Q1 What's offshore wind power?
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.
Q2 What makes up an offshore wind farm and how is it installed?
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.
Q3 What are Installed Capacity, Capacity Factor, and Electrical Energy Output?
Maximum electricity a power plant can generate, normally measured in MW or GW.
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.
Q4 What is grid connection?
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.
Q5 What’s the difference between offshore wind farm and onshore wind farm located along the west coastline of Taiwan? Is Taiwan an ideal place to develop offshore wind farm?
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.
Q6 What’s the benefit of developing offshore wind farms in Taiwan?
It can be analyzed from two aspects: environmentally and economically.
Environmentally speaking, offshore wind power can greatly help reduce the carbon emissions. According to IEA report, the carbon emission per capita in Taiwan was 11.26 tons in 2004, which figure ranked Taiwan number eighteenth in the world and number one in Asia in terms of carbon emissions. Since climate change becomes a global issue, Taiwan echoed to the international pressure by setting the carbon emission target to return to 2005 level by 2020 which is equivalent to 210 million tons and to 2000 level by 2025.
The carbon emission reduction of one kilowatt-hour from offshore wind power is around 2,000 tons. Assuming that 6,000 MW offshore wind farms are developed in Taiwan, the total carbon emission reductions can reach 12 million tons annually. Offshore wind has the highest potential among all renewable energies to reach Taiwan government’s carbon emission reduction goal.
Economically speaking, offshore wind can encourage the involvement of industry and financial institutions. In addition to offshore wind farm developer’s devotion and investment, the successful offshore wind farm development also needs the project financing provided by banks. Hence offshore wind development can activate financial market. Moreover, the offshore wind supply chain formed by the key component suppliers and offshore construction firms can increase the investment and create job opportunities, which upgrade Taiwan’s core competence.
Q7 In addition to Taiwan, where can we see the most prominent and advanced development of offshore wind farm? Do they share the same tariff mechanism as Taiwan does?
Europe is the pioneer in offshore wind farm development. European countries including Denmark, Netherlands, and Sweden took the lead to develop small-scale demonstrator project in the 1990s and then the UK took over the leading position after 2000 to plan 33 GW (33,000 MW) offshore wind farms. The UK and Taiwan share the same characteristic that both countries are surrounded by the sea. Therefore, the UK can fully utilize the vast ocean resources to develop offshore wind farms and is ranked top one in terms of installed capacity.
In addition, Germany is ambitiously planning the offshore wind installed capacity to reach 3,000 MW by 2015, and the US and China also start to acknowledge the benefits that offshore wind power can bring so they already plan several offshore wind farms along their east coast respectively.
The UK and Germany have the clearest tariff policy among all countries. The tariff in the UK is set by the market mechanism. Based on the incentives provided for offshore wind, the tariff is around NTD 9 (0.18 pound sterling) per kilowatt-hour in 2010. On the other hand, Germany adopts feed-in tariff system to guarantee 20-year power purchase. The feed-in tariff for offshore wind in the first 12 years is around NTD 6.3 (0.15 Euro) per kilowatt-hour and the developers don’t have to bear the grid connection and offshore substation costs. Taiwan is benchmarking to Germany’s feed-in tariff system but the first announced feed-in tariff for 2010 in Taiwan is only NTD 4.1982, which is far lower than any countries. The latest announced feed-in tariff for 2018 is about NTD 5.8498.
Q8 Will offshore wind farms interfere with shipping, fishing or ecology?
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.
Q9 When earthquake occurs or typhoon comes, what’s the impact on the turbine and how to mitigate?
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.
Q10 What are the international standards for offshore wind turbine?
IEC 61400-3:2009 sets the standards for wind turbine design and it can be categorized into Class I, II, III, and IV. Class A and Class B are further defined as a result of turbulence intensity across four classes. All wind speed data are at hub height and the hub height of offshore wind turbine is usually over 90 meters. Class IA is suitable for offshore wind farm where the average wind speed is 10 m/s, the extreme 50-year gust is 70 m/s and the turbulence intensity is 18%.
Q11 How does a team of technicians perform wind turbine maintenance and how to know when to maintain wind turbines?
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.
Q12 Can we choose to use offshore wind power in our daily life?
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.