The Engineering Challenges of Renewable Energy

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Engineering has given a lot to the world. It's transformed the nature of work, improve sanitation and help create vital infrastructure. The bad news is that to power the tools and processes behind those developments, we've relied on non renewable fuels, the kind that get produced at a much slower rate than we use them. As the name implies, non renewables won't be around forever. Resources like oil and natural gas might be gone in just half a century. And using them has been, frankly, pretty terrible for the environment. 87% of the harmful carbon dioxide emitted by humans in the last 50 years has come from burning fuels such as coal, oil and natural gas, known collectively as fossil fuels. It's been terrible for the atmosphere, in oceans, and is changing our climate in dangerous ways. Whether we like it or not, we're going to have to find new ways to power our world, despite their terrible effects on the environment and limited supply. For now, non renewables do a really good job of meeting our energy needs. In 2017, 80% of the power used in the United States for supplied using fossil fuels. And the need for energy doesn't appear to be shrinking any time soon. Another 9% is delivered from nuclear vision, the process of splitting atoms, which releases far less CO2. Unfortunately, fission produces radioactive waste and also relies on non renewable fuel sources such as uranium and plutonium. All of these methods operate on broadly the same principle, essentially operating as a heat engine. A working fluid, often water, is heated by the fuel to expand and do work turning the blades of a turbine. The turbine is connected to an electrical generator that converts the rotational motion of the blades into electrical power, which has then fed into the grid. So what about the remaining 11% of power that came from renewable energy sources, the kind that are generated about as fast as we use them. Some of the major renewable energy sources come from processes that are naturally occurring on earth, wind power, solar power, hydropower, which is based on flowing water, and geothermal power, which uses the heat of the earth deep underground. None of these sources, the things will run out of We have a good few billion years left of sunlight, E.G. And what's more, renewable energy tends to release fewer harmful byproducts like carbon dioxide, into the environment. Take hydro power, e.g., which converts the kinetic energy from the motion of running water into electrical power in a fast flowing river Run of river power plant diverts, part of the rivers flow, sometimes through a tunnel to turn the turbines of a generator. That works well in some places. But the problem with this approach is that it's tricky to control the generation of energy to meet demand. You don't want to put lots of power into the grid when it won't get used, and you want to be able to ramp up the supply when the demand suddenly spikes, like during the half time break, when the English football team that sockety you Americans played Columbia in the 2018 World Cup, a huge number of people in the UK open their refrigerators to grab a drink or a snack, causing the compresses inside them to turn on. Then there were the people who had already had a bunch of drinks. All those people simultaneously flushing their toilets during the break created an increased demand for power on the local pumping stations that maintain pressure in the water system. The total increase in demand was measured to be 1200 mw. That's an extra demand for power equivalent to several power plants. With fossil fuels, you can control the amount of fuel being burned and therefore the amount of power being produced. One of river power plants struggle with this because the amount of power they generate depends on the flow of the river, which in turn depends on things like the rainfall during the time period and even the temperature, both things we can't control. To get around this, the more common form of hydropower is a hydroelectric dam. In this case, you can install a dam that floods an area and creates a huge reservoir of water. The water then falls through the generators turbines at the bottom of the dam, which turn the water's kinetic energy into power. If you install an intake valve that opens or shots to control the water flow through it, you can even manage the production of energy to meet the changing demands of the electrical grid. Unfortunately, flooding an area with water isn't consequence free, changing the environment so suddenly and preventing the natural flow of water downstream can have devastating consequences for the local ecology. There's also the risk of the dam breaking if it was built improperly. Despite those challenges, hydropower has been enormously helpful in recent years. It produces as much as 16% of the world's energy and up to 70% of all the world's renewable energy. The other renewable energy source that works in a similar way to hydro power is wind power, which also uses turbines. The main difference is that the flu don't work on the wind turbines is air instead of water. One of the biggest engineering challenges here is designing the turbine blades to efficiently extract energy from that air. As we saw were fluid mechanics, Predicting the flow of a fluid around an object can get seriously tricky. Blades have to be engineered to withstand the stress the subjected to, while also allowing the wind to efficiently rotate them to power the generator. It's as complicated as designing an airplane wing. Once again, you run into the problem of demand. You can't control the strength of the wind to increase or decrease power generation as you need it. Even if that were possible, you'd still have to transport it from the sparsely populated open plains, where the wind blows more easily, to dense urban centers with low amounts of wind, but high demand for power. Transporting that power becomes even trickier over long distances, because you lose some energy as the electricity travels through the wires. For that reason. In others, engineering considerations often play a big role in deciding where wind farms, as a collection of turbines is known, should be built. So wind power has only generated 4% of the world's total power supply in recent years. Location also plays an important role in another renewable energy source geothermal power. Like conventional power plants, geothermal power relies on steam as the