[varkey]

Originally Posted by sj_koova

And any strong reasons why I shouldn't consider off-grid. I know cost is one.

You mentioned that on-grid can't go high capacity, but that is not true, in fact on-grid can go to any capacity as long as the grid can take it. 12-15 kW with on-grid is not a concern at all. Off grid is what is mostly limited due to storage/cost and other issues.

Leaving the cost aside, one other reason is wastage due to lack of storage. During the day, your energy demand might be less, whereas production is at the maximum. Batteries would get full relatively quickly and after that point, there is nowhere to store the energy produced.

I have a much smaller off-grid system, 1.3 kW solar panels, 2 kVA solar inverter and 2 x 150 AH batteries. On most days by 12 PM or so, the batteries are full, after that my usage during the day would be just the lights/fans/electronic equipments which wouldn't consume much energy and the solar generation is limited due to lack of demand. I wouldn't be able to run my non-inverter ACs on this setup during the day.

For a bigger off-grid system, these challenges may not be relevant, but not being able to use the grid as an unlimited capacity battery would have an impact on production nevertheless. In your case maybe going for a true hybrid solution might be better, this way, you are still connected to grid, and can export excess capacity. Most hybrid inverters have priority settings so you can always prefer solar and/or battery and use grid as a last resort.

[sudhirjaipur]

Originally Posted by wocanak

Background

In our residential community many of us were interested in exploring rooftop solar panels. We were vaguely aware that systems with batteries were very expensive, maintenance heavy and didn’t make much sense. The feedback from friends and relatives abroad (mainly in California) was that rooftop solar with net-metering kind of works out for them. When similar schemes were announced in India, we got more serious but it required someone to take a closer look, find reliable vendors and make some recommendations.

Nice to see such a detailed analysis. I have yet to go through the entire post, but am sure everyone would be benefitted by this.

On the first table where you have calculated savings on account of the variable tariff structure, my observation is that the saving would be much higher. The total consumption of power during a month shall be "Units generated (+) Units imported (-) units exported" and not "units Imported (-) units exported".

Thanks

[efgritesh]

Originally Posted by wankhade

My average consumption over last 4 yrs has been 305 units, for which I need to pay Rs 3175, That is 38000 per year!. And I paid 1.4L (excluding 43k subsidy for 3KW plant). Per that logic, I have crossed the breakeven!

Now that makes me wonder what kind of area is needed to install solar panels for 3KW. I live in an apartment with south facing balcony and ample sunlight throughout the day, not sure if thats an optimum condition for installing such a setup or we must get it done on rooftops only.

[Thad E Ginathom]

Originally Posted by efgritesh

Now that makes me wonder what kind of area is needed to install solar panels for 3KW. ...

I have dreamed about going solar sometimes, but not seriously looked into it. I might be wrong, but I don't recall ever having seen a table of roof/ground are required for the various kw panel configurations.

[wankhade]

Originally Posted by Thad E Ginathom

I have dreamed about going solar sometimes, but not seriously looked into it. I might be wrong, but I don't recall ever having seen a table of roof/ground are required for the various kw panel configurations.

As a rule of thumb, consider 100 sqft per KW of installation with each panel generating 330W. Now a days there are 450W panels, so it will demand even lesser space. But do consider in the cleaning aspects too! You need space for that too.

[wankhade]

Originally Posted by efgritesh

Now that makes me wonder what kind of area is needed to install solar panels for 3KW. I live in an apartment with south facing balcony and ample sunlight throughout the day, not sure if thats an optimum condition for installing such a setup or we must get it done on rooftops only.

It depends on how much your housing society would co-operate, as first you would be covering your balcony and secondly you would need 1-2 separate earthing connections from ground floor.

You may fit in 1-2 KW setup, but you need to give a thought on how you would clean those panels on a regular basis. If you have a bigger balcony do go for it after studying in the feasibility.

[Atul Kolekar]

Thanks for a very in-depth and informative post. One small observation, you seem to have not accounted for a concept called banking charge. In Maharashtra, MSEDCL currently charges few units for providing grid support which is calculated on the basis of production every month. That reduces the export or increases consumption depending upon your system design.

[chakky]

Originally Posted by sj_koova

I am considering off-grid for couple of reasons.

1. Clean 230 voltage all time through the Solar inverter and full battery backup. BESCOM has roasted many of my appliances in past.
2. Has a lot of power outages in the area. No dependency on BESCOM and community generator. (Will add a provision to toggle to BESOCM for emergency)
3. On-grid can't go high capacity. I will need around 12.5kW (Including ACs and EV etc..)

Any reliable suppliers who can do off-grid?

And any strong reasons why I shouldn't consider off-grid. I know cost is one.

