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Home Solar Electricity Set up for an Off-the-grid Living

The post illustrates a simple calculated configuration which may be used for implementing any desired sized solar panel electricity set up for remotely located houses or for achieving an off the grid electricity system from solar panels.

Technical Specifications


I am very sure you must have this kind of circuit diagram ready. While going through your blog I got lost and could not really choose one best fitting to my requirements. 

I am just trying to put my requirement here and make sure I understood it correctly. 

(This is a pilot project for me to venture into this field. You can count me to be a big zero in electrical knowledge. ) 

My basic goal is to maximize use of Solar power and reduce my electrical bill to minimum. ( :-( I stay at Thane. So, you can imagine electricity bills. ) So you can consider as if I am completely making a solar powered lighting system for my home. 

1. Whenever there is enough sunlight, I do not need any artificial light.2. Whenever intensity of sunlight drops below acceptable norms, I wish my lights will turn on automatically.

I would like to switch them off during bedtime, though.3. My current lighting system (which I wish to illuminate) consists of two regular bright light Tube lights ( 36W/880 8000K ) and four 8W CFLs. 

Would like to replicate the whole setup with Solar-powered LED based lighting.

As I said, I am a big zero in field of electricity. So, please help me with the expected setup cost also.

 

The Design


36 watts x 2 plus 8 watt gives a total of around 80 watts which is the total required consumption level here.

Now since the lights are specified to work at mains voltage levels which is 220 V in India, an inverter becomes necessary for converting the solar panel voltage to the required specs for the lights to illuminate.

Also since the inverter needs a battery to operate which can be assumed to be a 12 V battery, all the parameters essential for the set up may be calculated in the following manner:

Total intended consumption is = 80 watts.

The above power may be consumed from 6 am to 6 pm which becomes the maximum period one can estimate, and that's approximately 12 hours.

Multiplying 80 by 12 gives = 960 watt hour.

It implies that the solar panel will need to produce this much watt hour for the desired period of 12 hours during the entire day.

However since we don't expect to receive optimum sunlight through the year, we can assume the average period of optimum daylight to be around 8 hours.

Dividing 960 by 8 gives = 120 watts, meaning the required solar panel will need to be at least 120 watt rated.

If the panel voltage is selected to be around 18 V, the current specs would be 120/18 = 6.66 amps or simply 7 amps.

Now let's calculate the battery size which may be employed for the inverter and which may be required to be charged with the above solar panel.

Again since the total watt hour fr the entire day is calculated to be around 960 watts, dividing this with the battery voltage (which is assumed to be 12 V) we get 960/12 = 80, that's around 80 or simply 100 AH, therefore the required battery needs to be rated at 12 V, 100 AH for getting an an optimal performance throughout the day (12 hours period).

We'll also need a solar charge controller for charging the battery, and since the battery would be charged for the period of around 8 hours, the charging rate will need to be around 8% of the rated AH, that amounts to 80 x 8% = 6.4 amps, therefore the charge controller will need to be specified to handle at least 7 amp comfortably for the required safe charging of the battery.

That concludes the entire solar panel, battery, inverter calculations which could be successfully implemented for any similar kind of set up intended for an off the grid living purpose in rural areas or other remote area.

For other V, I specs, the figures may be changed in the above explained calculation for achieving the appropriate results.

In case the battery is felt unnecessary and the solar panel could also be directly used for operating inverter.

A simple solar panel voltage regulator circuit may be witnessed in the following diagram, the given switch may be used for selecting a battery charging option or directly driving the inverter through the panel.

In the above case, the regulator needs to produce around 7 to 10amps of current therefore an LM396 or LM196 must be used in the charger stage.



The above solar panel regulator may be configured with the following simple inverter circuit which will be quite adequate for powering the requested lamps through the connected solar panel or the battery.


Pats list for the above inverter circuit:R1, R2 = 100 ohm, 10 watt


R3, R4 = 15 ohm 10 watt

T1, T2 = TIP35 on heatsinks

The last line in the request suggests an LED version to be designed for replacing and upgrading the existing CFL fluorescent lamps. The same may be implemented by simply eliminating the battery and the inverter and integrating the LEDs with the solar regulator output, as shown below:



The negative of the adapter must be connected and made common with the negative of the solar panel

Need Help? Please leave a comment, I'll get back soon with a reply!




Comments

  1. Hi Dear Swagtam sir,
    Is Possible By Using Solar Panel Mirror We can increase in out-put of Panel by 30%

    ReplyDelete
  2. Hi Dear Swapnil, yes that's possible...

    ReplyDelete
  3. Sawagatm bhai maine ek solar street light liya or open kiya to usme 6v4.5ah 3pc battery h or connection parallel h or superflux led h 172 nos or usme day night switch h bahot choti h relay ki trah but usper kuch camical giraya houa h jo samjh me nhi araha vo hai kya na usme se kuch awaz ati h relay ki trah to bata sakte h vo h kya or vo censer b nhi h plz help me

    ReplyDelete
  4. Hi shiraz bhai, It will difficult to judge without practically seeing it, however only a relay will make a clicking sound, no other component will make such a sound, so you can assume it to be a tiny relay....further checking of its pinouts will help to confirm the details.

    ReplyDelete
  5. _ nd + ki line gai houi h or us device se single line nikli houi h - ki usi se auto on off ho raha ty for reply

    ReplyDelete
  6. sorry, it will difficult to identify without a physical check

    ReplyDelete
  7. Hi Swagatam,
    Can this circuit be used for 24V/200W Solar panels and 30Amp current. We will use qty 2, 150AH batteries.
    Any modifications required, pls advise. thanks

    ReplyDelete
  8. Hi Anup, yes it can be used, however the IC may be able to work with a 24V input and/or produce 15 amps for charging the batteries therefore these will need to be reinforced with additional outboard transistors as shown in the first diagram of this article:

    https://homemade-circuits.com/2012/05/dc-to-dc-double-cell-phone-charger.html

    please ignore R3 and two output pins, just find how R1 is required to be configured with the above designs.

    ReplyDelete
  9. Sir ,
    can you suggest any circuit for the solar panel battery charging circuit in which about 10% of solar panel voltage charges the battery and rest directly gives power to output.

    Thanks.

    ReplyDelete
  10. Akhil, If you are using an LM338 based charger then you can simply reduce the current by adjusting the shown current sensing resistor value such that only 10% current is allowed to reach the battery.

    ReplyDelete

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