The papers included in this special issue are the result of an open call for papers and a set of selected papers from the 4th International Conference on Smart Cities and Green ICT Systems (SMARTGREENS 2015).

In line with the topics of SMARTGREENS, this special issue will focus on solutions for all aspects of green computing such as energy efficiency, carbon footprint reduction and cooling management. The tradeoffs between energy efficiency and performance have become key challenges that must be addressed in all areas of computing, from embedded and distributed systems to traditional performance-oriented infrastructures. Particularly relevant is the so-called Smart Grid technology, seeking to optimize distributed electricity generation, especially from renewable sources, and to promote the use of smart devices (including smart home and new vehicular energy approaches) that require further research on distributed communications, energy storage and integrations of various sources of energy.

This special issue received 14 submissions and herewith presents 5 research papers with novel concepts and applications in the aforementioned areas. The high number and high quality of the papers received imposed difficult choices in the selection process.

We believe that all papers presented in this special issue will serve as a reference for students, researchers, and practitioners who research in the areas of Smart Cities and Green ICT Systems. We hope that the readers will find new inspiration for their research and may join the SMARTGREENS community in the future.

We would like to thank all the authors for their contributions and also to the reviewers who have helped ensuring the quality of this publication. Also we would like to thank INSTICC for organizing the conference and for their intensive support in preparing this special issue. Finally, we would also like to express our gratitude to the Springer Computing editorial staff of Springer, in particular to Prof. Schahram Dustdar and Christine Kamper to all their patience and availability during this process.

We hope you enjoy this special issue.

October 2016