In 2022, the proportion of nuclear power installed capacity has been reduced to 1. The installed capacity of flexible regulated power sources such as gas, pumped storage, hydropower, fuel and energy storage in Germany has reached 0. In addition, the output adjustable space of coal-fired power units is superimposed, and the flexible regulation capacity of power supply side is close to the maximum load, which can effectively cope with the output fluctuation of high proportion of wind and solar new energy.
In 2020, the German Bundestag passed the German Coal-fired Power Plant Elimination Act, formulated a specific exit plan for coal-fired power plants, sorted out the shutdown units and timelines, and provided compensation of up to 40 billion euros to cope with the impact of energy transformation. From January 1, 2021, Germany began to invite tenders for the coal phase-out plan, and compensated the coal-fired power plants planned to be shut down according to the tender amount, with a weighted average subsidy of 66259 Euro/MW, which is the compensation for coal phase-out, including the economic losses of standby and decommissioning. After the conflict between Russia and Ukraine, Germany has restarted or postponed the decommissioning of coal-fired power capacity to 10 GW. In order to avoid the possible power shortage after the shutdown of nuclear power, the German government announced that more coal-fired power plants would be on standby for nearly two years, and introduced the Alternative Power Plant Availability Act to ensure that the coal-fired power plants originally closed would remain in operation and that retired coal-fired units could re-participate in the electricity market at a specific time.
1. Germany is the core hub of the European interconnected power grid, interconnected with neighboring countries through 65 AC and DC lines (another German-British submarine power cable is under construction). The capacity of transnational interconnected transmission lines in Germany is about 30 million kW, accounting for about 40% of the maximum power load, which provides a sufficient network foundation for transnational power mutual aid. When the local power generation capacity is insufficient, the neighboring country will import power to support the power supply; when the local new energy is developed and the power supply is sufficient, the power will be transmitted to the neighboring country to reduce the peak shaving pressure. Since 2003, Germany has exported net electricity to neighboring countries, as shown in Figure 3.
Fig. 3
Changes of German net export electricity from 1992 to 2022 2022
1. Germany has futures, spot and other electricity markets, and the trading products cover multiple time scales such as medium and long term, day-ahead, intra-day and real-time; the on-grid price is determined by the market supply and demand, and new energy and conventional power sources compete on the same platform; the electricity sales market is fully competitive, and electricity consumers can freely choose electricity suppliers. Innovative market mechanism encourages multi-subject participation, such as biomass power generation, hydropower and roof photovoltaic, which can provide frequency modulation services through virtual power plant operators, with demand-side adjustable capacity accounting for more than 13% of the maximum load and controllable load accounting for 1.1% of the
maximum load. For a long time, Germany has implemented a "bottom-up" and "self-balancing" operation mode. There are more than 430 balancing groups in the country. The balancing groups must meet the balance of power supply and demand every 15 minutes. When the internal balance cannot be achieved, they must bear the balance cost of the system. The mechanism of balance group not only effectively encourages the improvement of new energy forecasting technology and reduces the system balance error caused by the fluctuation of new energy output, but also encourages the balance group to fully tap the flexibility potential, realize the best scheduling of resources in the group and improve the flexibility level of the system.
1. Germany has long adopted a variety of forecasting models based on weather factors. Factors such as snow, cold front, hurricane, cloud air convection, wind and light abandonment, operation status of renewable energy stations and network maintenance plan are also included in the prediction model. Through the Renewable Energy Law, Germany has continuously strengthened the monitoring and control of renewable energy, requiring that renewable energy power generation equipment above 100 kW must have the technical conditions of telemetry and remote regulation. In April
2023, the maximum load level of Germany was about 68 million kW. Before the shutdown of nuclear power, continuous and stable power was provided in the form of base load, and the output level was about 2.7 million kW, accounting for only 4% of the maximum load. Under non-extreme scenarios, the impact of nuclear power shutdown on German power supply security is very limited.
2. New energy participates in electricity market bidding according to zero electricity price (actual settlement price also includes government subsidies) to ensure priority access to the grid. When the output of new energy is high, the clearing price of electricity market decreases, or even negative price appears. Affected by the electricity price, the output of thermal power, fuel and gas power generation should be reduced as much as possible.
