The Ultimate Guide for Solar Energy Inverters

The solar inverters work hand in hand along with the solar photovoltaic panels and the rest of the components in the energy system. The inverters play an important role in converting the collected sunlight into a usable form of energy. The same with the solar modules, the pricing of the inverters had also declined internationally in recent years. In fact, according to IHS, the average market price of PV inverters had fallen by 18% in the last two years. As a result, the price trend became more favorable for consumers. Thus, it increased the volume of the global installation of photovoltaic energy systems with even a positive prediction of double-digit growth in 2019. Nevertheless, as the prices continue to be competitive, the technology behind its manufacturing is consequently becoming more challenging as well to continuously deliver high-quality products at the least possible cost possible.

What is solar energy inverter?

A solar inverter, also known as a photovoltaic or PV inverter, is a type of an electrical apparatus that fundamentally converts a variable direct current (DC) output of the solar panel into an alternating current (AC) which can be utilized to power the typical appliances such as the television, microwave, refrigerator, and other similar electronic devices. Furthermore, the energy can either be stored into a solar battery, fed into the grid, or used for off-grid applications. 

What are the functions of solar energy inverter?

Solar inverters are considered by many as the “brain” of the project. It is a balance of system, or BOS as they say, component of the photovoltaic energy system. This simply means that the inverters encompass all the parts of the PV system including the wiring, switches, mounting system, along with other solar inverters, battery banks, and the battery charger. 

Generally, the circuitry of the device determines the input and output voltages, the frequency, and its overall power handling capacity. The conventional power inverter devices require a relatively stable direct current (DC) power source, such as a solar panel or battery, that is capable enough to adequately supply the power demands of the energy system. The input voltage is based on the design and purpose of the inverter. In the case where the power is derived from photovoltaic solar modules, the input voltage is between 200 to 400 volts DC. Through a complex process of electrical adjustments, the inverter then allows the DC to be converted into a utility frequency AC.

Furthermore, solar inverters come with special functions specifically designed to adapt to an array of PV modules. This includes Maximum Power Point Tracking (MPPT) or sometimes simply referred to as Power Point Tracking (PPT). This is a technique used by the photovoltaic systems in order to maximize power extraction despite any given condition. Another specific feature is Anti-Islanding Protection. Islanding is a particularly dangerous condition wherein the distributed generator incessantly delivers power to a location despite the absence of the electrical grid power. This kind of circumstances posts a great deal of safety hazard to utility workers. Thus, the Anti-Islanding Protection offered by the inverters enables the detection of islanding which then triggers an immediate disconnection from the circuit to prevent any form of untoward incidents to occur.

What are the main types of solar energy inverters?

Stand-Alone Inverters

Also, referred to as the Off-Grid Inverters, this is essentially the “basic” type of inverter. Apart from converting the DC electricity into an AC, it also increases the amplitude of the voltage thereby causing changes in the frequency. It is often used in isolated energy systems wherein the inverter derives its DC power from batteries charged by the PV modules. In addition, Stand-Alone Inverters do not interfere with the utility grid. Hence, it may not necessarily come with anti-islanding protection.

Grid-Tie Inverters

As the name implies, the output AC power of this classification is supplied to a grid-type network. Consequently, it is built with complexity in its construction and internal circuitry for it to be able to synchronize accordingly with the grid network system. The grid-connected inverters transform the DC power generated from the PV modules into an AC power to supply electricity to homes or facilities and then sell the excess power back to the utility grid. That being said, the inverter inherently enables seamless connection into the grid to allow the continuous supply of power regardless of how much or little is the capacity of your solar panels. As a safety precaution, however, this type of inverter is particularly designed to automatically shut off upon disruption in the supply. Back up power is not provided during utility outages.

Types of Grid-Tie Inverters:

  • MICRO INVERTER – This type of grid-tie inverter is a small, self-contained device that is connected to a single PV solar panel. The AC produced from every micro inverter is then combined all together and sent into the grid for distribution. The micro inverters are more efficient in a way that it does not affect the entirety of the system should there be instances of shading or panel failures. Instead, the rest of the unshaded or undamaged solar panels can still continue to deliver power as usual.
  • STRING INVERTER – Unlike the micro inverter, this type is attached to one or more series of solar panels. As a repercussion, during occasions where there is a drop in power in at least one of the modules, the entire system is affected. Thus, among all the types of grid-tie inverters, this one has the highest tendency to become less efficient in generating power. Considering its drawback, the price point for string inverters is set to be less expensive.
  • CENTRAL INVERTER – The central inverter is similar to string inverters but rather than the strings running directly to an inverter, the string in the central inverter type is connected all together in a combiner box which runs the DC power to then be converted as an AC. This kind of inverter system is mainly used in large buildings, industrial facilities, and other utility-scale applications.

