Driving Sustainable Energy Dispatch for Remote Communities Using Levy Flight Salp Swarm Algorithm
Benjamin O. Ajayi, Anthony Ibe, Boniface A. Oriji, Toyin O. Odutola
Emerald Energy Institute, University of Port Harcourt, Nigeria
DOI: https://doi.org/10.51244/IJRSI.2024.1108096
Received: 08 August 2024; Accepted: 13 August 2024; Published: 15 September 2024
This study evaluates three energy dispatch algorithms to find the best way to improve hybrid energy systems in rural areas: load following (LF), cycle charging (CC), and a novel customized strategy (CS). The study examined solar and wind resources as well as projected patterns of energy consumption with a particular focus on Bambur village in Taraba State, Nigeria. The Levy Flight Salp Swarm Algorithm (LFSSA) was used in the study to assess system configurations for each method, accounting for battery storage, wind turbines, diesel generators, and photovoltaic (PV) arrays. The most cost-effective and efficient approach was determined to be the Customized Strategy (CS), which produced the lowest Net Present Cost (NPC) of $ 1,959,100 and Levelized Cost of Energy (LCOE) of $ 0.119/kWh. The Load Following (LF) technique had the highest costs at $ 2,204,736.10 and $ 0.134/kWh, while the Cycle Charging (CC) method had intermediate costs with an NPC of $ 2,083,770 and an LCOE of $ 0.127/kWh. With a 580-kWh battery bank, a 10 kW wind turbine, 332 kW of PV capacity, and a 78 kW diesel generator, the CS approach showed better component sizing balance. The trade-offs between energy output, storage, and backup power in real-time were optimized using this design. Sensitivity analysis revealed that increasing interest rates from 10% to 18% led to a rise in LCOE, while diesel cost fluctuations showed a non-monotonic impact on LCOE, peaking at $ 0.79/L before declining due to increased reliance on renewable sources and storage. CS strategy’s balance of investment and efficiency makes it ideal for remote energy management, offering key insights for rural electrification.
Keywords: Hybrid Energy System (HES), Dispatch Strategies, Levelized Cost of Energy (LCOE), Net Present Cost (NPC), Levy Flight Salp Swarm Algorithm (LFSSA)
Nigeria’s rich cultural diversity and natural resources are overshadowed by challenges like rural electricity shortages and the need for sustainable development. These issues, critical to national development, impede daily life and economic growth. Many rural areas lack reliable electricity, affecting education, healthcare, and industries, thereby perpetuating poverty and underdevelopment [1].
The critical need for power generation based on renewable energy (RE) to meet future energy issues is highlighted by the world’s rapidly diminishing fossil fuel sources. The use of fossil fuels increases emissions significantly, underscoring the need of using renewable energy sources like wind and solar power. Hybrid energy systems (HES) have made it feasible and efficient to integrate these dispersed renewable energy sources [2].
Stand-alone HES can be a useful option for decentralized power generation and distribution in remote locations, especially when combined with diesel backup. Renewable energy sources like wind and solar power are especially useful in this regard. By utilizing the plentiful and sustainable energy derived from natural sources, these systems lessen dependency on fossil fuels and encourage environmental sustainability [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. Rural areas face challenges such as poor road access, isolated locations, and high supply costs, making grid extension impractical. Diesel generators are often used but come with high costs, maintenance needs, and pollution [11]. Nigeria’s ample renewable resources—solar and wind—offer an alternative. Studies advocate for solar PV, wind, and hybrid systems to provide sustainable and efficient power [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. Successful dispatch strategies are essential for optimizing these systems, reducing costs, and enhancing reliability [12], [13], [14].
Energy control strategies in hybrid energy systems optimize resource utilization, reduce costs, and enhance reliability. They improve efficiency, extend component lifespans, and promote environmental sustainability. These strategies drive technological advancements, making renewable energy more viable and encouraging wider adoption of hybrid systems. Cycle Charging (CC) maximizes battery use by charging during low demand or high renewable generation and discharging during peaks, increasing renewable energy use and efficiency. Load Following (LF) dynamically adjusts power generation to demand changes, optimizing renewables and grid stability.
