WEBVTT - How much coal does a light bulb need to run for a year?

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<v Speaker 1>Welcome to brain Stuff from house stuff works dot com,

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<v Speaker 1>where smart happens. I am Marshall Brain With today's question,

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<v Speaker 1>how much coal is required to run a one hundred

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<v Speaker 1>watt lightbulb twenty four hours a day for a year.

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<v Speaker 1>We can start answering this question by figuring out how

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<v Speaker 1>much energy in kilowatt hours that lightbulb uses in one year.

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<v Speaker 1>To do that, we multiply how much power it uses

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<v Speaker 1>in kilowatts by the number of hours in a year.

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<v Speaker 1>That gives us point one kilowatts times eight thousand, seven

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<v Speaker 1>hundred sixty hours in a year, or eight hundred seventy

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<v Speaker 1>six kilowatt hours for the year. The thermal energy content

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<v Speaker 1>of a typical ton of coal is six thousand, one

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<v Speaker 1>hundred fifty kilowatt hours per ton. Although coal fired power

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<v Speaker 1>plants are very efficient, they're still limited by the laws

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<v Speaker 1>of thermo dynamics, so only about of that thermal energy

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<v Speaker 1>and coal gets converted into electricity by the power plant.

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<v Speaker 1>So the actual electricity generated per ton of coal is

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<v Speaker 1>forty of six thousand, one hundred fifty, or roughly kilowatt

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<v Speaker 1>hours per ton of coal. With a little math, we

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<v Speaker 1>get seven pounds of coal. The light are one hundred

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<v Speaker 1>watt lightbulb for a year. Once you take line losses

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<v Speaker 1>and a few other things into account, it takes about

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<v Speaker 1>a pound of coal to produce a kilowatt hour of

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<v Speaker 1>electricity in round numbers, that's a pretty big pile of coal.

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<v Speaker 1>But let's look at what else gets produced to power

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<v Speaker 1>that light bulb. First of all, there's sulfur dioxide. Coal

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<v Speaker 1>usually contains a little bit of sulfur and it's the

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<v Speaker 1>main cause of acid rain. You get five pounds of

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<v Speaker 1>that when you light a one hundred lightbulb for a year.

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<v Speaker 1>Then there's nitrogen oxides. These cause smog and acid rain.

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<v Speaker 1>They occur when the nitrogen in the area gets heated

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<v Speaker 1>up during the burning process with the coal. You get

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<v Speaker 1>about five pounds of that lighting your light bulb. And

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<v Speaker 1>then you get the carbon dioxide, a greenhouse gas suspected

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<v Speaker 1>of causing global warming. You get one thousand, eight hundred

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<v Speaker 1>fifty two pounds of carbon dioxide emitted into the atmosphere.

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<v Speaker 1>Coal also produces smaller amounts of just about every element

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<v Speaker 1>on the periodic table, including the radioactive ones. In fact,

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<v Speaker 1>a coal burning power plant emits more radiation than a

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<v Speaker 1>properly functioning nuclear power plant. A typical five hundred megawatt

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<v Speaker 1>coal power plant produces three and a half billion kilowatt

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<v Speaker 1>hours per year. That's enough energy for four million of

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<v Speaker 1>our light bulbs to operate year round. To produce this

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<v Speaker 1>amount of electrical energy, the plant will burn something like

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<v Speaker 1>one and a half million tons of coal. Be sure

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