By Teresa Hansen, Editor in Chief
High voltage direct current (HVDC) isn’t new. Direct current transmission lines have been successfully transmitting electricity since the 1950s. In fact, records of experimental use of HVDC date back to the late 1800s-the time when Thomas Edison, George Westinghouse and NikolaTesla, as well as other innovators in North America and Europe were “debating” the use of alternating current (AC) vs. DC for electricity delivery.
Countless industry experts have said over and over in the past few years that if Edison could see today’s grid, he would surely recognize it because it’s changed little in the last century; that, however, might not hold true anymore. Edison might be surprised and pleased to see that the technology for which he advocated so vehemently is now considered a viable option for moving large amounts of electricity over long distances and is being built out across the globe.
The rise of HVDC is due in large part to the growth of wind energy and large hydro power projects, coupled with the electrification of Asia and other countries throughout the world that are just now building out their electricity infrastructure.
When asked why DC is a better choice than AC for some transmission systems, Michael Skelly, founder and president of Clean Line Energy Partners, said DC offers more efficient delivery.
“Basically this is a complicated electrical topic,” Skelly said. “What happens with very long-distance AC line is your losses are higher and the voltage sags, so you get into reactive power and real power.”
Clean Line Energy is an independent developer of North American transmission lines designed to “deliver thousands of megawatts of low-cost renewable power from the windiest areas of the United States to communities and cities that have a strong demand for clean, reliable energy but lack access to clean energy resources.”
Although long distance HVDC is more expensive to build than HVAC, it ends up saving the operator money over its lifetime because it is more efficient and reduces losses. Clean Line Energy’s website explains that less energy is lost on DC lines as it is transmitted and there is no need for reactive compensation along the line. DC flows steadily through the wires without changing direction many times each second and through the entire conductor rather than at the surface, according to Clean Line Energy.
As more HVDC transmission projects are planned and developed, the concept of supergrids is being discussed and advocated around the world. Navigant Research released a report on Oct. 6 that predicts global supergrid investment will increase from $8.3 billion in 2016 to $10.2 billion by the end of 2025.
For its research, Navigant defined a supergrid as the transmission network required to transport high volumes of power across long distances in order to optimize resource use, improve operational efficiency and integrate renewable power from remote regions where the resource potential is strongest.
“The supergrid concept suggests a network of HVDC transmission systems that are strategically designed and implemented to maximize efficiency and tap into the best available renewable resources,” said Jessica Lewis, senior research analyst with Navigant Research who worked on the report. “This can be at a national, continental or even global scale. The HVDC projects we’re seeing now tend to be one-off projects, as opposed to carefully planned networks of projects. But with time and additional investment, they could eventually mesh into a network that functions like a supergrid.”
Supergrid advocates claim these grids will enable the integration of renewable power on a bulk scale.
Europe was one of the first to propose a super grid in 2009. The aim was to create an HVDC network that would span not only the continent but also connect it with northern Africa to move solar and offshore wind energy across the Mediterranean Sea into Europe.
An organization called Friends of the Supergrid was created to help make the European proposal a reality. It describes the supergrid as “a pan-European transmission network facilitating the integration of large-scale renewable energy and the balancing and transportation of electricity with the aim of improving the European market.”
“Friends of the Supergrid originally advocated a carefully planned HVDC supergrid across the entire continent, but they’ve since dialed back their expectations,” said Lewis. “They’re still advocating for the supergrid but recognize it’s likely to emerge more gradually as a combination of HVDC lines planned and built as independent projects.”
Europe might not be on the way to developing a pure supergrid, but it does have some things going for it, according to Lewis.
Europe is largely driven by a fairly unified energy policy and the desire to cut carbon emissions. In addition, Europe already has interconnection standards in place, she said.
The European Commission set a target of 10 percent electricity interconnection by 2020. This means that every European Union (EU) country should have electricity cables in place that allow at least 10 percent of the electricity it produces to be transported across its borders to neighboring countries. According to the European Commission, 22 EU countries are on track to reach, or have already reached, the target. In 2014, the European Commission suggested extending the 10 percent electricity interconnection target by 2020 to 15 percent by 2030, but this is still just a suggestion that is being studied and is not yet a requirement.
