Here you’ll learn how to be smart about energy and fuels, such that what makes it to stories, articles, media pieces and blog posts can be assessed.   It’s coming up on four years since those early posts on the fundamentals here were written and they’ve slowly gone away into the mists of search engine relevance.  Actually the refresher idea sources from the redoubtable Al Fin who spotted a remarkable web page on Transwiki that has, quite handily, listed many energy and fuel sources.  The Transwiki page even has a commentary with entertaining thoughts to amuse you.

Energy Density from Transwiki Condensed Size. Click the text link above to see the entire chart at Tranwiki.

At the basic level consumers use tools to get something done, which comes with an energy or fuel price.  The tool investment and the costs to feed it energy are the basic expenses.  The investment should amortize over time or total time used, the energy a cost per job or time working.  Not real hard stuff. But. . .

Energy sources be they a fuel or an energy store like a battery, have values, which is where the calculation for the smart gets going.  Cheaper energy is good for consumers, the economy and increases living standards.  If the world’s governments are smart they will drive towards cheaper tools and energy supplies simply because the economic pie is bigger and the profits produce more taxes and payrolls to tax.  Driving to more efficiency and lower energy costs would seem obvious, wouldn’t it?

The earthquake, tsunami and the disaster planetary geology foisted upon Japan makes this all the more clear – if you can avoid the mass media’s pollution about the wrecked nuclear reactors.

Thus what source of energy is the cheapest?  The answer is obvious from the Transwiki page – uranium.  Its simply the physics, uranium’s gravimetric (essentially by weight) of energy density is 2.5×1010 Watt hours per kilogram.  This is a huge amount of energy in a very small package.  Billions of dollars invested making electricity with a few million of uranium in atomic fusion could be very cheap, if the regulations, education and public discourse made any sense.  As it sits in the U.S. with a blundering regulatory system and wildly inflated costs, uranium is still the lowest cost, most reliable and safest form of power generation.

Of course thorium might be even cheaper and safer if the choices were to be investigated and improved to commercial scale. Interestingly, thorium isn’t on the Transwiki page, one might assume that’s because of the two main reactor types, conventional like a current day uranium reactor or fluoride reactor are so very different.  Still, what is known shows that thorium, likely in a fluoride reactor should be even cheaper than uranium.

The next Transwiki material is Boron.  Boron is known to fuse rather than split as in uranium or thorium.  As something of a surprise, boron is listed.  From Eric Lerner’s Focus Fusion to the Richard Nebel led Bussard EMC2, boron could have a future, and it will likely be even cheaper in spite of a huge energy density disadvantage at 16,361 Wh/kg.  No exponential power here – the difference between the nuclear field of fission and fusion by weight, if the number is right, is quite substantial. This is because fission needs very heavy elements and fusion quite light ones. The reported numbers are surely subject to revision when some valid evidence becomes available.

Next up, its fossil fuels.  That might or might not be a surprise, but the energy store in carbon-based hydrogen enriched fossilized fuels is substantial.  The Transwiki page ranks by volume, but by mass or weight of the common fuels diesel is tops followed by jet JP10 gasoline, coal, natural gas liquefied, and propane.  The range runs from a diesel high of 13,762 to coal at 6667 Wh/kg.  With gasoline at 12,200 Wh/kg is easy to see why the world runs on petroleum and coal.  Getting to this level is hard, as we’ll see . . .

Next is the common alcohols, ethanol at 7,850 and methanol at 6,400 Wh/kg.  Ammonia clocks in at 4,318 Wh/kg.  This makes ethanol look pretty good and ammonia look not so hot.  But we’re all carrying forward our experience using gasoline and diesel internal combustion.  The alcohols, including butanol, which isn’t listed, have properties that can produce more work per unit when the engine is built to optimize the fuels.

The Transwiki page even lists wood from 3154 more or less down to 1554 Wh/kg.  The energy by volume for wood is instructive. It’s only about 700 down to about 200 Watt-hours per liter.  Now compare that to diesel at more than four times the energy by weight and more than 15 times by volume.

Properties matter.  An over the road truck or railroad engine’s needs for fuel using wood would dwarf the load they’re carrying.  Or the loads would have to shrink proportionately, or reduce the speed in a major way.  We’re not going to fly using wood for fuel.

Finally hydrogen or H2. In liquid form H2 is very dense by weight at 39,000 Wh/kg, but by volume liquid hydrogen is only 2600 Wh/l.  The properties of hydrogen are not easy to keep pure – many of the fuels noted above have more liquid hydrogen by volume than liquid hydrogen does alone.  Then there is the matter of getting H2 to the liquid state at near absolute zero and keeping it there.  Its not simple cheap easy or safe.

Presuming one is clever enough to consider hydrogen connected to either carbon or in ammonia the ranges seen in the Transwiki page are illuminating.  What we’re used to is very dense fuel stores in small volumes.

The most popular fuels, diesel and gasoline come in at about 10,000 Wh/l and 13,000 Wh/kg.  They’re popular because they are so dense and small in volume.  How will a battery stack up?

Not real well.  The best theory battery listed is Sodium Borohydride at 7,100 Wh/kg.  Not realistic and not on any research hot lists.  It’s a very long drop to the best lithium based battery at 439 Wh/kg.  The more possible theoretical batteries get to 1,000 Wh/l as seen in zinc air or 1200 Wh/kg seen in ion polymer lithium depending, but both of these are far short of the 13,000 Wh/kg of popular petroleum fuels.

That’s the inescapable metric, 10,000 Wh/l or 13,000 Wh/kg.  Where does the latest great idea fit in comparison to that?

On the other hand . . .

The designs and engineering of the tools used matters.  A simple gasoline powered vehicle might be 20% efficient.  A stationary generator powered unit might get to 40% with losses to the battery at 20% or less and an electric traction motor at 10%.  That still increases the distance per fuel unit by more than 50% or third less fuel cost assuming the fuel is the same.  A fuel cell might be 90% efficient, the battery losing 20% and the traction motor losing 10% netting 65% efficiency, more than 3.25 times the distance per fuel unit compared to a gasoline engine vehicle.

You are going to decide what market succeeds.  At least within the parameters of what government regulations allow to be sold.  Of course the whole of the industrial world is feverishly working to drive to better means at lower costs.  Obviously niche markets will permit more innovative products, at smaller market sizes and thus higher unit costs.  But somewhere along the way the power systems whether engines, fuel cells or something else will break through to the mass market.  Its reasonable to expect that there will be a liquid fuel market for decades to come.

Meanwhile keep an eye on those energy density numbers when watching the process of the next phase of the world’s energy system develop.  The counter point is the system efficiency, something not seen nearly often enough, and when it is its usually seriously biased, but that’s another post.


1 Comment so far

  1. Charles on May 4, 2014 7:52 PM

    Friends, There IS only one fuel. It results from the most basic chemical reaction on this planet going back billions of years and all of use possess the reactants.
    If you own a home with a yard you can make the fuel.
    Methane, natural gas. The ONLY substance which fuel a vehicle cleanly which DOES NOT require a refinery a power generating station or a battery manufacturing plant. AND the engine runs clean with no need to change lubricating oil.
    Thousands of farms run their operations on electricity generated locally from a waste-to-methane pond.
    You may purchase it from someone;. When that natgas runs out then just make it yourself. A digester the size of a buried sewage cistern can generate enough natgas to power a car on a daily basis.
    Forget all the other exotic, expensive stuff.

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