Improving Discharge Characteristics of Indirect Integral Collector Storage Systems with Multi-Element Storage


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 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 multi-element 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 multi-element system shows increased robustness with respect to variations in heat exchanger effectiveness and initial storage temperature.

Meeting Name

2004 International Solar Energy Conference (2004: July 11-14, Portland, OR)


Mechanical and Aerospace Engineering

Keywords and Phrases

Heat Exchanger; Storage Volume; Temperature Limited Performance; Thermal Storage; Heat storage devices

Document Type

Article - Conference proceedings

Document Version


File Type





© 2004 American Society of Mechanical Engineers (ASME), All rights reserved.

Publication Date

01 Jan 2004

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