Use of parabolic trough solar collectors for solar refrigeration and air-conditioning applications

Abstract

The increasing energy demand for air-conditioning in most industrialized countries, as well as refrigeration requirements in the food processing field and the conservation of pharmaceutical products, is leading to a growing interest in solar cooling systems. So far, the more commonly systems used are single-effect water/lithium bromide absorption chillers powered by flat-plate or evacuated tube collectors operating with COP of about 0.5–0.8 and driving temperatures of 75–95 °C. In general terms, performance of thermally driven cooling systems increases to about 1.1–1.4 using double-effect cycles fed by higher temperature sources (140–180°C). If solar energy is to be used, concentrating technologies must be considered. Although some experiences on the integration of parabolic trough collectors (PTC) and Fresnel lenses in cooling installations can be found in the literature, the quantity is far to be comparable to that of low temperature collectors. Some manufacturers have undertaken the development of modular, small, lightweight and low cost parabolic collectors, compatible for installation on the roofs of the buildings aiming to overcome some of the current technology drawbacks as costs and modularity. After a comprehensive literature review, this work summarises the existing experiences and realizations on applications of PTC in solar cooling systems as well as present a survey of the new collectors with potential application in feeding double effect absorption chillers. In addition to this, it is evaluated its use as an occasional alternative to other solar thermal collectors in air conditioning applications by dynamical simulation. Results for the case studies developed in this work show that PTC present similar levelized costs of energy for cooling than flat plate collector (FPC) and lower than evacuated tube collectors (ETC) and compound parabolic collectors (CPC).