Energy density vs cost. The real drivers of humanity's transition to new energy sources.

Energy density is used as a metric to claim nuclear energy the next step, but really cost has driven energy advancements, and this is why renewables will win.

One of the most recent talking points in the current uranium stock hype cycle is that humanity has always transitioned from less to more energy dense sources. The trope goes that because humans have gone from lower energy density wood, to higher energy density coal, to higher energy density fossil fuels, that the logical next step is a jump to uranium / nuclear power.

And in terms of energy density of the fuel source, if that was the defining metric of what has caused energy transitions in the past, uranium absolutely does win out. For example, assuming a single 1” uranium pellet was fully converted to energy (they do not, in actuality, but this is a story for another day) it would give 17,000,000 BTU, which is equal to 1 ton of coal, 120 gallons of oil, or 17,000 cubic feet of natural gas.

Lets look at an energy transition in the past. In the mid 16th century, England began to run out of firewood, which was the dominant energy source of the time. Not only was wood the primary source of energy driving the British economy at the time, shifting requirements of agriculture, industry and commerce all strained wood supplies.

In particular, change was motivated by the migration of people from the countryside, to the cities. London, for example went from a population of ~60,000 in 1534, to a population of ~530,000 in 1696. Among the general English population, in 1534 only 1 in 10 was a ‘townsman’, and by 1690s 1 in 4 was. This strained wood supplies close by population centers, and from 1558 to 1625 the price of wood rose more than any other commodity, leading to widespread inflation (and complaints of deforestation).

Coal, up to this point never found widespread use in England. It had been burned in small quantities sourced from outcroppings since the 12th century, and a bit broader in China and Roman Britain. However it was not widely adopted before forests became depleted as a result of the perception that mining was a robbery from the earth, at the level of a kind of rape, and this perception did not change until the 16th century. Then, the wood shortage and its associated costs, as well as incentive from the government to use coal and preserve wood for naval uses, as a shortage of timber for shipbuilding would threaten royal Britain’s existence, led to the growth of coal use.

Source: Scientific American, 1977

The switch to coal did not come easily. Many industrial processes based around it had to be retooled to deal with the dirtier fuel. Processes which worked when fired by wood had to be re-engineered to avoid contact with burning coal and coal gasses. Wrought iron, for example, took until 1709 for a process making acceptable quality to be established. However, the plentiful nature of coal meant that after this initial pain period, processes often ended up cheaper than before, and fuel-heavy industries flourished such as iron wares, salt (evaporation of sea water, vs previous imports), gunpowder, brewing, and lime fertilizer. The application led to a coal boom and the discovery of massive coal resources in Britain, and for the next several hundred years, coal remained cheaper than wood based on availability.

However in all cases, no process was made simpler. While wood fuel allowed metallurgy to be conducted directly in contact with charcoal and wood gasses, coal and coal gasses mandated isolation from these, and the development of crucibles and fluxes to isolate metals resulted. It was the cost of coal, resulting from widespread scarcity of wood, and new discoveries of widespread coal resources in Britain, that led to its adoption over wood. ‘Energy density’ had nothing to do with it. Availability, as reflected by cost, did.

Enter the US story, where initial British colonists had no need for a domestic coal industry. Wood was abundant as a primary energy source, and while Britain was already burning coal for heat due to the centuries-earlier wood scarcity issues, wood costs were low in the US due to availability. There was no need for coal in 17th and 18th century America, early metallurgy was charcoal based (again, if one considers that chronologically Britain was using coal at this point) and it was only at the civil war in the US where coke, made from coal, began to replace charcoal (wood based) in iron blast furnaces when wood prices began to rise.

So look at this closely. Despite coal technology being developed in Britain ~200 years prior for iron production, despite early Americans having access to this technology, the US continued to use charcoal based blast furnaces due to availability /cost of wood.

If energy density was the inherent cause of this transition, this pattern would not be seen.

Instead, despite colonists from a coal based economy, arriving with all their coal based technology, to an area rich in wood, they went back to the wood based technology. Cost of inputs was the driver of the British transition, not energy density.

It is of course true that the energy density of coal is higher, and we do see, starting in the 1850s it declining as coal begins to take over.

What caused this? Again, an increase in prices of wood.

The East coast of the US was almost entirely forested upon the arrival of Europeans, and as mentioned above that meant an initial return to wood from processes already using coal in Britain. However the rapidly growing population of the US was causing deforestation already by the 1700s and 1800s. To quote Ben Franklin in 1744 as he noticed wood costs increasing in the Philadelphia area:

“Wood, our common Fewel,[fuel] which within these 100 Years might be had at every Man’s Door, must now be fetch’d near 100 Miles to some towns, and makes a very considerable Article in the Expence of Families,”

Similarly, Johann David Schoepf, a German doctor traveling through the US after the revolutionary war also was noticing extensive deforestation and feared that the next generation of Americans would not have enough wood to heat a teakettle

“leave for [American] grandchildren a bit of wood over which to hang the tea-kettle.”

