The Solar Power Inverter for Grid Connected PV Systems
As we already know, photovoltaic solar cells produce continuous DC (direct current) power and therefore when a photovoltaic solar system is required to connect directly to the mains electricity grid or contains an AC (alternating current) load, a DC to AC conversion of the electrical power is required. The Solar Power Inverter provides that DC to AC conversion using electronic switching techniques.
The Solar Power Inverter is an important electronic device that converts the electrical power generated by the PV solar array into a clean AC power supply suitable for feeding directly into the power grid. The typical application of a single solar power inverter is to convert the low input voltage into a higher conventional household AC mains power supply of the correct frequency and voltage, allowing us to use electrical appliances when an AC mains electricity supply is not available.
Solar Power Inverter Symbol
In practical terms, the inverter allows us to run electric drills, computers, vacuum cleaners, mains lighting, and most electrical appliances that can be plugged into the wall sockets. If the power inverter is big enough, then larger appliances such as freezers, refrigerators, and washing machines can also be used.
All of these standard 120 or 240 volt AC appliances can be powered directly from either the PV solar array, or by converting the power stored in backup batteries using the appropriately sized solar power inverter. An inverter’s operation is generally quiet with its output power available whenever it is needed. Therefore, stand alone battery systems can run just about any standard commercial appliance, 24 hours a day.
While a single inverter may well be sufficient for a domestic installation, multiple units become the norm as we advance up the power scale and their efficiency, reliability, and safety are major concerns of the system designer.
Solar Power Inverter Configurations
Central Inverter Configuration
Central Inverter Configuration – Several branches of the array are connected together in parallel. The complete output of the array is converted to AC through a single central solar power inverter and then fed to the grid. The single inverter is presented with a DC input voltage and current which may be quite large depending upon the configuration of the array.
This type of inverter configuration gives good efficiency, low cost, average reliability and since the PV panels within the same array are evenly matched, the maximum power point tracking (MPPT) selected by the inverter for the whole array ensures that all the PV panels operate at, or close too, their maximum power output.
Branch Inverter Configuration
Branch Inverter Configuration – Each branch or string has its own inverter attached. Then each single branch can have a different number of PV panels, different panel types, positions, orientations or suffer from full or partial shading. The result is that each inverter produces a different power output relative to its connected array.
Therefore the array cannot be efficiently characterised by one single maximum power point (MPP), as each inverter will operate at a different maximum power point with respect to the others. The main advantage of this type of power inverter configuration is that each solar branch can be at a different location or position and not all together in one single array.
Individual Inverter Configuration
Individual Inverter Configuration – Each photovoltaic solar panel has its own power inverter. This enables the inverter to select the optimum power point for the panel giving very good efficiency but at a higher cost per kWp. components in the array means lower reliability and more maintenance.
An increasing number of solar panel manufacturers are offering individual PV panels with solar power inverters built directly into the PV panel, making each solar panel its own complete AC power source allowing it to be plugged directly into the mains grid.
Grid connected solar power inverters synchronise the electricity they produce with the local grids AC grade electricity, allowing the system to feed the solar made electricity directly into the grid, usually through a second electricity kWh “net” meter.
Most grid connected power inverters are designed to operate without backup batteries, but battery based inverter models also are available. The battery based inverters for use in both a stand alone PV system or a grid connected PV system. As modern day power inverters include an inbuilt battery charger, which is capable of charging a battery bank directly from the grid during cloudy or bad weather.
High quality solar power inverters are available in sizes from a few 100 watts, for powering lights, laptops and games consoles from your car, up to tens of kilowatts, for powering large residential solar system with grid connected inverters being designed to automatically shut down when there is no grid power available for safety reasons.
Solar inverters are available in a wide range of power sizes and voltage ratings to suit just about every combinations of installation but there are basically three kinds of DC to AC solar power inverter: square wave, modified sine wave, and pure sine wave.
Square Wave Solar Power Inverter
The Square Wave Solar Power Inverter is the simplest and the least expensive type of inverter available. It is generally not used commercially due to its low quality of output power and very large harmonics. Square wave inverters equipped with thyristor output stages chop and invert (hence the name Inverter) the DC input positive power to generate a square wave alternating positive to negative AC output signal that is later filtered to approximate a sine wave and eliminate undesired harmonics.
