Book Summary: “Energy Transitions” by Vaclav Smil

Energy Transitions: History, Requirements, Prospects

Title: Energy Transitions: History, Requirements, Prospects
Author: Vaclav Smil
Scope: 4 stars
Readability: 3 stars
My personal rating: 5 stars
See more on my book rating system.

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Topic of Book

Smil examines the history of nations at they transfer from one type of energy to another. In particular, he attempts to estimate the time periods that would be necessary for modern economies to transition from fossil fuels to renewables.

If you would like to learn more about the role of energy in human history, read my book From Poverty to Progress: How Humans Invented Progress, and How We Can Keep It Going.

Key Take-aways

  • Energy transitions take decades to complete.
  • Energy transitions are not a simple change in technology. They requires a specific sequence of scientific advances, technical innovations, organizational actions and political changes.
  • Old energy sources rarely decline dramatically in use. New energy sources are generally added onto old energy sources.
  • Some of the important energy transitions of the past have been from wood to coal, and from coal to natural gas and petroleum.
  • Britain was unusual in using large amounts of coal as early as the 17th Century. Its main use was for heating homes.
  • Coal was the dominant energy source of the Industrial Revolution. It dominated until well after World War II.
  • The industrialization of China since 1980 has dramatically increased the burning of coal, more than North America and Europe combined.
  • Based upon previous energy transitions, fossil fuels will have widespread use for many decades in the future.
  • Increasing renewable energy production as a percentage of overall energy usage will become increasingly difficult.
  • Despite all the public investments in renewable energy, it makes up the same percentage of energy production as it did during the 1970s.

Other books by the same author:

Important Quotes from Book

The term energy transition is used most often to describe the change in the composition (structure) of primary energy supply, the gradual shift from a specific pattern of energy provision to a new state of an energy system.

But the study of energy transitions should be also concerned with gradual diffusions of new inanimate prime movers, devices that had replaced animal and human muscles by converting primary energies into mechanical power.

There is only one thing that all large-scale energy transitions have in common: Because of the requisite technical and infrastructural imperatives and because of numerous (and often entirely unforeseen) social and economic implications (limits, feedbacks, adjustments), energy transitions taking place in large economies and on the global scale are inherently protracted affairs. Usually they take decades to accomplish, and the greater the degree of reliance on a particular energy source or a prime mover, the more widespread the prevailing uses and conversions, the longer their substitutions will take.

As in the past, the coming energy transitions will unfold across decades, not years.

Photosynthesis uses only a small part of available wavelengths (principally blue and red light amounting to less than half of the energy in the incoming spectrum) and its overall conversion efficiency is no more than 0.3% when measured on the planetary scale and only about 1.5% for the most productive terrestrial (forest) ecosystems. Phytomass produced by photosynthesis is dominated by carbohydrates and absolutely dry phytomass has a fairly uniform energy density of about 18 MJ/kg;

Prime movers are energy converters able to produce kinetic (mechanical) energy in forms suitable for human uses. Human muscles (somatic energy) were the only prime movers (converting chemical energy in food to kinetic energy of walking, running, and countless manual tasks) until the domestication of animals provided more powerful animate prime movers used in fieldwork, transportation, and for some industrial tasks. Animate prime movers continued to dominate energy use long after the introduction of first mechanical prime movers, beginning with simple sails, followed, millennia later, by small water wheels, and roughly another millennium afterwards by small windmills.

All energy conversions involve some loss of the capacity to perform useful work. This is the essence of the second law of thermodynamics: in any closed system… The quest for higher conversion efficiencies underlies the evolution of modern energy systems.

Combustion, that is, rapid oxidation of carbon and hydrogen in biomass and fossil fuels, has been the dominant energy conversion since the early stages of human evolution. For hundreds of thousands of years of hominin evolution it was limited to wood burning in open fires… What has changed, particularly rapidly during the past 150 years, are the typical efficiencies of the process. In open fires less than 5% of wood’s energy ended up as useful heat that cooked the food; simple household stoves with proper chimneys (a surprisingly late innovation) raised the performance to 15–20%, while today’s most efficient household furnaces used for space heating convert 94–97% of energy in natural gas to heat.

