巨型深海渦輪機試驗為無盡的綠色動力提供了希望

Recently Yahoo News on-line reported the following

Giant Deep Ocean Turbine Trial Offers Hope of Endless Green Power

Erica Yokoyama

Mon, May 30, 2022, 6:07 PM

(Bloomberg) -- Power-hungry, fossil-fuel dependent Japan has successfully tested a system that could provide a constant, steady form of renewable energy, regardless of the wind or the sun.

For more than a decade, Japanese heavy machinery maker IHI Corp. has been developing a subsea turbine that harnesses the energy in deep ocean currents and converts it into a steady and reliable source of electricity. The giant machine resembles an airplane, with two counter-rotating turbine fans in place of jets, and a central ‘fuselage’ housing a buoyancy adjustment system. Called Kairyu, the 330-ton prototype is designed to be anchored to the sea floor at a depth of 30-50 meters (100-160 feet).

In commercial production, the plan is to site the turbines in the Kuroshio Current, one of the world’s strongest, which runs along Japan’s eastern coast, and transmit the power via seabed cables.

“Ocean currents have an advantage in terms of their accessibility in Japan,” said Ken Takagi, a professor of ocean technology policy at the University of Tokyo Graduate School of Frontier Sciences. “Wind power is more geographically suited to Europe, which is exposed to predominant westerly winds and is located at higher latitudes.” Japan’s New Energy and Industrial Technology Development Organization (NEDO) estimates the Kuroshio Current could potentially generate as much as 200 gigawatts — about 60% of Japan’s present generating capacity.

Like other nations, the lion’s share of investment in renewables has gone into wind and solar, especially after the Fukushima nuclear disaster curbed that nation’s appetite for atomic energy. Japan is already the world’s third largest generator of solar power and is investing heavily in offshore wind, but harnessing ocean currents could provide the reliable baseline power needed to reduce the need for energy storage or fossil fuels.

The advantage of ocean currents is their stability. They flow with little fluctuation in speed and direction, giving them a capacity factor — a measure of how often the system is generating — of 50-70%, compared with around 29% for onshore wind and 15% for solar.

In February, IHI completed a 3 ½ year-long demonstration study of the technology with NEDO. Its team tested the system in the waters around the Tokara Islands in southwestern Japan by hanging Kairyu from a vessel and sending power back to the ship. It first drove the ship to artificially generate a current, and then suspended the turbines in the Kuroshio.

The tests proved the prototype could generate the expected 100 kilowatts of stable power and the company now plans to scale up to a full 2 megawatt system that could be in commercial operation in the 2030s or later.

Like other advanced maritime nations, Japan is exploring various ways of harnessing energy from the sea, including tidal and wave power and ocean thermal energy conversion (OTEC), which exploits the difference in temperature between the surface and the deep ocean. Mitsui OSK Lines Ltd. has invested in UK-based Bombora Wave Power to explore the potential for the technology in Japan and Europe. The company is also promoting OTEC and began operating a 100 kW demonstration facility in Okinawa in April, according to Yasuo Suzuki, general manager of the corporate marketing division. Kyushu Electric’s renewable unit Kyuden Mirai Energy begins a 650 million yen ($5.1 million) feasibility test this year to produce 1 MW of tidal power around the Goto Islands in the East China Sea. The government this month also proposed changes to offshore wind auctions that could speed up development.

Among marine-energy technologies, the one advancing fastest towards cost-effectiveness is tidal stream, where “the technology has advanced quite a long way and it definitely works,” said Angus McCrone, a former BloombergNEF chief editor and marine energy analyst. Scotland-based Orbital Marine Power is one of several companies constructing tidal systems around Orkney, location of the European Marine Energy Centre. Others include SIMEC Atlantis Energy’s MeyGen array and California-based Aquantis, founded by US wind pioneer James Dehlsen, which reportedly plans to start testing a tidal system there next year.

While tidal flows don’t run 24 hours, they tend to be stronger than deep ocean currents. The Kuroshio current flows at 1 to 1.5 meters per second, compared with 3 meters per second for some tidal systems. “The biggest issue for ocean current turbines is whether they could produce a device that would generate power economically out of currents that are not particularly strong,” said McCrone.