Cheaper square wave inverters may also use push-pull transistor circuits with step-up transformers to produce the required output voltage. Square wave inverters are really only used in small stand alone PV systems that will run simple things like lighting or hand tools with universal motors with no problem – but not much else.
Modified Sine Wave Solar Power Inverter
The Modified Sine Wave Solar Power Inverter also called a quasi-sine wave inverter, is basically a modified square wave inverter which produces a square wave output with low harmonic distortion and a small “OFF” time between the positive and negative half cycles as the inverter switches polarity.
Modified sine wave inverters are suitable for most types of electrical and electronic loads, and are a popular type of inverter on the consumer market today due to their good conversion efficiency, relatively low cost, and can be used in solar installations where waveform shape is not too important.
However, modified sine wave inverters may not allow printers, copiers, light dimmers, rechargeable and variable tools to operate correctly due to the switching action of the inverters output stage. Also some audio amplifiers and radios may produce a low frequency background buzz due to the inverters output switching components.
Sine Wave Solar Power Inverter
The Sine Wave Solar Power Inverter produces a high quality AC voltage waveform with low total harmonic distortion (THD) similar to what you get from your local electricity or utility company. They are used when there is a need for clean sine wave outputs to operate sensitive devices such as electronic equipment, printers, copiers, and stereos, etc.
Pure or true sine wave power inverters are required as standard by most electrical utility companies as part of a grid connected PV solar system. Sine wave inverters have a much higher cost than the previous types for the same wattage due mainly to their better internal electronic circuits. Their output voltage can be controlled either in square wave mode or in pulse width modulated (PWM) mode.
In PWM pure sine wave circuits, the output voltage and frequency are controlled by varying the duty cycle of the high frequency pulses. Chopped voltage then passes through an output LC low pass filter network to produce a clean sinusoidal output.
This allows the output voltage and frequency to be well controlled, ensuring that any AC load within the inverters power limits will operate properly. Pure sine wave inverters are generally not suitable for home solar power as their cost is too expensive and are inefficient, instead “stepped” sine wave inverters are used.
Only the top end high quality inverters actually supply a pure sine wave as their output waveform. Also some of the higher end pure sine wave inverters have solar tracking circuits or maximum power point tracking (MPPT) built-in, in order to optimally operate a motorised solar tracking PV array.
Most sine wave models available on the market produce a variation on the modified sine wave inverter above. Their voltage output is not a pure sinusoid but they can operate almost anything that can be connected to the local grid. When it comes to efficiency, sine wave inverters perform better than pure sinusoidal inverters.
Solar Power Inverter Selection
After the solar PV panels themselves, Solar Power Inverters are the next most important part of a grid connected PV system and therefore the DC input power rating of the inverter should be selected to match the PV panel or array.
Generally, power inverters are selected for a particular solar system based on the maximum load, the maximum surge required, AC output voltage required, input battery voltage and any optional features needed. The size of an inverter is measured by its maximum continuous output in watts and this rating must be larger than the total wattage of all of the AC loads connected at the same time.
Also electrical appliances such as washing machines, dries, fridge’s and freezers which use electric motors require more power to start themselves than they require to run.
This high starting power consumption can be more than twice the normal power consumption so this must be considered when sizing an inverters wattage. Most power inverters are capable of delivering three to five times their rated wattage for short term surges and overload conditions.
Lets assume that we have calculated the total AC power consumption of our home and that we would need a 2500W or 2.5kW solar inverter. The PV solar panels we are interested in are 24 volt monocrystalline silicon panels rated at 140 Watts peak. Then dividing 2500W by 140 watts means that 18 PV panels will be needed, yielding 2520 watts in total.
But how do we connect these 18 panels to the inverter. We know from previous tutorials that PV solar panels can be connected together just like batteries, and in a series combination the voltage adds, with a constant current through each panel, and in a parallel combination the current adds with a constant voltage across each panel.
We first need to calculate how many modules can be connected together in a series branch. The datasheet for our inverter tells us that the maximum power point tracking (MPPT) input voltage is between 175 and 480 volts at a maximum current of 15 amps. The open circuit voltage ( Voc ) of each 24 volt PV panel at 25 o C is given as 36.8 Volts.
Then we can see that the maximum number of panels we can connect together in a single series branch is calculated as: 480/36.8 = 13 panels. Likewise, the minimum number of 24 volt PV panels required to keep the MPPT tracking voltage above the minimum 175 volts is there calculated as: 175/24 = 7.3, or 8 panels.
