Chapter 4. Technical Characteristics of Renewable Energy by Source
4.1 Status of RE Technology by Source
4.1.2 Wind power
high efficiency and potential for low-cost production. However, challenges remain, such as that competitiveness must be ensured, particularly in the mass-production system to achieve breakthrough growth. Several companies have started to release various semi-mass-produced solar cells (dye-sensitized and organic solar cells) ahead of their commercialization. Generally, it is expected that the commercialization hurdles, such as low efficiency and stability, which have offset the benefits in terms of manufacturing cost and applicability, will be overcome to some extent. At the beginning of 2016, since the discovery of the organic-inorganic perovskite compound from doing research to solidify dyes for dye- sensitized solar-cells, a research institute in South Korea recorded the world-class level efficiency of 22.1%.
This raises the expectations about future high-efficiency and high-stability thin-film solar-cell technology.
Furthermore, the research on quantum dot solar cells is at the early stages. In pursuit of high photovoltaic conversion efficiency through the arrangement of different size particles, researchers attempt to take advantage of the phenomenon that smaller semiconductor particles can absorb light with shorter wavelengths and larger particles can absorb light with longer wavelengths.
Wind spins the blades of the turbines, which spins the main shaft, gearbox, and generator consecutively to generate electricity. In contrast to its simple operation principle, the key components of wind turbines require considerable high-technology input in terms of their design and manufacturing, and the system control. Since the first wind turbine was invented by Charles Brush, it has taken approximately 130 years to develop a modern, MW-class wind turbine. The blades of wind turbines function on the same principle as airplane wings, i.e., the lift force, which is generated by the wind passing over the blade surface, activates the blades. Most MW-class wind-turbine blades have a rotational speed of 15~25 rpm. Longer blades are used to improve efficiency in areas with lower average wind speeds. In accordance with the International Electrotechnical Commission (IEC) criteria, the blade length of Class I blades is typically approximately 50 m, even for a large-capacity (3 MW) wind turbine. The length of Class II blades, designed for lower wind speeds, is approximately 60 m.
As the generator cannot produce electricity at a low rotational speed, a gearbox is employed often in wind turbines to increase the rotational speed. The gearbox accelerates the rotational speed of the blades to drive the generator. Wind turbines are classified into two types, namely, gearbox driven and direct drive.
The desired rotational speed of wind turbines without a gearbox can be achieved by increasing the number of poles in the permanent magnet mounted on the generator.
[Figure 4-5] Trend toward larger-capacity wind turbines
Source: KEA (2016a), Renewable Energy White Paper
As shown in [Fig. 4-5], after the commercialization of 1~2 MW wind turbines in the early 2000s, it took five years for 5 MW wind turbines to be commercialized. In 2015, the Vestas V164 8 MW was the world’s largest wind turbine.
4.1.2.2 Global Trends in Technology Development
In Europe and the US, efforts are underway to advance various technologies intended to reduce the levelized cost of energy (LCOE). LCOE, a concept that includes depreciation and financing cost, such as project financing, is the total cost input from the initial stage in the planning of a wind farm to the demolition after the termination of its life cycle divided by the total energy output over the entire life cycle.
Turbine costs account for the largest percentage of the LCOE composition, followed by the balance of system (grid connection cost). Therefore, wind turbine manufacturers focus more on cost reduction, whereas wind farm developers and operators are committed usually to minimizing the grid connection costs.
[Figure 4-6] Composition of LCOE of onshore wind power
Source: KEA (2016a), Renewable Energy White Paper
[Figure 4-7] Composition of LCOE of offshore wind power
Onshore and offshore wind power have different LCOE compositions because offshore wind power requires additional equipment, such as substructures and submarine power cables, owing to the challenges associated with such installation. In addition, extra insurance premiums and reserve funds are required for offshore installations.
The European Union is pursuing technology development to reduce the current LCOE rate of 11~18 cent (EUR)/kWh to 9 cents (EUR)/kWh by 2020 for offshore wind power. Siemens, who has the largest market share in offshore wind power, aims to reduce the LCOE rate to a maximum of 5 cent (EUR)/kWh, much lower than the EU target. DONG Energy, one of the major developers of wind farms, remains committed to reducing LCOE by 20~30% by 2017.
The Nuclear Energy Agency (NEA) of the Organization for Economic Cooperation and Development (OECD) has recently analyzed the LCOE of 181 power plants in 22 member states that are scheduled to start their commercial service in 2020. The results showed that nuclear power generation is the lowest at 47.4 USD/MWh, followed by onshore wind (74.7 USD/MWh), coal-fired (76.3 USD/MWh), natural gas (98.3 USD/MWh), and solar PV (121.6 USD/MWh). This implies that grid parity, at which the unit cost of onshore wind-power generation becomes cheaper than coal-fired power generation, could be reached by 2020. Distribution difficulties and a relatively high unit cost compared with fossil fuels have previously impeded wind power generation; however, the unit cost has been dropping because of continuing technological advancements.