high-temperature superconductors and co2 emissions

Energy Vol. 14, No. 6, pp. 309-322, 1989 Printed in Great Britain. All rights reserved

0360-S442/89 $3.00 + 0.00 Copyright 0 1989 Pergamon Press plc

HIGH-TEMPERATURE SUPERCONDUCTORS AND Co2 EMISSIONS

A. B. CAMBEL + George Washington University, Washington, D C 20052, U.S.A.

and

F. A. KOOMANOFP Office of Basic Energy Sciences,

U.S. Department of Energy, Washington, D C 20552, U.S.A.

(Received 26 October 1988)

Abstract--High-temperature superconducting materials have potential to mitigate CO2 emissions into the atmosphere, particularly in central electricity generation, which is the major source of these CO2 emissions (followed by the transportation and manufacturing sectors). High temperature superconductors (HTSCs) could provide improved efficiencies to sectors reliant on central electric power. For the U.S., the potential reductions of CO2 emissions through HTSCs could amount to 1.48 trillion Ibs per annum, or 14.9% based on 1985 energy consumption figures. Worldwide CO2 emissions could be reduced by 3.92 trillion lbs.

INTRODUCTION

In 1986, Bednorz and Muller published their pivotal paper’ (for which they received the 1987 Nobel prize in physics) describing how certain ceramic oxides exhibit superconductivity at 3OK. This finding, together with the recent discovery by Chu and Wu that superconductivity can be achieved at temperatures above that of liquid nitrogen (77K), vastly enhances the opportunities for achieving superconductivity at high temperatures. Whereas previously only 600 elements and compounds were known to be superconductive, about 6,000 elements, alloys, compounds, organ& polymers, and ceramics are expected to be high-temperature superconductors (HTSCS).~

The technological significance of two key characteristics of superconductivity, its negligible electrical resistance and its ability to expel magnetic fields (the Meissner effect), have long been recognized.3 In fact, traditional superconductors (those operated at liquid helium temperatures of 4.2K) are used today in high-energy physics research, controlled thermonuclear fusion and magnetohydrodynamic power research, supercomputers, magnetic resonance imaging equipment for medical diagnostics, and magnetically levitated trains. In general, however, the temperature limitations associated with superconductivity have made widespread applications economically unfeasible. The potential offered by HTSCs has thus reawakened world interest in superconductivity.

Ideally, one would want materials that are superconducting at room temperature and even above. However, much can be achieved with superconductors operating at liquid nitrogen temperatures, once the technology is developed and made economically feasible. The advantages of using liquid nitrogen as a cryogen, instead of the more traditional liquid helium, are many. With respect to equipment and instrumentation, it is easier to work at liquid nitrogen temperatures than at liquid helium temperatures. Equipment such as the cryogenic system is easier to design and to

t To whom all correspondence should be addressed.

309 EGY 14:6-.4

310 A.B. CAMBEL~~~ F. A. KOOMANOFF

construct. Operation also requires less sophistication. From an economic standpoint liquid nitrogen costs considerably less than liquid helium. Further, as Kirtley4 has shown, the energy required to maintain the requisite refrigeration for the liquid nitrogen is approximately l-2% of that required for liquid helium.

In addition to their extensive direct technological and cost benefits, HTSCs may have an indirect, positive effect on the environment. Specifically, HTSCs may be helpful in reducing CO2 emissions and thereby alleviating the potential consequences of the greenhouse effect, including the anticipated rise in atmospheric temperature. The greatest opportunity for reducing such emissions is in the electric utility industry.

Superconductivity in general, and HTSCs in particular, may be highly beneficial to the electric utility industry. With this technology, electric generators and motors may be more efficient, transformers may need less cooling, and the electric losses in transmission and distribution lines may be minim&d. Further, energy may be stored in electrical form in superconducting magnetic energy storage systems. The benefits of superconductivity may be increased in the future in high-technology applications (computers, telecommunications, robotics, etc.) that rely heavily on electricity.

Here, we explore how and to what extent HTSCs may lead to reductions in CO2 emissions from electric utility power plants which burn coal, oil, or gas. Basically, these emissions can be decreased through conservation on both the power supply and power demand sides. By their very nature, HTSCs promote conservation directly and indirectly and can thus reduce CO2 emissions.