Then to keep within the inverters input voltage limits for our simple example so that the PV array voltage is not lower than 175V or greater than 480V requires an array branch of between 8 and 13 solar PV panels. Since our calculated array consists of 18 panels, two branches or strings of 9, 24 volt PV panels each is acceptable. The short circuit current, Isc of our 24 volt monocrystalline silicon panels is given as 5.8 amps. Two branches will therefore give a total maximum current of 11.6 amps, well within the inverters specification.
So to determine the number of panels that can be connected on one series PV branch, check that the sum of the open circuit voltage of all the panels does not exceed the maximum power point tracking DC input voltage and that the minimum number of panels in the series branch does not fall below the minimum MPPT voltage not forgetting that the voltage in a series branch varies up and down with temperature. Also check that the short circuit current ( Isc ) of the array is less than the maximum DC input current of the power inverter.
In the next tutorial about Solar Power, we will look at the advantage of using Deep Cycle Batteries compared to normal automotive batteries and how to connect them into our home solar power system for use in a stand alone or grid tied PV system.
How Do You Build a Home Battery Backup System?
If you don’t have a home backup power system, you and your family can be vulnerable during a blackout.
You can keep a traditional fossil fuel generator on standby for a power outage. But gas and diesel generators guzzle fuel, produce toxic emissions, and are extremely noisy — not to mention terrible for our planet.
What’s a more eco-friendly alternative?
If you have a knack for DIY projects, you can build your own home battery backup system from scratch. The process requires care, attention to detail, and numerous essential components.
Once you know how to do it, building a home battery backup system can be rewarding and cost-effective.
Check out the step-by-step instructions and see if a DIY home battery backup system is a good fit for you.
If it all seems a bit much, we’ll also explore plug-and-play portable power station options, which are also an excellent alternative to traditional generators.
What Do You Need To Build a Home Battery Backup System?
The United States and the world are experiencing more power outages due to extreme weather. The frequency of blackouts means that it’s no longer just a convenience to have a home backup power solution, but a necessity.
Building a home battery backup system requires more than just a battery and some wires. You need to connect the battery to your electrical panel and ensure compatibility between all system components.
Still, the DIY process doesn’t have to be too complicated. It’s a relatively approachable project for a handyperson with basic electrical knowledge and skills.
To build an effective home battery backup system, you’ll require the following components:
- A power inverter
- Home backup battery
- Battery charger
- Wiring and cables
Choose a Power Inverter
Your home appliances use alternating current (AC) electricity to run. Unfortunately, batteries generate direct current (DC).
You can’t just connect a battery directly to your home circuit board or your appliances. You need to convert the battery power into AC — commonly known as household electricity.
The device that converts DC power to AC electricity is called an inverter.
When choosing an inverter, the first step is determining how much power output you need to produce. An inverter will carry a rating in watts, but unless you know the consumption required by the appliances and systems you want to run during a blackout, the wattage of the inverter is somewhat meaningless.
To determine your household energy consumption, add the wattage of each device and appliance you want to power or charge during an outage. For example, a 2000-watt inverter can only provide electricity simultaneously to appliances with a combined wattage of 2000W or less.
It’s also crucial to keep in mind that many appliances require a higher wattage to turn on than to operate. This is commonly referred to as surge power or starting watts. Make sure your inverter’s output capacity is sufficient to turn your appliances on, not just keep them running.
For your reference, here’s a table showing the average wattage of common home appliances.
Starting and Running Watts of Typical Household Appliances
|Rated (Running) Watts
|20” Box Fan
Choose Your Battery
Next, you need to choose your battery. You will probably need multiple batteries for a whole house backup power supply.
Battery capacities can range from small, 100Wh batteries to larger, 3.6kWh batteries sufficient to power large appliances. To find out how much power output and storage capacity you need, determine the wattage requirements of the appliances or devices you want to power, then multiply that number by the amount of time you want to be able to run it.
For example, running a 300-watt laptop for six hours would require a battery with a minimum power output of 300W and a storage capacity of 1800 watt hours (1.8 kWh).
If possible, select batteries that reach at least double the storage capacity you need so that you can keep them from discharging below 50% capacity.
Depending on the battery chemistry, “deep discharging” can negatively impact lifespan and performance.
