A novel solar absorption refrigeration system using the multi-stage heat storage method

• A multi-stage heat storage method has been added to our earlier research system (heat pump solar absorption refrigeration system).
• The issue of the whole day cooling requirement for solar absorption refrigeration system has been solved.
• The coefficient of performance for the system has been improved.
• The low cost signal flat-plate collector can be used in the novel system.

This paper introduces a multi-stage heat storage system using phase change materials with different melting points into the heat pump solar absorption refrigeration system which proposed by our earlier research work. Using meteorological data for the city of Nanjing, the performance of the novel system with a cooling capacity of 10 kW is quantitatively analyzed: (1) More than 91 m2 of solar collection area is required for the single flat-plate collector to satisfy the daily need of cooling. (2) Four different types of collectors, including single flat-plate collector, all-glass vacuum tube collector, heat pipe evacuated tube collector, and compound parabolic vacuum tube collector are compared. The results of solar collection areas show that the difference among them is not significant. Considering the building adaptability and production cost in the application designs, single flat-plate collector is preferred. (3) The coefficient of performance for the system with multi-stage heat storage system is approximately 1.3–2.4 times to that with the corresponding single-stage heat storage system at the given conditions. (4) The coefficient of performance of the novel system increases with the melting points of the phase change materials in the heat storage system when the solar radiation intensity is high (0.8 kW/m2), and behaves the opposite when the solar radiation intensity is low (0.3k W/m2).