How to design your off-grid solar system in 5 steps

Do you want to design off grid solar system for home or commercial? This blog is very kind to beginner. We believe you will learn how to design.

Just like playing a car trip, we need to know what type of vehicle or how far you're driving, to caculate how many gas you need to run the car.

We will need to know your load and the using time of each appliances to calculate the solar panels power and the battery bank capacity.

This is the first step of design off grid solar system. It's very important. Seemingly little changes can make a big difference. Don't try to skip this step.

Right now that we know how much power each device is using. What do we do with that Info? Using a load calculator can help you create the loads list of the first step to design off grid solar system.

This calculator is available on all these website to use it. You enter the appliance name, quantity, and how many wants it is in ac or DC? If it's ac, if it plugs into a wall outlet, if it's DC, it runs off a battery like a cell phone car charger. 

On at the same time indicates that the system needs to be big enough to power those devices simultaneously. 

For example, you have no control over when your fridge compressor will turn on or when you will pump will. 

But you can control when you turn on a light. So if there's a chance that multiple devices may be on at once, you must select on at the same time, 

that will help you determine how big of an inverter you need to handle that power if they all turn on it once.

Some devices also have a high momentary surge, like a fridge or motor, it can use 2 to 4 times as much power for a few seconds when it first turns on, you need to keep track of that as well. for the first step design off grid solar system

Because if your inverter cannot handle that surge, the device may not be able to turn on, or you could damage the inverter. 

You need to enter how many hours a day advice will be on. If it's less than an hour, do the decimal equivalent? 

For instance, half hours . whether you're using the calculator or joining the list by hand, all of the water hours get added up to show the total amount of power you need to generate for that day. 

Step 2 of design off grid solar system is to size the battery bank power, to figure out how many batteries you need to store.

We'll discuss the different considerations that go into sizing your battery bank. We've already done a loads list in our previous step, so we know how much power will use each day. 

Now let's see what size battery bank we need to store it. The answer may surprise you. Just a quick reminder of the components that make up an off grid system. We'll be starting at the battery bank this step.

You need only enough storage for a day or two. You have another power source like a generator turbine that will kick in if the sun doesn't shine. 

Would you need to have enough batteries to store 3 or 4 days or more with the power? Would you be storing the batteries in a warm room? 

Or will they be in a cold location? Batteries are ready for storage at around 80 ℃, the colder the room, the bigger the battery bank you need to compensate.

By over 50 % more, it's below freezing. Each of the answers to these questions affect the size and cost of your battery bank.

What voltage battery bank you need, 12, 24 volt or 48 volts.

Generally, the larger the system, the higher voltage battery bank you used to keep the number of parallel strings to a minimum.

You can pick 3 days of autonomy and plan on using the journey to charge up the battery bank. If you need a day four depth of discharge or dod is how far you drain the battery down in design off grid solar system

Let us a deep cycle battery that is made for renewable energy systems can be drained down pretty low. But the less you drain it, the longer will live.

You often hear people say you can drain a deep cycle battery down to 50 %. That's true. 

But if you do, it will last half as long as if you drained it to only 20 %, each battery will have a depth of discharge chart.

You can see here that if you drain this battery down to 50 % using half its power, you can get about 1,500 cycles. What 1,500 days if you do that every day? That's just over 4 years. 

But if you only drain it down to 20 %, you can get 3,400 cycles. That's over 9 years. That sounds great, except you have to remember that requires a bigger bank to use a smaller percentage.

You have to balance the upfront cost of the system with how often you need to replace the batteries. You may also hear the term state of charge or SOC. That is percentage of how full the batteries are. It's the inverse of dod so battery that is 30 % depth of discharge is at 70 % state of charge. 

But if you need power much over, say, 2,000 watts at a time, you want to consider 24 volt and 48 volt systems, 

besides reducing how many parallel strings of batteries you'll have to have. It allow you to use thinner and less expensive copper cabling between the batteries and the inverter. 

