Optimal operation of solar heat storage with off-peak energy price incentive

The problem of minimum cost control of a solar-assisted heat pump/heat storage system is considered. The system is configured to have separate storage for collected solar heat and high-temperature heat, so that night-time (‘off-peak’) operation of the heat pump is possible. The problem of finding the optimal operating strategy when electrical energy is priced at a discount during off-peak hours is considered. The solution of the periodic optimization problem is obtained through the use of state increment dynamic programming, simplified through the use of state feedback linearization/decoupling and augmented with a label-tracing procedure to identify the periodic but unknown initial/terminal state. The algorithm is applied for a typical case study. The results lead to several observations concerning economical operating strategies.