Firm PV generation through optimized trading and forecasting: Economic and system flexibility impacts

The growing penetration of variable renewable energy increases the need for strategies that reduce solar-induced flexibility requirements with reliable photovoltaic supply. This study investigates cost-effective trading strategies for utility-scale photovoltaic/smart inverter/battery systems (flexible PV plants) to deliver firm and predictable power to the day-ahead electricity market. An important novelty is the introduction of dedicated key performance indicators for assessing solar supply quality: certainty of supply, supply variability and solar-induced flexibility required from the power system. These metrics are used to compare annual and monthly baseload commitments, forecast-corrected/optimized offers against unconstrained PV supply. Results show that while the provision of a PV baseload 24/365 with 99 % of certainty of supply shows near zero variability and solar-induced flexibility, the minimum production cost is 320 €/MWh firming just 30 % of the unconstrained PV generation. In contrast, forecast-based strategies provide near-firm solar power at costs of 128 and 149 €/MWh while firming 62–72 % of solar generation still ensuring a high supply certainty and low system flexibility requirements. An additional strategy, based on the trading of not only firm output but also the residual variable component (generation splitting), further improves economic performance bringing total production costs closer to market parity while having solar-induced reserves.