On April 28, Spain suffered the worst
nationwide blackout in Europe in nearly 20 years, with 60% of the country's
electricity supply lost in just 5 seconds. This catastrophic blackout not only
plunged 50 million people into darkness, but also exposed the deep-seated
contradictions in Europe's energy transition. It is particularly noteworthy
that this is the first time in the world that a "black start" has
been attempted with such a high proportion of renewable energy - rebuilding the
entire power system from scratch.
Black Start: The Resurrection of Power System
Black Start is one of the most complex and challenging emergency operations in the power industry. It refers to the process of gradually restoring power from scratch when the power grid is completely paralyzed and all power plants are shut down. This concept stems from a fundamental contradiction in the power system: power generation requires electricity. The vast majority of power plants - whether coal-fired, gas-fired or nuclear power plants - require external power to start their key equipment.
Black Start is called the "cardiopulmonary resuscitation" of the power system because it must be as precise and orderly as a doctor rescuing a patient:
1. Start the "spark" power plant: First, rely on a few special power plants with self-starting capabilities (usually small hydropower plants or gas power plants equipped with diesel generators) to generate initial electricity;
2. Establish "power islands": Use these initial powers to start more power plants to form multiple small independently operated power grid areas, each of which must accurately maintain a standard frequency of 50 Hz;
3. Synchronous grid connection: Like a puzzle, gradually connect these "power islands" to ensure that the frequency and voltage are fully matched before they can be connected to the grid;
4. Load control: Carefully control the speed of power demand access to prevent the fragile power grid that has just been restored from collapsing again due to a surge in load.
Major Technical Difficulties of Black Start
1. Power dependency dilemma
Most power plants cannot start by themselves and require external power support. For example, coal-fired power plants need electricity to crush and transport fuel, and nuclear power plants rely on electric pumps and valve systems. Only about 10% of hydropower plants and a few gas-fired power plants equipped with diesel generators have self-starting capabilities. This "chicken or egg" dilemma is the primary difficulty faced by black starts.
2. Precision of system synchronization
During the recovery process, each "power island" must strictly maintain a standard frequency of 50Hz (European standard). A frequency deviation of more than ±0.5Hz may cause grid connection failure or even damage equipment. During the black start process after the Quebec blackout in Canada in 1982, a major accident caused damage to lightning arresters and transformers due to voltage exceeding 1.05 times the limit value.
3. Paralysis of information and control systems
When the power grid is completely shut down, a large number of alarm messages will suddenly flow into the dispatch center, and the communication system is often limited in function due to limited backup power. The DC power supply of many telemetry and remote control equipment can only last for a few hours. A long power outage will lead to the transmission of erroneous information, making it difficult for dispatchers to make correct judgments.
New Challenges Brought by High Proportion of Renewable Energy
Spain is facing the world's first black
start challenge under the conditions of high proportion of renewable energy.
Renewable energy accounts for 56% of its power structure (wind power 23%,
photovoltaic power 17%, hydropower 13%), nuclear power accounts for 19%, and
natural gas is supplemented. This new power structure has brought unique
advantages and created unprecedented difficulties:
1. The "double-edged sword" effect of wind and solar power generation: renewable energy will automatically disconnect from the grid when the power grid fails (safety mechanism), exacerbating the scale of power outages; and when it is restored, it is difficult to provide stable support due to its intermittent nature.
2. Insufficient system inertia: The rotating units of traditional thermal power and nuclear power provide the "inertia" of stable grid frequency, while wind and solar power generation lack this characteristic, making frequency control more difficult.
3. Shortcomings in energy storage capacity: Spain's energy storage capacity accounts for only 0.3% of electricity demand and cannot buffer severe fluctuations.
When the Iberian Peninsula fell into darkness, Spanish power grid operator Red Eléctrica immediately launched the most complex black start operation in history. This precise power restoration process lasted 15 hours, and it was not until 3:30 a.m. the next day that Spain announced that 99.95% of the power supply had been restored. This actual operation provided valuable first-hand experience for the global energy industry.
Phased Recovery Strategy
1. Hydropower plays a pioneering role
The 10% share of hydropower in Spain and 25% in Portugal has become a lifeline - hydropower stations can be started with almost no external power supply, and can be called "natural allies of black start". The two large pumped storage power stations La Muela and Aldeadávila completed synchronization within three minutes, and the power jumped from zero to 3GW.
2. Natural gas takes the burden
All seven nuclear power units in Spain were automatically shut down due to protection mechanisms, and affected by the "xenon-135 poisoning" effect, it takes 24-48 hours to restart. In the case of unstable wind and solar power generation, natural gas combined cycle power plants have become the mainstay of power grid recovery.
3. Island synchronization strategy
Operators divide the country into multiple regions (such as Aragon-Catalonia, Galicia-León, etc.), and gradually restore and synchronize them like a puzzle. Each region must first establish a stable 50Hz frequency "island" before carefully connecting to other regions.
It is worth noting that the power outage in Spain lasted only four to five seconds in San Vicente del Monte, the only village in Spain that did not lose power, which belongs to the town of Valdáliga. In 2020, Viesgo deployed an innovative energy storage project in the village. For the average daytime electricity consumption of 50 kWh in the town of Mount Saint Vincent, the project can guarantee electricity supply to the area for about 5 hours.
When the proportion of renewable energy is too high (lacking the grid stability inertia of traditional energy), the resilience of the existing European grid is already insufficient. It is necessary to increase investment in grid-level inverters, battery energy storage, synchronous renewable energy (biomass/pumped storage) and interconnection lines. Although these are already in the planning, they failed to prevent the blackout and black start crisis in time.
