水下渦輪機

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隨著技術的進步和對可再生能源的需求變得越來越迫切， 潮汐能可能成為一個更可行的選擇。


Q:美洲大陸架沿線海洋能源的潛在能源輸出估計是多少？
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據估計，美洲大陸架沿線海洋能源的潛在能源輸出可能會提供目前美國能源供應總量的大約一半，西海岸估計為 250 TWh/yr，東海岸為 160 TWh/yr，60 TWh/yr 墨西哥灣，阿拉斯加 620 TWh/年，夏威夷 80 TWh/年，波多黎各 20 TWh/年。


Q:除了潮汐能之外，還有哪些方法可以從海洋中獲取能量？
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除了潮汐能，還有其他方法可以從海洋中獲取能量。 其中包括風推動海洋表面時產生的波浪能，以及主要由風和太陽熱驅動的洋流。 一些系統甚至利用河流和海洋之間的鹽度差異來發電。


Q:與利用潮汐能相關的挑戰有哪些？為什麼世界上的大型潮汐能發電廠如此之少？
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利用潮汐能存在一些挑戰。 首先，建立潮汐能發電廠需要大量的初始投資。
其次，環境對海洋生態系統的影響可能很大，特別是在阻礙海洋生物遷徙模式方面。 這會改變該地區的食物鍊和物種分佈。
第三，潮汐植物的能量輸出受潮汐模式變化的影響，潮汐模式會受到一系列因素的影響，例如天氣模式的影響、月相以及復雜洋流之間的相互作用。
第四，開發商在設計、建
造、安裝和維護各種類型的潮汐能係統和發電所需設備方面面臨著重大的技術和工程挑戰。 由於這些挑戰， 世界上的大型潮汐能發電廠相對較少。 安裝成本高和對環境的重大影響是阻礙潮汐能技術廣泛採用的主要因素。 儘管如此，隨著技術的進步和對可再生能源的需求變得越來越迫切，潮汐能可能成為一些沿海社區更可行的選擇。


Q:那些地區正使用潮汐能
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目前正使用潮汐能的地區. 包括法國的Rance River潮汐能發電廠和韓國的Sihwa Lake潮汐發電廠。此外， 英國、加拿大、澳大利亞和中國等國也正在開發潮汐能發電技術，計畫在未來數年內建立許多潮汐能發電廠。 另外，例如北愛爾蘭的Strangford Lough也有一個可容納小型潮汐渦輪發電機的實驗區域。


Q:潮汐能跟波浪能.有何差別
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潮汐能和波浪能都是海洋能源， 但是它們的產生原理和收集方式有很大的差別。 潮汐能是利用潮汐運動的水流產生的動能發電，可以預測性地收集潮汐帶來的水流運動能量，它的能量來源於海洋和月球引力的相互作用。 另一方面， 波浪能是利用波浪的運動能量發電，因為波浪的變化具有隨機性和不可預測性，所以它的收集比潮汐能更具挑戰性，需要先進的技術和設備來收集波浪的能量。 潮汐能可以在固定的海域內準確收集能量，並且在周期性的潮汐變化中有較為穩定的產能表現，在可預測的周期內提供穩定的能源。 波浪能則需要更高的技術難度以及更複雜的控制系統來克服波浪的不可預測性，以保證波浪能的穩定性和可控性， 因此，相對來說，潮汐能更容易被實現和推廣。


