DC Superconductor Cables for Long Distance Transmission

2009 Mid-America Regulatory ConferenceTraverse City, MIJune 14-17, 2009

The challenge of moving renewable power long distances needs another option

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Today’s Key Energy Challenge: Carrying Today’s Key Energy Challenge: Carrying 100’s of Gigawatts of Green Power to Market100’s of Gigawatts of Green Power to Market

Many Issues

• Multiple Sources

• Multiple Destinations

• Cost Allocation

• Siting

• Transmission Across Interconnections

• Losses

Many Issues

• Multiple Sources

• Multiple Destinations

• Cost Allocation

• Siting

• Transmission Across Interconnections

• Losses

Superconductor Electricity PipelineSuperconductor Electricity Pipeline

The Superconductor Electricity Pipeline combines:• Conventional underground pipeline construction

With two power system technologies:• Superconductor cables• Reduced voltage multi-terminal DC power transmission

The result:• A high capacity electric transmission “pipeline” that is:

Underground and easy to site Highly efficient Offers greater security than other technologies Provides for multiple power on- and off-ramps

Superconductors Change the Game: 150X Increase in Power Capacity of Wires

Superconductors are the high efficiency “optical fibers” of power4

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Siting and Security Challenges With Overhead Power Lines

Courtesy Argonne National Lab

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High Voltage AC andLong Distance Transmission…

Superconductor Electricity Pipeline

765 kV Overhead Lines

Power Transfer Capabilities of

Old and New Technologies

“Analytical Development of Loadability characteristics for EHV and UHV Transmission Lines”, Dunlop, R., Gutman, R., and Marchenko, P., IEEE Transactions on Power Apparatus and Systems, Vol.PAS-98, No.2 March/April 1979

…and Long Haul Overhead Lines Generate Heat and Waste Energy

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0%

2%

4%

6%

8%

10%

12%

14%

16%

100 200 300 400 500 600 700 800 900 1000

% L

os

se

s (E

st.

)

Miles

5GW of Renewable Energy Transmission

765kV Overhead Lines

Superconductor Electricity Pipeline

Note: 765kV overhead line losses based on a variety of two and three 2400MVA SIL line designs using 4-, 6-, and 8-conductor bundlesLosses for Superconductor Electricity Pipeline based on 2% DC converter losses and 35 kW/mile refrigeration losses.

New Right of Way SolutionNew Right of Way Solution

Comparison of Transmission Alternatives

Superconductor Electricity Pipelines are uniquely suited for underground, long distance, high power transmission

AC

Point-to-Point

HVDC

Multi-terminal

VSC HVDC AC

Point-to-Point

HVDC

Multi-terminal

VSC HVDC

Multi-Terminal Superconductor

PipelineLow Power (<1GW) Short (<100 mile) lines Low Power (<1GW) Moderate (100-400 mile) lines

Low Power (<1GW) Long (>400 mile) lines Moderate Power (1-5GW) Short (<100 mile) lines Moderate Power (1-5GW) Moderate (100-400 mile) lines

Moderate Power (1-5GW) Long (>400 mile) lines High Power (>5GW) Short (<100 mile) lines High Power (>5GW) Moderate (100-400 mile) lines High Power (>5GW) Long (>400 mile) lines

Unique fit of Superconductor Electricity Pipelines for Long Distance, High Power, Multi-terminal transmission     

TRANSMISSION LINE POWER AND DISTANCE REQUIREMENTS

SUITABLE TRANSMISSION SOLUTIONSOverhead Solutions Underground Solutions

Superconductor Electricity Pipeline:National Loop Concept

Superconductor Electricity Pipeline

AC/DC Converter Stations

11/13/08 11An SC-DC Cable

DC Superconductor Cable

10,000MW in a 3 Foot Gas Pipe

Courtesy of Electric Power Research Institute

Superconductor Electricity Pipelines

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Installation similar to natural gas pipelines…

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Rights of Way Already Exist for Rights of Way Already Exist for Superconductor Electricity Pipelines Superconductor Electricity Pipelines

Advantages of Superconductor Pipelines

• Underground construction with minimum right of way requirement

• Simplified cost allocation due to precise controllability of DC terminals

• Highest power capacity• Highest efficiency (lowest power losses) of any transmission

technology• Ideal for very long distances • Capable of transferring power across the three U.S.

interconnections• Able to accept power from multiple distributed sources, and

precisely deliver power to multiple distributed destinations• Minimizes interaction with existing AC grid, reducing costs and

increasing operational flexibility

Superconductor Electricity Pipelines are uniquely and ideally suited to move renewable energy to distant load centers

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Comparison of a 1,000-Mile, 5 GW Run

Metric DC Superconductor Cable765KV Transmission

Lines

Power Loss(1) 3% Varies with design

Storm/Security Risk Low High

Precise Control for Efficient Markets Yes No

Cost Allocation Method Simple Complicated

Requires Rebuild of Underlying Grid No Yes

“Black Start” Capability Yes No

Permanent Right of Way 3 ft. 400-600 ft.

Aesthetics Good Bad

Electromagnetic Field None High

New Land Required No Yes

Efficiency Savings Per Year(2) $230 million n/a

CO2 Emission Savings Per Year(2) 3 million tons n/a

Cost Per Mile(3) $8 million for 5 GW pipe$13 million fully redundant

$9-10 million minimum

Per

form

ance

Sit

ing

Co

st

(1) Cooling and converter stations for DC cable; line and substation losses for 765 kV.(2) Based on generation cost of $0.065 per kW-hr and a 100% load factor.(3) $13 million per mile cable cost based on fully redundant system. 765 kV cost does not include rebuild of underlying grid.

Superconductor Electricity Pipelines:Superconductor Electricity Pipelines:Lots of Power, Out of Sight and Out of Harm’s WayLots of Power, Out of Sight and Out of Harm’s Way

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