Go to our off grid calculator to calculate what size battery bank you need based on these answers.

We'll discuss the different considerations that go into determining how many solar panels.

Step 1 and Step 2 showed how to determine the loads and battery bank. Now we'll do the solar panels for step 3 to design off grid solar system.

Now, you can figure out how much solar power you need. The cheat sheet can help you figure out how many solar panels you need for your solar system.

After knowing how much energy you need to make per day from the load calculator, you need to tell it how much sunshine you have to harvest from.

This available energy, from the sun, for a location is referred to as sun. Hours, the number of sun hours is basically how many hours the sun is shining on your panels and angle throughout the day.

They equal sunlight as if it were directly on your solar panels, when they get the most power. Like at noon, the sun isn't as bright at eight, am as it is at noon.

Let's face. It is no such thing as a perfect system with no losses.

But enough grid systems is a lot more than you would expect. Do the things like soiling of the panels and voltage drop on the wire, 

losses and batteries and electronics, and several other factors will be losing about 1/4 of the rated power from the panels.

So a hundred watt rated panel may actually give us only about 80 watts of usable power or even less after all the losses affected in.

Now that we know how many lots of panels we need, and which ones were using. The rest is pretty simple. 

You do need to make sure that the number of panels allows you to wire them so that the nominal voltage of the panels either matches or is higher than the voltage of the battery bank in design off grid solar system.

Now, we come to the step 4 to design off grid solar system. there's also a bit more to consider when selecting a charge controller. Charge controllers are available with two major types of technologies, pwm and mppt 

In short, if the voltage of the solar panel ring matches the voltage of the battery bank, you can use apwm charge controller.

If you have a 12pcs panel and a 12 battery bank, you can use pwm if your solar panel voltage is different than the battery bank and can't be wired and series to make it match, you need to use an mppt charge controller.

But if you're pouring any ac loads, you need to convert the DC current, the direct current from the batteries into the ac alternating current for your appliances. It's very important to know what type of ac power you need if you're in North America. 

The standard is one twenty two forty split phase, 60 hertz in Europe and much of Africa. And some countries in South America is 230 volts, single phase, 50 hertz. Some islands. It's an interesting mixture of both. So inverters are configurable between voltages and or frequencies. Many are fixed. Check the specs carefully of the inverter you're interested in to make sure it matches your needs in design off grid solar system.

 If you do have the North American standard, you must figure out if you have any appliances that use to 40 volts. If they're all just 120 volts, some voters are able to put out 240 volts, and then you wire the output to use either 120 or 240 volts. Other inverters are stackable, each one out putting 120 volts. 

When we are together or stacked, they can create to 40 volts. And others are only capable about putting 120 volts and can't be stacked.

Again, read the specs to determine which inverters right for you. You also need to know how many wants total your inverter will need to power.

Luckily, way back in step one, you created a loads list that figured out both the constant watts in the search requirements of your loads. 

Please note that an inverter is designed for a specific voltage battery bank, like 12, 24 or 48 volts. You should not feel selectable. So you need to know what voltage battery bank you're going to have before you settle on the inverter.

Keep this in mind. If you think you may be growing your system in the future. 

If you plan on having a higher voltage battery bank later, be aware that the lower voltage inverter won't work in the new bigger system.

So either plan ahead and go with a higher voltage to begin with or plan on changing out your inverter in the future.

But there are a lot of other little components needed like the fuses and breakers for over current protection.
What breaker box will you use? How you got amount of solar panels? What size wire do you need?

We've got more blogs that can help you with a lot of these details, like solar power components, part four, and wiring your solar power system.

We've also created some offered solar kits that have a lot of balance of equipment system already selected. You can see them here since solar really isn't one size fits all. They can be a great starting point to your own custom solar system.

Once you've gone through these 5 steps, you have a great start to design your off grid solar system. Give us a call with any questions if you want help design off grid solar system

Wang has over 10 years of experience in off-grid projects. And know how to wire the system well. Making every installation step easier.