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In this paper, we propose GreenCoin – an energy-efficient cryptocurrency system with mining protocols designed to favor locations with relatively higher availability of renewable energy. Traditionally, crypto coin mining involves solving complex mathematical problems by high-end computing devices consuming an enormous amount of electricity, thus adversely affecting net carbon emissions. To reduce cost and emissions, GreenCoin uses a modified proof of stake (PoS) consensus algorithm, which itself is more energy efficient compared to other state-of-the-art methods. Our modified PoS algorithm, called Green PoS (GPoS), allows GreenCoin to favor nodes (with reward and privilege) located in regions with higher availability of renewable energy. We present a detailed system architecture of GreenCoin and explain the operating method of GPoS. We also provide results from empirical studies demonstrating the renewable energy-aware approach of GreenCoin. 

Serverless computing has increased in popularity as a programming model for “Internet of Things” (IoT) applications that amalgamate IoT devices, edge-deployed computers and systems, and the cloud to interoperate. In this paper, we present Laminar – a dataflow pro- gram representation for distributed IoT application programming – and describe its implementation based on a network-transparent, event-driven, serverless computing infrastructure that uses append- only log storage to store all program state. We describe the initial implementation of Laminar, discuss some useful properties we obtained by leveraging log-based data structures and triggered com- putations of the underlying serverless runtime, and illustrate its performance and reliability characteristics using a set of benchmark applications.