Renewable Energy's 'Footprint' Myth

Electricity Journal

Volumn 24, Issue 6, 2011, Pages 40-47

  Lovins, Amory B ^a  

^a ROCKY MOUNTAIN INSTITUTE   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

NUCLEAR ENERGY; NUCLEAR FUELS;

ENVIRONMENTALLY ACCEPTABLE; ORDERS OF MAGNITUDE; RENEWABLE ELECTRICITY; RENEWABLE ENERGIES;

LAND USE;

EID: 79960560616     PISSN: 10406190     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tej.2011.06.005     Document Type: Article

References (33)

1. National Renewable Energy Laboratory and AWS Truewind, Estimates of Windy Land Area and Wind Energy Potential by State for Areas ≥30% Capacity Factor at 80 m, Feb. 4, 2010.
2. M.B. McElroy, Xi Lu, C.P. Nielsen and Yuxuan Wang, Potential for Wind-Generated Electricity in China, Science 325:1378 (Sept. 11, 2009) at www.sciencemag.org/cgi/content/full/325/5946/1378, doi:10.1126/science/1175706.
3. C.L. Archer and M.Z. Jacobson, Evaluation of Global Windpower, at www.stanford.edu/group/efmh/winds/global_winds.html. Class ≥3 sites (≥6.9m/s), normally competitive with new coal power at zero carbon price, could yield ~72TW at 80-m hub height. Contrary to the widespread impression that the best lower-49-states wind areas are only in the Great Plains, the East Coast, and certain West Coast sites, the data show that the Great Lakes wind resource, conveniently near upper Midwest load centers, is also Class 6±1. (It needs marine cables and engineering plus ice protection, but is much closer than Dakotas windpower.) The underlying data are in J. Geophys. Res. 110 (2005), D12110, doi:10.1029/2004JD005462, at www.stanford.edu/group/efmh/winds/2004jd005462.pdf. The global windpower potential will become far larger even just on land if tethered high-altitude wind-turbine R&D projects succeed.
4. M.Z. Jacobson, Review of Solutions to Global Warming, Air Pollution, and Energy Security, En. & Envtl. Sci. 2:148-173 (2009), at www.stanford.edu/group/efmh/jacobson/PDF%20files/ReviewSolGW09.pdf.
5. World Energy Council, at www.worldenergy.org/publications/survey_of_energy_resources_2007/solar/720.asp. Variation within the continental U.S. is smaller: Buffalo gets only one-fourth less and Arizona one-fourth more annual sunlight than Kansas City - less than regional differences in conventional energy prices (note 27). For detailed U.S. solar resource data.
6. see http://rredc.nrel.gov/solar/pubs/redbook/.
7. USDOE and Electric Power Research Institute, Renewable Energy Technology Characterizations, TR-109496, 1997, at www.nrel.gov/docs/gen/fy98/24496.pdf, at 4-19. See also M.Z. Jacobson and M.A. Delucchi, A Path to Sustainable Energy by 2030, Sci. Am., Nov. 2009, at 58-65; on PVs, V. Fthanakis, J.E. Mason and K. Zweibel, En. Pol. 37:387-399 (2009).
8. See also M.Z. Jacobson and M.A. Delucchi, A Path to Sustainable Energy by 2030, Sci. Am., Nov. 2009, at 58-65; on PVs, V. Fthanakis, J.E. Mason and K. Zweibel, En. Pol. 37:387-399 (2009).
9. V. Fthanakis, J.E. Mason and K. Zweibel, En. Pol. 37:387-399 (2009).
10. Including U.S. Sen. Lamar Alexander, who predicts that renewables, if unchecked, will "consume" an area bigger than Nebraska: Energy 'Sprawl' and the Green Economy, Wall St. J., Sept. 18, 2009, at http://online.wsj.com/article/SB10001424052970203440104574404762971139026.html; The Perils of 'Energy Sprawl', Oct. 5, 2009, at http://alexander.senate.gov/public/index.cfm?FuseAction=Speeches.Detail&Speech_Id=0a6f9273-5dbc-4c37-99b6-a9940780c51d.
11. The Perils of 'Energy Sprawl', Oct. 5, 2009, at http://alexander.senate.gov/public/index.cfm?FuseAction=Speeches.Detail&Speech_Id=0a6f9273-5dbc-4c37-99b6-a9940780c51d.
12. A cautionary note: land-use analyses assess land transformation (m) - land altered from a reference state - or land occupation (m-y) - the product of area occupied times duration of occupancy - for various energy outputs or capacities. The results can be hard to interpret if durations are long, effects are partly irreversible, or impacts are incommensurable. For example, the facilities and activities on a nuclear or coal system's land are often more permanent and damaging than windpower or solar installations, which can readily be removed altogether. Most metrics used here are, or are converted to, occupancy (simple land areas) to reduce the risk of unit confusion.
