Solar panels are the most visible and recognizable part of a solar power system . However, inverters are equally important as they convert DC power from solar panels into AC power used by electrical devices. The inverters also synchronize with the local grid, so the building can use electricity from the solar panels and the grid at the same time.
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Inverters are slightly smaller than solar panels and this design decision has an economic reason. Solar panels reach peak output for brief periods around noon and generate partial power for the rest of the day. If an inverter is sized according to the peak power of the solar panels, part of its capacity will be wasted. For example, you might find a 60 kW solar panel with a 50 kW inverter.
- The difference between the power of the solar panel and the capacity of the inverter is called the DC/AC ratio or inverter load ratio (ILR).
- If you have 133 kW solar panels and a 100 kW inverter, the DC/AC ratio will be 1.33.
In this blog post, we will describe the main types of solar inverters and their performance characteristics.
Types of solar inverters
String inverters are the most common type and get their name because solar panels are wired together in “string circuits” and then connected to the inverter. Generally, higher capacity inverters have a greater number of string circuits. For example, a 10 kW inverter may have 2 or 3 circuits, while a 60 kW inverter may have 12.
Microinverters are small devices connected directly to solar panels, rather than connecting them to a central inverter with string circuits. Microinverters can achieve greater efficiency since the electricity production of each solar panel is controlled individually. However, one inverter is required per panel, which makes installation more expensive and laborious. The maintenance needs of these systems are also more complex – if you have 300 solar panels, you also have 300 microinverters.
String inverters with power optimizers combine both concepts described above. Solar panels are wired into string circuits and connected to a central inverter, but they also have individual power optimizers – DC-DC converters that regulate voltage and current, to maximize the power delivered by each panel.
What is a hybrid inverter?
Solar inverters are only designed to handle the flow of energy in one direction: from the solar panels to the building, while sending excess electricity to the grid.
However, many solar installations are now equipped with battery systems , and their operation becomes more complex. Electricity can now move in multiple directions, and below are some examples:
- From solar panels to the building
- From solar panels to batteries
- From solar panels to the electrical grid
- From batteries to the building
- From batteries to the electrical grid
- Simultaneously from solar panels and batteries to the building
A traditional string inverter is not designed to manage all of these energy flows – you need a hybrid inverter to use solar power with energy storage. Solar panels are typically connected in string circuits when using a hybrid inverter, and some models are compatible with power optimizers.
Hybrid inverters typically come with built-in monitoring tools, which provide a clear picture of system performance. For example, you can check how much solar electricity is being consumed by the building, stored in the battery system, and exported to the grid.
Understanding MPPT – Maximum Power Point Tracking
Solar panels provide the most energy when operating at the ideal voltage and current. However, its operating conditions constantly change, as sunlight varies throughout the day and the climate constantly changes. This means that the ideal voltage and current are not constant.
An MPPT is an electronic device similar to a power optimizer that increases the productivity of solar panels. However, rather than optimizing an individual module, an MPPT circuit optimizes an entire series of modules. MPPT circuits are also part of the inverter and are not installed separately as power optimizers.
Solar panels are often divided into groups of panels to take advantage of available roof area. However, this also means that groups of solar panels will have different orientations and operating conditions. Ideally, solar panels with similar conditions should be connected in the same chain and optimized by the same MPPT circuit.
Conclusion
Inverters are just as important as solar panels, as they convert your DC energy into a usable form while optimizing your electricity production. Hybrid inverters are very useful if you plan to add energy storage, as they can control solar panels and batteries simultaneously without external devices. If you want to install solar panels and are thinking about batteries in the future, the best option is to use hybrid inverters from the start – this will save you having to replace them later.
