Today’s graphic is special type of flow chart, called a Sankey diagram.
This particular one shows the total estimated energy consumption in the United States in 2015, and how energy flowed from source to the final destination. The graphic comes to us from the Lawrence Livermore National Laboratory and the Department of Energy.
The beauty of a Sankey is in its simplicity and and effectiveness. No information is left out, and we can really see the full energy picture from a 10,000 foot view.
The U.S. is estimated to have consumed 97.5 quads of energy in 2015.
What’s a quad? It’s equal to a quadrillion BTUs, which is roughly comparable to any of these:
-- 8,007,000,000 gallons (US) of gasoline
-- 293,071,000,000 kilowatt-hours (kWh)
-- 36,000,000 tonnes of coal
-- 970,434,000,000 cubic feet of natural gas
-- 25,200,000 tonnes of oil
-- 252,000,000 tonnes of TNT
-- 13.3 tonnes of uranium-235
It’s a lot of energy – and if you look at the diagram, you’ll see most of it is actually wasted.
It’s estimated that 59.1 quads (60.6% of all energy) is “rejected energy”, a fancy term for energy that is produced but not used in an effective way. For example, when gasoline is burned in a car, most of the energy comes off as heat instead of doing productive work (ie. turning the crank shaft). The average internal combustion engine is only 20% efficient, and people get excited even when they approach 40% efficiency.
While gas engines are horribly inefficient, so are other energy sources. If you look at electricity production on the diagram, you’ll see that 67% of all energy going to generate electricity is wasted.
It’s the laws of physics, but there are still many areas for improvement to increase this efficiency.
A LONG WAY TO GO FOR GREEN ENERGY
As we explained in Part 2 of our Battery Series, there are still some big obstacles to overcome for green energy, batteries, and energy storage.
By looking at all energy use (including non-electrical energy used in automobiles, industrial, etc.), this diagram helps put things in even more perspective. To make a big impact, green energy not only has to make inroads in electrical generation, but it also has to supplant the 25.4 quads of energy being used in the automotive sector. This is why projects like the massive Tesla Gigafactory 1 are such a big deal. If Elon Musk is successful in his mission, the whole diagram and our energy mix would change dramatically.
For now, however, green is still a blip on the radar. Looking at total energy consumption in 2015, solar only accounted for 0.53 quads of energy. Meanwhile, wind accounted for 1.82 quads.