Nuclear or solar? Fracking or tar sands? Pipelines or no pipelines? And what the heck is a kilowatt-hour anyway? Confused? You’re not alone. The world of energy is a strange and complicated place, and like any unfamiliar land, it has a language all its own. In order to become an energy-conscious citizen, you’ve got to speak it, so today we’re going to take a look at the essentials of energy. Often we use the words energy and power interchangeably, but they mean very different things. Energy is a quantity,and we can use that energy to do lots of different things. Power is the rate at which we use that energy. Energy is measured in units like Joules, calories, or the ever-popular British Thermal Unit.
Power is measured in watts, kilowatts, megawatts… or gigawatts. Energy isn’t power, but power times time equals energy, which is why when your bill lists the amount of energy you used in a month, you see kilowatt-hours. If power is energy over time, how much energy would it take to time travel? Accelerating a DeLorean close enough to the speed of light to experience time dilation or simply warping the fabric of space and time at 88 mph would require a lot of energy. In “Back to the Future”, Doc Brown explains that the flux capacitor requires 1.21 jigga-watts to do its thing. 1.21 JIG-A-WATTS! But that’s power, and without knowing over how many seconds those 1.21 gigawatts are being applied, we don’t know how much energy, whether it’s from plutonium, lightning, or garbage-fueled nuclear fusion, is required.
Everything from light bulbs to toasters has a power rating, the amount of energy it needs to consume at any given moment to emit photons or cook pop tarts or whatever. A 100 W light bulb uses 100 Joules of energy every second. Turn it on for an hour, it uses 100 Watt-hours. Newer bulbs have lower ratings because they use less energy to make an equivalent amount of light in the same amount of time. An adult male like me eats 2,500 food calories every day, or about 10.5 megajoules of energy. Burning through those calories over 24 hours means my body operates at about 120 watts. And even though a fifth of that power goes to my brain, I can’t use it to light any actual light bulbs… because even though energy is all around us, and it comes in many forms, not all of it is available for us to use.
And, although we can’t create it, we can move it around from one form to another. It’s energy conversion that drives our energy world, whether it’s turning chemical to electrical, thermal energy to motion, or mechanical to electrical. Unfortunately, the second law of thermodynamics tells us that highly ordered forms of energy will be converted to highly dis-ordered energy. Basically we can’t turn heat and ash back into wood. Because every energy conversion has losses, and because of entropy. That’s a complicated physics answer for why Earth’s energy supplies are bound to decline. A-ha! But luckily our planet isn’t a closed system! The sun’s radiant energy can power solar cells, create wind, and drive precipitation to fill rivers and lakes.
As long as there’s a sun, we’ll have these renewable resources. But renewable or not, there’s inefficiencies at every step of converting energy, and the more times energy is converted, the more those losses multiply. For every 100 units of energy produced by coal, we only get 1.6 units of light energy in our homes. And overall, for every 100 units of energy produced in the US, we lose 60 to waste. ENTROPY!!!! To lower that number, we need to develop more efficient ways to use energy and move it around, better appliances, better vehicles, more efficient buildings, and most of all, more efficient ways to harness energy in the first place. Like how Doc Brown used a lightning strike to power the DeLorean in 1955! Lightning strikes the Earth around 1.4 billion times per year, each bolt can carry 5 billion joules of energy… 30 millionths of a second per bolt… that’s enough to power 137,741 flux capacitors, capable of taking us anywhere we want to go. I wonder what kind of future we’ll decide to make. Stay curious.