How Do I Integrate Solar Into A UAV?
Integrating solar will provide additional power to a UAV that can be used to extend range or carry additional payload. Integration can be as easy or complex as you want it to be, depending on the time and materials you have available. Alta Devices solar cells can be integrated into curved and irregularly shaped surfaces in a variety of methods. Two of the most common methods are vacuum forming and simple adhesive. We will also cover the role of an MPPT and how it can be integrated into a UAV.
Figure 1: Alta solar cells integrated into the Hanergy UAV
Vacuum Forming Method
This can be done with wing materials such as fiberglass, carbon fiber, or Kevlar. Firstly, the solar cells are placed face down into a wing shaped mold, and thin sheets of wing skin material are placed on top of the solar. Alta can provide encapsulated or un-encapsulated solar arrays depending on application needs. The stack is now able to endure heated vacuum processing to set the material with the solar forming the top layer of the wing.
Alta Devices offers a front-side-only lamination of the solar cells to provide the most lightweight solution possible. The back of the solar cells should be electrically isolated to ensure that the exposed leads are isolated from the wing material. Alta can do this for you in the form of a back-side laminate, or you can use your own material (such as Kapton tape). The solar cells become the top layer of the wing, providing a seamless integration that will provide minimal change to aerodynamics.
Figure 2: Alta solar cells integrated into a carbon fiber wing using a vacuum mold process
This is an easier, quicker, and cheaper method for integration. The adhesive attaches the solar directly to the UAV wing. This can be done using a double-sided industrial tape or spray-on adhesive, found at many hardware stores.
This process is suitable for small UAVs that don’t use a vacuum mold process, which includes UAVs with foam or Styrofoam wings. If using a foam wing, it is important to check that the adhesive will not eat away and degrade the foam. Since heat can easily melt foam wings, it is highly recommended to complete any soldering required before attaching. During the application process, it is important to be extremely careful when aligning the solar arrays. If the solar is misaligned, trying to un-adhere could result in damage due to sharp bending.
A small caveat to using this method is that the laminar air flow can be slightly disturbed due to the join where the solar is attached. The magnitude can vary depending on the size and area of the wing as well as where the module is placed.
Figure 3: Alta solar cells adhered to a foam wing using an adhesive
Power Management (MPPT)
As a leading supplier of solar for UAVs, we often get the question, ‘where should I locate the MPPT?’ Determining where the maximum power point tracker charger controller can be stored is an important step in the UAV solar integration process. A maximum power point tracker charger controller, or MPPT, is an electronic DC to DC converter that optimizes the match between a solar array (PV panels) and a battery bank. MPPTs are essential to convert a fluctuating, DC output from solar panels into a regulated voltage to charge batteries.
The MPPT can sometimes fit in the fuselage. Removing covers and extra packaging can reduce the size and weight of the controller, reducing its impact. In terms of early UAV prototypes, MPPTs can be simply adhered to the top of the fuselage, left exposed.
MPPT charge controllers are an important component of battery-based solar energy systems. They reduce wasted energy by operating the solar module at its maximum powervoltage, maximum power current (instead of the non-optimized power by voltage mismatch obtained by connecting the solar directly across the battery terminals). MPPT controllers allow integrators to use solar modules of any configuration or voltage, allowing them to optimize usable solar area instead of trying to match the voltages between solar and batteries.
Figure 4: MPPT Charge Controller
Please contact us for integration support at: firstname.lastname@example.org
Learn more about Increasing UAV Endurance: https://www.altadevices.com/unmanned-systems/
Figures 1,2,3: Property of Alta Devices
 Alta Devices recommends a maximum process temperature of 140 degrees Celsius and a maximum pressure of 1 atm.