Below are some examples of plug-and-play portable power station battery backup options:
- RIVER 2 Pro Portable Power Station—A step up from the RIVER 2, the RIVER 2 Pro supplies home backup for personal devices and small appliances. With 768Wh capacity and a 30ms switch-over mode, it’s an ideal battery backup station for uninterrupted power for up to 80% of high-wattage home appliances, such as microwaves and electric kettles.
- DELTA 2 Portable Power Station—The DELTA 2 power station delivers 1024Wh capacity. You can run several appliances and keep your essentials running during an outage.
- DELTA Pro Portable Power Station—The Delta Pro can run major appliances and heating/cooling systems with a 3.6 kWh power output capacity (expandable to 7.2 kWh/240V). You can connect extra Smart batteries and expand the storage capacity to 21.6 kWh for a whole home power backup solution that can run for up to a week.
Choose a Battery Charger
Next, you need a component to charge the batteries. A charger and a regulator can recharge your batteries without overcharging them. Make sure your charger is compatible with the batteries you use, as this will prevent damage to the batteries.
If you consistently drain or overcharge your batteries, you risk permanent damage and diminished efficiency. Measuring and regulating the charge your batteries receive allows you to keep them at their maximum capacity and maximum efficiency between uses.
In a blackout, a fully charged battery will supply you with power for longer periods.
If you’re building a solar home backup system to ensure an off-grid energy supply, you’ll need to purchase solar panels and balance of system components. Make sure the solar panels and battery are compatible.
Options like EcoFlow solar panels are universally compatible, but not all photovoltaic panels are. Unless you buy a plug-and-play solar generator, you’ll also need to ensure the compatibility of the inverter, charge controller, and other balance of system components.
Connect Your System
Finally, you need to wire your components together. Connect your battery to the inverter, charge controller, and charging source. Next, connect your home battery backup system to your home’s existing wiring using a transfer switch (or power input if available).
Once everything is hooked up, your home electrical system should draw from the backup battery the next time a power outage occurs.
Mistakes to Avoid When Building a Home Battery Backup System
If you purchase individual components for your battery backup system, you need to ensure those parts are compatible. If you don’t, your battery system will fail before you can even use it.
Similarly, you need to buy quality components. Many people choose the DIY route to save money. However, avoid skimping on the quality of your parts.
The right components will keep your home battery backup system reliable for a much longer time.
Mistake #1: Choosing the Wrong Battery Chemistry
Here are the common backup battery chemistry types in order of efficiency (from best to worst)
- Lithium Iron Phosphate (LFP or LiFePO4) Batteries
- Lithium Ion (Li-ion) Batteries
- Nickel Cadmium (Ni-Cad) Batteries
- Lead Acid Batteries
Unfortunately, the more efficient the battery chemistry, the more expensive the battery is likely to be. Don’t make the mistake of only considering upfront costs, though. Lead acid batteries will quickly need to be replaced — LiFePO4 batteries can last a decade or more.
Mistake #2 Underestimating Your Energy Consumption
If you’re building a battery system to meet your backup power requirements, make sure you’re accurate about how much electricity you need to consume during a blackout.
A system built to power your highest-wattage appliance is great if that appliance is all you want to run. If not, you need to make sure you account for all the other appliances and devices you want to run or charge simultaneously.
Add the wattage of all those devices together (don’t forget surge power or starting watts if needed). Aim to exceed your estimated power output and storage requirements by at least 20%, just to be on the safe side.
Mistake #3 Connecting Your Backup Battery to Your Home Wiring System Yourself
Unless you’re experienced at working with high voltage electrical wiring, hire a professional electrician.
Installing a transfer switch to connect your backup battery to your home circuit panel is a fast and easy job for a professional. If you try to DIY, you could electrocute yourself or create a fire hazard that you may not even know about until it’s too late.
Alternative Home Battery Backup Solutions
Building a home backup battery system involves numerous steps and selecting multiple compatible components.
There’s a lot of room for error.
Alternatively, you can purchase a plug-and-play solution.
EcoFlow offers solutions to back up and power your entire home in a blackout. Or you can go completely off-grid with solar panels to achieve energy independence:
Whole Home Backup Power Solution: The EcoFlow advanced whole home backup power solution consists of two DELTA Pro Portable Power Stations connected via the EcoFlow Double Voltage Hub. By chaining two DELTA Pros together, you can achieve 7.2kWh of power output. Connect up to four Smart extra batteries, and you can have up to 21.6 kWh of battery storage — which will last many homes up to a week. Connecting the whole home backup power solution to your home circuit panel creates a built-in backup system that can switch on instantly during a blackout and meet all your power demands.
