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.
Highlights
Introduction and ObjectivesTrigeneration plants integrated into district heating and cooling (DHC) networks are a very efficient way to provide energy services with the exploitation of locally generated waste heat to produce heating and cooling in a very efficient way and delivering them to final users
Trigeneration plants connected to DHC networks are designed to operate in several modules of cogeneration engines that can be connected and disconnected to the system to account for this type of problems and the variability of the users demand
This paper presents a mixed integer linear programming (MILP) model of a trigeneration plant based on cogeneration engines
Summary
Trigeneration plants integrated into district heating and cooling (DHC) networks are a very efficient way to provide energy services with the exploitation of locally generated waste heat to produce heating and cooling in a very efficient way and delivering them to final users. The variable cooling load demand of the buildings connected to the DHC has to be distributed among these chillers to achieve lower operating costs and higher energy efficiencies This problem is even more difficult to solve taking into account the different partial load behavior of each chiller and the high number of possible unit combinations that can cover a given demand specially with the appropriate dimensioning of the cooling storage. The selection, number, and on/off status of operation of equipment are expressed by integer variables and the capacities and load allocation of equipment by continuous ones This model is used to optimize the daily plant operation and to study the optimal cooling load sharing between the different types of absorption chillers, compression chillers and cooling storage. A second objective of the paper is to study the efficiency of this type of trigeneration plants working at cooling load demands lower that 50% of its nominal capacity
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