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Category — Smil, Vaclav

‘The Limits of Energy Innovation’: Timeless Insight from Vaclav Smil

[Editor note: One of the great energy scholars of our time is Vaclav Smil, Distinguished Professor Emeritus of Environment and Geography at the University of Manitoba. This (modified) article remains as fresh today as it was when originally published in 2009.]

President Barack Obama has promised an energy revolution in the world’s largest economy, with renewable sources of power and “green” technologies breaking America’s – and ultimately the world’s – dependence on conventional fuels…. But how realistic is this vision?

Primary Energies: Unchanged

There is only one kind of primary energy (energy embodied in natural resources) that was not known to the first high civilizations of the Middle East and East Asia and by all of their pre-industrial successors: isotopes of the heavy elements whose nuclear fission has been used since the late 1950’s to generate heat that, in turn, produces steam for modern electricity turbo-generators. Every other energy resource has been known for millennia, and most of them were harnessed by pre-modern societies.

The fundamental difference between traditional and modern uses of energy consists not in access to new or better energy resources, but in the invention and mass deployment of efficient, affordable, reliable, and convenient “prime movers,” devices that convert primary energies into mechanical power, electricity, or heat. History could be profitably subdivided into eras defined by the prevailing prime movers. [Read more →]

November 22, 2013   No Comments

Power Density Primer: Understanding the Spatial Dimension of the Unfolding Transition to Renewable Electricity Generation (Part V – Comparing the Power Densities of Electricity Generation)

Editor’s note: This is the conclusion of the series that provides an essential basis for the understanding of energy transitions and use. The previous posts in this series can be seen at:

Part I – Definitions

Part II – Coal- and Wood-Fired Electricity Generation

Part III – Natural Gas-Fired Electricity Generation

Part IV – New Renewables Electricity Generation


America’s dominant mode of electricity generation is via combustion of bituminous and sub-bituminous coal in large thermal stations. All such plants have boilers and steam turbogenerators and electrostatic precipitators to capture fly ash, but they burn different qualities of coal that may come from surface as well as underground mines, have different arrangements for cooling (once-through using river water or various cooling towers) and many have flue gas desulfurization to reduce SO2 emissions. Consequently, these conversions of chemical energy in coal to electricity feature widely differing power densities: for the power plants alone they are commonly in excess of 2 kW/m2 and can be as high as 5 kW/m2. When all other requirements (coal mining, storage, environmental controls, settling ponds) are included, the densities inevitably decline and range over an order of magnitude: from as low as 100 W/m2 to as much as 1,000 W (1 kW)/m2.

In contrast, compact gas turbines plants (the smallest ones on trailers and larger facilities that can be rapidly assembled from prefabricated units), which can be connected to existing gas supply, can generate electricity with power density as high as 15 kW/m2. Larger stations (>100 MW) using the most efficient combined-cycle arrangements (with a gas turbine’s exhaust used to generate steam for an attached steam turbine) will operate with lower power densities, and if new natural gas extraction capacities have to be developed for their operation then the overall power density of gas and electricity production would decline to a range similar to that of coal-fired thermal generation or slightly higher, that is in most cases to a range of 200-2000 W/m2. [Read more →]

May 14, 2010   6 Comments

Power Density Primer: Understanding the Spatial Dimension of the Unfolding Transition to Renewable Electricity Generation (Part IV – New Renewables Electricity Generation)

Editor’s note: This is Part IV of a five part series that provides an essential basis for the understanding of energy transitions and use. The previous posts in this series can be seen at:
Part I – Definitions
Part II – Coal- and Wood-Fired Electricity Generation
Part III – Natural Gas-Fired Electricity Generation

 

Photovoltaic Electricity Generation

Satellite measurements put the solar constant – radiation that reaches area perpendicular to the incoming rays at the top of the atmosphere (and that is actually not constant but varies with season and has negligible daily fluctuations) – at 1,366 W/m2. If there were no atmosphere and if the Earth absorbed all incoming radiation then the average flux at the planet’s surface would be 341.5 W/m2 (a quarter of the solar constant’s value, a sphere having four times the area of a circle with the same radius: 4?r2/?r2). But the atmosphere absorbs about 20% of the incoming radiation and the Earth’s albedo (fraction of radiation reflected to space by clouds and surfaces) is 30% and hence only 50% of the total flux reaches the surface prorating to about 170 W/m2 received at the Earth’s surface, and ranging from less than 100 W/m2 in cloudy northern latitudes to more than 230 W/m2 in sunny desert locations.

