source:www.europe-solarshop.com/

Understanding Power Optimizers

A power optimizer or solar optimizer is an electrical component that can be added into a solar power system. It is not a type of solar inverter, as it is often misunderstood to be. Instead, it is considered a kind of module-level power electronic (MLPE). 

In this article, we will touch on:

  • what power optimizers are and how they work
  • their lifespan, safety and installation
  • their pros and cons
  • the differences between power optimizers and microinverters
  • how to choose the right optimizer

What does a power optimizer do? 

A power optimizer can be considered a compromise between a microinverter and a string inverter. It is installed on individual solar panels like a microinverter but its function has nothing to do with converting DC to AC electricity.

Instead, a power optimizer uses a technology called maximum power point tracking (MPPT). It tracks the maximum power of each panel in real time, then smooths and conditions DC electricity generated by each panel before sending it to the solar inverter. This way the solar inverter can process much more electricity. 

Similar to what microinverters can do, a power optimizer reduces the impact of panel shading on system performance and offers panel-level performance monitoring.

Power optimizers work to ensure that you are getting the most out of your PV array, which makes them a perfect compliment to compatible string inverters. They can also work under extreme environmental conditions though with less efficiency on days with bad weather.

As such, a solar power system with optimizers will have a more efficient DC output than one without.

source:www.europe-solarshop.com

Lifespan of a power optimizer

Power optimizers are a relatively new technology in the solar industry. Their standard warranty is up to 25 years, which is the same as most solar panels.

Are power optimizers safe to use?

Yes. In fact, they include a safety voltage function that automatically reduces the output of each power optimizer to 1 Volt DC in the following cases:

  • during faulty conditions
  • disconnection between modules and the optimizer
  • when the solar inverter’s switch is turned off
  • when the Safety Switch is turned off
  • when the solar inverter’s AC breaker is turned off

Additionally, there are a number of options for grounding depending on your racking components and city regulations.

Are power optimizers easy to install?

Yes, installation can be done quickly and easily. Power optimizers can be installed in any orientation, which makes them extremely versatile. 

Nonetheless, they should be installed close enough to one another so that their cables can be connected. In addition, there must be enough clearance for heat dissipation. The maximum and minimum string length will vary according to the power optimizer, inverter and size of a solar power system.

Are solar power optimizers worth it?

Generally, the advantages of having optimizers trumps the disadvantages. The final decision of whether to have them ultimately depends on your needs.

Advantages of power optimizers 

1. More efficiency in partially shaded conditions

When solar panels are partially shaded or when they are installed in a roof with multiple angles, the DC output of the modules will be below par. Power optimizers allow you to increase the output of those panels which are affected by shading and panels which do not get direct sunlight.

2. Monitoring of every solar panel

As a type of MLPE, solar optimizers are able to collect solar energy production data such as output voltage and peak efficiency from each PV panel. This data can be sent to the cloud, where you can get real-time updates of the performance of each panel in an app. 

3. Smaller solar inverter size

Since the voltage tracking and optimizing happens at the individual module level, the solar inverter tied to power-optimized solar modules doesn’t need to be as big in size. The voltage capacity must match the total potential output of all the panels and optimizers but the inverter model for this type of system tends to be less bulky.

4. Less downtime in DC output

Even if one optimizer fails, the solar panel it is attached to will still produce electricity; just less than it should with the optimizer functioning. However, if a microinverter fails, DC power will totally stop for the panel that it is attached to.

Disadvantages of power optimizers

1. Limited inverter selection

Power optimizers must be paired with a matching solar inverter. As optimizers are still relatively new to the market, it can be tricky to find the right solar inverter for the system.

2. Higher installation cost

If you are going for an optimizer system, you will need to install one power optimizer for every single solar panel. This will make your overall installation cost a little higher than a traditional string inverter solar panel system. However, it is still cheaper than microinverters, and the overall long-term savings make the initial higher cost worth it if your panels experience shading.

What is the difference between a microinverter and a power optimizer?