Also, don’t forget, all of EcoFlow’s portable power stations — including the DELTA Pro — can recharge using solar panels. Turn your backup battery into a solar generator with one simple connection.
Your home is at risk of power outages at any time. A backup power supply is the best safeguard against energy vulnerability.
EcoFlow has the products and the expertise you need to keep your appliances running and your lights on — even during an extended power outage.
Reach out today for help with your home backup power needs.
EcoFlow is a portable power and renewable energy solutions company. Since its founding in 2017, EcoFlow has provided peace-of-mind power to customers in over 85 markets through its DELTA and RIVER product lines of portable power stations and eco-friendly accessories.
Solar Inverters: Types, Pros and Cons
Solar energy doesn’t provide electricity in a format that your table lamp could be powered by. Inverters change the power produced by your solar panels into something you can actually use.
Think of it as a currency exchange for your power. You might have a fistful of yen, but until you stop and exchange it for USD, you can’t pay for lunch stateside.
Your home is wired to conduct alternating current (AC) power. The electricity produced by solar panels is initially a direct current (DC). Inverters change the raw DC power into AC power so your lamp can use it to light up the room.
Inverters are incredibly important pieces of equipment in a rooftop solar system. There are three options available: string inverters, microinverters, and power optimizers.
Team up with an Energy Advisor to see which inverter is best for your solar project
Solar Inverter Types, Pros and Cons
String inverters have one centralized inverter — or, keeping with the metaphor — one central currency exchange station.
This is a standard inverter, and it works just fine if you don’t have any encroaching shade from nearby trees or a big chimney. It’s also great if you have all of your solar panels facing the same direction.
String inverters are standard in the industry, and they’re the least expensive.
String inverter cons:
- Overall production decreases if one panel is damaged or shaded
- No ability to monitor each panel individually
- Not optimal if your solar panels are facing different ways
- Increasing power needs are more difficult and may require second central inverter installation
Microinverters are small units built into each individual solar panel that convert power. Think of it as having mini currency exchange stations on every nearby street corner.
This gives each panel the ability to function at peak performance, independent from its neighbors. Even if the panel next to it has a tree branch shading it for most of the day, all the other panels can convert at full capacity. Any drop in efficiency only affects one panel.
Microinverters also enable you to monitor the performance of each individual panel. This is helpful for spotting any issues with a single panel so you can have it repaired before it slows down the whole system’s productivity.
This type of inverter can be more expensive than string inverters, but it can pay off over time by getting more power from your system overall.
Microinverters also make it easy to increase power usage if you want to. Say you buy an electric car and you’ll need more power to charge it every night. Adding more solar panels and inverters is easier and less expensive than adding an additional central inverter for a string inverter system.
- Shade from a nearby tree won’t reduce the whole solar panel system power output
- Individual panel monitoring available
- Increasing power needs are easier and less expensive than installing a second central inverter
- Good for rooftops where solar panels may face different directions
Power optimizers are somewhere in between string inverters and micro-inverters both in how they function and in price.
As with micro-inverters, power optimizers have a component (the “optimizer”) underneath and within each solar panel. But rather than change the DC to AC right there on site, these inverters optimize the current before sending it to one central inverter.
This is more efficient than a string inverter, as any sluggish production from one panel doesn’t slow the whole system, but more cost-efficient than a standard micro-inverter setup.
Imagine being able to cut to the front of the line at the currency exchange office. It’s not quite as quick or convenient as having your own exchange office a few steps from your home, but there’s no waiting around once you get to the central office.
Micro-inverters and power optimizers are gaining popularity and are dropping as the technology advances.
We have more details on power optimizers in this post.
Power optimizer pros:
- efficient than string inverters
- Less expensive than micro-inverters
- Individual panel monitoring available
Power optimizer cons:
Ultimately, best inverter for you depends on your roof shape and size, nearby trees, how much energy you need, and your budget.
What to Look for in a Solar Inverter
To recap, there are three kinds of inverters: string inverters, microinverters, and power optimizers.
They all transform the power your solar panels generate from direct current (DC) to alternating current (AC). This makes the energy usable for your home.
