Power density

Aggregate land claim of the global energy system in 2010

Download 0.52 Mb.
Size0.52 Mb.
1   ...   15   16   17   18   19   20   21   22   ...   25

Aggregate land claim of the global energy system in 2010

Process Power W/m2 ~ km2

Fossil fuel extraction 13.63 TW 12,000

Coal 4.72 TW 1,000 4,700

Crude oil 5.38 TW 1,000 5,400

Natural gas 3.53 TW 2,000 1,800

Crude oil refining 5.10 TW 5,000 1,000

Fuel transportation 27,000

Hydrocarbon pipelines 8.03 TW 300 27,000

Tanker terminals 2.21 TW 10,000 200

LNG terminals 364 GW 5,000 100

Thermal electricity generation 1.86 TW 2,100

Fossil-fueled electricity 1.54 TW 1,000 1,500

Nuclear plants 316 GW 500 600

Renewable energies 525 GW 398,000

Hydroelectricity 395 GW 3 131,700

Geothermal electricity 8 GW 50 200

Solar electricity 3 GW 5 600

Wind electricity 40 GW 20 2,000

(turbine spacing 1 40,000)

Modern biofuels 79 GW 0.3 263,300

Electricity transmission 2.30 TW 30 58,000

This summation (keeping in mind some its unavoidably broad error margins) means that in 2010 the world’s fossil fuel-based energy supply –- extraction of coals and hydrocarbons, their processing and transportation, thermal electricity generation and proportional claim of HV transmission ROWs (nearly 70% of the total) –- took at least 80,000 and no more than 90,000 km2 of the grand total, the latter total being an area smaller than Portugal or Hungary, and with 13.6 TW of primary fossil energy its average power density (counting the land devoted to fossil fuel-fired electricity generation) was roughly 150-170 W/m2.

Energy system that dominated the global supply during the past 50 years –- fossil fuels, thermal and hydro electricity generation, delivering 14.34 TW in 2010 –- claimed roughly 230,000 km2 (most likely range of 200,000-250,000 km2) of land that is either directly occupied or whose uses are restricted by the rights-of-way imposed by pipelines or HV transmission, which means that it has been operating with overall power density of about 60 W/m2. In comparison, the mean total is slightly smaller than Romania, the higher value is equal to about half of Spain and it is less than 0.2% of the Earth’s ice-free land. Leaving pipeline and transmission ROWs aside, the grand total comes to nearly 150,000 km2 (less than half of Poland) of which almost 90% is the land flooded by reservoirs although the global hydroelectric output reached only about 400 GW in 2010.

New renewables (solar PV, wind, geothermal, liquid biofuels) added up to a negligible total in 2010 (130 GW or 0.9% of all primary commercial energy flows in that year) –- but their combined land claim had surpassed the high estimate for the fossil-nuclear-hydro system. Solar-powered electricity generation claimed less than 1,000 km2 and wind turbines were spread over about 40,000 km2 when assuming actual generation density of 1 W/m2 and less than 1/20 of that area (< 2,000 km2) when counting only the land occupied by turbine pads and associated infrastructure. In 2010 biofuels (dominated by sugar cane and corn grown for conversion to ethanol) supplied only about twice as much power as wind –- 79 GW vs. 40 GW, that is an equivalent of less than 1.5% of the global crude oil output –- but their land claim was more than 260,000 km2, an area equal to almost 2% of arable land planted to annual crops (FAO 2014). Consequently, even when using minimal wind turbine claims, modern renewables (without hydroelectric plants) required almost 270,000 km2 to deliver 122 GW, implying an overall mean power density of less than 0.5 W/m2.

Final comparisons are between the power densities of energy production and final uses of fuels and electricity. Hierarchy of final uses proceeds from annually averaged power densities of around 3 W/m2 for small, densely populated modern economies to between 10-30 W/m2 for many urban areas to more than 100 W/m2 for city downtowns. This leads to a number of revealing conclusions. Perhaps most importantly, fossil/hydro/nuclear systems that dominate energy supply in modern affluent economies has been operating with overall power density that is (depending on climate, population density and level of industrialization) mostly two to four times that of power required by large urban areas.

Fossil fuels (including transportation and transmission ROWs) generally supply energy with power densities higher than those prevailing in city downtowns, and the only instances where power densities of energy use surpass those of common ways of energy production are the in city blocks consisting of densely packed high-rise buildings (on the annual basis they can go well above 500 W/m2) and during short periods of peak demand in (driven by winter heating or summer air conditioning) in downtown cores where they can go to as much 1,000 W/m2 or even more.