13. Ref. 6, at 161. By international norms, the minimum buffer zone is 200ha or 0.77mi: GEN IV International Forum, Cost Estimating Guidelines for Generation IV Nuclear Energy Systems, Ref. 3.03b, Sept. 29, 2006, at http://nuclear.inl.gov/deliverables/docs/emwgguidelines_ref3.03b.pdf. We don't count here the ~10-mile radius typical of the Emergency Planning Zone in which public activities are permitted.
14. J.G. Delene, K.A. Williams and B.H. Shapiro, Nuclear Energy Cost Data Base, DOE/NE-0095 (1988), cited in Spitzley and Keoleian, supra note 11. Kim and Fthenakis, both of Brookhaven National Laboratory, give a similar figure of 52W/m/GWh or, for our nominal 1GW plant, 6.3mi: The Fuel Cycles of Electricity Generation: A Comparison of Land Use, Mater. Sci. Soc. Symp. Proc. Vol. 1041, 1041-R05-03 (2008). Fthenakis and Kim, supra note 17, expand this analysis to include the full nuclear fuel cycle.
15. D.V. Spitzley & G.A. Keoleian, "Life Cycle Environmental and Economic Assessment of Willow Biomass Electricity: A Comparison with Other Renewable and Non-Renewable Sources," Rpt. #CSS04-05R, 2004, Center for Sustainable Systems, University of Michigan (Ann Arbor), cite at p. 57 some 2000 DOE data (www.eia.doe.gov/cneaf/nuclear/page/umtra/title1map.html) showing that 18 U.S. decommissioned uranium mines and mills disturbed an average of 0.025ha/tU3O8 for 15 years. However, those 18 operations ran from the 1940s to 1970, and during 1948-70, the average U.S. ore milled contained 0.453% U3O8 (author's analysis from USEIA, Uranium Industry Annual 1992, DOE/EIA-0478(92), http://tonto.eia.doe.gov/FTPROOT/nuclear/047892.pdf, p. 37). Through the mid-1980s, the modern ore grade reflecting most of the U.S. resource base averaged ~0.1% U3O8 (G.M. Mudd & M. Diesendorf, "Sustainability of Uranium Mining and Milling: Toward Quantifying Resources and Eco-Efficiency," Environ. Sci. Technol. 42:2624-2630 (2008), Fig. 1). Assuming, probably conservatively, a constant stripping ratio over the decades, the historical land-use of ~0.025ha/tU3O8 should therefore be adjusted to a modern U.S. value ~4.5×higher, or ~0.112ha/tU3O8. According to www.wise-uranium.org/nfcm.html, a modern EPR-class reactor (4.0% enrichment, 45GWd/t burnup, 0.9 capacity factor, 0.36 thermal efficiency) uses ~219tU3O8/y on standard assumptions, or 8,769tU3O8/40 y - hence a lifetime total of 986ha, or 3.8mi, for the nominal 1GW plant. (That figure would be comparable at Australian ore grades; higher at South African; and lower for Canadian, especially for two extraordinarily high-grade but short-lived deposits: see E.A. Schneider & W.C. Sailor, "Long-Term Uranium Supply Estimates," Nucl. Technol. 162:379-387 (2008).) Fthenakis and Kim, supra note 17, is in excellent agreement at 3.66mi. As a cross-check of reasonableness, at a nominal 0.1% ore grade and 91.5% recovery, the modern 1GW nuclear plant's uranium consumption over 40 y will produce roughly 8.94 million short tons of mill tailings. The tailings piles at 26 uranium mills reported at p. 7 of EIA's 1992 Uranium Industry Annual averaged 46,327 ston tailings per acre (24ft thick), committing 193 acres or 0.30mi for the 1GW plant's tailings; at the modern 0.1% ore grade this would be ~1.35mi. Adding the mine area and waste rock disposal (a typical stripping ratio is ~5, and it swells when removed, so it can't all go back in the excavated area) obtains reasonable agreement.
16. see E.A. Schneider & W.C. Sailor, "Long-Term Uranium Supply Estimates," Nucl. Technol. 162:379-387 (2008)
17. The traditional U.S. method of enrichment (coal-fired gas diffusion, 0.3% tails assay) would use during the 1GW plant's 40-year life ~10TWh to power separative work of ~4.3 million SWU. According to Spitzley & Keoleian, average U.S. pulverized-coal-fired electricity averages a land commitment of 580ha-y/TWh, so we must add another ~5,800ha-y or 22mi-y to power the enrichment - less with centrifugal enrichment or with less land-intensive electricity sources. Such a reduced modern estimate, from Fthenakis and Kim, supra note 17, is presented below.
