to: Professor Rajeev J.Ram (December 15, 2010):
My associate, Rob Karnes attended the ARPA-E session at MIT today and discussed our underground HVDC transmission concept with David Shum, who indicated that you are the guy with whom to bring this up within ARPA-E. I emailed you previously, but got no response (August 18, 2010); so I'm trying again now. The attached two papers give a general description of elpipes, and explain how it is possible and practical to go to power transfer levels >12 GW. The two abstracts for upcoming papers give a better sense of where we are today, and what we are working on. I applied for ARPA-E funding twice so far, FYI. I look forward to a funding opportunity that specifically addresses long distance transmission.
I am most interested in the high-power end of the smart grid. An HVDC grid is required, in my opinion, to enable continental scale power sharing. The voltage could be 500-800kV but I personally favor 800kV, as this is effectively the new standard due to the two recent Chinese overhead 800kV DC projects.
I have been promoting polymer-insulated electric pipelines that I call "elpipes" for a few years, and have published both magazine articles and scientific papers. Elpipes are one piece of the puzzle but equally important and needed are these innovations:
1) development of HVDC breakers;
2) development of control strategy
3) extending voltage source (VSC) converters (GTOs and IGBTs) up to 800kV
4) developing an HVDC-HTS (high temperature superconductor) junctions that can operate at 800kV.
An HVDC grid can bridge between different synchronous areas. Only an HVDC approach can cover a continental area with a single supergrid. My calculations show it is feasible to move 12 GW through a fully buried line, or 24 GW through a line mounted at the surface (to allow reliable radiation of waste heat away from the conductor). With internal (not cryogenic) cooling, such a line could even go to 200GW economically (I realize that could only be allowed if there are redundant circuits).
My approach to allow high capacity underground transmission is very simple in principle: use enough metal to reduce resistive heating below that which can be removed passively. Sort of a "brute force" method based on high efficiency transmission (1% loss per 1000 km is about the "sweet spot" in the design space of elpipes; about one third as lossy as the best available overhead lines). This causes the fraction of the total transmission budget spent for conductor per se to increase from less than 1% to about 12%...not a budget buster.
I envision a future HVDC grid with mostly line commutated converters (LCCs based on thyristors), but with enough fast acting IGBT-based VSCs interfaced with fast storage capacity to allow fast balancing and black start capability. Most power exchange would be handled by power sales through pairwise deals between two stations attached to the grid. Station A would make a deal with station K (for example) to transfer a certain amount of power (actually, the deals must be denominated in amperes rather than watts to simplify load balancing on a multi-terminal DC system). IGBTs keep the global HVDC grid in balance, and do voltage support if needed.
I have found though that this vision is "too big & too long term" to be conventionally financeable; though I would point out that elpipes are a lot more likely to work than some other things DOE has funded. The basic technology and physics are all known, but it would be a mistake to think this approach is so obvious that it can be left to private industry. Because of the difficulty of funding elpipe development directly, I am probing to see whether I can use my HVDC breaker concept to get some preliminary funding flowing (see abstract for IEEE Electric Ship Technical Symposium). I have been working with Professor Markus Zahn, and many other notable experts, though I am still very much pre-funding. If you have time, I'd like to meet you.
Roger Faulkner, President
Electric Pipeline Corporation
(Rajeev Ram’s primary focus at ARPA-E is in advanced electrical components and systems ranging from transportation to the generation and transmission of electric power.)
Note: Rajeev Ram wrote back to me January 29, 2011 and I met him at MIT February 14, with Ron Todd. One thing he said he was frustrated about is the lack of good cost data on HVDC gas insulated lines (GIL). Insofar as GIL is really the only competitive technology for really large scale, very long distance transmission of 30 GW through a single pair of metallic conductors, I too would like to see a full-blown ground-up cost comparison between GIL and elpipes, and I tried to include this in my recent ARPA-E application. Mel Hopkins from AZZ CGIT Division (the leading US supplier of GIL) was on board if he could get management approval from AZZ (but he could not).
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