One of the great debates of the solar industry is between the up and coming microinverter and the older, more conventional string inverter.
Microinverters took the industry by storm, touting better performance under shading and panel level monitoring for when things go wrong.
String inverters, on the other hand, market themselves as having fewer moving parts, higher efficiency (on paper) and a less complicated install.
As the war raged on, it seemed that the microinverter alliance was gaining ground on the old guard.
But with the rise of DC optimizers, the trusty string inverter has made a comeback.
One company leading the charge is SolarEdge, a premium inverter manufacturer out of Israel.
In fact in 2010, shortly after launching their optimizer product, SolarEdge shipped 250,000 DC optimizers or 70% of the global market.
It’s safe to say that SolarEdge is worth considering if your system requires DC optimizers to get the most out of your panels.
How Do They Work?
DC optimizers provide the best of both worlds. They offer panel level optimization and monitoring while providing the cost-saving benefits and reliability of a string inverter.
In many ways, a DC optimizer is a more reliable and efficient choice when compared to microinverters. However, it is most definitely up for debate.
DC optimizers are attached to each panel, in many cases replacing the junction box. In fact, many panels are manufactured with DC optimizers already attached.
They function by using MPPT or Maximum Power Point Tracking.
Essentially, a solar panel’s ability to achieve maximum power output is dependent on the circuit’s voltage, current and load characteristics.
MPPT is constantly tracking all of these variables and altering the current and/or voltage to draw out the most power under all conditions, come sunshine or rain.
While standard inverters use MPPT or PPT at a system level, they are unable to make changes on a panel level.
This can be particularly problematic for systems which experience partial shading or have panels across a multi-faceted roof.
This is because the panels experience different levels of sunlight, creating imbalance across each string.
In fact, panel mismatch is a phenomenon that occurs when one panel is manufactured to be less efficient than the panel next to it, causing a dip in production across the system.
As many of you might know, if one panel is underperforming, the entire string experiences diminished power output.
Without panel level optimization, the system is reduced to the lowest common denominator.
DC optimizers aim to reduce the impact of shading across a string, by optimizing at the panel level and increasing power output as much as possible.
Benefits of DC Optimizers Over Microinverters
DC optimizers are attempting to be the answer to the rise of microinverters.
There is definitely an argument to be made that DC optimizers offer both the benefits of standard string inverters, as well as many of the benefits of microinverters.
Supersizing Your Solar Array
Regulations have led to Enphase and other microinverter manufacturers having to limit the output of each unit to 230W.
This is because the AC coupled output of residential property cannot exceed 5kw.
That means a microinverter system can have no more than 21 microinverters on a single system (5000W divided by 230W is 21.7, by rounding down we get 21 microinverters).
The same applies to string inverters. However, if a system is utilising a string inverter, the total number of panels is not directly tied to the size of the inverter, whereas for a microinverter system, the total number of panels that can be installed is capped at 21.
In other words, a microinverter system’s total output is heavily handicapped.
For example, in a 21-panel system, Enphase’s microinverters will allow for a total inverter output of 4830W.
If we were to use 275W panels, the maximum production the system could achieve would be 5.775kW (275W multiplied by 21).
Still following? Good.
A string inverter system, on the other hand, can have as many panels as necessary, as long as the total production capability is no larger 1.3 times the inverter output (the CEC recommends supersizing the solar array by no more than 33%).
For example, SolarEdge’s 5kW inverter has an output of 4985W, which when multiplied by 1.33 is 6630W, or 24 275W panels.
Simply put, because a microinverter system requires a 1:1 ratio between the number of panels and microinverters, a DC optimized string inverter system can achieve a greater total output while still optimizing and monitoring at the panel level.
When coupling a battery to an existing system, it’s always recommended that the battery is DC coupled.
This means that the battery is connected to the rest of your system on a DC circuit. That’s because batteries store power using DC electricity.
Given that DC optimizers use DC current up until the inverter, it becomes far easier to DC couple your new battery.
By doing so, your system will be far more efficient.
Microinverters export AC power only, meaning that a battery would have to be AC coupled.
Therefore the electricity is inverted twice, once from DC to AC and again from AC to DC, before reaching your battery.
This will result in subsequent power loss and a lower return on your investment.
Unique Features of SolarEdge’s DC Optimizers
SolarEdge states that by using their DC Optimizers your system can reach efficiency levels of up to 99.5%.
This is compared to standard inverter efficiencies that range between 95% and 98%.
For example, the Fronius inverter, which is widely considered to be a premium inverter, has a max efficiency of ~97.5%.
SolarEdge is fairly confident in their product as well, providing a 25-year warranty on all power optimizers.
But these features could arguably be found in most optimizers. What’s most interesting is what SolarEdge has provided that others have not.
Module Level Monitoring
One of the main benefits of choosing SolarEdge is that their DC Optimizers are linked up directly with their advanced monitoring system.
By receiving panel level information on your system’s health, you can make better decisions about how to fix damaged components, remove shading or alter your electricity usage.
If for some reason you choose not to couple SolarEdge DC optimizers with a SolarEdge inverter, don’t worry.
SolarEdge has implemented IndOp™ or independent operation technology into their optimizers.
This means that the optimizers can function regardless of the inverter type and require no additional interface.
To ensure the safety of both your home, firefighters, and installers, their optimizers come equipped with SafeDC™.
This means that if the grid goes down, your panels are ‘switched off’ at the panel level, preventing potential electrocution or damage to your home.
DC optimizers provide homeowners with a third choice for getting the most out of their solar system.
SolarEdge’s DC Optimizers combine panel level optimization with the cost savings and simplicity of a string inverter.
Increase your system’s efficiency and increase your return on investment while getting access to panel level monitoring and advanced safety features with SolarEdge’s DC Optimizers.
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