Multi-period MINLP model for optimising operation and structural changes to CHP plants in district heating networks with long-term thermal storage

By using thermal storages it is possible to decouple the generation of power and heat, and it can also lead to an reduction in investments, as the storage can be used to cover the peak load periods. This work presents a MINLP model that can be used for analysing new investments and the long-term ope...

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Bibliographic Details
Published in:Energy conversion and management 2009-03, Vol.50 (3), p.639-647
Main Authors: Tveit, Tor-Martin, Savola, Tuula, Gebremedhin, Alemayehu, Fogelholm, Carl-Johan
Format: Article
Language:English
Subjects:
Applied sciences
Combined heat and power
District heating
District heating and refrigerating
Economic data
Energy
Energy economics
Energy. Thermal use of fuels
Exact sciences and technology
General, economic and professional studies
Heating, air conditioning and ventilation
Long-term thermal storage
Methodology. Modelling
Multi-period MINLP model
Natural energy
Space heating. Hot water
TECHNOLOGY
TEKNIKVETENSKAP
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Summary:By using thermal storages it is possible to decouple the generation of power and heat, and it can also lead to an reduction in investments, as the storage can be used to cover the peak load periods. This work presents a MINLP model that can be used for analysing new investments and the long-term operation of CHP plants in a district heating network with long-term thermal storage. The model presented in this work includes the non-linear off-design behaviour of the CHP plants as well as a generic mathematical model of the thermal storage, without the need to fix temperatures and pressure. The model is formulated in such a way that it is suitable for deterministic MINLP solvers. The model is non-convex, and subsequently global optimality cannot be guaranteed with local solvers. In order to reduce the chance of obtaining a poor local optimum compared to the global optimum, the model should be solved many times with the initial values varying randomly. It is possible to extract a lot of results from the model, for instance total annual profit, the optimal selection of process options, mass flow through the plant, and generated power from each plant. The formulation of the model makes it suitable for deterministic MINLP solvers.
ISSN:0196-8904
1879-2227
DOI:10.1016/j.enconman.2008.10.010