Several studies have compared different dispatch strategies, some with grid connections and others with standalone grids. These studies examined existing strategies like LF and CC, along with other dispatch strategies [2], [4], [5], [6], [7], [8], [9], [10], [15], [16], [17], [18]
Most papers focused on performance parameters such as NPC and COE [2], [4], [5], [6], [7], [8], [9], [10], [15], [16], [17], [18], while some included CO2 emissions as a performance parameter [2], [7], [9], [15], [17], [19]
This study introduces a Customized Strategy (CS) that combines the benefits of LF and CC by optimizing battery charging and discharging based on projected load demands and anticipated renewable energy generation. A planned PV/Wind/Diesel/Battery HES designed to electrify the off-grid rural area of Bambur, Taraba State, Northern Nigeria, is analyzed, which was developed in MATLAB. The approach uses the Levy Flight Salp Swarm Algorithm (LFSSA) to determine which of the three dispatch strategies—LF, CC, and CS—is the best. This algorithm’s main goal is to maximize the share of renewable energy while lowering the Levelized Cost of Energy (LCOE) and Net Present Cost (NPC).
This section presents the methodological framework for developing and optimizing the HES, starting with mathematical models of energy sources. This is followed by the description of the study area.
Energy Source Modeling
Mathematical modeling is vital for designing, optimizing, and assessing hybrid energy systems. It helps predict power flow, determine optimal component sizes, and integrate solar, wind, and storage technologies, ensuring efficient, reliable, and economically viable systems. This approach advances sustainable energy by enhancing system performance and grid integration.
Equation 1: PV Array Model
$$ P_{PV} = Y_{PV} \cdot f_{PV} \cdot \frac{G_T}{G_{TST}} \left(1 + \alpha_P \cdot (T_C – T_{CST})\right) $$
Where:
Equation 2: Wind Turbine Power Production
$$ P_{WDT}(t) =
\begin{cases}
0 & \text{if } v_{hub} < v_{cut-in} \text{ or } v_{hub} \geq v_{cut-out} \\
P_{WDT-r} \left(\frac{v_{hub}^3 – v_{cut-in}^3}{v_R^3 – v_{cut-in}^3}\right) & \text{if } v_{cut-in} \leq v_{hub} < v_R \\
P_{WDT-r} & \text{if } v_R \leq v_{hub}(t) < v_{cut-out}
\end{cases}
$$
Equation 3: Wind Profile Power Law
$$ V_{hub}(t) = V_{ref}(t) \left(\frac{h_{hub}}{h_{ref}}\right)^{\alpha} $$
Equation 4: Battery Storage System Model
$$ E_{BSS}(t) = E_{BSS}(t-1)(1 – \sigma) + E_{excess} \eta_{BSS} $$
$$ E_{BSS}(t) = E_{BSS}(t-1)(1 – \sigma) – E_{deficit} $$
Equation 5: State of Charge (SOC)
$$ SOC(t) = SOC(t-1) + \frac{\sum_{i=1}^{N} P_i(t) – P_{load}(t)}{V_{BSS} C_{BSS}} $$
Equation 6: Diesel Generator Fuel Consumption
$$ C_{f-DG} = \alpha_{DG} \cdot P_{DG}(t) + \beta_{DG} \cdot P_{rated-DG} $$
Equation 7: Rectifier Model
$$ P_{Rect-o}(t) = P_{Rect-i}(t) \cdot \eta_{Rect} $$
Equation 8: Inverter Model
$$ P_{Invt-o}(t) = P_{Invt-i}(t) \cdot \eta_{Invt} $$
Equation 9: Levelized Cost of Energy (LCOE)
$$ LCOE = \frac{C_{INT} + C_{OM} + C_{REP} – S_{SAL} \cdot CRF}{E_{gen}(t)} $$
Equation 10: Capital Recovery Factor (CRF)
$$ CRF = \frac{r(1 + r)^n}{(1 + r)^n – 1} $$
Equation 11: Annualized Capital Cost
$$ C_{INT} = \sum_{j=1}^{N} C_{INT_j} $$
Equation 12: Operations and Maintenance Cost
$$ C_{OM} = \sum_{j=1}^{N} C_{OM_j} $$
Equation 13: Replacement Cost
$$ C_{REP} = \sum_{j=1}^{N} C_{REP_j} (1 + r)^{t_i} $$
Equation 14: Salvage Value
$$ C_{SAL} = \sum_{j=1}^{N} C_{INT_j} \times \left(1 – \frac{t_{sys}}{L_i}\right) $$
Cost and Lifespan Notations
\( C_{INTj} \) is the initial cost of component \( j \).
\( t_{sys} \) is the entire operational lifetime of the system.
\( L_i \) is the expected lifespan of component \( j \).
