A method for online steady state energy minimization, with application to refrigeration systems

Energy efficiency of refrigeration systems has gradually been improved with the help of control schemes utilizing the more flexible components; however, the efficiency is far from optimal. The flexibility initiates a higher degree of freedom in choosing the operating set points while obtaining the required cooling capacity. This paper proposes an approach which utilizes this newly gained degree of freedom to drive the system towards the energy optimal set-point while keeping up the cooling capacity. The focus of this paper is on a refrigeration system, but the generality of the proposed method applies to a broader range or process systems where the lower level set-points (in the control hierarchy) can be chosen within a degree of freedom allowing optimization of the steady state performance index.