Here’s a few things to look for when shopping for inverters…
Solar Inverter Warranties
Most people feel more comfortable purchasing electronic devices with warranties. Solar inverters are no exception. Most inverters have warranties ranging from anywhere between 5 and 10 years, though some can be extended to 25 years.
When you’re looking at a company, make sure you know what’s included in the warranty and what’s not. For example, some power optimizers might not include the central inverter under the warranty.
Also make sure you understand the terms of a warranty. Is the device covered in case of an internal glitch as well as in the case of external damage? Will you be charged for labor or shipping if you have to send parts in? These are all important questions to ask.
Solar Inverter Operating Temperatures
As with most electronic equipment, inverters operate best when they’re running cool. Operating temperature is the safest temperature range an inverter maintains.
Inverters will naturally generate some heat themselves as they do their job. Since they’re typically in an uncontrollable environment outdoors, they’re exposed to a wide range of temperature fluctuations.
Obviously, conditions aren’t always ideal and some times an inverter will have to work harder than others. The higher the operating temperature (the more heat it can handle), the better.
Solar Inverter Efficiency
There are two numbers to look for in solar inverter efficiency: peak efficiency and weighted efficiency.
Peak efficiency will give you the efficiency of your inverter when it’s running optimally. It’s good to know what the best-case scenario is, but it’s also worth noting that it won’t always be hitting that level. Some days it might only reach peak efficiency for an hour or two, or maybe not at all.
Weighted efficiency figures in the variables like DC input levels. This gives a more accurate gauge as sunshine, temperature, and other environmental elements affect inverter efficiency throughout the day.
Solar Inverter Key Terms to Know
This is the term used to describe the energy output that is lost due to undersizing an inverter.
Any given inverter has a maximum power rating (at the residential level, measured in W or kW). When solar supplies DC power in excess of that inverter’s maximum power rating (what the inverter can handle), the resulting power is “clipped.” Think of it like a 14 foot tall truck trying to go under a 13 foot bridge — a little comes off the top.
It’s important to consider the solar panel arrays’ maximum power output and select an inverter with the correct size, model, and type in order to avoid excessive clipping.
It’s normal for the DC system size to be about 1.2x greater than the inverter system’s max AC power rating. For example, a 12 kW solar PV array paired with a 10 kW inverter is said to have a DC:AC ratio — or “Inverter Load Ratio” — of 1.2.
When you into account real-world, site-specific conditions that affect power output, it may make sense to size the solar array a bit larger than the inverter’s max power rating, as there may be very few “power-limiting days,” or instances of clipping for that system.
Inverter efficiency is a percentage that tells us how much DC power input to an inverter comes out as usable AC power.
No inverter is 100% efficient, although some come close in favorable conditions. In the conversion from DC to AC, power is lost in the form of heat.
While inverter efficiency is an important factor to consider in the selection process, there are other factors to consider that also affect a project’s economics, such as warranty, price, expected life, serviceability, and monitoring functions.
Maximum power is the highest amount of power allowed to feed into an inverter, which is a function of the inverter’s specifications or the maximum power a solar panel can produce. This will occur at the optimal trade-off between voltage and current along a given panel’s I-V (current and voltage) curve.
Maximum Power Point (MPP)
A solar system’s maximum power output will vary with conditions, such as how much sunlight it receives, temperature, and other factors. A fixed-tilt, stationary, roof or ground-mounted solar PV system might only produce its maximum rated power during a limited period of the day. Every specific solar cell has its own unique I-V curve, which relates its maximum power output to variations in current (I) and voltage (V).
Maximum Power Point Tracker (MPPT)
A device that periodically tracks characteristics of a given panel, string of panels, or system, and optimizes and varies voltage and amperage accordingly in order to produce maximum power.
A device that converts direct current (DC) produced by a single solar panel into alternating current (AC).
Micro-inverters are commonly connected to and installed at the site of, or behind, each individual solar panel in an array. Most micro-inverter makes are installed in the field, while some come panel-integrated by the manufacturer.
Popular brands of micro-inverters include: Enphase, Chilicon, APS, ABB, SMA, and SunPower.
A DC-DC converter, optimizer, or “panel optimizer,” is a module-level power electronic device that increases the solar system’s energy output by constantly measuring the MPPT of each individual panel.
