Implementation and optimisation of thermal storage in existing, large-scale district heating networks

Implementation and optimisation of thermal storage in existing, large-scale district heating networks

de Vries, Auke (TU Delft Mechanical, Maritime and Materials Engineering)

Infante Ferreira, C.A. (mentor)

Delft University of Technology

Mechanical Engineering

2018-10-23

District heating networks (DHN) are frequently considered an alternative heating solutions in the energy transition. The implementation of thermal storage in large-scale, existing, district heating networks was researched in this study. Thermal storage was found to enable the incorporation of sustainable heat sources and optimise fuel usage in DHN. Two storage configurations were investigated: a centralised configuration where the storage is located at the primary heat generation equipment and a decentralised storage configuration where several storage vessels are distributed throughout the network. Water was selected as storage material due to economic and operational advantages over the alternatives.
A thermodynamic model was designed, in MATLAB, based on the dimensions of the district heating network of Utrecht in The Netherlands. All generation assets, heat transfer equipment and transport pipelines were modelled and validated using measurement data. With the proposed model, the thermodynamic behaviour of the network was optimised over 6, carefully selected, scenario weeks.
The simulations of realistic centralised and decentralised thermal storage configurations resulted in a maximal thermal peak reduction of 101 MW and 106 MW respectively and an equalised thermal generation profile over the course of each day. The heat generation of backup boilers was reduced with 20% simulating centralised storage and 58% by decentralised storage. The network temperature was decreased simulating decentralised storage but increased in the centralised configuration.
The development of the thermocline in a thermal storage vessel was investigated through a data analysis over the Ypenburg (Den Haag) thermal storage vessel (1500 m3). With the implementation of adequate control, the volume percentage occupied by the thermocline can be maintained below 10%. Trends in rapid thermocline growth were observed when only 20% to 40% of the buffer volume was frequently refreshed.
Lastly, an economic optimisation was performed over the year 2017 using the cooperative Eneco and TU-Delft software Linny-R. The net result over 2017 was improved with €306000 simulating centralised storage and €583000 simulating decentralised storage. Decentralised storage enabled a decrease in supply temperature which generated an additional revenue of €104000 over the 4 modelled scenario weeks in 2017.
As a partial result of this work, Eneco is in the process of the actual implementation of decentralised thermal storage in the Utrecht district heating network.

Thermal storage
district heating
phase change material
Eneco
Utrecht
network
sustainabilit

http://resolver.tudelft.nl/uuid:7afa2698-0a89-4b4c-8cd9-110aa3fd6497

2023-10-23

Student theses

master thesis

© 2018 Auke de Vries