Ocean Energy Systems, an intergovernmental collaboration established by the International Energy Agency, sees the potential to deploy more than 300 gigawatts of ocean energy globally by 2050.

But the potential for ocean energy is location dependent, taking into account the strength of currents, access to grids or markets, maintenance costs, shipping, marine life and other factors. In Japan, wave energy is moderate and unstable through the year, while areas with strong tidal currents tend to have heavy shipping traffic, Takagi said. And OTEC is better suited to tropical regions where the temperature gradient is bigger. One of the advantages of the deep ocean current is it doesn’t restrict navigation of ships, IHI said.

Still, the Japanese company has a long way to go. Compared with onshore facilities, it’s much more complicated to install a system underwater. “Unlike Europe, which has a long history of the North Sea Oil exploration, Japan has had little experience with offshore construction,” said Takagi. There are major engineering challenges to build a system robust enough to withstand the hostile conditions of a deep ocean current and to reduce maintenance costs.

“Japan isn’t blessed with a lot of alternative energy sources,” he said. “People may say that this is just a dream, but we need to try everything to achieve zero carbon.”

With the cost of wind and solar power and battery storage declining, IHI will also need to demonstrate that overall project costs for ocean current power are competitive. IHI aims to generate power at 20 yen per kilowatt-hour from large-scale deployment. That compares with about 17 yen for solar in the country and about 12-16 yen for offshore wind. IHI also said it conducted an environmental assessment before it launched the project and will use the test results to examine any impact on the marine environment and fishing industry.

If successful at scale, deep ocean currents could add a vital part in providing green baseline power in the global effort to phase out fossil fuels. IHI’s work could help Japan’s engineering take a leading role with government support, said McCrone.

IHI has to make a convincing argument that “Japan could benefit from being a technology leader in this area,” he said.

Translation

（彭博社）—大電量消耗、依賴化石燃料的日本成功地測試了一個系統，該系統可以提供穩定的可再生能源，無論風或太陽如何。

十多年來，日本重型機械製造商 IHI Corp. 一直在開發一種海底渦輪機，該渦輪機利用深海流中的能量並將其轉化為穩定可靠的電力來源。這台巨型機器類似於一架飛機，有兩個反向旋轉的渦輪風扇代替噴氣機，一個中央 “機身” 裝有一個浮力調節系統。這款 330 噸重的原型機名為 Kairyu，設計用於定錨於 30-50 米（100-160 英尺）深度的海床上。

作為商業生產，計劃將渦輪機安裝在沿日本東海岸流動的黑潮, 世界上最強洋流的之一，並通過海底電纜傳輸電力。

東京大學新領域創成科学研究院的海洋技術政策教授高木健說: “洋流在日本的易獲取性方面具有優勢”; “風力發電在地理上更適合歐洲，歐洲主要受西風影響，並且位於高緯度地區” 。日本新能源和工業技術開發組織 (NEDO) 估計黑潮可能產生高達 200 吉瓦的電力，約佔日本目前發電量的 60%。

與其他國家一樣，可再生能源的大部分投資都投向了風能和太陽能，尤其是在福島核災難抑制了該國對原子能的需求之後。日本已經是世界第三大太陽能發電國，並且正在大力投資海上風能，但利用洋流可以提供可靠的基本電力，以減少對儲能或化石燃料的需求。

洋流的優勢在於其穩定性。它的流動的速度和方向幾乎沒有波動，因此它們的容量基數（衡量系統發電次數的指標）為 50-70%，而陸上風能約為 29%，太陽能約為 15%。

在2 月，IHI 與 NEDO 完成了一項為期 3年半的技術示範研究。它的團隊在日本西南部吐噶喇列島周圍的水域測試了該系統。方法是將 Kairyu從船上懸掛入水中在並將電力送回船上。它首先是啓動船以人為地產生電流，然後將渦輪機懸掛入黑潮中。

