ground based wireless and wired transmission cost comparison

7/28/2019 Ground Based Wireless and Wired Transmission Cost Comparison

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GROUND BASED WIRELESS AND WIRED POWER TRANSMISSION COST COMPARISONRichard M Dickinson, JPLJet Propulsion Laboratory M I S 238-5284800 Oak Grove DrivePasadena, CA 9 1 109(818) 3.54-2359, Fax: (8 18) 393-0207

Abstract:Recent interest in applicationsof wireless power transmission has raisedthe question of the cost comparison ofwireless vs wired transmission of powerfrom ground site to ground site. Costs interms of $NW-km, a figure of merit, forpast demonstrations and stimates forfuture suggested activities are givens afunction of power delivery distance.Wired power types uch as open wirehigh voltage ac and C lines, direct burialand submarinecables, appliance cordsand circular waveguide transmission linesare discussed. Beamed RF powerapplications in laboratory tests, fieldtests, proposed direct power deliveryapplications and power via reflector relayare presented. Although not ground-to-ground, but ground-to-air, additionalhistorical and proposed electric aircraftdemonstrations and airship applicationsare also discussed for comparison.A graph of the first approximation ofinstalled.system costs as a function ofdistance, in then year for the figure ofmerit is generated. Except for the veryhighest power, longest range cases, thewireless power cost is orders ofmagnitude more costly than wired powerfor delivery at the same distance onrnear the Earths surface.INTRODUCTIONRecent studiesby NASA of Space(Based) Solar Power [ I ] have rekindledinterest in transmitting electric power byRF microwave beam [2].

Owen Maynard, Aerospace Engr. Ret.5.5 Blue Springs Drive, Apt. 70.5Waterloo, Ontario Canada N2J-4T3

Fax 1.519) 888-9176(5 19)888-996.5

Those unfamiliar with the lements ofcosts want to find an Earth based locationfeature such as a canyon[3], rivercrossing, lake [4], strait, or otherdifficult crossing to apply F wirelesspower transmission (WPT) thinkingtmust be cheaper than wired ower.To our knowledge, such relative (albeitimprecise) cost comparison has not beenpublished. The purpose of this paper isto attempt to document a firstapproximation comparisonof wired andwireless RF power transmission,reception and control systemss afunction of power magnitude anddistance.Because the field f WPT is rather new,we will be mostly comparing laboratorytests, first-of-a-kind demonstrations andprojected applications costs withestablished utility costs and their longrange projections. Thus, a scatter plot ofthese disparate costs will be usedor thereader to compare, with the caveat that thevasious entries havemarkedly diifferentprovenance. Only general trends shouldbe derived from such data.Economical applicationsof beamedpower in the near future will probably befor powering high altitude telecom andobservation platforms,stratospherictourism airships and other ff-Earthvenues. Although not strictly ground-to-ground, they are point-to-pointand wheredata exist hey will be included forcomparison.

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contract with the National Aeronautics and Space Adm inistration.The research described in this paper was carried out by the Jet Propulsion Laboratory. California lnstltute of Technology, under a

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As the two key aspects of WPT arepower magnitude delivered and thedistance over which t is delivered,wewill use as a figure of merit (FOM) theinstalled system cost scaled by thedistance in km and the power magnitudedelivered in MW. The WPT installedcosts will include the electric powerconditioning at both endsf the link aswell as the beam safety equipment. Costconsiderations for the source, prime-generatoror load will not be included,only transmission costs.We will explore the safety and economicsof wired and wireless power, where bothends of the transmission link are on thesurface of theEarth, by briefly reviewingprevious activities. This paper will thendiscuss some current investigations ostestimates and compare themo pastwireless and wired power cost estimatesor projections. Then conclusions willbedrawn.GROUNDWPTBACKGROUNDOne of the authors (Dickinson) recallsbeing asked in 1976 by Sam Fordyce hisNASA Headquarters sponsor to look ntodelivering electric power via microwavesto Manhattan Island fromNew Jerseyover a particular 16km range, asundenvater cables were being overloadedand were expensive to install. This wasafter his successful managingf ademonstration in 1975 [5] of deliveringover 34 kW of DC at 1.6 m atGoldstone, CA under the ContractProgram Management by the otherauthor (Maynard) when he was atRaytheon. We both thank Bill Brownvery much for developing the rectenna [6]that was key to that project, and being itsTechnical Director.The calculation performed for Fordycedetermined that it would require atransmitting ma y and a rectenna array,both larger in diameter than the height ofan 18 story building, in order to achieveover 90% beam coupling efficiency at2.35 GHz over the distance required.After that shochng result, we looked

