[E&E seminars] November 19 - Continental-Scale HVDC Grid Based on Massive Metallic-Conductor Electric Pipelines

[Jameson Twomey]

Continental-Scale HVDC Grid Based on Massive Metallic-Conductor  
Electric Pipelines

Roger Faulkner and Ron Todd of Electric Pipeline Corp.

MIT Laboratory for Electromagnetic and Electronic Systems (LEES)  
Colloquium

Nov. 19, 2009
4:00 PM
MIT Room 32-144

By its very nature, a continental grid must link asynchronous AC  
areas; for this and other reasons it is desirable for any such grid to  
be DC. This lecture considers HVDC continental scale supergrids based  
on massive underground conventional metallic conductors (aluminum or  
sodium) which are too large to be installed as wires or cables. One  
can imagine busbars similar to those used in power plants or aluminum  
factories for example as conductors, but our preferred designs are  
underground or partially underground electric pipelines (elpipes),  
with polymeric insulation. This lecture concerns a proposal to the MIT  
LEES Laboratory to participate in an ARPA-E proposal to look at many  
aspects of an elpipe grid, such as:
Insulator behavior and reliability under high voltage DC stress
Semiconductive films and surface treatments on insulators
Electric field management
Mechanical and electrical stress management in materials seeing  
thermal gradients
Low cost, fail-safe heat transfer
HVDC circuit breakers & methods for fail-safe redundancy
Magnetic shielding options
Insulation degradation detection
Interfacing elpipe grid node points with superconducting lines at high  
voltage

The concept of elpipes to form a continental grid is being promoted by  
Electric Pipeline Corporation (EPC), a clean tech startup venture.  
Certain EPC inventions cannot be disclosed yet, due to patent  
considerations, but this lecture will discuss  design trade-offs on  
such a conventional elpipe, including design voltage, conductor  
selection, methods to make splices, alternative means to remove waste  
heat, and thermal expansion joints.

Theoretically, cost of conventional aluminum conductor + polyolefin  
insulator would be minimized for an elpipe between ±2-3MV (minimizing  
cost of conductor, insulator, and converter stations). However it took  
more than 10 years to go from a proven ±500kV design to a proven  
±800kV design for HVDC/AC converters. We have therefore conservatively  
adopted ±800kV as the design voltage for elpipes.

In a typical transmission project, the purchase price of the  
conductive metal per se is less than 2% of the project cost. Elpipes  
are massive by comparison, using up to 200 cubic meters of aluminum  
per km; conductor per se can represent up to 25% of the project cost.   
Among the conventional conductors, copper is about 7.7 times more  
expensive than aluminum on an equal conductivity basis, and aluminum  
is about 5-7 times more expensive than sodium (the least expensive  
feasible conductor). Aluminum is favored for initial designs of the  
elpipe, with the possibility that the hollow conductors can later be  
filled with sodium to further reduce electrical resistance. Heat  
transfer is a critical issue for any high power underground non- 
superconductive power line; we will show that it is feasible to design  
passively cooled electric pipelines up to about 40 GW, and above that  
one must use active (non-cryogenic) cooling.

The needed power generation capacity in the US would be greatly  
reduced if all generators and users could share power; the capital  
savings could pay for a continental scale grid. Considerable attention  
and research funding has been given to the "superconducting supergrid"  
option, which most experts agree cannot be implemented sooner than  
several decades into the future due to the need to meet US reliability  
standards. This lecture looks at a technologically simpler, yet still  
challenging alternative technology. The conventional HVDC supergrid is  
robust, and mechanically simpler than the superconducting grid, and it  
appears feasible to prove reliability sooner than is feasible for a  
superconducting grid. The hybrid design is interesting because the  
robust, relatively simple elpipe-based HVDC supergrid design can be  
augmented by a superconductive grid that only needs to connect to the  
elpipe HVDC grid at a few points, yet these few superconducting links  
would greatly improve the efficiency of coast-to-coast transmission.  
In this instance though, the reliability of the superconducting links  
need not be as high as would be the case if they are the only  
connections; the hybrid design also has hybridized reliability &  
efficiency.


Roger Faulkner is the founder of Rethink Technologies, Inc. ( www.rethink-technologies.com 
  ) and is a polymer scientist who studied at Akron University. His  
Ph.D. research was on one of his inventions, reaction wave  
polymerization, and most of his 30 year career since then  has had to  
do with pursuing and developing this and other inventions, not all in  
the area of polymer science. He has a strong scientific/technical  
interest in enabling technologies for renewable energy, including  
development of a long distance multi-terminal HVDC grid based on  
“electric pipelines” (which is the basis of Electric Pipeline  
Corporation). He has also had a strong interest in energy policy  
issues for many years, and was a full party and public intervenor in  
the Wisconsin PSC’s Advance Plan 6 hearings in 1991, where he first  
introduced the concept of HVDC pipelines in testimony he presented  
with Professor Willis (Bill) Long of UW-Madison, a leading expert in  
HVDC power transmission. Since November 2008, Faulkner has been  
pursuing the concept of HVDC electric pipelines (elpipes) as a  
business startup/spinout from Rethink Technologies, Inc.

Ronald Todd is a technologist and a serial entrepreneur, having been a  
founder of and managed 7 high-tech companies.  These have been in the  
areas of instrumentation, computing, automated test, electronic  
imaging, housewares, utility-scale solar energy balance-of-system, and  
now underground electric power transmission.  Additionally he led a  
100 person electronics and software consulting firm technically, and  
set up and ran a 50 engineer telecommunications IC design center.  He  
is the co-founder and CTO of Electric Pipeline Corporation, and has BS  
and MS degrees in Electrical Engineering from MIT.
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