Asset substitution over system redesign
Across the region, the shift away from coal is described as asset substitution within an unchanged framework rather than a full redesign of system architecture. Land and grid access tied to thermal plants are being repurposed for renewable development, including cases where ash disposal areas are converted for solar deployment. In parallel, retired thermal grid connections are being reused to host battery energy storage systems. While these changes can look like a clean technology swap, they preserve key operational assumptions from the coal era.
The inherited framework includes large connection capacity, centralized dispatch points, and reliance on fast-ramping thermal support. In practice, this means new generation is expected to integrate alongside controllable resources that can respond quickly when variability increases. Electricity.Trade highlights that solar and wind connected to legacy substations are therefore planned to coexist with dispatchable backup rather than replace it. This affects how developers scope technical studies and how operators plan reserves and balancing services.
Serbia’s Obrenovac solar reuse and dispatch expectations
One emblematic case is Serbia’s Nikola Tesla A complex in Obrenovac, where ash disposal areas are being prepared for large-scale solar deployment. The project is positioned as a strategic reuse of land and existing grid access to align decarbonisation goals with asset efficiency. However, Electricity.Trade notes that the system logic remains largely unchanged from a power-system operations perspective. The connection is sized for thermal output, dispatch remains centralized, and the operating environment assumes fast, controllable backup availability.
For engineering teams preparing feasibility work and grid studies, that assumption matters for what flexibility must be available at system level. It also influences how EPC preparation teams structure interface requirements between new solar generation, existing substations, and any required balancing support. Even when the generation mix changes materially on paper, the operational envelope expected by the network can continue to align with gas-fired response.
Bulgaria’s Maritsa East 3 battery anchored to thermal infrastructure
Bulgaria’s Maritsa East 3 site illustrates how battery energy storage can be integrated using legacy plant connectivity. The location hosts one of the largest battery energy storage systems in the region: a 202 MW / 500 MWh installation. Electricity.Trade reports that the battery uses the legacy grid connection of the former coal plant, enabling immediate market participation without new transmission investment. This approach can reduce capital expenditure needs associated with grid expansion.
At the same time, Electricity.Trade argues that such reuse reinforces a thermal-centric system design rather than displacing gas balancing roles. The battery is described as not replacing gas; instead it optimizes gas utilization by shaving peaks and smoothing ramps. Multi-day balancing responsibilities are left to gas units, which has implications for how reserve procurement and system services are planned during commissioning and operations.
Why coal-era design criteria shape flexibility needs
Electricity.Trade links the persistence of gas dependency to how coal infrastructure was originally designed for dispatchability rather than intermittency. Successor technologies connected to coal-era substations inherit expectations about controllability and response times from thermal operations. Solar and wind are therefore integrated under frameworks that assume coexistence with controllable resources. Nuclear, where present, is characterized as providing baseload but lacking ramping flexibility, while hydro flexibility depends on weather conditions.
In this context, gas is described as fitting the inherited operational envelope more naturally than other options. The analysis further emphasizes that inheritance effects are reinforced by regulatory and technical frameworks developed around thermal generation. Grid codes, protection schemes and market rules evolved with thermal plants in mind, so repurposing coal assets without redesigning these frameworks can tilt outcomes toward gas as the practical balancing solution.
Operational planning, studies and procurement consequences
The implications extend beyond generation assets into day-to-day operational delivery planning. Maintenance schedules, reserve procurement approaches, balancing market design choices and system service requirements are all calibrated around an assumption of fast thermal response capability. If coal capacity is removed without equivalent redesign of these processes, Electricity.Trade argues that a flexibility vacuum emerges that gas fills by default.
Financing structures can also strengthen path dependency during project execution readiness stages. Coal assets are depreciated and their grid connections become sunk costs that reduce barriers for repurposing land for solar or storage projects. Repurposing existing connectivity can minimize capital expenditure exposure and regulatory complexity compared with building new transmission interfaces. Meanwhile, gas plants—often already present or accessible through imports—provide flexibility without requiring new build on the same scale as renewables’ grid integration requirements.
Broader industry implications for developers and investors
Electricity.Trade concludes that South-East Europe’s transition should be viewed less as a direct coal-to-renewables break and more as coal-to-gas-mediated renewables under current design constraints. Until system architecture is redesigned around decentralization, long-duration storage or fundamentally flexible nuclear resources, gas may remain structurally locked in by design rather than by explicit choice. For developers and contractors preparing EPC packages and integration studies, this points to a need for early alignment between renewable interconnection plans and system-level flexibility procurement assumptions.
For utilities and industrial stakeholders evaluating investment planning risk, the message is that technology substitution alone may not change operational outcomes if grid modernization does not address dispatch logic end-to-end. Battery projects using legacy connections can accelerate execution readiness by avoiding new transmission investment, but they may still operate within thermal-shaped balancing structures unless market rules and network capabilities evolve in parallel.