Overcoming barriers to direct current power: Lessons learned from four commercial building case studies

While distribution systems deliver power to buildings using alternating current (AC), the loads in commercial buildings have increasingly shifted to those using direct current (DC) power. In addition, on-site generation, such as rooftop solar (which provides a DC source of electricity), is becoming more common in commercial buildings. As a consequence, numerous DC-to-AC and AC-to-DC conversions occur in commercial buildings, each of which results in wasted energy. This makes converting building electrical systems from AC to DC power an attractive energy efficiency measure. In the present study, barriers and advantages of DC power in commercial buildings were examined by interviewing personnel who worked on four commercial construction projects in Colorado. The cases, two new construction and two retrofits, varied in their level of successful implementation. The participants included general contractors, facilities managers, engineers, and financial officers. Interviews were coded for statements about people, technology, and the construction process. The results revealed that successful implementation required an owner who championed the project, along with a team that demonstrated positive motivations (e.g., enjoying a challenge, accepting uncertainty). Technological issues faced by the projects were largely due to limited availability and incompatibility of DC parts. Finally, pre-construction processes (financing, bidding, and contracting) emerged as important differentiators between successful and unsuccessful projects. These findings provide a roadmap for increasing successful implementation of DC power in commercial construction projects.