Utility systems operation: Optimisation-based decision making

Abstract

Utility systems provide heat and power to industrial sites. The importance of operating these systems in an optimal way has increased significantly due to the unstable and in the long term rising prices of fossil fuels as well as the need for reducing the greenhouse gas emissions.This paper presents an analysis of the problem for supporting operator decision-making under conditions of variable steam demands from the production processes on an industrial site. An optimisation model has been developed, where besides for running the utility system, also the costs associated with starting up the operating units have been modelled. The illustrative case study shows that accounting for the shutdowns and start-ups of utility operating units can bring significant cost savings.

Optimal scheduling of industrial combined heat and power plants under time-sensitive electricity prices

“…Third, thermodynamic insights, such as the Willans line, are used to describe the component on an input-output basis (Ashok and Banerjee, 2003) [41]. It is important to note that the choice can be made for each component individually and researchers often combine the three approaches (Yusta et al, 2008 [42]; Agha et al, 2010 [16]; VelascoGarcia et al, 2011 [43]). In the following, we describe the aforementioned papers that use thermodynamic balance equations in more detail.…”

“…They use piece-wise linear approximations for boiler efficiencies and constant steam turbine efficiencies. Velasco-Garcia et al (2011) [43] utilize a simplified version of the model by Varbanov et al (2004) [30] based on the Willans line approach to model the turbines of an industrial CHP plant and also incorporate a few logic constraints. However, they only consider the next set point for the CHP plant, i.e.…”

Formulating an Optimization Problem for Minimization of Losses due to Utilities

“…This is done for penalizing shutdown/start-up of different utility generation units in Iyer and Grossmann (1997) and Velasco-Garcia et al (2011), which results in a mixedinteger linear program.…”

“…Work within this area includes among others Papoulias and Grossmann (1983), Hui and Natori (1996), Maia et al (1995), Velasco-Garcia et al (2011), Iyer and Grossmann (1998) and Wilkendorf et al (1998). In most of these studies, the synthesis problem has been formulated as a mixed-integer linear program (MILP).…”

A Steam Utility Network Model for the Evaluation of Heat Integration Retrofits – A Case Study of an Oil Refinery

“…The large number of interdependencies and variations makes the system complicated and make it difficult to analyse the energy consequences of Heat Integration projects without including modelling of the steam system in the analysis. Every Heat Integration retrofit that implies a modification to the steam balances leads to a requirement for a complex decision on the best operational response for the overall steam system [19].…”