esm223_08_US and global energy overview Physics Today Jul-2004

Esm223_08_US and global energy overview Physics Today Jul-2004

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Unformatted text preview: Basic Choices and Constraints on Long-Term Energy Supplies Population growth and energy demand are exhausting the world’s fossil energy supplies, some on the timescale of a single human lifespan. Increasingly, sharing natural resources will require close international cooperation, peace, and security. Paul B. Weisz uman society, like any system composed of dynamic processes, depends on an external energy source. His- torically, that source was the Sun, which provides heat, light, and photosynthesis for food to support work energy by man and animal, and affects wind and water motion. Since the early 19th century, though, the discovery of and access to a vast supply of fossil fuels within Earth has en- abled the industrial revolution, near-exponential growth of population,1 technologies, and wealth. That period could well be renamed the energy revolution (see figure 1). As we enter a new millennium, we are growing in- creasingly concerned about the limits of our fossil fuels that are driving the world’s economies. Manyjournal arti— cles, committee reports, and books have addressed this “energy problem”; they contain opinions, ideas, and sug- gestions from experts within their various subdisciplines on possible ways to improve our practices or innovate tech- nologically. But a complex interdependence exists among the technological, social, and environmental aspects ofen— ergy use (see the articles in PHYSICS TODAY, April 2002). Furthermore, many of the ideas researchers propose can- not significantly impact the real magnitude of the energy problem or may provide only short-term relief. Our basic choices are limited. Nature’s energy re- sources are confined to two categories: Earth-stored fossil residues and nuclear isotopes, whose economic utility is limited by the finite amounts that exist on Earth, and the radiation flux of solar energy, whose economic utility is limited by the finite rate at which we can capture the Sun’s energy and by the land areas that societies can dedicate to harness it. The longevity of the fossil energy supply and the net rate of solar energy availability are both reduced by the energy consumed through their conversion to a suitable energy form and the technologies that accompany that con— version: storage, delivery, maintenance, and repair of en- vironmental damage. Solar-derived consumer energy, whether as electricity, biomass, or wind, represents a Paul B. Weisz is an emeritus professor of chemical and bioengi— neering at the University of Pennsylvania and a retired senior sci- entist and manager at the Central Research Laboratory of the Mobil Corp. He is also currently an adjunct professor of chemical engineering at the Pennsylvania State University. © 2004 American Institute at Physics, 3-0031-9228-0407-030-9 clean, alternative energy form. It is important to understand a basic law of nature: Energy, once used, is not re— generable. So the public term “renew- able energy” is misleading. The following analysis examines the magnitudes of the world’s energy supplies and the basic constraints on our ability to support in the long term society’s demands using those finite supplies. To put those magnitudes into a human context for policymakers and the public, the longevity of our resources will be expressed on the scale of a human lifespan (where 1 human lifespan is approxi- mately 75 years). Energy demands In viewing overall societal energy issues, it is useful to ex— press energy magnitudes in units of the quad (QJ, where 1 Q : 101‘5 BTU, roughly equal to 2.5 X 101‘I kcal or 1.06 X 10‘” joule. Current US energy consumption is about 100 Q/year, roughly a quarter of the world’s total demand.2 Energy demand by humanity continues to rise. An in— crease of about 1.5% per year is projected in the US and world demand is expected to increase by 1—2’%‘ per year for many decades, mainly due to continued population growth. While total demand is, of course, influenced by personal demand, even unusually large (20%, say) conser- vation efforts would be nullified by population growth in less than 20 years. Earth-stored resources ) Petroleum. In 1956, petroleum geologist M. King Hub- bert correctly predicted that a peak and subsequent drop in US production would occur around 1970.