elsewhere for potential applications, butfound no critical or desirable sites. Theend of the oil crisis and the NationalResearch Council report [7] soon took thewind out of SpaceSolar Power (SPS)sails, and interest n WPT waned.Thus WPT activities were mostly quietuntil 1987 when th e Canadians poweredamodel aircraft with rectennas near 2.45GHz [8].A contact from Exxon in Houston wantedto know if the energy from Alaska northslope oil could be converted tomicrowaves and delivered o Houston.An Alaska entrepreneur wanted to knowif WPT could be used to supply electricpower to native American strandedvillages in his state. DOE began lookinginto delivering Alaska crude energy toJapan via beamed power. NASAsCenter for Space Power at Texas&M[4]along withDOE also began aninvestigation of conducting ademonstration of beaming power acrosslake toa village in Alaska.S. Bharj and colleagues at Sarnoff,powered the Moonstruck rover at5.8GHz with 450W output at 200ft range(61m) in 1992 [9].The Japanese conducted demonstrationof ground-to-ground power transmissionat Yamasaki with the Kansai ElectricCompany [IO] in 1994-95. Theyinvestigated beaming power from theirmainland to islands in the Inlandea.However, subsequently they ncounteredsevere environmental concerns from theisland residents and abandoned theinvestigation.Ralph Nansen [111endeavored to puttogether and conduct an approximately$50 M , 3-year demonstration n Texas ofground based photovoltaic powerconverted to 50-250kW microwave RFand beamed 1-5 km to a rectenna to betied into the local utilitys grid. Theproject did not materialize due to lack offunding.

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provide the short term storage to bridge tomedium term flywheels ando longerterm natural gas turbinesor pumpedhydro storage for example.

The second potential WPT venue whichsurfaced in 1997-8 was in EasternCanada across the Straitf Bell Isle thatseparates Newfoundland island fromLabrador mainland. Here the distance isabout 40 km and the desired power levelwas postulated to be about 800MW. Inaddition to cruise ships, there areoccasional 60 m (several hundredft.) tallicebergs that scour the strait bottom,giving underwater cable systemsproblems.Again, due to weather andQOSconsiderations, 2.45 GHz is the ISM-Band frequency of choice. Thus thediameter of transmitters and rectennasor90 % beam coupling efficiency must beover 97 m in diameter(29 stories tall)each if equal in size. In this case, thebulge of the Earth adds n additional3 1.25 m height at each end for the beamto just be tangent to the Earth at the mid-point. Realistically, the endsof theterminal need to be sited at differentelevations to minimize multipathpropagation and for safety reasons thereis a preference for the rectenna o behigher.Terminals of the RF link should be basedon mountain topsor hillsides inorder forthe beam to clear cruise ships. Aninvestigation by Maynard revealed thatsuch sites in the topographyf the BellIsle strait would requireRF transmissiondistances from 65 to 88 km, not 40 km,thus increasing the required transmitterand rectenna diameters to over130m.Similar beam safety and energy storageconsiderations apply as n the Singaporecase, but due to the large quantity ofpower (0.8 GW), the prudent engineeringdesign would be to have parallel pairs toprovide redundancy for accommodatingiceberg blockage and to permit down timefor maintenance. Perhaps four 200MW