For an approximate calculation of electricity that could be generated on large scale by photovoltaic conversion it would suffice to multiply that rate by the average efficiency of modular cells. While the best research cells have efficiencies surpassing 30% (for multijunction concentrators) and about 15% for crystalline silicon and thin films, actual field efficiencies of PV cells that have been recently deployed in the largest commercial parks are around 10%, with the ranges of 6-7% for amorphous silicon and less than 4% for thin films. A realistic assumption of 10% efficiency yields 17 W/m2 as the first estimate of average global PV generation power density, with densities reaching barely 10 W/m2 in cloudy Atlantic Europe and 20-25 W/m2 in subtropical deserts. [Read more →]

May 13, 2010   12 Comments

Power Density Primer: Understanding the Spatial Dimension of the Unfolding Transition to Renewable Electricity Generation (Part III – Natural Gas-Fired Electricity Generation)

Editor’s note: This is Part III of a five part series that provides an essential basis for the understanding of energy transitions and use. The previous posts in this series can be seen at:

Part I – Definitions

Part II – Coal- and Wood-Fired Electricity Generation

Boilers of electricity-generating stations burning coal can be converted to burn liquid or gaseous hydrocarbons (fuel oil, even crude oil, and natural gas) and such conversions were fairly common during the 1960s and the early 1970s. Burning natural gas rather than coal has clear environmental advantages (it generates less, or no, sulfur dioxide and no fly ash) but the overall conversion efficiency of the boiler-steam turbogenerator unit changes little. In contrast, gas turbines, particularly when coupled with steam turbines, offer the most efficient way of electricity generation. This results in much higher power densities than is the case with coal-fired plants. Overall densities of the fuel extraction and electricity generation process are also kept high because of the relatively high power densities of natural gas production (depending on the field they vary by more than an order of magnitude, with minima around 50 W/m2, maxima well over1 kW/m2) and even more by the fact that new gas-powered generation often does not need any major new infrastructure as it can tap the supply from existing fields and pipelines.

Gas turbines were first commercialized for electricity generation by Brown Boveri in Switzerland during the late 1930s but in the US their installations became common only during the late 1960s, spurred by the November 1965 US Northeast blackout that left 30 million people without electricity for up to13 hours. Nationwide capacity of gas turbines rose from just 240 MW in 1960 to nearly 45 GW by 1975, a nearly 200-fold rise in 15 years. This ascent was interrupted by high hydrocarbon prices (as well as by stagnating electricity demand) but it resumed during the late 1980s. By 1990 nearly half of the 15 GW of all new capacity ordered by the US utilities was in gas turbines and by 2008 almost exactly 40% of the US summer generating capacity (397.4 GW) was installed in gas-fired units, either single- or combined-cycle gas turbines (CCGT). Unlike a single gas turbine that discharges its hot gas, CCGT uses the turbine’s hot exhaust gases to generate steam for a steam turbine, boosting overall efficiency. While the best single gas turbines can convert about 42% of their fuel to electricity, CCGT convert as much as 60% and are now the most efficient electricity generators. [Read more →]

May 11, 2010   No Comments

Power Density Primer: Understanding the Spatial Dimension of the Unfolding Transition to Renewable Electricity Generation (Part II – Coal- and Wood-Fired Electricity Generation)

Editor’s note: This is Part II of a five part series that provides an essential basis for the understanding of energy transitions and use. The opening post on definitions was yesterday.

Baseline calculations for modern electricity generation reflect the most important mode of the U.S. electricity generation, coal combustion in modern large coal-fired stations, which produced nearly 45% of the total in 2009. As there is no such thing as a standard coal-fired station I will calculate two very realistic but substantially different densities resulting from disparities in coal quality, fuel delivery and power plant operation. The highest power density would be associated with a large (in this example I will assume installed generating capacity of 1 GWe) mine-mouth power plant (supplied by high-capacity conveyors or short-haul trucking directly from the mine and not requiring any coal-storage yard), burning sub-bituminous coal (energy density of 20 GJ/t, ash content less than 5%, sulfur content below 0.5%), sited in a proximity of a major river (able to use once-through cooling and hence without any large cooling towers) that would operate with a high capacity factor (80%) and with a high conversion efficiency (38%).

This station would generate annually about 7 TWh (or about 25 PJ) of electricity. With 38% conversion efficiency this generation will require about 66 PJ of coal.

1 GW x 0.8 = 800 MW
800 MW x 8,766 hours = 7.0 TWh
7.0 TWh x 3,600 = 25.2 PJ
25.2 PJ/0.38 = 66.3 PJ

Assuming that the plant’s sub-bituminous coal (energy density of 20 GJ/t, specific density of 1.4 t /m3) is produced by a large surface mine from a seam whose average thickness is 15 m and whose recovery rate is 95%, then under every square meter of the mine’s surface there are 20 t of recoverable coal containing 400 GJ of energy. In order to supply all the energy needed by a plant with 1 GWe of installed capacity, annual coal extraction would have to remove the fuel from an area of just over 16.6 ha (166,165 m2), and this would mean that coal extraction required for the plant’s electricity generation proceeds with power density of about 4.8 kW/m2:

15 m3 x 0.95 x 1.4 t = 19.95 t
19.95 t x 20 GJ/t = 399 GJ
66.3 PJ/399 GJ = 166,165 m2
800 MW/166,165 m2 = 4,814.5 W/m2
A much larger area has to be occupied by the plant itself, but in a mine-mouth power plant without coal storage yard, with once-through cooling and with the disposal of fly ash into the excavated area the station’s complete infrastructure (boiler and turbogenerator halls, electrostatic precipitators, maintenance buildings, offices, roads, parking) could cover as little as 600,000 m2. This means that the total area whose other uses would be preempted every year by coal extraction and the permanent infrastructure of a coal-fired power plant would be roughly 766,000 m2 and the power density of the entire extraction-generation enterprise would be about 1,000 W/m2:

