Photovoltaic solar plant a 50 MW battery storage system is the infrastructure project that the Tunisian state-owned electricity company STEG has put out to tender for the Tataouine Governorate in southern Tunisia. The project includes a 10 MW battery storage system with 20 MWh of energy capacity, along with the necessary infrastructure for connecting to the high-voltage grid. The tender notice was published on October 9, 2026, on the ECEPP electronic portal.
The Tunisian Energy and Gas Company (STEG) is listed as the contracting entity, the announcement pertains to a single-stage open tender for construction work, so the plant should not yet be presented as built or awarded. Its scope combines renewable energy generation, storage, and transmission three components that must function in a coordinated manner to deliver electricity to the national grid.
The plant will have a planned photovoltaic capacity of 50 MW, this figure represents the installation’s generation capacity under reference conditions, but it does not equate to the energy produced in a single day. Actual production will depend on several factors, including available solar radiation, temperature, electrical losses, and operating conditions.
For their part, the batteries will have a power of 10 MW and a nominal energy capacity of 20 MWh, the first figure indicates how much electricity the system can deliver at a given time, the second indicates the amount of energy it can store. If it were discharged at its constant nominal power, it would have a theoretical duration of two hours, before considering operational limits and losses.
This distinction is important for understanding the project the 50 MW of solar power and the 10 MW of the BESS should not be automatically added together as if they were additional permanent generation capacity. The storage system manages previously charged energy, and its effective contribution will depend on how its charging and discharging are scheduled.
The notice identifies the process as a single-stage open tender for construction works, interested companies can consult the documentation through the ECEPP portal, after registering where applicable. There, they will find the technical, financial, and eligibility requirements that should guide the preparation of their bids.
The call for proposals was published on October 9, 2026, and sets December 10, 2026, at 9:00 a.m. as the closing date and time. Participants should check the electronic file for any subsequent clarifications or changes, as well as instructions on submitting proposals.
The announcement indicates that STEG plans to use some of the resources from a loan or grant administered by the European Bank for Reconstruction and Development to cover the cost of the contracts. However, the publication consulted does not provide the total budget, the start date of the works, or the commissioning schedule. This information should not yet be considered confirmed.
The initiative is located in the Tataouine governorate, in the south of Tunisia, choosing a site for solar energy requires evaluating the available resources and terrain conditions, but also its distance from the grid, access routes, and maintenance needs, these are relevant aspects for any installation of this scale.
In a solar operating environment, heat, dust, and dirt buildup can affect module performance, therefore, detailed engineering typically studies equipment selection, ventilation, cleaning procedures, and inspection frequency. The public notice does not specify what specific solutions will be used in Tataouine.
In addition, storage introduces its own monitoring needs, batteries require thermal control, electrical protection, and systems that monitor their state of charge. These elements contribute to maintaining adequate operating conditions, especially when the installation must respond to changes in solar production.
The plant requires infrastructure to carry electricity from the generating equipment to the grid connection point. The announced scope includes high-voltage installations and associated transmission lines. According to initial project information, a substation and approximately eight kilometers of 225 kV lines are planned.
The substation plays a central role in this system, enabling the transformation of voltage levels and providing switching, metering, and protection devices. This allows electricity to be transported under conditions compatible with the technical requirements of the network to which the complex will be connected.
On the other hand, transmission lines must be designed according to the route, required capacity, and applicable safety criteria. Protection and communication systems capable of detecting faults and coordinating equipment response are also needed. The public notice does not specify the exact interconnection point or the final design of these facilities.
Solar energy varies throughout the day and decreases when there is insufficient radiation, a Battery Energy Storage System (BESS) allows for the storage of some of the available production for later delivery, always within its capacity and the established operating limits. In Tataouine, a 20 MWh battery could be used to shift energy to periods of lower photovoltaic generation. It could also help smooth out certain delivery variations if the control strategy and the contract allow for it. These uses are technical possibilities of energy storage, not specific services confirmed in the contract announcement.
Furthermore, coordination between solar inverters, battery converters, and control systems will be crucial, scheduling must consider how much energy is generated, how much is stored, and when it is best to discharge it. Proper management aims to avoid unnecessary restrictions and leverage the grid infrastructure without exceeding its operational limits. Storage capacity also doesn’t mean the plant can continuously supply any demand for two hours, the nominal duration is calculated at a specific power output, while the actual usable energy can vary depending on efficiency, temperature, state of charge, and system safety conditions.
The execution of a complex of this type requires coordinating civil works, electromechanical installation and electrical work, in a photovoltaic plant the components include support structures, modules, inverters, cabling, and monitoring systems. In the BESS system, containers or cabinets, conversion equipment, and controls dedicated to battery safety are also included.
The high-voltage connection adds other tasks, such as protection testing, equipment verification, and commissioning of communication systems, it is not enough to install each component separately, it is also necessary to verify that the solar power plant, batteries, and substation respond correctly when operating together.
However, the design, testing, warranty, and maintenance requirements applicable to this tender must be verified in the official documents, the general notice refers to that document for complete specifications and the obligations that the winning bidder will assume.
For now, the main news is the opening of the competitive bidding process, not the start of construction, after the deadline for submitting bids, announcements regarding evaluation, awarding, and construction scheduling will follow. The available publication does not identify a winning contractor.
The project is notable for combining a 50 MW solar power plant, 10 MW/20 MWh batteries, and transmission infrastructure within a single project. If implemented according to the final contract terms, it could provide new renewable energy generation and time-of-use energy management options in southern Tunisia.
For companies in the sector, the crucial information will be in the technical file, which details the responsibilities for engineering, supply, construction, and testing, as well as the criteria that will determine the viability of the bids. Meanwhile, STEG’s call for tenders puts Tataouine on the map of opportunities for solar energy with storage in Tunisia.
Source: European Bank
Photo: Shutterstock
Moises Carrasquero is a mechanical engineer and writer specializing in technology, engineering, and industrial development, with a focus on the advancements that are transforming these sectors. My goal is to turn complex technical information into clear, accurate, and relevant journalistic content.
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