millions of households. Peak demand often has to be met using using fossil fuel-powered plants that lie idle the rest of the time.

This isn’t an economic or efficient way of running an electricity system. It also makes the job of delicately balancing supply and demand on a second-by-second basis that much harder and riskier.

Electricity transmission grid

The challenge facing the energy industry is to find a way to squash the duck and maximise renewable power when we need it most. And the way to do this is to invest in new smart technologies that create a more flexible system, evening out demand. These technologies include:

  • Better energy storage in the form of batteries. Investment in batteries has grown exponentially in the decade since Tesla reinvented the electric car, helping to bring down costs and creating a global market. Homes can now install large-scale batteries to store power from solar panels on their roofs and use it when they need it.
  • Better energy storage in the form of gas. Instead of charging batteries, renewable power can be used to split water via electrolysis into hydrogen and oxygen, leaving compressed hydrogen as a power source for fuel cells and even domestic heating.
  • Smart meters that can curb peak demand with minimal impact on people’s lives, for instance by switching off domestic freezers for short periods.
Solar panel linked to a Tesla Powerwall

Business interest in battery storage has exploded in the past few years: planning applications for new capacity in the UK soared from 2 megawatts in 2012 to 6,874 megawatts in 2018. The idea is that as these technologies develop, consumer behaviour will adapt so that energy won’t necessarily be used at the time of generation or peak demand. People who aren’t home during the day will store power then and use it later.

And so the duck will be squashed. Sceptics fond of repeating that you can never be sure when the sun will shine or the wind will blow will have their answer. But in the long run the duck curve should be a minor issue for clean technologies with bigger fish to fry. As we move to a low-carbon economy the way we use, manage and generate energy is being completely transformed. Electric vehicles, for example, can be used to both store power and deliver it back to the grid when not in use. As their numbers increase, solar panels will be able to provide charging services, helped by smart meters to collect and communicate data. You’ll always know where to plug in.

Workers install solar panels in Wuhan, China

Current predictions suggest that by 2040, renewables will become the world’s dominant energy source, growing faster than any fuel in history. Solar households will play a huge part in this future and we have to be ready to accommodate them. A great leap forward in energy storage, and smart, digital power demand management, are key to this future.

We have only glimpsed the first signs of solar power’s true potential. If we are up to the challenge then there is nothing to stop this technology from tackling some of the world’s biggest problems, including climate change, head on.

Further reading

  • Rob Gross et al in Science Direct: Can demand response live up to expectations in managing electricity systems?
  • David MacKay: Sustainable Energy – without the hot air
  • California ISO: Electricity 2030 – Trends and Tasks for the Coming Years.

Juliet Davenport is CEO of Good Energy

All photographs by Getty Images