“ In fact, for— eign imports have since risen to 60% of current consump- tion. US dependence on foreign petroleum is certain to increase. In 2000, Jay Hakes of the Energy Information Ad— ministration presented a similar and extensive US De— partment of Energy assessment of the likely trend and peak in the world petroleum supply.” Figure 2 shows the predicted range of years when the peak is likely to occur for demand whose growth rate may be between 0—2%. Be— cause growth rates due to population alone are anticipated to be at least 1% per year for many decades to come, the pivotal event is expected to occur well within a human lifespan. Moreover, the analysis was based on an opti— mistic estimate of the world oil resource of approximately 2200—3900 billion barrels, nearly twice the proven re- serve.i That would place the anticipated time to reach the peak well within a few decades. > Natural gas. A natural gas shortage exists now in the US. Yet the current growth rate of US demand is ap— proaching 3% per year.” As seen in figure 3, the proven July 2004 Physics Today 47 9 5 Ener 8 revolu ion 5 7 E 6 E 5 B 4 o (34 3 m E 2 o B 1 0 1200 1300 1400 1500 1600 1700 1800 1900 YEAR Figure 1. World population growth since the 13th century. US natural gas reserve would last very few years, even at constant (year 2000) demand. Estimated gas reserves worldwide are relatively large. Geologists have good reasons to believe the sum of our reserves and still undiscovered (but likely to exist) nat- ural gas could last roughly for another 45—60 years (see figure 3).“ However, those reserves are widely scattered around the world: 58% are reported to be located in Rus— sia, Iran, and Qatar, with small contributions in numer- ous other countries2 Clearly, their use will depend on vast international and intercontinental transportation by pipelines, transoceanic shipment as liquefied natural gas (LNG), or advance conversion to liquid fuels. Energy sac- rifice by basic thermodynamic requirements plus process efficiency loss will accompany advance conversion to liq— uid fuels. Geopolitics] cooperation will be essential. D Goal. The largest fossil fuel resource available in the US is coal. The energy content of the current US reserve is about 5667 Q. If demand remains frozen at the current rate of consumption, the coal reserve will indeed last roughly 250 years.2 That prediction assumes equal use of all grades of coal, from anthracite t0 lignite. Population growth alone reduces the calculated lifetime to some 90—120 years (see figure 4). Any new uses of coal would further reduce the supply. The Fischer—Tropsch process has been used to convert coal to gasoline motor fuel in South Africa for decades, for ex- ample. The process requires that one carbon atom of coal be sacrificed to generate at least two hydrogen atoms, and it takes energy to decompose water to make that hydro— gen. As a result, the process consumes 2 Q of coal to gen- erate 1 Q of motor fuel. Hydrogen production would re- quire an even greater consumption of coal. The use of coal for conversion to other fuels would quickly reduce the life— time of the US coal base to less than a human lifespan (see figure 4). High carbon dioxide emissions also accompany the conversion of coal to any motor fuel. For more details on how C02 complicates the energy problem, see the box on page 50. > Dilute fossil residues. Oil shale, or bitumen, is sed- imentary rock containing dilute amounts of “heavy oil” or near—solid carbonaceous residues. The US has negligible amounts of that resource. Worldwide estimates of the 48 July 2004 Physics Today total energy contents are large but highly speculative?“7 To harvest the dilute solid carbonaceous contents requires drastic measures: Either underground combustion, heating, steam, or air to drive the carbonaceous solids to- ward the surface, or the mining of huge vol- umes of solids using heat, solvents, and steam to extract the resource. The extracts must be further processed to yield usable hydrocarbon fuels, 3 process that requires further energy sacrifices. Compared to pe— troleum, these heavy oils present additional refining and environmental problems be— cause of the abundance of nitrogen, oxygen, and metal compounds found in them. Also, the amount of CO2 released during process- ing and use greatly exceeds that released by the current use of petroleum fuels. Nuclear energy. Uranium fission plants in the US are presently supplying less than 8% of our total energy demand. Were the current nuclear technology ex- panded to provide the electricity now sup— plied by coal (about 23 Q), the estimated US uranium resources2 would be exhausted in about 35~58 years—less than a human lifespan. 