18. The Yucca Mountain high-level waste repository, according to D. Bodansky's data cited by Spitzley & Keoleian (ref. 11), commits 6.2km×(40y×23t spent fuel/y/70,000t facility capacity); but those authors failed to notice that this counts only the facility's direct footprint. Dr. Bodansky omitted its permanently withdrawn, DOE-controlled exclusion zone of ~600km (232mi, 150,000 acres; see Final EIS, pp. 4-5 and 2-79), thus understating its land-use by 97× as ~0.08 rather than the correct ~7.7km for the nominal 1GW plant. (That plant's lifetime spent-fuel output of ~920t represents 1.3% or 1.5% of Yucca Mountain's 63,000tHM or ~21PWh of authorized capacity.) Kim & Fthenakis, supra note 17, derive 29m/GWh, or 3.5mi for our nominal 1-GW plant.
19. I have not found reliable data, other than old DOE data in Fig. 1, on the minor land-uses for uranium conversion, enrichment, or fuel fabrication facilities including exclusion zones, nor for any land commitment for cooling water.
20. That is, (7+3.8+0.55+3)/0.33=14.35, which is 43× Cravens's 0.33. As a cross-check, using slightly different global-average nuclear data, Jacobson, supra note 4, uses the Spitzley & Keoleian data to calculate a land commitment of ~20.5km/847MW reactor at 85.9% capacity factor, or 25.4km using our assumptions here but excluding enrichment fuel and the Yucca Mountain exclusion zone. That's 9.8mi (29× Cravens's number), or, adjusted to 0.1%U ore, 16.1mi or 48× Cravens's claim. Another paper using the Spitzley & Keoleian data (R.I. McDonald et al., "Energy Sprawl or Energy Efficiency: Climate Policy Impacts on Natural Habitat for the United States of America," PLoSONE, 2009, www.plosone.org/article/info:doi/10.1371/journal.pone.0006802#pone.0006802-Spitzley2, cited in Alexander, supra note 7), expresses its nuclear land-use as 1.9-2.8km/TWh/y, or 5.8-8.5mi for our nominal 1GW plant, but shows no derivation, and I have not been able to reproduce its results from its stated sources.
21. W. Häfele et al., Energy in a Finite World, International Institute for Applied Systems Analysis (Laxenburg), 1977, & Ballinger (Cambridge MA), 1981, Vol. 1, p. 286, found that the total area disturbed by the LWR system is ~0.7mi for fixed facilities, plus ~0.5mi/y for the fuel cycle using 0.203%U ore, which would be ~1mi/y at the modern U.S. norm of 0.1%U ore. (I've adjusted the IIASA figures for the 14% lower uranium use per TWh in today's EPRs and for 90% nuclear capacity factor.) This implies ~41mi for the 1GW nuclear plant over its 40-y lifetime, which is 2.9 times my conservative estimate or 123× Cravens's claim.
22. V. Fthenakis and H.C. Kim, Land Use and Electricity Generation: A Life-Cycle Analysis, Renewable and Sustainable Energy Reviews 13(6-7):1465-1474 (2009), Fig. 1, assuming 50 percent underground and 50 percent openpit mining, 70 percent centrifuge and 30 percent gas-diffusion enrichment, and apparently counting all terms except disposal sites for low- and medium-level wastes, which neither they nor I can quantify from available data. Erroneously in my view, though, they count windpower area spread across, not occupied.
23. Ausubel's charming essay Renewable and Nuclear Heresies, Intl. J. Nuclear Governance, Economy & Ecology 1(3):229 (2007), claims energy sources that use material amounts of land are not green because some Greens think human land-use shouldn't increase. Its untransparent but clearly flawed analysis has been heavily criticized privately and publicly, e.g., www.newscientist.com/blog/environment/2007/07/just-how-much-land-does-solar-power.html.
24. According to the European Wind Energy Association's 2009 treatise The Economics of Wind Energy, 2009, at 48. The American Wind Energy Association at www.awea.org/faq/wwt_environment.html#How%20much%20land%20is%20needed%20for%20a%20utility-scale%20wind%20plant gives the older and more conservative figure "5% or less," and notes that the land the turbines spread across can decrease by up to 30× on a hilly ridgeline (from 60 to 2 nominal acres/peak MW), though some such sites may require maintained roads, taking back some of the turbine-spread land savings. In a 23 Sep. 2009 online Wall Street Journal letter, AWEA gives a 2-5% range and states that "for America to generate 20% of its electricity from wind, the amount of land actually used is about half the size of Anchorage, Alaska, or less than half the amount currently used for coal mining today." DOE/EPRI's 1997 data (ref. 6), reflecting early California practice before turbine layout was well understood, mentions 5-10%. J.G. McGowen & S.R. Connors' thorough "Windpower: A Turn of the Century Review," Ann. Rev. En. Envt. 25:147-197 (2000), at p. 166, give 3-5% for U.S. windfarms in the 1990s, but find 1% typical of U.K. and 1-3% of continental European practice, with "farm land...cultivated up to the base of the tower, and when access is needed for heavy equipment, temporary roads are placed over tilled soil." I consider 1-2% typical of modern practice where land is valued enough to use attentively.