Hybrid Inverters

Also known as the “Smart-Grid Inverters”. This versatile all-in-one system is relatively a combination of both grid-tie and off-grid inverters. The hybrid inverter intelligently determines whether to consume or store the generated energy. So when the utility power is normal, the inverter functions like a grid-tie that supplies the load to the home or establishment then feeds the excess back into the grid. Nevertheless, whenever deemed necessary, the smart-grid inverter also stores energy in the battery system when there is more amount produced than the actual consumption. Hence, during times when the utility power is not available, the inverter can then act as a back-up power source similarly like how an off-grid inverter operates. 

COMPARISON BETWEEN EACH TYPE OF INVERTER

Stand-AloneGrid-TieHybrid
AdvantagesCheaperEnergy self-sufficientFinancial benefits through net meteringUtility grid serves as a virtual batteryCheaper in cost than Stand-Alone inverterInnovative all-in-one device
DisadvantagesNo access to the utility gridMay require a backup generatorThe initial cost is expensiveProne to “islanding” hazardsThe smart meter is more expensive than traditional power meters
Equipment RequirementsOff-grid inverterBattery bankCharge controller/Battery regulatorDC disconnect (additional)Back-up generator (optional)Grid-tie inverterPower meterBattery-based grid-tie inverterBattery bankCharge controller/Battery regulatorSmart meterDC disconnect (additional)

What are the 3 basic types of inverters according to power outage waveforms?

SINE WAVE INVERTER

Sometimes called “pure” or “true” wave. This type is similar to that of the supply we acquire from the local utility companies and generators. Sine waves are naturally produced from a rotating AC machinery. The biggest advantage of this kind of wave is that it is widely compatible with most equipment sold in the market today. Thus, rest assured that this will provide the user with an output that guarantees to power any modern devices safely and properly. Given its capabilities, its price point tends to be steeper too compared to other wave inverters.

MODIFIED SINE WAVE INVERTER 

This type is primarily a modified square wave. It tends to have a waveform resembling that of a sine wave but just less complex. Hence, this inverter is still somewhat suitable to use with most appliances. However, it is bound to deliver less power and efficiency than the pure wave inverters.

SQUARE WAVE INVERTER

This type of inverter is the cheapest in cost essentially because it is rarely used as well since the majority of the household appliances nowadays are practically designed to accommodate sine waves. Attempting to apply a square wave into a sine wave-compatible device can cause significant damage. It is, however, still can be used for simple tools with a universal motor.

How to choose the right size of solar energy inverter?

Now that you already have an idea of what type of inverter is suitable for your needs, it is also critical to select the right size of the PV inverter to maximize its efficiency. Regardless of how big or small the installation is, the fact that the solar power system is generating and transmitting DC electricity through the inverter, it is just deemed necessary as well to make sure that inverter size is sufficient enough to handle the load and effectively convert it to an AC electricity. 

  1. Inverter Rating

Before anything else, it is crucial to understand how inverters are rated. There are two ways to rate inverter. The first is in Watts or Continuous Watts. This refers to the total amount of watts the inverter is capable of supporting for an indefinite span of time. Now, in order for your inverter to be the right size, its watts rating should approximately be tantamount to that of the PV system. So, for example, if your solar PV system has a watt rating of 2000 watts. Then, your inverter should ideally have a continuous watt rating of around 2000 watts as well. A little bit more is okay, though, probably not too much since this may also cause the efficiency to decline too. In case you are using multiple appliances simultaneously, what you need to do is to add the continuous watts of all the devices to countercheck if your inverter can accommodate such amount of load.

The second way to rate an inverter is through its Surge Watts. This pertains to the amount of power the inverter is capable of handling in a very short period of time. In order for your inverter to be the right size, its surge watt must approximately be at least equal to or greater than the potential surge watts of the appliance you intend to power. So, let’s say that a 2000-watt inverter was rated with a surge watt of 4000. This means that the inverter is capable of handling up to 4000 watts momentarily to power appliances that usually requires greater amount of energy to get started, just like when kickstarting a motor for example.

  1. Input Voltage

Another rating you should determine when you’re trying to size an inverter is its input voltage. Basically, the inverter must have the same input voltage as the solar panels and the battery bank. The input voltage of the inverter also depends on its watt rating. So when you have an inverter with relatively minimal power, like about 100 watts only for instance, then the voltage requirement will typically be 12V, 24V or 48V. Likewise, the inverters with higher power capabilities will also bear greater input voltage.

  1. Wire Length & Solar Power Performance

To some extent, the performance of the inverter can be affected by the distance between the solar panels and the battery system. Technically, the longer the wire the lower the inverter’s voltage should be in order to deliver optimum performance. That is because long wires cause the voltage to drop while increasing the current. Vice versa, the higher the voltage, the lower the current and the shorter the length of the wire you can use. 

  1. Inverter Stacking

There may be times when you need more power so you resort to connecting multiple inverters to increase the overall capacity. This process of installing and wiring two small inverters together is called as Inverter Stacking. Doing such will either provide the user more power or higher voltage. Like if you wire two compatible inverters in series, you can double the output voltage. On the other hand, if you wire two inverters in parallel, then you end up doubling the power. Nevertheless, the invert stacking technique can ideally be done to solar power systems with a much higher watt rating than a single inverter is capable of handling. So for instance, you decided to wire two 2000-watt inverters together in parallel, then it is expected that it should be able to handle as much as 4000 watts of power in return.

