The United Nations says emissions must reduce by 45% by 2030 and reach net zero by 2050 to hit the Paris Agreement target of limiting global temperature increases to below 1.5°C. According to the World Green Building Council, the built environment accounts for 40% of annual global emissions, making it a critical target for tackling climate change. As a result, the Biden Administration’s Executive Order 14057 establishes an ambitious plan to make all federal facilities net zero by 2045, and several state and local governments are implementing similar legislation. For example, New York City Local Law 97 establishes strict emission limits for buildings over 25,000 square feet, requiring a 40% reduction in emissions by 2030 and an 80% reduction by 2050. Several other states and jurisdictions also have current or pending legislation requiring net-zero or near-net-zero buildings by 2050, with several requiring significant carbon emissions reduction by 2030. Real estate owners and operators are also implementing ambitious net-zero targets to comply with corporate environmental, social, and governance (ESG) initiatives and improve the overall value and profitability of their building portfolio to maintain and attract tenants in an increasingly competitive commercial real estate market. 

Onsite DC microgrids that consist of renewable energy sources like wind, solar, and hydro, along with battery energy storage systems (ESS) that store energy from these sources, are becoming an increasingly popular means to reduce carbon emissions of commercial buildings. While renewables generate DC power, electrical distribution in a building is historically AC power, which gets converted to DC power required by most equipment and devices—everything from electronics and security appliances to LED lights, electric vehicle (EV) chargers, and building system sensors, controllers, actuators, and motors. Experts estimate that over 70% of the world’s generated AC power gets converted into DC power. Each time this conversion happens, it introduces significant losses of up to 30%. 

A DC power distribution infrastructure for building lighting, plug, and equipment loads can connect to a DC microgrid and eliminate conversion losses for maximum efficiency, net-zero status, and several other benefits. Let’s take a closer look.

What is DC Power Distribution?

There are multiple options for distributing DC power to building loads:

• Class 1 Circuits – Limited to 600VDC, Class 1 circuits are ideal for larger power loads, including 380VDC used to power networking equipment in data centers, HVAC systems, electric vehicle (EV) chargers, elevators, and other large loads.
• Class 3 Circuits – Limited to 150VDC and considered safe from a fire initiation standpoint, Class 3 circuits are primarily used in specialty systems, including nurse call, public address, and some security and life-safety systems.
• Class 2 Circuits – Class 2 circuits are considered safe from a fire initiation AND electric shock perspective as they are limited to less than 60VDC and 100W. Familiar Class 2 circuits in commercial buildings include 24VDC or 12VDC power distribution over multi-circuit (MC) cables for LED lighting, alarm panels, legacy CATV surveillance, relays, and more. Class 2 Circuits also include the following:
  • Power over Ethernet (PoE)—This type of Class 2 power is transmitted from power sourcing equipment (PSE), such as a network switch, over twisted-pair Ethernet cabling (e.g., Category 6A, 6, 5e). PoE is delivered simultaneously with data and control information to networked IP-based powered devices (PDs). PoE is increasingly used for powering and controlling LED lighting via direct connections to fixtures or intelligent nodes that manage power and control for multiple fixtures. The various levels of PoE power are defined by IEEE 802.3 Ethernet standards, with Type 1 delivering up to 15W, Type 2 up to 30W, Type 3 up to 60W, and Type 4 up to 90W. PoE lighting systems typically require the higher power levels offered by Type 3 or Type 4 PoE.
  • Single-pair Power over Ethernet (SPoE)—This type of Class 2 power is a PoE-based technology used with emerging Single-pair Ethernet (SPE) for connecting and powering low-speed OT devices, such as controllers, sensors, actuators, and meters used in building automation systems. Like PoE, SPoE is transmitted in parallel with data and can deliver up to 52W of DC power.
  • Universal Serial Bus (USB) – Traditionally used for computer peripherals, the latest USB technology can deliver data and up to 240W of DC power to shorter distances of about 1 m (3.3 ft) via much smaller connectors. USB can be delivered via computers or other power and data rendering devices (e.g., network switches) or via receptacles with built-in USB ports per Article 406 of the NEC.
• Class 4 Circuits – Class 4 power was recently adopted in Article 726 of the 2023 NEC with a voltage limit of 450VDC. Class 4 power is considered fault-managed power (FMP), a technology pioneered as Digital Electricity (DE) by VoltServer. FMP systems safely transmit bulk DC power to building loads using centrally managed transmitters and remote receivers to intelligently detect faults and immediately stop transmission, providing the same level of protection from electric shock and fire initiation as Class 2 circuits. The power and distance capabilities of an FMP system vary based on specific vendors’ technology and the number and size of conductors. For example, VoltServer’s DE system operates at 336VDC, delivering 300W and 600W to about 365 m (≈1200 ft) over one and two 18 AWG conductor pairs, respectively. It can reach levels up to 2000W using multiple pairs of larger conductors.