25. Wind turbines on flat ground are typically spaced 5-10 diameters apart (e.g., in an array designed at 4×7 diameters) so they don't unduly disturb each other's windflow. (Spacing over water or on ridges is often much closer.) A typical modern wind turbine with its infrastructure has a nominal footprint of ~1/4 to 1/2 acre for roads, installation, and transformers (NREL, Power Technologies Energy Data Book, Wind Farm Area Calculator, www.nrel.gov/analysis/power_databook/calc_wind.php) and has a peak capacity ~2-5megawatts, hence an average capacity ~0.6-2megawatts. That's 0.2-2mi of actual equipment and infrastructure footprint to match a 1GW nuclear plant's annual output. As a more rigorous cross-check, a nominal 1.5MW, 77-m-diameter, 80-m-hub-height turbine in a Class ≥3 wind site would nominally be sited 6 turbines per km (Jacobson, supra note 4, at 17), so 667 of them would match the peak output and (at 35% wind versus 90% nuclear capacity factor) 1,715 would match the annual output of a 1GW nuclear plant. Including roads, 1,715 turbines would physically occupy a nominal 1-2% (EWEA, ref. 19) of the area they spread across, which is 1,715/6=286km or 110mi. That 1-2% occupied area is thus 2.9-5.7km or 1-2mi. Even in probably the highest official land-use estimate, which generously assumes about a thousand times the minimal physical footprint, the Bush Administration's 20% Wind Energy by 2030, at pp. 110-111, found that 305GW of U.S. windpower could disturb ~1,000-2,500km of land, or 1.3-3.2mi/installed GW, or at 35% capacity factor, 3.3-8.1mi/1-GW-reactor-equivalent - still 37-90 times lower than Ausubel's claim of 298mi.
26. With each 5-MW turbine at 35% capacity factor producing 1.75 average MW, 514 turbines would produce 900 average MW to match the 1GW nuclear plant. Each turbine has a direct footprint (foundation and tower) of ~20m, so 514 turbines directly occupy ~20×514=10,280m or ~0.004mi. We round up to 0.005 to allow for transformers; the cables are always underground. This footprint is normal for flat open sites not needing permanent roads.
27. In an average U.S. site, PVs spreading across 15mi, but not actually using much or most of it, would produce the same annual grid electricity as a 1GW nuclear plant from flat horizontal solar cells like the 19.3%-efficient Model 315 in SunPower's current catalog (that firm's prototypes in May 2008 also achieved 23.4%, heading for market ~2011-12). The math is simple. The U.S. receives annual-average, 24/7/365 sunlight of 1,800kWh/my (one-fifth of full equatorial sea-level noon irradiance), so a 19.3%-efficient module captures an average of 347kWh/my or 40 average WDC/m. AC output is nominally ~23% lower due to practical losses (dirt, fill fraction, wiring and conversion losses, mismatch, system availability, heat: http://rredc.nrel.gov/solar/codes_algs/PVWATTS/system.html), yielding 31 average WAC/m. Now derate generously by another 25%, to 23.1 average WAC/m, to allow ample access space for maintenance (possibly shared with other uses). Thus horizontal flat PVs spread across 3/4 of 900,000,000/23.1=39millionm or 15mi will produce 900 average MWAC in an average U.S. site. Tracking collectors could reduce the module area by ~25-36%, or southwestern Nevada siting by ~22%, or both; simply tilting up the panels at the local latitude saves ~16%, but some space is still needed between the panels for access, so for simplicity and conservatism I've used the horizontal model in this illustration. NREL (ref. 27) found that the most efficient packing of tilted 15%-efficient PV modules can spread across 10km/GWp, or 17.4mi to match the annual output of our nominal 1-GW nuclear plant; at our 19.3% efficiency that would be 13.5mi. In excellent