Direct Current Microgrids: DC Proponents Say It’s the One Direction to Go
The world we’re wired into is an alternate universe.
We don’t mean space-time continuums or matrices. Speaking electrically, of course, our modern consumption is mainly wired for alternating current as opposed to the direct current that dominated at the beginning of the power grid era in the late 19th century.
Direct current was more efficient at higher voltages, but alternating current was easier to step voltages up or down via transformers.
So, Nikola Tesla’s AC innovation won the war and has been the electrical infrastructure’s main mode of transportation over the past 130 or so years. Direct current was doing big work, but mainly on high voltage transmission lines outside the U.S. and in isolated projects.
DC isolation, however, is becoming a thing of the past in this era of energy transition. The devices rising to the top of the modern and future economic and technological food chains are almost all DC, such as computers, solar cells, electric vehicles, batteries and fuel cells.
Inverters not required
Many industry experts increasingly contend that the future of a clean energy economy must rely on the three Ds: distribution, digitalization and direct current. They also believe that the decentralization of the macro power system will require more and more DC microgrids.
“DC is better” in many applications, noted Marija Vujacic, Hitachi Energy’s global product manager for energy storage and grid edge solutions. “There is less need for conversion for DC to AC and back.”
AC/DC are the ying and yang and they both have their strengths in certain situations.
Direct current, Vujacic added, "has significant merits, but it is not always the best option. Hitachi Energy continues to explore the benefits of DC concepts as well as hybrid AC and DC solutions."
Vujacic, like energy transition entrepreneur Vic Shao and others, believe that inverters—those tools that do the shifting of DC to AC and so on—are a primary point of dysfunction in efficient energy utilization. The complexity of inverters also is hindering interconnection processes, which often delay clean energy projects for a year or more.
In other words, focus on DC and avoid the muss and the fuss. Current moving in one direction, to quote musical legends One Direction, is “Perfect” ... or nearly so. Proponents are certainly singing its praises.
“Having current flowing in one direction, you can reduce the losses through the overall process,” Vujacic pointed out. “With distributed energy, it also means locations are shorter and transmission is also shorter, hence less losses.”
Accelerating the future of e-mobility
Alternating current on transmission systems can result in 7% or more losses in electricity, according to reports. A study by California’s Department of Energy, reported by Stanford University, estimated that resistive losses through AC transmission cost about $2.4 billion in wasted electricity in 2008.
AC proponents also note that DC has its share of line losses, too. But in the case of microgrids, or on-site power close to the load, direct current simply makes more sense.
“I’m convinced, whether it’s a microgrid or off-grid or a DC grid, that these solutions are necessary,” Vic Shao, the man who helped found startups Amply Power and Green Charge Network and now is undertaking his latest company, DC Grid, said in an exclusive interview with EnergyTech earlier this year.
“With 90% efficiency [from direct current], the need for AC no longer is necessary,” Shao added. “Solar is DC-based, computers, cell phones and EV charging—all DC-based consumption. What is the main failure point in solar? It’s the inverters,” which are only there to convert DC to AC.
Electric utilities — the gatekeepers of alternating current — are scrambling to contend with this relentless challenge. Having anticipated flat load growth only a few years ago, the utilities are now seeing a sustained surge in power demand from new data centers and EV charging infrastructure. Even some commercial and industrial companies working toward fleet electrification, such as Costco, are pursuing off-grid solar and/or battery storage microgrid-type installations to power charging stations.
And off-grid means mainly direct current. DC is A-Ok for accelerating the future of e-mobility.
Feeling the need for speed in off-grid power
Electrification infrastructure giant ABB certainly thinks so. Swiss-based ABB is now partnering with iconic American race car league NASCAR to help decarbonize company-owned speedways with more efficient LED lighting, HVAC and, eventually, on-site solar, battery storage and perhaps even microgrids.
Those LEDs, solar cells and batteries are direct current, so developing a DC ecosystem not only is logical, but it makes financial sense.
“You can save costs in wiring by DC,” which only needs two conductors compared to AC’s three, said Amber Putignano, EV ecosystem market development leader at ABB.
Putignano is working intently with NASCAR on its goal to achieve net zero emissions by 2035.
“With on-site battery energy and DC, you can eliminate a few different steps” to make the charging flow more freely, Putignano added. “The efficiency gain is there to see the benefits.”
Eventually, ABB might even help NASCAR electrify its transport trucks by utilizing megawatt-level charging stations. This would be a mammoth undertaking requiring several years of transition in equipment and infrastructure, but NASCAR owns a dozen or so of the racetracks on its circuit and has the capital and patience to make it happen.
“With ABB we’ll look at microgrids,” said Riley Nelson, head of sustainability with NASCAR. “There’s an opportunity for using renewable energy in different use cases, such as microgrids and on-site power. . . We would consider nearly everything.”
ABB’s Putignano and her team understand that alternating current still rules the power lines and the megawatt charging system might be forced to start with AC. Over time, though, the advantages of DC for microgrids and on-site generating assets will rise into prominence as projects such as EV infrastructure grow.
“It’s going to take a little time,” she said. “AC is a cost that people can accept right now, then we have to innovate and evolve.”
Panels and switchboards are AC, so that’s that. The first megawatt chargers at NASCAR sites are maybe two years away, and then the innovation moves faster than Joey Logano’s No. 22 car.
“We’ll start with megawatt charging, making sure the connection is safer and bigger,” Putignano noted. “We’ve got to have huge power, and MW charging is currently available in AC. Over time, the efficiencies will become obvious with DC.”
Sometimes even the most direct journey takes alternating pathways.
