13 - Minervini

Portions reprinted, with permission, from Massachusetts Institute of Technology and Joseph Minervini.

Technology & Engineering Division

Development of HTS Cables for DC Power Transmission and Distribution

Joseph V. MinerviniLeslie Bromberg

Makoto TakayasuChristopher Miles and Nicholas R. LaBounty

MIT Plasma Science and Fusion Center

Eighth Annual EPRI Superconductivity ConferenceDoubletree, Oak Ridge, TN ~ November 12 – 13, 2008


Technology & Engineering DivisionOutline

• HTS DC Advantages• Cable Design Concepts• Chubu-MIT HTS DC Cable Collaboration• Long Length Cooling• Current Lead Cooling• Potential Near Term Application• Conclusions


Technology & Engineering DivisionDC Superconducting Transmission Line

Advantages:•No DC resistive losses•No AC inductive storage•Low or no AC losses•Long range transmission of high currents, including undersea•Very high power ratings including transmission of several GVA •Fault currents limited by fast acting inverters at AC/DC and DC/AC ends of the line•Low voltage transmission, if desired, limiting the need for high voltage transformers•Simplified cable design, more amenable to using HTS tape geometry•Cable coolant also used to cool solid state inverters increasing capacity and reducing high temperature aging degradation

Disadvantages: Invertors can add substantially to cost



HTS DC increases efficiency for long distance transmission Opens other advanced technology opportunities:

• Direct connection of alternative low-carbon or carbon-free power sources:WindSolar PVFuel CellMicroturbineother

• Connection of advanced energy storage devicesFlywheelBatterySupercapacitorSuperconducting Magnetic Energy Storage (SMES)other

HTS DC Applications

}Grid independence

} System Stability and Power Quality



HTS DC Transmission Cables

DC-to-AC Power Conversion

Off-Shore Wind Farm Power Transmission

Using HTS DC Cable



Solar Photovolatic or Concentrated Solar Thermal Power Transmission Using HTS DC Cable

Solar PV CSP

Solar and WindDC Power

Transmit DC before conversion?

DC Superconducting Power Transmission Line Experiment in

Chubu University&

Collaboration with MIT

Prof. Satarou YamaguchiDept. of Electrical Engineering

[email protected]

Center of Applied Superconductivity and Sustainable Energy Research

(CASER)

Experimental Device in Chubu University

Parameterscurrent > 2.5 kAvoltage > 20 kVlength ~ 20 mSumitomo Bi-2223 cable

coolant; LN2equipped with pump and cryogenic cooler72 K - 77 K

SC Cable

made by Sumitomo

insulation layer

HTS Tape

formercopper wires

inner spring

center holefor coolant path

Photo of cross-section

40φ

insulation30kVDC

earth layer

formercopper wires

HTS Tape x 39

Side View

Tape conductor 1st layer; 192nd layer; 20

Bi-2223/ 100A grade

Insulation Volt. DC20kV Insulator, PPPL

Outer radius 40φ Center hole 14φ


Technology & Engineering DivisionMIT High Current HTS

DC Cable Designs

Multiple Layers

Triplet

Carpet Stack

Twisted Triplets

Wedge Stack

Twisted Triplets



• Use Basic Carpet Stack– tapes can be insulated or soldered• Square or rectangular stack • Base element former can be– conducting– non-conducting– Structural• Tape shape requires relatively long twist

pitches• AC losses not an issue for DC applications



• 25 kA at T = 65 K - 77 K• Carpet Stack triplets have highest Je• Allows for smaller cryostat and lower heat leak• Carpet Stack and wedge base conductors allow many

variations on cable patterns and total tape number


Technology & Engineering Division Potential OpportunityData Server Centers

• In 2006, electricity consumed by servers in U.S. data centers (including cooling and auxiliary infrastructure) represented about 1.5 percent of national electricity use*.

• Internet data center consumes ~ 1–2 kW/m2.– 10 MW-50 MW+ total capacity in new centers

• DC may be preferred– Minimizes conversion losses

• ~7-10% energy savings migrating to DC– No reactive power– Power multiplier: for 1 W dissipation saved, 1.5 - 2 W

cooling eliminated

Google datacenter near The Dalles Dam

*”Report to Congress on Server and Data Center Energy Efficiency”, U.S. Environmental Protection

Agency, Aug. 2, 2007



Expected Data Server CenterPower Growth

G. Lawton, Powering Down the Computing Infrastructure, Computer, IEEE, 40, issue 2, p 16-19, Feb. 2007.

DC Distribution Demonstration Developed by LBNL and Industry Partners

William Tschudi, LBNL

Measured Best in Class AC System Loss Compared to DC• ~9-12% efficiency improvement measured by elimination of transformer

