It is all about resistance folks. AC had a real edge while power was pumped through metal wires. We arenow entering the age of the super conduction transmission line and zero resistancebetween source and need thousands of mile apart is just too compelling anargument and that is why even direct current trunk lines are going in even ifthey are not super conducting just yet.
I recall how blind the Telcos were to the real impact of fiber optic transmission.
The installed base is AC for both legacy and safety reasons and I seelittle reason to change any of that soon. Everything else will be better handled with direct current solutionsthat are obviously coming.
What this means is that the power companies will have a huge increasein available power for sale. I like tosuggest double, which is inaccurate but in the ball park.
WillSolar, Wind and New Tech Pave the Way for a DC Renaissance?
HighVoltage Direct Current (HVDC) lines offer a big opportunity for developers.
HERMANK. TRABISH: DECEMBER6, 2010
The permitting, sitingand financing obstacles to the building of new transmission lines in the faceof NIMBY (Not In My Backyard) and BANANA (Build Absolutely Nothing AnywhereNear Anything) activists are familiar. But Aftab Khan, Vice President andGeneral Manager of
Grid Systems for multinational engineering giant ABB, sees anew game afoot. U.S.
Khan has watched theold game since starting at ABB 18 years ago. “A lot of what we would do forutility customers or transmission companies was to evaluate what the bestsolutions were for them,” Khan said, “both AC and DC.”
The latenineteenth-century War of Currents pitted George Westinghouse and alternatingcurrent (AC) against Thomas Edison and direct current (DC). Because electricitywas then primarily delivered over short distances to consumers from nearbypower plants, Westinghouse and AC won.
But DC is the key to the new game. “Poweron a DC line is completely controlled. If you say, ‘I want to bring power frompoint A to point B and I want exactly this many megawatts on that line,” Khansaid, “the power goes.” Theoretically, he added, AC lines can do the same. Butin an AC system, “you don’t have the ability to manage the power flow frompoint A to point B directly.”
The new game ispossible because transmission systems around the world are adding renewables.Vast renewable resources -- be they North Sea and
winds or Saharan and Mohave solar --are being developed far from population centers and transmission systems. “Youhave a lot of wind capacity in the Midwest and into Texas , and you have a lot of load going outto the West and to the East,” Khan noted. “DC makes perfect sense. Point A topoint B, send X number of megawatts that way. It achieves exactly what you needto do.” Texas
Semiconductors andadvances in electronics have also paved the way for high-voltage DCtransmission.
ABB built the first200-mile, 100-kilovolt, 20-megawatt DC line in
in the 1950s. There are now,Khan said, more than 145 working or pending HVDC projects worldwide (and HVDC line manufacturer ABB is involvedin more than 70 of those projects). Few are located in the Sweden -- so far. U.S.
Meanwhile, others suchas
Power Systems and Nextek Power Systemsare devising equipment that convert AC power to DC for use in data centers orbuildings. How popular is the concept? Nextek recently hosted delegations fromChina, Singapore and Japan, said Lian Downey, director of digital applicationsfor the company. With DC coming straight from HDVC lines, efficiency would beincreased even more. Valdius DC
"We are living ina DC world. Everything that uses electricity internally users DC power,"she said.
China built a 1,200-megawatt capacityDC project in the late 1980s to deliver remote hydroelectric power to burgeoningurban populations. Earlier this year, ABB and Chinese partners “completed andcommissioned” an 800-kilovolt, 6,400-megawatt capacity line in
. Thecountry has really pushed the technology, Khan said. “They’re building more andmore of these HVDC lines to access more and more of their remote generationresources.” As a result, Chinese transmission developers have joined ABB,Siemens and Alstom Grid as the most important handlers of HVDC transmission. China
The cumbersome U.S. transmission development processallows for more stakeholder input, Khan noted, and the thrashing out of issuessuch as whether new transmission might be a vehicle for more fossil fuelgeneration (Khan believes it will not). But delays leave remote renewableresources stranded. The new game, Khan thinks, can resolve the conundrum.
is doing is, they’re investing 5billion dollars or so in transmission infrastructure that goes out to the middleof nowhere,” Khan said. “The logic is that if the wires are there, into thesehigh wind areas, then a wind developer will say ‘OK, all I need to do isfinance the development of my wind farm and I can connect in and sell thepower.’” Texas
solution ofpre-identifying Competitive Renewable Energy Zones (CREZs) into which newtransmission can be built may not work elsewhere. Texas ’ own big population centers consumeits wind-generated electricity. Midwestern winds need to be delivered across many state and regional regulatory borders.That’s where the new game comes in. Texas
Two-line HVDCtransmission systems are less expensive than three-line AC systems and incurfewer instances of line loss to resistance. There is,however, an added expense due to the need for power converter equipment. Overlonger distances, however, the benefits outweigh the costs. “It’s such acomplex calculation,” Khan said, but “if you’re going over a couple of hundredmiles, you should consider DC.”
Another advantage ofHVDC lines, significantly simplifying the siting process, is they can be builtunderground or underwater over distances with little line loss, whereas “withAC lines, you don’t get much out of the other end” if you use these kind ofnon-traditional sites.
HVDC systems are nowbeing proposed and initiated by entrepreneurial transmission developers such asClean Light Energy Partners, Transmission Developers, TransWest Express, and aGoogle-led consortium, Khan said. “They’rewanting to develop long-haul transmission lines,” despite the necessity of“crossing multiple state lines and multiple jurisdictions,” whereas “thereisn’t any existing transmission company that would ever want to do that.”
With the marketadvantages of HVDC, developers “can actually build a business case around it.Because they have complete control of power on that line, they can sign up winddevelopers on one end” and “they can sign up a utility on the other end to buythe power.”
Players in the new gamehave -- for now -- won a major blessing from the Federal Energy Regulatory Commission (FERC).“Traditional transmission is cost-based,” Khan explained. FERC is giving thenew transmission entrepreneurs “the right to negotiate rates on their line.”
Khan sees the new gameas “really exciting, and something they don’t do in
.” Though controversial andnot without hurdles, he said, “DC has opened up an opportunity that wouldn’thave existed otherwise.” China
Michael Kanellos contributed to this article.