HYDROMECHANICAL SYSTEMS IN NEW vs. REHABILITATED HYDROPOWER SITES

Introduction

Hydropower plays a key role in global energy innovation, particularly in Africa, where hydropower potential is immense but underexploited. Hydromechanical systems, which encompass water flow control and regulation equipment, are essential to the performance of hydropower plants.

This article examines the differences between hydromechanical equipment used in Greenfield (new sites) and Brownfield (rehabilitation) projects, highlighting the specific challenges faced by African projects.

Hydropower remains the cornerstone of renewable energy, contributing 15% of global electricity and over 40% of sub-Saharan Africa's electricity supply. In Africa, where 90% of hydropower potential remains untapped, new (greenfield) and rehabilitated (brownfield) projects are essential to meet growing energy demand.

A thorough understanding of these tactical and operational challenges will enable African countries to adjust their energy policies with a view to achieving energy innovation that is more appropriate for their geoeconomic ecosystems.

1.Types of Hydromechanical Equipment

Hydromechanical equipment forms the backbone of hydroelectric power plants, enabling energy conversion and flow control. The main components include:

Turbines: Francis, Kaplan, Pelton, as well as emerging models such as Archimedes screw turbines and very low head (VLH) turbines, convert hydraulic energy into mechanical energy.

Valves and gates: (segments & Radials valves, butterfly valves, flap valves) regulate water flow and ensure safety.

Hydraulic structures: (penstocks filter screens, weirs) convey water to the turbines.

Control and regulation systems (automation, pressure and flow sensors).

Lifting and maintenance systems (gantry cranes, overhead cranes, hydraulic winches).

 Leading manufacturers such as Voith Hydro, GE Renewable Energy, and Andritz Hydro provide specialized equipment tailored to site conditions (EPRI, 2021).

In Africa, sedimentation and variable water flows require robust designs, particularly in regions such as the Congo Basin and the Nile Basin.

 Greenfield Projects

Greenfield projects involve the construction of new hydroelectric power plants.

In Africa, these projects are often located on rivers with high potential, such as the Nachtigal, the Nile, the Congo, or the Zambezi.

 Benefits include:

Technological optimization: Integration of the latest innovations in hydromechanics.

High-efficiency turbines, such as ANDRITZ Kaplan turbines, are chosen for their adaptability to variable flow rates, essential for Africa's erratic rainfall conditions. Modern automation and digital monitoring, as demonstrated by the Kafue Gorge Lower hydropower plant in Zambia, which incorporates IoT-based predictive maintenance (Andritz Hydro, 2023).

Environmental integration: Fish-friendly designs and low-head turbines minimize ecological impact, as demonstrated by the Mbei River project in Gabon.

Design flexibility: Adaptation to energy and environmental needs.

Increased durability: Use of modern, corrosion-resistant materials.

Cost and scalability: Greenfield projects require significant upfront investment.

Example: The Grand Inga project in the DRC, which aims to harness one of the world's largest hydropower potentials, the 650 MW Nam Theun in Laos, and the EDF-backed Nachtigal project, demonstrate advanced hydromechanical integration.

 Key considerations include:

Sediment management (critical in silt-laden rivers like the Niger)

Adaptability to climate variability (World Bank, 2020)

Local manufacturing versus reliance on imports (high costs but potential for growth of local industry)

 New hydropower projects offer the opportunity to integrate modern hydromechanical technologies from the design stage. However, these projects require rigorous initial planning, in-depth hydrological studies, and careful environmental assessment to ensure their sustainability.

In Africa, typical challenges include significant logistical constraints, limited availability of local specialized resources, and the need to import much of the technology used (Harbin Electric International, 2023).

 Brownfield Projects (Rehabilitation)

Brownfield projects aim to modernize existing hydropower facilities to extend their lifespan and improve their efficiency.

The rehabilitation of the Inga power plant in the Democratic Republic of Congo is a perfect example of this, where modernizing existing hydromechanical systems significantly increased its capacity while optimizing costs (EDF, 2023). In Africa, aging infrastructure, such as the 270 MW Sarband project in Tajikistan, is benefiting from rehabilitation.

 Key aspects include:

 • Equipment modernization: Voith Hydros' modernization of the Qairokkum power plant in Tajikistan increased capacity by 30 MW thanks to state-of-the-art turbines.

