The summer course – the introduction to the introduction – has been interesting so far.
We started off with a discussion of the energy economy: just how much power do humans actually use, anyway? It turns out the answer is quite a lot. We use so much energy that there’s a new vocabulary needed to describe it.
A basic measure of energy consumption in large economies is the Quad, which is shorthand for a quadrillion BTUs. BTU is short for British thermal unit, the amount of energy required to heat one pound of water by one degree Fahrenheit, in a pressure equivalent to the Earth’s air pressure at sea level. The BTU is often used to describe the capacity of a furnace or an air conditioning unit; one BTU is about 1055 joules, or roughly the amount of thermal energy generated by burning a four-inch long wooden match to ash.
A Quad is a million billion BTUs. Put another way, it’s roughly the equivalent of 200 one-megaton thermonuclear bombs, or the amount of energy that would be required to lift this Icelandic volcano to a height of one kilometer higher than its current position:
The world consumes about 500 Quads every year. If we all turned off our appliances (and everything else) and saved all our energy for about 11 months, we could send a mountain up to fly alongside the International Space Station. Which would be a silly and pointless gesture, but still an interesting way of looking at the energy involved.
The US consumes about a fifth of the world’s generated energy. This diagram shows how it’s produced – and how it’s used:
There are a couple of facts illustrated here that I found particularly interesting. The first is that more than three-quarters of the energy consumption in the US comes from oil, coal, and natural gas. These are fossil fuels created by biological and geological processes – processes that converted sunlight millions of years ago into vegetation and other living matter, and have since converted those organic materials into chemical compounds we use to heat our homes and move our cars.
Our economy still is very much based on the light of ancient days.
The other thing I found interesting was the amount of rejected energy – energy produced that isn’t actually used. Typically, this is heat energy, sometimes called waste heat. When you drive a car, for example, only a fraction of the energy stored in the gasoline you use actually makes your car move. Some of the gas winds up as energy that heats the engine or the air that comes out the tailpipe. Most of that energy isn’t used for anything.
More than three-fifths of the energy consumed in the US is similarly wasted. We often think of energy conservation in terms of making products that use less electricity, and that’s one way to approach the problem. Another approach is to capture and put to work more of the energy we otherwise don’t use.
Hybrid cars do this by using regenerative braking systems to power an electric generator when slowing down, rather than relying exclusively on brake pads to slow the car by creating friction; instead of producing waste heat, the car produces and stores electricity for further use.
There are also projects are underway to make commercially-viable thermoelectric generators that can capture the heat of a car’s engine and use it to power the air conditioner or other accessories. We could actually use more energy, at a cost of fewer resources, by finding ways to use the energy we waste throughout our economy.
The lectures have covered a lot of topics so far, as you’d expect from a very basic course: most of the concepts are pretty straightforward. For a non-technical guy the math is a little intimidating, but not unreasonably so.
We even get some field trips – which will be the subject of a later post.
* Who says it can’t be both?