2000 Constraints on solar energy use The amount of solar energy received across US latitudes is approximately 22 Q per year per 4000 km?‘ (about a mil- lion acres) on average? Technologies based on this re- source have the potential to become major contributors to our energy supplies (see Sam Baldwin’s article in PHYSICS TODAY, April 2002, page 62.) Photovoltaic solar cells convert 10—20% of incident ra- diation directly to electricity. Figure 5 illustrates how large a surface area of cells would be required to generate a par— 19 GROWTH IN DEMAND (per year) l—‘ e“ 0% 2000 2020 2040 2060 2080 2100 YEAR OF PEAK WORLD OIL PRODUCTION l—l—_l—I Human lifespan 0.5 1.0 1.5 Figure 2. Predictions indicate that the peak and subsequent decline in world oil production will probably occur within the next few decades. The data here are based on optimistic estimates that place the oil reserve at 2248—3896 billion bar— reis. Just how soon the peak will occur depends on annual population growth rates and increases in demand. The given ranges account for uncertainty in predicting the future: For each estimate of projected growth in demand for petro— leum—O, 1%, or 2%—there exists a 95% chance that the peak will occur by the year on the left—hand end of the range and a 5% chance that it may occur as late as the year on the right-hand end. (Data from ref. 4.) http://www.physicstodaycrg Figure 3. Outlook for world and US natural gas capacity, based on current proven gas reserves and on currently estimated resources (including unproven and nonpro— duceable amounts). The energy content is given to the right of each bar, the length of which in- dicates the amount of time that the natural gas supply is likely to last. That longevity depends on the annual growth in usage (shown on the far right) that may occur over the next few decades. (Based on data from ref. 6, and ref. 2, Energy Information Admin— istration International Energy Out— look 2004.) WORLD Estimated NATURAL GAS RESOURCES 10 20 0 ticular amount of electricity. The yellow region indicates electricity produced directly at the cell. The blue region is a more realistic mapping and indicates the larger cell areas needed to cover the energy losses in transformers, transmission, power-equalization over time, and efficiency losses that occur for any conversion to gaseous or liquid fuels. Thus about 40—80 thousand ka of area—roughly 2—4 times the size of Massachusetts—could supply about 20 Q, or 20—25%, of today’s US total energy requirements. That amount and more of available land can probably be found in the US. But the size illustrates the magnitude of the technological and social impact. It is instructive to compare what fraction of other nations’ total areas would be required to supply their current energy demand. The percentage ranges from as low as 0.2% for Australia to as much as 24% ofthe land occupied by Belgium (see the table on page 51). The data assume a 15% solar-cell efficiency, and 50% efficiency at the site of consumption. Biomass energy production requires photosynthesis exclusively on fertile land, but it is another much dis— cussed alternative energy. The US has about 1.6 million km3 (400 million acres) of arable land that provides food CURRENT USE l. . : 1 E L, 1.1 % growth 57% _ E :1, 2.0 % growth n—‘l <1 0 a AFTER CONVERSION D 1.1 0/1. growth 2.0 % growth l—l—l—'_'—l—l—l— 0 50 100 150 200 TIME (years) r—I—fi—l— O 1.0 2.0 TIME (lifespan) http://www.physicstodayorg 183 quads 10 400 quads 2.0% growth 7 5500 quads 2.8% growth 1400 quads 2.8% growth g No growth % 30 40 50 60 70 80 90 100 TIME (years) l—T'_*— 0.5 TIME (lifespan) 1.0 for the current US population, with about 20% of the food left for export. The US is likely to progressively need that 20% in the next few decades as its population increases. Moreover, the current agricultural productivity depends on fossil fuels to provide the reactive nitrogen required to make fertilizer. Otherwise, about three to four times that 1.6 million km2 of arable land will be needed to provide photosynthetic nitrogen fixation to generate the current food supplies. Quite apart from fertile land requirements, the solar- to»biomass conversion efficiency is very much smaller than for the conversion of solar to electrical energy. Modern agriculture can generate about 1—1.5 million kg of biomass vegetation per square kilometer of land with about 16 000 BTU per kg, for a total of about 0.06—0.09 Q on 4000 km2 of land. However, after accounting for external energy con- sumed through the agricultural process and the conver- sion of biomass