Energy-saving opportunities of direct-DC loads in buildings

TLDR: How typical building loads can benefit from DC input is identified, including bath fans, refrigerators, wall adapters, task lights, and zone lighting, and the development of several prototypes that demonstrate efficiency savings with DC are detailed.

About: This article is published in Applied Energy.The article was published on 2019-08-15 and is currently open access. It has received 35 citations till now. The article focuses on the topics: Variable-frequency drive.

Figures

Figure 2: DC-connected loads have an internal DC stage that can be connected or hardwired to DC distribution. DC-converted loads require an input DC/DC converter, but still benefit from a DC input. DC-indifferent loads do not benefit from a DC input.

Figure 6: Input power conversion boards for the Delta bath fan. (a) The original rectifier board that converts 120 VRMS AC to 12 V DC. The board dimensions are 8 x 6 cm. (b) A Murata MYBSP0122BABF 48/12 V DC/DC converter for interfacing the DC capacitor stage with PoE. The board dimensions are 3.5 x 2 cm.

Figure 7: Efficiency curves for the prototype bath fan’s AC/DC and DC/DC boards.

Figure C.21: A model of the energy flow in a VFD motor with PFC. The DC capacitor is responsible for absorbing the AC component of Pin, allowing for a purely DC Pout. In this model, the inverter is a half-bridge and the motor is represented by its winding inductance LL and a constant back EMF.

Figure 12: Two different methods for powering the internal DC bus in electronics. (a) Native-DC electronics require a wall adapter, which often rectifies 120 V AC to 170 V DC and steps-down to the 5-20 V DC appropriate for electronics. (b) This work considers direct-DC electronics to be DC-connected.

Figure 17: Efficiency curves for the 380 V DC series-remote driver with 1-4 LED tubes attached in series. The driver’s efficiency increases with the number of attached tubes.