Several summers ago, I took up jogging to break up the monotony of my current cardio exercises. I love cycling, but jogging offered something more personal: an ability to explore the outdoors leisurely, without any tool or gear beyond clothing. I quickly discovered a favorite route and began to relish the feeling of the sun on my skin and breeze through my hair. Unfortunately, as I continued my daily routine, I failed to account for the intensifying weather of the season and was left with a nasty sunburn.
It doesn’t take someone with technical knowledge to tell you that the sun is exceedingly powerful. Developments in the past half-century of material sciences have rapidly driven down solar panel technology costs. It has seen widespread adoption at both the consumer and business level as buyers look to reduce their carbon footprint or energy expenses. A solar panel, however, needs a solar panel circuit board to help guide the function of the panel installation and serve as an interface between the solar cells and the local load/grid.
Solar Cell Theory and Operation
The solar cell is at the core of a solar panel—a photovoltaic module that can directly translate light energy into direct current. Like a diode, a solar cell uses separate doped regions of the silicon for either charge carrier in an electrons-hole pair. Applying an electric field at the interface between the two doped regions (known as the p-n junction) separates the two charge carriers into their respective regions, further amplifying the strength of the field. By connecting an external conductor, current flows from anode to cathode, serving as the electromotive force that powers a circuit.
By itself, a solar cell is a passive device: it can generate current purely on its material properties. While this is a miraculous event in its own right, integrating this feature into a circuit requires some additional components for proper functionality:
- Inverter: Transforms the DC to AC. Typically, this is used to send current generated from the solar cell to the grid. However, it can also provide for local load requirements in the case of a power outage. For safety purposes, some inverters may need to shut off during a power outage to prevent a situation where someone may unknowingly work on a live circuit. Finally, inverters help target the ideal impedance according to the active current-voltage curve characteristics to maximize power transfer.
- Charge Controller: Prevents battery overvoltage and over-discharge conditions. This part not only maintains the long-term operating performance of the battery but also protects the circuit from excessive charge or heat that could damage the components or board.
- Battery: Allows accumulated energy storage over the day, which can be used for local load requirements or sent back to the grid on buyback programs. The latter option in bulk also provides adaptive stability to the grid during periods of high demand.
Additionally, some solar panel installations may include a solar tracking system for real-time adjustments to the sunlight’s angle of incidence throughout daylight hours. Solar tracking is more often an element of commercial systems than residential ones, as the equipment necessary for tracking amounts to an increased cost at both times of purchase and over the maintenance life span. Further refinements include double-sided panels that utilize highly reflective white surfaces underneath the panel side facing away from the sun to enhance albedo, increasing total energy efficiency per unit and area.
Solar Panel Circuit Board Manufacturing Considerations
A PCB intended for solar panel integration must primarily focus on clean design. Additional modules may incorporate more advanced PCB topics, but the main design tenets follow common best practices. Signal integrity and power design are paramount, though designs are unlikely to encounter high-speed challenges nominally associated with signal integrity.
In aggregate, extensive voltage and current needs may arise from the linked solar panels. To accommodate these conditions, designers should widen traces and provide ample space on plane layers for enhanced current-carrying capabilities. Fabrication may also require thicker foil on the copper-clad laminate to further allay electrical concerns. The increased trace width and reduction in copper feature spacing will have an overall knock-on effect on the routing density, but this is less likely to be a major concern for solar panel PCBs than it would be for boards originating from other industries.
Proper thermal regulation will also be an important design consideration as the board will be bombarded by solar radiation during peak periods daily for extended periods. Full pour plane layers will somewhat alleviate this, but the design can incorporate thermal vias much like a power circuit design to conduct heat away from the sun-facing side. Component selection will also play a key role: alternate packages that attempt to draw away the leads from the package for a heat sink mount provide additional surface area to divert heat from the generating or localizing package. An enclosure may be useful for even greater heat sinking capabilities for more extreme climates, but this needs to be balanced against the board’s integration within the panel installation.
Your Contract Manufacturer is Ready to Meet Your Solar Design Demands
Solar panel circuit boards do not differ significantly from similar power delivery boards, but the additional complexity of environmental conditions may pose a challenge to optimizing performance. Whether it’s component selection, fabrication considerations, or circuitry design, a team of manufacturers and designers will need to consider a bevy of angles to maximize efficiency. For jobs like this, VSE is well-suited to meet your design requirements: we’re a team of engineers looking to lend our expertise to build electronics. Alongside our valued manufacturing partners, we’ll go to any length necessary to provide you with a board that exceeds all performance expectations.