Modelling of HES
This research introduces a novel energy dispatch strategy named the Customized Strategy (CS) for optimizing power dispatch in hybrid energy systems. The CS prioritizes renewable energy sources by leveraging the strengths and mitigating the weaknesses of two existing strategies: LF and CC.
The study uses LFSSA to optimize the system setup using the MATLAB simulation tool. Comparison is made between the results of different energy dispatch systems, such as LF, CC, and Customized Strategy (CS). In order to minimize the system’s COE and NPC while maintaining adherence to predetermined operational limits, the ideal number of photovoltaic (PV) modules, wind turbines, battery banks, and diesel generator capacity must be determined.
Customized Strategy (CS) offers superior performance over cycle charging (CC) and load following (LF) by dynamically adapting to changing conditions. It uses intelligent prediction and state of charge (SOC) feedback to optimize fuel economy and battery sustainability. Unlike static CC, which lacks adaptability, and LF, which doesn’t optimize for efficiency, CS handles the complexities of hybrid energy systems more effectively by balancing load demands and renewable variability.
Hybrid Energy System Components
The analysis assumes a system lifetime of 20 years, and the system components (PV modules, wind turbines, diesel generator, and battery storage) are defined in Table 3.1.
Table I – The System Components
Optimization Techniques
The Flight Levy Salp Swarm Algorithm (FLSSA) a novel optimization technique that combines the concepts of Lévy flight and the Salp Swarm Algorithm (SSA) is employed for the studies.
SSA is a cutting-edge optimization method modeled after nature that mimics the swarming behavior of salps in the ocean. The key aspects of the SSA are:
The goal of the SSA is to replicate the coordinated and cooperative movement of actual salp swarms in the water in order to effectively search the search space and converge to the global optimum. When compared to other metaheuristic approaches, the algorithm’s performance on a variety of optimization problems has shown promise.
Key Equations
Equation (15):
\[
X_p = x_{11}x_{12}…x_{1n}x_{21}x_{22}…x_{2n}…x_{d1}x_{d2}…x_{dn}
\]
Equation (16):
\[
x_{i1} =
\begin{cases}
z_1 + a_1(ub_p – lb_p) a_2 + lb_p & \text{if } a_3 \geq 0 \\
z_1 + a_1(ub_p – lb_p) a_2 + lb_p & \text{if } a_3 < 0
\end{cases}
\]
Equation (17):
\[
a_1 = 2 e^{-4\frac{l}{L}}
\]
Equation (18):
\[
x_{pj} = \frac{1}{2} \lambda t^2 + \delta_o t
\]
Equation (19):
\[
x_{pj} = \frac{1}{2}(x_{pj} + x_{pj-1})
\]
Equation (20):
\[
x_{pj} =
\begin{cases}
l_j & \text{if } x_{ij} \leq l_j \\
u_j & \text{if } x_{ij} \leq u_j \\
x_{pj} & \text{otherwise}
\end{cases}
\]
Levy Flight Equation (21):
\[
L_s \sim \frac{1}{s^{1+\beta}}
\]
where \( 1 < \beta \leq 3 \).
Equation (22):
\[
x_{ij} = x_{ij} + \alpha L(s)
\]
The FLSSA leverages the Levy flight strategy along with the swarming characteristic of salps to enhance both exploration and exploitation in the search space. The algorithm divides the salp population into leaders and followers, with the leader leading the swarm and the followers trailing behind. The leader’s position is updated using an algorithm that accounts for the location of the food source, search space limitations, and random factors. The followers’ positions are updated using Newton’s law of motion. The Levy flight strategy introduces long jumps that help the algorithm escape local optima. This approach balances exploration and exploitation, making it suitable for various optimization problems in engineering design, machine learning, and resource allocation.
The outcomes of the estimated energy demand and renewable energy data for the study area are displayed in charts, followed by the use of LFSSA to compare various energy dispatch methods, such as Customized Strategy (CS), Cycle Charging (CC), and Load Following (LF).
Study Area and Population of the Study
The study examines the potential for renewable energy solutions in Bambur, a village situated in Taraba State, Nigeria. Bambur lies at approximately 9° 20′ 59″ North latitude and 11° 2′ 41″ East longitude. A part of Central Bambur is the area under study, encompasses roughly 200 residences, a primary healthcare center, a public primary school, and a bustling commercial hub.
