Storing Solar Energy in Thermally Stratified Tanks

摘要

Described are: how solar-system tanks fail to stratify, a new solar-system control strategy that allows stratification, a one-dimensional analytical model of thermally stratified tanks, experimental measurement of thermal stratification in tanks, and a correlation of experimental measurements with empirical constants in the analytical model. Failure to stratify is explained in terms of the critical Richardson number. The key to the new control strategy is to avoid a Richardson number that decreases during solar collection. The analytical model is an approximate solution containing two empirical constants. The empirical constants were adjusted to obtain the best least-squares fit with experimental data and correlated with the Fourier and Richardson numbers. The new control strategy allows tanks to stratify and reduces the average collector operating temperature by as much as 20 exp 0 C. Several features of tank design that improve thermal stratification are also described. (ERA citation 08:023356)