Similarities

Both the microinverter and power optimizer allow you to monitor the performance of individual PV modules. 

Both solve challenges from conditions of non-optimal lighting where solar panels are shaded or do not face sunlight directly. A power optimizer maximises the DC output of a PV panel like a microinverter when light conditions are poor. 

Differences

Installation of microinverters is pricier than power optimizers, as the former has a more complex circuitry. Microinverters are also bulkier electrical components than power optimizers which causes them to have a higher lightning risk. 

The function is also different for both. Power optimizers only condition DC to DC energy before sending it to a solar inverter. It does not convert DC to AC power like a microinverter. 

Another key difference between a system with microinverters and a system with optimizers is that the latter is harder to scale over time. This is because power optimizers are tied to a central inverter, which has limitations in the amount of power it can handle. 

Microinverters need more maintenance than power optimizers. The lifespan of microinverters can vary greatly, from as short as 5 years to as long as 12 years, depending on the model and brand. On the other hand, power optimizers can last almost 25 years, double that of microinverters. 

However, microinverters are less likely to affect the performance of a system than optimizers. That is because an optimizer system depends on a central inverter. If an optimizer fails, it is likely to affect the inverter.

  Power Optimizer Microinverter
Lifespan Longer Shorter
Cost Moderate High
Ease of system expansion Challenging Very easy
Lightning risk Low Moderate
Panel-level monitoring Yes Yes
Performance with multiple roof angles Excellent Excellent
Performance in shade Excellent Excellent
Likelihood of system interruption Lower Higher

Table 1: Summary of comparison

How to choose a power optimizer

When comparing options, there are a few main factors to keep in mind:

1. The existing capacity of your inverter

The premise for this point is for those who already have an existing solar power system. Care needs to be taken when considering the quantity and wattage of the correct optimizer for your system. 

This is because inverters are meant to convert AC power to a level that can’t be exceeded. If you are boosting DC power using optimizers, your inverter will limit the production of your panels to the amount of AC it can convert. The inverter can still function despite a higher payload, but the excess electricity routed to your inverter can shorten its lifespan.

2. Efficiency of your inverter

Just like solar panels, power optimizer systems have different degrees of efficiency. Efficiency is a measure of how much energy is lost in the form of heat during the conversion from DC to AC electricity. Whether you have power optimizers or not, the solar inverter tied with your system also plays a role in higher overall system efficiencies and more solar electricity production.

3. Size of power optimizer

Power optimizers come in different sizes designed to handle different maximum voltages. The size of the optimizer follows the wattage rating of the modules themselves. For example, a 300-Watt panel would likely use the 320-Watt power optimizer. 

You will need to pair a matching sized inverter with the power optimizer chosen as well. The bigger your optimizer capacity, the bigger your inverter capacity must be also. 

That being said, you also do not want to choose an inverter or optimizer that is too small for your system. The sizes of both are affected by the energy output of your existing or new solar panels. 

4. Your budget

Bear in mind that you need one power optimizer per solar panel if you are proceeding with an optimized system for a residential installation. Commercial installations sometimes have one optimizer for every two panels. 

In addition to the quantity of optimizers, the cost will also be affected by the warranty periods associated with different brands. Typically, the longer the warranty, the higher the price tag.

Conclusion

Power optimizer systems offer a hybrid solution between a solar power system with a traditional string inverter and a system with microinverters. It is ideal for setups that experience shading or complicated roofs which experience indirect sunlight. 

A power optimizer is a type of MLPE. Installed on a solar panel like a microinverter, it conditions DC electricity at the panel itself, optimizing the voltage before sending it down to the inverter for conversion. 

However, it does not convert DC to AC. A power optimizer system needs a solar inverter for this process. The trick with installing optimizers is to ensure the outcome of total power output does not exceed the capacity of the inverter in the system. 

Although adding optimizers increases the total cost of a solar installation, the benefits gained from doing so outweigh the disadvantages. They are also cheaper than microinverters and offer the possibility of less interruption in the power supply.

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