and second AC/DC conversion

PSU

ASD

Ballast

AC Distribution

Electronicloads

Lightingloads

Motorloads

AC/DC

AC/DC

VRAC/DCDC/DCAC/DC DC/AC

DC/AC

DC/AC

60 Hz AC480V

AC/DC DC/AC

DC/ACDC

300-400V

PV

FC

Benefits of 400Vdc

Slides courtesy of Annabelle Pratt-Intel

PSU

ASD

Ballast

Facility Level

Electronicloads

Lightingloads

Motorloads

AC/DC

AC/DC

VRAC/DCDC/DCAC/DC DC/AC

DC/AC

DC/AC

60 Hz AC480V

AC/DC DC/AC

DC/ACDC

300-400V

PV

FC

Benefits of 400Vdc


XX

XXXX

XXXX XX

XX

XX

ASD

PSU

Ballast

400V DC facility with DG

60 Hz AC480V

Electronicloads

Lightingloads

Motorloads

VRDC/DC

AC/DC

DC300-400V

DC/AC

DC/AC

Benefits of 400Vdc

AC/DC

DC/DC

DC/DC


ASD

PSU

Ballast

400V DC facility with SC Bus

60 Hz AC480V

Electronicloads

Lightingloads

Motorloads

VRDC/DC

AC/DC

DC300-400V

DC/AC

DC/AC

Benefits of 400Vdc

AC/DC

DC/DC

DC/DC



Technology & Engineering Division 4400 Ampere Cable Sizes

1.75” Diameter cable325 A per cable

14 Cables35 lbs/ft

0.605” Diameter cable133 A per cable

33 Cables8 lbs/ft

1.75” Diameterup to 30 Conductors

up to 200 Amps per Conductor1 Cable2.0 lbs/ft

Copper - Air cooled Copper - Water cooled HTS- LN2 Cooled

Very High Power Density is Achievable with Superconductors

x 10 = 4000 A @ 0 Voltage ®



Schematic 10MW, 400V, 25 kAData Center Layout



Technology Needed to ImplementSC Distribution

• As opposed to transmission, there are a large number of secondary spurs, with relatively high density (depending on application)

• Refrigeration losses dominated by leads, not by distributed cryostat or AC losses

• Need to address the problem of– Electrical connections through low-loss leads– Cooling manifolding



Navigant Consulting costing predictions of SC components in 2008-2012:http://www.energetics.com/meetings/supercon06/pdfs/Plenary/07_Navigant_HTS_Market_Readiness_Study.pdf

Power Dissipation with Standard Leads (kW)

Summary of Preliminary System AnalysisMIT Energy Initiative Seed Fund - 2008

Current lead loss is 0.05 W/A-lead

Power Loss HTS + Cu

(2007)

Power Loss HTS + Cu (2008-2011)


Power Loss All Cu

HTS Leads 10 10 10

HTS Cryostat 0.45 0.225 0.225

HTS Cold Power Total 10.450 10.225 10.225

Refrigerator Wall Power 300 177 118

Copper Bus 16 16 16 250

Total Electrical System Power 316 193 134 250



Navigant Consulting costing predictions of SC components in 2008-2012:http://www.energetics.com/meetings/supercon06/pdfs/Plenary/07_Navigant_HTS_Market_Readiness_Study.pdf

Power Dissipation with Optimized Leads (kW)

MITEI Seed Fund Study (cont’d)

Current lead loss is 0.025 W/A-lead achieved by intermediate cooling stage

Power Loss HTS + Cu

(2007)



Power Loss All Cu System

HTS Leads 5 5 5

HTS Cryostat 0.450 0.225 0.225

HTS Cold Power Total 5.450 5.225 5.225

Refrigerator Wall Power 157 90 60

Copper Bus 16 16 16 250

Total Electrical System Power 173 106 76 250



Navigant Consulting costing predictions of SC components in 2008-2012: http://www.energetics.com/meetings/supercon06/pdfs/Plenary/07_Navigant_HTS_Market_Readiness_Study.pdf

Capital Costs (k$)


Capital Costs HTS + Cu

2007

Capital Costs HTS + Cu 2008-2011

Capital Costs HTS + Cu 2012-2016

Capital Costs All Cu

HTS Tape 2,800 560 112

HTS Cryostat 200 130 44

HTS Refrigerator

1,050 640 260

HTS Total 4,050 1,330 416

Copper Bus 11 11 11 160

Total Capital Cost

4,061 1,341 427 160



Operating Costs of Power ($/Hr)

Electricity cost = $0.10/kW-Hr


Operating Costs 2007

Operating Costs

2008-2011

Operating Costs

2012-2016

HTS (standard leads) 31.69 19.27 13.38

HTS (optimized leads) 17.26 10.62 7.61

All Copper 25.07 25.07 25.07

HTS Payback Period (standard leads)

Never 23 Years 2.6 Years

HTS Payback Period (optimized leads)

57 Years 9.2 Years 1.75 Years


Technology & Engineering Division Summary

Use of HTS could open innovative opportunities in datacenters for decreased power consumption, flexibility and easy of constructionApplication to data server centers is a near term application with potential large efficiency gainsShort time scale implementation allows further development for other MicroGrid applications with similar technologyEstablishes technology for:

• Bringing large-scale power to land from offshore wind farms

• Combining large-scale solar PV or solar thermal systems to the grid

• Long distance power transmission and/or grid interconnects

Optimized DC cable, cryostat and current leads require development program

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13 - Minervini