Earth's internal heat, fueled by radioactivity, provides the energy for plate tectonics and continental drift, mountain building, and earthquakes. It can also be harnessed to drive electric generators and heat homes. Geothermal energy becomes available in a practical form when underground heat is transferred by water that is heated as it passes through a subsurface region of hot rocks (a heat reservoir) that may be hundreds or thousands of feet deep. The water is usually naturally occurring groundwater that seeps down along fractures in the rock; less typically, the water is artificially introduced by being pumped down from the surface. The water is brought to the surface, as a liquid or steam, through holes drilled for the purpose.
By far the most abundant form of geothermal energy occurs at the relatively low temperatures of 80° to 180° centigrade. Water circulated through heat reservoirs in this temperature range is able to extract enough heat to warm residential, commercial, and industrial spaces. More than 20,000 apartments in France are now heated by warm underground water drawn from a heat reservoir in a geologic structure near Paris called the Paris Basin. Iceland sits on a volcanic structure known as the Mid-Atlantic Ridge. Reykjavik, the capital of Iceland, is entirely heated by geothermal energy derived from volcanic heat.
Geothermal reservoirs with temperatures above 180° centigrade are useful for generating electricity. They occur primarily in regions of recent volcanic activity as hot, dry rock; natural hot water; or natural steam. The latter two sources are limited to those few areas where surface water seeps down through underground faults or fractures to reach deep rocks heated by the recent activity of molten rock material. The world's largest supply of natural steam occurs at The Geysers, 120 kilometers north of San Francisco, California. In the 1990s enough electricity to meet about half the needs of San Francisco was being generated there. This facility was then in its third decade of production and was beginning to show signs of decline, perhaps because of over development. By the late 1990s some 70 geothermal electric-generating plants were in operation in California, Utah, Nevada, and Hawaii, generating enough power to supply about a million people. Eighteen countries now generate electricity using geothermal heat.
Extracting heat from very hot, dry rocks presents a more difficult problem: the rocks must be fractured to permit the circulation of water, and the water must be provided artificially. The rocks are fractured by water pumped down at very high pressures. Experiments are under way to develop technologies for exploiting this resource.
Like most other energy sources, geothermal energy presents some environmental problems. The surface of the ground can sink if hot groundwater is withdrawn without being replaced. In addition, water heated geothermally can contain salts and toxic materials dissolved from the hot rock. These waters present a disposal problem if they are not returned to the ground from which they were removed.
The contribution of geothermal energy to the world's energy future is difficult to estimate. Geothermal energy is in a sense not renewable, because in most cases the heat would be drawn out of a reservoir much more rapidly than it would be replaced by the very slow geological processes by which heat flows through solid rock into a heat reservoir. However, in many places (for example, California, Hawaii, the Philippines, Japan, Mexico, the rift valleys of Africa)the resource is potentially so large that its future will depend on the economics of production. At present, we can make efficient use of only naturally occurring hot water or steam deposits. Although the potential is enormous, it is likely that in the near future geothermal energy can make important local contributions only where the resource is close to the user and the economics are favorable, as they are in California, New Zealand, and Iceland. Geothermal energy probably will not make large-scale contributions to the world energy budget until well into the twenty-first century, if ever.
Paragraph 1: Earth's internal heat, fueled by radioactivity, provides the energy for plate tectonics and continental drift, mountain building, and earthquakes. It can also be harnessed to drive electric generators and heat homes. Geothermal energy becomes available in a practical form when underground heat is transferred by water that is heated as it passes through a subsurface region of hot rocks (a heat reservoir) that may be hundreds or thousands of feet deep. The water is usually naturally occurring groundwater that seeps down along fractures in the rock; less typically, the water is artificially introduced by being pumped down from the surface. The water is brought to the surface, as a liquid or steam, through holes drilled for the purpose.
1.According to the processes described in paragraph 1, what is the relationship between radioactivity and the steam produced by geothermal heat?
O Geothermally heated steam is produced when water is exposed to radioactivity deep underground.
O When water is introduced into holes drilled thousands of feet in the ground, it becomes radioactive and turns to steam.
O Radioactivity heats Earth's interior rock, which in turn can heat water to the point it becomes steam.
O When a reservoir of steam in subsurface rock is produced by radioactivity, it is said to be geothermally heated.
