﻿ How Far Will Energy Go? – An Energy Density Comparison

# How Far Will Energy Go? – An Energy Density Comparison

12 Oct, 2009

I once read an article by William Tucker that included some interesting facts about nuclear energy.  You can read it here.  One statistic from Tucker’s letter that I’ve kept with me is that uranium is 2 million times more energy dense than coal.  Hopefully, by representing this fact visually it will stick with most of you.  Let’s get started…

Energy density is the amount of energy stored in a given volume or mass of a certain substance or material.  If an energy source has a high energy density, then you’ll need less material or resources to create the same, if not more, amounts of power than energy sources with lower energy densities.  I’ve tabulated the energy density of various energy sources below.  These numbers are easily accessible on the internet from various reliable sources.  I started with a wonderfully informative website named “What Is Nuclear?” linked here.

 Material Energy Density (MJ/1kg) Solar* 0.2-1 Wood 10 Ethanol 26.8 Coal 32.5 Crude Oil 41.9 Diesel 45.8 Natural Gas 55.6 Natural Uranium 570000 Reactor-grade Uranium 3700000

*Tucker explains in his piece that solar energy is 10-50 times less dense than wood.  I’d like to use this, but I had a hard time justifying that you can consider solar energy in terms of mass (kg) when solar energy density is usually measured per square meter.  I included solar in the table as a matter of perspective.

I will be the first to admit that if you don’t have a scientific background, you cannot fully appreciate this data unless it is put into perspective.  So, how can you put these numbers into perspective?  I will first represent this data with graphs.  Then I will represent these numbers in terms of feet, and then in miles.

## Represented Graphically

First, the energy densities of wood and ethanol, both directly derived from plants, are shown in the below graph.

Next, the energy densities for wood, ethanol, coal, crude oil, diesel, and natural gas are graphically displayed.

Next, natural uranium and reactor-grade uranium are included in the graph.  They completely dwarf the other energy sources.

You can see that other than natural and reactor-grade uranium the other energy sources don’t even show up on the graph.  This is because nuclear energy is just that energy dense!  In fact, if I were to stretch this graph out to where natural gas, coal, and oil would begin to show up, this graph would be almost one mile long!

## Represented in Feet

### Wood – 10 ft

This can be compared the height of a basketball goal, or the career average passing yards per attempt of Ryan Leaf (3.6 yards).  Leaf is often referred to as the worst quarterback in NFL history.

Ryan Leaf

### Coal – 33 ft

This can be compared the career average passing yards per completion of Brett Favre (11.4 yards).

### Crude Oil – 42 ft

Compare this to the distance that a football punter stands behind the line of scrimmage before the ball is snapped to him for a punt.  Virginia Tech’s football program has proven that 42 feet (14 yards) isn’t very far.  They have led all NCAA football teams in blocked kicks over the past two decades.  It takes about 3 seconds from the snap to the blocked punt.

Virginia Tech blocks a punt against Miami

### Natural Uranium – 570,000 ft (108 mi)

This is approximately the distance from Washington DC to Richmond, VA on I-95.  It takes 2 hours to get there with no traffic.

DC to Richmond

### Reactor-grade Uranium – 3,700,000 ft (700 mi)

This is the approximate distance from Washington, DC to Chicago, IL via interstate travel.  This trip takes 11 hours without traffic or bathroom breaks; and although some may argue otherwise, I would be willing to bet that Brett Favre cannot throw a ball this far.

DC to Chicago

## Represented in Miles

### Coal – 33 miles

This is equal to the average round-trip daily commuting distance for Americans (ABC News/Time Magazine/Washington Post Poll).

Commute

### Natural Uranium – 570,000 miles

This is equal to traveling around the equator 23 times.  Or making one trip to the Moon and back.  Hardly a daily commute.

### Reactor-grade Uranium – 3,700,000 miles

This is equal to traveling around the equator 149 times.  Or you could make 15.5 round-trips to the moon, but you would have to stay there because you’re one-half a round-trip short.

One Leg Short of a Round-trip

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1. The Log
October 13, 2009

Wow, reactor grade Uranium is almost as energy dense as a Chuck Norris roundhouse kick.

2. DocForesight
October 13, 2009

Bravo gentlemen!

3. Krzysztof Kosiński
December 13, 2009

You should also add the energy density of thorium and uranium when used in breeder reactors. However, this would get even more unwieldy, as those columns would be several times higher than reactor grade uranium.

4. March 17, 2010

Great post, I bet a lot of work and research went into this article.

5. March 28, 2014

A liquid fueled reactor uses virtually all of the energy of uranium, or thorium so you can go 81,000,000 miles. So on close approach (36 Mmiles) you could go to Mars an back and a couple dozen trips to the moon, but at its most distant (62 Mmiles) you’d get there and 1/3 of the way back.

6. March 28, 2014

The reason this liquid fuel vs solid fuel doesn’t help you get to Mars much more cheaply is that the amount of fuel you burn is a tiny fraction of the mass needed to keep the rector critical.