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Comparing Inverter Technologies
Apr21

Comparing Inverter Technologies

The decision to install solar is a simple one. It will save you money so you should do it. Solar panels require an inverter to convert the DC power that they produce to AC power that your appliances need. So you know an inverter (or inverters) needs to be part of your solar package, but navigating the options on what type of inverter technology is right for you can be little more complex.  The basic options are microinverters, string inverters, string inverters that require optimizers and battery-based inverters.  Microinverters are installed at the solar panels. They will mount to the solar panel frame or the racking depending on what racking you are using. There is typically one microinverter for every one or two solar panels. The most popular brand for microinverters is Enphase who pioneered the concept of microinverters many years ago. String inverters are very different than microinverters. They are installed separately from the solar panels and one string inverter can handle many solar panels. How many solar panels can go on a string inverter depends on the size of a the string inverter and the wattage of the solar panels. The residential string inverters usually max out at about forty solar panels while a larger commercial inverter could handle hundreds of solar panels. Inverters designed for utility scale solar farms can even handle thousands of solar panels but that is probably a little bigger than you are looking for here. The name “string inverter” comes from the fact that the solar panels are wired together in series strings. Some string inverters require DC optimizers be installed at the solar panels. One or two solar panels connect to each optimizer and then the optimizers are connected together in a string.  It used to be that only SolarEdge inverters needed to have optimizers in installed, but the new NEC 2017 requirements for rapid shutdown has changed the rules for all string inverters. If the system is installed on a building, there need to be rapid shutdown devices that can de-energize the system at the module level. These may not be as complex as the SolarEdge optimizers which do maximum power point tracking for each solar panel but at the very list they have to be a switch that can turn off the DC power for each solar panel. Finally, there are the battery-based inverters which get their power input from batteries instead of solar panels. If you are installing a battery-based inverter as part of your solar power system, you would need to install charge controllers to manage the power from the solar panels going into the batteries and...

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What Is the Difference Between Grid Tie and Off Grid Solar?
Mar30

What Is the Difference Between Grid Tie and Off Grid Solar?

There are two basic types of solar power systems – grid tie and off grid. The simple explanation of the difference between them is that grid tie systems connect to the grid and off grid systems don’t connect to the grid. Whether or not they connect to the grid makes a big difference in how they are designed. First let’s define what we mean by “grid”. The grid is the utility company’s network of conductors and equipment that bring electricity from the power plant where it is made to the end user’s home or commercial building. If a building is getting electricity from the electric company, it is connected to the grid. So what makes a grid tie system different from an off grid system is that the grid tie system must interact with the grid and there are some requirements and some advantages to this interaction. First, a grid tie inverter must sync up exactly with the grid. Its AC output wave must be exactly in time with the AC wave that the grid is delivering to the building. It also means that you must choose the correct grid tie inverter based on how the power is delivered to your building. A typical home receives 120/240 Volt Single phase (aka split phase) power so the solar power system would have to use a single phase inverter. Commercial buildings are usually three phase power which is typically 120/208 Volt or 277/480 Volt and could be wye or delta configuration. It must be determined exactly what type of power is being delivered to the building so that you can choose the correct grid tie inverter.  The other big requirement for a grid connected system is that it can not feed power to the grid when the grid goes down. The reason for this is that the utility workers are trying to troubleshoot and correct the problem and if there are a bunch of solar power systems still feeding into the grid, it would be dangerous and it would affect the measurements the workers are making as they try to determine what is wrong and fix it. One of the advantages to a grid tied solar system is that they can rely on the grid to provide power when the solar isn’t producing enough. This means the solar does not need batteries and the building never goes without power. In an off grid system, there is no grid to provide power so if you want power at night, you have to have stored enough power during the day. This means that off grid systems have to be much larger because the...

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DIY Mishap – When Home Installers Throw Caution To The Wind
Mar16

DIY Mishap – When Home Installers Throw Caution To The Wind

When it comes to DIY home solar installations, some rules are meant to be broken, while others are better to follow. Paying a centralized utility company for energy you can make for free: Break it!Best-practice safety protocols during self-install: Follow it! Devaluing your home property value by not putting solar panels on your roof: Break it! Local zoning and city ordinances: Follow it! The laws of physics: Follow it! Okay, the last might seem like a no-brainer.  “The laws of physics,” after all, are those immutable truths about reality which, unlike the tooth fairy or a wizarding world living in tandem with our own, exist whether or not you believe in them.  The laws of physics are why, in more 14 years of business, the DIY department of Go Green Solar has never had a customer encounter an issue when heeding the recommendations of our dedicated engineering team.  Recently, however, one of our lead plan-set designers, Carl, shared a cautionary tale regarding a DIY dilettante and a home solar installation project that both metaphorically (and literally) went off the rails: “Everything started off fine,” recalls Carl. “We designed the system plans as per the racking manufacturer’s specifications, but then, when the customer started digging to install the ground mounts, he hit rock and couldn’t go any further. Unexpected challenges like this can sometimes happen, so we took the data over to one of our certified engineers to advise us how to proceed.” Factoring in historical weather conditions, the updated plan included the addition of diagonal braces for structural support and excavating grade beams along the entire span of the installation to connect all the footings. Carl submitted the revisions back to the home installer.  “He didn’t like it,” Carl said. “He felt it was overkill and said that 99% of the time, the wind blew from the East and would be hitting the face of the panels. For the additional cost of construction, he didn’t think it would be worth it.”  Carl and the Go Green Solar team didn’t hear back from the homeowner for a while. Then, several months later, we got an email with an image of a crumpled ground mount solar system. Turns out, that gamble the person took on the wind never howling in the wrong direction didn’t pay off.  When you don’t follow expert advice. In an attempt to save around $800 in reinforcement upgrades, the person sacrificed a system that cost nearly $20,000 as it hadn’t yet begun to pay itself off.  “As long a person is handy and can go up and down a roof ladder with 50 lbs, they should be...