agreement, CTO Tom Dinwoodie (personal communication, 2 Oct. 2009) confirms that in a typical U.S. site, SunPower's land-efficient one-axis/backtracking T0 tracker typically yields 0.3 capacity factor at 0.4 ground cover ratio (the ratio of panel area to total land area), so a nuclear-matching PV farm at 20% module efficiency and 80% DC/AC efficiency would spread across 17.8mi (or 5.9 if it matched the nuclear plant in capacity rather than in energy). Also consistent with these figures, J.A. Turner (NREL), Science 285:687-689 (30 July 1999), showed that 10%-efficient PVs occupying half of a 100×100-mile square in Nevada could produce all 1997 annual U.S. electricity. But the phrase "occupying half of" is conservative: PVs normally get mounted not on the ground but well above it, leaving the space between ground mounts available for other uses such as grazing. (The moving shade can reportedly benefit both grass and sheep.) Mounting poles punched into the ground can make actual land-use a very small fraction of the total site areas calculated here, and livestock graze right up to the poles. Two-axis trackers, though typically less cost-effective than one-axis, have an even smaller footprint because they're PVs-on-a-pole, analogous to wind turbines. For comparison, concentrating solar thermal power systems spread across roughly one-third more area than PVs for the same annual (but firm) output, and require cooling, though this can use dry towers. Other revealing land-use comparisons are at www.sourcewatch.org/index.php?title=Concentrating_solar_power_land_use.
28. According to Lawrence Berkeley National Lab's world-class roof expert Dr. Hashem Akbari (www.climatechange.ca.gov/events/2008_conference/presentations/2008-09-09/Hashem_Akbari.pdf), the world's dense cities occupy 1% of the earth's land area, or ~1.5trillionm. About one-fourth of that, or 0.38millionkm, is roofs. So ignoring all parking structures, and all smaller cities' or non-urban roofs, and assuming that just one-fourth of the big-city roof area has suitable orientation, pitch, shading, and freedom from obstructions, PVs just on the world's urban roofs could produce ~106PWh/y, or 5.8× global 2005 electricity use. (This assumes the same 75% module derating factor as before, and global-average horizontal surface irradiance of 170W/m (WEC, ref. 5, but most big cities are at relatively low latitudes with more sun.) Large land areas now occupied by old landfills and Superfund sites, or overwater, could also be covered with PVs without displacing any useful activity.
29. This old figure assumes 10% module efficiency. With the best 2011 modules in or entering production, the 7% figure would drop to roughly 3%.
30. NREL, PV FAQs: How Much Land Will PV Need to Supply our Electricity?, DOE/GO-102004-1835 (2004), at www.nrel.gov/docs/fy04osti/35097.pdf, italics in original.
31. Vestas, "Life cycle assessment of offshore and onshore sited wind power plants based on Vestas V90-3.0 MW turbines," Vestas Wind Systems A/S, 2006, www.vestas.com/Files/Filer/EN/Sustainability/LCA/LCAV90_juni_2006.pdf, assuming 105-m hub height onshore. See also www.vestas.com/en/about-vestas/principles/sustainability/wind-turbines-and-the-environment/life-cycle-assessment-(lca).aspx.
32. See also www.vestas.com/en/about-vestas/principles/sustainability/wind-turbines-and-the-environment/life-cycle-assessment-(lca).aspx.
33. E.g., Kim & Fthenakis, That article states that using U.S. average solar irradiance (1,800kWh/my) and a 30-y assumed life, the indirect land-use for PV balance-of-system is 7.5m/GWh, plus for the installed PV array itself, 18.4, 18, and 15m/GWh for multi-, mono-, and ribbon-Si. Scaled to 900 average MW for 40y, these would correspond respectively to 0.9, 2.2, 2.2, and 1.8mi. For comparison, that paper calculates 30-60-y direct land-use as 164-463m/GWh with optimal tilt but ~10% efficiency. These direct land-uses correspond to 20-56mi/900 average MW - higher than my ~10 because the paper assumes half my empirical array efficiency and uses layouts with severalfold less dense packing (id.; Ref. 6, p. 4-30). Their analysis confirms that PVs produce about two-fifths more electricity per unit of land (over 30 y at 13% efficiency and average U.S. irradiance) than typical U.S. coal-fired power plants do.