Techno-Economic Assessment of a Hybrid Wind-Solar-Battery System in Nordic Conditions: Market participation in the Finnish day-ahead and imbalance markets
Sutradhar, Nanda (2025)
2025
Sähkötekniikan DI-ohjelma - Master's Programme in Electrical Engineering
Informaatioteknologian ja viestinnän tiedekunta - Faculty of Information Technology and Communication Sciences
Hyväksymispäivämäärä
2025-12-29
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-2025122912185
https://urn.fi/URN:NBN:fi:tuni-2025122912185
Tiivistelmä
Hybrid renewable energy systems combining wind power, solar photovoltaics (PV), and battery energy storage systems (BESS) are considered one of the means to reduce output variability and smooth the power profile of variable renewable generation. In Finland, where renewable producers rely on the Nord Pool Day-Ahead market and settle deviations through Fingrid’s imbalance pricing, the economic feasibility of hybrid systems depends strongly on forecasting accuracy and the ability to manage imbalance risk. This thesis develops a data-driven techno-economic modelling framework to evaluate the operational and financial performance of a hybrid wind–solar–battery system under real Finnish market conditions.
The study uses hourly ERA5 meteorological data, Nord Pool Day-Ahead prices, and Fingrid imbalance prices for the year 2024 (a total of 8758 hours) to simulate three hybrid plant sizes: 5 MW, 10 MW, and 20 MW. Renewable generation is modelled using established PV temperature-corrected efficiency equations and an IEC-based wind turbine power curve. A BESS sized at 50% of plant power rating with a two-hour duration is intentionally assumed as a stress-case configuration to evaluate the technical limits of imbalance mitigation; its economic profitability is assessed ex post through annual profit and NPV analysis. Day-ahead schedules are generated using a 24-hour rolling-mean of realized meteorological data, representing producer expectations of next-day generation rather than a full operational weather
forecast-based bidding model. For each scenario, the model computes a full-year time series of generation, battery operation, deviations from schedule, imbalance settlement, and total annual profit.
The results show strong seasonal complementarity between wind and solar resources in Finnish conditions, with wind dominating winter production and solar contributing meaningfully during summer. The BESS is technically effective, reducing total absolute imbalance energy by approximately 40% (39.7%) across all system sizes. Under the implemented imbalance settlement logic, this reduction also decreases the net annual imbalance settlement penalty and increases annual market profit in all cases (e.g., for the 5 MW system from approximately €10,245/yr without BESS to €21,266/yr with BESS). However, the absolute profit levels remain small relative to realistic CAPEX, OPEX, and battery replacement costs, and the discounted cash-flow analysis yields strongly negative NPVs, indicating that imbalance-mitigation-only operation is insufficient to justify battery investment under Finnish 2024 market conditions.
The thesis concludes that hybrid wind–solar systems are technically promising in Nordic climates, while economically viable BESS deployment generally requires access to additional value streams-such as frequency reserves, intraday trading, or price-aware dispatch-beyond imbalance reduction alone.
The study uses hourly ERA5 meteorological data, Nord Pool Day-Ahead prices, and Fingrid imbalance prices for the year 2024 (a total of 8758 hours) to simulate three hybrid plant sizes: 5 MW, 10 MW, and 20 MW. Renewable generation is modelled using established PV temperature-corrected efficiency equations and an IEC-based wind turbine power curve. A BESS sized at 50% of plant power rating with a two-hour duration is intentionally assumed as a stress-case configuration to evaluate the technical limits of imbalance mitigation; its economic profitability is assessed ex post through annual profit and NPV analysis. Day-ahead schedules are generated using a 24-hour rolling-mean of realized meteorological data, representing producer expectations of next-day generation rather than a full operational weather
forecast-based bidding model. For each scenario, the model computes a full-year time series of generation, battery operation, deviations from schedule, imbalance settlement, and total annual profit.
The results show strong seasonal complementarity between wind and solar resources in Finnish conditions, with wind dominating winter production and solar contributing meaningfully during summer. The BESS is technically effective, reducing total absolute imbalance energy by approximately 40% (39.7%) across all system sizes. Under the implemented imbalance settlement logic, this reduction also decreases the net annual imbalance settlement penalty and increases annual market profit in all cases (e.g., for the 5 MW system from approximately €10,245/yr without BESS to €21,266/yr with BESS). However, the absolute profit levels remain small relative to realistic CAPEX, OPEX, and battery replacement costs, and the discounted cash-flow analysis yields strongly negative NPVs, indicating that imbalance-mitigation-only operation is insufficient to justify battery investment under Finnish 2024 market conditions.
The thesis concludes that hybrid wind–solar systems are technically promising in Nordic climates, while economically viable BESS deployment generally requires access to additional value streams-such as frequency reserves, intraday trading, or price-aware dispatch-beyond imbalance reduction alone.