PLEASE DON'T ASK FOR AIRCON... IT IS TOO MUCH ENERGY CONSUMING AND THEREFORE NOT POSSIBLE WITH SOLAR UNLESS YOU HAVE A VERY BIG BUDGET!!!
Good day guys!
Today I’ve decided to make this thread about solar at home. It’s a little bit complicated so I will try to make it simple ( but long! ). First I must say that I’m not an engineer nor an electrician. All what I learn about solar come from internet and my own experience: I made my small home solar with no other help than internet, and it works very well, so maybe I can help you, I have 3 solar panels 50 watts, 1 inverter pure sine wave 1000 watts and 3 deep cycle batteries 125 Ah.
Before deciding to go solar you first must re-think how you use electricity! Forget about big electricity eaters like aircon, big fans, ref (some ref can be run on solar, I will tell you how later) because, unless you are very rich, you will not be able to run all these things with solar. If you are rich, you can afford to buy 20 batteries and 5000 watt solar panels so this thread is not for you!
Try to change things in your house before buying any solar, For example, change all your bulbs with led bulbs, your big fans for smaller ones, your old tv for a led one, electric stove for gasul and so on. Doing so, even if you don’t buy any solar, you will see your electric bill going down by at least 20%.
Now here is a tip about ref that can reduce your electricity bill up to 40% (just using this trick my bill went down from 800 pesos to 500):
First you need a ref with a chiller (those with two doors, the chiller on top, the ref sa baba) or better pa, a chest freezer that you are going to use as a ref. You must know that a ref use a lot of electricity each time it starts because of its compressor. For example a 100 watt ref will use 100 watts of electricity per hour plus, each time the compressor starts, it will use up to 1000 watts!! Each time you open the door of your ref, the temperature goes up and your ref starts and you eat 1000 watts right away... This trick may work also with a regular ref but I didn't try it yet. For sure it will work very fine with a 2 door ref or a chest freezer because they are better insulated.
So, it’s very simple: go to cdr king or any mall and buy a mechanical timer that can be plug in an outlet (180 pesos sa cdr king) program it to run 15 minutes every 2 hours, plug it, plug your ref on it... Voila! Your ref will consume 2 to 4 times less electricity! It works a lot better with a chest freezer, because they are better insulated so you can program you timer to run the ref only 15 minutes every 3 hours. If you do that with a 2 door ref, you must know that the lower part of your ref will not be so cold, so you must put all meat and fish or meal left over in the chiller part of the ref. You can achieve the same thing with a temperature controller, but it’s more expensive. For more details feel free to ask. Using a timer for your ref, you may be able to run your ref on solar in daytime only if you have only few batteries or 24 hrs a day if you have more batteries.
Now, let’s talk solar! Before starting you must know what is your normal consumption of electricity per day. For that you take your monthly bill and find how many Kw you consume, then divide it by 30 you will get your Kw per day. Then decide what you want to run on solar, Be realistic! If you have very few appliances with a small electric bill (small Kw per day), so maybe you can run almost everything on solar. But if you have an aircon, several fans, big tv, desktop computer.... You will have to choose which one(s) you want to run on solar. You must also determine how many hours per day you want to use each appliance and how many hours per night. You can run an appliance on solar while charging your battery but at night your battery will be the only one providing electricity.
You should know the watts and the amperage for each appliance. Usually watts are written somewhere on the appliance. to know the amperage you just have to divide the watts by 220 (the electricity in the philippines is 220 volts), Let’s take for example a 500 watt desktop. 500 watts divided by 220 volts = 2.27 ampers AC (AC means alternating current, the one from your outlet). Solar panels and batteries are usually in 12 volts DC (direct current)
Everybody will think that, in a solar set up, the most important is the panel... I would say NO, the more important is how you are going to stock your electricity, meaning....
the BATTERY: Batteries are rated in Ah (Ampere Hour) (ampere DC not ampere AC), for example, in theory, a 100 Ah battery will be able to run a 100 ampere DC appliance for 1 hour or a 10 amperes DC appliance for 10 hours. Coming back to our 500 watt desktop it will draw from the battery 46 amperes DC each hour so your battery will last 2 hours until totally discharged. Something very important in solar: NEVER TOTALLY DISCHARGE YOUR BATTERY. If you want them to last 7 and up to 10 years you should keep them at a 50 % charge. Meaning that you can use only 50% of your 100 Ah battery, so only 50 Ah. So, in our example the desktop will run only 1 hour before your battery is 50% discharged. Of course, time to time you can go up to 80% discharge but keep in mind that the more discharge is the battery, the less time it will last.
You can see that, if you want to run many appliances you need many batteries, and these are very expensive. For solar purpose use only deep cycle batteries. They are made to be charged and discharged many times and up to 80 % discharge with no problem. Some people use car battery. Car batteries are made to start a car, so they just give a fast and strong kick and the car starts, this just discharge a little the battery and then the alternator will recharge it right away. They are not made for deep discharging and recharging. So you can use them for a while but they will not last. It’s ok if you are in a remote place and you just want to have a light a night.