The average U.S. wood and charcoal consumption was very high: about 100 GJ/capita in 1860, compared to about 350 GJ/capita for all fossil and biomass fuel at the beginning of the twenty-first century. But as the typical 1860 combustion efficiencies were only around 10%, the useful energy reached only about 10 GJ/capita. Weighted efficiency of modern household, industrial, and transportation conversions is about 40% and hence the useful energy serving an average American is now roughly 150 GJ/year, nearly 15-fold higher than during the height of the biomass era.

A careful investigation of energy transitions always reveals that their progress requires a specific sequence of scientific advances, technical innovations, organizational actions, and economic and political and strategic circumstances. Missing a single component in such a sequence, or delaying its introduction or effects because of some unforeseen events, results in very different outcomes and in lengthier transition periods.

The most obvious reality that emerges from the study of energy transitions done from the global perspective and across the entire historical time span is a highly skewed division of their progress: Stasis, stagnation, marginal adjustments, and slowly proceeding innovations marked the entire preindustrial era—while the process of industrialization and the evolution of postindustrial societies have been marked (indeed formed) by rapid, often truly precipitous diffusion of new inventions and widespread adoption of technical and organizational innovations.

The two fundamental transitions, from biomass to fossil fuels and from animate to inanimate prime movers, have taken place only during the last few centuries (roughly three in the case of some European societies) or just a few recent decades (six in China’s, four in India’s case), and the emergence of electricity as the energy form of the highest quality began only during the 1880s. Inevitably, these transitions began on small local scales, evolved into nationwide developments, and eventually became truly global phenomena.

All preindustrial societies had a rather simple and persistent pattern of primary fuel use as they derived all of their limited heat requirements from burning biomass fuels. Fuelwood (firewood) was the dominant source of primary energy, but woody phytomass would be a better term: the earliest users did not have any requisite saws and axes to cut and split tree trunks, and those tools remained beyond the reach of the poorest peasants even during the early modern era. Any woody phytomass was used, including branches fallen to the ground or broken off small trees, twigs, and small shrubs. In large parts of the sub-Saharan Africa and in many regions of Asia and Latin America this woody phytomass, collected mostly by women and children, continues to be the only accessible and affordable form of fuel for cooking and water and house heating for the poorest rural families.

For hundreds of millions of people the grand energy transition traced in this chapter is yet to unfold: They continue to live in the wooden era, perpetuating the fuel usage that began in prehistory.

But, without exception, all of the world’s major economies—the United States, the United Kingdom, Germany, France, Russia, Japan, China, and India—had followed the classical sequence from biofuels to Coal.

Three grand trends marked the global coal production of the twentieth century: continuous decline of its relative importance, continuous growth of its absolute contribution to the worldwide total of primary energies, and the transformation from a highly labor-intensive to a highly mechanized industry.

Electricity’s use results in economic benefits unsurpassed by any fuel, as it offers superior final conversion efficiencies, unmatched productivity, and unequaled flexibility, with uses ranging from lighting to space heating, from metallurgical to food industries, and from any stationary to all but one mobile use (commercial flight). Its other much-appreciated advantages include precise control of delivery (ranging from less than one watt for the most efficient microchips to multigigawatt flows in large national or regional grids), focused applications on any conceivable scale (from micromachining to powering the world’s largest excavators and the world’s fastest trains), and, of course, no need for storage and the ease of using (flipping the switch) energy that is noiseless and, at the point conversion, absolutely clean.

There are at least four major reasons why thermal electricity generation took off so swiftly and has continued to expand so vigorously. The first one is an undoubtedly brilliant Edisonian design of an entirely new energy system for generating, transmitting, and converting electricity… The second reason is that while more than 125 years after its invention Edison’s grand concept of electricity system remains the foundation of the modern thermal electric industry, every one of its key components has been improved by a remarkable concatenation of technical advances that have made every aspect of the electric system more efficient, more reliable, and more durable.

The third reason was the invention and rapid commercialization of a device that did not exist when Edison designed his first electricity-generating stations: In 1888 Nikola Tesla patented his electric induction motor, a device that made it possible to convert electricity into mechanical energy with high efficiency and with precise control. Within a few decades after their introduction electric motors became the dominant prime movers in all industries and they had also revolutionized household work.

The fourth factor was the ability to harness the economies of scale by generating electricity in stations of increasingly greater capacity and by transmitting it by interconnected HV lines.

