1. Introduction
Against the backdrop of a global focus on developing a low-carbon economy and China's proposed "dual-carbon" target, wind energy, as a clean and sustainable renewable energy source, has become a focal point for governments and energy giants worldwide. With the continuous construction of onshore wind farms, increasingly mature technology, and declining costs, onshore wind power has developed rapidly, with global newly installed onshore wind power capacity reaching 61.8 GW in 2019 alone. However, limited by onshore exploitable land and wind energy resources, offshore wind power has gradually become a development trend. In particular, China's southeastern coastal areas are economically developed, have a well-established power grid, and abundant offshore wind energy resources, making them highly suitable for large-scale development and grid connection of offshore wind power.
2. Current Status of the Offshore Wind Power Industry
In 2020, the global newly connected offshore wind power capacity exceeded 6 GW, roughly the same as in 2019. Ten years earlier, in 2010, the global newly installed offshore wind power capacity was less than 1 GW. Meanwhile, the proportion of offshore wind power in the global newly installed wind power capacity has also risen from 2.5% in 2010 to the current 7%.
2.1 Current Status and Trends of the Overseas Offshore Wind Power Industry
In terms of the ranking of countries by newly installed capacity, the top five offshore wind power markets globally in 2020 were China, the Netherlands, Belgium, the UK, and Germany. Industry experts predict that the global offshore wind power market will experience an average annual growth rate of over 30% between 2020 and 2025. This assessment is based on the following reasons:
01
The rapid decline in offshore wind power costs is due to the increasing size of offshore wind turbines (see Figure 2-1), which can significantly save on upfront investment and subsequent operation and maintenance costs.
Figure 2-1 Global Development Trends of Offshore Wind Turbines
Data source: GWEC Market Data Platform, August 2020
02
With governments around the world raising their targets for offshore wind power development, the Asian markets of China, Vietnam, Japan, and South Korea are expected to see rapid growth. In the European market, in addition to Western European countries continuing to vigorously develop offshore wind power, Eastern European countries will also begin construction of offshore wind power facilities. Furthermore, the first large-scale offshore wind farm in the United States will be connected to the grid in 2023.
03
The industrialization of floating wind power (see Figure 2-2) will have a wider range of applications because the floating foundation structure is suitable for deep sea areas with a water depth of 50 to 200 meters. According to the World Energy Report, the global installed capacity of floating wind power will reach 8 to 10 GW by 2030.
Figure 2-2 Schematic diagram of a floating offshore wind farm
2.2 Current Status of China's Offshore Wind Power Industry
China's offshore wind power industry started relatively late, but its development in recent years has been extremely rapid. Since 2018, China's newly installed offshore wind power capacity has consistently led other countries. In particular, in 2020, China's newly connected grid capacity exceeded 3GW for the first time. Based on cumulative installed capacity, China surpassed Germany to become the world's second-largest offshore wind power market by the end of 2020. According to estimates based on the growth rates of offshore wind power in various countries, China replaced the UK as the world's largest offshore wind power market in 2021.
2.2.1 The scale of installed capacity and grid connection continues to grow.
The Shanghai Donghai Bridge Offshore Wind Power Project, China's first large-scale offshore wind power project, which started in 2006 and began construction in 2008, successfully installed 34 domestically produced 3MW offshore wind turbine units, with a total installed capacity of 102MW, thus opening the prelude to the development of offshore wind power in China.
In 2016, the National Energy Administration released the 13th Five-Year Plan for Wind Power Development and introduced a series of major favorable policies to encourage the development of offshore wind power, which also means that the development of offshore wind power in China has moved from "project demonstration" to the fast track of "rapid development".
In 2020, offshore wind power projects entered a critical period of rush installation. According to statistics, 30 projects were under construction at the same time in the first half of the year, with an installed capacity of 12,972,800 kilowatts, including 11 newly started projects and 3 projects that were fully connected to the grid.
2.2.2 The single unit capacity of wind turbines has been increasing year by year.
According to data from the end of 2019, in terms of single unit capacity, 4MW units have the largest cumulative installed capacity, while 5MW has become the mainstream model for offshore wind power projects (see Figure 2-3).
On July 12, 2020, China's first 10MW wind turbine was successfully connected to the grid and generated electricity at the Xinghua Bay offshore wind farm in Fujian Province, setting a new record for the capacity of a single offshore wind turbine in China. From the perspective of wind turbine manufacturers' development plans, 8MW has become a new starting point, and large-scale offshore wind turbines of 10MW and above have been listed as key development models.
Figure 2-3 Percentage of Offshore Wind Turbine Capacity in China at the End of 2019
2.2.3 Offshore wind power construction is gradually shifting from nearshore shallow waters to deep-sea and deep-water areas.
By the end of 2019, the total approved offshore wind power capacity in China reached 35 million kilowatts. Among them, Jiangsu and Guangdong had approved capacities exceeding 10 million kilowatts, while Fujian and Zhejiang had approved capacities exceeding 3 million kilowatts. The available near-shore resources for future development are limited, while China has a vast area of exploitable deep-sea waters, which are expected to become the focus of offshore wind power development in the future.
