  Power grids are undergoing major changes due to rapid growth in renewable
energy resources and improvements in battery technology. While these changes
enhance sustainability and efficiency, they also create significant management
challenges as the complexity of power systems increases. To tackle these
challenges, decentralized Internet-of-Things (IoT) solutions are emerging,
which arrange local communities into transactive microgrids. Within a
transactive microgrid, "prosumers" (i.e., consumers with energy generation and
storage capabilities) can trade energy with each other, thereby smoothing the
load on the main grid using local supply. It is hard, however, to provide
security, safety, and privacy in a decentralized and transactive energy system.
On the one hand, prosumers' personal information must be protected from their
trade partners and the system operator. On the other hand, the system must be
protected from careless or malicious trading, which could destabilize the
entire grid. This paper describes Privacy-preserving Energy Transactions
(PETra), which is a secure and safe solution for transactive microgrids that
enables consumers to trade energy without sacrificing their privacy. PETra
builds on distributed ledgers, such as blockchains, and provides anonymity for
communication, bidding, and trading.