Human muscles were the sole prime mover during the hominin evolution as well as in all preagricultural societies organized to provide subsistence through foraging (gathering and hunting). Human exertions are limited by metabolic rates and by mechanical properties of human bodies, and before the domestication of draft animals the only way to enlarge their overall scope was to rely on combined action of people pushing or pulling heavy loads, sometimes with ingenious assistance by rolling logs or sleds.

With the domestication of draft animals humans acquired more powerful prime movers, but because of the limits imposed by their body sizes and commonly inadequate feeding the working bovines, equids, and camelids were used to perform only mostly the most demanding tasks (plowing, harrowing, pulling heavy cart- or wagon-loads or pulling out stumps, lifting water from deep wells) and most of the labor in traditional societies still needed human exertion.

Comparison of plowing productivities conveys the relative power of animate prime movers. Even in the light soil it would take a steadily working peasant about 100 hours of hoeing to prepare a hectare of land for planting; in heavier soils it could be easily 150 hours. In contrast, a plowman guiding a medium-sized ox harnessed inefficiently by a simple wooden yoke and pulling a primitive wooden plow would do that work in less than 40 hours; a pair of good horses with collar harness and a steel plough would manage in just three hours.

When expressed in terms of daily mass-distance (t-km), a man pushing a wheelbarrow rated just around 0.5 t-km (less than 50-kg load transported 10–15 km), a pair of small oxen could reach 4–5 t-km (10 times the load at a similarly slow speed), and a pair of well-fed and well-harnessed nineteenth-century horses on a hard-top road could surpass 25 t-km.

Steam engines remained the dominant mechanical prime mover during the entire nineteenth century and by 1900 their record ratings were unit power of 3 MW (compared to 100 kW in 1800), pressure of 1.4 MPa (100-fold increase above the 1800 level), and efficiency of just above 20%, an order of magnitude better than at the beginning of the nineteenth century. But the machines had their inherent disadvantages, above all the enormous size and mass of all high-capacity units due to high mass/power ratios and relatively poor conversion efficiency. The first drawback made them unsuitable for road transport, eliminated them from any serious consideration in powered flight, and also made it impractical to build larger units (in excess of 5 MW) required for the increasing capacities of thermal electricity generation.

Electrification of industrial manufacturing was completed first in the United States (during the 1930s), then in Europe (by the 1950s), and many low-income countries went straight from the ancient use of animate prime movers to reliance on electric motors.

The first conclusion of this global quantification is that the relative importance of biofuels had not changed dramatically during the first half of the nineteenth century (it was still nearly 95% of the fuel total by 1840) but it began its accelerated decline after 1850: By 1860 the share of biomass fuels fell below 85%, by 1880 it was just above 70%, by 1890 it was less than two thirds, and although we will never be able to pinpoint the date, it is most likely that sometime during the latter half of the 1890s fossil fuels (i.e., overwhelmingly, coal) began to supply more than half of all energy derived from the combustion of fuels.

Contrary to a commonly held impression that the nineteenth century was the era of coal, on the global scale and in its entirety, that century still belonged very much to the wooden era.

See page 64 for primary energy transitions from 1800-2010

Between 1800 and 1900 cumulative combustion of biofuels added to roughly 2.4 YJ compared to less than 0.5 YJ of fossil fuels, which means that biomass provided no less than 85% of all of the century’s fuel energy.

Coal ended up indisputably as the century’s most important fuel.

Coal was in a big lead during the first half of the twentieth century (its energy content accounted for half of all fuels and 80% of all fossil fuels), crude oil in its second half (35% of all fuels, more than 40% of fossil fuels).

Large marine diesels needed about 40 years to move from pioneering designs to a near-complete dominance of that important transport niche. Similarly, where the transition on railroads was solely, or largely, from steam to diesel engines, its duration was 35–45 years from the first models to near complete dominance. The fastest substitution of draft animals by tractors took place in the United States, with 30 years from the first introduction (in the early 1890s) to more than 50% of total power (in the early 1920s), but another 30 years

were needed to bring that share above 90%. In Western Europe the spans from introduction of tractors to their near-complete dominance were about 60 years and the transition has yet to be accomplished in many Asian and African countries.


