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- Ek Fälth, Hanna, 1992
(författare)
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Insights from modeling renewable electricity systems and developing hydropower models
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One strategy for reaching a carbon-neutral electricity system is a large-scale deployment of wind and solar power. However, electricity systems with high shares of wind and solar power rely on other technologies, e.g., transmission and hydropower, to ensure that demand can be met at all times despite weather-dependent wind and solar power production. Moreover, the deployment of some technologies may be limited by public concern and land availability, which could increase the cost of decarbonizing electricity systems. To analyze designs and costs for future electricity systems with high shares of renewables, energy system models are crucial. In such models, the representation of hydropower is often significantly simplified, overestimating how flexibly hydropower can operate and, thereby, the hydropower’s ability to complement wind and solar power production. This thesis has two overarching aims addressed separately in the two appended papers. First, to explore how deployment limits on wind and solar power, transmission, and nuclear power each affect the cost of future carbon-neutral electricity and how it differs between the Middle East and North Africa region (MENA) and Europe (Paper A). Second, to investigate the accuracy of the hydropower representations used in energy system models and to develop a method for a more accurate hydropower representation (Paper B). In Paper A, we use an energy system model to show that the cost of a carbon-neutral electricity system is considerably lower in MENA than in Europe, which we link to MENA’s better wind and solar resource potential. Also, limiting the deployment of wind and solar power, transmission, or nuclear power can significantly affect system costs. However, the effect is markedly different in the two regions. Paper B examines how realistic different hydropower representations are by developing hydropower optimization models with different levels of detail and comparing them. We find that simple hydropower representations, such as those often used in energy system models, result in unrealistic production profiles and exaggerate the flexibility that hydropower can provide. In addition, we contribute a novel computationally efficient hydropower model that entails a more realistic hydropower production.
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| 2. |
- Ek Fälth, Hanna, 1992, et al.
(författare)
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MENA compared to Europe: The influence of land use, nuclear power, and transmission expansion on renewable electricity system costs
- 2021
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Ingår i: Energy Strategy Reviews. - : Elsevier BV. - 2211-467X. ; 33
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Tidskriftsartikel (refereegranskat)abstract
- Most studies that examine CO2-neutral, or near CO2-neutral, power systems by using energy system models investigate Europe or the United States, while similar studies for other regions are rare. In this paper, we focus on the Middle East and North Africa (MENA), where weather conditions, especially for solar, differ substantially from those in Europe. We use a green-field linear capacity expansion model with over-night investment to assess the effect on the system cost of (i) limiting/expanding the amount of land available for wind and solar farms, (ii) allowing for nuclear power and (iii) disallowing for international transmission. The assessment is done under three different cost regimes for solar PV and battery storage. First, we find that the amount of available land for wind and solar farms can have a significant impact on the system cost, with a cost increase of 0–50% as a result of reduced available land. In MENA, the impact on system cost from land availability is contingent on the PV and battery cost regime, while in Europe it is not. Second, allowing for nuclear power has a minor effect in MENA, while it may decrease the system cost in Europe by up to 20%. In Europe, the effect on system cost from allowing for nuclear power is highly dependent on the PV and battery cost regime. Third, disallowing for international transmission increases the system cost by up to 25% in both Europe and MENA, and the cost increase depends on the cost regime for PV and batteries. The impacts on system cost from these three controversial and policy-relevant factors in a decarbonized power system thus play out differently, depending on (i) the region and (ii) uncertain future investment costs for solar PV and storage. We conclude that a renewable power system in MENA is likely to be less costly than one in Europe, irrespective of future uncertainties regarding investment cost for PV and batteries, and policies surrounding nuclear power, transmission, and land available for wind- and solar farms. In MENA, the system cost varies between 42 and 96 $/MWh. In Europe, the system cost varies between 51 and 102 $/MWh.
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| 3. |
- Ek Fälth, Hanna, 1992, et al.
(författare)
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Trade-offs between aggregated and turbine-level representations of hydropower in optimization models
- 2023
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Ingår i: Renewable and Sustainable Energy Reviews. - 1879-0690 .- 1364-0321. ; 183
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Tidskriftsartikel (refereegranskat)abstract
- To model a future power system with high shares of variable renewables, it is essential to capture the flexibility of dispatchable technologies such as hydropower. However, the representation of hydropower is often oversimplified in energy system investment models, such that the flexibility of hydropower is significantly exaggerated. This suggests the need for improved representations of hydropower that capture physical river dynamics but are computationally efficient to maintain the tractability of large models. Here, we develop a series of hydropower optimization models for a single river with various levels of techno-physical detail to evaluate options for hydropower representations in energy system investment models. All models operate hourly over a full year with perfect foresight. We explore trade-offs between accuracy and computational time involved in including features such as the river network, head-dependent power production, and discharge-dependent turbine efficiencies. We find that the level of detail significantly affects the optimal production and confirm that a simplistic hydropower representation similar to those often used in investment models significantly overestimates the flexibility of hydropower. The most detailed nonconvex model includes a full river network, head-dependency, and turbine efficiencies and is solved in just one hour on a modern desktop computer. Furthermore, we linearize this detailed model, thereby reducing computation time to one minute while featuring production dynamics substantially more similar to the full nonconvex model than a naive linear network model. These contributions pave the way for improving hydropower representations in investment models to avoid overestimating the flexibility that hydropower may provide.
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| 4. |
- Hassanzadeh Moghimi, Farzad, 1994-, et al.
(författare)
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Climate Policy and Strategic Operations in a Hydro-Thermal Power System
- 2023
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Ingår i: Energy Journal. - : International Association for Energy Economics (IAEE). - 0195-6574 .- 1944-9089. ; 44:5, s. 67-94
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Tidskriftsartikel (refereegranskat)abstract
- Decarbonisation of the Nordic power sector entails substantial variable renewable energy (VRE) adoption. While Nordic hydropower reservoirs can mitigate VRE output's intermittency, strategic hydro producers may leverage increased flexibility requirements to exert market power. Using a Nash-Cournot model, we find that even the current Nordic power system could yield modest gains from strategic reservoir operations regardless of a prohibition on "spilling" water to increase prices. Instead, strategic hydro producers could shift generation from peak to off-peak seasons. Such temporal arbitrage becomes more attractive under a climate package with a €100/t CO2 price and doubled VRE capacity. Since the package increases generation variability, lowers average prices, and makes fossil-fuelled plants unprofitable, strategic hydro producers face lower opportunity costs in shifting output from peak to off-peak seasons and encounter muted responses from price-taking fossil-fuelled plants. Hence, a climate package that curtails CO2 emissions may also bolster strategic hydro producers' leverage.
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