|
Study investigates small scale HVDC Preliminary results out from phase II look at whether 1 MW high voltage direct current transmission would work for rural areas Kristen Nelson Petroleum News
The Denali Commission has funded two phases of a study looking at whether high voltage direct current, HVDC, transmission would work for small Alaska rural communities, those which need about 1 megawatt of electricity.
Jason Meyer, emerging energy technology program manager for the Alaska Center for Energy and Power, ACEP, at the University of Alaska Fairbanks, told the Anchorage Association for Energy Economics at a Nov. 5 meeting that this isn’t the big backbone project that’s been discussed to use North Slope natural gas to generate electric power which would be transmitted to Interior and Southcentral Alaska via HVDC.
It isn’t even the size of project would take power off the backbone line for major communities.
“We’re on the other side of that sector,” Meyer said. “So you have the trunk, which is the backbone project, branches (to the) larger hubs, and then we’re the twigs.”
HVDC As Meera Kohler, president and CEO of Alaska Village Electric Cooperative and Robert Jacobsen, Ph.D., vice president, science and technology for Marsh Creek LLC, said in presentations over the summer, HVDC is used to take massive amounts of power long distances, and the transmission lines for HVDC are much cheaper than AC alternating current lines.
But there is a big expense — at both ends of the line, converter stations are required to take AC generation and put it on the HVDC line and then take it off and put it into the grid at the other end.
HVDC hasn’t been considered economic for distances under 300 miles based on economics, but because of environmental and right-of-way issues today, it has become economic well under 300 miles.
Two goals Meyer said the project ACEP is managing has two goals: developing low-cost small-scale HVDC converter technology, and developing innovative transmission infrastructure.
Meyer said the scale needed for rural Alaskan communities is megawatt-scale.
That’s compared to large commercial-scale technology in use to move large quantities of power across long distances —currently in use in China and the Lower 48.
While technology is available for the large projects — in the size range from hundreds to thousands of megawatts — and even for the medium-sized projects, from tens to thousands of megawatts, “there is no commercial technology available for anything under that (mid-sized scale); so if you’re looking at a megawatt there isn’t anything available.”
Phases of project Phase I of the project, completed in 2009, evaluated the technical feasibility of HVDC converter technology. That project, also funded by the Denali Commission, was managed by the Alaska Village Electric Cooperative.
In that phase, Princeton Power did preliminary estimates on the breakeven point for HVDC costs and found that lifecycle HVDC costs were projected to be lower than alternating current lifecycle costs for overhead interties longer than about 10 to 23 miles, Meyer said.
Phase I developed a prototype that worked, he said, and in phase II a demonstration-scale prototype was developed, with converters to laboratory engineering scale.
Polarconsult, the project lead, also “identified some innovation in actual transmission line infrastructure that they felt would be relevant,” specifically fiberglass poles, which would allow poles to be spaced farther apart, and also provide a transportation cost savings.
Phase II, with full-scale prototyping, was completed in May and a preliminary report is out, with the final report expected by the end of the year.
Converter demonstration Meyer said the scale of the converter — to convert AC to DC power and back again at either end of the transmission line — is about 1 megawatt, which he described as the general size appropriate to a lot of rural Alaska communities.
The demonstration went OK, he said, and showed the system could be brought up to full voltage but said there were some issues in the design and actual layout. They aren’t major flaws, he said, but will require some tweaking of the system to make it work appropriately.
But, he said, it’s not turnkey, “you can’t bring this up here today.”
Polarconsult has installed one of their prototype fiberglass poles in Fairbanks and will monitor it for a couple of years. He said there are concerns with maintaining wires on a fiberglass pole and also cold-weather concerns.
Funding sought Meyer said Polarconsult is seeking phase III funds for an Alaska-based laboratory and field demonstration of converter units. He said that stage would involve bringing finalized converters to Alaska and doing laboratory and field demonstrations.
The general findings, he said, are that HVDC is a mature and stable technology, but power scales on which it is currently available are much too large for small-scale Alaska applications.
| 