links spaced more than an iceberg lengthapart should be used.WIRED POWER SYSTEM COSTSThe least costly wired powertransmission system s a 6 f t appliancecord at 10 A, 1 1OV and $5 cost, and soits installed cost figure of meritFOM) asshown in the comparison graph is over10**3 $/MW-km.The United States Department ofAgriculture Rural ElectrificationAdministration (REA) Bulletin 151shows the results of typical economicconductor analysis or a high voltagetransmission line in support ofa 200MWload at $160,000/mile, r for example at100 km long, the FOM is over 10**2$/MW-km, an order of magnitudecheaper than the appliance ord. There areeconomies of scale at work.Obtained from theAsea Brown Boveri(ABB) web site is the costf a 65 kmundersea 200MW ine between Finlandand Estonia at FOM of nearly 10**4$/MW-km. Data for a 1.2 GWunderwater link or the New York PowerAuthority to Long Island at 13 km rangehas a FOM that is about 80% of theBBlink, probably due o the larger powerlevel that is carried. However, both arean order of magnitude over the REAine.The approximately 1 GW, +/- 500kVDC line from the Dalles in Oregon toSylmar in California around 000 kmhas a FOM of installed cost of around10**3 $fMW-km.Based upon Bechtel studies in 1968 [161,a TEOl mode circular waveguide at GWand 500 km length has a FOM of over10**2$/MW-km. An 8 GW nearly lo00km system would havea FOM about halfthat, the lowest cost ( in then-year$)ground-to-ground wired systemencountered.Michael Klemke has estimated the costfmoving large quantitiesof electric powerover intercontinental distances with

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To the best of the authors knowledge,only a French proposal [3] is currentlyunderway. On La Reunion Island in theIndian Ocean, the French are developinga beamed power system that is to beenvironmentally friendly o transmitpower down a canyon to a resort complexat a lower elevation. The intent s not tofully competeon price of power deliveryhowever. Funding continues to be aproblem nevertheless.CURRENT WIRELESS POWERTRANSMISSION INVESTIGATIONSEach author is involved indirectly withinformal investigations into surfacebeamed power applications,pro bono.The first potential venue was fromSingapores large island to its other ff-shore islands. The ranges involved are amaximum of 10 km and the powermagnitude was 100 M W .At 2.45 GHz, the S-Band Industrial,Scientific and Medical Band (ISM), thewavelength is -12 cm and the equaldiameter apertures at transmitter andrectenna for90 % beam couplingefficiency are 48.6 m, nearly 160 ft,about 14.5 stories based on 11 ft perstory.Depending upon the overwaterrossingutilizahn, it is estimated thatanadditional 42mof height may be requiredfor the bottom edge of the power beam toclear the highest habitable spaces aboardcruise ships, and allowing for thecurvature of the Earth. The message isthat large structures are potentiallyinvolved in an area where high windsmay occur. Hilltop locations would helpthe altitude requirements,f they areavailable, otherwise tall structures mustbe added to the system cost.With further regard to weather,depending on he quality of service(QOS) desired for the electric powerdelivery, the sometimes torrential rains nSingapore need to be considered. Therain ratesof up to 25 mm/hr are exceeded

0.3% of a year, ( 26 hours cumulative),and the attenuation can exceed0.1 dB/km for 5.8 GHz ( 20.5% power loss in10 km), and 0.007 dB/km fo r 2.45 GHz(1.6 % loss for 10 km) [121. At rainrates of 100mm/hr,exceeded 0.03%/yr.(2.6 hr), the attenuation can exceed 0.8dB km at 5.8 GHz (84% loss), 0.025dBkm for 2.45 GHz (5.6% loss) and0.002dBlkm for the 915 MHz UHF ISM-Band.Although the5.8 GHz ISM bandfrequency (wavelength of -5 cm) couldmake the required apertures smaller bythe square root f the frequency atio, theweather losses are probably ntolerable.The sizesat 915 MHz arecorrespondingly much larger, thus 2.45GHz is the default choice.In order to yield 00 M W of output acpower at50 Hz fo r distribution, nearly150M W of RF needs to be generated atthe transmitting array. The averagepower density over the aperture would be82.4 kW/m2. However, the peak powerdensity resulting from the requirementosupport the nearly 10 B edge taper thatis required to place mostof the power inthe main beam and little in the sidelobes,will yield about 190kW/m2 on axis.Further phase focusing on xis [131 atabout 3.86km range due to therequirement to have spherical phasefront convergingOR the rectenna, willyield 14 dB higherpeaks, or 4.76MWlm2.This is very hazardous to birds or otheraviation and thus will require some meansof detecting imminent beam crossings[141 coupled with interlocks to hut downthe beam, until the crossings complete.The beam interruptions will require thesystem design to accommodate theresulting voltage transients in thetransmitter and receiver equipment safely.There will also be required some form ofon-line floating and switched energystorage in order to prevent the serviceinterruptions to the customer. Atadditional cost, on-line batteries can