• Digitalization: EDF's digital control systems in Vogelgrün improve predictive maintenance, thereby reducing downtime.

• Cost-effectiveness: Retrofitting, as illustrated by the installation of Archimedes screws at Percheron Powers, reduces costs by more than 20% compared to new construction.

 Challenges include:

Adapting to new environmental standards: Reducing the impact on ecosystems.

Corrosion and wear due to prolonged use (EPRI, 2019)

Obsolete mechanical parts (difficulty finding replacement parts)

Equipment modernization: Replacing obsolete turbines and valves.

Upgrading control systems without disrupting operations.

Cost optimization: Less expensive than building a new site.

In Africa, rehabilitation is essential and often involves upgrading to more efficient turbines (GE Renewable, 2022) and replacing manual valves with automated systems. This is particularly true for plants such as those built in the 1960s, which now require upgrades to meet modern energy efficiency standards.

 Comparing the Challenges

Greenfield projects foster technological innovation from the design stage but involve significant investments and extended construction times. Conversely, brownfield projects offer economic benefits and rapid deployment, but pose technical constraints related to the integration of new technologies with existing systems.

 Challenges include:

• Technical challenges: Greenfield projects require site-specific designs to manage hydrological variations, while brownfield projects must integrate new systems with aging infrastructure. For example, Harbin Electrics' work on the GERD adapts to complex geological conditions, while the Qairokkums rehabilitation addresses compatibility issues. 

• Economic considerations: Greenfield projects, such as Karuma ($1.7 billion), have higher initial costs but lower long-term maintenance. Brownfield projects, such as Sarband, are profitable but face financing constraints for upgrades. 

• Environmental and social impacts: Greenfield projects risk disrupting habitats, as evidenced by concerns about the GERD reservoirs, while brownfield projects focus on reducing downtime and ecological impact during upgrades. The Electric Power Research Institute (EPRI) emphasizes that digitalization and fish-friendly technologies are essential for both types of projects to achieve Africa's sustainability goals.

Comparison of Key Issues

 Selection and Installation Strategies

Effective selection and installation of hydromechanical systems in African projects requires tailored strategies:

• Site-specific assessment: Hydrological and geotechnical studies ensure equipment suitability. For example, GE turbines for Karuma were selected based on detailed flow analyses.

 • Technology partnerships: Collaborations with global leaders such as Voith, ANDRITZ, and GE ensure access to state-of-the-art and reliable equipment. The XFLEX HYDRO project, involving EDF and ANDRITZ, demonstrates this with the development of Vogelgrün's digital twin.

 • Sustainability priority: Fish-friendly turbines and low-head systems, such as those used in the Mbei project in Gabon, comply with environmental regulations. 

• Hybrid solutions: Partial retrofits where complete replacement is not practical. 

• Local capacity building: Training programs, such as those implemented in the Nachtigal project by the Petrocertif Construction Academy. 

• Lifecycle cost analysis: Compare the long-term benefits of new and refurbished systems. 

Installation and maintenance

Greenfield projects: Phased construction with performance testing.

Brownfield projects: Phased replacement of equipment to minimize disruptions. 

In Africa, an effective strategy integrates partnerships with specialized international suppliers (Andritz Hydro, Voith, GE Renewable Energy) while strengthening local technical capacity, thus ensuring operational sustainability and better future maintenance management (Andritz Hydro, 2023; GE Renewable Energy, 2023).

Conclusion

Africa possesses considerable hydropower potential, and the optimization of hydromechanical systems is essential for changing the energy setpoint to maximize hydropower-based renewable energy production. The effective implementation of hydromechanical systems in African hydropower projects requires a tailored approach depending on the nature of the project. Greenfield projects enable advanced technology integration from the design stage, while brownfield projects promote rapid economic optimization of existing facilities.

A balanced strategy combining technological innovation and local capacity building ensures not only immediate success but also the long-term sustainability of African hydropower infrastructure.

 Strategic selection, leveraging partnerships with companies such as ANDRITZ, GE, Voith, Harbin Electric, and EDF, as well as careful attention to sustainability and local capacity, guarantees successful implementation. By taking into account Africa's unique hydrological and economic contexts, these systems can unlock the continent's vast hydropower potential, contributing to a sustainable energy future.