The emission saving related to the use of renewable energy sources: The case study of solar thermal collectors

Abstract

The employment of renewable energy sources can represent a useful way to reduce air emissions released by conventional ones. In this paper we describe the results of a Life Cycle Analysis performed upon one of the most world-wide diffused renewable technologies: the solar thermal collectors for warm sanitary water. Two domestic solar plants have been investigated: mono-familiar plant with a passive flat collector and a large solar plant with forced fluid circulation. The first step has been the evaluation of direct and indirect emissions related to the production and use of plants. The main emissions have been categorised in three of the most important indicators (Global Warming Potential, Acidification Potential and Photochemical Ozone Creation Potential) and successively we have estimated the emission saving. Considering that a solar plant works with an auxiliary heater, the pollutants that would be produced by the conventional part of the plant without the employment of collectors are the "emission saving". These avoided atmospheric releases depend on the typology of the used conventional system. The case studies of electric and gas heaters have been investigated. The final aim is to perform a global balance between the air emissions related to the production and use of the solar plants and the emissions saved during their useful-life. These results are synthesised by various indicators that contain useful information to evaluate the environmental efficiency of the studied renewable technology.