Single-stage solid-gas reaction heat transformer system with the reactive salts of CaCl2 and MnCl2 was investigated. The system performances with gas valve control (closed protocol) were measured and compared with those without gas valve control (open protocol). The reasons of these differences were discussed. It was concluded that specific heating power (SHP), coefficient of performance (COP) and exergic COP (COPex) of the experimental set-up were improved with gas valve control. From the theoretical analysis, it was concluded that the improvement of system performances was mainly due to the difference of gas pressure in system operation, while not the multi-step reactions between CaCl2 and NH3. Further improvements of the performances of experimental set-up were also proposed. It was concluded that conducting heat recovery process would increase system COP and COPex, and converting to novel two-stage system with reactive salts of CaCl2, MnCl2 and FeCl2 would increase temperature lift Delta T. (C) 2010 Elsevier Ltd. All rights reserved.