Analysis of the exergy balance of green leaves

Abstract

In this paper we analyze the exergy balance of green leaves. The exergy source comes from the direct and diffuse solar radiation absorbed in the leaves, while exergy destruction occurs as the consequence of evapo-transpiration, of internal flows and of leaf metabolism. Exergy storage occurs namely in the form of glucose which is a result of photosynthesis and oxygen release into the environment. Based on the exergy balance equation we can evaluate the leaf metabolic rate and the survival threshold conditions. In the absence of the exergy source (solar radiation) we can also understand how the trees use the exergy stored for their metabolic needs. This process is similar to the discharge of a capacitor though a resistance, which is a characteristic found in every living structure.