Note that considerable R&D work remains to be done before the opportunities for HTSCs discussed here become feasible technologically and commercially. For example, specific technological issues requiring resolution include the structural integrity of superconducting wires and films, satisfactory life economical manufacturing techniques, and achieving current densities of the order lo4 amps/cm’ to 16 amps/cm2. In the U.S., these efforts are being encouraged under President Reagan’s “superconductivity initiative,” begun in July 1987.

GENERATION OF ELECTRICITY

Worldwide electricity consumption continues to increase (Fig. 1). Between 1960 and 1985, electricity energy production in the U.S. went up by 227%. Worldwide, this increase was 267%. The largest growth (4297) o was in Eastern Bloc countries which included the U.S.S.R. Comparable growth over this period in the O.E.C.D. countries (mcluding the U.S.) was 243%.

Countries derive their electricity from several primary energy sources, including fossil fuels (coal, oil, gas), fissile fuels, and hydraulic energy. Approximately two-thirds of all the electricity generated in the world comes from fossil fuels; these also account for about three-quarters of all U.S. primary energy sources. Fig. 2 shows limited data on the percentage of fossil fuels used in electrical energy generation. As can be seen in Fig. 3, among the four major energy economic sectors, electric utilities consumed the largest amount of fossil fuel energy. In economic terms, total U.S. sales of electricity derived from fossil fuels amounted to approximately $16~10~.

Among the fossil fuels, coal use is increasing significantly in the U.S. over time (see Fig. 4). This is of consequence because, on a unit-ener p basis, coal produces more CO2 than does either oil or gas. SpeciBcally, Albanese and Steinberg have determined that coal produces 0.204 lb Co2/l,OIM Btu, while fuel oil and natural gas produce 0.16 and 0.115 lb COz/l,OOO Btu, respectively. In the U.S. at least, this increase in coal usage will continue in the foreseeable future for several reasons: (a) sites for hydroelectric plants are limited, (b) nuclear installations are not presently on the ascendancy, and (c) prevailing policies encourage the use of coal in electricity generation.

High-temperature superconductors and CO, emissions 311

1000

0

- Ea. ~,~k ,...‘.

. . . . . . ‘.’ ----- “.S.

. . . . ../

....’ O.E.C.D. ,....’

,...

- ,....’ ,...:

_______--- ____- --

________------

- __________------

1870 1075 1980 lSS5

Fig. 1. Electricty production from l!ZCl to 1985 in the O.E.C.D., the East Block countries, and the U.S.

Pnunt

- U.S.

---- World

Fig. 2. Percentage of electricity generated from fossil fuels. (Sources: E.I.A. and U.N.)

312 A. B. CAMBEL and F. A. KOOMANOFF

Fig. 3.1985 U.S. fossil fuel usage by sector.

BillIon kWh

1500

i

,*--_

_____.----- __-- _’

1000 _ ._’

___--- _ -’ _______e---

Transportation

Industry

- Total

Hydra

----- Nuclear

Gao

- Petroleum

Fig. 4. U.S. electricity generation.


CO2 EMISSIONS

Co2 is emitted into the atmosphere whenever carbon-containing compounds--i.e., all fossil fuels, including coal, oil, and natural gas--are oxidized. In 1985, world CO2 emissions amounted to 26.5 trillion lbs, while U.S. emissions were approximately 10.0 trillion lbs (Fig. 5). Each of the major energy economic sectors (industry, transportation, residential/commercial, and electric utility) contributes differently to CO2 emissions (Figs. 6 and 7); however, when all fossil fuels are combined, the electric utility industry is the major contributor to CO2 emissions, with the transportation sector following close behind (Fig. 8). While the energy sector generally enjoys considerable inter-fuel substitutionality, it has been shown6 that there is little such flexibility in the transportation sector, particularly in air transportation. In Fig. 9, it may be seen how the diierent modes of transportation contribute to CO2 emissions in the U. S. where rail transportation plays a relatively small role.

It should be noted that CO2 production and fuel consumption do not follow the same order in the four sectors of the energy economy (Table 1).

Table 1. Relative rankings of CO2 sources.

Sector

Utilities

Transportation

Industry

Residential/ Commercial

Total Energy Fossil Fuel co2

Consumption Consumption Emissions

3 2 1

4 1 2

1 3 3

2 4 4

Trillion Ibs.

World USA

Fig. S. 1985 CO2 emissions.


lJIllHl.s

IndustIy

Rmld.ntlau comm.nW

Total

Fig. 6. Amount of 1985 U.S. CO2 emissions by sectors and fuels used.

Trillim lb.

Industry

Fig. 7. Amount of 1985 U.S. CO2 emissions by sector.

