Thermal storage valuation in Gothenburg district heating system
Ladda ner
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Sustainable energy systems (MPSES), MSc
Publicerad
2023
Författare
Håkansson, Pontus
Johansson, Ludvig
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Göteborg Energi has invested in an accumulator tank for their district heating system
in Rya. This accumulator tank needs further investigation about cost-efficiency
and best usage. The study’s goal is to investigate the profitability of the installed
accumulator tank and see if future accumulator tank investment is a profitable solution.
The district heating network is divided into different nodes which are connected by
water pipes, and different plants/units are found at different nodes. The units have
different fuels, start times, start costs, efficiencies, and limitations which makes
these units more or less expensive to run. In this work, the combined heat and
power (CHP) plants have decided to have a restricted minimum load, and the rest
of the units have a flexible load. The different generation units are heat-only boilers
(HOB), CHPs, and heat pumps (HP).
The method was set up to calculate the minimum annual cost of generation in three
different cases with different input values. These cases are 2019, 2030, and 2030
new investments where the differences are that 2019 is the current system and is
modeled with an accumulator tank and without. The 2030 case is based on Göteborg
Energi’s prognosis of how the new installment of units will look in 2030. Here
the comparison was made between the current accumulator installed and the possibility
of new accumulator investments in the system. The last case was like the
2030 case, but instead of the 2030 prognosis of installed units, the model invested
in three categories of plants (HOB, HP, and CHP), where the units still in service
from 2019 remained. A sensitivity analysis was also made in all these cases where
the fuel prices were varied.
The 2019 case showed a saving of 1.55 MAC, and in both cases, investments in new
accumulator tanks were made, especially in nodes 5 and 6, which are in the north
and eastern districts of Gothenburg. The sensitivity also showed that accumulator
tanks are profitable even though bigger fuel price fluctuations occur.
One important discovery in the study was that bottlenecks were decreased with the
help of accumulator tanks. In contrast, plants further up the merit order decreased
production when more accumulator tanks were available. Also, electricity-dependent
heat generation units have good integration with this kind of thermal storage because
of the higher use of heat pumps and CHPs when accumulator tank capacity
increases.
One of the study’s conclusions is that the current accumulator tank is profitable and
has a payback of approximately 11 years, and investing in more accumulator tanks
would decrease the cost of the district heating system.
Beskrivning
Ämne/nyckelord
Accumulator tank , Thermal energy storage , District heating system , Node division , Bottlenecks