Supercapacitor-Based Voltage Smoothing in a Solar PV Microgrid: An OpenModelica Simulation Study

In the quiet corners of the world where the electrical grid does not reach, solar panels are often the only source of power. They offer a clean, silent way to light homes and run small appliances, but they come with a fundamental limitation: the sun does not shine steadily. When a cloud passes overhead, the light hitting the panels dims and brightens in a matter of seconds. This rapid shifting causes the electricity they produce to surge and dip unpredictably. For sensitive devices like medical equipment, telecommunications gear, or even simple LED lights, these sudden jolts in power can cause flickering, damage, or failure. To solve this, engineers often turn to energy storage, but not all storage is the same. While heavy batteries are excellent for holding energy for hours, they wear out quickly if asked to react to every tiny, fast change in sunlight. A different kind of device, known as a supercapacitor, acts more like a shock absorber for electricity. It can absorb or release energy almost instantly, smoothing out the bumps in the power supply without the rapid degradation that plagues traditional batteries.

Researchers at the Air Force Institute of Technology in Kaduna, Nigeria, set out to test how well this shock-absorbing technology could stabilize a solar power system in a simulated environment. They built a virtual model of a small, off-grid solar system using open-source software, a tool that allows scientists to write equations and watch how a system behaves over time without needing physical hardware. Their goal was to see if adding a single supercapacitor to a solar array could calm the wild fluctuations caused by passing clouds, making the electricity safe and steady for everyday use. They did not just guess; they created a detailed digital twin of a solar panel, a resistive load representing a home or business, and a specific type of supercapacitor known as the Maxwell BCAP0310. This device, rated at 310 farads and 2.7 volts, was chosen because it is a common, real-world component used in many applications.

The team programmed their simulation to mimic a realistic cloudy day. They created a pattern of sunlight that rose and fell in a complex rhythm, combining slow, rolling changes from large clouds with faster, jittery shifts from atmospheric scattering. This resulted in the solar power output swinging wildly between roughly 118 watts and 250 watts over a five-minute period. In the first scenario, they let this raw, bumpy power flow directly to the load, representing a system with no storage. In the second scenario, they introduced the supercapacitor. This device was connected to the system with a simple rule: it would act as a buffer, soaking up extra power when the sun flared up and releasing stored power when the sun dipped, all guided by a filter that looked five seconds into the future to decide how much energy to move.

The results of the simulation were clear and measurable. When the supercapacitor was active, the electricity delivered to the load became significantly more stable. The most extreme spikes in power, which reached nearly 69 watts of fluctuation in the uncontrolled system, were reduced to about 54 watts. This represents a drop of roughly 21 percent in the worst-case jolts. The overall variability of the power, measured by how much it deviated from the average over time, also fell by about 18 percent. Perhaps most importantly for the health of connected devices, the voltage at the load terminals became steadier. The standard deviation of the voltage, a measure of how much the electrical pressure wobbled, dropped from nearly 2.0 volts to just over 1.6 volts, an improvement of 18 percent. The supercapacitor did this by constantly charging and discharging, its internal state of charge moving between zero and 69 percent, which proved it had enough room to operate effectively without running dry or becoming overfilled during the simulation.

The study also looked at the physical toll this smoothing took on the device. As the supercapacitor worked to balance the power, it generated heat due to its internal electrical resistance. The peak heat generation reached 12.28 watts during the most intense moments of cloud cover. While this amount of heat is within the safe operating limits of the specific component used, it highlighted a need for further study into how heat spreads through the device, suggesting that future work might need to combine electrical and thermal models to ensure long-term safety. The researchers noted that their approach was passive, meaning it did not require complex, active control loops or expensive converters to function, making it a simple and potentially low-cost solution for rural areas.

This work demonstrates that a supercapacitor can serve as an effective, short-term buffer for solar power, smoothing out the rapid fluctuations that typically plague off-grid systems. The simulation showed that even a single, relatively small device could significantly improve power quality, reducing the stress on equipment and making solar energy more reliable for communities that depend on it. The researchers concluded that while this was a successful proof of concept, the next step would be to combine this short-term smoothing with long-term battery storage and to investigate the thermal behavior of the device in greater detail. For now, the study confirms that in the absence of a traditional power grid, a supercapacitor offers a practical way to turn the erratic pulse of the sun into a steady, usable flow of electricity.