Functional Description – Pala Agri-PV Hybrid Solar Power Plant
1. Installation Site
The proposed hybrid solar power plant is intended to be installed in the municipality of Pala, Department of Mayo-Dallah, Mayo-Kebbi Ouest Region, Chad.
The final design of foundations, drainage and site infrastructure shall take into account the actual local ground, geotechnical and hydrological conditions. The overall plant layout shall combine photovoltaic electricity generation with continued agricultural use of the land.
The Agri-PV mounting structures and foundations shall be designed taking into account local environmental, drainage and flooding conditions. The minimum vertical clear distance between finished ground level and the lowest edge of any PV module shall be at least 2.5 m. The minimum clear horizontal distance between structural posts/supports within areas intended for agricultural access shall be at least 4 m The arrangement shall maintain safe and practical access for agricultural activities underneath and between the PV module rows.
The climatic conditions impose demanding thermal and environmental requirements on the equipment. All equipment shall therefore be suitable for the specified ambient temperatures, humidity, dust exposure and other environmental conditions. Where required, appropriate cooling, ventilation, filtration and other protective measures shall be provided in accordance with the Detailed Technical Specifications.
2. Functional Specifications
Agri-PV Solar Array
The PV array shall be designed as an agrivoltaic (Agri-PV) ground-mounted system allowing the continued cultivation of market-garden crops underneath and between the PV module rows.
The system shall use semi-transparent PV modules suitable for agrivoltaic application. The arrangement of module tables, row spacing, module transparency, inclination and orientation shall be coordinated to provide an appropriate distribution of solar radiation on the cultivated area while achieving the required electricity generation.
The Bidder shall propose a preliminary Agri-PV site layout and a preliminary shading / solar-radiation analysis at crop level. The layout shall minimise permanent obstruction of cultivable land and provide suitable access for soil preparation, planting, irrigation, crop maintenance, harvesting and plant maintenance.
The Bidder may propose either reinforced concrete foundations or a driven-pile foundation system, provided that the proposed solution is structurally suitable for the site conditions and the Agri-PV mounting system. The foundation concept shall minimise the loss of cultivable land and unnecessary obstacles to agricultural activities.
The mounting structure shall be designed for the proposed PV modules, module arrangement, inclination, environmental conditions and applicable structural loads. Rainwater management, cable routing, earthing and other interfaces shall be designed so as not to interfere unnecessarily with agricultural use.
The minimum installed capacity of the PV array shall be 2 MWp. Depending on the proposed module technology and transparency, the installed capacity may exceed this value but shall under no circumstances be less than 2 MWp. Detailed requirements are defined in the Detailed Technical Specifications.
Diesel Generator, 600 kW
A diesel generator shall provide dispatchable backup and complementary generation and shall be fully integrated with the PV plant and BESS/PCS through the central EMS/PMS.
The generator shall be suitable for coordinated operation with the other generation and storage sources of the hybrid power plant. Detailed capacity, performance, control, interface and other technical requirements are defined in the Detailed Technical Specifications.
PV Inverter System
Conversion of the DC power generated by the Agri-PV array shall be performed by a modular PV inverter system.
The inverter system shall provide the required conversion capacity and shall support parallel operation, multiple MPPTs, active and reactive power control, grid monitoring, remote control and full integration into the central EMS/PMS/SCADA system.
The inverter configuration shall be coordinated with the proposed semi-transparent PV modules, string configuration, transformers and overall electrical architecture of the plant and shall allow efficient and reliable operation under the specified site conditions.
Detailed electrical ratings, performance requirements, protection functions, communication interfaces and applicable standards are defined in the Detailed Technical Specifications.
Energy Storage
Energy storage shall be provided by a complete, factory-integrated Battery Energy Storage System (BESS) with a total usable energy capacity of at least 6 MWh, divided into two separate units of at least 3 MWh each.
The BESS may be installed in containers or other suitable purpose-built enclosures, provided that the proposed solution is suitable for transport, installation, operation and maintenance under the specified site conditions.
