The purpose of this project is to determine the feasibility, cost effectiveness, market barriers, customer needs, and savings potential for direct current (DC), or hybrid DC-AC systems, to power zero net energy (ZNE) residences and commercial buildings, subdivisions, and communities. Particular focus will be on residential and light commercial building applications.

Various aspects of DC electrical systems have been studied. These analyses suggest that multiple benefits could be achieved from using DC:

• Easier and more-efficient integration with renewable sources and electric vehicles
• Improved efficiency and control of motors, appliances, electronics, and other technologies
  
• Improved reliability at a lower capital cost
• Elimination of AC power quality problems
• Easier integration of electricity storage (batteries, capacitors)
• A unique opportunity for worldwide interoperability, voltage, and connector standards

 For ZNE buildings, the use of DC power has the potential to reduce the amount of on-site generation necessary, facilitate the use of energy storage, and more easily tie to electric vehicles, while saving energy lost in power conversions.

Project Description

This collaborative project will significantly expand knowledge for the various applications of DC power, focusing on new residential construction and residential subdivisions, as well as retrofits of residential and commercial buildings, including design of AC-DC hybrid systems.

The project will be organized in two phases:

• The first phase will interview stakeholders and analyze available state, national, and international information on DC power in buildings and microgrid applications. The project team will interview customers and conduct a workshop with stakeholders, including end-users, designers, builders, industry, and utilities to understand industry and customer choices, barriers, and codes, and policy needs for DC systems. A summary report from the first phase of the project will provide a comprehensive collection of public data and analysis of existing DC buildings, subdivisions, communities, and other applications. It will also identify appropriate end-use applications for DC power, barriers to adoption of DC power, codes and standards issues, and an assessment of customer, builder, and utility acceptance of DC systems.

• The second phase will use the information from the first phase to optimize the design and evaluate the costs, benefits, or drawbacks of DC and AC-DC hybrid systems for residential and commercial zero net energy buildings, both for new construction and retrofit. The project team will develop design templates for DC or AC-DC hybrid systems, and analyze the relative efficiencies using manufacturer’s published efficiency data and/or limited lab evaluations. Savings and costs for key end use applications for DC power (e.g., motors, adjustable-speed drives, lighting, electronics, and plug loads) will be estimated. The team will then develop case studies describing other demonstration results. The project findings will summarize the technical and economic feasibility, barriers, market acceptance, reliability, and operational advantages for DC and AC-DC hybrid systems for buildings, subdivisions, and communities.