  1. Solar Inverter Price

The low to a medium quality range of inverters, which roughly cost around $400 up to as much as $1000, is capable of serving small to medium-sized photovoltaic systems with considerably decent performance, reliability, and consistency. Consequently, expect that there will be a moderate amount of energy or performance loss as well. Nevertheless, if you’re using simple and not too high-tech appliances or if your overall solar applications aren’t too demanding, then this type of inverter should suffice. However, if you require a bigger system then a much better quality inverter would cost you between $900 to $1500 for a Modified Sine Wave inverters with 2000 to 3000 watts. Moreover, if you prefer to accommodate more devices and have automatic features, a True Sine Wave inverter might be more apt for your needs. However, it will definitely cost you $500 to $1000 more. The bottom line, the practicality and convenience should also be factored in when choosing the right inverter size.

How to choose the right solar energy inverter?

Now that you already have an idea of what type and how big or small you want your solar inverter to be, the guideline below will provide you further insights on what to consider when buying. 

  1. Research

Just like purchasing any other device or venturing into an investment, the initial yet relevant step in choosing the right product is research. Browsing the internet for reviews or conducting a short market visit will enable you to get an in-depth understanding of what makes one a fit for your needs. The first-hand experiences from the articles you read online and the recommendations given by the sales personnel add to your knowledge about which type is suitable, what size should you get, the most trusted brand in the market, and other factors. These bits of information are valuable in helping you evaluate and compare different inverters in order to come up with a better decision in the end.

  1. Parameters

The solar inverters do not generate electricity on its own. Thus, the series of parameters surrounding it must be well considered to ensure that it will deliver its function accordingly. Aspects such as the input DC voltage, output AC voltage, frequency, circuitry, and its overall suitability to your solar power system is worth looking into. For instance, a conventional residential photovoltaic system would require an average input voltage of 24 and 48 VDC.

  1. Tracking Devices & Other Accessories

Some solar inverters are manufactured with a built-in tracking device. This chipset conveniently detects any malfunction within and accurately pinpoints which component needs servicing or repair. Thus, it becomes easier for the user and the manufacturer to identify and troubleshoot the device. In addition, optional accessories such as a monitoring device would also be helpful to have around. This provides the user the capability to keep track of pertinent performance data of the inverter including how much power it can generate, your actual energy consumption, optimizing the usage, and more. 

  1. Weatherproof

Given that solar inverters are most often installed outdoors, it is a must to ensure that the device is equipped with stout features that would effectively handle the different weather conditions it might likely be exposed to. Consequently, extremely high temperatures can cause the voltage of the PV system to rise, and in the opposite, it falls under low temperatures. Abnormalities from the voltage specification may impair the function of the inverter or worse, induce serious damage. Hence, it is highly advisable to make sure that your inverter comes with a hard shell and perhaps an IP65 technology as well.

  1. Cooling System

Apart from weatherproofing your inverters, it is also equally necessary to secure its cooling system. Just like any other electronic device, proper ventilation is fundamental in prolonging the lifespan of your PV system. Most especially that it is bound to be exposed outdoor while actively collecting heat energy from the sun the entire time. Thus, an effective cooling feature will be of great benefit to help maintain an acceptable level of thermoregulation within the device.

  1. Warranties & Services

As an integral part of your security as a customer, it is imperative that you are aware of the scope of the warranty and services included with your inverter. Some manufacturers may not exactly provide a detailed and accurate description. Thus, for your own safety, it is ideal to thoroughly examine the terms and conditions encompassing the warranty of the product to assure that it is within your favor. 

How to maintain solar energy inverters?

Similar to solar panels, inverters are built with minimal maintenance requirements. However, unlike the PV modules, the inverters are far more technical in nature and are composed of electrical components that can likely post hazard if managed incorrectly. Given the situation, it is wiser to appoint this task to trained professionals instead. Here are few of the things to look into when caring for your solar inverters:

  • Dirt – Dirt and other dust particles can potentially create new conduction pathways on the circuit board which can eventually lead to damage or circuit failure if not removed accordingly.
  • Heat – Just like other electronic devices, an inverter also needs a fan or any form of cooling system to help tone down the heat from within.
  • Humidity – Humidity itself increases the risk for corrosion of the electrical terminals and connectors. Thus, it is important to monitor it periodically because once corrosion sets in, it is very difficult already to halt its progress.
  • Annual Check-up – A yearly preventive maintenance typically includes a full inspection, thorough cleaning, tightening of any loosened components, replacement of damaged parts, and as well as the analysis of the performance.

The solar energy inverter is an integral element of the solar power system. Its main role in converting the direct current (DC) electricity into a usable alternating current (AC) power is vital in the overall function of the photovoltaic system. That is the reason why it is often regarded as the “brain”. Hence, it is necessary that users should acquire the right kind of inverter in order to optimize the generation and transmission of a cleaner and greener renewable electricity to homes and establishments both on-grid and even in the remote setting.