High-temperature superconductors and CO, emissions

Fig. 8. Proportional 1985 U.S. CO2 emissions by sector.

Billions of tons

aom

2500

2uoo

1500

loo0

500

0

i

L

315

Fig. 9.1985 U.S. Cm emissions generated in the transportation sector.

316 A.B. CAMBEL~~~ F. A. KOOMANOFF

THE EFFECT OF ATMOSPHERIC TEMPERATURE ON Co;! EMISSIONS

The greenhouse effect, with its potentially higher atmospheric temperatures, could place an extra demand on existing electric energy-generation capacity. This demand can be estimated using changes in the available energy as prescribed by the second law of thermodynamics.’ Only a fraction of the energy supplied to the system Qs is available to do useful work. The maximum available energy to do useful work Qa is given by the Carnot Limit as: Qa = Q,[l-(Tu/T$], where To and TH denote, respectively, the ambient environmental temperature and the system operating temperature. As the ambient temperature increases, the thermal energy available for electricity generation must decrease.

Increases in the atmospheric temperature caused by the greenhouse effect will be reflected in To. Currently estimates of these increases range from 0.5 to 7C; however, we shall assume a conservative temperature rise of 2C. Further, we take TH =54OC as a representative plant operating temperature and set To = 25C, the customary standard temperature. From the Carnot limit, it is found that a 2-degree rise in temperature causes the available energy to be reduced by 0.4%. This in itself does not appear to be a significant figure. However, if we consider that in 1985, the U.S. alone generated nearly 2,178 biion kWh of electricity from fossil fuels, this 0.4% energy supply reduction becomes a highly significant 9.88 billion kWh nationwide. In other words, for a 2C rise in environmental temperature, an additional 9.88 billion kWh of energy would need to be generated to meet existing U.S. demand. If generation is accomplished with fossil-fuel-burning plants, an additional 45.4 billion lbs of CO2 per annum would be emitted in the U.S. alone, and 120.3 billion lbs worldwide. This in turn would exacerbate the greenhouse effect, and the atmospheric temperature could rise further. Consequently, air conditioning demand would rise, CO2 increasing the demand for electricity and causing higher CO2 emissions.

Incorporating HTSCs into the overall central electric system could counterbalance the projected increase in COZ emissions. However, application of HTSC technologies will not prevent the availability loss caused by the rise in atmospheric temperature. Availability loss is strictly thermodynamic in nature and as such is not directly affected by superconductivity. Inasmuch as superconductivity would reduce electric losses in the system, however, the demand for electrical energy would be lowered, and consequently, CO2 emissions would not be as high as they might otherwise be. In turn, the increase of the atmospheric temperature rise would also be less.

Note that atmospheric temperature will not rise quickly so that the loss in availability (and the concomitant added capacity cost) would not suddenly and simply appear. Added capacity probably would be absorbed in new capacity addition caused by increasing electricity demand; thus, it would not be noticed explicitly. Nevertheless, rising atmospheric temperature does have an associated lost opportunity cost which must be considered.

REDUCING LOSSES IN POWER GENERATION

To appreciate how superconductivity might reduce losses in electricity generation and transmission, it is convenient to divide the system into the following subsystems: (a) the thermal plant, including the boiler-superheater; (b) the turbo-generator; (c) the auxiliary equipment, such as motors, pumps, and control equipment; and (d) the transmission and distribution subsystem, including the transformers.

Elect& generators

In the overall electric utility system, the electric generators are the most efficient subsystem with efficiencies of well over 90%; 98% is not unusual. Accordingly, there is relatively little room for improvement. Given the large volume of such subsystems now in use, however, the total savings due to even a small percentage improvement could be quite significant.


Superconductors improve on generator performance because (a) there is negligible Ohmic dissipation and (b) they can produce high current densities and flux densities. Although generator losses are reduced significantly, overall system savings are lessened because the cryogenic equipment requires energy.

Prior to the discovery of HTSCs, experimental superconducting generators using liquid helium were built. Thullen’ has reported on a 45KVA prototype generator which was tested successfully without fundamental problems. A 300-MVA generator with a Nb-Ti field at liquid helium temperatures has been tested in the U.S.S.R. It was operated for about 12 hours with a 0.7% improvement in efficiency.