Supergrids in China
“Because China is in the midst of electrifying and also has the political will and financial means to invest in major infrastructure projects, it is probably in the best position to build a supergrid,” Lewis said. “Its load centers are concentrated in the south and east of the country while its renewable generation sources are largely concentrated in the north and west.”
Skelly also believes China is farther along than the rest of the world, especially the U.S., when it comes to developing HVDC transmission infrastructure.
“I would say China is way ahead of the U.S. electrically. Partly because its (infrastructure) is a lot newer and more modern,” said Skelly. “Their grid is dramatically more efficient and newer and more modern than the U.S. grid. And, HVDC is a big part of it.
“What you get with the Chinese grid are more choices. When the Chinese build a grid, they receive access to coal, hydro, wind and solar. That interconnection gives them options that we don’t have,” he said. “China is heavily focused on building infrastructure. When you look at Chinese airports and trains and grids and ports, they’re just way ahead of us.”
In September 2011, the Asia Supergrid was conceptualized. China, Japan, Mongolia, Russia and South Korea are the possible participants that would work together to create a supergrid to link the countries. The grid would maximize the use of renewable energy by taking advantage of diversity in loads and resources. Wind energy generated in Mongolia could be transmitted to Japan, through China and South Korea via undersea transmission cables, and hydropower generated in Russia could be delivered to Japan and other nations. Utility/grid operators representing four of the five countries (Mongolia was not represented) signed a memorandum of understanding in Beijing in October agreeing to conduct technical and economic feasibility studies toward creating the Asia Supergrid in northeast Asia.
Although renewables are a major driver of HVDC development, there are also gains to be made by establishing larger transmission markets, said Navigant’s Lewis.
“Integrating regions with different time zones and climate patterns can reduce the overall capacity requirements of the system,” she said. “It can also mitigate some of the challenges associated with the intermittency of wind and solar power. If the wind stops blowing in one area, there’s a good chance it will still be blowing somewhere else.”
There are many benefits, at least in theory, to the creation of supergrids. There are, however, some challenges.
“Building a supergrid at any scale would require significant political support, and in most cases, it’s just not there,” said Lewis.
She said there are three main challenges: Regulatory, political and financial.
“Internationally, you would need to develop harmonized grid codes and standards if a supergrid was ever going to work,” said Lewis. “And, you would need to build consensus around rules governing electricity trade.”
Ensuring security of supply is another major concern, said Lewis.
“Energy security is traditionally a matter of national concern. Some countries will inevitably hesitate to integrate their infrastructure with others or trust others to provide power reliably under all conditions and circumstances,” she said.
Obtaining financing for any large infrastructure project is difficult, but especially so for a large multi-state or multi-country transmission line. In addition, high up front cost is also a challenge for developers.
In China, HVDC is being developed in higher voltages than anywhere else. The technology is evolving, which is causing the price to come down, but it is still more expensive than HVAC. The cost of conversion is also high, but is coming down, too. Decreasing cost will facilitate more HVDC projects.
Lewis pointed out that because HVDC conversion is complicated from a technology standpoint, the technology vendors like ABB, GE, Siemens and others must be heavily involved in HVDC projects.
Supergrids and the U.S.
Because the U.S. is a patchwork of complex regulations and state jurisdictions, Lewis said it is unlikely that a supergrid will be planned in North America. In addition, the U.S. has a mature grid, growing distributed energy resources and flat energy demand, which will remain flat or even diminish as demand response and energy efficiency programs grow. It is the opposite of China, where regulations are consistent, energy demand is growing and the country is electrifying.
That’s not to say that HVDC is not growing in the U.S.
“Clean Line Energy is at the vanguard of HVDC transmission in the U.S.,” said Lewis.
Skelly would agree. His company is close to beginning construction or in the final stages of licensing five U.S. transmission projects, four of which are HVDC projects. Three of those HVDC projects will move wind energy from the Great Plains to load centers further east and the fourth will move wind energy from the Southern Plains west. A line in New Mexico, the Western Spirit Clean Line, is a shorter AC line.
While these projects are not supergrids and aren’t likely to be, Clean Line Energy is open to the concept.
“If there was a U.S. supergrid, we would definitely be part of it,” Skelly said.
Not only are no supergrids being planned or built in the U.S., so far none are under construction anywhere on the planet and none are expected soon.
“Super grids will most likely emerge gradually as a series of projects,” said Lewis. “The process will take decades.”