We have studied solar thermal power generation devices. One is a Cone-shaped power generation device and the other is a Dome-shaped power generation device. Those are different at the point of sunlight inlet shape. In our experimental study, we have concluded the Dome-shaped power generation device is superior to the Cone one from the viewpoint of volumetric efficiency using the estimation method with heat collection coefficient, heat retention coefficient, and heat dissipation coefficient. Then we performed a matrix power generation device arrayed with many Dome-shaped power generation devices. The matrix power generation device can generate power of more than 30 mW. The power is small compared to the solar power generation at present. However, we estimate that the potential of solar thermal power generation devices can generate power of up to 15% compared to solar power generation. In this paper, we discuss the potential of solar thermal power generation devices and show their ability for power enhancement by material development.