Two case studies of renewable intermittency-Timera

By Paul Homewood

An interesting analysis by Timera of the woeful shortage of back up capacity in Europe, based on German renewables performance:

Two case studies of renewable intermittency

Europe is leading a global push to decarbonise power markets with renewable energy sources. Decarbonisation looks to be a tough but achievable challenge, with wind & solar capacity set to do the heavy lifting.

More than 350GW of new wind and solar is projected to come online across Western Europe over the next 10 years. At the same time, large volumes of dispatchable nuclear, coal & lignite capacity are due to close, at least 40GW by 2023 and 80GW by 2030.

We set out the challenges of such a rapidly changing European capacity mix in a recent article. This highlighted what in our view is a substantial shortfall in flexible capacity investment in order to support growing wind & solar output volumes.

In today’s article we use two case studies to illustrate the flexibility required to support renewable output swings in 2020 compared to 2030. We also consider the assertion that these swings can be supported by electricity storage alone (e.g. batteries).

The full post is here.

Below is the key section. Bear in mind it relates to Germany alone:

Case study 1: Low renewables day

Our two case studies are based on actual recently observed load, wind & solar data in Germany (the 2020 case). We then scale up wind & solar output based on the projected capacity growth required to meet the latest German 2030 renewable policy targets. Chart 3 plots our low renewables case study day.

The dark blue shaded area at the bottom of the chart shows 2020 wind and solar output across a given 24 hour period. The blue line shows power demand. The top blue dashed line on the chart shows the level of installed dispatchable (‘flex’) capacity in 2020 (just under 75GW). In other words there is a comfortable volume of dispatchable capacity to cover low wind & solar output days in 2020.

Now let’s consider 2030. The lighter blue shaded area at the bottom of the chart shows the incremental increase in wind & solar output in 2030. Despite the large increase in nominal renewable capacity, there is only a relatively small increase in output on a low wind & solar day.

In contrast there is a more than 30GW reduction in dispatchable flexible capacity by 2030. Nuclear, coal & lignite closures drag the blue dashed line down to a level that leaves an approximately 500GWh energy shortage across the day. This is the equivalent of 250GW of 2 hour average duration storage.

In practice, only a portion of this energy gap can be plugged by storage. Interconnectors will also play a role, although a relatively high correlation of wind patterns across NW Europe means Germany’s neighbouring markets may be in a similar position. But there is a substantial requirement for investment in new flexible capacity e.g. in the form of batteries, gas peakers and demand response.

As I have been pointing out for a long while, storage and demand supply response (DSR) are of little use in covering for renewables intermittency.

Even if daily supply and demand could be perfectly smoothed within 24-hour periods, Germany would still need to cover for that missing 500 GWh, equivalent to a capacity of 21GW.

Timera sum up:

We do not mean to downplay the role of electricity storage, particularly batteries. Storage is set to play a key role in absorbing excess energy, peak shaving and providing very high speed balancing. But storage is a net consumer (not a producer) of energy and current technology (e.g. 1-2 hour duration batteries) have limited practical application for shifting large volumes of energy.

There is also large potential for broader engagement of the demand side. But the flex characteristics of demand side response are typically similar to storage i.e. shorter duration and at best net energy neutral.

Interconnectors can help shift energy from lower to higher valued locations. But the rapid deployment of renewables across Europe will increasingly see neighbouring countries with correlated tight or oversupplied market balances.

Current policy support across Europe is grossly inadequate to support the required volumes of flex from low carbon sources. Even heroic assumptions on storage, demand response and interconnector deployment do not close the flexibility deficit in markets like Germany.

That leaves conventional gas-fired generation playing a structural flexibility provision role well through the 2030s, albeit at steadily declining load factors. And that is not an outcome that is inconsistent with net zero emissions targets in 2050. Gas generation is effectively buying time for the commercialisation and scale up of low carbon flex capacity such as hydrogen and longer duration storage.

In reality, hydrogen and longer duration storage remain pie in the sky, and certainly not options you would want to build an energy policy around.

Which brings us back to gas.