Wedoany.com Report-Nov. 18, Sunnic Lighthouse, a subsidiary of Enerparc, together with flexibility provider Entelios and transmission system operator 50Hertz, has successfully prequalified the 37.4 MW Schkölen solar park in Thuringia, Germany, for participation in the secondary control reserve market. During the past week, the plant has already delivered up to 25 MW of both positive and negative automatic frequency restoration reserve (aFRR).

This marks the first time a photovoltaic installation has entered Germany’s secondary reserve segment. The partners stated that the Schkölen project sets new benchmarks for renewable energy integration, with three further solar parks currently being prepared for similar qualification.

Managing Director of Sunnic Lighthouse, Arved von Harpe, explained that any large solar plant can participate individually, while smaller facilities can qualify through aggregation. He noted that connecting multiple sites creates additional redundancy and that the Schkölen park still maintains considerable operational buffer despite providing the maximum 25 MW reserve capacity.

The aFRR service requires full power delivery within five minutes and sustained availability for 15 minutes. Tenders are currently awarded in four-hour blocks the day ahead, though the Federal Network Agency plans to introduce 15-minute blocks next spring, a change expected to benefit solar and wind generation.

The Schkölen plant can supply both upward and downward regulation. When grid frequency rises, output can be curtailed almost instantly; when frequency drops, previously reduced generation can be rapidly restored. Under favourable solar conditions, response times can surpass those of conventional gas units or large industrial consumers.

Real-time visibility of available balancing capacity, which varies with weather and time of day, has been the main technical hurdle. The consortium developed dedicated metering arrangements, data systems, and AI-based forecasting tools in close cooperation. Entelios adapted the park’s control infrastructure for aFRR requirements.

Entelios CEO Fabian Becker described the project as “a true milestone – and proof of what is possible when technological innovation meets collaborative partnership.” Both companies highlighted the proactive role played by 50Hertz, which initiated the effort two years ago after earlier attempts to enable solar-based reserve provision had stalled.

From an economic perspective, the partners noted that solar parks can often offer secondary reserve at competitive cost, especially during periods of high generation. The additional revenue stream complements existing power purchase agreements or market sales, strengthening the business case for photovoltaic projects while supporting overall grid stability.