Back to the future: A need for multi-drop Ethernet for cost-effective power distribution

Local renewable DC electricity sources, such as solar, have become cost competitive. In this position paper, we argue that an Ethernet LAN with Power-over-Ethernet (PoE) is a nanogrid where the physical layer infrastructure is used for DC electricity distribution and the link-layer capabilities can be used to match electricity supply and demand. To be cost effective with respect to wiring, many of these nanogrids must be multi-drop where each drop may be a power socket. Open challenges to employing PoE as a multi-drop managed nanogrid include 1) extending LLDP for multi-drop, 2) adapting LLDP to support the use of price signals for modulating power demand, 3) achieving efficient PoE power flow in a multi-drop circuit, and 4) implementing low-cost and fair scheduling for packet transmission. We explore how multi-drop Ethernet can be implemented with fair access to all devices by employing at each drop a mini-switch with packet scheduling.