Hydropower Potential Assessment and Grid Interconnection Modelling for the North-Kivu Province, Democratic Republic of Congo (DRC)

The Democratic Republic of Congo (DRC) is recognised as the largest African country and the third in the world in terms of hydropower potential, estimated at around 100,000 MW. Approximately 44% of this potential is concentrated in the Inga River, with the remainder distributed across its 26 provinces. Despite the identification of 890 hydropower sites throughout the country, this resource remains largely unexploited, presenting a significant opportunity for renewable energy development.[1]. North Kivu, one of the 26 provinces, comprises six territories, with only a small portion of Nyiragongo territory and Goma town currently connected to the Eastern National Grid (SNEL). The electrification rate for the province is critically low, less than 5% leaving the majority of the population without reliable access to electricity, despite the province's abundant hydropower resources. Power supply in the province primarily depends on a 5 MW line originating from interconnected RUZIZI I and II plants in South Kivu, which is insufficient to meet the needs of Goma town’s approximately 2 million inhabitants. The lack of a unified national power grid and limited power generation capacity have led to widespread reliance on charcoal for cooking, diesel generators, and small-scale solar power, all of which are associated with economic and environmental challenges. Consequently, there is a compelling need to explore and develop the vast hydropower potential of North Kivu to address electricity shortages, stimulate economic growth, and reduce environmental degradation. This study aims to assess the hydropower potential in North Kivu using existing hydrological data, estimate the region’s electricity demand, and design a grid-connected system that interconnects major hydropower plants across the province. Such a system is envisaged to enhance the reliability of electricity supply, promote private sector investment, and ultimately increase electricity access from the current 3.1% to 100%. Hydropower remains the most cost-effective and reliable renewable energy source, with flexible design capabilities suitable for base and peak load demands and high-capacity factors. [2]. Understanding the quantity and location of hydropower resources is crucial for guiding development and investment strategies, as well as for informing energy system planning that minimises climate impact and fosters sustainable regional development.[3]. This paper addresses these objectives by analysing hydropower resources in North Kivu Province, evaluating their economic feasibility, and proposing a grid-connected hydropower system to enhance energy access and stability in the region. The findings aim to serve as a foundation for further research and practical implementation to harness DRC’s considerable renewable energy potential.  