3. Hardware requirements for industrial Ethernet switches in offshore wind farms
Offshore wind turbines and offshore substations are built tens of kilometers away from land, in extremely harsh environments. This places very high demands on equipment, especially core communication equipment, primarily concerning reliability, resistance to salt spray, high and low temperatures, and electromagnetic interference. Furthermore, offshore equipment maintenance is constrained by weather, maritime regulations, and vessel deployment, making both emergency and routine maintenance exceptionally difficult, with highly unpredictable timing. This places extremely high demands on the stable and reliable operation of Ethernet switches.
3.1 Reliability requirements
Several key indicators of equipment reliability:
1) Mean Time To Failure (MTTF)
2) Mean Time Between Failures (MTBF)
3) Mean Time To Repair (MTTR)
3.1.1 MTBF indicator
One of the most important performance indicators for industrial Ethernet switches is Mean Time Between Failures (MTBF). The most widely accepted and authoritative standards are MIL-HDBK-217, GJB/Z299B, and Bellcore. Most foreign brands of industrial switches use the American MIL-HDBK 217F as a reference standard and employ HALT (High-Accelerated Life Test) and HASS (High-Accelerated Stress Screening) tests during R&D and production testing to verify whether the product's MTBF meets design requirements. The MTBF of most industrial Ethernet switches is over 20 years, and some even exceed 50 years.
HALT (Highly Accelerated Life Testing) is mainly used in the product research and development design stage. It is effective in exposing potential defects in products and is an important testing method for design engineers to improve product reliability.
HASS (Highly Accelerated Stress Screening) is a high-accelerated stress screening process performed on the production line after products have passed the HALT test to determine their operational or destructive limits. 100% of products are required to participate in the screening. Its purpose is to ensure that the manufactured products are free of any hidden defects, or at least to identify and resolve these defects before the products leave the factory. HASS uses accelerated stress to find defective products in a short time, shorten the corrective action cycle, and identify products with the same problems.
3.1.2 MTTR indicator
The typical requirements for offshore wind farm sites are: Mean Time To Repair (MTTR) provided by the manufacturer, which is generally 0.5 to 1 hour when management support time and delivery time are not taken into account; and the time for diagnosing (or inspecting) and updating faulty plugs should be less than 30 minutes.
If an industrial switch experiences a hardware failure, and if management support time and delivery time are not considered, and only a simple replacement is needed, in most cases, the industrial switch product can be replaced within 1 hour, meeting the customer's MTTR requirements.
3.2 Corrosion resistance requirements
A key characteristic of the marine operating environment is the high salt spray level. Industrial Ethernet switch products must provide circuit board protective coating design to achieve G3 protection level and fully comply with the requirements of ISA-S71.04-1985 (classification G3- Hash Group A) and EN60068-2-60 Method 4 standards in order to operate stably and reliably for a long time in the harsh marine environment.
Early offshore wind farms experienced a large number of switch failures. Upon opening the switch casings, visible burn marks were found on the circuit boards. One reason for this was that these switches lacked a protective coating.
3.3 High and low temperature requirements
Because different offshore wind farms are located at different latitudes, their climate conditions vary greatly. For example, in winter, the lowest temperature at the Zhuanghe offshore wind farm in Dalian can reach -15 degrees Celsius, while in summer, the highest temperature at the Xuwen offshore wind farm in Zhanjiang can reach 38 degrees Celsius. The temperature inside the wind turbine towers may be even higher than the outdoor temperature. Therefore, very high requirements are placed on the normal operating temperature of industrial switches.
Although most industrial switch manufacturers on the market list operating temperatures of their switches as -40°C to +70°C, or even -40°C to +85°C, these figures are derived from short-term laboratory tests. For example, the testing requirements of a reputable domestic testing institution specify that in high-temperature environments, the switch, while powered on, should be placed in the center of an environmental test chamber, and the temperature should be raised to 70°C and maintained for 2 hours. The device should function normally at +70°C, and the store-and-forward rate should reach 100%. If this requirement is met, the switch is considered合格 (qualified/acceptable).
The technical requirements for the same low-temperature environment are as follows: The switch, while powered on, is placed in the center of an environmental test chamber, and the temperature is lowered to -40°C and then maintained at that temperature for 2 hours. The device should function normally at -40°C, with a store-and-forward rate of 100%; it should also be able to start normally at -40°C. If these requirements are met, it is considered合格 (qualified/acceptable). Therefore, the test only verifies whether it can operate stably for 2 hours under this extreme temperature.
While industrial switches in offshore wind farms do not need to withstand such extreme temperatures, they must operate continuously for extended periods in harsh temperature environments, and may even be subject to additional adverse effects from other external environments. Only industrial switches that have stood the test of time can be said to meet the high and low temperature requirements of offshore wind farms.
(To be continued)