"Preface This book covers the state of the art of adsorption research and technologies for relevant applications based on the use of the efficient heat transfer devices--heat pipes and two-phase thermosyphons--with the objectives of energy efficiency and sustainability. The severities of energy crisis and environmental problems have been calling for rapid developments in Freon-free air conditioning and heat pump technologies, the heat exchangers, which are considered as the components of prime importance. The concerns of energy consumption and environmental pollution urge researchers to work on the development of clean energy and the utilization of waste energy. From this viewpoint, interest in fuel cells and thermally activated (heat pipe heat exchangers) adsorption systems using natural refrigerants and/or alternative to hydrofluorocarbon-based refrigerants has increased significantly. The quest to accomplish a safe and comfortable environment has always been one of the main preoccupations of the sustainability of human life. Accordingly, during the past few decades, research aimed at the development of thermally powered adsorption cooling technologies has intensified. They offer two main benefits: (1) reduction in energy consumption and (2) adoption of environmentally benign adsorbent/refrigerant pairs, without compromising the desired level of comfort conditions. The efficiency of new power sources (co-generation, tri-generation systems, fuel cells, photovoltaic systems) can be increased with the help of heat pipe heat exchangers, solid sorption heat pumps, refrigerators, accumulators of heat and cold, heat transformers, and fuel gas (natural gas and hydrogen) storage systems. Low-temperature power systems are generally significantly less expensive to build"--