Technical Proposal for UAV Power System

1. Introduction

Based on the previously provided input conditions, we estimate the energy requirements for the UAV system as follows:

· Solar cell area: 30–36 m²

· System bus voltage: 150V

· Control voltage for steering and information loader: 2.5V, 5V, or 12V (low voltage distribution)

· Peak power output: 6–8 kW

· Average power consumption: 2–4 kW

· Flight altitude: Below 12 km

· Flight duration: Extended, though unable to achieve a 24-hour flight time

 2. Our Power System Configuration

The UAV power system consists of the following components:

· Solar array

· High energy density Lithium-ion battery

· Maximum Power Point Tracker (MPPT)

The solar array on the UAV wing can be divided into 4 to 8 or more sub-arrays, each controlled by an independent MPPT controller. The system may include 2 or 4 lithium-ion batteries, distributed either within the cabin or integrated into the wing structure. The MPPT units can manage energy distribution across different system components, ensuring optimal performance and minimizing energy loss.

 3. Configuration Details

     Key Considerations:

· Weight density

· High efficiency

· Cost-effectiveness

(1) Solar Cell and Array Solution

We use high-efficiency thin crystalline silicon solar cells, with the following specifications:

· Conversion efficiency: >20% (AM1.5, 25°C)

· Cell thickness: 15μm for flexibility to match wing surface curvature

· Cell density: <350g/m²

· Module packaging: solar cells are integrated into a hard light wing structure, which is shaped to match the UAV’s wing design.

Circuit Design:

The solar cells are connected using thin-film printed circuits, integrated into the internal structure of the UAV. The size of each solar cell is customized to fit the wing's bending shape, with typical sizes being 100mm x 100mm or 60mm x 40mm, but other sizes are available depending on requirements.

Encapsulation:

The surface of the PET thin-film solar modules is encapsulated with a layer of 25–75μm thick material to ensure durability and weather resistance. The modules are tested for temperature tolerance between -60°C to +50°C, ensuring their reliability in varying environmental conditions. The expected lifespan of these modules is at least 2 years.

(2) Lithium-ion Battery Solution

We utilize high-density lithium-ion batteries with the following specifications:

· Energy density: >220Wh/kg

· Output voltage: 88V to 134V (adjustable)

· Operating temperature range: 10°C to 30°C

· Maximum discharge rate: ≥2C

The battery configuration is tailored to support the UAV’s required flight duration and power needs.

(3) Power Management Solution

The power management system uses Maximum Power Point Tracking (MPPT) to optimize energy use. Key parameters include:

· Tracking accuracy: ≥99%

· System control efficiency: ≥94%

· Power management capacity: ≥1000W/kg

· MPPT module output: Typically 1000W, with a weight of less than 1kg

Each MPPT module is paired with a corresponding propulsion motor, allowing for direct energy transmission and minimizing energy loss.

 4. Operational Mode

The UAV's power system operates in several stages throughout the day to maximize energy efficiency:

· Morning (sunrise stage): The UAV is powered by the solar cells and battery during ascent.

· Noon (10:00 AM – 2:00 PM): Solar cell power generation is at its peak. Excess power charges the battery while also powering the UAV.

· Afternoon (decreasing sunlight): As the angle of the sun decreases, solar power output declines. The UAV then relies on both solar and battery power, and eventually switches to battery-only power during low light or at night.

This operational cycle ensures that the UAV maximizes flight time, with battery discharge occurring only when solar power is insufficient.

 5. Battery and Solar Array Performance

When the UAV is on the ground and the battery is fully charged, the solar array can generate surplus power. The power supply controller ensures that the system remains stable, even if the array deviates from the optimal power point. This has no impact on the UAV’s system performance.

 6. Manufacturing and Development

Given the wing surface design and materials, it is feasible to manufacture the solar modules and circuits in China and deliver them in product form. However, the UAV power system requires extensive analysis and testing, particularly with regard to the battery and power control systems. The development of the power system package will focus on ensuring ease of debugging and meeting operational requirements.

Our team has extensive experience in the development of solar-powered UAV systems, particularly for low-altitude operations. We have already completed several related research projects and developed similar aircraft. We look forward to a successful collaboration on this project.

 Conclusion

We believe this power system solution will meet the UAV’s energy requirements, providing optimal performance, efficiency, and flight duration. We are confident in our ability to develop and integrate this system successfully and are eager to proceed with the next steps in the project.

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