A table makes it easy to appreciate how small is the absolute claim of modern energy infrastructure in comparison to other human activities that have modified large parts of roughly 130 Tm2 of the Earth ice-free surface:

Terrestrial areas modified by human action ~ 2010*

Activity Area (1,000 km2) % of ice-free land

Arable land and permanent crops 16,000 12.3

Area affected by logging 3,000 2.3

Forest and tree plantations 3,000 2.3

Urban areas (including roads) 4,000 3.1

Impermeable surfaces 600 0.5

Reservoirs 600 0.5

Fossil fuels extraction 15 0.01

Rights of way (pipelines, HV lines) 90 0.07

Hydro reservoirs 150 0.1

Modern energy system 250 0.2

*Data from FAO (2014), Hooke, Martín-Duque and Pedraza (2012), from previously cited studies of urban areas and ISA, and from the preceding table.

US energy system Spatial requirements of America’s energy system can be estimated more accurately than the total of land claimed by the global energy production, processing and distribution. I use supply specifics from official statistics (primarily USEIA) and, once again, assume fairly liberal means of power densities and round the totals to the nearest 50 km2. Fossil fuel extraction claimed roughly 6,000 km2, fuel processing (mainly crude refining and crude oil and oil product imports by tankers) needed less than 500 km2 and ROWs of hydrocarbon pipelines pre-empt most of the other land use on about 15,000 km2 (this total excludes gas distribution lines within cities).

Coal transport by railroads is an important part of the US energy system: in 2010 about 40% of all transported mass was coal (AAR 2013), but as only a small minority of lines is dedicated solely to coal shipments the only imperfect way to proceed is to attribute roughly 40% of ROWs of high-density “A” track (approximately 3,100 km2: 30-m ROW for 104,000 km) to coal; that would add about 1,200 km2. Thermal electricity-generating plants (including the domestic part of uranium fuel cycle) occupied less than 600 km2, reservoirs used for hydrogenation covered at least 17,000 km2, and HV transmission’s ROWs extended over nearly 16,000 km2.

Aggregate land claim of the US energy system in 2010

Process GW W/m2 ~ km2

Fossil fuel extraction 1,847.4 5,550

Coal 734.1 1,000 750

Crude oil 443.4 100 4,450

Natural gas 669.9 2,000 350

Oil tanker terminals 534.6 10,000 50

Crude oil refining 1,077.6 3,000 350

Fuel transportation 13,000

Oil pipelines 291,300 km 15 m ROW 4,400

Gas pipelines 494,300 km 15 m ROW 7,400

Coal shipments 40% of 3,100 km2 1,200

Fossil-fueled electricity 329.1 250

Coal 210.9 1,000 200

Gas and oil 118.2 3,000 50

Nuclear electricity 92.1 300 300

Hydro electricity 29.7 1.7 17,500

New renewables 124,600

Geothermal electricity 1.7 50 50

Wind electricity 10.8 20 550

(turbine spacing 1 10,800)

Ethanol 34.1 0.3 ~ 114,000

Electricity transmission* 470 30 15,700

*total power includes burning of wood waste

The entire fossil-nuclear-hydro energy systems thus required (including transmission ROWs) almost 53,000 km2 (that is roughly 0.5% of the US territory, and an area roughly half the size of Virginia or Tennessee), of which some 30,000 km2 (55%) were ROWs and nearly a third water reservoirs, while fossil fuel-based supply (including pipeline and railway ROWs) claimed only about 19,000 km2. For the completeness sake the nationwide fossil fuel-based total should be enlarged by the area of abandoned wasteland created by surface extraction of bituminous coal that has yet to be reclaimed. During the first decade of the 21st century the difference between new permits for surface coal mining and bond releases (issued after the completion of planned reclamation) was on the order of 250 km2 a year and that would imply the growth of unreclaimed land debt by more than 2,000 km2 per decade.

But that is both too much and too little: too little because in forested areas (particularly in Appalachian mountaintop removal) even the best reclamation effort cannot recreate the original plant composition and an ecosystem that would closely resemble it may get re-established only after decades, even centuries; too much because in some locations (particularly in regions originally covered with shrubland or grasses) unreclaimed, abandoned areas can become naturally revegetated in a matter of years without any deliberate reclamation effort. In any case, it should be remembered that the overall land claim attributable to the US coal extraction is definitely higher than my approximation.