It was with, again, the scarcity, as represented by cost, of wood that began to drive a transition to coal.

But it was not to be resisted and the shift did not come easy, and the arguments against the shift were numerous.

The designs of a coal stove vs an open hearth fireplace are vastly different, and coal stoves were considered to have an anti-American Aesthetic

Many people hated the aesthetics of stoves because they were enclosed, and you couldn’t see the flames within as you could in a traditional fireplace. In articles and speeches, prominent citizens protested, denouncing stoves as, essentially, un-American.

A few more historical quotes to put the coal transition in perspective:

Harriet Beecher Stowe, 1864.

Would our Revolutionary fathers have gone barefooted and bleeding over snows to defend air-tight stoves and cooking-ranges? I trow [believe] not.

Nathaniel Hawthorne, 1843

Social intercourse cannot long continue what it has been, now that we have subtracted from it so important...an element as firelight…While a man was true to the fireside, so long would he be true to country and law.

Coal was harder to light, and was soon blamed for a variety of health ailments and produced a large amount of soot, which in dense settlements was almost universally hated.

…

However, after watching an interview with a green chicken on YouTube, people were convinced that coal was the future because it was more energy dense than wood, so they ignored their health ailments, unamerican ugly stoves, air pollution and hassles, and switched to coal…

I’m sorry, I’m being snarky. If you recognize the above reference great. If not, don’t bother. And if you did not get alarm bells setting off in your head referencing YouTube existing in the 1800s please leave.

…

Anyway, back to actual history of the coal transition. The cultural resistance to coal was immense. It was estimated that the use of coal over wood led to an extra hour of work for a housewife, and a guide for servants in 1827 was 27 pages of how to light a coal stove.

However price won out, in 1831 it was estimated that the heating bill for a family in the cold months would be $4.50 using coal, and $21 using wood. 20 years later American households were burning more coal than wood in stoves, particularly in the cities where deforestation was more acute and natural wood resources (as in Ben Franklin’s Philadelphia example) were scarcer. Yet again, energy density had nothing to do with it, it was all cost.

Lets look at an example of where energy density DOES matter: when it influences cost :)

Deforestation and associated local high wood prices were particularly intense in two main areas, excellent agricultural centers where forests would be cut for farms, and population centers where forests were cut for human space and the associated population density strained wood supply. Both led to long transits for wood, reflected in higher costs.

The charcoal iron industry was still incredibly prevalent and widespread in the New Jersey highlands in the 1800s. Coal was now cheaper than wood in the majority of iron producing regions, and this region was a holdout to charcoal/wood as local conditions led to low-priced wood.

One can even check out the area on google maps today, it is still green and covered in dense forests. The reason is the area is particularly bad for agriculture. Geologically the area is defined by being the weathered remnants of a billion year old mountain range, and is rich in minerals including iron. The rocky soils and steep slopes make the area unsuitable for agriculture, so forests were not cut down for farms. Additionally, the forests are composed of deciduous hardwoods that grow rapidly, and several thousand acres of forest, replanted every 20-25 years, was expected to provide indefinite charcoal for an ironworks.

This suppressed the local price of wood, and as such charcoal. The area had rich iron ore deposits, so it led to a local charcoal-based iron industry, long after other locations had switched to coal. The way that energy density did come into play here, is that charcoal is of such low energy density that transporting it to a far away ironworks is infeasible.

So 3 factors prevented coal from taking over from wood in the production of iron here:

1. inhospitability to farming, preventing rising wood costs by cutting forests

2. Local inexhaustibly of wood, preventing wood from increasing in price

3. local availability of iron ore, negating the need to transport wood/charcoal.

This local economic situation led to charcoal based ironmaking persisting for decades after the rest of the country abandoned it, due to higher wood prices elsewhere.

So how is this relevant to today?

First, wood-based energy still persists in a few locations where either a natural market (waste wood chips) or a distorted market (countries with subsidies for wood because its "allegedly carbon neutral) exists. In these situations, such as industrial waste wood, wood can be so cheap that it is an economical method of power generation or industrial heat still. Its price still leads to its use today, regardless of energy density.

Now for renewable energy, in particular utility scale photovoltaics and onshore wind:

Here are the unsubsidized generation costs of various electricity sources:

Source: Lazard via wiki

What has this meant:

Can’t fight economics. Unless something has a chance of competing economically against wind and solar it won’t be built in appreciable amounts. Claims that because uranium is more energy dense that it is the next step do not hold up to scrutiny if uranium based power can’t compete economically, and so far, it has not.

Other historical and present energy transitions will be covered in subsequent posts, where we look at the drivers of each.

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