Since 2019, as long-life, deep-cycle lithium iron phosphate (LiFePO4) cells begin to be used in solar energy storage and the price of solar panels continues to fall, more and more homes are installing solar systems to provide power for everyday life.
We have compiled some common questions asked by first-time solar energy system users, which are not comprehensive, but hopefully can help you.
How solar systems work
Solar energy systems work on the principle of photoelectric conversion.
When sunlight hits a solar panel, the solar panel converts it into electricity.
“How solar panels convert sunlight into electric current?
Solar panels are made up of silicon atoms. Think of the atoms as bricks on a building – like Lego building blocks – but because the atoms are so small, you need special tools to see them. Solar cells come from layers of silicon wafers that are similar in size to a dinner plate, but much thinner – only roughly three times thicker than an average hair.
The silicon wafer layer is heated to 1,000 degrees Celsius and then a metal sheet is placed on the back of the layer, while the solar cell is covered with a metal mesh with holes and this side is exposed to the sun.
When the 60 solar cells are prepared, they are fixed on a layer of glass to make solar panels. Generally, a solar power system on a roof has 10-50 solar panels, while in solar power plants millions of solar panels are installed.
Each silicon atom contains electrons of extremely small size and light mass, which carry a weak electric charge. When sunlight falls on a solar panel, it strikes one of the electrons and causes it to fall out of its electron orbit. These struck electrons are free to move, but the special construction of the cell allows the electrons to move only in a direction toward the sun.
So when the sunlight falls on a solar cell, many electrons will break out of their orbits and become free electrons, because of the nature of solar cells, the electrons can only move upward, thus producing an electric current that can drive household appliances.
If the sunlight falling on the solar cell is stronger, more electrons will be hit to get out of their orbit, and the more current will be generated. If the weather is not clear, the number of electrons hit will be reduced and the current generated will be reduced by 75 percent or more. At night, solar panels do not produce any electricity, and the power supply at this time is entirely dependent on batteries or other sources of electricity. “
These solar panels produce electricity, part of which is used to drive household appliances, part of which is stored in the battery.
When the sun goes down, the batteries begin to output energy for household needs.
What are the main components of a solar energy system?
- Solar panels
- Solar charge controller
- Battery system
How to choose a solar charge controller
There are two types of solar charge controllers: PWM type and MPPT type.
If your budget allows, please choose MPPT charge controller. Because MPPT charge controller has higher conversion efficiency and more scalability than PWM charge controller.
MPPT charge controllers are more expensive than PWM charge controllers, but in the long run, it can convert more energy than PWM charge controllers. This brings more than enough benefits to offset the price difference between them.
How to choose a battery system
Lithium iron phosphate (LiFePO4) batteries have quickly become the choice of most homeowners since they entered solar systems as energy storage units in 2020.
So when you’re planning your own solar system, choose LiFePO4 batteries.
LiFePO4 batteries have the following advantages.
- safety (no explosions, no fires).
- more cycle life (generally greater than 3000 deep cycle life, some even more than 6000 times).
- large energy density.
- better high temperature performance.
- environmental friendliness.
- light weight.
How to choose an inverter
An inverter is a device that converts DC power from solar panels or batteries into 110V or 220V AC power. There are two types of inverters: modified sine wave inverters and pure sine wave inverters.
For home applications, the pure sine wave inverter is recommended. This is because some appliances may not work or may be damaged when connected to a modified sine wave inverter.
The power selection of the inverter is based on meeting your current maximum power requirements while leaving a certain amount of margin. This is because there are bound to be other appliances added in the future.
How to determine if my house is suitable for a solar energy system
Be sure that your roof or yard has enough sunlight to reach it.
If you want to set up on the roof, then make sure that the south-facing roof has the right slope to collect enough sunlight.
When the roof is shaded by trees or does not have a suitable angle to receive sunlight, then consider installing solar panels in the yard and making mounts that can be moved to change the angle of the solar panels.
