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Why Microinverters are a better option ?


string inverter vs microinverter

What is a Solar Inverter ?

A solar inverter is a device that converts the direct current (DC) electricity produced by solar panels into alternating current (AC) electricity, which can then be used to power homes and businesses. The inverter is an important component of a solar on grid system, as it allows the solar panels to interface with the electrical grid and other loads.


There are several types of solar inverters, including string inverters, microinverters, and central inverters. String inverters are the most common and are used in systems with a single string of solar panels. Microinverters are attached to each individual panel and can improve the performance of a PV system by allowing each panel to operate independently. Central inverters are used in large-scale PV systems and can handle the output of multiple strings of solar panels.


What are the types of Solar Inverter ?

There are several types of solar inverters that are commonly used in photovoltaic (PV) systems:

  1. String inverters: These are the most common type of solar inverters and are used in most residential PV systems. They are called "string" inverters because they are connected to a string of solar panels. String inverters convert the direct current (DC) electricity produced by the solar panels into alternating current (AC) electricity that can be used in a home or business.

  2. Central inverters: These inverters are used in large, utility-scale PV systems and are typically located at a central location within the PV array. They are designed to handle the high power outputs of many solar panels and are usually more efficient than string inverters.

  3. Microinverters: These inverters are attached to each individual solar panel and convert the DC electricity produced by the panel into AC electricity. They are a good option for PV systems with shading issues or for those that want to maximize their energy production.

  4. Battery inverters: These inverters are used in PV systems with energy storage, such as in a home with a solar battery. They are designed to charge the battery with electricity produced by the solar panels and to discharge the battery as needed to power the home.

  5. Hybrid inverters: These inverters are a combination of a string inverter and a battery inverter, allowing them to both produce electricity from solar panels and store excess electricity in a battery for use later.


What is the difference between String Inverter & Microinverters ?

String inverters and microinverters are both devices used in photovoltaic (PV) systems to convert the DC electricity produced by solar panels into AC electricity suitable for use in homes or businesses. The main difference between them lies in how they are connected to the solar panels and how they operate.


String inverters are a type of central inverter that are connected to multiple solar panels in series, forming a string. They convert the DC electricity from the string into AC electricity that can be fed into the power grid or used on-site. A string inverter typically has a higher power rating than a microinverter and is located at a central point in the system, often in a protected environment, such as a garage or basement.


On the other hand, microinverters are small inverters that are mounted on each individual solar panel. They convert the DC electricity produced by the panel directly into AC electricity, which can be fed into the power grid or used on-site. Unlike string inverters, microinverters operate independently of each other, allowing for greater flexibility in system design and better performance in shaded or mismatched panels. Microinverters are also typically easier to install and maintain, as they do not require as much wiring as a string inverter.


In summary, the main differences between string inverters and microinverters are their connection to the solar panels, location in the system, power rating, and operating characteristics. String inverters are connected to multiple panels in series, have a higher power rating, and are located in a central location, while microinverters are mounted on each individual panel, have a lower power rating, and operate independently of each other.


Which is the biggest player in microinverters ?

Enphase Energy is considered the biggest player in the microinverter market. The company, founded in 2006, pioneered the development of microinverters and has since become a leading supplier of microinverter systems for residential and commercial solar installations. Enphase has shipped over 30 million microinverters worldwide, and its products are used in over 130 countries. The company's microinverter systems are known for their reliability, efficiency, and ease of installation, and they have won numerous awards for their innovation and performance. Other major players in the MLPE technology include SolarEdge, SMA Solar Technology.


What is a microinverter ?

A microinverter is a very small inverter designed to be attached to each individual solar panel. This is very different to standard string solar inverters, which are usually located on a wall some distance from the string of solar panels and connected via DC cable. In string inverter systems, DC power from the string of the panels is then converted to AC at the inverter. Since micro Inverters are attached to every solar panel, each panel works independently from the rest of the solar array and DC power is converted to AC immediately on the roof. Some solar panels are also available with factory-installed microinverters, these are referred to as AC solar modules.