2.The word "practical" in the passage is closest in meaning to
O usable
O plentiful
O economical
O familiar
Paragraph 2: By far the most abundant form of geothermal energy occurs at the relatively low temperatures of 80° to 180° centigrade. Water circulated through heat reservoirs in this temperature range is able to extract enough heat to warm residential, commercial, and industrial spaces. More than 20,000 apartments in France are now heated by warm underground water drawn from a heat reservoir in a geologic structure near Paris called the Paris Basin. Iceland sits on a volcanic structure known as the Mid-Atlantic Ridge. Reykjavik, the capital of Iceland, is entirely heated by geothermal energy derived from volcanic heat.
3.The word "abundant" in the passage is closest in meaning to
O economical
O familiar
O plentiful
O useful
4.According to paragraph 2, which of the following is true about heat reservoirs with a temperature in the range of 80° to 180° centigrade?
O They are under international control.
O They are more common than reservoirs that have a higher temperature.
O Few of them produce enough heat to warm large industrial spaces.
O They are used to generate electricity.
Paragraph 3: Geothermal reservoirs with temperatures above 180° centigrade are useful for generating electricity. They occur primarily in regions of recent volcanic activity as hot, dry rock; natural hot water; or natural steam. The latter two sources are limited to those few areas where surface water seeps down through underground faults or fractures to reach deep rocks heated by the recent activity of molten rock material. The world's largest supply of natural steam occurs at The Geysers, 120 kilometers north of San Francisco, California. In the 1990s enough electricity to meet about half the needs of San Francisco was being generated there. This facility was then in its third decade of production and was beginning to show signs of decline, perhaps because of over development. By the late 1990s some 70 geothermal electric-generating plants were in operation in California, Utah, Nevada, and Hawaii, generating enough power to supply about a million people. Eighteen countries now generate electricity using geothermal heat.
5.According to paragraph 3, what is the connection between underground faults and naturally occurring steam?
O Underground faults enable the heat from molten-rock material to escape upward to regions where it can heat surface water enough to produce steam.
O Underground faults are created by steam that is produced in geothermal reservoirs deep inside Earth.
O Underground faults create spaces in which natural steam is sometimes trapped.
O Underground faults allow surface water to reach deep rocks that are hot enough to turn it into steam.
6.In paragraph 3, why does the author mention that in the 1990s The Geysers was in its third decade of production?
O To provide the historical context of the geothermal production of electricity in the United States
O To imply that The Geysers was the first geothermal site to be put into production in California
O To help explain the signs of decline shown by The Geysers
O To explain why 70 new geothermal sites were put into electricity production in the late 1990s
7.Which of the following can be inferred from paragraphs 2 and 3 about geothermal reservoirs?
O Volcanic heat is associated only with geothermal reservoirs that have a temperature over 180° centigrade.
O More countries produce power from geothermal reservoirs than use them for heating buildings.
O Most geothermal reservoirs are suitable for producing electricity.
O A higher geothermal reservoir temperature is needed to generate electricity than is needed to heat homes.
Paragraph 4: Extracting heat from very hot, dry rocks presents a more difficult problem: the rocks must be fractured to permit the circulation of water, and the water must be provided artificially. The rocks are fractured by water pumped down at very high pressures. Experiments are under way to develop technologies for exploiting this resource.
8.According to paragraph 4, extracting heat from very hot, dry rocks is difficult in part because
O the underground rock must be fractured before heat can be removed from it
O the water above the rock is under very high pressure
O the rock breaks apart when water is pumped into it
O the water circulated through the rock must be much cooler than the rock itself
9.The word "exploiting" in the passage is closest in meaning to
O locating
O increasing
O making use of
O estimating the size of
Paragraph 5: Like most other energy sources, geothermal energy presents some environmental problems. The surface of the ground can sink if hot groundwater is withdrawn without being replaced. In addition, water heated geothermally can contain salts and toxic materials dissolved from the hot rock. These waters present a disposal problem if they are not returned to the ground from which they were removed.
10.How is the problem that the surface may sink related to the problem that water heated geothermally may contain toxic materials?
O Both problems could be solved by returning groundwater that is removed from an underground heat reservoir back to the reservoir after heat is extracted from it.
O The problem of sinking is more difficult to solve than is the problem of toxic materials.
O Land at the surface sinks because the rock beneath the surface is weakened when salts and toxic materials are removed from it in the process of extracting geothermal energy.
O Both problems are caused by the fact that the hot groundwater in a heat reservoir dissolves the rock, which weakens the rock and makes the water toxic with salt.