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1 . Mankins, J.,The Space Solar PowerOption, Aerospace America, pp. 30-36,M ay, 1997.2. Brown, W.,The History of PowerTransmission by Radio Waves,IEEETransactions on Microwave Theory andTechniques, Vol. MTT-32, No. 9, pp.1230-1242, Sept. 1984.3. Celeste, A., et al., The Grand-BassinCase Study: Technical Aspects, Proc.SPS97, Montreal, pp. 255-258, Aug.24-28, 19974. Haldane, R. and Schupp, B.,Alaska21 A Terrestrial, Point-To-PointWireless Power Transmission System,Conference Proceedings, WPT93, FirstAnnual Wireless Power TransmissionConference, pp. 191-198, San Antonio,TX, Center for Space Power, TexasA&M, College Station, 23-25 Feb. 1993.5. Dickinson, R.,MicrowaveTransmission System for Space Power,Raumfahrtforschung, Band 20, Heft5,pp 238-241, Oktober 1976.6. Brown, W.,The History of theDevelopment of the Rectenna, Presentedat the Rectenna Session of the SPSMicrowave Systems Workshop, JohnsonSpace Center, Houston ,TX, Jan. 15-18,1980.7. National Research Council,ElectricPower From O rbit:A Critique of aSatellite Power System,NationalAcademy Press, Washington, DC, 1981.8. Schlesak, J. and Alden, A.,SHARPRectenna and Low Altitude Flight ests,Proc. IEEE Global TelecommunicationsConference, New Orleans, Dec. 1985.9. Bharj, S . et al.,A MicrowavePowered Rover for Space Exploration inthe 21st Century, ConferenceProceedings, WPT93, First AnnualWireless Power TransmissionConference, pp. 449-455, San Antonio,

TX, Center for Space Power, TexasA&M. College Station, 23-25 Feb. 1993.10. Shinohara, N. and Matsumoto,H.,Experimental Study of LargeRectenna Array for Microwave EnergyTransmission, IEEE Trans. onMicrowave Theory andTechniques, Vol.46, No. 3, pp. 261-268, March 1998.11. Nansen, R.,Ground Test Programfor Developing Solar Power Satellites,Space Energy and Transportation, Vol. 1,NO. 3, pp. 187-194, 1996.12. Flock, W.,Propagation Effects onSatellite Systems at Frequencies Below10 GHz, NASA Reference Publication1108. Dec. 1983.13. Hansen, R.,Focal RegionCharacteristics of Focused ArrayAntennas, IEEE Transactions onAntennas and Propagation, Vol. AP-33,No. 12. pp. 1328-1337, Dec. 1985.14.http://www.atlanticrt.com/jma7736.htm, JRC JMA-7736 BirdWatching Radar.1.5. REA Bulletin 1724E-200, DesignManual for High Voltage TransmissionLines, Electric Staff Division, RuralElectrification Administration,U.S.Dept.of Agriculture, Washington, D.C. 20402,revised Sept., 1992.16. Dunn, D. and Lowenstern,W.,Economic Feasibility f MicrowavePower Transmission inCircularWaveguide, Sect 3.6, Microwave PowerEngineering, Vol. 1, pp., 256-269,Academic Press, N Y , 1968.17. Klimke, M.,New Concepts ofTerrestrial and Orbital Solar Power Plantsfor Future European PowerSupply,Proc. SPS97, Montreal, pp. 67-72,Aug. 24-28, 1997.18. Dickinson, R. and Brown,W.,Radiated Microwave Power TransmissionSystem Efficiency Measurements,

