Sector coupling of the electricity and district heating system of Gothenburg - Integrating electric boilers in a multi-zone district heating model

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Examensarbete för masterexamen
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2022
Författare
Haagensen Thornström, Tim
Larsson, Viktor
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To lower emissions of green house gases, Göteborg Energi AB plans to retire their fossil-fueled heat generation. To replace this generation, one possibility can be to utilise the existing electricity grid via power to heat generation. This master’s thesis investigates the possibility for electrical boliers (EB)s to support the district heating system (DHS) by evaluating economical viability, geographical placements and the role EBs can take in heat generation. A techno-economical model of the DHS in Gothenburg was developed using linear programming in the software, General Algebraic Modeling System (GAMS). The modeled DHS of Gothenburg was divided into seven zones to account for bottlenecks within the DHS and the availability in the electricity system. Data was gathered from Göteborg Energi AB and Göteborg Energi Nät AB to depict the DHS during the period 2020-09-01 to 2021-04-30. The objective function was set to minimize the cost of heat generation while fulfilling the heat demand. With the possibility to invest in EBs, the model evaluated their competitiveness. Different cases and scenarios were studied, such as the implementation of possible future plants, reducing the energy tax on electricity, increasing fuel prices and the availability of electricity. The results indicate that the operational cost are an important factor for the competitiveness of EBs which can be seen when looking at scenarios with lowered energy tax. For cases and scenarios that don’t change the variable costs for the investigated period, the model only invests in EBs to fulfill the heat demand if no other option are available. When in use the EBs mostly contribute to heat generation during peak hours, yet, only when there is a low electricity price and sufficient grid capacity. Results show that EBs can be utilised as backup heat generation to a certain extent in all zones, but at different installed capacities. With the conditions from the investigated period, EBs are not economically viable nor are they needed to fulfill the heat demand. Changing the conditions, the EB can become economically viable, and for these scenarios the EBs act as a combination of peak heat- and intermittent heat generation. The zones West, Frölunda and North are most of interest for installing EBs. The results show that with increased cost for bio-oil, an investment of about 30MW in North is interesting to further investigate. The model also showed a need for additional heating in West and Frölunda, but with less economical incentives for an investment in EBs due to cheaper heat generation in adjacent zones. The Frölunda zone was also more constrained when it came to available electricity.
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