to a useful fuel, the net energy production, ifany, is less than 0.02 Q on 4000 ka—two orders of mag— nitude smaller than that of photovoltaic cell conversion. That is, biomass conversion would require some IOU-fold more area of fertile land. No growth Figure 4. Outlook for the longevity of the US coal supply, based on the current consumption rate and a range of anticipated annual growth ratesiup to a 2% increase in de- mand per year, The two lowest bars indicate the longevity of the Coal supply if coal is converted to other fuels. Experts estimate that roughly 54% of the reserve underground— comprising anthracite, bituminous, subbituminous, and lignite rock— is recoverable. (Data from ref. 2, Annual Energy Review 1999.) 250 3.0 July 2004 Physics Today 49 Basic Problems Associated with Carbon Dioxide Emissions The massive quantities of carbon dioxide currently generated during fossil fuel consumption are responsible for progressive global warming. This problem has become a matter of global concern and has led to large efforts and expenditures for re— search in technologies designed to sequester C02.” Unfortunately, permanent immobilization confronts fun- damental problems. Like HZO, CO2 is a chemically inert molecule. Its only potential reaction partners possibly avail- able in sufficient magnitudes may be mineral oxideswfor example, calcium— and magnesium-silicates. They exist in dense geological formations. However, no useful reaction rate is achievable in such locations. Their use would require mining, shipping, grinding, special activation processing,” and disposal of gigatons of the solids. Most prominent research projects are directed toward massive physical storage of CO2 by injection into those ge— ological formations or within the deep oceans (see Jorge L. Wind energy is another secondary product of solar ra- diation. Although few studies have assessed its ultimate technological promise, researchers estimate that the tech- nology could potentially generate a maximum of 3—22 Q of electricity in the US.“ Energy losses due to transmission, supply, and demand fluctuation or conversion to other en— ergies will reduce the actual contribution, but wind energy provides a significant potential resource contribution. Hydrogen fuel from solar—cell electricity would be free of CO2 emissions, but the “hydrogen economy” would de- pend on vast land areas as illustrated by the yellow band in figure 5. In addition to energy losses during conversion to hydrogen, energy losses will occur in the creation and operation of a vast new infrastructure designed to store, ship, distribute, and handle huge amounts of hydrogen at all levels, from manufacture to uses. In a recent analysis, Reuel Shinnar‘” of the City College of New York noted that the enormous effort to alter our infrastructure to create a hydro— gen economy argues strongly for the direct automotive use of electricity itself, for which much of the infrastructure and po- tential technology are at band. 100 Energy science Energy availability determines, drives, limits, and shapes the working capability of all processes of society." The silent and plentiful gift ofenergy has fundamentally U! O 03 O N.) O H 0 Figure 5. Photovoltaic cell areas required to generate electrical energy that could supply a sizable fraction of the US economy. The yellow area plots the electrical energy pro— duced at the solar cell surface for efficiencies between 10 and 20%. The blue area plots ENERGY DEMAND (quad) the energy at the consumer side and ac- 3 counts for losses in transmission, storage, and so forth, in addition to efficiency losses. 2 Some US states (Delaware, Massachusetts, 5 Indiana, Idaho, Arkansas, and California) and world nations provide the scale of the enor— mous land areas that would he required. countries; US states: DE Sarmiento and Nicolas Gruber’s article in PHYSICS TODAY, August 2002, page 30). It is difficult to accurately predict the integrity of such physical storage over long periods") be- cause many variables in complex environments are in- volved. Attempts to manipulate marine or terrestrial ecosys- tems and increase the amounts of C03 these sinks naturally hold are fraught with great complexities that involve multi— ple and interactive processes.” Any conversion of a carbonaceous fossil fuel to a fuel of lower carbon content—including the conversion all the way to hydrogen—will eject the excess carbon as C01. The problem of its emission to the atmosphere is simply trans‘ ferred from the points of consumption to the location where the conversion process takes