To Grid Or Not To Grid? - A Solar Decision

Posted by K.N. Jackson on Jun 26, 2020 3:58:53 PM

Yep, energy independence is a BIG deal.

It determines whether you're tied to "the system" or reliant upon your own resources. It could determine whether you have that extra cash to invest in your future this year...or not.

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When your neighbors are suffering widespread outages due to downed power lines, you're sitting back swiping through your favorite streaming providers online, or browsing through your social media posts, because your WiFi is still receiving electricity from your solar array.

When they're commiserating over yet another rise in their electric bills, you're touting the lowered costs you receive—if your bills haven't been eliminated altogether—because you invested in solar when the expense was manageable, the tax credit was high, and the industry was coming to fruition.

So, when your neighbors ask you how you decided to go solar, and what considerations one must take into account when seeking independence from an electric utility, do you inform them that there's an alternative to going completely off-grid? That for some folks going off-grid may not be preferable, and that there are ways to get the electric company to reimburse them for producing power?

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 Power, Power, Bo Bower

When choosing whether to go off-grid completely, or connect one's solar array to the local electric company's grid in order to net meter, also called a grid-tied system, sometimes aspects of both are better than one or the other. Using aspects of both is called a hybrid system.

What determines when a system can safely be considered hybrid? What are the characteristics of grid-tied and off-grid?

The answers may be less complicated than you think. Below are several considerations you may find helpful when making your decision. At the very least, they'll help galvanize your research journey by providing necessary information that every prospective solar owner must take into account before finalizing their installation plans.

 

 Grid-Tied Systems

 

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A grid-tied solar system can be described just as its name suggests: your solar array would be connected, or "tied" to your local electric company's power grid through the electric box on your home, just as it is now, except the bulk, if not all, of your power would be generated from your solar array instead of the power lines.

Pros: Grid-tying would allow you to sign a net metering contract with the electric company to accrue utility credits that can be redeemed at later times when your solar array isn't producing as much power. And if your solar array fails for any reason, the utility company's electricity grid would compensate, meaning you wouldn't need to maintain a generator or backup batteries like with an off-grid system.

Look at the solar array as your main source of power, and the electric company's grid as your backup power that may or may not be free depending on how much electricity your system generates throughout the year. 

With a grid-tied system, your peace of mind about outages is covered from more than one angle, giving you assurance that if one system is down, the other will definitely compensate!

Cons: While you are technically energy independent as long as your solar array is functional, you're not functionally independent if the size of your array doesn't generate enough power to meet all of your energy needs. In this case, your electric bills would be greatly reduced, though not eliminated.

Also, on a grid-tied system you're only allowed to produce up to 120% of your home's usual energy consumption without legally being considered a utility provider by the state. Therefore, the digital net meter box you purchase from your electric company when you install your solar system and sign your net metering contract will be monitored like your electric meter is now to ensure your energy production doesn't exceed the allowed percentage. You're functionally, but not technically independent, so if independence is your main reason for going solar, a grid-tied system may not be your best bet.

 

 Off-Grid System

 

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Off-grid systems are not tied to your local electric company's grid via your electricity box, and therefore you have true independence from their specifications for the energy production of your system. It can be as big as you need, though if your electricity production exceeds your usage, you'll need to "dump" the excess energy via one method or another. We'll explore energy dumping later in this blog.

However, the drawbacks of going off-grid are obvious, if also worth the risk to any owner. An off-grid system requires a generator or battery array to support it in the event it goes down or doesn't produce the needed amount of power. You're more likely to blow fuses in the system if you overload its capacity, and depending on the kind of batteries you choose to purchase, their maintenance can be crucial to the safety of the entire system. Let's look at the two (2) main types of batteries that homeowners buy.

 

 Back It Up!

Lead-acid batteries are comprised of lead pieces submerged in distilled water with electrolytes in the form of diluted sulfuric acid. As the electricity is conducted throughout the battery, the water comes to a boil and evaporates, meaning that lead-acid batteries require "watering" or refilling with the water-electrolyte solution periodically so they don't lose efficiency or catch fire and ignite the other batteries and equipment in their vicinity. The lead centers of your batteries must be completely submerged for best safety and performance life. 

 

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Lead-acid batteries are considered older technology, and cheaper than the newer, more expensive lithium-ion batteries that don't require watering. They take up more space, and are heavier also. They can reach 80%-90% efficiency, however, and if you don't mind the constant maintenance then you may want to consider these when building your off-grid array.

Over time, they will lose the capacity to hold a full charge, so their lifespan is approximately 5-7 years with proper care.

Lithium-ion batteries are the same type you'll find in laptops and cellphones, and nowadays are nearly the same price as lead-acid batteries. The lithium-ion material comes in the form of a paste that is encased in a plastic casing for safety, because if the paste comes into contact with oxygen it can combust and catch fire. While these batteries are indeed safer than lead-acid batteries, are lighter, consume less space, and require less maintenance, making sure they are stored safely so the casing doesn't become damaged or degraded is still just as important as safely maintaining your lead-acid batteries.