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normal-conducting HVDC cables,hattranslates intoa FO M of under 10**3$/MW-km [171.HISTORICAL WIRELESS POWERCOSTSTRANSMISSION FIGURE-OF-MERITProceeding mostly by distance, the firstentry in the plot is the approximately 1.7m range delivery of about 495 done byBill Brown and recorded by Diclunson in1975 [181. Based on the estimateddevelopment cost, the FOM is over10**10$/MW-km.The next entry is the 94 JapaneseYamazalu test [9]delivering about 24 UTat a range of 42 m, withan estimatedFOM of slightly under1010$/MW-km.The slightly over$1M Goldstone test in75delivered 34 kW at1.6km for a FOMof about 1.8X10**7$/MW-km.Although not ground-to-ground,additional entries are given for thehistorical beamed power to modelhelicopter tests by Bill Brown (50 ft.,270W DC out) in the US in 65,and themodel airplane tests in Canada and Japanin the SHARP 87 andMILAX 92demonstrations, respectively. Theauthors did not have the detailedosts forthe demonstrations, but based an estimateon prior knowledge and estimates of thenumber of staff nvolved, the time, theequipment quantity and complexity etc.,in order to arrive at an approximate FOM.A similar estimate is given for the 95demonstration in Japan of 3 kW delivered50 m range to the 2.7mX 3.4m rectennaon the ETHER experiment on theHALROP airship [19 .The authors estimate f a full-blownairship system installed cost for 0,000 ftoperation and over 1MW transmittedpower is shown as near 10**6$/MW-kmFO M for todays $.

Among the lowest FOM WPT approachesare the Power Relay Satellites[20,2 ,22,23,24], at around 10**3$/MW-km FOM. These systems areground-to groundelectric power delivery,but via orbiting reflectors, in rder to getaround the bulge of the Earth. The Bekeymillimeter wave scheme (FOM $750-$1,375/MW-km) proposes a clevercombination of pumped hydro storage toimprove QOS and to provide a beam-safety zone around the ver-waterrectenna sites.CONCLUSIONSThe very short range 1- lorn),preliminary demonstrations fW atlow power levels(< kW) were in generalquite costly, however, the cost estimatesare coming down for larger power levelsand longer ranges. Tens of km WPTsystems are in the rangef several $M /MW-km, whereas similar range wiredsystems are of order $lO,OOO/WMW-km,at least two orders of magnitude less.It is apparent from the plottedata points,and the indicated trend-lines, that longerrange higher power levelystems areestimated to be lower cost in /MW-km.Both for the wireless and wired owertransmission systems. However, theirabsolute costs are in Billions, and onlyMVDC lines have been builtc date.Given the economic disparity and beamsafety concerns, it is oubtful that shortrange WPT applications involving beamsthat are near tangent to thearths surfacewill ever be useful for electric powertransmission as compared to wired powerdelivery. However, this does notpreclude research and development testsand demonstrationsof WPT from point topoint on the Earths surface, whereeconomic competitionis not the primeconsideration.

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REFERENCES

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NASA JPL Technical Memorandum 33-727, Pasadena, CA , May 15, 1975.19. Fujino, Y., et al.,Wireless PowerReceiving System for MicrowavePropelled Airship Experiment. paceTechnol, Vol. 17, No. 2, pp. 89-93,Pergamon, Elsevier Science Ltd. 1997.20. Ehricke, K.,Space Technology andEnergy, Presentation to the paceScience and Applications and the EnergySubcommittees of the Committee onScience and Astronautics,U.S.House ofRepresentatives, SD 73-SH- 139,24 May1973,21. Rogers, T.,Reflector Satellites forSolar Power, IEEE Spectrum, pp. 38-43, July, 1981.22. Arrott, A.,Power Relay Satellites,Workshop on Wireless PowerTransmission (WIT) StrategicPartnering, pp. 41-46, A. D. Little atDept. of Commerce, Jan. 31, 1994.23. Woodcock, G.,Power RelaySatellites, op cit. pp. 75-81 , Boeing atDOC.24. Bekey, I. and Boudreault, R.,AnEconomically Viable Space Power RelaySystem, IAA-98-IAA. 1.3.03,49thInternational Astronautical Congress,Abourne, Australia, Sept. 28- Oct. 2,1998.

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ground based wireless and wired transmission cost comparison

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