Taking 14:00 on April 10 as an example, the load level of Germany is only 44.64 million kW, the output of renewable energy is 53.65 million kW, the output of nuclear power is 2.66 million kW, and the output pressure of non-renewable energy is reduced to 9.08 million kW. The day-ahead market clearing price in Germany is – 7.77 euro/ (MW · H) (about –
0.2). Before and after the nuclear power shutdown on April 17, the output and imported electricity of various power sources in Germany are shown in Figure 4. At 06:00 on April 17, 2023, the electricity load in Germany was at a low level (about 53.07 million kW), but the output of renewable energy was only 12.38 million kW (the maximum output on that day was close to 40 million kW), and the output of non-renewable energy was about 25.08 million kW. The day-ahead market clearing price in Germany is 140.82 Euro/ (MW · H) (approx. 1.
Fig. 4 Changes
in output and imported power of various power sources before and after the shutdown of nuclear power in Germany Fig
. 3. The proportion of renewable energy generation in Germany increased from 17% to 46%, the proportion of coal power decreased from 42% to 33%, and the proportion of nuclear power decreased from 22% to 6%. German residential and industrial electricity prices have risen by 38% and 89% respectively. In 2022, it will reach 2.5 yuan/ (kW · H), 1.
Fig. 520
Changes of residential and industrial electricity prices in Germany in 10-2022 Germany from 2010 to 20223
. The price of electricity in Germany consists of the cost of power supply, grid charges and taxes, which include value-added tax, franchise fees, renewable energy surcharges, electricity taxes and other taxes. Taking the average electricity price of households and small businesses in 2021 as an example, the grid cost accounts for about 24%, and the highest proportion of taxes and fees is the renewable energy surcharge, which accounts for about 40% of taxes and fees, and about 20% of the total electricity price.
Germany implements the separation of transmission and distribution, the transmission and distribution network is operated by four transmission network companies (TSO) and more than 800 distribution network operators (DSO), the transmission cost must be authorized and approved by the German Federal Network Regulatory Authority, and the cost of peak-shaving power purchased from the peak-shaving power market when supply and demand are unbalanced is also included in the cost of grid use. The other part is charged to the power supplier who causes the imbalance of the power grid. There is a big difference in the cost of distribution. The pricing mechanism of power grid cost is a way of hierarchical accumulation from high-voltage level to low-voltage level. There are many competitive units in Germany's transmission and distribution network, and the expected total profit of each link is high. With the deduction of time, the cost of the network is gradually increasing.
Taxes and fees are incorporated into the electricity price system after being approved by the competent government departments at all levels. Renewable energy surcharge is mainly used to pay subsidies and other expenditures to renewable energy power plant operators, which will be adjusted annually according to the actual subsidies of the project, and taxes and fees will be raised in 2014 and 2020.
Figure 6 shows the cost structure of household electricity price with annual electricity consumption of 3500 kW · H in Germany from 2010 to 2022. From 2010 to 2021, the average electricity price in Germany increased by 36%, of which the supply cost decreased by about 3%, the renewable energy surcharge and grid cost increased by 217% and 33% respectively, and the contribution of the increase of renewable energy surcharge and grid cost to the increase of electricity price was 53% and 23% respectively.
Fig. 6 Cost structure
of residential electricity price with annual consumption of 3500 kW · H in Germany from 2010 to 2022 Fig. In 2022, the conflict between Russia and Ukraine triggered a crisis of energy supply in Europe, which greatly pushed up the cost of fossil energy power generation. Recently, the electricity price in the wholesale electricity market in Germany fluctuated and rose to new highs. The residential electricity price and industrial electricity price of the terminal increased by 3% and 23% respectively compared with 2021. Since the beginning of 2023, due to the warm winter climate, weak economy and high natural gas stocks, the situation of energy supply and demand in Europe has eased significantly, and the price of coal, oil and gas has dropped sharply. After the complete shutdown of nuclear power on April 15, the German day-ahead market price did not fluctuate significantly, as shown in Figure 7. By the end of June, the average day-ahead electricity price in Germany was about 107 euros/ (MW · H), down 45% from the same period last year. As an important baseload power source, Germany's ability to cope with the risk of future energy supply shortage will be further weakened after the shutdown of nuclear power, and the terminal electricity price will still face upward pressure.
China's thermal power may be blocked due to heating and steam supply, poor coal quality, equipment maintenance and other reasons, and hydropower may be blocked due to low water head and other reasons. If the extreme situation of new energy such as "extremely hot without wind, extremely cold without light" is superimposed, there will be a gap in power balance. Affect the reliable supply of electricity.
