Black Start Ability


A power plant is described as capable of black starting when, in the event of a power grid failure, it can be restarted completely independently, i.e. without a voltage requirement from outside. The safe and reliable operation of the electricity supply system and thus a secure energy supply is the responsibility of distribution system operators and transmission system operators. In addition, transmission system operators across Europe have measures in place to prevent a grid collapse in critical situations. Despite all these safety measures, a (partial) collapse of the electrical supply network can occur in extreme cases (“power failure”). In this case, the network operators coordinate grid reconstruction using power plants with black starting capabilities.

How are battery storage systems used in the application scenario?

In the future, a new procurement concept for the black start capability system service in Germany is to be developed. This is done against the background of Directive (EU) 2019/944 (Electricity Market Directive), which requires market-based, transparent and non-discriminatory procurement of non-frequency-based system services (NF-SDL). Black start capability is now acquired through bilateral negotiations and contracts. It is therefore primarily about improvements in terms of transparency and non-discrimination. At the same time, a new procurement concept is intended to improve the status quo, particularly in terms of incentives for innovation and investment. Such a procurement concept offers large battery storage systems the opportunity to participate in this market, which is important for security of supply. In addition to hydroelectric power plants or the gas power plants that will not be desired in the future, battery storage systems are almost the only systems capable of black starting. For example, black start capability could be tendered in a standardized process following technical regional differentiation. All systems that meet the minimum requirements for black start systems should be able to participate in these tenders and win the contract after weighing up the price and the technical and systemic benefits. Such a process and the implications described above through the transformation to a sustainable energy supply will promote market development and active competition among all providers of black start capability. In order to be able to maintain supply security in the long term, network operators also need planning security with regard to the available black start systems. This gives large battery storage systems the opportunity to conclude multi-year contracts and thus secure revenues as part of a multi-use strategy.


Which and how many systems are currently capable of black starting?

There are currently 174 black-start plants in Germany with a nominal output of at least 10 MW. In some cases, these are kept as a network reserve for black cases, i.e. they are on call, or they are active and also produce electricity normally. Of these 174 black start plants, only 26 actually have a contractual agreement with the TSOs for network reconstruction. Most of these plants are hydroelectric power plants. Natural gas power plants are also used. However, these conventional power plants and hydroelectric power plants also require a low amount of starting energy (pumped storage power plants, e.g. to control the servomotors to regulate the water flow), which is provided, for example, by local batteries. However, the most important task of black-starting plants is to supply the thermal power plants with the necessary starting power to resume grid operation. For example, large conventional producers also have gas turbines available for black starting.

What does black start ability look like in a renewable future?

As a result of the transformation of the energy system as part of the energy transition, grid reconstruction will be subject to changes in the coming years. On the one hand, more conventional generation plants will come under profitability pressure and go offline. If such conventional power plants capable of black starting are considered solely for black starting capacity on the grid, the costs for the entire system could rise. A market for black start capability should be designed in such a way that an installation remains connected to the grid for black start capability only if it continues to be the most economical option for meeting the given level of safety. These changes in the course of the energy transition create opportunities for grid reconstruction — for example by involving new players and plant types for a black start. Energy storage systems in general and large battery storage systems in particular are therefore a natural alternative: They can be used independently of geographical conditions, i.e. do not need a slope like a pumped storage power plant, for example, and they can deliver large amounts of energy in a matter of seconds at the “push of a button”. Thanks to their multi-functionality, large battery storage systems are able to provide both black start capability and control energy and can therefore make a decisive contribution to security of supply. Large-scale battery storage systems also represent a sustainable alternative to the black start supply: After all, stored solar and wind energy is also used in the black start. This makes it possible to use the entire range of renewable energies also to stabilize and restore the grid. As a technology capable of black starting, large battery storage systems can ideally replace the gaps that arise in black start power plants caused by the disappearance of conventional power plants.

How big is the market for black start power plants?

The market size can be estimated on the basis of the costs associated with black start capability in the BNetzA monitoring report. In 2018, these amounted to 7.4 million euros. According to the study on aspects of electrical system stability in the German transmission grid up to 2023 (RWTH Aachen, 2015), 4.6 GW was contractually bound in 2019 with a potential of over 10 GW of black-starting power plant capacity. According to statements by the transmission system operators and the federal government (in accordance with printed matter 19/16714, 2020), there are currently 26 plants, primarily pumped storage and natural gas power plants, occasionally also hard coal-fired power plants, being contracted by the transmission system operators. There are 174 systems capable of black starting in total, but the majority of them have comparatively low outputs. In coordination with the transmission system operators, the distribution system operators will reserve additional systems for their own applications, such as rebuilding the supply of critical infrastructure. The costs for the latter are passed on via distribution network charges, as the systems are not included in the control-zone-wide reconstruction.