LITERATURE REVIEW

The development and utilization of hydropower as a renewable energy source have been of significant interest since ancient times. Hydropower remains the most cost-effective and reliable renewable energy source, offering long lifespans ranging from 30 to 80 years and high-capacity factors that make it suitable for both base-load and peak power demands. The electricity generation in hydropower plants fundamentally depends on the height (head) and flow rate of water, which determine the size of the plant. Hydropower plants are classified primarily based on size, head, and operational scheme. Size classifications include large plants (>100 MW), medium (20-100 MW), small (1-20 MW), mini (100 kW to 1 MW), micro (5-100 kW), and pico hydropower (<5 kW)[4]. Head classifications are divided into high-head (>300 m), medium-head (30-300 m), and low-head (<30 m) developments, each employing different turbine types such as impulse turbines for high-head and reaction turbines for medium- and low-head schemes.[5]. The main components of a hydropower plant encompass civil structures (dam, intake, forebay, penstock, and tailrace), electromechanical elements (hydraulic turbines and generators), and grid connection apparatus (transformers and transmission lines)[6], [7], [8]. The selection of components, especially turbines and penstocks, depends heavily on site-specific head and flow conditions, availability, and cost considerations. Francis turbines remain the most widely used reaction turbines due to their efficiency and applicability to a wide range of heads and flows. Resource assessment is a critical initial step for hydropower projects. Estimation of power potential generally involves calculations using measured or estimated flow rates and net head, adjusted for losses and turbine efficiency. Methods for measuring river flow include basic volumetric methods, refined velocity-area methods, sophisticated flow meter grids, and weir calibration, each suitable depending on river characteristics and required accuracy.[9]. The integration of hydropower and other distributed energy resources into the power grid is increasingly important with the growth of renewable energy and deregulation of electricity markets.[10]. Grid-connected systems, also known as microgrids, enable load sharing, increased reliability, and economic operation by interconnecting distributed generators. Nevertheless, challenges include system control, planning complexity, and accommodation of variable renewable energy sources. Integration requirements emphasise synchronisation, voltage, frequency control, safety, and protection mechanisms. The cost structure of hydropower projects involves capital expenditures primarily influenced by civil works, depending on site characteristics, electro-mechanical equipment costs, operation and maintenance costs, and levelized cost of electricity (LCOE)[6], [11]. Capital costs tend to decrease per kW with increasing project size and head, while O&M costs are relatively low, averaging below 2% of installed costs annually. Economic feasibility is assessed using indicators such as payback period (PBP), internal rate of return (IRR), and benefit-cost ratio (BCR). LCOE for hydropower globally averages around $0.047/kWh, providing a competitive alternative to fossil fuel-based generation[6]. Recent research such as [12], continues to underscore hydropower’s potential for sustainable electricity generation without greenhouse gas emissions. Case studies [13],[14],[15] and [16] Emphasise the feasibility of small hydropower projects in rural and remote areas, highlighting both technical assessment and cost-effectiveness. Modern analytical tools, such as Geographic Information Systems (GIS) and Multi-Criteria Decision Making (MCDM) methods, facilitate site identification and selection.[14]. Furthermore, dynamic modelling using tools like Matlab/Simulink aids in the design and control system studies of hydropower plants, including advanced governor controls for output stability. Studies on interconnected hydropower systems reveal benefits in reducing voltage drops, improving reliability during grid disturbances, and enabling operational modes like islanding.[17]. However, managing synchronisation, reverse power flows, protection, and power quality under grid or island conditions presents both technical and economic challenges. Solutions involve power electronics, automatic synchronisation, and control strategies to maintain system stability and maximise utilisation. In conclusion, the literature presents hydropower as a mature but evolving technology with significant untapped potential, particularly in regions rich in water resources but lacking infrastructure. Integration into smart grids and the use of advanced control and modelling techniques promise enhanced efficiency, reliability, and economic viability. Ongoing research focuses on optimising design, operation, and grid interconnection strategies to fully harness this renewable resource.

METHODOLOGY

Data collection

Existing hydrological data for rivers in the North Kivu province were obtained primarily from[1], The 2014 UNDP Renewable Energy Atlas of DRC, supplemented by reports from credible organisations such as[6], [18] and [19]. These datasets included geographical locations, estimated power capacities (in megawatts, MW), and river flow parameters crucial for assessing hydropower potential.

Hydropower Potential Assessment

A comprehensive assessment of hydropower potential was conducted using hydrological parameters, particularly river flow rate (Q) and head (H). The theoretical hydropower potential was calculated using the equation:

P=η×ρ×g×Q×H

Where η is turbine efficiency (assumed 94%), ρ is water density, and g is the gravitational constant. Losses due to friction in penstocks and other conduits were accounted for by calculating net head (Hn). The demand in each region depends on how loads are being connected to the network from time to time. To predict the load, the demand factor (????????) and the diversity factor (????????????????) are often used. Each type of load possesses its ???????? and ????????????????, depending on its magnitude. The maximum demand for a given consumer can be obtained by multiplying their total connected loads and their respective ????????. In the case of the transformer, the maximum demand can be found by the summation of all maximum demands of consumers divided by the ???????????????????? between them. Electricity demand for each territory was estimated by categorizing loads into domestic, commercial, industrial, and municipal groups. Using standard appliance load profiles and demand/diversity factors, total demand was estimated by:

P=( i=14K_i ×C_i ^{) ×1.2}           

Where the subscript i represents the group of loads ( i=1

K_i =Number of units × Installed power per unit

C_i=Demand factor (DF)Diversity Factor(DivF)

The factors for the groups of loads as recommended by the International Electric Commission (IEC) are given in Table 3-1.

Table Error! No text of specified style in document.?1: Different factors for a group of loads[20]

The electricity demand for a given region requires as much granularity as possible, with a preliminary geographical scanning of the population and on-the-ground surveys, based on statistically significant sample sizes of the different demand segments[21]. Regarding the actual situation of the province with multiple repetitive civil wars, it is not easy to undertake such a task. Therefore, some estimations will be carried out based on standard loads.