The BESS shall include the battery system, Battery Management System (BMS), thermal management, fire detection and suppression, electrical protection, monitoring, communication and auxiliary systems required for safe and autonomous operation.
The Power Conversion System (PCS) shall be integrated into or fully coordinated with the BESS and shall provide bidirectional conversion for charging and discharging of the batteries.
The BESS/PCS shall provide grid-forming capability and shall be capable of establishing and maintaining stable voltage and frequency in the local network without support from the diesel generator. It shall also provide black-start capability and coordinated parallel operation with the PV inverter system and diesel generator under control of the EMS/PMS.
Detailed technical, safety, performance, enclosure and interface requirements are defined in the Detailed Technical Specifications.
Transformers and MV Connection
The power plant shall include a 5 MVA step-up transformer, MV switchgear, protection, metering and associated equipment required for connection of the PV/BESS system and diesel generator to the 20kV public distribution network. All equipment and the overall connection concept shall comply with the technical and safety requirements applicable to public electricity networks in Chad, as well as with the applicable IEC standards.
The transformers, switchgear and protection system shall be suitable for the proposed hybrid plant architecture and the required power flows between the generation sources, storage system and distribution network.
Final grid parameters, protection settings, metering requirements, communication interfaces and the point of common coupling shall be coordinated with and confirmed by SNE or the competent grid operator.
Detailed requirements are defined in the Detailed Technical Specifications.
Central Control System
A central Energy Management System / Power Management System (EMS/PMS) shall coordinate the operation of the Agri-PV plant, BESS/PCS and diesel generator.
The EMS/PMS shall manage the main functions required for stable and coordinated hybrid operation, including source synchronization, connection and disconnection of generation sources, active and reactive power management, voltage and frequency control, BESS charge/discharge and State of Charge management, PV power limitation and black-start operation.
The system shall interface with the relevant protection devices, circuit breakers, meters, equipment controllers and the overall monitoring/SCADA system.
Detailed functional, communication, monitoring and control requirements are defined in the Detailed Technical Specifications.
3. Main Characteristics of the Installation
The proposed configuration shall establish a stable local electricity supply system based primarily on solar generation and battery storage, complemented by dispatchable diesel generation, while preserving the agricultural use of the Agri-PV area.
The main functional characteristics of the plant are:
- Agri-PV array: minimum installed capacity of 2 MWp using semi-transparent PV modules suitable for cultivation of market-garden crops underneath and between the module rows.
- Agri-PV mounting structure: minimum 2.5 m clear height below the lowest module edge and layout designed to preserve agricultural access and cultivable land. The minimum clear horizontal distance between structural posts/supports within areas intended for agricultural access shall be at least 4 m
- PV inverter system: modular inverter configuration in accordance with the Detailed Technical Specifications, 1,5 MW
- BESS: minimum usable energy capacity of 6 MWh, divided into two separate units of at least 3 MWh each, installed in containers or other suitable purpose-built enclosures.
- PCS: 1 MW x 2 bidirectional power conversion system, integrated into or fully coordinated with the BESS
- Grid-forming and black-start capability provided by the BESS and PCS.
- Diesel generator, 600 kW, providing dispatchable backup and complementary generation.
- Central EMS/PMS for coordinated operation of the Agri-PV plant, BESS/PCS and diesel generator.
- Step-up transformer 5 MVA and MV switchgear for connection to the 20 kV public distribution network.
- Protection, metering, monitoring and communication systems suitable for operation of the complete hybrid power plant and its connection to the public electricity network.
- Compliance with the technical and safety requirements applicable to public electricity networks in Chad, the requirements of the competent grid operator and the applicable international standards.
All equipment shall be mutually compatible and form a complete and technically coordinated system. Detailed ratings, Agri-PV design requirements, component specifications, standards, documentation requirements and interfaces are defined in the Detailed Technical Specifications (xls). The detailed technical specifications provided in Excel format shall constitute the final and authoritative reference for all technical requirements. A functional diagram of the system is provided on the following page.