Phase-change-storage dual-heat-source thermoelectric system for photovoltaic-diesel waste-heat complementation

Photovoltaic (PV) modules suffer from efficiency losses of 0.4–0.5% per °C temperature rise, while diesel engines discharge approximately 30% of fuel energy as exhaust waste heat, both issues remaining largely unaddressed in standalone systems. This study designed a dual-heat-source thermoelectric generation (TEG) system that integrates lauric acid-expanded graphite composite phase change material (PCM) and flat heat pipes to enable cascaded thermal utilization and bidirectional heat transfer between PV modules and diesel exhaust. A three-layer thermoelectric module (TEM) array was adopted, with the first and second layers driven by diesel exhaust heat and the third layer utilizing recovered PV waste heat. Numerical simulations and experiments were conducted to evaluate thermal performance, PV cooling effectiveness, and thermoelectric output under single- and dual-source modes. Results show that the system reduces PV operating temperature by 26.4% under 1000 W/m 2 irradiance, increasing PV output power by 9.4%. Dual-source operation improves maximum TEM output by 7.85% over diesel-only mode, reaching 3.57 W. At an extreme ambient temperature of 233 K, the system actively maintains PV backsheet temperature at 313 K via reverse heat transfer. The PCM enables continuous power delivery for 15 h under no-sunlight conditions. Thermoelectric conversion efficiencies reach 0.71% for diesel exhaust, 0.42% over a full 22-h cycle for PV waste heat, and 0.68% under dual-source mode. Unlike previous studies that focus on single heat sources or independent cooling, this work uniquely achieves bidirectional thermal regulation, cooling PV under high irradiance while insulating it under extreme cold, and cross-period energy supply, offering a practical thermoelectric solution for off-grid hybrid PV-diesel systems.