TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The nano-molten salt composite phase-changing energy-storing material comprises 1-5 wt.% expanded graphite and 95-99 wt.% primary phase change material, which are compounded together, where the compounding process is adding expanded graphite to the primary phase change material aqueous solution, dispersing by ultrasonic drying and dehydrating, where the primary phase change material is a binary salt mixture of sodium nitrate and potassium nitrate, in a mass ratio of (4-6):(6-4), the transition temperature of the nano-molten salt composite phase-changing energy-storing material is 210-230 degrees C and the latent heat is 120-150 J/g.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The Fresnel light-collecting device is made by hot pressing polymethyl methacrylate, provided with circular or square shaped structure, and with the multiplying power of 100-1000 times. The phase change energy storage heat exchanger is a cylinder, whose outer wrapping layer is an insulating layer, upper and lower ends is a furnace heat insulation cover and a heat absorbing chamber insulation cover and the middle part is phase change energy storage heat exchanger inner container. The upper and lower ends of the phase change energy storage heat exchanger inner container are provided with a heat releasing furnace head and a heat absorption chamber. The external part of the heat releasing furnace head is covered with the furnace heat insulation cover and the external part of the heat absorption chamber is covered with the heat absorbing chamber insulation cover. The rear part of the heat absorbing chamber is provided with 4-6 metal bar-shaped ribs used for heat conduction. The heat absorbing chamber is aligned with converging focal point of the Fresnel light-collecting device. The phase change energy storage heat exchanger inner container is provided with nano-molten salt composite phase-changing energy-storing material. The heat absorbing chamber insulation cover is opened and the heat insulation cover is closed while the heat absorption in the phase change energy storage heat exchanger. The heat absorbing chamber insulation cover is closed and the heat insulation cover is opened while heat-releasing time. The heat absorbing chamber insulation cover and heat insulation cover are closed during heat storage time.