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Ultimate guide: DIY solar kit
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Ultimate guide: DIY solar kit

20 mins 04 Oct 2020
It might be quite challenging for a novice solar farmer to figure this whole solar mess out. Some give up the first day and go for turnkey solutions, which normally cost like a one-way ticket to the Sun. Here is our ultimate guide on how to save money and DIY your own PV system. It will take just 5 steps.

Step 1.
Сalculate your energy needs

To become truly energy independent with a new solar PV system, you need to assess the amount of energy it will have to produce. Depending on your circumstances, the best approach will be one of the following.

Checking past utility bills is the most rational and time efficient. They will tell you the average energy consumption per month, which you just need to divide by 30 days.

You can expect some seasonal change in the numbers, especially if the climate in your area differs throughout the year. Some shifts in consumption patterns are also inevitable. We recommend using the highest monthly bill as a baseline, because it can give you additional safety margin.

Checking the power ratings is for those who value precision. Make a list of all the devices you use daily, find out their power ratings and multiply by the time you normally use them a day. Sum everything up to get your average energy consumption. Sounds doable for an RV solar installation or a marine power system: the power consumption there is more or less predictable. When it comes to a house, the task becomes herculean.

In any case, don't forget to account for a 20-30% energy loss. It's inevitable due to multiple reasons: shading, high temperatures, reflection, dust and more.
29.2 kWh/day – the average electricity consumption for a US utility customer

Step 2.
Choose the type of your system

There are several types of solar power systems: grid-tie, off-grid and hybrid. A grid-tie system allows you to sell excess electricity to the grid and therefore become a prosumer. On the other hand, an off-grid solar panel system can make you fully independent. A hybrid system can do both, hence the name.

You don't have to embrace one or the other right off the bat. Personal experience is an important factor and you always have the possibility to upgrade. To reap the first harvest from your solar farm you need two main elements – solar panels and an inverter.If you decide to go off-grid, it will require an investment in two more components – a battery and a charge controller.
The average number of peak sun hours per day

Size the PV modules

Size the PV modules

Let's take a house in New York that consumes the average 29.2 kWh per day. With 4.2 peak sun hours in NYC, the family will need a solar panel system with a capacity of

29.2 kWh ÷ 4.2 h = 7 kW

Such a system could consist of twenty 350 watt panels or eighteen 400 watt panels. The family may opt for panels of higher or lower wattage, depending on the available yard or roof space.

Size the inverter

Size the inverter

An inverter is used to convert direct current into alternating current, which is needed to run most appliances. The size of your inverter should exceed the wattage of your solar PV system. For a 7 kW system, an inverter with a nameplate rating above 7,000 watts will be a perfect match. You can also opt for microinverters, which are installed right on solar panels. Their size should correspond to the power output of a particular PV module rather than the whole system.

Inverter manufacturers usually specify sizing guidelines for their inverters in product specification sheets. When you know the wattage of your setup, just make sure that recommended maximum DC power of a specific inverter is slightly higher. If the power output of the solar modules paired with the inverter don't meet the stated guidelines, it may void the warranty.

Size the batteries

Size the batteries

First, decide how many days' worth of energy you want to store in your battery bank. The product of the number of days and watt-hours required per each day is the storage capacity you need. However, it should be multiplied by 2, since the recommended depth of discharge for most batteries is about 50%. To convert the result in kWh into amp hours (Ah), divide it by the battery voltage.

Back to the NY family. They want the battery bank to last one full day. As they consume the average of 29.2 kWh per day, it is the capacity they need. No battery can be discharged all the way to zero, so they add from 30% to 50%, depending on the type of batteries they choose.

29.2 kWh + 30% = 38 kWh (lithium-ion)
29.2 kWh + 50% = 58.8 kWh (lead acid)

This is the energy the batteries will have to provide. Thus, five 7.5 kWh (48 V) lithium-ion batteries can satisfy the needs of the family. If you go for bulkier, less energy dense lead acid, you will need twenty eight 2.1 kWh cells (12 V).

Size the charge controller

Size the charge controller

Take the wattage of your PV system and divide it by the voltage of your battery bank. Add 25% to allow for cold temperatures and round up to the tenth. A 7 kW system and a 48 V battery bank require a 40 A charge controller, as

7,000 ÷ 48 + 25% = 37 A

Step 4.
Go shopping

The steps that involve counting are over. It's time to begin the most exciting part – purchasing your solar equipment. A1SolarStore supplies all the necessary items for residential and commercial PV systems, making it possible to find everything in one place. Let's see if this is actually true.

The NY family doesn't have much roof space, so models like Q CELLS 400W or LONGI 445W would be an optimal choice. To build a 7 kW system they would need 18 or 16 panels respectively. The impressive efficiency and power output of both models is achieved by packing a large number of monocrystalline cells into the modules.

A1SolarStore has a variety of inverters ready for use in both grid-tie and off-grid systems. Sunny Boy 7kw or 7.6kW Fronius Primo are of the right size and offer additional functionality, for example interfaces for monitoring and datalogging, specialised online and mobile platforms.

Every inch of space is valuable, so buying 28 lead acid batteries didn't look very attractive. It just seemed like too many. Luckily, there are units that have significantly more storage capacity, like KiloVault HAB 7.5kWh. Five of them will be just fine.

MORNINGSTAR 45A charge controller, compatible with 48 V systems, became the last item in the shopping list.

Step 5.

It is the final step, but not necessarily the one you want to make on your own. The number of panels, type of roofing or terrain and relevant experience are all things to consider before going down the DIY road. It may be quite tricky and the solar equipment is much more expensive than furniture from IKEA.

Solar panels weigh a lot for a single human. Without a pair of additional hands, hiring professional installers is the only way out. Unless we are talking about an off-grid system, you will need to contact a professional anyway. Only a certified specialist can connect your system to the utility grid.

However, if the site isn't difficult and you are not alone, we have a number of articles dedicated to this topic. They are worth reading without skipping lines, because the installation process does not admit mistakes.

Following these 5 steps you can make your solar panel system from scratch. Very little time is needed to assess your energy needs and just two items are enough to crank up the process. There's no need to count it all down to the last watt and to choose the system type straight away. You can always upgrade from a minimal setup and the experience you gain will allow you to make wiser decisions.

A1 Solar team is always ready to help you out at any point of your journey to a new solar life. Per Aspera Ad Sol!
Illustrations – Marina Fionova
Tilda Publishing
Any solar DIY article is a great responsibility because some people rely on them to work with complicated and expensive equipment. I found all the data in the article to be correct and the suggested items optimal for described uses. The article also does well in underlining a very important point – if you have any doubts in your capabilities, contact a professional.
Cecilio Tavera
Solar installer with more than 12 years of experience in the field