Paragraph 6: The contribution of geothermal energy to the world's energy future is difficult to estimate. Geothermal energy is in a sense not renewable, because in most cases the heat would be drawn out of a reservoir much more rapidly than it would be replaced by the very slow geological processes by which heat flows through solid rock into a heat reservoir. However, in many places (for example, California, Hawaii, the Philippines, Japan, Mexico, the rift valleys of Africa)the resource is potentially so large that its future will depend on the economics of production. At present, we can make efficient use of only naturally occurring hot water or steam deposits. Although the potential is enormous, it is likely that in the near future geothermal energy can make important local contributions only where the resource is close to the user and the economics are favorable, as they are in California, New Zealand, and Iceland. Geothermal energy probably will not make large-scale contributions to the world energy budget until well into the twenty-first century, if ever.
11.Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
O Heat flows through solid rock very slowly, so it takes a very long time for geological processes to produce a reservoir of geothermal energy.
O Geothermal energy is not renewable because heat flows very slowly through solid rock into or out of a heat reservoir.
O The heat quickly removed from a heat reservoir is replaced so slowly by geological processes that geothermal energy is not practically speaking, renewable.
O In most cases, heat travels into a heat reservoir so slowfy that it is a much quicker process to remove the heat from a reservoir than to replace it.
12.In paragraph 6, the author implies that in California, Hawaii, the Philippines, Japan, Mexico, and the rift valleys of Africa the potential size of the geothermal resource is so large that
O it might be economically worth developing these sites even though geothermal energy is not renewable
O these sites will be the first geothermal energy sites to be developed with new technology
O these sites are likely to make a large-scale contribution to the world energy budget in the twenty-first century
O it does not matter whether they have naturally occurring deposits of hot water or steam
Earth's internal heat, fueled by radioactivity, provides the energy for plate tectonics and continental drift, mountain building, and earthquakes. It can also be harnessed to drive electric generators and heat homes. Geothermal energy becomes available in a practical form when underground heat is transferred by water that is heated as it passes through a subsurface region of hot rocks (a heat reservoir) that may be hundreds or thousands of feet deep. ■The water is usually naturally occurring groundwater that seeps down along fractures in the rock; less typically, the water is artificially introduced by being pumped down from the surface. ■The water is brought to the surface, as a liquid or steam, through holes drilled for the purpose.■
By far the most abundant form of geothermal energy occurs at the relatively low temperatures of 80° to 180° centigrade. ■Water circulated through heat reservoirs in this temperature range is able to extract enough heat to warm residential, commercial, and industrial spaces. More than 20,000 apartments in France are now heated by warm underground water drawn from a heat reservoir in a geologic structure near Paris called the Paris Basin. Iceland sits on a volcanic structure known as the Mid-Atlantic Ridge. Reykjavik, the capital of Iceland, is entirely heated by geothermal energy derived from volcanic heat.
13.Look at the four squares [■] that indicate where the following sentence could be added to the passage.
In either case, the heated water will usually be under considerable pressure, and so may have a temperature that is well above its sea-level boiling point of 100° centigrade.
Where would the sentence best fit? Click on a square to add the sentence to the passage.
14.Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Heat reservoirs in the form of hot rock far beneath Earth's surface are a potential source of usable geothermal energy.
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Answer Choices
O Heat reservoirs with a temperature from 80° to 180° centigrade can be used, as in France and Iceland, to heat buildings.
O A number of countries now use geothermal reservoirs that contain water or steam above 180° centigrade to generate electricity.
O Most heat reservoirs with a temperature above 180° centigrade cannot be used for energy because they are usually too close to recent volcanic activity.
O The sinking of land above heat reservoirs and other environmental problems arise when water is pumped into a heat reservoir under high pressure.
O Experiments are under way to determine if geothermally heated waters could be used as a source of certain minerals that have been dissolved out of hot rocks deep within Earth.
O A number of issues, including how to extract heat from reservoirs that do not have a natural supply of water, will significantly limit the use of geothermal energy for the foreseeable future.
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14. Heat reservoirs with ...