In a recent comparative analysis of 300-MVA generators, Kirtley4 has shown that any kind of superconductor will raise generator efficiency. HTSC generators, however, show slightly higher efficiencies because they do not have as stringent a cryogenic requirement as do conventional superconductors operating at liquid helium temperatures. The difference between conventional and high-temperature superconductors in total improved efficiency is approximately 1.1%. This could result in a reduction of 110 biion lbs of CO2 per annum in the U.S. based on 1985 figures. Worldwide, the corresponding figure would be 291.5 biion lbs.

Transmission lines

The electric power generated in utility plants is conveyed to the end user first by transmission lines and then locally through distribution lines. The overall transmission/distribution system also includes a variety of transformers. All three of these components suffer significant electrical losses; HTSCs consequently could play a vital role when technologically developed.

Line ? losses are of sufficient magnitude to necessitate an increase in generating capacity to continue to meet the same end user demand. Line losses depend on a number of factors (e.g., voltage, power carried, and design configuration); thus, HTSC contribution to line loss reduction is highly situation-specific and not possible to evaluate precisely here. In general, overhead long-distance lines experience a loss of approximately 1% per 100 miles. Total loss depends on the particular system and may vary quite widely: reported line power losses vary from 5%-20%. Annual transmission losses over the national grid amount to about 1,015 Btu.’

HTSC use seems best suited to underground transmission, because the lines would not be suspended but laid comfortably within conduits, thus minGzing structural requirements. These conduits could further constitute the Dewar casing so that superconductivity might have a role even at liquid nitrogen temperatures. Indeed, superconducting power transmission was considered even before the discovery of HTSCs.”

While high temperature superconductivity should work with AC, certain engineering problems will have to be overcome. Because most research in superconductivity is conducted with DC, it is not clear if constantly varying current will lead to energy dissipation. Changing over to DC lines would, under ideal conditions, cause no losses, but given the quantity of already-installed AC equipment, this would be a costly undertaking.

Reducing CO2 emissions by applying HTSCs in transmission and distribution systems involves numerous variables and cannot be evaluated accurately at this time. Accordingly, we assume a conservative estimate at the lower end of the line-loss range, i.e., 5%. Based on the power generated in the U.S. during 1985 in fossil-fuel-burning plants, HTSCs could reduce CO2 emissions by.500 billion lbs per annum.

Electicity storage

Electric utility demand load fluctuates over time, typically during the 24hour day, over the 7-day week, and by season. By law, utilities must provide the electricity demanded by customers within

-t- For expository convenience an unless otherwise stated, we use line generically to include transmission and distribution lines, as well as underground cables and transformers.

318 A. B. CAMBEL~~~F. A.

their service area: peak loads must be met, and this is done in a variety of ways such as using peak load units, buying power from the grid, or storing energy during hours. The most frequently used forms of storage are pumped hydro, underylound

cooling. Energy generally magnetic energy storage (SMES) could alter the storage

situation dramatically. In an SMES system an current is induced in a conducting loop when an externally

applied field is withdrawn. In normal conductors, currents will be dissipated in a matter of If the loop is made out of a superconductor, however,

applying SMES in the power industry, off-peak hours would be stored in the superconductor

operating costs. Unfortunately, transfer from the superconducting

levelling need by utilities; this is, in situations, generally is used in pulses rather than continuously.

achieved in a matter of milliseconds discharge in microseconds.

detailed comparison of SMES with other storage forms may be found in a 1976 EPRI additionally, analyses for the Department of Energy by the Bechtel Group and by G.A. Technologies13 base-load capacity. estimated reduction emissions of 510 billion lbs per annum based on 1985

LOSSES IN MANUFACTURING

service. Within the service sector, any due to superconductivity

magnetic resonance imaging; cryogen. In it is difficult

sectors. Accordingly,

subsector 714.2 billion kWh in 1985.14 About three-quarters electric motors. (In fact, in the U.S. about two-thirds of all

electricity consumption is due to these motors.)” electric generators, electric motors ranges only from about 80% to 92%; there is thus considerable figures, a 5% improvement

emissions by 180 billion lbs. Industries that operate larger motors could benefit particularly

resulting from HTSCs might make retrofitting profitable.

Magnetic separation levitated trains, both of which are through the superconductivity Meissner reduction within the manufacturing Magnetic separation

HTSC-type separation magnets could reduce operating compared to conventional


Magnetically levitated trains are being developed in West Germany and Japan; the former uses conventional magnets, while the latter uses liquid helium magnets. HTSCs could be used in these trains and in the many electric-drive trains used in Europe. Because of the relatively small electricity consumption of U.S. electric trains (less than O.l%), conservation opportunities (and CO2 emission reduction) in mass transportation are more pronounced in Europe.