working fluid on the turbines connected to the generator. But in this case, you don't need fuel to generate the steam. You can drill into underground deposits of hot volcanic rocks, normally near the Earth tectonic plate boundaries, to use them as a heat source for a power plant. Then all you need is to pump water to that location and create another channel for steam to rise through to do work on the turbines. The biggest problem comes with setting up a geothermal power plant in the 1st place. It can be expensive to drill and explore for underground conditions that are exactly right, and is only really possible in certain parts of the world, like Iceland and Italy. But there's one source of renewable energy that's so abundant and easily accessible you only have to step outside on a bright, sunny day to see it, solar energy. In fact, the amount of sunlight the Earth receives in just a single year is twice the total amount of energy that will ever be extracted from fossil fuels and the uranium used in nuclear fission combined. The challenge is finding efficient ways to harness that energy, because turning sunlight into electricity isn't simple. The most promising technology we have is called the photo voltaic or simply PV cell. Most people know them by the name given to many cells arranged together solar panels. Unlike everything else we've looked at, there's no trace of a turbine wine here. Instead, as we saw when looking at semiconductors, solar panels used two different semiconducting pieces to set up an electrical field that biases the movement of free electrons inside the material in a particular direction. In short, the materials encourage an electrical current to flow when they receive energy, which then travels through the circuit, delivering power to whatever is connected to the PV cell. That means solar panels can deliver power directly to the grid. Between that and the abundance of sunlight, it seems like there shouldn't be an energy shortage problem at all. But as we've seen for the other energy sources, costs, fluctuating demand, location and transmission, all factor in here. For starters, solar cells aren't all that efficient. The very best solar cells can convert 40% of the energy they absorb into electrical power. But they're expensive to produce because of the high quality of silicon needed in manufacturing, among other reasons. On average, industrial PV cells were about 17% efficient. Once you factor in the cost of making the cells and energy storage, solar power ends up being anywhere between three and six times as expensive to produce. Is that from fossil fuels. Increasing solar panels efficiency would bring this down dramatically. Another big challenge for solar power is that, like with the hydroelectric dam, you need a way to store energy, to control the production. In line with power demands, you won't generate much solar power on a cloudy day, whereas you might have a surplus on sunny days, but you can't store sunlight directly. Instead, engineers are working on ways to temporarily store that extra solar power. These include solutions like batteries, or even pumping water up a column to later give up its energy as hydro power during periods of high demand. Once again, though, efficiency plays a big role in making both these methods a suitable form of energy storage. Despite the efficiency and storage problems, there is one major advantage to solar panels. They can be deployed pretty much anywhere. Rather than having to transmit power across long distances, solar panels can simply be installed on smaller scales, close to areas of demand, even on the roof of an individual home. But manufacturing the panels themselves brings its own set of issues. One of the more materials used to currently make solar panels is caught, which has to be processed to produce the high quality silicon needed for making PV cells. This itself is an energy intensive process, which offsets some of the total energy production of solar panels across their lifetime of usage. Even worse, processing courts can often produce toxic by products like tetcher chloride, which can end up spilling into the environment and causing damage to soil. That all sounds a little bleak, but the most difficult challenges in engineering are often the most important ones. In fact, the National Academy of Engineering in the US has identified making solar energy more economical is one of the grand challenges that engineers in the 20 onst century need to solve. Future engineers have lots of ways to contribute towards making solar more feasible. Currently, researchers are looking at new storage systems, such as using solar power to drive hydrogen fuel production, which can be burned later on with no carbon dioxide emissions. More on that next time. Engineers are also introducing new materials into production of solar panels and improving the ways in which PV cells themselves are linked and arranged on the panels. There are even experimental methods being developed that use new structures on a molecular level called nano crystals. These increase the amount of energy given to the electrons and the material when light is absorbed, instead of losing the energy is heat. So that could drive the efficiency high enough to make it economically competitive with current power sources and increase the adoption of solar worldwide. So there are lots of challenges ahead in bringing renewable energy sources to the forefront of electrical power production, but that's all the more space for future engineers to have an impact and create new solutions to the world's energy needs. In this episode, we looked at renewable energy sources and why we need them. We looked at how hydropower, wind, geothermal and solar power are used to produce electricity. Some of the challenges face in doing so. In the areas engineers are working on to make their use more widespread. And our next episode will see how engineers have moved beyond natural processes to invent entirely new ways of generating power. Critical engineering has produced in association with PBS Digital Studios, which also produces Ions, a series that journeys through the history of life on Earth, with paleontology and natural history. Ions takes you from the dawn of life to the so called age of dinosaurs, and right up to the end of the most recent ice age crash. Course, is a complexly production, and this episode was filmed in the Doctor Charles c Kinney studio, with the help of these wonderful people, and our amazing graphic team. Is Thought Cafe.?

