Here you can find Solar Panels and technological accessories related to Solar Energy: Click Here If you want to learn about Solar...
Here you can find Solar Panels and technological accessories related to Solar Energy: Click Here
If you want to learn about Solar Panels, to advise you before buying or to build your own Solar Panel: Click Here
what if you have $11,000 to spend on an offgrade solar system a subscriber recently asked me this question I need a reliable system that can run a fridge when the grid is down and it has to be recharged with solar power here's what I came up with stick around to see how long you can run the appliances and why this system is perfectly sized let me take you behind my screen and talk about the details of the system we have a 12vt 100 a battery for $187 a 2000 wat inverter which is UL listed and has a groundfold current protector built in for $288 four 100 wat solar panels that are wired in series for $198 a victron 150 35 amp mppt charge controller for $165 solar cables $17 charge controller cables $14 and battery cables $31 diff fuses and Breakers in the system will cost you $77 the total cost of the system will be $977 this is under the requested $1,000 budget but what can you run with this system we typically aim for two or 3 days of autonomy for offgrade systems which is how long the system can run without the sun recharging the battery so your battery size should be two or three times your daily energy consumption if you consume 1 KW hour of energy daily your battery must be between 2 and 3 Kow hours let me show you how to calculate for this system the battery we are using has a nominal voltage of 12.8 volts and is 100 amp hours which means we have a total battery capacity of 1,280 w hours or 1.28 KW hours let me show you the runtime based on my fridge my fridge is rated at 80 watts and uses 640 W hours per day it has a duty cycle of 30% meaning the compressor is on for 8 hours a day if we divide the total battery capacity of 1280 W hours by the consumption per day which is 640 W hours we get 2 days of runtime this was a quick explanation I recommend checking out my full video on the topic the following example is a TV it consumes 60 watts can you guess how we calculate the total runtime again we divide the total battery capacity in wat hours by the TV's power consumption so it becomes 1280 W hours divided by 60 wats equals 21 hours some people who are Advanced with offgrid designs might have spotted a flaw in these previous calculations to be completely accurate we must slightly increase the power consumption this is because the inverter is not 100% efficient most inverters are 90% efficient so the 60 wats from the TV will draw more than 60 watts so we must divide the power rating by the efficiency to become 60 watts divided by .9 equal 67 Watts the new run time is now 1280 wat hours / by 67 watts equals 19 hours I made it easy for you by designing a free tool on my website just fill in your appliances their consumption and the time they will be on then you get a result that shows you the amount of batteries and solar panels you will need the link will be in description let me explain why I chose these components and show you how the whole system is balanced first up the solar panels why did I choose 400 watts on average people have three Sun hours now you might ask what are three Sun hours I have 5 hours of Sun a day let me explain because this is often confusing one Sun hour equals 1, watts per square meter of solar irradiation when the sun shines in your backyard it might only be 600 WT per square meter solar panels are tested at 1,000 WTS per square meter so if you look at the back of the solar panel it says it's rated for 100 Watts but that's only at 1,000 watts per square meter this is why people rarely get their rated power out of the solar panel if you have 600 WT per square met solar idance your 100 watt panel will only deliver 60 watts my subscriber is located in Atlanta Georgia these are the sun hours he has available we can see that December has the lowest figure of the year with an average of 3.43 I went with 400 wats of solar panels because you can recharge the battery in one day with three Sun hours with 400 watts of solar energy we will produce 1 1200 W hours of energy per day the formula goes like this 400 W of solar panels * 3 Sun hours equals 1200 W hours if you live more Up N the Sun hours will decrease especially in winter I recommend using a generator to recharge your batteries during this time now that the solar panels are sized let's size the cable that will carry the power from the solar pan panels to the charge controller I have calculated the wire thickness from the solar panels to the charge controller they need to be 12 gauge so I will include that in the part list I have made a video about how to figure out the thickness of the wire according to the length explaining it in this video would take too long we also need a disconnect switch to isolate the solar panels from the system we can install a 10 amp dc circuit breaker right before the charge controllers