Batteries can be connected in parallel to get more capacity. 2 x 125 Ah battery in parallel will give you 250 Ah capacity so 2 times more time for your appliance to run.
SOLAR PANELS: solar panels are getting cheaper, that’s good news... You must first decide what appliances you want to run on solar, then you will know how many batteries you will need and only then you decide how many solar panels you need (if you want to expand your system, you can always add solar panels and battery) Usually 1 watt solar cell will charge 2 to 3 Ah, for example a 100 watt panel could charge 2 batteries of 125 Ah each. This is based on a 5 to 6 hour of direct sun on the panel. Solar panels can be connected in parallel to get more wattage. 2 x 50 watts panels in parallel = 100 watt panel
Solar panel must face South at a 10 degree angle. If you mount them on your roof you must make a chassis to allow the air to pass around. Overheating solar panel are less efficient and can be damaged. Avoid mounting them on a G.I sheet roof, it’s too hot in summer. Avoid any shade of trees or other... A small shade will lower a lot the wattage of the panels.
INVERTER: inverters are needed to transform the 12 volts current you get from your solar panels thru your batteries into the 220 volts of your appliances. If you use only 12 volts appliances (like 12 volts bulbs) you don’t need inverter. How many watts will be your inverter depend on how many watts are your appliances. A 300 watts inverter can run a tv and a laptop and lights. Some inverters are pure sine wave, others are modified wave. Pure sine wave are needed if you want to run a ref or sensitive equipment (some led tv might prefer a pure sine wave) To run a ref the inverter must be a minimum of 1000 watts. Don’t forget that the inverter will also draw some amperes from your batteries!
CONTROLLER: Controller are used between solar panels and battery to prevent the battery to overcharge and they help charging smoothly the battery. If you have more capacity battery than solar panels, you don’t need a controller because it will take more time to charge your batteries so no risk of overcharge. But you must monitor your batteries with a tester, time to time, to be sure that they are not overcharged. You can find cheap controller (around 1300 pesos for 20 amperes controller) be aware that these cheap controllers are fake. They will not charge your battery as a controller should, they just act like a switch by turning on and off time to time, the solar panels. Still useful, but expensive for a switch! I just use and old breaker box, that I switch off when I see my batteries getting overcharged, which is very seldom actually!
If you want to use a charge controller, the best is to buy a MPPT controller. It's more expensive than a PWM controller but a lot more efficient... With a MPPT controller you can charge your battery even if the total wattage of your panels equals the rating of the batteries (for example 100 watt panel and 100 Ah battery) This is almost impossible to achieve with a PWM controller. With a PWM controller you will need 2 times more panels to be able to charge your battery (for example 200 watt panel and 100 Ah battery)
WIRING: Never use smaller than #10 wire to connect your solar panels to the batteries unless your batteries are less than 5 feet from your panels. Up to 20 feet from the panels you must use wire #10, father you must use #8 or even #6... The farther the bigger wire.
FUSE AND BREAKER: for a small set up you need only a breaker or a fuse between the inverter and the batteries. If you have a controller you will also need a fuse or a breaker between the controller and the panels. Breaker and fuse must be for DC current not AC.
So, now, concretely, how it works? Ok, let’s take my small set up as example. As I said earlier, I have 3 x 50 watts panels, 3 x 125 Ah batteries, 1 x 1000 pure sine wave inverter, 1 fuse box with no fuse that I use as a switch, between the solar panels and the batteries and 1 DC breaker between the batteries and the inverter. Batteries and solar panels are wired in parallel to give me a total of 150 watts solar panels and 375 Ah capacity battery. My batteries are only 30 % discharged everyday (meaning that I could use 2 times more appliances or 2 times longer than I do up to now. But because the weather is still bad (still rainy season) I prefer to keep my batteries charge in case of brownout (frequent here).
So with this set up, I can run my laptop (50 watts) 8 hours, my led tv (80 watts) 4 hours, dream satellite receiver (20 watts) 4 hours, a led bulb 4 hours, external speakers (5 watts) 4 hours. As I said, I could run two times longer time all these appliances and my batteries will still be 40 % charged. When summer will be back, I will also run my ref. I already tried it and it works fine. The only problem is that I don’t have enough batteries to run it at night so I will just run it in daytime.
Be aware that appliances with engine like fan, power tools, blender, can be harsh on solar...
Now it’s time for questions..... Feel free to ask, I will do my best to answer you!
Go here for a simple step-by-step on how to make a diy off grid solar system
Go here for a Small-scale Off grid Solar PV: Installation Manual (alongside with others small interesting docs... just scroll down to get to this file)
Go here to calculate ampere AC to DC
See attachment for a chart to monitor battery with a tester
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