Optimal Cooling Load Sharing Strategies for Different Types of Absorption Chillers in Trigeneration Plants

Abstract

Trigeneration plants can use different types of chillers in the same plant, typically single effect and double effect absorption chillers, vapour compression chillers and also cooling storage systems. The highly variable cooling demand of the buildings connected to a district heating and cooling (DHC) network has to be distributed among these chillers to achieve lower operating costs and higher energy efficiencies. This problem is difficult to solve due to the different partial load behaviour of each chiller and the different chiller combinations that can cover a certain cooling demand using an appropriate sizing of the cooling storage. The objective of this paper is to optimize the daily plant operation of an existing trigeneration plant based on cogeneration engines and to study the optimal cooling load sharing between different types of absorption chillers using a mixed integer linear programming (MILP) model. Real data from a trigeneration plant connected to a DHC close to Barcelona (Spain) is used for the development of this model. The cooling load distribution among the different units is heavily influenced by the price of the electricity sold to the grid which rules the duration of the operation time of the engines. The main parameter to compare load distribution configurations is the primary energy saving indicator. Cooling load distribution among the different chillers changes also with the load of the whole plant because the chiller performance changes with load.

Thermodynamic and Economic Analysis of Trigeneration System Comprising a Hierarchical Gas-Gas Engine for Production of Electricity, Heat and Cold

“…The objective of the paper [13] is to optimize the daily plant operation of an existing trigeneration plant based on cogeneration engines and to study the optimal cooling load-sharing between different types of absorption chillers using a mixed integer linear programming (MILP) model.…”

An operational optimization method for a complex polygeneration plant based on real-time measurements

“…where & = 1, 2, … , ', and I H " are binary variables equal to 1 when the m-th system component is on and equal to 0 when it is off. Therefore, equations (23,25,27,29) define the maximum output capacity of the relevant machine, and equations (24,26,28) impose that the minimum allowable load factors are respected.…”

Simulation of Polygeneration Systems

“…Nevertheless, the management of such systems is not trivial, since power, thermal and cooling demands may significantly vary during the day. This problem was addressed by Conte et al [30], who investigated the optimal management of absorption chillers integrated into trigeneration systems. Their study starts from the analysis of the state of the art, showing that, in many cases, modularity and flexibility of modern and efficient trigeneration systems are not sufficient to properly work in DHC when the partial load ratio is very low.…”

“…However, this simple control strategy may be significantly improved using optimized sharing load approaches, as shown by several studies available in literature. The novelty of the work presented by Conte et al [30] lies in the utilization of real data taken from an existing trigeneration plant located near Barcelona (Spain). Thermal and cooling capacities are 1.40 MW and 8.75 MW, respectively.…”