Direct current (DC) transmission lines date back to 1882, but went out of style in favor of alternating current (AC). That has once again changed with at least 660 MW of load demand in New York alone powered by DC, which is twice as efficient as AC.
Although AC transmission still dominates the industry overall, growth in electricity demand and congestion and instability of the grid are currently driving high-voltage (HVDC) transmission, which allows interconnection of regional systems that operate asynchronously, mitigating many instability issues that otherwise would cause outages in AC transmission. Further, innovative developments in HVDC transmission, such as voltage-source converters (VSC), are alleviating some doubts.
Interest in VSC has taken off, and Navigant Research forecasts a growth in demand for this technology, with global cumulative HVDC converter revenue of $56.6 billion between 2013 and 2020. Worldwide, 110 new HVDC lines are planned or under construction and will be completed by 2020, according to Navigant.
Also driving the expansion is the increasing need for integration of new renewable resources, particularly offshore wind power with utilities implementing aggressive plans for offshore wind development.
“Approximately 333 GW of new HVDC transmission capacity will be added between 2013 and 2020, including nearly 200 GW in China alone,” said Kristoffer Torvik, senior research analyst with Navigant Research