800 MW/766,000 m2 = 1,044.4 W/m2

An even larger area would be needed by a plant located far away from a mine (supplied by a unit train or by barge), [Read more →]

May 10, 2010   2 Comments

Power Density Primer: Understanding the Spatial Dimension of the Unfolding Transition to Renewable Electricity Generation (Part I – Definitions)

[Editor’s note: This is Part I of a five-part series by Vaclav Smil that provides an essential basis for the understanding of energy transitions and use. Dr. Smil is widely considered to be one of the world's leading energy experts. His views deserve careful study and understanding as a basis for today's contentious energy policy debates. Good intentions or simply desired ends must square with energy reality, the basis of Smil's worldview.]

Energy transitions – be they the shifts from dominant resources to new modes of supply (from wood coal, from coal to hydrocarbons, from direct use of fuels to electricity), diffusion of new prime movers (from steam engines to steam turbines or to diesel engines), or new final energy converters (from incandescent to fluorescent lights) – are inherently protracted affairs that unfold across decades or generations.

Many factors combine to determine their technical difficulty, their cost and their environmental impacts. A great deal of attention has been recently paid to the pace of technical innovation needed for the shift from the world dominated by fossil fuel combustion to the one relying increasingly on renewable energy conversions, to the likely costs and investment needs of this transitions, and to its environmental benefits, particularly in terms of reduced CO2 emissions.

Inexplicably, much less attention has been given to a key component of this grand transition, to the spatial dimension of replacing the burning of fossil fuels by the combustion of biofuels and by direct generation of electricity using water, wind, and solar power. Perhaps the best way to understand the spatial consequences of the unfolding energy transition is to present a series of realistic power density calculations for different modes of electricity generation in order to make revealing comparisons of resources and conversion techniques. Detailed calculations will make it easy to replicate them or to change the assumptions and examine (within realistic constraints) many alternative outcomes. [Read more →]

May 8, 2010   5 Comments

Energy Innovation as a Process: Lessons from LNG

Modern technical innovations operate unlike the traditional, pre-industrial advances: they too have their phases of gradual improvements based on tinkering and everyday experiences with running a machine or a process. But the initial accomplishments result almost invariably from deliberate and systematic pursuits of theoretical understanding. Only once that knowledge is sufficiently mastered the process moves to its next stage of experimental design followed by eventual commercialization.

That is precisely how Charles Parsons, Rudolf Diesel, and their collaborators/successors invented and commercialized the two machines that work–unseen and unsung–as the two most important prime movers of modern economies:

steam turbo-generators, which still generate most of the world’s electricity and

diesel engines, which power every tanker and every container ship besides energizing most of the trucks and freight trains.

The process of process is also how we got gas turbines (jet engines) and nuclear reactors, and many other taken-for-granted converters and processes. Ditto for solid state electronics that has evolved from crude transistors in the Bell Laboratories in the late 1940s to the now ubiquitous microprocessors.

Moore’s Curse

Unfortunately, this conquest of the modern world by microchips has helped to create a warped image of a universally accelerating technical progress, one that has been unthinkingly promoted both by computing gurus (Ray Kurzweil makes perhaps the most egregious claims, as he believes that the 21st century will be equivalent to 20,000 years of progress at today’s rate of advances) and politicians (nobody can compete with Al Gore in this category with his call for completely repowering America in just one decade). [Read more →]

January 11, 2010   1 Comment

The Iron Age & Coal-based Coke: A Neglected Case of Fossil-fuel Dependence

As an old-fashioned scientist, I prefer hard engineering realities to all those interminably vacuous and poorly informed policy “debates” that feature energy self-sufficiency (even Saudis import!), sustainability (at what spatial and temporal scales?), stakeholders (are not we all, in a global economy?) and green economy (but are not we still burning some 9 billion tonnes of carbon annually?).

High regard for facts and low regard for wishful thinking has forced me to deal repeatedly with many energy illusions–if not outright delusions–and to point out many complications and difficulties to be encountered during an inevitably lengthy transition from an overwhelmingly fossil-fueled world to economies drawing a substantial share of their primary energies from renewable sources.

Steel & Coal-Derived Coke

Here is another challenge for the energy transformationists, one that is both inexplicably neglected and extraordinarily important: steel’s fundamental dependence on coal-derived coke with no practical substitutes on any rational technical horizon.

Those with a warped understanding of the real world might scoff: steel? Is not the electronics everything that matters in the post-industrial world? Yes, according to scientifically illiterate media and to the ceaseless self-promoting noise coming from assorted software companies. But, contrary to these naïve perceptions of reality, ours is still very much the Iron Age and not a Microprocessor Age. [Read more →]

September 17, 2009   10 Comments