Abstract
The NAL, National Aerospace Laboratory of Japan, has been studying Stirling generators as a candidate system for the utilization of solar thermal energy. Several types of semi-free-piston Stirling generator have been fabricated and experimentally evaluated. These prototype engines, called the NALSEM (NAL Stirling Engine Model) series, are semi-free-piston Stirling machines with a moving-magnet linear alternator. The NALSEM500 was designed to achieve thermodynamic efficiency of 30% or more with an indicated power of 500W. The design performance has been achievable to date. Based on this achievement, an improved Stirling engine generator, the NALSEM700, has been designed as part of the present study. This engine has an opposed-piston configuration to minimize mechanical vibration, and is expected to provide higher performance and stability than the NALSEM500. Addressed in this paper are discussions of the NALSEM500 test results, and both the design and design verifications of the NALSEM700.