As shown in the graphic below, a DC power distribution infrastructure consists of incoming DC power from onsite microgrids stored in battery ESS for use when renewable sources are not generating power. DC power is then distributed throughout a building to various loads over power infrastructure comprised of multiple DC power delivery options.

For bulk power and larger loads, Class 4 FMP is a safer and far more cost-effective option than Class 1 circuits. Unlike Class 1, Class 4 FMP offers protection from electric shock and fire initiation and uses small, lightweight cables that can be deployed via typical low-voltage installation practices, eliminating the need for AC circuit panels and installation via master electricians. Class 4 FMP cables can also reside in pathways and spaces with Class 2 circuits, with no conduit required in most environments for reduced material and installation costs. With intelligent transmitters and receivers, Class 4 FMP enables improved monitoring and control via centralized management for additional energy savings. Class 4 FMP can combine with fiber optics into a single hybrid cable to converge power and data for connected electronics and smart building systems and devices. Equipment and devices that can accept Class 4 FMP are already hitting the market, including network switches, LED lighting drivers, HVAC controllers, EV chargers, and more.

Class 2 circuits such as PoE and SPoE deliver DC power to various connected devices, including computers, wireless access points, surveillance cameras, access control panels, digital displays, and building automation devices. Class 2 PoE circuits are also much smaller than Class 2 MC cables, comprising at least 80% less copper material. PoE and SPoE are also faster and easier to install than other Class 2 systems and offer better support for data transmission and centralized management. Class 2 USB ports on computer equipment, network switches, or separate receptacles deliver DC power to devices such as smartphones, tablets, laptops, video displays, speakers, microphones, and other personal devices.

Worthy Incentives and Benefits

DC power distribution in a building eliminates conversion losses and parasitic loads prevalent in most AC-to-DC transformers of building equipment power supplies, providing an estimated 10 to 20% energy savings. Combining DC power distribution with a DC microgrid makes it easier to achieve net-zero status. A DC microgrid with DC power distribution also contributes to green building certifications like LEED and qualifies for sizable tax credits under the 2022 Inflation Reduction Act—to the point where total investment can compete with traditional AC grid power distribution. Additional benefits of DC power distribution include:

• Converged power and data to support smart building systems and devices that collect and act upon information about the environment for improved efficiency, optimized operations, and enhanced occupant well-being
  
• Centralized management, control, and backup power for reduced operating expense, improved reliability, and lower energy consumption
• Ability to intelligently share power across various building loads for lowering the amount of incoming power required
• Reduced space, material, and labor for significant cost savings and lower carbon footprints
• Improved building resiliency and emissions by reducing reliance on the grid and fossil fuels during non-peak hours and enabling building operation during power outages

Want to learn more? Sinclair Digital Services, Inc. is a full-service consulting, design/build, and project management firm specializing in pioneering sustainable buildings with a primary focus on DC Power and Microgrids. Get in touch with us today at info@sinclair-digital.com to discuss how we can help get your building to net zero with a seamless, cost-effective DC power infrastructure deployment.