Pareto-optimal performance of one-bed adsorption chillers by easy-to-implement heat-flow-based control

Abstract

The control strategy strongly influences the performance of adsorption chillers: both efficiency and cooling power depend on phase times for adsorption and desorption. For a given cooling power, operating points with maximum efficiency are Pareto-optimal and desired in practice. However, finding the corresponding phase times for adsorption and desorption is difficult since these times vary with system characteristics and inlet conditions. In this paper, we mathematically derive a control strategy which is based only on heat flow measurements in the evaporator and the condenser of the adsorption chiller. The derived control strategy finds the Pareto-optimal adsorption and desorption phase times for a given cooling load. The control strategy is easy to implement since it only requires easily available temperature and volume flow measurements in the secondary fluid circuits. The derived control strategy is tested in (1) a simulation study and (2) an experimental study. In the simulation study, we show that the control strategy leads to (near) Pareto-optimal operation in cyclic steady-state and quickly responses to step-changes in the inlet conditions. In the experimental study, we demonstrate the ease of implementation and we show optimal operation for continuously varying inlet conditions. © 2019 Elsevier Ltd.