00 This episode of Real Engineering is brought to you by Brilliant. A problem solving website 0:04 that teaches you to think like an Engineer. 0:07 Next time you’re near the ocean, listen closely to the waves. That sound you hear? 0:12 That’s wasted energy. 0:14 The energy from waves, tides and currents, known collectively as ocean energy, is a massive 0:20 resource just waiting to be tapped. 0:23 The total energy available along the American continental shelf could potentially provide 0:28 roughly half of the current total US energy supply. [1] With an estimated 250 TWh/yr for 0:37 the West Coast, 160 TWH/yr for the East Coast, 60 TWh/y for the Gulf of Mexico, 620 TWh/y 0:44 for Alaska, 80 TWh/yr for Hawaii, and 20 TWh/yr for Puerto Rico. [1] 0:48 Harassing all of that energy, while transporting it to population centres and finding suitable 0:53 locations along the coast that will not affect coastline ecosystems and property values would 0:58 be a difficult if not an impossible task, but if we could find a suitable way to harass 1:04 the power of the tides and waves off our coasts, it could provide the final push needed to 1:09 convert out grid to a 100% renewable system [2] 1:14 There are many methods to gain energy from the sea. Wave power is created as the wind 1:19 pushes the surface of the ocean. Ocean currents provide power driven predominantly by wind 1:25 and heat from the sun. Some systems have even utilized the differences in salinity between 1:30 rivers and seas to produce electricity. 1:33 However, today we are going to investigate one of the most promising technologies in 1:37 this sector, Tidal Energy. It has huge potential in the renewable energy market thanks to its 1:43 predictable and consistent availability. Tides change four times a day, every day. 1:50 This is a result of the Earth rotating through bulges of ocean water formed by the gravitational 1:55 influence of the Sun and Moon. We experience greater tides, called Spring Tides, when the 2:00 Sun is aligned with the Moon allowing their gravitational influence to combine. [3] This 2:05 corresponds to the New and Full Moon phases of the Moon. And we experience smaller tides, 2:11 and smaller differences in high and low tide, during Neap Tides. This occurs when the Moon 2:16 is at a quarter phase, offset to the Sun by 90 degrees. Meaning our tides are not only 2:22 smaller in total, but the changes in tide are minimised. 2:27 While their intensity does vary, these tidal changes come 4 times a day and result in a 2:31 flow of water that will look something like this for a Spring Tide and this for a Neap 2:36 Tide. [4] With the Spring Tide not only resulting in a higher tide, but a faster flow of water, 2:43 which means more energy is available for extraction. 2:47 These patterns can be projected well into the future thanks to the predictable movement 2:51 of the Sun, Moon and Earth. Which definitely cannot be said for the unpredictable weather 2:57 here on earth which affects Wind and Solar energy. 3:01 Despite this steady and reliable flow of water, ocean power provides the smallest percentage 3:06 of renewable energy. With only two large scale tidal energy plants, a 240 MW system [5] located 3:14 in the estuary of the Rance River in Northern France, and a 254 MW system in Sihwa Lake 3:21 in South Korea [6]. Both are tidal barrage systems, which work similarly to dams by opening 3:27 and closing sluice gates to control the flow of water through their turbines. This is a 3:32 proven technology, proving they can generate electricity and operate in seawater without 3:38 corrosion being a massive issue thanks to cathodic protection. [7] 3:42 So why are there so few of these systems in the world. The problem is two-fold. First, 3:48 the cost of installation is incredibly high requiring a very large structure to control 3:53 the flow of water. It simply makes more sense to use other forms of renewables like wind 3:58 and solar. And second, a large barrier like this has a significant effect on the local 4:04 ecosystem. 4:06 One company, Simec Atlantis, is looking to improve on both of these points with their 4:11 underwater turbines which look remarkably like normal wind turbines, but thanks to water's 4:16 higher density can be much smaller. 4:20 Their first prototype system was placed here in the mouth of Strangford lough in Ireland. 4:25 This area benefits from some of the fastest flowing water in Ireland, as tides force their 4:30 way in and out of the bottleneck of Strangford Lough. Millions of tonnes of water flow through 4:36 the channel every day. [8] 4:38 The system consisted of two 16 metre diameter turbines with a nameplate capacity of 0.6 4:45 MWs each. [8] For reference an equivalent wind turbine would have a diameter around 4:51 40 metres. These turbines reached full capacity in November 2008 and were decommissioned in 4:57 May 2016. [9] If that 1.2 MWs ran continuously at full capacity for all that time it would 5:05 result in about 77-79 GWhs of power, however it only produced 11.6 GWhs. [10] Enough to 5:14 power around 1 thousand American homes for 1 year, but that’s just 15% of its full 5:21 potential. That percentage is called a capacity factor and 15% is a very low capacity factor, 5:28 with Ireland’s 5 year average wind energy capacity factor standing around 28%. [11] 5:35 However this was a prototype which did not run continuously and was routinely taken offline 5:41 for inspection and research. In their best month, SeaGen produced 522 MWhs with a capacity 5:49 factor of 59% and Seagen claim that is reproducible year round. [12] With a capacity factor of 5:57 59% year round this would make tidal energy an incredibly reliable energy source with 6:03 only minimal storage needed to smoothen out the peaks and troughs between the tides. With 6:09 a short time between peak power generation and minimum power generation, this form of 6:14 tidal energy could use cheaper short-term energy storage solutions like mechanical batteries 6:21 to create a desperately needed renewable baseload. 6:25 This project was decommissioned in 2016, as part of the research process. It was vitally 6:31 important to test whether these machines could be effectively removed from the environments 6:37 with minimal impact. [13] And this is of course a major concern for any machinery being placed 6:42 into a marine environment. Seagen satisfied this requirement having no significant effect 6:48 on the local ecosystem, and they have since moved onto the next stage of their technology 6:54 with Meygen, installed in between the Island of Stroma and the North East coast of Scotland. 