This paper presents a prototype implementation of a USB charging device with Ethereum blockchain support for booking and payments. It outlines the design of the system and selection of hardware and software components for the end-to-end solution. Blockchain technologies are relatively new and promising development for decentralized trusted transactions, including micropayments. There are many possible application domains of blockchain technology envisaged; one of them is smart grid. Several initiatives are prototyping solutions in this domain; however, there is still a vast unexplored area related to technological and business aspects of blockchain in energetics. Our prototype provides an end-to-end solution that is comprised of a blockchain enabled end-device, Web applications with blockchain clients for users and administrators, and corresponding smart contracts for the specific transaction logics. The prototype was implemented as a DIN rail compatible device based on RPi and a user application as Javascript code embedded in HTML page that can be opened in Chrome browser with Metamask plugin installed. The system was successfully implemented and tested and it confirmed the viability of the concept.
With modest modifications this approach could be extended to electric vehicle chargers, smart grid supply and demand management or other utility support systems.

PUSTIŠEK, Matevž, BREMOND, Nicolas, KOS, Andrej. Electric switch with Ethereum blockchain support. The IPSI BgD transactions on internet research, ISSN 1820-4503. [Print ed.], Jan. 2018, vol. 14, no. 1.