Making renewable energy cost effective and technically efficient compared to existing power stations is a make or break issue for renewable technology. This is because governments can't cross subsidize renewable technology forever. Governments change their energy policies and related energy cross subsidization programs. One indicator of such large scale policy changes (or reversals) is the mass exodus of major carbon emitting countries away from the internationally agreed Kyoto agreements and others.
The above explanation from Siemens of more efficient renewable energy transmission is highly technical. There is no way to escape that. Solutions for renewable energy will always be a complex mix of economic, scientific/technical and political issues. What I call "green faith" or morality doesn't come into it.
Separately from http://www.greentechmedia.com/articles/read/the-secret-to-hvdc-mega-grids-abb-unveils-hvdc-circuit-breaker November 9, 2012, see below:
The Secret to HVDC Grids: ABB Unveils HVDC Circuit Breaker
High voltage direct currents could go from superhighways to resilient grids.
Katherine Tweed: November 9, 2012
ABB, which has been delivering power over high voltage direct current for more than 60 years, has solved an engineering puzzle that has been around as long as HVDC.
The power automation giant just announced that it has cracked the code on building circuit breakers for HVDC power lines. The development allows for extremely fast mechanics with power electronics. In this case, the enormous amounts of power that are moving over HVDC lines can be interrupted within five milliseconds.
Currently, HVDC lines are widely used to move power across huge distances, because DC is more efficient across long spans than alternating current. The technology is particularly key for renewable projects, such as offshore wind farms, which are often far from city centers where most of the power is used.
“This historical breakthrough will make it possible to build the grid of the future,” Joe Hogan, CEO of ABB, said in a statement. “Overlay DC grids will be able to interconnect countries and continents, balance loads and reinforce the existing AC transmission networks."
China is heavily investing in HVDC, as is South Korea. In China, HVDC will make up 40 percent of the country's 300 gigawatts of new transmission capacity, according to GTM Research in its recent report, The Smart Grid in Asia, 2012-2016: Markets, Technologies and Strategies.
In Europe, HVDC is being used to link offshore wind power in the North Sea to northern Europe. But that might be just the beginning, said Thomas Schmidt, spokesperson for ABB.
He noted that wind power from Scotland could come into mainland Europe, along with hydro from Norway and solar from the Mediterranean region and North Africa. “It's a very simple thought: to use the ultra-efficient transmission plus the advantages of a grid,” he said. “Until now, that wasn't possible because of the risk that you couldn't isolate any fault.”
The technology uses semiconductor switches on each side of a mechanical switch to isolate up to 1 gigawatt of power that might be flowing over an HVDC cable. “The challenge was to break this in a controlled way,” said Schmidt
ABB wouldn't say just how long it had been working on this project, but the company spends about $1 billion annually on R&D, and Schmidt described this as a “flagship” project.
ABB is also busy in the Americas, updating the Oklaunion link in American Electric Power's territory and installing a 2,500-kilometer HVDC highway to power São Paulo, which will be the longest in the world. There are also dozens of offshore wind projects being proposed across the U.S. that would likely be linked by HVDC.
The next step will be a pilot project, which will take place in about eighteen months.