Beginning in early 1974, the staff of the National Bureau of Standards (NBS) began the development of'thermal test procedures for the two primary non-conventional components of solar heating and cooling systems, solar collectors and thermal storage devices. Recommended procedures for testing both components were published in late 1974 and early 1975 [1, 2] in a format consistent with the Standards of the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE). The procedures were later published, with supplementary information explaining the rationale behind each procedure [3, 4, 5].

In July, 1975, ASHRAE formed Standards Project Committee 94-P to develop a standard for the testing of thermal storage devices. In June, 1976, a draft of a standard was published and submitted to the Society for review. It was based substantially on the previously published NBS-recommended procedure [2]. The ASHRAE draft was modified according to the review comments received and then forwarded to the ASHRAE Standards Committee for approval. In February, 1977, the ASHRAE Board of Directors approved and authorized publication of ASHRAE Standard 94-77, Methods of Testing Thermal Storage Devices Based on Thermal Performance [6].

The purpose of this paper is to describe the results of an experimental study conducted at NBS during 1977 in which a 1.9 m (500 gal.) water tank was tested in accordance with Standard 94-77. The study demonstrates the applicability of the Standard to this type of sensible-heat storage device. Similar experiments are presently being conducted at NBS on residential-size pebble-bed and phase-change storage devices and the results will be published at a later time.

It should be noted that a similar and parallel process has occurred with the NBS-recommended test procedure for solar collectors [1]. ASHRAE Standard 93-77, Methods of Testing to Determine the Thermal Performance of Solar Collectors, was adopted and published in February, 1977 [7]. NBS has conducted a series of experiments demonstrating the.use of this Standard for typical commercially-available water-heating and air-heating collectors [8].