Off-grid living has gained tremendous popularity in the last few years, and one of the critical necessities when living off-grid is a consistent supply of energy. Among the few available options of energy sources, the most popular is solar, owing to the obvious reasons of its incredible flexibility and reliability of operation, as well as the simplicity of installation. As a result, going off-grid today is almost synonymous with going solar.
The following article is structured as a step by step process which teaches you how to choose the appropriate batteries, solar panels, inverter and charge controller, and then instructs you on how to connect and set them up properly.
1.Analyzing the Loads
First, make a list of all the appliances that will be run and define the number of hours they will be dependent on the solar energy.
Second, check the specification chart of each appliance on the list to find out their power rating.
Next, you need to calculate the Watt Hour: WATT HOUR = RUN TIME x PRODUCT POWER RATING
Lastly, calculate the total Watt Hour. It is the number you get when you calculate Watt Hours for individual products and then add them all together.
Led Lights: 20W x 8hrs = 160Wh; Fridge: 100W x 24hrs = 2400Wh
Laptop: 35W x 4hrs = 140Wh; TV: 50W x 2hrs = 100Wh
2. Selecting the Battery
Many types of lead acid batteries, including flooded, gel and absorbent glass mat (AGM), are available. They cost less than LiFePo4 batteries, but the drawbacks of lead acid outweigh that advantage. They’re heavy, making them a poor choice for mobile installations. With their shorter life span (300 to 1,000 cycles), you’ll pay more for them over time.
Then Right-Size Your Battery Bank:
Once you have the specs for everything, start by purchasing and installing the batteries first. The batteries in the market exists 12V/24V/48V. Your system might require a different voltage. This depends on the input voltage of the inverter.
Based on the above loads, multiply that number by the days of autonomy (DoA) — that is, the average number of days you expect complete cloud cover.
That is: 2800Wh/day x 3 DoA = 8400Wh
Assume that 48V system is selected，the the necessary Ah is: 8400Wh/48V=175Ah
Based on these equations, our battery bank needs at least 175Ah to accommodate this simple system.
3.Selecting the Charge Controller
Charge controller is a device placed between a battery and a solar panel, used for the regulation of current and voltage that is coming from the solar panels. It regulates the charge to the battery as the input voltage from panels rises. That way, charge controller prevents the battery from overcharging.
There are three types of charge controllers to choose from:
ON/OFF, known as the least efficient one; MPPT, maintaining the status of a highly efficient charge controller, but also a costly one; PWM, which delivers satisfying results at a fairly affordable price.
The final decision should be made based on your personal preferences, but our advice would be to go for either MPPT or PWM
4.Selecting the inverter
Inverter is a device used to convert the direct current into alternating current (AC), that is, the electricity that powers your appliances.
Inverters come with a predefined voltage rating, with the smaller sizes usually having a 12V or 24V rating. When setting up the entire system, select the solar panels, charge controller, and batteries so they configure to this rating.
On the power rating side, always select an inverter slightly larger than your calculated system size. For example, a 5000W inverter should work if your load calculation says you need a 4000W system. Last but not the least, always prefer an inverter with a pure sine wave output for the best efficiency.
5.Selecting the solar panel(s)
Based on the load calculation and the selected batteries, controller, and inverter, the next step is choosing and installing the correct solar panels based on the voltage rating.
The purpose of a solar panel is to convert the sunlight it receives into electricity as direct current (DC). They are typically categorized as monocrystalline or polycrystalline, the former ones being slightly costlier, but more efficient.
Factors Determine the Solar Panel Sizing:
a. Daily energy consumption;
b: Number of Peak sun hours:
The first step for sizing the solar panel is to determine the amount of sunlight received where you live. While the amount of sunlight your panels receive is important, a more accurate representation of the amount of energy your panels can produce is peak sun-hours.
The peak sun hours is the number of hours per day during which the average solar irradiance (sunlight) is 1000 watts per square meter (W/m2) or 1 kilowatt per square meter (kW/m2).
One peak sun hour = 1000 W/m2 or 1kWh/m2 of sunlight
c. Solar panels efficiency:
You will never get the rated power from the solar system because there are few losses associated with it like :
1). Soiling Loss: Loss due to dust deposition on the solar panel
2). Shading Loss: Loss due to shadow by trees and building near to the panels
3). Wiring Loss: Loss arises in the inter panels cabling and cable from panels to the battery bank.
The typical efficiency is 70% ( considered the worst situation )
Solar Panel Sizing:
You can use the below formula to determine the solar panel wattage:
Solar Panel Watt = Daily energy consumption ( WH) / ( Peak Sun Hour x system efficiency )
Daily energy consumption = 2800WH
Peak Sun Hour = 4.5Hrs
Panel Watt = 2800 / ( 4.5 x 0.7 ) = 888.88W
Assuming that the panel used is 450W, the required quantity is:
Number of panels=888.88W/450W=2
You have to purchase 2pcs 450W panels
The interest in sustainable, off-grid living has exploded in recent years, and there is rarely a better option for your off-grid energy needs than setting up a solar power system. All you need to design and install your own off-grid unit is to figure out the specs, do a few basic calculations, understand the basics, and you are on your way to building a self-sustaining off-grid haven.