The strained situation of the European power grid
As can be seen in all the current media, the conflict with Russia is putting the European power and energy network to a severe test. If the conflict escalates further, it is conceivable that not only the heat supply will be affected due to a possible gas shortage in winter, but also that the power supply, which is dependent on Russian gas and coal, will face a major challenge.
Even if it is not obvious at first glance: The extreme electricity price fluctuations and price spikes currently observed are an indication that security of supply is not - yet - at risk. This is because they show, albeit painfully, that the electricity market can ensure that demand is met even in times of fuel shortages by means of appropriate price signals. The signals have an effect not only on the supply side, where available generation capacity is given a strong incentive to maximize electricity production from all remaining sources. The demand side also responds, and electricity consumption is cut in the face of high prices in industry and commerce, and increasingly in households. Thus, price signals make it possible to ensure security of supply, to serve the demand for electricity regardless of price. In expert circles, such a situation is referred to as having "resource adequacy."
But what happens when additional challenges and unforeseen incidents are added to an already tense situation like the one we are currently observing?
Just how sensitively the power grid can react to this is illustrated by an example from 2006, when a normally routine shutdown of just one extra-high voltage line across the River Ems in northern Germany briefly threw the entire European interconnected power grid out of balance and caused it to break up into three separate grids (Western, North-Eastern and South-Eastern Europe). On the occasion of the passage of a large ship, this extra-high voltage line was shut down as planned at the time, but several errors in the calculation of the consequences of the shutdown led to a system crash in which up to 10 million households had no electricity for 30-60 minutes and rail traffic was also massively affected.
If such difficulties coincide with the current tense fuel situation, the power grid faces a real challenge. Especially with the further important expansion of renewable energies for the energy turnaround, which are significantly more volatile and less controllable than conventional large-scale power plants, ensuring supply security in the German power grid is more important than ever before, so that the worst case scenario of a blackout, the complete, large-scale collapse of the power supply, cannot occur.
How Energy storage can avoid the worst case of a blackout
To ensure security of supply, various instances and escalation levels are available in the power grid to avoid the catastrophe of a blackout. Thanks to the high flexibility of energy storage systems, they can make an active contribution to avoiding these worst cases in every instance.
Instance 1: Ensuring security of supply via the electricity market
As described above, the electricity market is the first instance in which differences in supply and demand are balanced out. By using energy storage systems on the market, they can already contribute to security of supply in the first instance.
If, for example, there is a surplus of renewable energies in the grid, the price drops due to the surplus supply. This price signal then allows energy storage to absorb the excess electricity. The opposite case also applies. When consumption is increased and supply is low, the price on the electricity market rises, allowing the energy storage devices to feed in the previously stored electricity and thus make up the difference between supply and demand. This also counteracts in advance a potentially dangerous situation in which a shortage ultimately leads to a drop in grid frequency or even a collapse of the power supply. More information on energy storage trading in the electricity market is available in our glossary entry "Intraday Trading".
In this way, energy storage systems can help to ease critical situations in the electricity market such as the current one, where there are extreme price fluctuations. The dampening of price peaks increases security of supply, as the electricity market gains more safety reserves to be able to meet existing demand at all times.
Instance 2: Dynamic grid support - the control energy
If the market's ability to respond is insufficient or if unforeseen, short-term incidents occur, such as the outage of a large power plant or instabilities in network operation, for example due to the incorrect calculations of line utilization via the Ems described above, control energy is called up by the transmission system operator. Control energy represents an energy reserve to compensate for short-term, unplanned fluctuations between power generation and power consumption.
Due to the fast reactivity of some energy storage systems (e.g. battery storage) and the fact that they can both absorb and feed in electricity, they are particularly well suited for the provision of balancing power. If power needs to be made available to increase the grid frequency, energy storage systems can feed in the stored power. If the grid frequency has to be lowered, the storage unit can absorb and store electricity within a very short time.
In the second instance, energy storage can therefore also actively increase supply security by providing transmission system operators with high-quality balancing energy for dynamic grid support.
Instance 3 - Stabilization of island operations
If the use of balancing energy and other emergency instruments does not succeed in balancing out the fluctuations in the network frequency, the power network can, in the worst case, disintegrate into so-called "islands". As in the case of the incident in 2006, smaller, separate sub-grids are then created in the power grid. In the best case, it is then possible to stabilize the grid frequency in at least some of these "islands". Possible damage caused by the network fluctuations to transformers, lines and consumers can thus be contained and the problem zone causing the problem isolated.
However, since typically some regions produce a surplus of electricity, which is then transported to regions with lower electricity production, balancing the grid frequencies during islanding is a real challenge. For example, in the 2006 example, the islanded grid of Northwest Europe produced a surplus of electricity and had to shed power plants in the short term, i.e., stop their production, to lower the grid frequency and ensure security of supply. South-eastern Europe, however, had a power deficit, so consumers here had to be jettisoned, resulting in a large number of power outages at households and industrial plants.
Energy storage can also provide support in this instance of supply security. Due to the high Flexibility they can stabilize the grid frequency of the island in the island operations and thus prevent drops of plants and especially of consumers.
If, despite all safety measures, the worst-case scenario occurs and the grid frequency of the islands cannot be maintained, a blackout will ultimately result. A total power failure in the affected regions. All generation plants come to a standstill and no consumer is supplied with electricity. The task now is to rebuild small islands of the power grid, restore the grid frequency locally and slowly synchronize these small islands back into a single power grid.
Here, some energy storage devices, especially large battery storage devices, have a rare capability. The black start capability. This means that large-scale battery storage can build up a grid with 50 Hertz frequency and supply consumers with electricity without an initial external power supply. Many of the conventional power plants, such as coal or gas-fired power plants, can only be restarted with an external power supply. Energy storage can therefore provide these power plants with the initial power supply that is critical for start-up, allowing the grid to be built up again bit by bit.
Although there are still some legal hurdles before the black start capability of energy storage can be fully developed, these should be cleared in the next few years.
In all instances of supply security, energy storage systems can make a major contribution to making the German power grid more secure and independent. They can balance supply and demand through market deployment, can respond to short-term and unforeseen incidents by providing balancing power, and can effectively stabilize the grid frequency during islanding and thus prevent blackouts. Even in the event of a blackout, some energy storage systems - particularly large-scale battery storage systems - are able to make a decisive contribution to supply security through their black-start capability by helping to rapidly rebuild the grid.
Energy storage systems therefore not only offer an effective way of making the power grid more flexible and preparing it for the target of 80% renewable power generation in 2030, as described in more detail in our article "Large-scale battery storage as a key technology for the energy transition"but can also stabilize the power grid and thus actively support the development of a secure and, above all, independent power supply.