The panel optimizers relay performance characteristics via a monitoring system to facilitate operations and any necessary maintenance. In essence, optimizers support flexible system designs and arrangements – with multiple panel orientations, tilts, azimuths, and module types in a given string.
Because optimizers are a DC-DC, or DC-coupled, systems using this technology will generally be compatible with DC-coupled energy storage or battery backup solutions, like the Tesla Powerwall.
Perhaps the most advantageous benefit of using a DC optimizer is panel-level MPPT, or max-power point tracking. The result is increased energy harvest from a panel system, especially when subject to periodic or sweeping shade.
Peak Power Point
Another term for Maximum Power Point (MPP).
The device that converts direct current (DC) electricity produced by groups of solar panels (called strings), into usable alternating current (AC) electricity.
String inverters are considered a “mature” solar technology that has proved effective, safe, and reliable. Residential, 240V AC string inverters usually carry manufacturer’s warranties of about 10 years.
When installed to a manufacturer’s specifications, code, and best practices, a string inverter may require service or ultimately replacement during a photovoltaic system’s lifespan.
Team up with a solar.com Energy Advisor to understand what is covered by your solar system’s workmanship warranty, as well as the inverter manufacturer’s warranty. Depending on what one’s goals, budget, and preferences are, string inverters can be a great option for your solar PV system.
4 Cool New Technologies from Solar Power International (SPI) 2019
Our team just returned from a very exciting trip to the Solar Power International 2019 Convention in Salt Lake City, Utah. We toured the floor.
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Microinverter vs String Inverter: Which is Right For Your Solar System?
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What is a Power Optimizer?
When deciding on solar equipment it’s important to know what options are available. Different equipment suits different situations better. A power optimizer is ideal.
What Kind of Inverter Does My Solar Panel System Need?
Electricity produced by your solar panels and left in your battery storage is useless without the proper equipment to harness all that energy. A solar panel system requires a method to transport and convert stored electricity into your home safely and efficiently.
Inverters are crucial to set up your solar panel system, and getting the right one can be a bit confusing without some help. This guide will introduce you to everything an inverter does, how it works, and, most importantly, how to choose one for your unique situation.
WHAT IS AN INVERTER?
The most basic function of an inverter is to turn DC (Direct Current) into AC (Alternating Current).
Home appliances can’t use electricity from your battery storage without converting it into AC. Since batteries and solar panels require a DC to work, inverters are mandatory for any solar panel system to function correctly.
Solar panel inverters also act as a safety net for your system. If it senses something in the chain is amiss, it turns off. This protects your home in case of electrical problems, malfunctions, and so on.
Setting up safety features such as fuses, insulation, and breakers are still required for your system. But, of course, the more safety features to fall back on, the better!
HOW DO INVERTERS WORK?
To understand how inverters function, we first need to learn how electricity generates and moves in a solar panel system.
A Direct Current simply means the electricity flows in one direction. Solar panels and batteries use DC because electricity or electrons flow in one way and then out another. Since electricity is coming from one main direction (the sun), you can’t have a solar panel with an Alternating Current.
An Alternating Current means the electricity quickly reverses direction back and forth. It switches directions about 60 times per second, more or less depending on the inverter. Home appliances and the grid use AC because of how easy it is to transport from location to location. It is also notably easier to shift the voltage for an AC than it is for a DC. DC requires bigger wires and more insulation, which means more potentially wasted electricity.
An inverter simply takes the Direct Current and makes it act like an Alternating Current by switching the flow back and forth as fast as possible. Every inverter does this at different speeds and steadiness. The more advanced the inverter, the better job it does at converting the current back and forth.
WHAT TYPES OF INVERTERS ARE THERE?
There are tons of solar panel inverters on the market, all made for various devices and situations. Still, the main selection for solar panel systems comes down to two different kinds of inverters: modified sine wave and pure sine wave.
WHAT’S THE DIFFERENCE?
A modified sine wave inverter switches the current as if turning on and off a light switch: it’s very abrupt. Pure sine wave inverters switch between the two directions smoothly (but still very quickly!) and make the conversion more akin to a sine wave, hence the name.
WHICH INVERTER IS BEST?
Well, that depends on what you need.
A modified sine wave inverter is a cheaper and less efficient version of an inverter. It works best with more basic appliances, mainly those without a running AC motor or more advanced electronic components. Devices such as tube TV’s, vacuum cleaners, and water pumps will work fine but will likely use a bit more electricity.
