Energy Resources and Consumption
AP Environmental Science Topic 6 9:13 English narration · English + 中文 subtitles burned in
Chapters
Transcript
Look at this hole in the ground.
看看地上这个大坑。
A machine digs out soft brown coal, and the power station behind it burns it the same day.
机器把褐色的软煤挖出来，紧挨着的发电站当天就把它烧掉。
Now look at this: three towers on a farm, turning wind into the same electricity.
再看这一幅：农田上的三座塔，把风变成同样的电。
Both light one room.
它们点亮的是同一盏灯。
This unit is about that choice, and its cost.
本单元讲的就是这个选择，以及它的代价。
Here is the plan.
本节的安排是这样的。
First, what makes a source renewable or not.
首先，什么样的能源算可再生，什么样的不算。
Then fossil fuels, and how a power station makes electricity.
然后是化石燃料，以及发电站如何发电。
Then nuclear, and the half-life maths the exam sets.
接着是核能，以及考试要考的半衰期计算。
Then solar and wind.
然后是太阳能和风能。
Then hydro and geothermal.
再然后是水电和地热。
And last, biomass and using less.
最后是生物质，以及少用能源。
Start with the split everything hangs on.
先看那条决定一切的分界线。
It is a race between two rates: how fast we use a resource, and how fast nature replaces it.
它是两个速率的赛跑：我们使用资源的速度， 和自然补充它的速度。
A renewable source refills as fast as we take it: sunlight, wind, new plants.
可再生能源补充的速度和我们取用的速度差不多， 比如阳光、风和新长出的植物。
A nonrenewable source took millions of years to form, so once burned it is gone.
不可再生能源的形成要几百万年，所以一旦烧掉就没有了。
Fossil fuels are non-renewable, and still give about eighty percent of world energy.
化石燃料是不可再生的，而且仍然提供全世界约百分之八十的能源。
Now, who uses what.
再看谁在用、用什么。
About eighty percent of the energy we use is still oil, coal and gas; nuclear, hydro and the newer renewables share the rest.
我们所用能源的约百分之八十仍然是石油、煤和天然气； 核能、水电和较新的可再生能源分掉剩下的部分。
But use is not even.
但使用并不均衡。
A rich country uses many times more energy per person than a poor one, and as poorer countries industrialise their demand climbs.
富裕国家人均用掉的能源，是贫穷国家的许多倍；而随着较穷的国家工业化， 他们的需求还在攀升。
The resources themselves are unevenly distributed too — they sit where ancient geology put them, not where the people are, and that drives trade and geopolitics.
燃料也只待在远古地质把它们放下的地方，而不是人所在的地方。
Different fuels suit different jobs: coal and gas for electricity, oil for transportation, biomass for heating and cooking.
不同的燃料适合不同的用途。
In many places wood and charcoal are still the everyday fuel.
在许多地方，木柴和木炭仍是日常燃料。
Peat is partly rotted plant matter: dry it, and it burns.
泥炭是部分腐烂的植物物质：把它晒干，就能燃烧。
Bury peat deeper, and heat and pressure make coal.
把泥炭埋得更深， 热和压力就把它变成煤。
Coal comes in ranks.
煤分等级。
Lignite, the soft brown coal, is lowest.
褐煤，也就是软的棕色煤，等级最低。
Bituminous is harder.
烟煤更硬。
Anthracite is hardest and richest in carbon.
无烟煤最硬，含碳量也最高。
Natural gas is the cleanest fossil fuel, mostly methane.
天然气是最清洁的化石燃料，主要成分是甲烷。
Here is the machine at the centre of this unit.
这就是贯穿整个单元的那台机器。
Burn a fuel, and the heat boils water into steam.
烧燃料，热把水烧成蒸汽。
The steam pushes a turbine, the turbine spins a generator, and that makes electricity.
蒸汽推动涡轮机，涡轮机带动发电机，这样就发出了电。
Now watch the first box.
现在看第一个方框。
Swap coal for uranium: a nuclear station.
把煤换成铀，它就是核电站。
Swap it for hot rock: geothermal.
换成地下的热岩，它就是地热电站。
Only the heat source changes.
变的只是热源。
Solar panels, wind and fuel cells skip the steam completely.
太阳能电池板、风力和燃料电池则完全不需要蒸汽。
So, fossil fuels.
那么，化石燃料。
They are buried life: plants and plankton pressed for millions of years into coal, oil and gas.
它们是被埋起来的生命：植物和浮游生物被挤压了几百万年， 变成煤、石油和天然气。
We mine the coal and pump the oil and gas, and more and more we use hydraulic fracturing — fracking — forcing fluid into shale rock to crack it open.
