Producing enough energy to meet our needs has become a serious problem. Demand is rising rapidly, because of the world’s increasing population and expanding 【Q31】 industry. Burning fossil fuels, like gas, coal and oil, seriously damages the environment and they’ll eventually run out. For a number of years now, scientists have been working out how we can derive energy from renewable sources, such as the sun and wind, without causing pollution. Today I’ll outline marine renewable energy – also called ocean energy – which harnesses the movement of the oceans.
Marine renewable energy can be pided into three main categories: wave energy, tidal energy and ocean thermal energy conversion, and I’ll say a few words about each one.
First, wave energy. Numerous devices have been invented to harvest wave energy, with names such as Wave Dragon, the Penguin and Mighty Whale, and research is going on to try and come up with a really efficient method. This form of energy has plenty of potential, as the source is 【Q32】 constant, and there’s no danger of waves coming to s standstill. Electricity can be generated using onshore systems, using a reservoir, or offshore systems. But the problem with ocean waves is that they’re erratic, with the wind making them travel in every 【Q33】 direction. This adds to the difficulty of creating efficient technology: ideally all the waves would travel smoothly and regularly along the same straight line. Another drawback is that sand and other sediment on the ocean 【Q34】 floor might be stopped from flowing normally, which can lead to environmental problems.
The second category of marine energy that I’ll mention is tidal energy. One major advantage of using the tide, rather than waves, as a source of energy is that it’s 【Q35】 predictable: we know the exact time of high and low tides for years to come.
For tidal energy to be effective, the difference between high and low tides needs to be at least five metres, and this occurs naturally in only about forty places on Earth. But the right conditions can be created by constructing a tidal lagoon, an area of sea water separated from the sea.
One current plan is to create a tidal lagoon on the coast of Wales. This will be an area of water within a 【Q36】 bay at Swansea, sheltered by a U-shaped breakwater, or dam, built out from the coast. The breakwater will contain sixteen hydro turbines, and as the tide rises, water rushes through the breakwater, activating the turbines, which turn a generator to produce electricity. Then, for three hours as the tide goes out, the water is held back within the breakwater, increasing the difference in water level, until it’s several metres higher within the lagoon than in the open sea. Then, in order to release the stored water, 【Q37】 gates in the breakwater are opened. It pours powerfully out of the lagoon, driving the turbines in the breakwater in the opposite direction and again generating thousands of megawatts of electricity. As there are two high tides a day, this lagoon scheme would generate electricity four times a day, every day, for a total of around 14 hours in every 24 – and enough electricity for over 150,000 homes.
This system has quite a lot in its favour: unlike solar and wind energy it doesn’t depend on the weather; the turbines are operated without the need for 【Q38】 fuel, so it doesn’t create any greenhouse gas emissions; and very little maintenance is needed. It’s estimated that electricity generated in this way will be relatively cheap, and that manufacturing the components would create than 2,000 【Q39】 jobs, a big boost to the local economy.
On the other hand, there are fears that lagoons might harm both fish and birds, for example by disturbing 【Q40】 migration patterns, and causing a build-up of silt, affecting local ecosystems.
There are other forms of tidal energy, but I’ll go on to the third category of marine energy: ocean thermal energy conversion. This depends on there being a big difference in temperature between surface water and the water a couple of kilometres below the surface, and this occurs in tropical coastal areas. The idea is to bring cold water up to the surface using a submerged pipe. The concept dates back to 1881, when …
Complete the notes below.
Write ONE WORD ONLY for each answer.
