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dubrd7 months ago

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.


CarlvinD dubrd4 months ago

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

deba168 (author)  dubrd7 months ago

Hi Bob,

Thanks for sharing your knowledge here.I appreciate your valuable write up.

Definitely it will be very useful for all.

DavidW3854 months ago

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!

yzh_95274 months ago

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

rjawale5 months ago

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?

deba168 (author)  rjawale5 months ago

Hi Rjawale,

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?? :-)

deba168 (author)  Gursimran Singh 4257 months ago

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!! :-)

YodaD8 months ago

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


deba168 (author)  YodaD8 months ago

Cheers :)

pawan g10 months ago

On seeing your instructable, I am instantly motivated to try out a Solar Charger. Hats off Deba168

deba168 (author)  pawan g10 months ago

Glad you like my works...

Telemabo11 months ago

Please I placed a comment/enquiry t on your mppt solar charge controller instructable. Please I am waiting your response. Thank you.