Hydroelectricity is the traditional source of renewable energy with by far the largest land claim among mature energy conversion, while relatively small contribution by geothermal electricity (< 2 GW in 2010) requires less than 50 km2 and electricity generated by combustion of woody phytomass (about 5 GW) comes mostly from burning logging residues and does not create any additional space claims and hence is not included in the aggregate count. Of the three kinds of new renewable energy supply PV-based solar electricity generation was still minuscule in 2010 (< 50 MW) but wind turbines contributed 10.8 GW, equal to slightly more than a third of hydro generation. They were spread over an area of nearly 10,000 km2 but the actually occupied land (mostly by their tower pads and access roads) was only on the order of 500 km2 (less than six Manhattans). But in 2010 nearly 29% of both corn and sorghum harvests were used to produce ethanol, and cultivation of those crops claimed about 124,000 km2; that was an area larger than Pennsylvania and three times as large as all land (including all ROWs) claimed by the entire US fossil-nuclear-hydro energy system.

Once again (and keeping in mind a number of inevitably simplifying approximations) these nationwide summations lead to interesting insights. Mainly because of a very large number of old, low-productive oil wells the average power density of US fossil fuel extractions (roughly 1.85 TW, roughly 6,000 km2) is relatively low at about 300 W/m2. Imports and processing of fossil fuels (dominated by shipments of crude oil and refined products and by refining of domestic and imported crude) make a relatively small spatial claim (<500 km2), a total smaller than an unavoidable margin of error in estimating fuel extraction claims.

ROWs of oil and gas pipelines are 2.5 times as large as the land taken by the extraction of all hydrocarbons. Coal extraction, thanks to highly productive Western surface mines, claims less than 1,000 km2 and more land is occupied by ROWs of railroad coal transportation when they are apportioned according to the coal’s share in annual mass of rail shipments on high-density lines. America’s fossil fuel-fired electricity generation (fuels needed to energize it have been already accounted for) occupies less than 300 km2 and nuclear generation (including fuel supply) takes up a similar amount of space -– and land requirements of both of these industries are dwarfed by the land flooded by reservoirs use for hydroelectric production and by ROWs of HV transmission lines.

The country’s dominant fossil-nuclear-hydro energy supply system whose domestic primary power output reached about 2 TW in 2010 had overall power density of close to 40 W/m2 as three of its low-density components, hydrogeneration and pipeline and transmission ROWs overwhelmed high power densities of fossil fuel extraction and processing. The rate will naturally increase when counting the total energy input: net fossil fuel imports added about 750 GW to the domestic production and power density of the entire system would be about 50 W/m2. As expected, overall power density of the nascent energy supply delivered by new conversions of renewable sources is much lower: the growing triad of wind turbines, solar electricity and liquid biofuels reached a bit over 60 GW in 2010 and even after counting only the land actually occupied by wind turbines and their infrastructure the new renewable system delivers with overall power density of less than 0.5 W/m2.

Additional annual land claims cannot be estimated by simply applying appropriate power densities to specific expansions of fuel extractions and electricity generation or to extension of pipelines and HV lines. This is why such simplistic extrapolation would end up with substantial errors: in some localities land disturbances created by surface coal mining are more than matched by mandatory reclamation of old abandoned wasteland; directional drilling of multiple wells from a single well-pad reduces specific land claims of new wells; new refinery capacities and new natural gas-fired generation can be accommodated within the sites of existing facilities; some new transmission lines and some new pipelines can use, fully or in part, the existing ROWs. As a result, my best estimate is that recent net annual additions (for land actually transformed by new energy projects and for new ROWs) have been less than 500 km2.

I will close this section in the same way as I did the previous one, by contrasting land claims of US energy production with other important land uses. Here they are in descending order: protected areas in national parks are just over 2,600,000 km2 (27% of the nation); arable land and permanent crops occupy 1,630,000 km2 while the recently harvested area of annual crops has averaged less than 1,400,000 km2; as I have already explained, urban areas (including also grassy and treed surfaces) take up about 150,000 km2 and impervious surface areas (just buildings and paved surfaces) amount to about 50,000 km2.