How to start designing my solar energy system
1, Find your maximum daily power needs
For all first time homeowners installing a solar system. We recommend that you start by understanding your monthly electricity usage.
Start by knowing your monthly electricity usage, preferably with a bill from the past year. Find the months that use the most electricity, usually during the summer months. Then calculate the maximum daily electricity usage.
At the same time, you should also record and observe your daily electricity usage. The best way to do this is to monitor the electricity consumption of your appliances with a small device called Kill-A-Watt.
Once you have finally calculated your maximum daily electricity consumption, combined with the daily hours of light in your house, you can calculate the total power of your solar panels and the capacity of your battery bank.
2, Determine the voltage of the solar system
Next you need to determine the voltage of the solar system. This is important because an unsuitable voltage design could end up pushing everything back to the drawing board.
If your ultimate goal is to go off-grid, we recommend that you choose a 48-volt system. This is because the current of a 48-volt system is lower than a 24-volt system, so that even with a whole-house load, the solar system does not output much current. This will keep the electricity safe.
3, Determine the number of solar panels and the capacity of the battery pack
Once you know the maximum daily electricity consumption, you can calculate the capacity of the battery pack.
Battery bank capacity = Maximum daily power consumption * Number of days of maintenance
For example, if your maximum daily electricity consumption is 15 kWh, and you want the battery pack to last for 2 days of household electricity in extreme weather (cloudy/rainy days), then
Battery bank capacity = 15 kWh * 2 = 30 kWh
Next you can calculate the number of solar panels.
For example, if you plan to use 500 W of solar panels and the Peak-Sun-Hour available in your area is 3 hours per day, then
Number of solar panels = 30 kWh / 3 hours / 500 W = 20
You need 20 500 W solar panels to meet the 30 kWh of energy you get per day.
4, Select Solar Charge Controller and Inverter
Based on what we described earlier, choose an MPPT solar charge controller and a pure sine wave inverter whenever possible.
In addition, choosing a device with high conversion efficiency helps to reduce the energy loss.
Can I set up my own solar energy system?
If you have some knowledge of electronics, you are perfectly capable of building your own solar system. This will save you a considerable amount of money. You only need to pay for the cost of materials.
In the process of setting up a solar system, you need to have the following skills.
- circuit planning.
- connecting equipment.
- making mounts.
How much money I can save by assembling solar energy system by myself
If you buy your own solar panels and assemble your own LiFePO4 battery pack, you can save approximately 60% of the cost.
Can I assemble the LiFePO4 battery pack by myself?
Of course you can. Assembling a LiFePO4 battery pack is easy.
The main materials needed to assemble LiFePO4.
- LiFePO4 battery cells.
- Kapton tape.
- Wooden plate/threaded rod.
All battery packs are made up of battery cells and BMS. You can buy high quality Grade A LiFePO4 battery cells from energiepanda.com. Connect the cells in series and parallel according to your designed battery pack voltage and capacity.
Each way series cells are paired with a BMS to manage the battery cells.
Kapton tape is used to bind the battery cells.
Planks and threaded rods are used to compress the battery cells to prevent the cells from expanding.
Assembling the LiFePO4 battery pack yourself can save about 50% of the pack cost.
How long does it take for a solar energy system to pay for itself?
The cost payback period ranges from 6-13 years depending on the cost of electricity in each location.
How many years can a solar system work?
Solar panels have a working life of about 20 years.
The lifetime of LiFePO4 cells is mainly determined by the number of cycles. With a cycle life of 3,000 cycles it works for about 10 years.
Solar charge controllers and inverters have a working life of 5 years or more.
Can I go completely off-grid by installing a solar energy system?
Yes, you can completely rely on the solar system to be off-grid.
In fact in recent years more and more homes are relying on solar systems to choose new places to live, lakeside, mountaintop, countryside, forest.
But it’s important to note that while the solar system you design will produce enough or even more than enough power for your home’s electricity needs each day. But there will still be extreme weather that will cause you to have no access to sunlight at all for several days.
So a backup set of generators is very necessary.
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