English coal—known and used sporadically in small manufactures for centuries—became an increasingly important heating fuel already during the first half of the sixteenth century, above all (due to its falling prices) among poorer households.

Coal surpassed biomass as the source of heat most likely around 1620, perhaps a bit earlier. By the middle of the seventeenth century British coal supplied two thirds of all thermal energy, by 1700 about 75%, by 1800 about 90%, and by 1850 its share was in excess of 98%. This coal supremacy lasted for another 100 years: By 1950 coal’s share was still 91% and by 1960 it declined to 77%, the rate it had reached already during the first decade of the eighteenth century. This means that coal dominated the country’s thermal energy use (supplying more than 75% and as much as 99% of the total) for 250 years, a period of dependence unmatched by any other nation.

British coal production reached its peak in 1913 (with 287 Mt).


During the early Napoleonic times more than 90% of France’s primary energy came from wood, that that share declined to about 75% by 1850, and that it slipped below 50% by 1875. By 1880 coal provided about 55% of all primary energy and it then dominated France’s primary energy supply until the late 1950s when it yielded to imported crude oil whose share rose to as much as 68% by 1973.


The Dutch Republic, and particularly the province of Holland, was one of the great pioneers of adopting fossil fuels and inanimate sources of energy, and it had done so in two rather uncommon ways, by large-scale production of peat and by an extraordinarily high reliance on wind power.

Peat, the youngest fossil fuel, was the principal source of industrial and domestic heat, and, fortuitously, every one of Holland’s major cities had nearby resources that could be easily extracted and inexpensively transported. Peat’s annual consumption during the seventeenth century averaged about 1.5 Mt (equivalent of about 25 PJ or nearly 800 MW) but coal and firewood were also imported and Holland’s windy climate and flat landscape provided excellent conditions for harnessing wind by sails and mills.

After the best peat deposits were depleted and shipping became more expensive due to extensive silting of shallow waterways and harbors, Holland ceased to be an exception and its energy use began to resemble that of the neighboring countries.


My estimates indicate that in 1850 nearly half of U.S. useful power was provided by animals, roughly a sixth by people, and just over a third by inanimate prime movers, overwhelmingly by steam engines complemented by water wheels, water turbines, and windmills.


China’s primary energy use shows the share of biomass energies fairly constant during the first half of the twentieth century, falling only marginally from more than 99% in 1900 to nearly 98% by 1949.

China’s extraordinary dependence on coal means that the country now accounts for more than 40% of the world extraction, and that the mass it produces annually is larger than the aggregate output of the United States, India, Australia, Russia, Indonesia, and Germany, the world’s second- to seventh-largest coal producers. No other major economy, in fact no other country, is as dependent on coal as China.


My best estimates indicate that by 1913 wood supplied no less than 75% of Russia’s primary energy and that the aggregate consumption of fossil fuels and primary electricity surpassed that of fuelwood only during the early 1930s (compared to the U.S. tipping point half a century earlier in 1884/1885).

British, French, and U.S. histories of energy use show that all early modernizers had experienced a slow (even very slow) transition from biomass fuels to coal… During that time gaps between invention, innovation, and large-scale commercial diffusion were often so long because of the limited abilities to perfect newly invented production methods and prime movers and because of the restricted or disrupted capacities for their widespread adoption. Several reasons for those slow advances stand out: Scientific understanding of the underlying processes was often inadequate, suitable high performance materials needed for mass production (steel in particular) were either unavailable or in short supply, manufacturing processes were inadequate as far as both qualities and capacities were concerned, requisite infrastructures took a long time to complete, and large-scale competitive markets were absent.

  1. “Energy and Civilization: A History” by Vaclav Smil
  2. “A Question of Power: Electricity and the Wealth of Nations” by Robert Bryce
  3. “The Prize: The Epic Quest for Oil…” by Daniel Yergin
  4. “Prime Movers of Globalization: The History of Diesel Engines and Gas Turbines” by Vaclav Smil
  5. “Foragers, Farmers and Fossil Fuels” by Ian Morris
  6. “Power to the People: Energy in Europe over the Last Five Centuries” by Kander et al

If you would like to learn more about the role of energy in human history, read my book From Poverty to Progress: How Humans Invented Progress, and How We Can Keep It Going.

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