譯文：

????????????????可再生能源的工程挑戰(zhàn)

工程給世界帶來了很多。它改變了工作的性質(zhì)，改善了衛(wèi)生條件，幫助建立了重要的基礎(chǔ)設(shè)施。壞消息是，為這些工具提供動力在這些發(fā)展背后的過程中，我們依賴的是不可再生燃料，這種燃料的生產(chǎn)速度要慢得多然后我們使用它們。顧名思義，非可再生能源不會永遠存在。像石油和天然氣這樣的資源可能在半個世紀內(nèi)就會消失。坦率地說，使用它們對環(huán)境非常糟糕。在過去50年里，人類排放的有害二氧化碳中有87%來自燃燒煤炭、石油和天然氣等統(tǒng)稱為化石燃料的燃料。這對大氣和海洋來說都是可怕的，并且正在以危險的方式改變我們的氣候。不管我們喜歡與否，我們都必須找到新的方式來為我們的世界提供動力，盡管它們對環(huán)境造成了可怕的影響，而且供應(yīng)有限。目前，非可再生能源在滿足我們的能源需求方面做得很好。2017年，美國80%的電力供應(yīng)來自化石燃料。而且對能源的需求在短期內(nèi)似乎不會減少。另外9%來自核視覺，即原子分裂的過程，釋放的二氧化碳要少得多。不幸的是，裂變會產(chǎn)生放射性廢物，并且依賴于不可再生的燃料來源，如鈾和钚。所有這些方法的運作原理大致相同，本質(zhì)上就像熱機一樣運作。一種工作流體，通常是水，被燃料加熱膨脹并做功轉(zhuǎn)動渦輪機的葉片。渦輪機與發(fā)電機相連，發(fā)電機將葉片的旋轉(zhuǎn)運動轉(zhuǎn)化為電能，然后送入電網(wǎng)。那么剩下的11%的電力來自可再生能源，這種能源的產(chǎn)生速度和我們使用的速度一樣快。一些主要的可再生能源來自于地球上自然發(fā)生的過程，如風(fēng)能、太陽能、水力發(fā)電(基于流動的水)和地?zé)崮?利用地下深處的地球熱量)。這些資源都不會用完，我們還有幾十億年的陽光更重要的是，可再生能源傾向于釋放更少的有害副產(chǎn)品，如二氧化碳，進入環(huán)境。以水力發(fā)電為例，它在湍急的河流中將流水運動的動能轉(zhuǎn)化為電能。河流發(fā)電廠使部分河流改道，有時通過隧道來轉(zhuǎn)動發(fā)電機的渦輪機。這在一些地方很有效。但這種方法的問題在于，它很難控制能源的產(chǎn)生以滿足需求。你不想在電網(wǎng)不用的時候向電網(wǎng)投入大量電力，你想在需求突然激增的時候增加供應(yīng)，比如在中場休息期間，當英國足球隊在2018年世界杯上擊敗你們美國人對陣哥倫比亞隊時，英國有很多人打開冰箱拿飲料或零食，導(dǎo)致冰箱里的壓縮裝置打開。還有一些人已經(jīng)喝了很多酒。所有這些人都在休息期間同時沖洗廁所，這增加了當?shù)乇谜镜碾娏π枨螅跃S持供水系統(tǒng)的壓力。據(jù)測量，總需求增加了1200兆瓦。這對電力的額外需求相當于幾個發(fā)電廠。有了化石燃料，你就可以控制燃燒的燃料量，從而控制發(fā)電量。其中一個河流發(fā)電廠與此斗爭，因為它們產(chǎn)生的電量取決于河流的流量，而河流的流量又取決于時間段內(nèi)的降雨量甚至溫度，這些都是我們無法控制的。為了解決這個問題，更常見的水力發(fā)電形式是水電站大壩。在這種情況下，你可以建一個大壩，淹沒一個地區(qū)，形成一個巨大的水庫。然后，水通過大壩底部的發(fā)電機渦輪，將水的動能轉(zhuǎn)化為電能。如果你安裝一個可以打開或關(guān)閉的進氣閥來控制流經(jīng)它的水流，你甚至可以管理能源的生產(chǎn)，以滿足不斷變化的電網(wǎng)需求。