THE DC-POWERED BUILDING
AC current has been the dominant electric current since the late 19th century, with its rival, DC, used primarily in batteries for powering mobile phones and torches, as well as flat-screen TVs (converted from AC) and hybrid and electric vehicles. But as the established electricity grid continues to age, designers of smart, eco-friendly buildings are seeing direct current as the future.
This was the core argument of Brad Koerner’s presentation at the Smart Building Conference during ISE 2020, The DC-Powered Building. Koerner, VP of Product Development and Innovation at design technology company Cima as well as Principal of Koerner Design, laid out his case by stating that that a “revolution in electricity” was needed “before a lot of smart buildings were impacted” by the limitations of the grid as it is now.
The landscape, Koerner argued, was now changing rapidly in favour of DC; more solar panels were being installed on buildings because of price parity with existing solutions and battery prices continued to “plummet”. Increasingly, he said, the infrastructures of commercial premises were being converted to DC, with the LEED (Leadership in Energy and Environmental Design) certification programme actively promoting the transition. As part of this, LEED’s new pilot credit scheme is encouraging people to make energy savings by switching to DC power systems.
“Forbes magazine estimates that by 2030 over half of new electricity connections will be off-grid,” Koerner said. “Firms are getting more concerned about grid resilience and are starting to turn it off. The grid is becoming more creaky as it ages and there are also pressures to de-carbonise business and domestic activities.”
The ongoing debate about climate change, Koerner observed, was driving organisations to “seek control” over both their energy management and reputation. As more devices “behind the meter” – in other words, inside the building – are DC-compatible, including sensors, lighting, HVAC and data centres, as well as charging for electric vehicles, Koerner said the pressure was on for the grid to become DC as well.
“Because AC is 240V, the whole system has to go through a conversion process, which calls for a lot of what is really unnecessary hardware and throws away a lot of energy,” he explained. “About 15 percent of a net zero building goes on converting AC, which is wasteful and dumb.”
By using digital solid-state circuits to replace circuit-breakers and relay switches, it was possible to have a more precise flow of power with no in-rush current, with ultra high-speed fault interruption and a higher degree of safety. “AI delivery circuits can manage cyclic optimisation, which means smart buildings can run based on human occupancy. DC is the missing piece in all this.”