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Can Solar Power Your Air Conditioner?
Feb06

Can Solar Power Your Air Conditioner?

Maybe your electric bills aren’t that bad, except for summer when you have to run the air conditioning. But you are the conservative type, so you set the thermostat at 80 degrees and suffer through it. Because of this, you don’t think getting solar for your whole house can help you. You would only need the solar for a few months and only for the air conditioner.  Is it possible to just get solar panels for your air conditioning and not for anything else? It depends on who you ask. There have been many solar companies over the years that have advertised solar powered air conditioning systems but what were they really selling? Some of them were selling evaporative coolers (also known as swamp coolers). Contrary to having the word “swamp” in their name, these types of cooling systems only work in the desert because they rely on evaporating water to cool the air. They have very low power consumption and can often be operated with a single solar panel. If you live in the desert and don’t already have an evaporative cooler installed on your house, this is not a bad option to save on air conditioning. But, chances are, if evaporative coolers work well in your area, you already have one and it’s already saving you money on your air conditioning costs whether or not it has the solar panel. Other companies advertising solar power for your air conditioner were really just selling standard grid-tied solar power systems but sizing them smaller so they only offset the usage of the air conditioner and not anything else.  There really is no practical way to only power the air conditioner with solar panels. If you really wanted to do it, you would have to separate the electric circuit for the air conditioner from the rest of your house. Then you would purchase an off-grid solar power system with batteries to make sure that the air conditioner always had power even when it was cloudy. After you set all that up, you will have paid a lot of extra money for all the battery equipment and when the air conditioner wasn’t running you have solar panels on your roof going to waste because you isolated them to only run the air conditioner.  If you are going to install solar, you might as well install the system to the whole house. First, solar panels produce a lot more power in the summer than they do in the winter so they would be working hardest for you when you are running your air conditioning. Second, most electric companies offer net metering on...

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Choosing Solar Panels
Jan23

Choosing Solar Panels

The biggest part of a solar power system is the solar panels themselves. With dozens of different solar panels in warehouses across the US, how do you decide which ones to get? There are many ways to compare solar panels so let’s talk about what to look for. Many people make the assumption that a solar panel with higher wattage is always the better choice, but this isn’t necessarily true. If you are comparing solar panels that are same physical size and one of them is higher wattage, that means it is more efficient and will cost more money per watt. If you have a limited amount of space to install your solar panels, then the more efficient solar panel would be a good idea because you can fit more wattage in the space you have. But if you have plenty of room for solar panels, it may not be worth it to pay the higher price per watt for the more efficient panels. Lower efficiency does not necessarily mean lower quality.      Which brings us to the discussion of quality. Determining the quality of a solar panel is not an exact science but there are some things you can look for. Looking at the manufacturer is a good idea. Ask questions like how long they have been in business and whether they make things other than solar panels. What you are trying to judge is whether or not they will be around 20 years from now to honor their warranty. If they have been making solar panels for a long time, chances are they are good quality or warranty issues would have put them out of business. If are a major electronics brand, that make other things chances are they will stick around and honor their solar warranties because they will still want to sell their other products. Another way to determine solar panel quality is check what certifications it has. You can see our blog article “Solar Panel Certifications Demystified” for more details but all solar panels have to be certified to meet the UL 1703 standard but they can also take it up a notch and get certified to meet other IEC 61646 standards for durability and performance or get tested over time for the DNV GL PV Module Reliability Scorecard which is what financial companies look at when investing money into solar farms. Solar panel manufacturers can also get their factories certified to certain quality standards as well for added peace of mind.  Some people get hung up on different types of solar panels. They might insist on monocrystalline solar panels because they heard they are...

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Where Should You Install Solar?
Jan21

Where Should You Install Solar?

Everyone knows solar panels can save you money, but where should they go?  First, let’s discuss location on a larger scale. There is no place in the United States where solar wouldn’t work. You might think you it is too rainy, too cold or you live too far north and don’t get enough sun but let’s drop those excuses.  There is no location that gets too much rain. Even in Seattle with 226 cloudy days and 38 inches of rainfall per year gets enough sun for solar panels to be worthwhile because solar panels will still produce electricity on cloudy days, just not as much as they would on sunny days.  Too far north is not a problem, but there are things to consider. Unless you are at the equator, solar is going to produce more power and in summer and less power in winter because of the angle of the sun and the amount of daylight hours. The further north you go, the more extreme this is. In Alaska, solar works great in the summer but it won’t do much in the winter. In the continental US, you will still get solar power in the winter and with most grid-tied systems you would be on yearly net metering billing with your electric company so it doesn’t really matter what month the power was produced. Many people think solar panels don’t work when in the cold, but they actually work better when it’s cold out. Cold temperatures can increase solar production by as much as 10%. The other side of that is really hot temperatures will lower production by 10% but that still means your getting a lot of free power from the sun, so don’t sweat it. So now that you know you are in the right geographic location for solar, let’s talk about where to install solar panels on a smaller scale. If you have a few acres of land you will probably have plenty of room for a ground mounted solar system. Even a half acre yard might have enough space that isn’t shaded by the house, depending on the layout. Ground mounts have advantages in that they are easier and safer to install (no lugging solar panels to the roof or worries about fall hazards) and you also have more options on orientation. You can check out our article on ground mounts vs roof mounts to get a better understanding of whether or not ground mounted solar is right for you. If your yard is small, then your roof will be the best place for the solar panels. Solar panels facing south will produce the...

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