PRELIMINARY CONCLUSIONS

Application of HTSCs in both the utility industry and other economic sectors dependent on electricity could result in appreciable reductions of CO2 emissions.

Reductions of CO2 emissions would be significant (Figs. 10a and lob) if HTSCs were available in a technologically developed form and at economically competitive prices. Potential CO2 emission reductions for the U.S. alone amount to 1.48 trillion lbs, or 14.8%, based on 1985 energy consumption figures. Worldwide, HTSCs could reduce CO2 emissions by 3.92 trillion lbs annually.

HTSCs are likely to be introduced first in applications where superconductivity at liquid nitrogen temperatures already offers advantages. Classical superconductors are now in use, for example, in research, in supercomputers, and in magnetic resonance equipment found in hospitals. Superconducting magnetically levitated (MAGLEV) trains are under study in Japan, and trains with conventional magnetic levitation are being developed in Germany. In these situations, application of HTSCs could achieve economies in capital and operational costs.

Before their commercial application can be widespread, however, several technological developments are needed, i.e.: (a) The critical temperatures must be raised. (b) Current densities must be raised to a range of approximately lo4 amps/cm2 to 16 amps/cm2. This current density would have to occur in the overall superconducting material, including the needed stabilizers. (c) Superconducting materials must possess sufficient structural stabiity to withstand the required static, dynamic, and thermal loads. (d) New techniques must be developed and implemented, such as the abiity to make superconducting connections in an industry using numerous electrical connections. The extent to which these developments are needed will depend on the application. For example, the requirements for overhead transmission lines are far more stringent than for underground cables. New vistas will open if superconductivity with the requisite technological characteristics is developed at room, and even higher, temperatures.

Presently, there is intense R&D work in science and engineering to overcome HTSC technical problems. Much of this work has been pursued in the absence of a theory that explains the phenomena involved. This may not necessarily constitute a barrier to successful research and development, however: the science of thermodynamics came about well after the steam engine was developed and commercialized. On the other hand, the lead time between a scientific discovery and its commercial application is diminishing.” For example, it took 51 years from Faraday’s discovery in electromagnetism (1881) to build the first practical electric generator; it was 40 years from Einstein’s special theory of relativity (1905) to detonation of the fast nuclear bomb, but only 6 years from Esaki’s 1957 discovery of semiconductor to the commercial manufacture of semiconductor diodes. Thus, recent scientific breakthroughs in superconductivity may well facilitate rapid commercial application. Rapid implementation of HTSC technology is particularly desirable, moreover, because power plants have an expected lie of 40 years and the potentially serious impacts of CO2 emissions are perhaps no more than several decades away.

There is a small, but significant, chance that the efficiency of HTSCs could, ironically, turn out to be counterproductive in terms of CO2 emission reduction. For example, the success of such applications as magnetic imaging devices or magnetic levitation trains could actually increase the demand for electric power because their technical and economic advantages might encourage their wider deployment. In most cases, however, the increase realized by the HTSC application (e.g., implementation of high-speed trains) would generally be counter balanced by a decreased demand elsewhere (e.g., greater mass transportation availability would mean less personal transportation).


=I

100

0 I!-

500 510

180

I Fig. 1Oa. Amount of potential reductions in Cm

emissions by sector.

Gwwation

2

Fig. lob. Percentage of potential reductions in CO2

emissions by utility subsystem and other industries.


OTHER CONSIDERATIONS

During the energy crises of the 197Os, there was considerable interest in renewable energy sources. This interest has since waned because fossil-energy costs have dropped and renewable energy has not been an economical alternative. After a decade and a half, renewable energy has not gained sufficient market penetration to be included in energy supply statistics. Major barriers to acceptance include the decentralized nature of renewable energy sources andI; lack of suitable storage. The introduction of HTSCs significantly changes the picture, however.

All renewable energy sources (except solar thermal space and water heating) could benefit from the application of HTSCs. For example, wind energy conversion (WEC) and solar power could benefit from the more compact alternators; geothermal energy-steam generators could improve their efficiencies, and off-shore ocean thermal energy conversion c&d experience lower line losses.” Some of these, such as WEC, might become more prominent, because in the case of large wind energy farms SMES would make them more practicable. In addition, minicomputers could be used for system integration and control of distributed solar energy systems. By making alternative energy more economical, these devices might penetrate the energy market more than they have in the past and serve as electrical energy suppliers that do not emit CO2. However, in the near term, reductions of CO2 emissions would be a relatively small, indirect effect of making alternative energy more attractive with HTSCs.

