The Azimuth Project
Vaclav Smil (changes)

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Vaclav Smil is a energy/environment academic and thinker who works on energy technology. His papers are on our list of recommended reading:

Interview

Here is an interview with Vaclav Smil:

And here is an excerpt:

Q: In Prime Movers of Globalization, you write about the under-appreciated impact of the diesel engine and the gas turbine on modern civiliza­tion. Can you summarize their importance?

A: Any imported manufactured products (that is, the bulk of consumer goods sold in North America today) came either on a container ship and was then loaded onto a truck for the final delivery (all powered by diesels) or as jet cargo (powered by gas turbines). All intercontinental trade in coal, oil and natural gas, ores and fertil­izer goes in large vessels powered by massive diesels. All long-distance flight is powered by GE, Pratt & Whitney and Rolls Royce gas tur­bines: from moving materials and products to moving people, the modern global economy rests on those two prime movers.

Q: Why are these engines more important than, say, the steam engine or the gasoline-powered automobile engine?

A: Both steam engines and gasoline-powered internal combustion engines are not powerful enough to propel massive container or bulk cargo ships (they carry commonly 250,000 tonnes of load) and are horribly inefficient compared to massive diesels, the only prime movers that can now convert half of all fuel into useful energy.

And no prime mover is more reliable than a gas turbine powering an intercontinental jet.

Q: How much longer do you think modern economies will rely on oil, and what do you think of some of the proposed alternatives, such as bat­teries and fuel cell or even solar and wind power?

A: That depends not only on how much coal, oil and gas we will move from resource to reserve category (resources of everything are still plentiful, but the cost of their recovery and the environmental impacts are a different matter), but also how much we will eventually consider enough. Canadians and Americans consume twice as much energy per capita as the richest EU countries or Japan — without, obviously, be­ing twice as rich, smart or happy. Besides, no al­ternative is, as yet, available at a scale needed to make a difference to the global supply, that is on the order of hundreds of gigawatts for electricity generation, and hundreds of millions to billions of tonnes of oil equivalent in terms of fuel supply.

Power density

One of these papers is an interesting introduction to the concept of power density: the amount of power that can be produced per square meter of land (or water) by a given technology:

• Vaclav Smil, Power density primer: understanding the spatial dimension of the unfolding transition to renewable electricity generation.

It makes the point that switching to renewable forms of energy will require us to adapt to vastly lower power densities—a point also made by Saul Griffith.

Here are some of Vaclav Smil’s results:

  • Most large modern coal-fired power plants generate electricity with power densities ranging from 100 to 1,000 W/m2, including the area of the mine, the power plant, etcetera.

  • No other mode of large-scale electricity generation occupies as little space as gas turbines: besides their compactness they do not need fly ash disposal or flue gas desulfurization. Mobile gas turbines generate electricity with power densities higher than 15,000 W/m2 and large (>100 MW) stationary set-ups can easily deliver 4,000-5,000 W/m2. (What about the mining?)

  • The energy density of dry wood (18-21 GJ/ton) is close to that of sub-bituminous coal. But if we were to supply a significant share of a nation’s electricity from wood we would have to establish extensive tree plantations. We could not expect harvests surpassing 20 tons/hectare, with 10 tons/hectare being more typical. Harvesting all above-ground tree mass and feeding it into chippers would allow for 95% recovery of the total field production, but even if the fuel’s average energy density were 19 GJ/ton, the plantation would yield no more than 190 GJ/hectare, resulting in harvest power density of 0.6 W/m2.

  • Photovoltaic panels are fixed in an optimal tilted south-facing position and hence receive more radiation than a unit of horizontal surface, but the average power densities of solar parks are low. Additional land is needed for spacing the panels for servicing, access roads, inverter and transformer facilities and service structures — and only 85% of a panel’s DC rating is transmitted from the park to the grid as AC power. All told, they deliver 4-9 W/m2.

  • Concentrating solar power (CSP) projects use tracking parabolic mirrors in order to reflect and concentrate solar radiation on a central receiver placed in a high tower, for the purposes of powering a steam engine. All facilities included, these deliver at most 10 W/m2.

  • Wind turbines have fairly high power densities when the rate measures the flux of wind’s kinetic energy moving through the working surface: the area swept by blades. This power density is commonly above 400 W/m2 – but power density expressed as electricity generated per land area is much less! At best we can expect a peak power of 6.6 W/m2 and even a relatively high average capacity factor of 30% would bring that down to only about 2 W/m2.

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