Advantages of Microinverters

Shadow on solar panel mlpe

The main advantage of microinverters is that each panel is monitored and optimized individually to generate maximum power. Solar panels can generate different amounts of power due to a number of reasons, such as shading, dirt and mismatch, as explained in detail below. In a standard string installation, the panels are linked together in series, and the power output of the entire string can be significantly reduced by a single poor-performing, shaded or dirty panel. However, using micros can overcome this and help avoid the many reasons solar systems can under-perform including:

  • Shading – Trees, buildings, poles, wires, antennas, or rooftop structures

  • Soiling – Dust, snow, bird droppings or birds

  • Panel mismatch – various manufacturing tolerances

  • Panel faults – micro cracking, hot spots or water ingress

  • Temperature difference – thermal mismatch at different times of the day

  • Panel Ageing - Panel degradation at different rates over time

  • No PID – Eliminates Potential Induced degradation

  • Odd roof layouts - Panels mounted at multiple orientations and angles

  • Small roof - Roof areas that can only fit a small number of panels

Other advantages of microinverters

Considering the issues listed above, microinverters can significantly improve performance as they allow all panels to operate at their maximum power point (MPP) and not be affected by the lower performance of other panels. Another advantage of micros is the ability to locate panels on multiple sections of complex roof layouts with different orientations and tilt angles. Unlike string inverters, microinverters are not restricted to panel placement which is generally limited to two or three different orientations. String inverters generally have only two string inputs (MPPTs) and thus can only work with two groups of panels. Furthermore, the strings must have enough voltage to operate the inverter, which means they typically need to be at least four panels in a string. Microinverter systems are not restricted by any of these limitations.

  • No single point of failure

  • Not limited by string voltages

  • Easily expanded with a different model or newer panels

Microinverter systems have no single point of failure, which is particularly important in a large system with many panels. This means that unlike with string inverter systems if one panel or microinverter has a serious fault, the rest of the system is unaffected, and it doesn't result in a complete loss of generation.


Enphase Microinverter Range

buy enphase IQ7+ Microinverter

Enphase Energy now has two families of microinverters, the current seventh-generation IQ7 series and the new eighth-generation IQ8 series. Unfortunately, the IQ8 series is still only available in North America. IQ8 micros are available in a large range of sizes to suit specific panel sizes and voltages, in particular, the more powerful commercial solar panels rated up to 550W. Release dates for other countries are still pending.


IQ7 Series

The IQ7 series has been around since 2018, and several new variations have been released over the years, the latest being the more powerful smart grid-ready IQ7A microinverter. Due to increasingly larger and more powerful solar panels coming into the market, the IQ7A has a higher continuous power rating of 349VA, up from 320V on the IQ7X. However, unlike the IQ7X, the maximum DC input voltage is limited to 58V, which is compatible with the latest 60 and 72-cell panels, or 120 and 144 half-cut high-powered solar panels up to 460W. The 96-cell panels, such as those from Sunpower and Panasonic, are only compatible with the IQ7X.


buy enphase IQ 7A microinverter comparison

System and panel level monitoring device : Enphase Envoy


Microinverters offer better system monitoring compared to string inverters, as each panel can be monitored individually. Note, for those with standard string inverter systems, additional panel-mounted 'DC optimizers' such as those from Tigo or SolarEdge can also enable individual panel-level monitoring and optimisation. However, the extra cost and real-world performance of these alternatives are debatable.

buy enphase microinverter envoy online india

With microinverters an owner can see the performance of the system as a whole, plus at the individual panel level. Also, the installer can have a separate login where they can monitor all their systems at a panel level and are warned when any panels are under-performing which can prevent system downtime and help with any warranty claims. Enphase Energy has the Envoy monitoring hub for all systems to enable setup, commissioning and remote monitoring. They also monitor all registered systems worldwide from the US headquarters which provides valuable information to monitor fault conditions and continue to improve their products.


