Sustainable Cooling Strategies Using New Chemical System Solutions

Abstract

Energy-efficient cooling concepts play an important role for numerous applications in the area of comfort and industrial cooling. In this regard, it represents a huge challenge to ensure that the cooling demand of industrialized countries is covered in a sustainable manner with a drastically reduced carbon footprint. In recent years, several innovations in the field of absorption have been introduced. While some of them are based on process improvements, other innovations are based on newly developed chemical system solutions. One example is the use of new working pairs for absorption chillers. In the past, working pair related drawbacks such as crystallization, corrosion, and instability led to a number of innovation barriers. One very promising way to overcome these drawbacks and thereby to allow for new or improved absorption chiller processes is the replacement of the state-of-the-art absorbent LiBr by a suitable ionic liquid (IL). This review aims at discussing new, energy-efficient cooling concepts with a special focus on using ionic liquid based working pairs in absorption chillers/absorption heat pumps. The most relevant research and development activities are analyzed, a patent overview is provided, and both new technological opportunities and remaining scientific challenges are identified. Although a large number of ionic liquid papers have been published in this field during the last 10 years, many contributions do not adequately address the interdisciplinary set of application requirements and do not fully recognize that most imidazole-based ionic liquids are not suitable for being used in multieffect absorption cycles since their (in)stability at high temperatures in the presence of water and the resulting cooling capacity do not meet the industrial requirements.