Solar Desiccant Air-Conditioning in an Industrial Application: Optimisation Approaches for Solar-Thermal Integration and Air-Handling Unit
Abstract
Solar-driven air-conditioning with DEC-systems (Desiccant and Evaporative Cooling) is a renewable solution and promising alternative to nowadays´ electricity based compression type refrigerating. While this conventional technology, with its consumption of fossil primary energy affects the depletion of resources and contributes to the global warming through CO2-emissions, solar air-conditioning is an approach, which uses solar-thermal heat, in contrary to electricity, to drive air-conditioning systems. Against this background, the CENTRE OF EXCELLENCE FOR RENEWABLE ENERGY RESEARCH at Ingolstadt University of Applied Sciences (Germany) investigates a solar-driven desiccant and evaporative cooling system in a multipurpose building, operated with two large arrays of solar-thermal flat-plate collectors. This paper initially describes the system layout and the measurement equipment integrated in the solar DEC-system. Subsequently, the measurement results of 2009 cooling period are summarised, which showed a considerably low refrigeration capacity of the system. Operational optimisations that were realised prior to the 2010 cooling period are described and consequently, the measurement results of the solar DEC-system in the 2010/11 cooling periods are analysed. For this purpose, first the air-handling components desiccant wheel and heat recovery wheel are analysed, which repeatedly showed considerable deficiencies in efficiency. Combined with the results of a process water analysis, the impact of an insufficient water treatment (causing severe calcification in the air ducts) on the efficiency of components and system is discussed. Secondly, as a main part of this paper, the analysis focuses on the operation of the two large solar collector arrays and its integration in the DEC-process. Intensive experiences on the operation of such a large complex system are discussed and the importance of self control mechanisms as well as the enforcement of quality assurance processes are argued, in order guarantee an energy efficient operation of the overall system. An outlook on the further proceeding in the current research project particularly with regard to the system simulation concludes the paper.