我们开采煤，抽取石油和天然气； 而且越来越多地采用水力压裂，把液体高压注入页岩把它压裂。
It can contaminate groundwater and release volatile organic compounds, and oil can even be dug from tar sands, where it is thick bitumen mixed with clay and sand.
水力压裂可能污染地下水，并释放挥发性有机物；石油甚至可以从油砂中分离出来。
Burning any of them gives carbon dioxide.
燃烧它们中的任何一种，都会产生二氧化碳。
Nuclear power burns nothing.
核能什么都不烧。
A neutron strikes a uranium nucleus and splits it.
一个中子撞上铀原子核，把它劈开。
That is fission, and it gives enormous heat from very little fuel.
这就是核裂变，它用极少的燃料放出巨大的热量。
So there is almost no greenhouse gas and no air pollutant.
所以几乎没有温室气体，也没有空气污染物。
But uranium is not renewable, the waste stays radioactive for thousands of years, and the warm cooling water is thermal pollution.
但铀不是可再生的，核废料的放射性会持续几千年，而排出的温水就是热污染。
Here is the reaction itself.
这就是那个反应本身。
A slow neutron, on the left, strikes a uranium nucleus.
左边一个慢中子撞上铀原子核。
The nucleus becomes unstable and splits into two smaller nuclei, here barium and krypton.
原子核变得不稳定， 裂成两个更小的核，这里是钡和氪。
Two or three fresh neutrons fly out, able to split more uranium.
两到三个新的中子飞出来，可以再去劈开更多的铀。
And energy is released: huge heat from very little fuel.
同时释放能量：极少的燃料放出巨大的热。
The waste is the hard part, and half-life is how we measure it.
废料才是难处，而半衰期就是我们衡量它的方式。
Watch this grid of unstable nuclei.
看这一格格不稳定的原子核。
In one half-life, about half of them decay.
一个半衰期里，大约一半会衰变。
In the next, half of what is left decays again, not half of the original.
下一个半衰期里，剩下的再衰变一半，而不是原来的一半。
The count falls sixty-four, thirty-two, sixteen, eight, and never quite reaches zero.
数目从六十四降到三十二、十六、八，却始终到不了零。
Now the calculation.
现在来算一算。
A reactor leaves one hundred grams of an isotope whose half-life is thirty years.
一座反应堆留下一百克某种同位素，它的半衰期是三十年。
How much is left after ninety years?
九十年后还剩多少？
Pause here and try it yourself.
先暂停，自己算一遍。
First count the half-lives: ninety divided by thirty is three.
第一步数半衰期：九十除以三十等于三。
Now halve three times. Fifty grams, then twenty-five, then twelve point five grams.
然后减半三次：五十克，再二十五克，再十二点五克。
The trap is subtracting instead of halving.
陷阱是做减法，而不是减半。
Biomass is energy stored in living matter: wood, crop waste, dung.
生物质是储存在生物体中的能量：木材、作物残渣、粪便。
It is renewable if you replant.
只要补种，它就是可再生的。
But burning gives carbon dioxide, carbon monoxide, nitrogen oxides and particulates, and cutting too many trees causes deforestation.
但燃烧仍然产生二氧化碳、一氧化碳、氮氧化物和颗粒物；砍伐过多的树木还会造成森林砍伐。
Ferment sugar crops and you get ethanol, a substitute for petrol.
把含糖作物发酵，就得到乙醇，可以替代汽油。
Ethanol adds no new carbon, but it has a low EROEI — a low energy return on energy investment, because growing and distilling the crop uses nearly as much energy as the fuel delivers.
乙醇不增加新的碳，但它的能量回报很低。
Cleaner still is the hydrogen fuel cell: its only product is water.
更干净的是氢燃料电池：它的唯一产物是水。
Two renewables that need no fuel.
两种完全不需要燃料的可再生能源。
Photovoltaic cells turn sunlight straight into electricity, and at night you need storage or backup.
光伏电池把阳光直接变成电， 而到了夜里就需要储能或备用电源。
Active solar heating pumps a liquid through collectors; passive solar just lets a building soak up the sun.
主动式太阳能供热用泵把液体送过集热器； 被动式太阳能则只是让建筑本身吸收阳光。
Wind turbines use moving air to spin a generator.
风力涡轮机用流动的空气带动发电机。
Both are clean, but both are intermittent, and solar farms take a lot of land.
两者都很清洁，但都是间歇性的，而且太阳能电场要占用大量土地。
Two more, and both are steady.
再看两种，而且都很稳定。
A hydroelectric dam holds a reservoir behind a wall and drops water through turbines; tidal turbines are spun by the tide.