Germany has sufficient source and load regulation resources, strong system regulation capability, flexible regulation of power supply accounts for 24% of the total installed capacity, demand-side adjustable capacity accounts for more than 13% of the maximum load, and controllable load accounts for 1. The proportion of new energy installed capacity in China has increased from 11.3% to 24. The proportion of adjustable and controllable resources on the demand side in the maximum load is low, and the system regulation capacity is limited.
Germany has a reasonable grid structure, uniform power flow distribution and less grid congestion, which lays a foundation for the smooth operation of Germany's decentralized market model. China's Shanxi, northern Hebei, Heilongjiang, Qinghai and other provinces are facing the problem of uncoordinated development of network sources, and there are still blocked channels within the network in some areas, which restricts the transmission and consumption of clean energy. Backed by the European power grid,
Germany is interconnected with 12 European countries through 65 AC and DC lines, complementing the neighboring countries in power supply structure, and can rely on transnational mutual support to cope with the random fluctuation of new energy output. The transmission capacity of inter-provincial tie lines in China is still insufficient, and the power generation and consumption of adjacent provinces in the sending and receiving areas are strong at the same time. There is still much room for improvement in inter-provincial mutual assistance and complementary surplus and deficiency in key periods such as winter and summer.
China and Germany have roughly the same monitoring and control technologies for main power sources and centralized new energy sources, and the main difference lies in distributed power sources. Germany has realized the considerable controllability of distributed photovoltaic and established a relatively perfect hierarchical regulation mode, while China is in the pilot stage of considerable controllability of distributed photovoltaic, and the hierarchical regulation mode needs to be further explored.
Germany allows controllable loads to participate in the balancing market, and controllable loads can directly participate in the real-time balancing regulation of the system, which greatly increases the regulation resources of the power grid. Spot market price signals are used to guide units and loads to actively participate in power grid regulation, effectively promoting new energy consumption. Demand side management in China is mainly carried out by means of demand response and orderly power consumption, but the direct control of controllable load by dispatching agencies has not yet been realized, and demand side resources are less involved in real-time dispatching. The demand for power grid regulation is met by means of peak shaving ancillary service market, and some spot pilot areas meet the demand for power grid regulation through spot market.
To sum up, Germany has a solid source, network and load foundation, which provides a strong material foundation for the rapid transformation of the power system. In recent years, China's new energy development has achieved remarkable results, and the utilization rate of new energy consumption is also at a high level. However, with the accelerated construction of the new power system and the further increase of the proportion of new energy generation, the pressure of ensuring supply, promoting consumption and stabilizing electricity prices will become more prominent. With reference to the German experience, the following recommendations are made.
1) Give full play to the role of conventional power supply, interconnected power grid and flexible system regulation. Give full play to the role of conventional power supply as a ballast stone; further strengthen the construction of inter-provincial and inter-regional interconnected power grid; accelerate the development of pumped storage, new energy storage, demand-side resources and thermal power flexibility transformation, and effectively enhance the flexibility of the system; use retired coal-fired power units to establish a strategic reserve unit mechanism, and play a strategic reserve role in extreme cases.
2) Accelerate the improvement of monitoring and control means suitable for high proportion of new energy grid connection. The meteorological forecast model is introduced to predict the power generation capacity and the balance of power and energy, and a normal monitoring mechanism is established; the dispatching control scope of distributed photovoltaic and new energy storage is expanded, and the hierarchical dispatching system and management mode suitable for the high proportion of new energy grid connection are accelerated.
3) Establish the coal power capacity compensation mechanism and electricity price formation and dredging mechanism adapted to the new power system. Due to the large-scale grid connection of new energy, the utilization rate of coal-fired power equipment and the efficiency of power generation are further reduced, resulting in an upward trend in the cost of thermal power generation. The simple electricity price mechanism can not reflect the security function of coal-fired power under low operating rate, so it is urgent to establish ancillary service market such as peak shaving compensation and capacity price mechanism. In recent years, the cost of wind power and photovoltaic power generation in China has dropped significantly, and new projects in most provinces have achieved parity access to the grid, but parity access to the grid does not mean parity utilization.The power system will undergo major changes in the power supply structure, power grid form and other aspects, which will inevitably involve a series of new costs such as supporting the construction, transmission and consumption of new energy. The new costs need to be borne scientifically and fairly among various market players. At the same time, the affordability of end users should be fully considered, and the price formation and dredging mechanism adapted to the new power system should be gradually established.
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