This means that the US fossil-nuclear-hydro energy system (including all ROWs) is almost exactly as extensive as are the country’s impervious surface, and that the land taken up by cities (including their green surfaces) is roughly three times as large as the dominant energy supply system consisting of fossil fuels and nuclear and hydro electricity. Inversely, this means that for every 3 m2 of urban areas (where most of the modern energies are used) there is roughly 1 m2 of land that is either transformed or whose other uses are largely pre-empted by extraction, conversion, transportation and transmission components of the US fossil-hydro-nuclear energy system.

In contrast, in 2010 ethanol delivered an equivalent of only about 5% of the country’s motor gasoline supply but production of its primary feedstock (grain corn) required roughly four times as much land as the entire US fossil fuel-hydro-nuclear energy system. This brings me to the closing chapter of the book in which I will look at how much land these new renewables would require if they were to displace entirely our current reliance on fossil fuels and nuclear fission; in other words, I will examine the unfolding energy transition through the prism of power densities



Unfolding energy transition from systems dominated by fossil fuels and thermal generation of electricity to new arrangements where new forms of renewable energy conversions become more important dictates the book’s final chapter: I will look at this transition through the prism of power densities and offer some conclusions about the import and consequences of these new realities.

We are at the beginning of another epochal shift to new sources of energy. Timing of the first shift, to use energy other than the work of our muscles, cannot be determined with accuracy as the earliest confirmed or estimated dates of controlled use of fire have been steadily receding and now appear to be at least 105 years ago (Smil 2013). The second shift began to take place more than 5,000 years ago with the domestication of domestic draft animals: greater power of cattle and horses was a critical component in the evolution of traditional agriculture, land transport and large-scale construction. Only millennia later did the settled societies added limited use of wind and water harnessed by sails, wind mills and water wheels.

Combination of these traditional sources –- human exertions, combustion of phytomass, use of draft animals and small-scale low-efficiency conversions of wind and flowing water -– characterized all pre-industrial societies. This pattern began to change only in the early modern era with the rising combustion of coal in the UK and in few European regions; during the latter half of the 19th century hydrocarbons were added to the rapidly expanding use of coal and the introduction of large boilers, internal combustion engines, steam turbogenerators and thermal electricity generation accelerated the transition from phytomass to fossil fuels.

Modern civilization is thus a material and intellectual embodiment of converting fossil fuels into useful energies of heat, electricity, motion and chemical potential. Of course, photosynthesis remains the planet’s most important energy conversion as it powers all life (with the minuscule exception of deep-sea organisms aggregating near hot thermal vents) but our relative reliance on phytomass fuels has been steadily declining since the mid-19th century. Combustion of these fuels energized first the shift from foraging to agricultural societies and, millennia later, to urbanization and, later still, to incipient industrialization.

By 1850 coal, the only commercially extracted fossil fuel, supplied less than 10% of the world’s primary energy, and during the closing years of the 19th century gross energy content of traditional phytomass fuels (wood and charcoal and straw) and fossil fuels became even. At the beginning of the 21st century fossil fuels (now dominated by crude oil) supplied just over 80% of the world’s primary energy and because of their more efficient conversions in boilers, furnaces and engines they provided more than 90% of all useful energy (Smil 2010a). And the origins of modern commercial energy supply in the world’s largest economies are even more heavily tilted toward fossil fuels. In 2012 fossil energies supplied 94% of Japan’s, 91% of China’s, 89% of Russia’s, 87% of the US and 83% of Germany’s primary energy demand, with the largest share of non-fossil energies originating either in nuclear power (in the US and Russia) or in hydro power (in China and Japan).

New kinds of renewables –- dominated by wind and solar PV in Germany and China and by liquid biofuels in the US –- reached the highest share of the overall supply in Germany where preferential policies pushed their share to 8.3% of all primary energy by 2012 (BP 2013). Elsewhere the contributions of new renewables were much lower, with 2.3% in the US, 1.7% in Japan, and 1.2% in China, and in Russia (with 0.01% of the total supply) these alternatives were essentially absent. These realities make it clear that the transition from fossil fuels to new renewables will be, much like all previous energy transitions, a gradual, protracted affair that will take place over many decades.

