This technique takes advantage of the fact that the maximum power voltage (V MP) of a solar panel does not, typically, vary much as the amount of incident light changes (see " Solar Battery Charger Maintains High Efficiency in Low Light" for more information). Partially shaded solar panel showing multiple power maximaĪn intermediate approach is something that Linear Technology calls Maximum Power Point Control (MPPC). įigure 2.In between these periodic sweeps, the MPPT algorithm will continuously dither the operating point to ensure that it operates at the peak. When the sweep is complete, the circuitry forces the panel to return to its maximum power point. It does so by periodically sweeping the entire output range of the solar panel and remembering the operating conditions where maximum power was achieved. Typically, a full MPPT algorithm is required to find the true maximum power operating point. In multi-cell solar panels, it is possible to have more than one power peak during partial shading conditions (see Figure 2). The advantage of a full MPPT algorithm is that it can differentiate a local power peak from a global power maximum. The LT8490 and LTC4015 are examples of integrated circuits that perform this function. There are a variety of MPPT algorithms, but most will have some ability to sweep the entire operating range of the solar panel to find where maximum power is produced. The opposite end of the spectrum is an approach that implements a complete Maximum Power Point Tracking (MPPT) algorithm. When available power levels are very low (approximately less than a few tens of milliwatts), this may be the best approach. It relies on matching the maximum power output voltage of the panel to the relatively narrow voltage range of the battery. This technique is described here in the article " Energy Harvesting With Low Power Solar Panels". One of the simplest is to connect a battery to the solar panel through a diode. There are many different ways to try to operate a solar panel at its maximum power point. Put another way, since we cannot predict the availability or intensity of solar power, we need to harness as much energy as possible while energy is available. This is particularly true of a solar powered battery charger, where the goal, presumably, is to capture and store as much solar energy as possible in as little time as possible. Ideally, any system using a solar panel would operate that panel at its maximum power output. Solar panel I-V curve showing maximum power įigure 1.This voltage is typically around 70 – 80% of the panel’s open circuit voltage (V OC).In Figure 1 the maximum power is just under 140W with V MP just under 32V and I MP just under 4.5A. Most solar panel manufacturers will specify the panel voltage at maximum power (V MP). Under open-circuit conditions the output power is zero since the output current is zero. Under short-circuit conditions the output power is zero since the output voltage is zero. Let’s look into the definition and meaning of these terms in more detail.Īs can be seen in Figure 1, the output current of a solar panel varies nonlinearly with the panel voltage. When discussing solar panels and power, terms such as Maximum Power Point Tracking (MPPT) and Maximum Power Point Control (MPPC) are often used. Both of these articles mention a concept known as maximum power, which in the context of solar panels is the ability to extract as much power as possible from the solar panel without collapsing the panel voltage. Two recent articles, " Energy Harvesting With Low Power Solar Panels" and " Solar Battery Charger Maintains High Efficiency at Low Light", discuss how to efficiently harvest energy with low power solar panels. Techniques to Maximize Solar Panel Power Output
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