The more complex the appliances, though, the less likely they will function properly, or even at all. Devices not suited for the modified sine wave inverter will make a buzzing noise, generating more heat than normal. But if you need a cheap inverter to work basic home appliances, then a modified sine inverter will get the job done.
On the other hand, a pure sine wave inverter is a more expensive, but far more efficient, version of an inverter. It works with most home appliances and helps them run as cleanly as possible.
If you’re planning on running sensitive hospital equipment, microwaves, more advanced TVs, or anything with an AC motor, you need to have a pure sine wave inverter.
WHAT INVERTER SIZE SHOULD I GET?
Solar panel inverters come in different sizes, depending on how much electricity they can intake and output at a time. Knowing which size is right for you depends entirely on how much electricity you will be using throughout the day and how much storage you plan on having.
Consider what home appliances you own. You need to account for everything in your initial estimation, even something as small and mundane as a digital clock.
Another factor to consider is how often you will be using these devices. Ask yourself what you need from day to day.
- How often do you use the microwave?
- Do you watch TV every day? How long?
- How long do you have your phone or laptop plugged into the charger?
- Will you be running a device all day or just an hour?
- Are you using several appliances at the same time?
- Will you switch between plugging in different devices?
These are the types of questions you must ask yourself.
You must have solar panels and battery storage large enough to handle everything you are considering using each day. That’s why estimating is so essential: it impacts every decision when planning out your solar equipment selection.
That’s also why it’s safer to get a size bigger than you think you need. Being able to use electricity whenever you want or need requires a bit of spontaneity.
You never know when you’ll get more electronics added to your home. So, getting a bigger inverter to start with will save you the trouble of getting a new one later on.
If you’re struggling to figure out calculations, you can use our solar calculator here. You can also reference our blog on solar calculation here. Our blog goes into more detail on how to work out the math and helps the planning process!
WHAT OTHER INVERTER FEATURES SHOULD I CONSIDER?
Every inverter has different strengths and drawbacks. Make sure you consider what aspects are most important to you and your situation.
For example, some inverters are easier to set up than others. If you are doing a lot of the work yourself, easy installation options might suit you best!
If you live in a state with harsher weather conditions, you must consider how durable the inverters are. Look up an inverter’s NEMA rating, or check reviews, to see which can handle constant rain, harsh sunshine, strong winds, or any weather you deal with constantly.
Efficiency comes back to using modified or pure sine wave inverters.
Of course, the more features you have, the more expensive it can end up becoming. Costs can range wildly, but generally, the more you spend, the more features and valuable qualities you’ll have included.
That’s not to say you should throw all your money at the biggest and most powerful inverters. You don’t want one that’s too big or doesn’t have a chance to use the advanced features it may have.
Consider what is crucial for you and your situation, then select an inverter accordingly.
DOES BEING ON OR OFF THE GRID MATTER?
There are a few key differences to be aware of when going on or off the grid, so be wary!
Solar panel inverters on the grid are easier to set up since you don’t need a battery bank. Not to mention, putting the electricity you produce onto the grid will be shaving tons of money off your electricity bill without worrying about battery life and what time of day you use your electronics.
However, being on the grid means power outages will affect you since the inverter shuts off for safety reasons. You’ll also not be completely self-reliant since your home will still connect to the grid. That’s not necessarily a bad thing. But, it’s much more tempting to use electricity if you’re not worried about battery storage and whatnot.
Inverters off the grid take a bit more to set up and require more planning. You need to consider your battery bank and how much electricity you can run during the day and night.
However, being completely self-reliant means you don’t have to worry about electricity bills or power outages on the grid in case of emergencies. It’ll be work, but you will have complete control and save a lot of money.
Lately, there have been hybrid setups with both an emergency battery bank and a connection to the grid. However, you will need to recognize this will cost more initially and require more planning. Despite this, finding a middle ground between both can be beneficial for those interested.
WHAT IF I’M STILL NOT CERTAIN?
Many factors go into selecting an inverter for your home. Being overwhelmed is shared with anyone looking to set up their solar panel system. Luckily, we have a lot of experience helping customers pick out whatever equipment they may need, inverters being no exception!
Please check out our website for various product selections, or contact us with any questions you might have. Are you looking to learn more about anything and everything solar? Check out our blogs and learn from the experts about the benefits and experiences of going solar.