測試證明該原型可以產生預期的 100 千瓦的穩定電力，該公司現在計劃擴大到一個完整的 2 兆瓦系統，該系統可能在 2030 年代或更晚投入商業運營。

與其他先進的海洋國家一樣，日本正在探索利用海洋能源的各種方式，包括潮汐能和波浪能以及海洋熱能轉換 (OTEC)，OTEC 是利用海表和深海之間的溫差。 Mitsui OSK Lines Ltd. 投資了總部位於英國的 Bombora Wave Power，以探索該技術在日本和歐洲的潛力。據企業營銷部總經理 Yasuo Suzuki 稱，該公司還在推廣 OTEC，並於 4 月開始在沖繩運營一個 100 kW 的示範設施。九州電氣的可再生能源部門 Kyuden Mirai Energy 今年開始進行一項 6.5 億日元（510 萬美元）的可行性測試，以在東海五島群島周圍生產 1 兆瓦的潮汐能。政府本月還提議對海上風電拍賣進行改革，以加速發展。

在海洋能源技術中，向成本效益發展最快的一項是潮汐流技術。前 BloombergNEF 主編兼海洋能源分析師 Angus McCrone 說: “這項技術已經取得了相當長的進步，而且絕對有效”。總部位於蘇格蘭的 Orbital Marine Power 是在歐洲海洋能源中心所在地 Orkney 附近建造潮汐系統的幾家公司之一。其他包括 SIMEC Atlantis Energy 的 MeyGen 部署,和由美國風能先驅 James Dehlsen 創立的位於加利福尼亞的 Aquantis，據報導該公司計劃明年開始在那裡測試潮汐系統。

雖然潮汐流不是 24 小時運行的，但它們往往比深海流強。黑潮以每秒 1 到 1.5 米的速度流動，而某些潮汐系統的流速為每秒 3 米。McCrone說: “洋流渦輪機的最大問題是它們是否可以生產出一種設備, 能夠利用不是特別強的洋流經濟地發電” 。

海洋能源系統 是由國際能源署建立的政府間合作機構，預計到 2050 年，全球有可能部署超過 300 千兆瓦的海洋能源。

但海洋能源的潛力取決於位置，要考慮洋流的強度、電網或市場的接入、保養成本、運送、海洋生物和其他因素。高木說日本的全年波浪能量普通且不穩定，而潮汐強的地區往往航運繁忙。而OTEC更適合溫度升降率較大的熱帶地區。 IHI說，深海流的優勢之一是它不限制船舶航行。

不過，這家日本公司還有很長的路要走。與陸上設施相比，在水下安裝系統要復雜得多。高木說: “與擁有悠久北海石油勘探歷史的歐洲不同，日本在海上建設方面幾乎沒有經驗”。去建立一個足夠強大的系統以承受深海洋流的惡劣條件並降低保養成本是重大的工程挑戰。

他說:“日本沒有很多替代能源”;  “人們可能會說這只是一個夢想，但我們需要盡一切努力實現零碳。”

隨著風能和太陽能以及電池存儲成本的下降，IHI 還需要證明洋流發電的整體項目成本具有競爭力。 IHI 的目標是通過大規模部署以每千瓦時 20 日元的價格發電。相比之下，該國太陽能約為 17 日元，海上風電約為 12-16 日元。 IHI還表示，它在啟動該項目之前進行了環境評估，並將使用測試結果來檢查對海洋環境和漁業的任何影響。

如果在規模上取得成功，深海流可以在全球逐步淘汰化石燃料的努力中為提供綠色基本電力增加重要的組成部分。 McCrone 說，IHI 的工作可以幫助日本的工程在政府支持下發揮主導作用。

他說，IHI 必須提出令人信服的論點，即 “日本可以從成為該領域的技術領導者中受益”。

       So, Japanese heavy machinery maker IHI Corp. has been developing a subsea turbine that harnesses the energy in deep ocean currents. It is a giant machine anchored to the sea floor at a depth of 30-50 meters (100-160 feet) and can transmit the power generated via seabed cables. It is hoped that IHI’s work could help Japan’s engineering take a leading role globally in harnesses the energy in deep ocean currents and converts it into a steady and reliable source of electricity.