水电大坝把水库拦在墙后，让水落下穿过涡轮机； 潮汐涡轮机则由潮水推动。
Hydro makes no air pollution and no waste, but it is expensive, floods a valley and blocks fish.
水电不产生空气污染，也没有废料， 但造价高、会淹没山谷，还会阻断鱼类。
Geothermal taps the Earth's own heat: water goes down and comes back as steam.
地热利用地球自身的热量：水注下去， 再变成蒸汽回来。
It runs day and night, but only where hot rock is shallow.
它日夜都能运行，但只适用于热岩埋得浅的地方。
A hydrogen fuel cell is not a battery and not a fire.
氢燃料电池不是电池，也不是燃烧。
Hydrogen goes in one side, oxygen the other.
氢气从一侧进入，氧气从另一侧进入。
The hydrogen gives up its electrons; they cannot cross the electrolyte, so they travel round the outside wire instead, and that flow is the electricity.
氢放出电子；电子无法穿过电解质，只好绕到外面的导线上走，这股电子流就是电。
They meet the oxygen, and the only thing that comes out is water.
它们与氧相遇，出来的唯一物质是水。
The catch is upstream: most hydrogen is made from fossil fuels.
问题出在上游：今天大多数氢仍然由化石燃料制取。
Energy conservation is the cheapest, cleanest option: the energy you never use needs no fuel and makes no pollution.
最便宜、最干净的能源，是你根本不用的那一份。
At home: turn the thermostat down, fit LED bulbs, buy efficient appliances, insulate.
在家里：把恒温器调低，换上LED灯泡， 买高效电器，做保温。
Nationally: better fuel economy, electric and hybrid cars, public transport, green buildings.
在全国层面：提高燃油经济性，用电动车和混合动力车， 坐公共交通，建绿色建筑。
And one clever trick, cogeneration.
还有一个巧办法，热电联产。
A normal station wastes its heat; a cogeneration plant pipes that heat to nearby buildings, so one fuel gives electricity and heat.
普通电站把废热白白扔掉； 热电联产电站把这些热送到附近的建筑，于是一份燃料既给出电，也给出热。
One more calculation.
再算一道。
Replace a sixty-watt bulb with a ten-watt LED, used five hours a day.
把一只六十瓦的灯泡换成十瓦的LED，每天用五小时。
How much does one bulb save in a year?
一只灯泡一年能省多少？
Pause here and try it yourself.
先暂停，自己算一遍。
The power saved is sixty minus ten: fifty watts.
省下的功率是六十减十，等于五十瓦。
Times five hours is two hundred and fifty watt-hours a day.
乘以五小时，就是每天二百五十瓦时。
Divide by a thousand: nought point two five kilowatt-hours.
除以一千，得到零点二五千瓦时。
Times three hundred and sixty-five is about ninety-one kilowatt-hours a year.
再乘以三百六十五，约等于每年九十一千瓦时。
Three marks students throw away.
三个学生常丢的分。
First, half-life: after three half-lives an eighth is left, not nothing.
第一，半衰期：过了三个半衰期还剩八分之一，而不是什么都不剩。
Halve, never subtract.
要减半，不要相减。
Second, never name a source without naming its cost: solar and wind are intermittent, hydro floods habitat, nuclear leaves long-lived waste.
第二，说出一种能源，就一定要说出它的代价： 太阳能和风能是间歇性的，水电会淹没栖息地，核能留下长寿命废料。
Third, show every unit step: watts times hours, then divide by a thousand.
第三，把每一步单位换算都写出来：瓦乘以小时，再除以一千。
Five things to take with you.
带走五件事。
First, renewable sources refill on a human timescale; fossil fuels and nuclear fuel do not.
第一，可再生资源按人类时间尺度补充；化石燃料和核燃料不会。
Second, about eighty percent of world energy is still fossil, and the fuels sit where geology put them, not where the people are.
第二，全球能源大约八成仍是化石燃料，而且燃料在地质放它们的地方，不在人多的地方。
Third, never name a source without its cost: solar and wind are intermittent, hydro floods habitat, nuclear leaves long-lived waste.
第三，说出一种能源，一定要说出代价：太阳能和风能是间歇的，水电淹没栖息地，核能留下长寿命废料。
Fourth, half-life halves: after three half-lives an eighth remains.
第四，半衰期是减半：过了三个半衰期还剩八分之一。
Fifth, conservation is often the cheapest option, and cogeneration captures waste heat so one fuel gives electricity and heat.
第五，节能常常是最便宜的选择，而热电联产把废热也用上，一份燃料既发电又供热。
Ethanol adds no net carbon but has a low energy return on the energy invested.
乙醇不增加净碳，但能量回报很低。