听前预测：定位词 population；提示词 because of、growth；词性：名词。此空所在的句子是一个并列结构并且含有一个表示原因的关系词，可知答案应该是一个与 population 并列的名词。
题目解析：题干中的 more energy required 在文中被替换成了 demand is rising rapidly；because of 原词重现，其后的“the world’s increasing population and expanding industry”直接导出与定位词 population 并列的 industry 这个答案词。此题比较容易，属于得分题。
听前预测：定位词 Wave energy、Advantage；提示词 source；词性：限定词，可以是形容词或者名词。答案应该是一个用来描述 source 的词。
题目解析：此题较难。上一题的答案导出后，文中有大量篇幅在讲题干中的已知信息，答案句出现得较晚，容易使人分神和跟丢。在定位词 Wave energy 原词重现后，出现了大量解释 wave energy 的内容，此处为陷阱，易让同学们以为定位词后马上会有答案，从而出现关注点的偏差。此题的另外一个定位词 Advantage 在文中被替换成了一个比较难辨识的表达方式：“This form of energy has plenty of potential…”，其中 this form of energy 指代的就是 wave energy；has plenty of potential 意为“有很大的潜能”，即 wave energy 的一种优势，可见原文与题干进行了比较隐晦的同义替换。随后，紧接着的“as the source is constant”就是答案句，其中 constant 是用来修饰和限定 source 的，符合听前预测中的词性分析，因此答案为 constant。
听前预测：定位词 Problems、waves；提示词 move、in；词性：名词。此空在一个介词短语后，可知 in any 后面需要接一个名词，来描述波浪运动的方式。
题目解析：此题比较容易定位，同义替换也比较直白。定位词 Problems 原词重现后，答案句“with the wind making them travel in every direction”出现，其中 travel 是题干中的 move 的同义替换，介词短语 in every 刚好与题干中的 in any 结构一致，故答案为 direction。请同学们注意，一般情况下，题干中的挖空部分如果为介词短语结构，答案句中都会含有相同的介词，因为固定搭配的语法结构，很难找到别的表达方式来替换。所以，以后看到此类介词短语题，要多留心，拿下得分点。
听前预测：定位词 sand；提示词 on、ocean；词性：名词。此空在一个 A of B 结构的名词短语中，翻译过来的意思是 B 的 A，可知题干中缺失的是一个由 ocean 限定的核心名词。
题目解析：题干中的 sand 和 on 原词重现，后面紧跟着答案句“that sand and other sediment on the ocean floor might be stopped from flowing”，不难发现被 ocean 修饰的 floor， 即为答案。A of B 结构，即表示从属关系的名词短语，是雅思听力考试中的一处重点，该结构经常会被替换成 B+A 的形式，即 n. + n. 形式的名词词组，如 the floor of the ocean 被替换成 ocean floor。
听前预测：定位词 Tidal energy、Tides；提示词 more…than waves；词性：形容词。此空需要一个形容词来描述 Tides 与 waves 两者之间的比较关系。
题目解析：此题较难。题干中 Tides 与 waves 之间比较直白的比较关系，在文中被转化成了对 tides 的优势的直接表达，即“One major advantage of using the tide, rather than waves, as a source of energy is that it’s predictable…”，此处，需要知道“A is more…than B”（A 比 B 更……）与“the advantage of A, rather than B, is…”（与 B 相比，A 的优势是……）是相同的概念，才能得出答案是 predictable。
听前预测：定位词 tidal lagoon、Wales；提示词 be created、in；词性：名词。此空在一个介词短语后，in a 后面需要接一个名词来描述 tidal lagoon 在 Swansea 的具体位置。
题目解析：此题比较容易定位，同义替换也比较直白。tidal lagoon 和 create 原词重现后，紧接着答案句“This will be an area of water within a bay at Swansea…”出现，其 中介词短语 within a bay at Swansea 刚好与题干中的 in a…at Swansea 结构一致， 因此答案为 bay。
听前预测：定位词 stored water；提示词 is released、through；词性：名词。从题干中的 through 可以分析出此处应填排水所涉及的一种媒介。
题目解析：此题很容易就能判断出答案句为“Then, in order to release the stored water, gates in the breakwater are opened.”。不难看出，题干中的 stored water is released 与 in order to release the stored water 是主被动之间的同义转换；gates are opened 的目的是排水，即 gates 为排水的媒介，因此答案为 gates。
听前预测：定位词 weather；提示词 no、required；词性：名词（因为缺少主语）。
题目解析：此题较为简单，定位词 weather 原词重现后，紧接着答案句“the turbines are operated without the need for fuel”出现，其中 without the need for… 与 no… is required 之间为同义替换，因此答案为 fuel。
听前预测：定位词 create；提示词 a number of；词性：名词（复数）。
题目解析：定位词和答案一起出现，具体对应信息为“manufacturing the components would create more than 2,000 jobs”，其中 more than 2,000 对应题干中的 a number of，所以答案为 jobs。此题不难，但要注意 38 和 39 题之间连接紧密，答案句在文中的位置较近，这就考查了同学们对文章整体节奏的把握和快速反应的能力。
听前预测：定位词 Problem、fish and birds、e.g.；提示词 affecting；词性：名词。题干中的 e.g. 表示答案为前文中 harm fish and birds 的具体例子。
题目解析：通过文中表示转折的 on the other hand 可知，文章内容已经从前文的 advantages 转为叙述 problem 的相关内容了。答案句为“there are fears that lagoons might harm both fish and birds, for example by disturbing migration patterns”，其中定位词 fish and birds 原词重现；for example 与 e.g. 对应；后面的 by disturbing 与题干中的 by affecting 也意思一致，因此答案为 migration。此题答案比较直白，也应是得分题。