Welcome back. Module 3 covers energy vocabulary and literacy. In this lecture, we'll introduce the

Transcription

1 UTx S-991gOZGPk [MUSIC PLAYING] Welcome back. Module 3 covers energy vocabulary and literacy. In this lecture, we'll introduce the language of energy, including specialized terminology, units, conversions, and data sources. So let's get started. Now, let's talk about energy vocabulary and information literacy. I've already started to use specialized terms in units and energy figures and values. So it's important that we understand what those mean as a part of the background for the class. The goal is to make you fluent in energy, and so you need to know what the vocabulary is. Let's start with the words. Energy has its own vocabulary. It has its own words. Now, one of the key distinctions is the difference between energy and power. People often use energy and power interchangeably, but they mean different things. Energy is a quantity. It's the ability to do work. Power is a rate. It's work over time, or energy over time. Power is a measure of how quickly something is being done or how quickly energy is being consumed. And we'll walk through these examples because one of the most important points of the class is to takeaway this difference. Energy has many units. It has scientific units, things like BTU, or British Thermal Units; or a quad, which is a quadrillion BTU. There's also joules or kilojoules and megajoules and calories. In electricity, we use things like kilowatt hour or megawatt hour or gigawatt hour. So we have different units that are both scientific for fuels and for electricity. And then we have these proxy units, things like barrels of energy, or barrels of oil equivalent of energy, or cubic feet of energy. And that usually assumes a particular volumetric energy density. It's more of an industry term than a scientific term. We also of mass-based energy terms, things like a ton of energy, or a kilogram of energy, or a kilogram of energy equivalent, or a kilogram of oil equivalent of energy. These are all mass-based proxies based on the gravimetric energy density that we might assume. Again, an industry term, not a scientific term. So there's different units and unfortunately, industry and government and different people all use

2 different terms. They don't use all the same units, and that's one of the complicating factors of following the energy industry. Now, power is a rate of energy. Power is work performed over a period of time. It's energy produced over a period of time, energy consumed over a period time. It's a rate, not a quantity and has units of things like watts, kilowatts, megawatts, gigawatts. It has things like horsepower. And this raises the point that kilowatts of energy is nonsensical. You could kilowatts of power or kilowatt hours of energy, but not kilowatts of energy. And if you know this vocabulary and you read the energy literature or if you read newspaper articles, you will see mistakes in the press, or in the analysis of energy that confuses these terms quite often. Now, there's a related term to power, which is power density, watts per square meter. That's important for things like heat flux density or solar insulation or radiation or irradiance, which is important for things like solar energy. So we have power, or power densities, all of which are important. This is all a part of the vocabulary of energy. Now, we can relate the two. Energy equals power times time. For example, a light bulb consumes energy at a rate of about 100 watts. In fact, we used to buy light bulbs by their power rating, 100 watt light bulb was a measure of how quickly it was consuming energy. It was its power rating. Its instantaneous power consumption is 100 watts, which means after 1 hour, it has consumed 100 watt hours, or 0.1 kilowatt hours. After 10 hours, it has consumed 1 kilowatt hour. So we can go back or forward between power and energy using this relationship. Just to put it in context, a typical house, its power consumption in the United States is roughly 1 to 4 kilowatts. And a human's nominal power consumption, for example my power consumption while speaking right now, is about 100 watts. And I can convert how much energy I am using over a day into power, or back and forth using this relationship, energy equals power times time. We can take another example, a large one. Instead of a light bulb, a nuclear power plant. A nuclear plant has something like a capacity of 1 gigawatt. After 1 hour, it generates 1 gigawatt hour of electricity. After a year, which has 8,760 hours, it has generated 8,760 gigawatt hours of electricity. And we can convert that to kilowatt hours. 1 gigawatt hour is a million kilowatt hours. And kilowatt hours is a typical unit for electricity.

3 In the total US, electricity generation in 2011 was about 4,000 billion kilowatt hours. And we could see what fraction of that was produced by just one nuclear power plant. A non-zero fraction, not enough. We need many more than one nuclear power plant to generate all the electricity the United States needs. But we can figure that out based on this relationship between the capacity and power of the power plant and the energy produced over time. There's also a difference between primary and secondary energy. Primary energy are those fuels that are unconverted or original and secondary energy are those that are converted or stored. So the primary energy source are things like petroleum, natural gas, coal, biomass, hydro, wind, solar, that kind of thing. And the secondary energy is energy that's been converted, like electricity. We don't mine for electricity. We don't harvest electricity. We generate electricity as a secondary form from the primary fuels, like natural gas. It's also hydrogen, which we don't mine for in nature, but we might make hydrogen from natural gas or electrolysis of water, or it's pumped hydroelectric, or any energy storage. So there's a difference between energy and power, and there's a difference between primary and secondary energy. There's also energy notation. We have different terms we use to keep track of the quantities of energy. And I've put in this table different columns that are useful for this. One is the scientific prefix, things like milli for a thousandth. Like a millimeter is a thousandth of a meter. A centimeter, or centi, is one hundreth. A deci is a tenth. Deca is 10. Hecto, a hundred. A kilo is a thousand, like a kilometer. And then mega is a million, giga is a billion, tera is a trillion, that kind of thing. So I've listed the scientific prefix, its name, its multiplier, and the English explanation of what it is. But there's something tricky here, which is some parts of world also use Roman numerals. And particularly, the United States uses Roman numerals as well. And the X stands for 10, the C stands for 100, and the M stands for 1,000. Well, if you look on this chart, C shows up two places. C shows up as C for a hundredth and C shows up in Roman numerals as a hundred, which is different by a factor of 10,000. You also have m for milli and M for Mega. Little m is one thousandth. Big M is a million. That's different by a billion, nine orders of magnitude difference. Then you also have big M, mega, and big M, Roman numeral. The big M, mega, is a million and the big

