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Wind Is Not Power At All (Part II Power Density) MasterResource

Part I of this three-part series set the stage for examining intermittent power sources, especially wind, as viable sources of electricity. Part 2 addresses

one of the critical power considerations:power density.

In his MasterResource series, Vaclav Smil compared the power

densities of a range of fuels for electricity production, which

demonstrates the inadequacies of renewables. David MacKay also

makes a useful contribution to this topic.[i] Table 1 summarizes the

results, which take into account entire fuel cycles, transportation and

transmission requirements for a range of assumptions.

Note that all renewable energy sources are ten to over a thousand

times less effective than those serving our needs today, with wind

providing one of the poorest performances of the renewable sources

shown, outside of wood. Areas required for renewables are large

because of the dispersed, and often remote, nature of their energy

supply.

The problem that this presents is that our current electricity

infrastructure is based on high power density generation facilities

supplying the low power densities of users, and in general, user

power density is about ten times higher than most renewable sources,

including wind.[ii]

In the case of wind, it is acknowledged that some agricultural

activities may be possible within the areas needed for wind turbineseparation, although there is growing experience that this may not be

the case (see here and here), but this misses the point that many

activities will not, and substantial implementation of wind will

increasingly impose on these. Also, there are space requirements

beyond the wind turbine base footprint, for example, access roads

and additional buffer zones for a variety of reasons, including human

habitation and increased transmission lines (more on this later).

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Table 1 Power Densities for Selected Fuels for Electricity

Generation

Notably missing in the aboveare nuclear and hydro plants.

Based on land claims for fuel

extraction, processing and

waste storage, nuclear plants

are in about the same range as

fossil fuel plants.[iii] Smil also provides a more general

representation as shown in Figure 1, which does include hydro, and

for which there are two representations; the higher power density for

upper-course sites, and the other for lower-course sites.[iv]

The power density of fossil fuel and nuclear electricity plants is the

same order of magnitude of the total power for an average

tornado.[v] The power density of wind is closer to that of a horse.[vi]

Figure 1 Power Densities of Fossil Fuel Extraction and

Generation Compared to Renewable Energy Conversions

Hydro-electric sources have low

power densities because of the

size of water reservoir areas,

which are estimated to account

for about one-half of the total

land requirements for all aspects

of electrical energy conversion,

which includes mines, oil and

gas fields, refineries, pipelines,

generation plants and

transmission.[vii]

The next largest category is transmission lines, accounting for about

one-quarter of land requirements for electricity generation. This is

important because the current emphasis on additional transmission

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lines to accommodate new renewables, especially wind with the

quantities projected, adds substantially to the areas required to

support these energy sources. The existing grid fans out from todays

high power density generation sites to the low power density (diffuse)

consumption requirements of buildings, factories and cities. Wind

and solar require large grid increases to provide an additional

fanning out at the generation end because of the inflexibility and

dispersion of the locations required to collect the diffuse energy

supply.

Apart from the not inconsequential grid considerations, what is the

significance of the low power density of renewables? Any

transformation from todays high power density generation facilities

will require many significant adjustments, which will take decades to

accommodate for economic, technological (e.g., massive storage

capabilities and electrification of transportation) and societal and

human nature reasons. The latter refers to the need for the developed

nations to adjust their use of primary energy supply use downwards

to allow for the inevitable growth of this in developing countries.

Other factors include de-urbanization (in part moving closer to the

sources of renewable energy), substantially more careful use of

energy, significantly improved energy efficiency in buildings (which

depends largely on new structures, for example, designed to better

accommodate substantially improved photo-voltaic energy

converters), transportation and distribution systems (e.g., for

distribution of hydrogen fuel produced centrally by renewable

sources, if this proves feasible). The practical time frames for these

are many decades, and for some, the end of the 21st century.

As described in Part I, this time scale creates a race with that for

concerns about climate change impacts. Therefore short to medium

term policies (the next 10-30 years) should focus on those electrical

energy sources that have the energy and capacity requirements that

best address this.

The net of this is that the current rush to massive implementations of

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wind plants is an extremely premature, unwise policy. Of the two,

wind and solar, direct tapping of solar energy has by far the most

useful and effective outlook for renewables, but the entry point for

utility-scale commercialization of this is still many decades away. We

need a well thought out energy use evolution in the meantime, not a

revolution.

Based on power density, this is how Smil summarizes the outlook for

renewables:

As a result, these new energy infrastructures would have to be spread

over areas ten to a thousand times larger than todays infrastructureof fossil fuel extraction, combustion and electricity generation: this is

not an impossible feat, but one posing many regulatory

(environmental assessments of affected areas, rights-of-way

permission and inevitable lawsuits), technical and logistic

challenges.Higher reliance on renewable energies may be desirable

(mainly because ofperceived environmental and strategic reasons)

and technical advanceswouldalso make it an increasingly

appealing economic choice-but inherently low power densities of

these conversions will require a new system of fuel and electricity

supply that will be able to substitute for todays dominant practices

only after decades of gradual development.

Power density alone establishes wind as unworthy of the diversion of

significant amounts of national wealth, human resources, especially

within our governments, and time, all of which could be more

productively used.

However, wind also fails in the other dimension of powercapacity

value. This is the consequence of its randomness and intermittency of

supply, which has the effect of shifting the power density comparison

even less favorably for renewables. This will be addressed in Part III.

[i] MacKay, David (2008). Sustainable Energy without the hot

air. http://www.withouthotair.com/download.html

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[ii] Smil, Vaclav (2008). Energy in Nature and Society: General

Energetics of Complex Systems. The MIT Press. Page 383.

[iii] Smil, page 313.

[iv] Smil. pages 311-312.

[v] Smil, page 45.

[vi] Smil, page 156.

[vii] Smil, page 313.

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