input let's move on to sizing the charge controller the best way to wire the panels is in series because that's how we reduce the thickness of the wire and the voltage drop which will make the cables cheaper wiring the panels in series will increase the voltage so let's figure out what the maximum expected voltage will be each panel has a VOC or volts open circuit of 22.7 volts so 22.7 Vol * 4 panels equal 90.8 volt next we need to add a safety factor of 1.25 do you remember that one Sun hour is 1,000 watts per square meter and the solar panels are rated as standard test conditions of 25° or 77° F imagine it's a cold winter day with full sunshine and no clouds it could be that these conditions are better than the standard test conditions so the panel could produce 120 watts this is because the cold temperature improves the efficiency of the panel if we multiply the voltage of 90.8 volts with the SA safety margin of 1.25 we become a total voltage of 114 volts now we need to decide the current of the charge controller this one is easy divide the solar panel's total Power by the voltage of the battery we become 400 wat / by 12.8 volt equals 31 amps we need a charge controller with an input voltage rating higher than 114 volts and the current higher than 31 amps so we choose the victron 150 35 mppt you can also select a 30 amp charge controller I recommend not running the charge controller at 100% because this will heat up the controller and heat is the enemy of longevity next up is the sizing of the fuse and cable from the charge controller to the battery according to the victron manual we must choose a fuse between 40 and 45 amps so we will use a 40 amp mrbf use because it's easy to mount on the battery terminal I recently made a video about these fuses now we need to select a cable that can carry at least 40 amps this is an 8 gauge or 10 mm Square cable I will link the cable in the description as well it already has ring terminals so you don't need to add these I recommend crimping some fer Wheels on the end which goes to the mppt the same as with the Sor cables in the DC breaker and solar input on the mppt let's calculate the fuse and wire size for the inverter an inverter is not 100% efficient it's more like 90 % if the inverter delivers 2,000 wats on its output the input power will be higher for a 2,000 watt inverter with 90% efficiency this becomes 2222 Watts next we figure out the maximum current draw that's 2200 22 / by 12 volts and we get 185 amps then we multiply with a safety Factor we multiply 185 amps by 1.25 and we get 231 amps if you round these up the closest fuse rating is 250 amps now we need to find a cable that can handle at least 250 amps this is a 1 o or 50 mm Square cable I have linked all the cables in the description so you don't have to crimp theux if you are experienced with offgrid solar design you might have noticed something unusual in the system can you spot the issue the high current draw from the inverter and the 100 amp BMS inside the battery the BMS or battery management system regulates the current entering and leaving the battery it's designed to protect the battery by limiting the current to 100 amps which ensures safety and longevity of the cells inside but what does it mean for the system if you draw 100 amps at 12 volts that equals a maximum power draw of 1200 wats from the battery but our inverter is 2,000 Watts if you try to run a continuous 2,000 watt load the battery will likely shut down to prevent damage let me explain why we go for a slight larger inverter remember that my subscriber asked me to run a fridge knowing that the fridge has an inish current to start a compressor we must account for this you might think that the BMS will shut down if more than 100 amps is drown from the battery I have tested this myself and the BMS has search Power capability meaning it will deliver a larger current for a few seconds more than enough for the search Power demand if you want to run a continuous 2,000 watt load the solution is to add another battery in parallel this way you will increase the available current and prevent overloading the BMS you can also get a 12vt 200 amp hour battery with a plus BMS this means that the BMS can Contin to deliver 200 amps of current I have made a video on how to wire and fuse batteries in parallel so check it out if you're interested when we connect the inverter to the battery you can expect a spark if you can use a small resistor to pre-charge the capacitors in the inverter the spark itself is not bad for the appliance it might just scare you regarding the connection sequence connect the battery to the charge controller first then connect the solar panels to the charge controller and turn on the breaker then connect the inverter to the battery I will post a system with all the components on my website where you can find all kinds of free diagrams it will be the first link in the description if this video was helpful please give it a like thank you for watching and I will see you in the next one ...
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