4 M Roman numeral is a thousand. Three orders of magnitude difference. So when you see units in energy, you might see a capital M. And you don't know if that means milli, mega, or Roman numeral thousand. And this is part of the confusion, keeping track of all the unit's notation. And so as a consequence, it's easy to get the wrong number, to be off by orders of magnitude. There are some rules of thumb. Generally, for the electricity world, the scientific prefixes use M for mega, like megawatts, MW, which is a million watts. In the liquid fuels world, Roman numerals are often used. MM, thousand thousand, which means a million. So MMBTU means a million BTU, or a thousand times a thousand BTU. Or MMBLS is a million blue barrels, or a thousand thousand barrels. And a blue barrel by the way, is a 42 gallon barrel of oil. Or MMBD is million barrels per day. That's one way to think about it. But then you have other journals or articles or news magazines that use different notation. The Economist uses little mbd for million barrels per day. I looked at that and think that's a thousandth of a barrel per day. But it's actually a million barrels per day. Some people use BOE, like Barrels Of Energy, or Barrels Of Oil Equivalent, like the BP Statistical Review uses that approach. Some people use MMBDOE. So there's all these different terms and all these units and all these notations. It's very easy to get confused. So you have to keep track of it so you get the right numbers. Now, we get lucky along the way. There's a lot of confusion that makes it bad for us. But there's actually some fortunate conversions as well. For example, there's one for natural gas. The energy content of a thousand standard cubic feet of natural gas is approximately a million BTU. A standard cubic foot is an scf. An mcf is a thousand cubic feet. Now, some people call that a little mcf, or a big M little cf, or little m-i-l, mil, which means not a million but a thousand cubic feet. Although, some people think of that as a thousandth of an inch if you're a machinist. And some people think of it as a million dollars, so it gets very confusing. There's about a thousand BTU per cubic foot. If we had a thousand cubic feet, that's about a million BTU per thousand cubic feet. So price is often given for natural gas in MCF or a million BTU. It's the same thing. The energy content is only different by about 3%. So someone might say, what's the price of gas today? It's about $4. And they don't tell you it's about $4 per MCF, or $4 per million BTU. They just say it's about $4, but it works out to be the same. So it's just good luck, good fortune that that conversion works out that way.

5 We have some other fortunate conversions, like tons. A ton is about a tonne. A ton, T-O-N, is the English ton, which is 2,000 pounds-- a short ton. The tonne, T-O-N-N-E is a metric ton, is a thousand kilograms. But a kilogram is 2.2 pounds. So a metric tonne is 1,000 kilograms is 2,200 pounds, is 1.1 English tons. So 1 metric tonne is about 1 English ton within about 10%. This is crazy, we just got lucky. We don't deserve it to work out that well. And this becomes important when we talk about tons of coal shipped or tons of oil or tons of carbon emissions, where people say the United States admitted 6 gigatons of carbon dioxide, but don't tell you whether it's English tons or metric tons. And that difference is 10% might matter to some people. Anyway, it's close enough for now to at least get in the right order of magnitude, and that's just good fortune. There's also some large-scale energy units that are closely matched. An exajoule and a quad are about the same thing. An exajoule is a quintillion joules, or 1 times 10 to the 18 joules. And we have in the English system, a quad, a quadrillion BTU, which is 1 times 10 to the 15 BTU. So it's a billion billion. BTU is a quad. And a billion billion joules is an exajoule. But it turns out 1 exajoule is about 0.95 quads. So 100 quads is about 105 exajoules. It's about the same. So you can do the metric to English diversions for large-scale energy units in your head and impress people at cocktail parties. Another thing to keep in mind is that the data sources matter. Energy is highly politicized, so you have to pay attention to the source. You have to think about where you're getting your energy information from. And there's a guide for evaluating sources. Think about your authoritative sources, governmental agencies, the industry and trade associations. NGOs and watch dog groups all have data sources and they're mostly accurate, but they might have different agendas. You have to keep track of that. And they don't all agree. Here are some of the ones I use. I use things like the Annual Energy Outlook or Annual Energy Review from the Energy Information Administration in the United States. You could also use information from the International Energy Agency. BP Statistical Review is industry standard. So you have several authoritative sources of energy to use that are all quite good. They don't always agree, so keep that in mind. They have different assumptions or standards by which they collect the data. So this is a challenge. And you have to be real careful because there's so many political outcomes and desired objectives by different groups that data will try to be steered by different people. So you have to think carefully about what data you're looking at and whether you believe it.

6 Make sure you come back for the next lecture. But in the meantime, go online, do the exercises, and they'll reinforce all the concepts and the things we talked about this time on this topic. [MUSIC PLAYING]