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sizing your off grid PV system,
Hi folks, here are a few thoughts I have about where to start with solar PV. The most important reason, In my opinion, to have a solar PV system is to have a way to pump water when the grid goes down. I would recommend sizing your system to power your water pump plus what ever additional power reserve you can afford. The first thing to size is the inverter. The inverter should be a true sinewave inverter and be designed with controls to allow future inverters to be added in parallel. You can not parallel inverters unless they are designed to do so. The inverter must be sized to handle the maximum current that the pump will draw. This includes the startup inrush current. Keep in mind that most submersible pumps are very inefficient. For example lets say I have a 1 HP submersible pump. That equates to 746 watts. If it is powered by 240VAC then from the equation P=IXE, I = 746/240 =3.1 amps Assuming a 300% inrush current, peak current is 9.33 amps. Assuming an efficiency of 50%, the continuous power draw of the 1 HP pump motor would be 746X2= 1492 watts. Hence the inverter must be sized to handle at least 1492 watts continuous duty and a peak current of 9.33 amps at 240VAC or peak power of 2238 peak watts. You will probably want an inverter that also can charge from an AC source such as a generator. A good inverter will also have metering to keep track of the amp hour drain on the battery once it is calibrated to the battery. It does this by measuring power using a shunt and an algorithm in it's microprocessor. Once the inverter/s is sized, the battery and solar panels will be sized to accommodate the inverter. You will need a battery to power the inverter and a dc charger to power the battery from the solar panels. The only type of battery you will want to get for this high quality system is a lead acid flooded deep cycle 48V battery. It must be flooded so you will be able to measure the state of charge of the battery and the only way to accurately do this is by measuring the specific gravity of the flooded electrolyte (easily done with a refractometer). The larger battery voltage is needed to keep the cables smaller. It is important to be able to measure the charge on the battery so you do not discharge it beyond 80% of its rated AH capacity. That way you will get the most life out of the battery. The battery will be the most expensive part of the system over the long run and can easily be destroyed by discharging it too much too often. You will want an MPPT type solar battery charger. This is the most efficient solar charger and it would be a waste of your solar panel energy to get anything else.
This information comes from my experience after retiring from working as an electrical engineer for 40 years and from the solar system I installed for my self. I hope you all found it useful.
hey nice insight
if you were sizing electrical components for a farm with 15kw solar power and are installing equipment such as an incubator and fridge what systems would you use 110V or 240V
Thanks for sharing your knowledge here.I appreciate your valuable write up.
Definitely it will be very useful for all.
Hello Deba, just wanted to say thank you for the MPPT project and right now I'm marking off the check list to make sure I have all the needed parts. Looking forward to soldering everything in place!
Hi Deba, thanks for your sharing of the project. Just wondering in your version 3 of MPPT charge controller, why did you use 2 MOSFETs for the buck converte. Could you please explain for me? Cheers
In your version 3 of MPPT charge controller. You have made a Buck converter using MOSFETs and you're also using a LM2596 based buck converter. Why two buck converters are used?And why not use the same LM2596 module in both the places?
The LM2596 module is for power supply for the Micro controller and other auxiliaries like LCD,ESP8266 etc. The module is suitable for small current rating.Another thing is that you cant't vary the output voltage by using the MCU,you have to do it manually by adjusting the potentiometer.Though few people are working to hack the module so that it can be controlled by a MCU.
For our requirement ( large current ) its not suitable.
Hi Deba you have great ideas with good pictures qhich camera/lightening you use?? :-)
Hello, no such trick.I use my Nexus 5 mobile camera to take pics.I always take pics at day time ( indirect sunlight through window ).
Great!! Best way!! Btw nice articles!! :-)
Many thanks for this
Am wondering if there are Books out there for complete 63yr Old novices and learning and understanding Solar. Would like to eventually build a system so it will run a fan and small fridge etc when power goes out like it does, sometimes for days and in case of a major outage, would like the info in my hands to build a system or at least have the necessary products etc on hand, got a Generator etc, but noisy and expensive
On seeing your instructable, I am instantly motivated to try out a Solar Charger. Hats off Deba168
Glad you like my works...
Please I placed a comment/enquiry t on your mppt solar charge controller instructable. Please I am waiting your response. Thank you.
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