IntroductionThe conference is organized by the Faculty of Power Engineering and Power Machines at the Technical University of Sofia, Bulgaria. This is the 28th annual edition of the event, part of the “Days of Science” activities at the Technical University of Sofia. For the past 28 years, this conference has become a traditional annual scientific forum for the meeting of Bulgarian and foreign experts and industry representatives in the field of energy and renewable energy technologies, thermodynamics, heat engineering, building efficiency improvements and HVAC systems, environmental engineering and protection, hydraulics and pneumatics, textile and sewing production.All received publications are peer reviewed and traditionally, the highest quality scientific papers are further submitted for publishing in referenced partnering journals. Based on recent years of experience, the conference offers on-site and online possibility for attendance. The program includes keynote lectures from selected popular topics in the presented areas, as well as oral presentations of the papers by the participants. It became a tradition, for some of the main sponsors, to organize special demonstration stalls in the conference area, where they can expose their latest innovative products and have a closer meeting with the audience.This year, three exhibitions were organized and performed as side events, during the conference days. The first one is called “EcoSynthetic”, and it is an exposition of nine woodcrafter sculpture artists, developing the “energy concept” in their work. The second exposition presented students’ design ideas for devices or technologies for green and sustainable energy utilization. And finally, a small textile exhibition with textile products, developed with sustainable and zero-waste technologies, was demonstrated during the conference days.List of Organizers, Venue, Conference topics, Committees, Editors, Sessions, Participants, Sponsors, Contacts, Conference pictures, Conference Program, Conference Agenda are available in this pdf.