The development of a 1 KW electrical output free piston Stirling engine alternator unit

Abstract

Sunpower, Inc. has been engaged in the development of free-piston Stirling engine alternator units since 1971. After considerable experience gained with high pressure (50 to 80 bar) engines, it appears that the high pressure configuration may not necessarily be the most appropriate approach to a successful commercial design. The repeated difficulty associated with the design of an efficient, cost effective heat input system plus the tight clearances forced by a critical sensitivity to leakage losses poses problems which have not been satisfactorily resolved in the past. In an effort to address these and other specific technical problems relating to the commercialization of Stirling engines, Sunpower has decided on a radical departure from the high pressure design so prevelant in the industry. Recent engines built at Sunpower all operate at substantially lower charge pressure than those built in the past. Described here is one program to develop a low pressure 1 kW free-piston alternator unit. It is shown that the low pressure configuration addresses both the heat input system and clearance problems with an acceptable compromise in the other aspects of the design. Two generations of the design have been built, one has been operated on a coal burner with verymore » encouraging results and the other is presently on test in our laboratory.« less