Improving Discharge Characteristics of Indirect Integral Collector Storage Systems with Multielement Storage
The desired performance of unpressurized integral collector storage systems hinges on the appropriate selection of storage volume and the immersed heat exchanger. This paper presents analytical results expressing the relation between storage volume, number of heat exchanger transfer units, and temperature-limited performance. For a system composed of a single storage element, the limiting behavior of a perfectly stratified storage element is shown to be superior to a fully mixed storage element, consistent with a more general analysis of thermal storage. Since, however, only the fully mixed limit is readily obtainable in a physical system, the present paper also examines a division of the storage volume into separate compartments. This multielement storage system shows significantly improved discharge characteristics as a result of improved elemental area utilization and temperature variation between elements, comparable in many cases to a single perfectly stratified storage element. In addition, the multielement system shows increased robustness with respect to variations in heat exchanger effectiveness and initial storage temperature.
A. M. Boies and K. Homan, "Improving Discharge Characteristics of Indirect Integral Collector Storage Systems with Multielement Storage," Journal of Solar Energy Engineering, American Society of Mechanical Engineers (ASME), May 2008.
The definitive version is available at http://dx.doi.org/10.1115/1.2840569
Mechanical and Aerospace Engineering
National Renewable Energy Laboratory (U.S.)
Keywords and Phrases
Thermal Energy Storage; Heat exchangers
Article - Journal
© 2008 American Society of Mechanical Engineers (ASME), All rights reserved.