The evaluation of thermal stratification by exergy

Abstract

What makes a good heat store? Is it a large store, with a large volume? And is the largest the best? We experienced this question when the first solar houses were built: many stores were oversized and never reached temperatures high enough for heating. It was learned that consumer needs, solar collector areas a nd storage capacity have to be well balanced to give a satisfying solar heating system. Not to speak of costs which usually promote the final decision. It is quite simple to calculate external losses; it is complicated and requires a number of assumptions to calculate internal degradation. But nevertheless, there is the need to quantify advantages and disadvantages of the various stores in order to compare them and to improve them.