It should be noted that elect&cation is a key concern in developing countries; moreover, many of these rely heavily on fossil-fuel-burning plants. HTSCs could offer a viable alternative in these countries. Further, because the associated R&D work is relatively low cost, it could be pursued by personnel within developing countries to help them develop an educated infrastructure.

Acknowledgement-The authors extend their thanks to D. Barns, S. U. Chaudhry, S. Edwards, G. Feric, M. A. Javed, R. S. Silver, and W. F. Zeller III, who critically reviewed earlier versions of this manuscript and made useful suggestions. Also gratefully acknowledged are contributions by M. W. Firestine, N. Congress, J. Simon, M. Shomon, C. Yaron, and M. Taylor in editing and producing the manuscript.

REFERENCES

1. J. G. Bednorz and K. A. Muller, 2. Phys. B64,189 (1986). 2. Personal communication with Dr. D. Gubser. (1988). 3. Proceedings of the 1972 Applied Superconductivity Conference,” IEEE, New York, NY

(1972). 4. J. L. Kirtley, Jr., “Impact of HTSCs on Generators,” in Advances in Applied Superconductivity:

A Preliminary Evaluation of Goals and Impacts, p. 45, ANL/CNSV-64, Argonne National Laboratory, Argonne, IL, 45, (1988).

5. A. S. Albanese and M. Steinberg, Environmental Control Technology ForAtmospheric Carbon Dioxide, DOE/EV-0079, Brookhaven National Laboratory, Upton, NY (1980).

6. A. B. Cambel, Sci. I. 3,57 (1%7). 7. A. B. Cambel, D. Cutler, A. Ghamarian, G. Hefferman, eds., Enemy 5,667 (1980). 8. P. Thullen, J. C. Dudley, D. L. Greene, J. L. Smith, Jr., and H. H. Woodson, IEEE Trans.

PowerApp. Sys. PA!MO, 611(1971). 9. R. F. Giese, R. A. Thomas, and E. B. Forsyth, “AC Transmission,” in Advances in Applied

Superconductivity: A Preliminary Evaluation of Goals and Impacts, p. 69, ANWCNSV-64, Argonne National Laboratory, Argonne, IL (1988).

10. E. B. Forsyth and R. A. Thomas, Cryogenics 26,599 (1986).

322 A.B.CAMBEL~~~F. A. KOOMANOFF

11. A. B. Cambel, “The Techno-Socio-Economics of Distributed Thermal Energy as Part of Load Management,” in Alternative Eneqg Sources vll, T. N. Veziroghr ed., Hemisphere Publishing, Washington, DC 6, p. 3, (1987).

12. An Assessment of Energy Storage Systems Suitable for Use by Electric Utilities, EPRI EM-264, Electric Power Research Institute, Palo Alto, CA (1976).

13. R. F. Giese and J. D. Rogers, “Superconducting Magnetic Energy Storage,” in Advances in Applied Supexonductivity: A Pwlimina~ Evaluation of Goals and Impacts, p. 101, ANL/CNSV-64, Argonne National Laboratory, Argonne, IL (1988).

14. T. Moore, EPRZ Journal 12,4 (1987). 15. E. J. Daniel, B. W. McConnell, and T. A. Lipo, “Motors,” in Advances in Applied

Superconductivity: A Preliminary Evaluation of Goals and Impacts, p. 111, ANLICNSV-64, Argonne National Laboratory, Argonne, IL (1988).

16. “Advances in Applied Superconductivity: Goals and Impacts,” Draft Report, Argonne National Laboratory, Argonne, IL (1987).

17. W. J. Broad, The New York Times-Science Times CXXXVII, Cl April 5, (1988). 18. A. B. CambeI, Keynote Address, International Conference on Alternative Energy Sources,

Miami, FL (1987). 19. A. M. WaIsky, J. G. DeSteese, J. A. Dirks, M. K. Drost, S. B. Merrick, R. M. Smith, and T. A.

Williams, “Potential Impacts of HTSCs on Renewable Energy Technologies,” in Advances in Applied Superconductivity: A Preliminary Evaluation of Goals and Impacts, p. 15, ANL/CNSV-64, Argonne National Laboratory, Argonne, IL (1988).

high-temperature superconductors and co2 emissions

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