不幸的是，用水淹沒一個地區(qū)并不是沒有后果的，如此突然地改變環(huán)境，阻止水的自然流向下游，可能會對當?shù)氐纳鷳B(tài)造成毀滅性的后果。如果修建不當，大壩還存在潰壩的風(fēng)險。盡管存在這些挑戰(zhàn)，水力發(fā)電近年來還是大有幫助。它生產(chǎn)的能源占全球的16%，可再生能源占全球的70%。另一種與水力發(fā)電原理相似的可再生能源是風(fēng)力發(fā)電，它也使用渦輪機。主要的區(qū)別是流感對風(fēng)力渦輪機不起作用的是空氣而不是水。這里最大的工程挑戰(zhàn)之一是設(shè)計渦輪葉片以有效地從空氣中提取能量。正如我們在流體力學(xué)中看到的，預(yù)測物體周圍流體的流動是非常棘手的。葉片的設(shè)計必須能夠承受承受的壓力，同時還要允許風(fēng)有效地旋轉(zhuǎn)葉片，為發(fā)電機提供動力。這就像設(shè)計飛機機翼一樣復(fù)雜。你又遇到了需求的問題。你不能根據(jù)需要控制風(fēng)力來增加或減少發(fā)電量。即使這是可能的，你仍然需要把它從人口稀少的開闊平原運輸?shù)饺丝诿芗某鞘兄行模抢镲L(fēng)更容易吹，但風(fēng)力較少，但對電力的需求很大。長時間輸送電能變得更加棘手距離，因為當電流通過導(dǎo)線時你會損失一些能量。因為這個原因。在其他情況下，工程方面的考慮往往在決定風(fēng)力發(fā)電場(一組已知的渦輪機)應(yīng)該建在哪里時起著重要作用。因此，近年來風(fēng)力發(fā)電僅占世界總電力供應(yīng)的4%。地理位置在另一種可再生能源地?zé)岚l(fā)電中也起著重要作用。與傳統(tǒng)發(fā)電廠一樣，地?zé)岚l(fā)電廠依靠蒸汽作為與發(fā)電機相連的渦輪機的工作流體。但在這種情況下，你不需要燃料來產(chǎn)生蒸汽。你可以鉆到熱火山巖的地下沉積物中，通常在地球構(gòu)造板塊邊界附近，把它們用作發(fā)電廠的熱源。然后你所需要做的就是把水抽到那個位置，創(chuàng)造另一個通道，讓蒸汽上升，對渦輪機做功。最大的問題是首先要建立一個地?zé)岚l(fā)電廠。鉆探和勘探地下條件的成本可能很高，而且只有在世界上的某些地方才有可能，比如冰島和意大利。但有一種可再生能源非常豐富，而且很容易獲得，你只需要在陽光明媚的日子走到外面就能看到它，那就是太陽能。事實上，地球在一年內(nèi)接收到的陽光是從化石燃料和核裂變中使用的鈾中提取的總能量的兩倍。挑戰(zhàn)在于找到有效的方法來利用這種能量，因為將陽光轉(zhuǎn)化為電能并不簡單。我們擁有的最有前途的技術(shù)被稱為光伏電池或簡稱PV電池。大多數(shù)人都知道它們是由許多排列在一起的電池組成的太陽能電池板。不像我們看過的其他東西，這里沒有渦輪酒的痕跡。相反，正如我們在觀察半導(dǎo)體時看到的那樣，太陽能電池板使用兩種不同的半導(dǎo)體片來建立一個電場，使材料內(nèi)部的自由電子向特定方向運動。簡而言之，當材料接收到能量時，就會產(chǎn)生電流，然后通過電路，將能量傳遞給連接到光伏電池上的任何東西。這意味著太陽能電池板可以直接向電網(wǎng)輸送電力。再加上充足的陽光，似乎根本不應(yīng)該有能源短缺的問題。但正如我們所看到的其他能源，成本，波動的需求，位置和傳輸，都是這里的因素。首先，太陽能電池并不是那么高效。最好的太陽能電池可以將吸收的能量的40%轉(zhuǎn)化為電能。但它們的生產(chǎn)成本很高，因為制造過程中需要高質(zhì)量的硅，還有其他一些原因。