/LONDON, October 15, 2025, 11:45 BST, RENEWABLE MARKET WATCH™/ Work began in April 2025, and in September (of the same year), the phased construction was completed, with electrical tests beginning. Commercial operation is scheduled to begin in December 2025.
At Principia, it remains steadfast in its commitment to accelerating the energy transition through innovation, technology and sustainable investments. As part of this strategy, the company completed its first Battery Energy Storage System (BESS), a milestone project not only for the company but also for the entire Greek energy market. The unit, with the commercial name “Themelio”, is located in the Vouno area of Halkidiki, near Polygyros, and is one of the first BESS projects implemented in the country, integrated into the national plan for the stability and electrification of the energy system.
The power of the unit is 49MW, with an installed storage capacity of 127.04MWh and a guaranteed capacity of 98MWh for two hours, offering substantial flexibility to the grid. This capability allows for a better balance of supply and demand, enhancing the stability and efficiency of the electrical system.
The unit consists of 26 Sungrow battery containers, each with a maximum capacity of 5,015kWh and equipped with advanced CALB 314Ah cells. It also includes 13 Sungrow generation substations with 5,140kW power transformers and 33kV medium-voltage switchboards, as well as two medium-voltage terminal substations that ensure smooth and safe interconnection with the grid. Of particular importance is that, over 20,000 man-hours of work, no accidents occurred, confirming strict adherence to health and safety standards.
Principia’s “Themelio” energy storage unit brings tangible benefits to the Greek energy system and the market. First, it helps reduce curtailments from wind and photovoltaics, especially in areas with a saturated grid, by absorbing excess production and reintroducing it into the system when needed. Furthermore, it enhances system stability, providing power during peak hours and ensuring smooth grid operation.
At the same time, it promotes energy decentralisation by being located near RES production points, contributing to a more flexible and smart energy environment.
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