Q&A

Offshore wind power is the electricity generated from offshore wind farms located at sea, in the fjord, and in the lakes. The Taiwan Strait is the best place for Taiwan to develop offshore wind power.

Offshore wind farm is composed of several hardware parts, including offshore wind turbine, foundation, transition piece, offshore substation, subsea cable, onshore cable and onshore substation. The electricity generated from offshore wind farms will be firstly collected and then stepped-up at offshore substation, transmitted through subsea cable and connected to the onshore cable all the way to Taiwan Power Company’s onshore substation.

Installed Capacity:
Maximum electricity a power plant can generate, normally measured in MW or GW.

Capacity Factor
The capacity factor is the ratio of an actual electrical energy output to the maximum possible electrical energy output over a given period, falling in the interval between 0 and 1. Capacity factors vary among different types of power generations. Take the annual statistics of 2016 made by Taiwan Power Company as an example, among the major electricity sources in Taiwan, the capacity factor of nuclear power, thermal power, and hydro power are 67.6%, 68.07%, and 35.71% respectively. The number of capacity factor of renewable energy is normally relatively less because of the natural limits. The capacity factor of the offshore wind power off Chunghua coast is about 25% to 30% as estimated.

Electrical Energy Output
Electrical Energy Output is the power generation in a given time period and is correlated to the capacity factor. In Taiwan, it is normal to use kWh as the basic unit of the electrical energy output.

In offshore wind farm, grid connection refers to electricity travelling from offshore substation, transmission via undersea and on-land cables, all the way to onshore substation. All onshore substations in Taiwan are operated by Taiwan Power Company which is responsible for power distribution and transmission for our daily use.

From 2001 when the first onshore wind farm was erected in Penghu County, Taiwan has had around 20 onshore wind farms with total installed capacity up to 400 MW in this decade. However, the average installed capacity of an onshore wind farm is only 20 MW which is mainly due to the limited land in Taiwan. As a result, the first-tier onshore wind farms are located sparsely with small-scaled wind farm plan, and already being either developed or underdeveloped.

On the other hand, Taiwan possesses extraordinary advantages in developing offshore wind farms. Taiwan is gifted with excellent wind offshore because of the Taiwan Strait’s special geography which causes channeling effect. Spacious sea area with strong wind enables the planning of large-scaled offshore wind farms with each installed capacity over a hundred MW, so more clean electricity can be offered for Taiwan use.

The franchise (or the Establishment Permit) issued by the Bureau of Energy, MOEA is required before the construction starts. In order to obtain the franchise, a list of documents shall be prepared, including the opinion letters to demonstrate that the offshore wind farm is not located in shipping, aviation and military restricted area. In addition, the developers will evaluate the impacts on the environment by conducting the environmental impact assessment and propose the mitigation methods or solutions correspondingly.

Since that the required seabed area for turbine installation is limited and the construction period is relatively flexible and short, as long as supporting measures are well-planned during the construction, the turbine in fact can become perfect habitat, spawning and feeding place after the offshore wind farm is in operation. Hence, the offshore wind farm has a very minimal impact on the environment.

The wind turbine only operates within the “cut-in” and “cut-out” wind speed. Generally speaking, when the wind speed is over 25 m/s, the software on the wind turbine would automatically pause the turbine or could automatically adjust the direction of the turbine and the pitch to avoid directly facing the gale. Another way is to stop the turbine before typhoon comes so the potential damage to turbine can be minimized. In addition, only turbines certified as IEC Class 1A which is the highest standard can fit Taiwan’s requirement, so the suitability of turbine is considered when selecting the wind turbine.

Different from the onshore wind turbine, the fixed-bottom offshore wind turbine majorly used in Taiwan needs foundation (supporting structure) undersea which stands on the seabed to support the wind turbine above sea level. As long as the sufficient earthquake records on the epicenter, magnitude and etc are gathered, the foundation strength can be augmented by tailor-made design and the structural interaction between wind turbine and foundation will be considered in the design to withstand the earthquake, too.

Periodic maintenance and unsceduled repairs are performed on wind turbines, and technician will access wind turbines via specially built vessels such as crew transfer vessel (CTV). Depending on different situations, the operation center will arrange certified technicians and spare parts required, together with appropriate transportation and special vessels, in order to carry out the maintenance works.

Every turbine is also installed with remote monitoring system (known as SCADA system). Therefore, operational and other data can be transmitted and viewed in the operation center in real time, which provides the info the operation center needs when a maintenace job is required.

The transmission and supply of power are currently under control of Taiwan Power Company. Therefore, residents in Taiwan cannot choose offshore wind power or other sources of energy for their daily consumption of electricity. However, according to Renewable Energy Development Act, Taiwan Power Company has a obligation to purchase renewable energy sources. Hence, once wind farms begin operation, a part of electricy in daily use will be supplied by offshore wind farms.