工業(yè)光伏電池的平均效率約為17%。一旦你考慮到制造電池和能量儲存的成本，太陽能的生產(chǎn)成本最終將是太陽能的3到6倍。是來自化石燃料。提高太陽能電池板的效率將大大降低這一比例。太陽能發(fā)電的另一個巨大挑戰(zhàn)是，就像水電站大壩一樣，你需要一種儲存能量的方法，來控制生產(chǎn)。根據(jù)電力需求，在陰天你不會產(chǎn)生太多的太陽能，而在晴天你可能會有盈余，但你不能直接儲存陽光。相反，工程師們正在研究暫時儲存額外太陽能的方法。這些解決方案包括電池，甚至將水抽到一個柱子上，然后在高需求時期將其能量轉(zhuǎn)化為水力發(fā)電。然而，再一次，效率在使這兩種方法成為合適的能量存儲形式方面起著重要作用。盡管存在效率和存儲問題，但太陽能電池板有一個主要優(yōu)勢。它們幾乎可以部署在任何地方。太陽能電池板可以簡單地安裝在更小的范圍內(nèi)，靠近有需求的區(qū)域，甚至安裝在單個家庭的屋頂上，而不必長距離傳輸電力。但是制造太陽能電池板本身也帶來了一系列問題。目前用于制造太陽能電池板的更多材料之一是捕獲，它必須經(jīng)過加工才能生產(chǎn)出制造光伏電池所需的高質(zhì)量硅。這本身就是一個能源密集型的過程，它抵消了太陽能電池板在其使用壽命期間產(chǎn)生的一些總能量。更糟糕的是，加工法院往往會產(chǎn)生有毒的副產(chǎn)品，如氯離子，最終會泄漏到環(huán)境中，對土壤造成破壞。這一切聽起來有點凄涼，但工程中最困難的挑戰(zhàn)往往是最重要的挑戰(zhàn)。事實上，美國國家工程院(NationalAcademyofEngineering)已經(jīng)確定，使太陽能更加經(jīng)濟是21世紀工程師需要解決的重大挑戰(zhàn)之一。未來的工程師有很多方法可以使太陽能變得更可行。目前，研究人員正在研究新的儲存系統(tǒng)，比如利用太陽能驅(qū)動氫燃料的生產(chǎn)，氫燃料可以在以后燃燒而不排放二氧化碳。下次再詳細講。工程師們還在太陽能電池板的生產(chǎn)中引入了新材料，并改進了光伏電池本身連接和排列在電池板上的方式。甚至有正在開發(fā)的實驗方法，在分子水平上使用稱為納米晶體的新結(jié)構(gòu)。當光線照射時，這些增加了給予電子和材料的能量吸收，而不是失去的能量是熱。因此，這可以將效率提高到足以使其在經(jīng)濟上與現(xiàn)有的能源競爭，并增加全球?qū)μ柲艿牟捎?。因此，在將可再生能源推向電力生產(chǎn)的前沿方面，我們面臨著許多挑戰(zhàn)，但這也為未來的工程師提供了更多的空間，他們可以發(fā)揮影響，為世界能源需求創(chuàng)造新的解決方案。在這節(jié)課中，我們探討了可再生能源以及我們?yōu)槭裁葱枰鼈儭Ｎ覀冄芯苛怂?、風(fēng)能、地?zé)岷吞柲苁侨绾伪挥脕戆l(fā)電的。這樣做會面臨一些挑戰(zhàn)。在這些領(lǐng)域，工程師們正在努力使它們的應(yīng)用更加廣泛。下一集我們將看到工程師們?nèi)绾纬阶匀贿^程，發(fā)明全新的發(fā)電方式。《關(guān)鍵工程》是與PBS數(shù)字工作室合作制作的，PBS數(shù)字工作室還制作了《離子》系列節(jié)目，講述了地球上生命的歷史，包括古生物學(xué)和自然史。離子帶你從生命的開端到所謂的恐龍時代，一直到最近一次冰河時代崩潰的結(jié)束。當然，這是一個復(fù)雜的制作過程，這一集是在查爾斯·c·金尼醫(yī)生的工作室拍攝的，得到了這些了不起的人的幫助，還有我們出色的圖像團隊。是思想咖啡館。