What is Maximum Power Point Tracking (MPPT) in a solar inverter?
How much electricity solar panels generate depends on sunlight and environmental conditions. When these conditions change, MPPTs track and adjust the electrical load, ensuring the panels operate at their peak efficiency.
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The topic in a nutshell
It continuously adjusts voltage, depending on the solar panel's current to extract the highest possible power in all conditions.
With fewer hours of sun in the winter, the efficiency improvements of the MPPT are much needed to maintain a high enough power output.
Systems with multiple MPPTs optimise output from different roof orientations and shading.
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What is a solar inverter MPPT?
A maximum power point (MPP) is the point at which a solar panel produces its maximum power output. It depends on sunlight, temperature and the electrical load drawing from the panel. An MPPT inverter adjusts the electrical load dynamically, even as sunlight and conditions change, making your system as efficient as possible.
How does an MPPT work?
The MPPT algorithm utilises a DC-DC converter to dynamically adjust the solar panel's operating voltage to align with its maximum power point. When environmental factors such as sunlight intensity or temperature change, the MPP shifts, and the algorithm swiftly modifies the panel’s voltage to track and maintain this optimal operating point.
The concept of MPPT is best understood with the current-voltage (I-V) curve of a solar panel. The relationship between power, voltage, and current is expressed as:
Power (W) = Voltage (V) × Current (A)
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As the voltage across the panel changes, so does the current, resulting in a curve where power is maximised at a specific point. For optimal energy generation, the panel's operating conditions must remain as close as possible to these values.
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The challenge arises because the I-V curve, and thus the MPP, varies with sunlight intensity and other environmental conditions. As the level of solar radiation hitting the panel changes, the MPPT algorithm adapts the operating voltage to maintain maximum power output. This dynamic adjustment ensures solar panels consistently deliver peak performance under all conditions.
When is an MPPT more efficient?
MPPTs are particularly effective under the following conditions:
- Cold and cloudy weather, when the need for extra power is greatest. Solar panels perform more efficiently at lower temperatures, producing higher voltage. Without an MPPT controller, much of this potential is wasted. Winter, characterised by colder temperatures and fewer sun hours, is when this efficiency boost is most needed, as it helps recharge batteries during the season with the highest energy demand.
- Low battery charge: When your battery’s state of charge is low, an MPPT controller delivers significantly more current to recharge it quickly. This ability is especially critical during periods when the extra power is most needed, such as cloudy days or during heavy energy use.
- Long wire runs: When your solar panels are located far from your battery, voltage drop and power loss can be significant unless expensive, heavy-gauge wiring is used. With MPPT, multiple panels can be wired in series to create a high-voltage array. This setup minimises power loss over long distances and allows for smaller, less expensive wires. The MPPT controller then converts the high voltage from the panels to the appropriate lower voltage required to charge the battery, ensuring efficient energy transfer.
What are the key advantages and disadvantages of an MPPT?
The table below outlines the key advantages and disadvantages of MPPT technology:
Should I go for single or multiple MPPTs?
Inverters were originally designed to have a single MPPT, which means the inverter can maximise the output for 1 value of current (e.g. one side of the roof). For simple PV arrays, a single MPPT is usually sufficient. It would look at the total output of the panels and compare it to the battery voltage and then figure out the best power that the panel can put out to charge the battery.
For larger and more complex designs, having the PV array managed by more MPPTs will help to improve the energy yield. With multiple MPPTs, each MPPT is connected to a specific set of solar panels (e.g. for multiple sides of the roof), allowing them to operate independently and optimising energy production from each set separately. With multiple MPPTs, you can charge your battery more consistently, regardless of shading or panel orientation.
Frequently Asked Questions
What is the difference between panel tracking and Maximum Power Point Tracking?
Panel tracking and Maximum Power Point Tracking are both methods to optimise solar energy output, but they achieve this in different ways. Panel tracking involves mounting solar panels on a system that physically follows the sun's movement across the sky. This ensures the panels receive the maximum sunlight throughout the day. Depending on the season, panel tracking can increase energy output by around 15% in winter and up to 35% in summer, as the sun's angle is more optimal for longer periods.
On the other hand, Maximum Power Point Tracking is an electronic method that optimises the power output of solar panels by continuously adjusting the system to operate at the optimal voltage and current for maximum efficiency. This is particularly effective in winter, as solar panels produce more power at lower temperatures, and shorter days make maximizing output crucial. MPPT systems convert the panel's energy to achieve the highest possible current into the battery, improving efficiency by 20-45% in winter and 10-15% in summer. Both methods can complement each other, with panel tracking improving sunlight capture and MPPT maximising the conversion of that sunlight into usable energy.
Solar inverter MPPT is a very technical topic, so we understand you might have several questions. Please get in touch by answering the short survey below:
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