Changsha Kototerk Tech Co, Ltd Rainer.Chen
Keywords: Solar streetlights; Photovoltaic degradation; Lithium battery life; Extreme environment; Energy balance; Middle East and Africa
In the Middle East and Africa along the "Belt and Road" initiative, off-grid solar lighting systems are a core component of infrastructure construction. However, in many projects, the luminous flux decreases by 30%-60% compared to the initial design value after 2-3 years of operation, directly leading to the failure of road lighting safety standards. This premature performance inflection point not only increases subsequent maintenance costs but also exposes the vulnerability of traditional engineering design in coping with extreme climates. To address this problem, Kototerk Company, based on its years of practical construction and operation experience, offers the following points for discussion with peers.
1.1 Photovoltaic Module Degradation
In tropical arid climates, the annual degradation rate of photovoltaic modules far exceeds the laboratory expectations set by the International Electrotechnical Commission (IEC) standards.
Temperature coefficient influence: The power temperature coefficient of monocrystalline silicon modules is typically -0.35% to -0.45%/°C. In the summer of the Middle East, the back panel temperature of the modules often exceeds 75°C, resulting in a real-time power drop of nearly 20% [1].
Potential-induced degradation (PID): High temperatures accelerate ion migration in the encapsulation material, leading to increased leakage current. Physical Shading Losses: The high-dust environment in Africa (Soiling Effect) can lead to a 15%-30% reduction in the light transmittance of the module surface. Without regular cleaning, this loss will translate into hot spot effects within the module, causing irreversible physical damage [2].
1.2 Electrochemical Evolution of Energy Storage Systems
Battery failure is a direct cause of brightness degradation.
Application of the Arrhenius Law: The electrochemical reaction rate is exponentially related to temperature. In a 45°C environment, the SEI film thickening rate of lithium iron phosphate (LFP) batteries is 2.5 times that at 25°C, directly leading to a rapid collapse of available capacity [3].
Deep Discharge under Energy Deficit: When the system enters an "energy deficit" state due to insufficient power generation from the modules, the battery operates at a low state of charge (SoC) for extended periods, causing the depth of discharge (DoD) to frequently trigger the threshold, accelerating the structural collapse of the cathode material.
1.3 Logical Audit Defects in System Design
Most failed projects have a "static design" misconception in the planning stage, using the annual average sunshine hours for calculations while ignoring the dynamic balance during extreme months (such as dust seasons and continuous rainy seasons). Once the system cannot be recharged in time under adverse weather conditions, it will enter a vicious cycle that cannot be self-corrected.
2.1 Dynamic Capacity Redundancy
Institutional views suggest that the "just enough" design logic should be abandoned in extreme environments.
Over-provisioning Coefficient: For the Middle East region, the photovoltaic installed power should be configured at 1.3-1.5 times the load demand power to offset the losses caused by high temperatures and dust shading.
Shallow Cycling Strategy: By increasing the battery capacity (3-5 days of redundancy), the daily depth of discharge is limited to within 50%, using physical redundancy to counteract chemical degradation in high-temperature environments.
2.2 Intelligent Energy Management (EMS)
Introduce controllers with MPPT function and temperature compensation strategies. When the battery SoC (State of Charge) is detected to be below a preset value, the system should automatically switch to "intelligent dimming mode," reducing brightness during non-peak hours to ensure a smooth transition of battery power and prevent deep discharge.
2.3 Thermal Insulation and Ventilation Design
Existing lithium iron phosphate battery technology abandons traditional passive thermal insulation methods such as burying the battery box and adding aluminum foil reflective layers. Instead, it adopts an integrated design of the battery module and the back of the photovoltaic panel, utilizing the heat dissipation area of the photovoltaic panel and air convection channels. Combined with the wide operating temperature range of lithium iron phosphate batteries (-20℃~60℃), this achieves natural heat dissipation of the battery compartment. Simultaneously, the module sealing process (IP67 protection) isolates external dust and moisture, simplifying civil engineering construction processes and achieving active thermal management through structural optimization, ensuring temperature control and extended lifespan of the battery in extreme outdoor environments.
The 2-3 year performance degradation of solar streetlights is not an industry inevitability, but rather a design flaw caused by low-cost competition. Changsha Kototerk Technology Co., Ltd. (www.kototerk.com) has proven in numerous overseas projects that by focusing on "system matching" rather than "single-point component stacking," and taking responsibility for the final delivery results (continuous lighting rate), the system can achieve stable operation for more than 8 years.
Project owners should shift their focus from "initial purchase price" to "levelized cost of electricity (LCOE)" and "total life cycle return on investment."
References
[1]Jordan,D.C.,&Kurtz,S.R.(2023).Photovoltaic Degradation Rates—An Analytical Review.Progress in Photovoltaics:Research and Applications.
[2]Maghami,M.R.,et al.(2024).The impact of dust on solar PV performance:A review over Middle East and African environments.Renewable and Sustainable Energy Reviews.
[3]Wang,J.,et al.(2023).Degradation Mechanisms of LiFePO4 Batteries in High-Temperature Tropical Climates.Journal of Power Sources.
[4]Abderrezek,M.,&Fathi,M.(2024).Optimization of Off-grid Solar Lighting Systems in Desert Regions.Energy Procedia.
[5]Sharma,A.,et al.(2023).Long-term performance assessment of solar lighting systems in rural Africa.International Conference on Advances in Energy Research.
Post time:Jan - 01 - 1970
