Abstract
Driven by the proliferation of DC energy sources and DC end-use devices (e.g., photovoltaics, battery storage, solid-state lighting, and consumer electronics), DC power distribution in buildings has recently emerged as a path to improved efficiency, resilience, and cost savings in the transitioning building sector. Despite these important benefits, there are several technological and market barriers impeding the development of DC distribution, which have kept this technology at the demonstration phase. This paper identifies specific end-use cases for which DC distribution in buildings is viable today. We evaluate their technology and market readiness, as well as their efficiency, cost, and resiliency benefits while addressing implementation barriers. The paper starts with a technology review, followed by a comprehensive market assessment, in which we analyze DC distribution field deployments and their end-use characteristics. We also conduct a survey of DC power and building professionals through on-site visits and phone interviews and summarize lessons learned and recommendations. In addition, the paper includes a novel efficiency analysis, in which we quantify energy savings from DC distribution for different end-use categories. Based on our findings, we present specific adoption pathways for DC in buildings that can be implemented today, and for each pathway we identify challenges and offer recommendations for the research and building community.
Highlights
National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA; This paper is a technically extended version of a conference paper entitled “Direct-direct current (DC) Power in Buildings: Identifying the Best Applications Today for Tomorrow’s Building Sector”, by a subset of the authors above, presented at the 2020 ACEEE Summer Study on Energy Efficiency in Buildings
DC power distribution in buildings has recently emerged as a path to improved efficiency, resilience, and cost savings in a transitioning building sector, thanks to three factors: (1) the increased market penetration and cost reductions of DC sources, such as photovoltaics (PV) [1] and battery storage [2]; (2) the availability of DC end uses, such as electronics, electric vehicles (EVs), and solid-state lighting [3]; and (3) recent advancements in power electronics technologies
DC distribution in buildings with onsite DC sources powering DC end uses can lead to energy savings of up to 18 percent compared to alternating current (AC) distribution, according to power simulation studies [4,5,6] and field measurements [7,8]
Summary
Since the war of the currents of the late 1800s, alternating current (AC) has dominated power distribution in the building sector. Additional potential benefits of DC power distribution include fewer maintenance requirements, longer-lived system components, and simpler load control [13]. Despite these important benefits, the market for DC distribution in grid-connected buildings in the United States and globally is still in the demonstration phase, with few actual buildings utilizing DC directly from an onsite DC source to power building end uses (direct-DC). The benefits of DC systems have been documented and quantified in some cases (e.g., efficiency) Such benefits have mostly been evaluated individually or at the building level, and less often for specific applications, without considering real-world opportunities and challenges to implementation
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