place. Therefore, the CO_, problem is not eliminated by a "hydrogen economy" if the hydrogen is created by the conversion of coal, petroleum, or natural gas. influenced the application of economic theory as well as the teachings of most other disciplines in the educational system. > Economics. In the 19705, Nicholas Georgescu—Roe— gen” tried to demonstrate the actual relationship between economics and thermodynamics, the basic physics of en- ergy. He observed that most economists believe that “the economic process can go on, even grow, without being con- tinuously fed low entropy,” which in a thermodynamics context means “without receiving new energy.” As we ap- proach the limits of our easy access to energy, the defining economic currency will be dominated by availability of en- ergy units rather than by an artificial currency, be that gold or dollars. This change in economic theory is well illustrated by the silicon photovoltaic cells that brilliantly accomplished CELL EFFICIENCY 20% 10%20’32' 100} US total consti'fher US transportation US petroleum imports ' 10 20 30 50 100 200 400 ‘AREAtx 103 king); . g . MA 4 IN ID4 AmCA BELGIUM UK GERMANY 50 July 2004 PhysicsToday http://www.physicstoday.org their mission in space flight in 1972 at an afford- able economic cost. Yet, if they had to provide us with indispensable alternative energy, they would have had to operate continuously for at least 20 Energy consumed Approximate years just to replace the energy invested (or con Per Rafi Land area 9013‘” cellar“ “eedEd sumed) in their production. By 1999, photovoltaic 10" 103 kmz 10:: km: %ofland cells were reported to produce their investment en- peop q ergy in about 3_7 yearsnu US 0.36 100 9 591 263 2.7 I That history illustrates the profound economic Belgium 027 2.7 30 7 24.0 importance of the concept of net energy. The eco- I nomic value of an alternative energy technology de- Austral“ 0-19 4-8 7 580 13 0-3 pends on the net rate of energy QNE it will deliver Russia 017 26 15 981 69 0.4 after the rate of energy production QPR is debited by the energy consumed for its operation Qop and Japan 0-17 21-8 372 58 15-4 tthe eiiilergy invested in its creation E during its life- Germany 017 14 356 37 10.3 lme 2 UK 0.17 10 243 26 10.8 QNE : an _ (Qor + E/T)- I _ France 0.17 10 546 26 5.0 For example, ethanol productlon from biomass, _ which involves a complex agricultural and indus- Bram 0-05 3'6 3456 23 0'3 trial processing system that requires large and di- China 003 32 9 377 84 09 verse external energy inputs QOP, easfly results in a Egypt 003 2.0 996 5 0.5 negative QNE, yet government subsidies can make the production profitable to producers. > Education. The educational system has become focused on how to manage, produce, distribute, and enjoy the objects, services, and pleasures that plen- tiful energy makes possible. That system has grown into ever more disciplines and subdisciplines that serve ever more specialized skills. Dedication to basic sci- ence—that is, to the laws of nature that allow, control, and constrain all abilities and potentials—is no longer empha- sized. Basic science remains limited largely to recitation of formalisms that are gladly forgotten after examination time because little effort is made to relate their basic and universal relevance to specialties, the totality of life, and society. More than ever since the beginning of the energy rev- olution, knowledge of the basic nature and limits of en— ergy is needed to realistically determine and carry out ef— fective policy designed to guarantee reliable energies in the future. That could well help ensure the survival of civilization. As H. G. Wells once remarked, “Human his- tory more and more becomes a race between education and catastrophe.” A knife-edge issue The major source of the world’s energy supply, the fossil fuels, will decline in availability within several decades. It is of paramount importance that the public and policy- makers recognize the ensuing shortages and the urgent need for policies that will address them. In particular, an urgent commitment to solar and nuclear energy technolo~ gies appears to be mandatory for the long term. Solar energy technology offers the most promising ca- pabilities for the future because photovoltaic cells can gen- erate potentially large quantities of electricity for nations with sufficient land area. Worldwide use, though, will de— pend on international peace and cooperation. Current uranium fission technologies could provide enough energy for a few decades.” Advanced fission tech- nologies that involve