Reliability

Most microinverters have been rigorously tested in extreme weather and climate conditions. These units are designed to last the life of a solar panel and generally have a warranty to back that up. Many microinverters, such as those from Enphase, come with a 10-year warranty. To date, there have been very low failure rates reported by our solar specialists, and Enphase has proven to be one of the most reliable inverter manufacturers in the world.


High Temperatures

Enphase tested and monitored the performance of their micro's during the 2014 Australia summer in Adelaide, which had the most consecutive days over 40C (104F) in its recorded history and peaked at 45.9C (115C). Because of the advanced monitoring of their inverters, they were able to announce that “No Enphase Micro inverter across Australia shut down due to high temperature” during this period. Other manufacturers also have very stringent testing of their inverters and have performed well in hot and freezing temperatures. It cannot be inferred that all micros are up to this standard, though and there are several competing brands that have recorded much higher failure rates by installers.


Safety - AC vs DC

In standard string inverter systems, high-voltage DC electricity is sent via cables from the strings of panels, usually through the roof or wall cavities, to an inverter that converts the DC into AC electricity. If the cable is damaged, the high string voltage, which is often 400 to 500 volts, can cause dangerous arcing, which is very difficult to extinguish. Additionally, if a single cell is damaged in a panel, it will often turn into a hot spot due to the reverse current bias and high voltage, resulting in a thermal runaway that can burn the rear side of the cell. In a worst-case scenario, this can even result in a fire.

In a microinverter system, the panels produce DC power, which is immediately converted to AC on the roof. This is important because AC arcing can be easily detected and isolated, unlike high-voltage DC electricity, which is more likely to cause arcing and heating, leading to a potential fire. It is very important to bear in mind that fire from any solar system is very unlikely, especially if correct installation methods are taken.


What to avoid using microinverter ?

A factor that should be considered when looking at microinverters is that there are far more inverters in one solar installation than with a string inverter. In an 8kW system using 400W panels with micros on each panel, there will be 20 inverters. This means that if the micros being used have the same failure rate as a mid-range string inverter, there is 20 times more chance of a failure than with that string inverter. This leads to the obvious cost disadvantage; while a single microinverter is much cheaper than a string inverter, purchasing 20 microinverters is much more expensive than one string inverter. However, unlike string inverter systems, a single failed microinverter will not affect the rest of the system, and the remaining microinverters will continue to operate as normal.

The most apparent reason why microinverters may not be the best choice is due to the mounting location on the roof, where they are generally exposed to extreme heat, humidity and potentially salt mist when located near the ocean. This is where string inverters have the big advantage of being mounted in more protected locations or even indoors. Most microinverters are tested and built for these weather extremes, but over the years, some microinverters have had multiple faults, especially when in harsh conditions such as high humidity and in close proximity to the ocean with extreme salt corrosion.


Cost and Savings

A microinverter system's upfront cost is generally higher than a regular string inverter system. On smaller systems around 3-4kW, micros are comparable to string systems since the cost of one good quality string inverter is equivalent to the cost of 8-10 micros, which are relatively cheap. Although on a larger 8kW system, the cost difference becomes more significant as one single string inverter becomes significantly cheaper than 18 to 20 microinverters.


However, microinverters have a significant cost advantage when it comes to upgrading a system in the future, as you do not have to replace the inverters with a newer, larger model. Microinverter systems are unique in that you can add additional panels, of a different make or model, without having the modify the existing system. Solar panel technology is advancing rapidly, so it is often impossible to source the exact model panel even after only one year. String inverter systems cannot mix different types of panels, and often the entire system has to be replaced to increase the solar capacity resulting in a far greater cost.


Looking to get solar panels installed for your home or business, contact the best solar installer i.e. HV Solar today @ 8700102836 or submit your details on www.hvsolar.co.in



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