7:00 Their original lease agreement was for up 400 Megawatts, provided the initial testing 7:05 phase with 4 turbines satisfied the environmental impact requirements. [14] 7:11 The latest version of the underwater turbine now has 3 turbine blades, allowing for an 7:16 increase in capacity to 1.5 MegaWatts with only a slightly increased diameter turbine 7:22 over the 16 metre 0.5 MegaWatt turbines of their previous project in Northern Ireland. 7:29 This turbine is also completely submerged, so it is not an eyesore for local residents. 7:35 Seagen previously had actuators to lift the turbine out of the water to allow maintenance 7:40 to occur, but the new generation of turbines are designed so the actual turbines and generators 7:46 can simply be placed and removed from the substructure in about 30 minutes. [15] Making 7:51 installation and maintenance vastly easier and cheaper. 7:56 Environmental impact has been a central focus for the project and this started with a comprehensive 8:02 survey of the surrounding ecosystem from seaweed and shellfish to the whales that occasionally 8:08 visit the area. 8:09 The area thankfully has such fast moving water that the seabed was stripped of sand and silt, 8:15 so the installation had little impact on ecology of the rocky seafloor. 8:20 The impact the installation could have on local marine mammals was of much larger concern 8:26 with surveys showing a large population of both seals and dolphins, with several haul 8:31 out areas for seals nearby. [16] Both of these mammals are sensitive to noise and will likely 8:37 avoid any area with excessive sound. The noise levels these turbines emit are not terribly 8:43 high, as they move relatively slowly through the water. Their 544 page long environmental 8:49 report, which I read to the best of my ability in the 1 week of research I did for this video, 8:55 indicates that seals will have a strong avoidance of the noise within 38 metres of the structures, 9:01 while mild avoidance may extend as far as 168 metres. [17] With seal haulouts over a 9:07 kilometre away this was deemed acceptable. While dolphins are expected to avoid the noise 9:12 up to 100 metres and filter feeders like whales up to 500 metres, which may remove a small 9:19 section of sea from use, but will not act as a barrier to any significant feeding ground. 9:25 A significant improvement over tidal barrages. 9:28 This theory is backed up by surveys conducted during Seagen’s operation which found little 9:34 evidence that the two turbines had a significant effect on the numbers of seals and dolphins 9:39 during operation, but did have an effect during the construction phase where noise was much 9:45 higher. [18] 9:46 Area avoidance would be useful in the fact that it would prevent the animals from straying 9:50 too close to the turbines and being struck by them. Potentially hurting themselves and 9:55 damaging the turbine. Once again we can garner some positive data from Seagen, which examined 10:00 all carcasses discovered near the site and found no evidence that any deaths were caused 10:06 by impacts to the turbines. [19] 10:08 This seems unlikely but they theorize that these animals actually avoid the areas while 10:12 the turbine is operating not because of sound, but because the water is flowing fast enough 10:17 to make it too difficult to swim and catch prey. 10:20 The last major worry for these types of devices is the fact that they need to use toxic anti-fouling 10:26 coatings to prevent marine growth on the turbines. However Meygen uses a clever low friction 10:32 paint that self cleans as soon as the marine growth grows large enough where the drag overcomes 10:37 their ability to adhere to the slippery paint. 10:41 Additionally they trialed a sonar detection system that would allow them to track and 10:45 potentially stop the turbines when larger animals occasional pass through the area. 10:50 Without a doubt, these types of turbines would have less of an impact on the environment 10:55 than tidal barrages seen in France and South Korea, but only time will tell whether this 11:00 system in the far reaches of Scotland will have a small enough impact to encourage additional 11:05 systems to be installed. 11:08 Cost will still be a massive factor. Based on their companies financial reports the Meygen 11:12 project generated 2.7 million dollars of revenue for the company in 2018. That’s 0.675 million 11:20 dollars of revenue from each turbine. Based on their estimated cost for a further 49 turbines 11:26 at 540 million dollars, we can calculate that each would come with an installation cost 11:32 of around 11 million dollars, so that would require 16.3 years to recoup the cost of installation. 11:39 Which is better than the 20 years it took to recoup the costs of tidal barrage system 11:43 in France, and those numbers will likely continue to drop if the company manages to start manufacturing 11:49 these underwater turbines on a larger scale. 11:52 But it’s slow going. Iterating and improving on designs for tidal power is much more difficult 11:58 than other forms of renewable energy. Testing has to take place in coastal waters, most 12:04 of which are public spaces, requiring extensive permitting and testing. 12:08 It’s unlikely that these underwater turbines will ever compete on cost with onshore wind 12:13 turbines or solar, but thanks to the predictability of the tides this form of energy could provide 12:19 a reliable baseload when combined with low cost batteries. 12:24 If this project succeeds if could justify large scale manufacturing of these turbines 12:29 and transform tidal energy from a small niche industry, to a huge player in the renewable 12:35 energy industry. 12:37 After all, Meygen is just one small section of a larger 1600 MW ocean energy project earmarked 12:45 for Pentland Firth and Orkney, with mixes of both wave and tidal energy.[20] 12:50 A colossal amount of energy which could go a long way to diversifying Scotland’s power 12:55 usage, and we will delve into the world of wave energy in a future video. 13:01 In the meantime, you can learn more about other forms of renewable energies like solar 13:05 by watching some of my past videos on the topic, or taking this course on solar energy 13:10 on Brilliant. 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