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.

In the event of a major disruption, coordinating responsibility lies with the transmission system operator across regions. Transmission system operators are required to keep grid reconstruction plans available, regularly check them for timeliness and function, and coordinate them with the connected network and relevant plant operators. Network reconstruction begins with producers who have the necessary control capacity, can be deployed from the network operators' control center and thus meet the technical requirements for the fastest possible resupply. Today, these are mostly large power plants, such as gas or hydropower. Renewable energy will be used in the further course of grid reconstruction, depending on the available energy provided today primarily by conventional power plants Standard services. In addition, as the grid reconstruction continues, electricity consumers will be switched on successively and the power grid will thus be rebuilt piece by piece. In doing so, the network frequency must always be kept stable. The network operator coordinates the interplay of electricity production and electricity consumption until the state is completely restored to normal.

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 the 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 off the grid. 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.

In addition, these new plant types must be able to meet the resulting demand for required Balancing power to cover. This is because balancing energy is required to gradually connect producers and consumers during grid reconstruction. If this is not available in sufficient quantity, network reconstruction slows down. Since this balancing capacity is currently largely provided by large conventional power plants such as gas-fired power plants, there will also be an opportunity for new players to take on this role here in the near future.

energy storage Large-scale battery storage systems in general and 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, 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.

What could the role of large battery storage systems look like in a system for market-based procurement of black start capability in the future?

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. 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.