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地球內(nèi)部因放射產(chǎn)生的熱量為板塊運(yùn)動(dòng)、大陸漂移、造山運(yùn)動(dòng)和地震提供了能量。這種熱量還可以用來驅(qū)動(dòng)發(fā)電機(jī)發(fā)電以及為家庭供暖。水流經(jīng)地表下可能幾百甚至幾千英尺深的熱巖區(qū)域（一種熱儲）被加熱，當(dāng)被加熱的水將熱量傳遞出來時(shí)，地?zé)崮芫涂梢詫?shí)際形式加以利用了。這些水通常是沿著巖石的斷面下滲的天然地下水，少數(shù)情況下是人為從地表泵入的水。通過為了采集地?zé)崮芩@的孔，這些水會以液體或蒸汽的形式被帶到地表。
到目前為止，最豐富的地?zé)崮苄问浇橛谙鄬^低的80到180攝氏度的溫度。在此溫度范圍內(nèi)的熱儲內(nèi)循環(huán)的水可以提取出足夠的熱量供居住區(qū)、商業(yè)區(qū)和工業(yè)區(qū)取暖。目前在法國有20 000間以上的公寓是由溫暖的地下水供暖的，這些地下水來自位于巴黎附近叫做巴黎盆地的地質(zhì)構(gòu)造的熱儲。冰島位于一個(gè)被稱為是大西洋中脊的火山構(gòu)造之上。冰島的首都雷克雅維克完全是用火山熱產(chǎn)生的地?zé)崮芄┡摹?/span>
溫度高于180攝氏度的地?zé)醿瘜涌捎脕戆l(fā)電。這類地?zé)醿瘜又饕挥谟薪诨鹕交顒?dòng)的區(qū)域，以干熱的巖石、天然熱水或天然蒸汽的形式存在。后兩種形式的儲集層局限于少數(shù)區(qū)域，在這些區(qū)域，地表水通過地下斷層或斷裂滲入到被近期的熔巖活動(dòng)加熱的深層巖石。世界上最大的天然蒸汽供應(yīng)位于加州舊金山以北120公里處的蓋沙斯。二十世紀(jì)九十年代，那里產(chǎn)出的電能足夠滿足舊金山半數(shù)的需求。當(dāng)時(shí)該電廠已經(jīng)有三十個(gè)年頭了，開始顯示出發(fā)電量下降的跡象，這可能是由于過度的開發(fā)所致。到二十世紀(jì)九十年代末，加州、猶他州、內(nèi)華達(dá)州和夏威夷約有70個(gè)地?zé)岚l(fā)電廠在運(yùn)轉(zhuǎn)，產(chǎn)生的電能足夠滿足一百萬人的需求。目前有18個(gè)國家在利用地?zé)崮馨l(fā)電。
要從極干熱的巖石中提取熱量存在一個(gè)更大的難題：巖石需要有裂縫才能讓水流通，而且水必須是人工提供的。通過泵入高壓水可以將巖石斷裂。開發(fā)利用此能源的技術(shù)的實(shí)驗(yàn)正在進(jìn)行之中。
就像大多數(shù)其它能源一樣，地?zé)崮芤簿哂幸恍┉h(huán)境問題。如果抽取地下熱水而又不泵回，地表就會下沉。此外，地?zé)峒訜岬乃袕臒釒r中溶出的鹽分和有毒物質(zhì)。這些水如果不能被輸送回抽取的地方，將會產(chǎn)生處理方面的問題。
地?zé)崮軐κ澜缒茉次磥淼呢暙I(xiàn)是難以估量的。地?zé)崮茉谀撤N意義上講是不可再生的，因?yàn)槎鄶?shù)情況下，與熱量流經(jīng)堅(jiān)硬的巖石到達(dá)熱儲這個(gè)極為緩慢的地質(zhì)作用的更新速度相比，從熱儲提取熱量的速度要快得多。不過，在很多地區(qū)（例如加州、夏威夷、菲律賓、日本、墨西哥、非洲的裂谷），這種能源可能非�？捎^，它的前景將取決于經(jīng)濟(jì)的生產(chǎn)。目前，我們只能有效地利用天然形成的熱水或蒸汽形式的地?zé)崮�。盡管潛能巨大，近期之內(nèi)地?zé)崮芸赡苤荒軐ε徲脩粢约敖?jīng)濟(jì)狀況良好的地區(qū)做出重要的局部貢獻(xiàn)，就像在加州、新西蘭和冰島地區(qū)的情況一樣。如果可能的話，地?zé)崮芄烙?jì)要到二十一世紀(jì)才能對世界的能源預(yù)算做出大的貢獻(xiàn)。