Design of Grid-Connected System

Major hydropower plants with small to medium capacity (1 MW to 72 MW) were selected for grid interconnection based on proximity and technical feasibility. Detailed design considerations included:

• Civil engineering components: dams, weirs, intake structures, penstocks and surge tanks, designed to optimise head and minimise hydraulic losses.
• Mechanical components: selection of Francis turbines due to their efficiency and suitability to site-specific head and flow conditions, with appropriate governor and control systems (preferably digital PID controllers).
• Electrical components: synchronous generators were selected for their reliability in weak grid conditions, with voltage ratings adapted to site capacity; step-up transformers were designed for economical transmission voltage (~220 kV).

Economic Analysis

A pre-feasibility economic analysis was performed using RETScreen Expert software, considering capital expenditure, operation and maintenance costs, inflation, debt interest, and project life of 40 years. Key economic indicators such as payback period, internal rate of return, benefit-cost ratio, and levelized cost of electricity (LCOE) were evaluated.

Simulation and Load Flow Analysis

A dynamic model of the interconnected hydropower system was developed in Matlab/Simulink using block modules representing generators, turbines, governors, transformers, and transmission lines. Load flow analysis was conducted to evaluate power sharing, voltage stability, reactive power management, and frequency control across the interconnected grid.

RESULTS AND DISCUSSION

1. 1. Hydropower Potential and Electricity Demand in North Kivu Province

The assessment of hydropower potential across North Kivu province identified 95 hydropower sites ranging in size from Micro (13 to 88 kW), Mini (100 to 915 kW), Small (1 to 7.8 MW), to medium hydropower plants (20 to 72 MW). The total hydropower potential available is approximately 359.07 MW, with the majority located in Beni and Lubero territories. The distribution of this potential across the six territories that compose the North kivu province is given in the following table:

Table 1: Distribution of the hydropower potential across the six territories that compose the North Kivu province

Despite this potential, the actual electricity demand in the province is significantly higher, estimated at around 831.4 MW. Consequently, the hydropower potential can cover only about 43.2% of the current electricity demand. Forecasting electricity demand over the next decade, considering an 8.2% annual increase in residential loads and a 5.2% increase in industrial loads, shows a rise in total demand by 716.9 MW, reaching approximately 1,548.3 MW after ten years. This underlines the necessity of exploiting other renewable resources and implementing a reliable and cost-effective grid-connected system to meet the rising demand.

1. 2. Grid-Connected System Design and Simulation

Most micro and mini hydropower plants have small water flow rates and seasonal fluctuations, while small and medium units show less fluctuation and are thus suited for grid connection. A grid-connected hydropower system was designed by selecting 11 hydropower plants (See figure), comprising small and medium units, with known technical data, such as flow rates and heads. These units were chosen to maximise reliability and minimise power fluctuations due to seasonal changes, as these plants are located near to each other geographically, facilitating interconnection.

Figure 1: Single-line diagram of the proposed system

The simulation of the interconnected system was executed using MATLAB/Simulink, employing synchronous generator models to represent the generation units. The overall system was divided into four substations: Beni, Lubero, Masisi, and Walikale. Load flow analysis results indicated a total generated active power of 250.15 MW and reactive power of -128.14 Mvar. The system supplied approximately 244.15 MW to loads, with losses estimated at 5.99 MW (2% of total generated power) in the network. These losses highlight areas for improvement, such as reactive power compensation to enhance system efficiency.

Figure 2.: Simulink diagram of the Grid-connected system

Voltage and power analysis at generation and load buses revealed that several synchronous generators were under-excited, consuming reactive power from the utility grid. Installation of capacitor banks or adjustments to excitation voltages may be necessary to balance reactive power adequately and improve power quality. Frequency analysis demonstrated that the system frequency remained stable within acceptable limits (±0.5 Hz deviation) due to the implementation of PID controllers within governors, which maintain frequency stability despite load variations.

Figure 3: Variation of the overall frequency of the system

This confirms that the proposed grid-connected system operation aligns with standard power system frequency requirements.

1. 3. Economic Feasibility of the Grid-Connected Hydropower System

The pre-feasibility economic analysis conducted with RETScreen Expert software showed promising financial indicators.