A new solar heat engine is provided in the form of a pressure oscillation generation device having a chamber with two spaced apart walls, means on one wall receiving sunlight through said one wall, means on the other of said walls continuously cooling said other wall, a light absorbing surface on a thermal shield movable between said walls, means for automatically alternating said sunlight absorbing surfaced thermal shield back and forth between said walls whereby a heat expansible fluid contained in said chamber is alternately heated and cooled thereby causing said fluid to undergo alternate expansions and contractions. The alternate expansions and contractions of the fluid are used to produce useful work by pump action, torque action, compression and the like.