The renewable tipping point is here: now we need to focus on flexibility

Richard Molloy, Business Development Manager – Energy Storage, Eaton

We tend talk a lot about tipping points in the energy industry. There’s a tipping point, for example, after which fossil fuel extraction will go into consistent long-term decline, or a possible tipping point for energy subsidies after which they cost more than the economic activity they stimulate, or (perhaps most importantly) a tipping point after which renewables can be seen as our dominant power source.

It can be hard to tell when a tipping point has been reached. For all these examples, there are arguments about when they will happen, what they will look like, or even whether they have already happened. One way of identifying a tipping point, though, might be to notice when the conversation stops debating the idea itself, and starts to deal with all the different things that the idea will affect.

This is, I think, where we are with renewables. Renewable energy is not new: even putting aside millennia of windmill usage, the first electricity-generating wind turbine was constructed in the late 1800s, while efforts to commercialise photovoltaic technology have been underway for more than half a century. For most of this history, the questions have been around viability and feasibility; we have asked whether the technology will work, and whether we can afford to build and operate it. Now, we are thinking in terms of managing and maximising the transition.

The tipping point from whether to how

It has been clear for some time that, in many contexts, renewables have become cheaper per kilowatt-hour than alternative sources, and they already fulfil around a fifth of Europe’s energy demand. An even bigger reason for optimism about the speed of renewable adoption, though, is that we are increasingly talking about what needs to happen when – not if – renewables are supplying sixty, seventy, eighty percent of our power.

While many alternative sources are highly predictable in their output, solar and wind are inherently variable. For solar, we naturally have a daily rise and fall along with the sun, but also a seasonal cycle of sunlight duration and intensity as well as a much more rapid variation when cloud cover and other weather conditions limit production. Wind, of course, fluctuates more dramatically still. Forecasting the variations in output from solar and wind generation has improved dramatically over recent years and continues to increase in accuracy with the application of AI, but even when we know when and by how much outputs will vary, we still need to enable a system response in a fast enough time-frame to manage these changes. When these sources supply some 20% of our needs, fossil fuel plants can be throttled to compensate – but this won’t be possible for a renewable-majority grid.

Perhaps less well known is the challenge that this poses in the other direction. From a grid stability perspective, oversupply is just as much a problem as undersupply, and without a solution in place it’s possible that, by 2040, as much as 16% of Germany’s renewable production will be curtailed. That will mean 2,300 hours a year when potential supply is being wasted even while, at other times of the year, additional sources are needed to manage shortfalls.

Bridging the hills and valleys

All of this means that, as renewables continue their rapid ascent into our energy systems, we need to place our focus on flexibility. Our grid is designed for simultaneous production and consumption, with every watt of supply matched as closely as possible by a watt of demand at all times. In a renewable world, that leads us to needing both back-up generation capacity and costly grid upgrades.

Flexibility will mean decoupling supply and demand through large-scale storage infrastructure. A range of tactics will enable this. For short-term, intra-day fluctuations, integrated battery storage is an ideal way of siphoning off over-production of power and feeding it back in hours later when it is needed.

As the requirement for this kind of flexibility grows, electric vehicle batteries will also play a role. The average EV battery can store enough power for several days of demand from the average European home, and smart charging can delay that demand until renewable supply is abundant – and, for the driver, potentially less expensive. In the future, we will also see vehicle-to-everything solutions sell this stored energy back to the grid when it is needed.

For longer-term storage, possibilities include pumped hydro, compressed air batteries, and green hydrogen. These approaches all offer long-term energy storage with no degradation in capacity over time, making them ideal to smooth out generation gaps which may last weeks or even months.

Decoupling leads to sector coupling

In short, what we think about when we think about renewables now is the prospect of a smart, flexible, multi-directional grid which performs in ways that current infrastructure cannot. It’s not just about replacing our current electricity generation capacity, though: this decoupling of supply and demand will, ironically, also help set the stage for the important work of sector coupling.

While renewable adoption will make much of our daily lives decarbonised by default – from the lights in our homes to, with an EV, our commute to work – much still relies on direct fossil fuel supply. To extend our emissions-reduction efforts to areas like heating, shipping, and the manufacture of goods like steel and chemicals, we need to eliminate their need for fossil fuels.

We can do this by finding ways to link these industries to the grid, in a process known as sector coupling. Shipping, for example, currently relies on highly polluting bunker fuel, and battery technology cannot deliver the power density needed for a cargo ship’s high weight, long range requirements. Green hydrogen, however – either used directly in fuel cells or reformed into ammonia – offers a realistic route to carbon-neutral shipping.

Identifying the tipping point for renewables might feel like an academic exercise, but looking at sector coupling we can start to grasp the importance of flexibility, as a consequence of that tipping point, in our energy systems. It will be the key to unlocking the full potential of renewables for society, and in the process it will make the variability of renewables into an enormous opportunity for our collective future.

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