There are two kinds of arguments in favor of an accelerated shift away from fossil fuels: concerns about their future supply, and worries about long-term environmental consequences of their combustion. The first worry has been around for generations but it has received a great deal of post-2000 attention in many publications detailing assorted scenarios of peak oil, peak coal and peak everything (Smil 2010; 2013a) and predicting, even pinpointing, the dates when the world’s crude oil production will begin to decline. Production realities do not reflect any convincing signs of an imminent global peak for any fossil fuel extraction, and the best appraisals of remaining coal and hydrocarbon resources indicate supply sufficiency for decades to come.

The argument can then readily shift to quality and cost. Of course, since the beginning of our exploitation of fossil fuels the running-out argument has always applied much more convincingly to their richest, most accessible deposits that could be extracted with the lowest expenditures. Consequently, running out of fossil fuels (of any quality and producible at any cost) may be a slow process with no imminent ends, but diminishing reserves in many of the most accessible deposits in the richest coal seams and hydrocarbon reservoirs in the areas that have been explored and exploited for generations has been an undeniable reality. One of its latest impressive demonstration has been the cost of bringing new crude oil to the market: in 2013 no new major oil project (with at least 300 Mb in estimated lifetime output) added in the previous two years had breakeven cost below $70/b (Goldman Sachs 2013).

The environmental imperative for accelerated shift away from fossil fuels –- the need to slow down and eventually to reverse anthropogenic global warming induced by combustion fossil fuels -- has dominated the quest for new renewables since the late 1980s. The only two technical solutions that would obviate global decarbonisation would be a massive development of nuclear power or an equally large-scale effort to capture and to sequester CO2 generated by fossil fuel combustion. Both of these options have their strong advocates but there is no evidence of any commensurate deployment. Nuclear power is either stalled (US) or on the way out (EU), with more than 40% of all (66) under construction in China and 75% of them in just four countries, China, Russia, India, and South Korea (IAEA 2012a; Schneider et al. 2013). And most of the proposed carbon capture and sequestration projects have been shelved or postponed (Global CCS Institute 2014). There is a third option, climate engineering, but its efficacy, practicality and acceptance are even more uncertain (Keith 2013).

By 2012 nearly 140 countries had policy targets for energy supply provided by renewables, ranging from modest shifts to profound changes: in the UK the target is 15% of all energy from renewables by 2020 (Department of Energy and Climate Change 2013), in Germany it is 30% by 2030 and 80% by 2050 (REN21 2013). Moreover, some studies even argued that it would be perfectly possible to have all new energy demand supplied by renewables (wind, water and solar) by 2030 and the world’s total energy demand by 2050 (Jacobson and Delucchi 2011) –- and the latest incarnation of this plan sees the New York state completely energized by nothing but renewably generated electricity by 2030 (Jacobson et al. 2013). I have shown in a great detail that no worldwide energy transition has ever been (indeed can not ever be) so rapid (Smil 2010a), and that none has ever resulted in a complete domination by a single energy source as would be the case with renewably generated electricity that would be also used to produce hydrogen for fuel cells and direct combustion.

Apparently, such realities do not matter where theoretical calculations reign. Of course, a theoretical option might consider only electricity generation: if it were exceptionally inexpensive electricity could be used as the foundation of a new hydrogen economy, a solution advocated by some enthusiasts for decades (Dickson, Ryan and Smulyan 1977; Ball and Wietschel 2009). In reality, we could not convert every convertible industrial, transportation, residential and commercial uses to electricity in just 15 years, and we would still need fuels in order to produce heat and supply the reducing agent for iron smelting, to provide important industrial feedstocks (needed to replace fossil hydrocarbon feedstocks that now dominate many chemical syntheses) and, of course, to energize our land, water and air transportation: the world’s fleets of heavy truck or container ship appear unlikely to run on electricity or fuel cells anytime soon, to say nothing about electric or cell-powered commercial jetliners.

That is why, being a realist, I insist that, regardless of the pace and specific national circumstances, if an accelerated transition to new renewables were to succeed it would have to deliver both electricity and fuels. And, obviously, it would have to do so on multi-GW scales in large countries and on TW scale globally. Consequently, I will examine first the spatial implications of displacing all liquid fossil fuels by biofuels and all metallurgical coke by charcoal and then I will take a closer look at wind and solar electricity in the unfolding energy transition before closing the chapter with quantitative illustrations of what it would take to create a completely renewable energy system.

Share with your friends:
1   ...   15   16   17   18   19   20   21   22   ...   25

The database is protected by copyright ©sckool.org 2019
send message

    Main page