A review of powering unmanned aerial vehicles by clean and renewable energy technologies

This paper comprehensively reviews renewable power systems for unmanned aerial vehicles (UAVs), including batteries, fuel cells, solar photovoltaic cells, and hybrid configurations, from historical perspectives to recent advances. The study evaluates these systems regarding energy density, power output, endurance, and integration challenges. A detailed comparison highlights that lithium-ion batteries dominate the market due to their high power density but are limited by low energy density, restricting flight endurance to less than 90 min for small UAVs. Fuel cells, particularly proton exchange membranes, demonstrate high energy density, enabling long flight durations for lightweight UAVs, yet face challenges such as slow response and hydrogen storage limitations. Solar-powered UAVs, while achieving multi-day endurance in optimal sunlight, require extensive wingspans and are constrained by weather and location. Hybrid systems integrating fuel cells, batteries, and solar cells offer the most promising solutions, achieving endurance improvements of over 60% compared to single power sources, as demonstrated in recent studies. By addressing gaps in efficiency, scalability, and environmental resilience, this review identifies pathways for advancing UAV propulsion technologies. This study fills a critical gap by providing a holistic analysis of renewable energy integration in UAVs and proposing innovative approaches to optimize endurance, efficiency, and environmental impacts.