Figure 1 – Location of the study area (Bambur)
The population is estimated at around 1,000, comprising regular dwellers and others who conduct business at the hub. The majority of the residents are engaged in agricultural activities. Similar to many villages in the region, Bambur currently lacks access to the national electricity grid.
The wind and sun irradiation data utilized in this study was obtained by the National Aeronautics and Space Administration (NASA). The estimated energy demand for Bambur were determined through a combined approach of data collection via questionnaires and subsequent validation by comparing the obtained data with the average energy demand of a typical village in Northern Nigeria. This multi-pronged approach ensured the accuracy and representativeness of the energy demand estimations for the village.
The average yearly solar radiation and wind speed, as determined by the study’s analysis of 8760 hours of village data, are 5.61 kWh/m2/day and 5.12 m/s, respectively. The daily load demand curve for Bambur Village is shown in Figure 3.2. The average daily electrical load demand is 482 kWh, with an anticipated peak daily load demand of 26.75 kW. Energy use peaks twice daily: mornings (5-8 AM) and evenings (7-10 PM), likely due to typical daily routines. To enable a comparative study of the patterns of energy consumption, the load demand is shown for the wet season and the dry season. The dry season experiences significantly higher demand, primarily driven by cooling needs and extended business hours compared to the wet season.
Figure 2 – Daily load demand in Bambur Village
Monthly wind speed in Bambur Village
Figure 3 highlights the wind speed data for Bambur, crucial for evaluating wind energy potential. Wind speeds peak at around 7 m/s in January and 6.5 m/s in December, indicating favorable conditions for wind energy generation. However, speeds drop to around 4 m/s in June and July, necessitating energy storage or additional sources to maintain a reliable energy supply.
Figure 3 – Wind Speed in Bambur
Monthly solar radiation in Bambur Village
Figure 4 presents monthly solar radiation data for Bambur, crucial for assessing solar photovoltaic (PV) system performance. January and December show high solar radiation at around 5.7 kWh/m², and from February to April, levels remain consistently high at 5.9-6.5 kWh/m². May and June see a slight dip to about 5 kWh/m², while July and August exhibit the lowest levels at 4-4.5 kWh/m². Radiation increases again from September, peaking at 6.2 kWh/m² in November.
Figure 4 – Solar Radiation in Bambur
Hybrid Energy System
This analysis compares three strategies for a HES: LF, CC and CS. The components evaluated are Photovoltaic (PV) systems, Wind Turbines (WT), Battery Storage Systems (BSS), and Diesel Generators (DG) in Figure 5.
Figure 5 – Hybrid Energy System Components (PV, WT, DG & BSS)
1) Photovoltaic (PV) System: The Load Following strategy prioritizes real-time energy with 353 kW PV capacity. Cycle Charging, at 319 kW, relies more on storage and diesel. The Customized Strategy, with 332 kW, balances energy production and storage, aiming for cost efficiency and reliability.
2) Wind Turbine (WT): The consistent 10 kW wind turbine capacity across strategies suggests limited or consistent wind resources, making larger turbines unnecessary. Wind power plays a minor role compared to PV systems, and its integration isn’t influenced by operational strategy choice.
3) Battery Storage System (BSS)
Energy dispatch strategies vary in battery capacities. Cycle Charging uses the largest at 679 kWh for maximum renewable utilization and minimal diesel use. Load Following, with 495 kWh, focuses on real-time generation. The Customized Strategy balances at 580 kWh, optimizing storage and costs.
4) Diesel Generator (DG): Generator size choices reveal distinct strategies: Load Following and Customized Strategy use a larger 78 kW generator for robust backup and grid stability during peaks. Cycle Charging, with a smaller 63 kW generator and larger battery, emphasizes stored renewable energy, reducing fossil fuel use and emissions.
5) Overall System Analysis: LF prioritizes immediate demand with the largest PV capacity and generator but smallest battery, leading to higher diesel use during low solar output. CC emphasizes storage with the largest battery but smallest PV and generator, minimizing diesel consumption. CS balances components, optimizing cost, reliability, and renewable use. All strategies reflect solar-driven systems with minor wind roles, highlighting location’s solar potential and limited wind. Battery size variations emphasize storage’s importance, and generator roles vary, demonstrating system flexibility for different operational goals.
HES with Relevant Parameters
This analysis examines the relevant parameters for the three strategies in a HES: LF, CC, and Customized Strategy (CS).