Like all batteries, the lithium-ion type will lose the ability to hold a full charge over time, although they last much longer than lead-acid batteries, about 15 years with proper storage and care.

 

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Lithium-Ion Solar Battery by Lithium Battery Power, LLC

 

 Off-Grid Hybrid Systems

Sometimes off-grid solar owners prefer to hybridize their systems. In an off-grid context, they may supplement their solar panels with alternative renewable energy sources like a wind turbine, and connect both systems to battery arrays or a generator to ensure that if one system goes down, the other can compensate assisted by the battery array or generator. These hybridized off-grid systems aren't as reliable as the grid-tied hybrid systems because the reliance on the local electric utility provides more assurance that power will be available more readily and in large amounts, but if your main concern isn't the readiness of power and instead about independence, then this sort of hybridizing of renewable energy sources may be the way to go if you want to go off-grid.

 

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 Grid-Tied Hybrids

In a grid-tied context, hybridizing means to hook a solar array to the local electric company's utility grid in addition to a battery array or generator and/or perhaps an alternative renewable energy source like a wind turbine.

It's essentially combining the best aspects of all systems to prepare for any scenario. With a wind turbine, you're more likely to generate more electricity where your solar panels' performance may lack, and with the backup battery array or generator, you know that if all other sources of power go down, you will still be able to keep your food fresh and your lights running for a period of time until the utility, or your renewable tech is functional again.

 

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 Wind Turbine Generators

Wondering more about these wind turbines? Easy peasy, lemon squeezy!

A wind turbine generator serves the same purpose as, say, a gas-powered generator, except it's powered by the force of the wind, which is a fantastic way to supplement your solar array in winter months when the weather is already unpredictable. 

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Primus Air30 (48V) Wind Turbine Generator

 

Many of the lower voltage turbines are less than $1000 before installation, and could serve to further strengthen the power output of your solar system in addition to ensuring that you have a backup source of power creation in the event your solar array needs repairs. They generate 1.5-2 kW (kilowatts) of electricity at their maximum output when wind is high, so if you're looking to go off-grid and need to plan for overcast months when your solar output drops, consider hybridizing your system with these on open areas of your property that receive ample wind.

The wind turbines, like solar panel tech, will need to be able to dump accumulated energy that you don't use periodically. Dump loads, also called diversion loads, will be explored in the final section of this post.

Primus Air turbines are available through McClintock's Green Energy Division in conjunction with installed solar systems. Want to consider other kinds of generators? McClintock Electric does free quotes!

 

 Diversion Loads

What is a diversion load, or a "dump load", in other words? 

When your solar array or wind turbine creates excess energy, that energy needs somewhere to go. If it's not being used by you in your home then it would normally be sent to your backup batteries so that they remain fully charged. But what happens when your batteries are fully charged, and there is still excess energy to be utilized? You don't want the excess energy to continue to flow to your batteries because if your batteries become overcharged it can hurt their performance life.

That is when a dump load becomes relevant. A dump load consists of a resistor like a heating element that the excess energy is diverted into when your batteries can't retain any more energy. Resistors carry resistive loads, which are generally used to convert electrical currents into forms of energy such as heat. Contrary to inductive loadsresistive loads don't generate magnetic fields. 

An example of a resistor in your home would be your water heater, and often your dump load from your solar array, water turbine, or wind turbine can be diverted to your water heater via a device called a charge controller or voltage regulator to heat your water rather than needing to draw upon the main source of power, or gas lines, to do so. In this way, the excess power creation can be controlled so that you don't short circuit your solar array or need to disconnect your battery chargers frequently. You can also divert your dump load to an air heater if your water heater is adequately powered, or simply disconnect your solar array from its batteries so they don't overcharge to avoid the necessity of using a diversion load.

Unlike with a solar array, it's not possible to disconnect wind turbines from their voltage regulator, which controls the amount of voltage created so they don't overproduce and damage components inside, so using them to initiate a dump load is important with wind turbines, especially if the turbines are connected to a solar array that may be affected if the batteries to which the entire system is connected overcharge.

There are certain brands of wind turbine that don't require charge controllers to manage the excess energy, and those options are better discussed with your certified installation professional.

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EPEVER MPPT Solar Charge Controller

 

 It All Starts Here

Hopefully by now, some of your questions have been answered about the differences between grid-tied, off-grid, and hybrid solar systems. Are you still interested in more specifics, say, about your home's potential for solar output?

Click on the button below for a FREE solar estimate and personalized home assessment that includes a 3-D rendering of your home with solar panels attached. Just upload a recent electric bill, fill out the form, and a McClintock Electric Solar Specialist will get back to you as soon as possible for a complimentary consultation!

 

Get My Free Assessment!

 

Topics: PV panels, solar, renewable energy, solar panels

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