breeder methodologies and the use of thorium, as envisioned by Edward Teller,” could extend that timeline to many hundreds of years. Controlled nu— clear fusion remains a unique energy alternative of vast magnitude. Moreover, nuclear technologies are not de- pendent on location and land area. At the moment, public concern over potential risks has virtually stopped the pur- suit of this energy source. http://www.physicstoday.org *Data from Department of Energy/Energy Information Administration International Energy Annual 1999. Solar Cell Area Requirements to Meet Energy Demand in Select Countries Peaceful cooperation among nations will be increas- ingly and vitally important for accessing and sharing our remaining resources. Human society faces no greater risk, however, than ignorance of the basic laws of nature, the role and finite magnitudes of energy sources, the arithmetic of population growth (see Albert A. Bartlett’s article in this issue on page 53), and their consequences on the survival of humanity. As Shirley Ann Jackson, president of the American Association for the Advance- ment of Science, points out (see APS News, October 2003, page 8), “The public policy arena needs the voice of sci- ence itself . . . weighing in on knife-edge issues with the voice of reason.” I acknowledge the tireless assistance of David. Pimentel, pro- fessor of agricultural sciences at Cornell University, for advice on agricultural science; its role in food production, land use, and biomass production; and their relevance to energy issues. References 1. United Nations statistics available at http://wwwunnrg/esa/ population/publications/sixbillion/sixbilpart1.pdf. 2. Energy Information Administration, Annual Energy Outlook 2004, rep. no. DOE/EIA-0383(2004), available at http:// www.eia.doe.gov/oiaf/aeo; International Energy Outlook 2004 rep. no. DOE/EIA-0484(2004), available at http://www. eia.doe.gov/oiaf/ieo; Annual Energy Review 1999, rep. no. DOE/EIA-0384l99) (2000), available at http://tonto. eia.doe.gov/ftproot/multifuel/038499.pdf. 3. M, K. Hubbert, in Drilling and Production Practice, Ameri- can Petroleum Institute, Washington, DC (1956); M. K. Hub- bert, Am. Assoc. Pet. Geol. Bull. 51, 2207 (1967). 4. J. Hakes, Long Term World Oil Supply, presentation at the 18 April 2000 meeting of the American Association of Petro— leum Geologists, New Orleans, LA, available at http:l/www.eia.doe.gov/pub/oil_gas/petroleum/presenta- tions/2000/long_term_supply. 5. Table 8.1 World Crude Oil and Natural Gas Reserves, 1 Jan— uary 2003, Energy Information Administration/Department of Energy update posted on 8 March 2004 for International Energy Annual 2002, available at http://www.eia.doe.gov/ pub/international/iea2002/table81.xls 6. National Petroleum Council Committee on Natural Gas, July 2004 PhysicsToday 51 10. 11. 12. 13. 14. 15. 16. 17. 18. Naliiral Gas: Meeting the Challenges oftlie Nation’s Growing Natural Gas Demand, v01. 1, National Petroleum Council, Washington, DC (1999). W. Youngquist, Shale Oil: The Elusive Energy, newsletter 110. 98/4, M. King Hubbert Center for Petroleum Supply Studies, Golden, CO (1998). W. E. Reil'snyder, H. W. Lull, Radiant Energy in Relation to Forests, US Dept. ongriculture, Forest Service, Washington, DC (1965); E. P. Odum, Fundamentals of'Eeology, 3rd ed,, W. B. Saunders, Philadelphia (1971); M. Slesser, C. Lewis, Biologiml Energy Resources, Wiley, New York (1979); S. B. Weiss, Can. J. Forest Res, 30, 1953 (2000). D. Pimental et al., BioScience 52, 1111 (2002); EIA Monthly Energy Review, DOE/EIA—0035(95/02), Washington, DC (February 1995). R. Shinnar, Tee/Incl. in Soc. 25, 455 (2002), P. B. Weisz, in Chemical Engineering in a Changing World, W. T. Koetsier, ed., Elsevier Scientific, New York (1976). N. Georgescu-Roegen, The Entropy Law and the Economic Process, Harvard U. Press, Cambridge, MA(1971). R. Corkish, Sol. Pi‘og. 18, 16 (1997). The Future of Nuclear Power: An Interdisciplinmy MIT Study (2003), available at http://web.mit.edu./nuclearpower. E. Teller, Memoirs-1A fluentieterentury Journey in Science and Politics, Perseus, Cambridge, MA (2001), p. 565. US Department of Energy, Office of Fossil Energy, Carbon Sequesi‘mi‘ion Research and Development, (December 1999), available at l1ttp://www.fossil.energy.gov/programs/ sequestrationfpublications/ 1999,1'dreport/frontjeh.pdf. M. M. Maroto-Valer et 3]., Am. Chem. Soc. Div. Fuel Chem. 49, 373 (2004). K. L. Griffin, J. R. Seemann, Chem. Biol. 3, 245 (1996); H. E]- dcrfield, Science 296. 1618 (2002). I ...
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