Large-scale battery storage systems as a key technology for the energy transition

Large-scale battery storage systems as a key technology for the energy transition
What a sunny Monday in June tells us about the future of the power grid.

Whit Monday, June 6, 2022 - a beautiful sunny and pleasantly windy day. Not only perfect for a holiday walk with the family, but also perfect conditions for photovoltaic and wind power plants, which managed to single-handedly provide all the electricity needed on this day. Around lunchtime, the entire 48.7 GW of electricity needed in Germany was easily covered by the 54.5 GW of solar, wind, biomass and run-of-river power plants. In fact, 5.8 GW more was generated than was consumed.

An impressive sign of the success of the energy transition, isn't it?

Definately, but with a bitter aftertaste. As can be seen in the following chart, renewables were able to completely cover the demand, but conventional power plants such as coal, gas or nuclear power could not be shut down at the same time.

Due to the lack of flexibility of the German power grid and the inertia of the large conventional power plants, which could not be shut down quickly enough, a significant surplus of electricity was produced on this day.

In addition to the 54.5 GW mentioned above, 7.9 GW came from lignite & hard coal, 2.2 GW from nuclear power and even 2.5 GW from the generation of electricity from natural gas, which is currently in very short supply. Thus, Germany produced a surplus of 19.3 GW at that time. This imbalance between electricity supply and demand caused the price of electricity to plummet from around €94/MWh to €-0.08/MWh. Germany thus had to give away electricity to neighboring countries in order to keep the power grid in balance. Only a few hours later at 20.00, as soon as the sun went down, production by lignite had to be ramped up from 6.3 GW to 13.8 GW to now cover the demand. The electricity price rose extremely to € 215/MWh.

Within a few hours, Germany had to give away surplus electricity from renewable sources and then more than double production from lignite to meet demand.
The 06.06.2022 therefore impressively shows the critical problem in the energy transition that still needs to be solved:
The lack of flexibility in the German power grid.

In order to meet the climate target of 80% renewable energy by 2030, it is essential to greatly increase this flexibility and thus prepare the grid for much higher volumes of renewable generation in the future.

How do we increase flexibility?

To effectively balance volatility, the power grid must be able to respond much more flexibly to fluctuating production from renewables in the future. For this purpose Energy storage systems of all kinds become an integral part of the grid. With the help of these systems, the surplus energy on that Whit Monday could have first been absorbed, and then later fed back into the grid, which would have avoided the ramping up of lignite-fired power and the sharp price fluctuations on that day. More on the topic of grid flexibility can be found in the glossary entry "Flexibility (power system)".
One of the key technologies in the field of storage systems that address exactly this problem is large-scale stationary grid-connected battery storage.

These large-scale battery storage systems are, as the name suggests, large-scale battery storage systems that are connected directly to the grid and are often in the 5 - 100 MW range. Due to their high efficiencies (over 90%) and extremely fast response times (full power is available within fractions of a second in case of doubt), these storages are very well suited to compensate for short-term fluctuations in the power grid.

So in the specific case of Whit Monday 2022, the large-scale storage facilities would take advantage of the cheap prices at 12:00 noon to charge up and the expensive prices at 8:00 p.m., once the sun went down, to discharge. Thus, the batteries would absorb the excess energy from renewables and both reduce the price fluctuations on that day and avoid the need to ramp up lignite-fired power plants.
In addition to this market-serving behavior, large-scale battery storage can simultaneously perform other critical grid-serving power system tasks that will keep the future volatile power grid flexible, stable, and secure:

Control energy:
Control energy serves as a reserve to compensate for any fluctuations in the power grid frequency in a short period of time (seconds to minutes) and to maintain the constant frequency of 50 Hertz. Power generation and consumption are then always in balance.
--> Stabilizes the power grid even with a high percentage of renewable generation plants.

Black start capability:
Ability in the event of a complete power failure to rebuild the grid without external power (Many large conventional power plants require power to restart themselves)
--> Backs up the power grid and prepares it for a possible emergency.

Congestion avoidance (redispatch):
Intervention by the grid operator to avoid power overloads in the power grid. Plants are ramped up or down as needed to avoid the overloads.
--> Reduces further physical grid expansion needed and helps evenly distribute load on the power grid. (Reduces the north-south bottleneck, for example).

Reactive power:
Power needed to build our AC grid (build up magnetic fields in transformers, inverters, etc.)
--> Assists in building and stabilizing our power grid.

Electricity trading/balancing of price peaks:
Absorption of electricity when prices are favorable (= often surplus of renewables) and feed-in when prices are high (= often too little renewable energy available).
--> Stabilization of volatile electricity price
--> Increase of flexible use of renewables through intermediate storage.

The fact that large-scale stationary battery storage systems will play a key role in the energy transition due to this possible diversity of grid-serving tasks is also shown by the Fraunhofer ISE study "Pathways to a climate-neutral energy system" of November 12, 2021.
According to the study, it is inevitable to expand the battery storage capacity in Germany to 83 GWh by 2030, almost 200 times the current capacity, and thus prepare the grid for this number of volatile generation plants, if Germany wants to obtain even 65% of our energy from renewable sources by 2030. If the 80% currently planned in the German government's latest Easter package is consequently to be achieved by 2030, this expansion will just have to be accelerated.

Without the flexibilization and stabilization of the German power grid through a strong expansion of large-scale battery storage and other storage systems, a rapid expansion of renewable sources by 2030 will regularly result in days like Whit Monday 2022, when the power grid cannot cope with the demands of fluctuating production and thus cannot effectively use valuable produced electricity as well as jeopardize the stability of the power grid.
However, if we manage to remove the currently still prevailing bureaucratic hurdles in the near future, such as the recognition of the grid efficiency of large-scale battery storage, which are currently slowing down the expansion, we will get a good deal closer to a 100% renewable energy system.

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