本篇文章共分 8 段，從海洋儲存巨大能量，到包含潮汐發電等四種可能的能量轉化方式，一一說明各種方法的必備條件與可能的發展前景。

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Electrical Energy from the Ocean 來自海洋的電能

1. 海洋能源儲量高

   Solar energy reaching Earth is responsible for differential heating of the atmosphere and thus air circulation as wind. Some of the energy of wind is transferred to the oceans, where it causes waves and is partly responsible for oceanic currents, although Earth's rotation also plays a role in currents. Gravitational attraction between Earth and the Sun and Moon generates tides and, along with Earth's rotation, causes most coastal areas to experience a twice-daily rise and fall of sea level. In short, the oceans possess a tremendous reservoir of largely untapped energy.

   到達地球的太陽能負責對大氣層進行不同程度的加熱，從而使空氣循環成為風。風的一些能量被轉移到海洋中，在海洋中引發波浪，並對洋流造成部分影響，儘管地球的自轉也對洋流起著作用。地球與太陽和月亮之間的引力產生潮汐，並與地球自轉一起，使大多數沿海地區經歷每天兩次的海平面上升和下降。簡而言之，海洋擁有一個大部分是未開發能源的巨大的能量庫。

2. 四種可能發展

   If we could effectively harness the energy possessed by the oceans, an almost limitless, largely nonpolluting energy supply would be ensured. Unfortunately, ocean energy is diffuse, meaning that the amount of energy for a given volume of water is small and thus difficult to concentrate and use. Several ways of using ocean energy are being considered or are under development, and one is currently in use, although it accounts for only a tiny proportion of all energy production. Of the several sources of ocean energy—temperature differences with depth, currents, waves, and tides—only the last shows much promise for the near future.

   如果我們能有效地利用海洋所擁有的能量，就能確保幾乎無限的、基本無污染的能源供應。不幸的是，海洋能源是分散的，這意味著一定體積的水的能量很小，因此難以集中和使用。有幾種利用海洋能源的方法正在考慮或正在開發中，其中一種目前正在使用，儘管它只佔所有能源生產的極小部分。在海洋能源的幾種來源中—隨深度變化的溫差、海流、海浪和潮汐—只有最後一種在不久的將來顯示出很大的前景。

3. 溫差發電條件

   Ocean water at depth might be as much as 25° C colder than surface water, a difference that allows for ocean thermal energy conversion (OTEC). OTEC exploits this temperature difference to run turbines and generate electricity. The amount of energy available is enormous, but a number of practical problems must be solved before it can be used. For one thing, any potential site must be close to land and also have a sufficiently rapid change with depth to result in the required temperature difference. Furthermore, enormous quantities of warm and cold seawater would have to circulate through an electrical-generating plant, thus requiring that large surface areas be devoted to this purpose.

   海洋深處的水可能比表面的水冷 25°C，這種差異使海洋熱能轉換（OTEC）成為可行。OTEC 利用這種溫差來運轉渦輪機與發電。可用的能量相當巨大，但在使用之前必須解決一些實際問題。首先，任何潛在的地點必須靠近陸地，並且有足夠快的深度變化，以導致所需的溫差。此外，大量的冷暖海水必須在發電站中循環流動，因此需要有廣大的地表面積用於此目的。

4. 溫差發電現況

   The concept of OTEC is more than a century old, but despite several decades of research, no commercial OTEC plants are operating or even under construction, although small experimental ones have been tested in Hawaii and Japan.

   OTEC 的概念已經有一個多世紀的歷史，但是儘管有幾十年的研究，目前並沒有商業的 OTEC 工廠在運行，甚至也沒有在建造當中，儘管在夏威夷和日本已經測試了小型的實驗性工廠。

5. 洋流發電

   Wind-generated ocean currents, such as the Gulf Stream, which flows along the east coast of North America, also possess energy that might be tapped to generate electricity. Unlike streams that can be dammed to impound a reservoir, any electrical generating facility exploiting oceanic currents would have to concentrate currents’ diffuse energy and contend with any unpredictable changes in direction. In addition, whereas hydroelectric generating plants on land depend on the rapid movement of water from a higher elevation to the turbines, the energy of ocean currents comes from their flow velocity, which is at most a few kilometers per hour.

   風產生的洋流，如沿北美東海岸流動的墨西哥灣灣流，也擁有可能被利用來發電的能量。與可以築壩蓄水的溪流不同，任何利用洋流的發電設施都必須集中洋流的擴散能量，並與任何不可預知的方向變化作競爭。此外，陸地上的水力發電站依賴於水從高處向渦輪機的快速移動，而洋流的能量來自於其流速，最多為每小時幾公里。

6. 波浪發電

   The most obvious form of energy in the oceans lies in waves. Harnessing wave energy and converting it to electricity is not a new idea, and it has been used on an extremely limited scale. Unfortunately, the energy possessed by a wave is distributed along its crest and is difficult to concentrate. Furthermore, any facility would have to be designed to withstand the effects of storms and saltwater corrosion. The Japanese have developed wave-energy devices to power lighthouses and buoys, and a facility capable of providing power to about 300 homes began operating in Scotland during September 2000.

   海洋中最明顯的能源形式在於波浪。利用波浪能並將其轉換為電能並不是一個新的想法，而且已經在極其有限的範圍內使用。不幸的是，波浪所擁有的能量是沿著波峰分佈的，很難集中。此外，任何設施的設計都必須能夠承受風暴和鹽水腐蝕的影響。日本已經開發了波浪能裝置，為燈塔和浮標供電，2000 年 9 月，一個能夠為大約 300 個家庭提供電力的設施開始在蘇格蘭運行。

7. 潮汐發電條件

   Perhaps tidal power is the most promising form of ocean energy. In fact, it has been used for centuries in some coastal areas to run mills, but its use at present for electrical generation is limited. Most coastal areas experience a twice-daily rise and fall of tides, but only a few areas are suitable for exploiting this energy source. One limitation is that the tidal range must be at least five meters, and there must also be a coastal region where water can be stored following high tide.

   也許潮汐發電是最有前途的海洋能源形式。事實上，幾個世紀以來，它在一些沿海地區已經被用來運行磨坊，但目前用於發電的情況有限。大多數沿海地區經歷了每天兩次的潮汐上升和下降，但只有少數地區適合開發這種能源。一個限制是，潮汐範圍必須至少有五米，而且還必須有一個沿海地區可以在漲潮後儲水。

8. 潮汐發電限制

   Suitable sites for using tidal power are limited not only by tidal range but also by location. Many areas along the U.S. Gulf Coast would certainly benefit from tidal power plants, but a tide range of generally less than one meter precludes the possibility of development. Even areas with an appropriate tidal range such as the Arctic islands of Canada offer little potential because of their great distances from population centers.

   適合使用潮汐發電的地點不僅受到潮汐大小的限制，而且還受到地點的限制。美國墨西哥灣沿岸的許多地區肯定會受益於潮汐發電站，但潮汐大小通常小於一米，這就排除了開發的可能性。即使是具有適當潮汐範圍的地區，如加拿大的北極島嶼，也因為距離人口中心很遠而沒有潛力。