Figure 6 – Initial Capital Cost
Initial Capital Cost
The Customized Strategy (CS) has the lowest initial capital cost at $711,936.94, followed by Cycle Charging (CC) at $720,755.21 and Load Following (LF) at $821,043.72 as in Figure 6, CS system would require the least amount of upfront investment compared to the other two options.
Figure 7 – Operating Costs
Operating Costs
Fig. 7 indicates the operating costs with Load Following (LF) has the highest at $179,588.98, followed by Cycle Charging (CC) at $173,903.11, while the Customized Strategy (CS) has the lowest at $141,340.45. Thus, CS is the most cost-effective option for operating expenses.
Figure 8 – LCOE and NPC – Dispatch Strategies (LF, CC & CS)
Net Present Cost (NPC):
Load Following (LF) has the highest NPC at $2,204,736.10 due to larger PV and diesel investments and higher operational costs. Cycle Charging (CC) has a moderate NPC of $2,083,770.00 (Fig. 8), balancing initial investments with efficient storage use. Customized Strategy (CS) has the lowest NPC at $1,959,100.00, optimizing costs and efficiency. These values indicate CS offers the best long-term economic performance, followed by CC, with LF incurring the highest costs.
Levelized Cost of Energy (LCOE):
Load Following (LF) has the highest LCOE at $0.134/kWh, indicating low cost-efficiency. Cycle Charging (CC) improves with $0.127/kWh, using energy storage efficiently. Customized Strategy (CS) achieves the lowest LCOE at $0.119/kWh, balancing renewables, storage, and backup. CS offers the most cost-effective energy production, followed by CC, with LF being the least economical.
CO2 Emission
Figure 9 illustrates the carbon dioxide (CO2) emissions associated with three distinct algorithms: LF, CC, and CS, measured in kilograms per year. Among these, the CC algorithm exhibits the highest level of CO2 emissions, approximately 32,452 kg/year. Following closely, the LF algorithm generates emissions of 25,138 kg/year, while the CS algorithm records the lowest emissions, slightly below 24,897 kg/year.
Figure 9 – CO2 Emission
Overall System Analysis:
The Customized Strategy (CS) emerges as the most cost-effective option, featuring the lowest Net Present Cost (NPC) and Levelized Cost of Energy (LCOE), as well as the least CO2 emissions. Cycle Charging (CC) offers a lower-cost option compared to LF; however, it results in the highest CO2 emissions.
Sensitivity Test
The sensitivity analysis examines how variations in fuel prices and interest rates influence the LCOE and NPC.
Figure 10 – Sensitivity with Interest Rate
Figure 10 illustrate the sensitivity analysis demonstrates that increasing interest rates from 10% to 18% lead to a rise in the LCOE for HES. This non-linear relationship underscores the importance of strategic financial planning to manage elevated financing costs and ensure the sustainability of renewable energy projects.
Figure 11 – Sensitivity with Diesel Cost
The sensitivity analysis of diesel costs on the LCOE for a HES as highlighted in Figure 11 shows a non-monotonic relationship, with LCOE peaking at $0.79/L before declining. This trend is influenced by the controller’s logic, which shifts reliance to battery storage and renewable energy as diesel costs rise, highlighting the importance of smart energy management.
In summary, this study offers significant insights into optimizing HES for remote settlements by evaluating LF, CC and novel CS. Focused on Bambur village in Taraba State, Nigeria, the research highlights how different dispatch methods can influence system performance, cost efficiency, and sustainability.
The findings reveal that the Customized Strategy (CS) is the most practical and affordable choice, achieving the lowest NPC of $1,959,100 and a LCOE of $0.119/kWh, outperforming both the LF and CC. The CS strategy also showcased an optimal configuration of energy components, balancing the capacities of solar, wind, battery storage, and diesel generation to maximize energy production and reliability.
Local adaptation is necessary for HES, which prioritize RE and efficiency of the batteries. Because interest rates and diesel prices fluctuate, financial planning is essential. Performance is improved via customized dispatch, which prioritizes balanced energy integration over capacity maximization.
This study advances knowledge of sustainable energy options for remote populations by showing that enhanced HES can provide dependable, reasonably priced electricity to places without grid connectivity. The promising results of the Customized Strategy pave the way for future research into adaptive energy management systems, potentially leveraging machine learning for real-time decision-making.
As global efforts to address rural electrification and transition to sustainable energy continue, this study serves as a valuable resource for policymakers, engineers, and communities aiming to implement effective energy solutions. The findings not only provide a framework for enhancing energy access in Nigeria but also offer adaptable strategies for similar challenges faced worldwide.