Cost will be exhoribant and maintenance too. I have 3kw off-grid setup with 16 120ah lead acid batteries. That I use for all my lights fans a a side by side fridge and nightly one 1.5 ton inverter ac. It all works fine in the summer but during rainy time in Cochin it won't get fully charged. So i have had to set it up with a special device that automatically changes over from solar to kseb electricity once the lead acid batteries reach 50%.


When i say maintenance all lead acid batteries come with 5 year warranty and replacement but there is an issue that in most cases more the number of batteries you have, one by one randomly a battery will start failing. When that happens it causes your entire system capacity to reduce. During my warranty period after my first year , i had to replace all 16 batteries at different points of time. End result i have a mix of old and new lead acid batteries of differing age that it reduces efficiency of the already inefficient system.

Secondly lead acid batteries give out acid fumes, so always better to keep it in the open and terrace if you plan to go on a 12.5 kw system.

Topping up distilled water, cleaning battery contacts are all extra works and unless you are knowledgeable about this, it's a risk.

I wouldn't recommend tata power to residential customers because they have so many projects big and large they setup and go and only come when there is a complaint. My provider here B&B whom I got connected to when Bosch my first solar system Inverter stopped service here, has made it a point to come every six months to clean the panels top-up the battery etc to reduce failures. At that point they also realised one or two panels had shorted due to lightning strikes and had them replaced.


I am not trying to scare people away, but if you have a good service provider things are fine. I have further installed a 6.5 kwp 5kw ongrid system. This has given me approx 18k for the last two years as return of excess units given to the grid and at the same time i only have a. 175 rupees monthly bill despite running an ac 8/365 and other two ac during summer and running 1.5 hp motor four times a week for two hours plus watering the trees for about 5 months a year. So if you ask me I would highly recommend the same but this post was just to explain pitfalls...i have been using solar since close to ten years at home so my two cents.

[wocanak]

Originally Posted by sudhirjaipur

Nice to see such a detailed analysis. I have yet to go through the entire post, but am sure everyone would be benefitted by this.

On the first table where you have calculated savings on account of the variable tariff structure, my observation is that the saving would be much higher. The total consumption of power during a month shall be "Units generated (+) Units imported (-) units exported" and not "units Imported (-) units exported".

Thanks

You are correct, good catch. In the first table I have missed to take into account how many units would have been directly serviced by generation, so the savings would be higher. The savings column in the table is then the minimum savings.

But the RoI calculations are based on units used per month, so they remain valid. Let me know if you see any problem there. The Google Sheet I linked and used for RoI calculation can also benefit from a keen reviewer like you.

Originally Posted by efgritesh

Now that makes me wonder what kind of area is needed to install solar panels for 3KW. I live in an apartment with south facing balcony and ample sunlight throughout the day, not sure if thats an optimum condition for installing such a setup or we must get it done on rooftops only.

You have to check with your association and electricity distribution company on whether this is allowed. But technically a smaller plant is possible. Each panel is ~2.2m by ~1.1m, i.e. around 8ft x 4ft. If your balcony is say 12 ft, you can have 3 panels, wall mounted like a large sunshade/canopy. This will be a 1.5 kWp plant and produce around 6 units per day, i.e. 180 units per month on an average.

Originally Posted by Thad E Ginathom

I have dreamed about going solar sometimes, but not seriously looked into it. I might be wrong, but I don't recall ever having seen a table of roof/ground are required for the various kw panel configurations.

With the high capacity 540W panels, you need ~6 sqmt or ~64 sqft for 1 kWp (has come down from ~100 sqft). This will produce ~4 units per day or around 120 units per month. See dimensions above to get better idea.

Originally Posted by Atul Kolekar

Thanks for a very in-depth and informative post. One small observation, you seem to have not accounted for a concept called banking charge. In Maharashtra, MSEDCL currently charges few units for providing grid support which is calculated on the basis of production every month. That reduces the export or increases consumption depending upon your system design.

I have not seen this in the BESCOM net metering bill of my colleague, anyway I will give an update once we get our first net metering bill.

[sj_koova]

Originally Posted by chakky

Secondly lead acid batteries give out acid fumes, so always better to keep it in the open and terrace if you plan to go on a 12.5 kw system.

Topping up distilled water, cleaning battery contacts are all extra works and unless you are knowledgeable about this, it's a risk.

BTW, this is for a new house that is under construction. I plan to keep it on terrace or I have exterior space in the ground floor itself.

At my current residence, I have a 2.5KV UPS with 4 batteries on the BESCOM line. I added a servo stabilizer as well due to high voltage spikes. These batteries are on it's 6th year. Efficiency has reduced, but none of them have failed so far.

I considered solar option at my new place due to longer power outages and voltage issues I have been experiencing in the area. Several LED lights and appliances failed. It got better after I added the stabilizer.

My approved load in the new house is 10KV and the residence community provides 100% power backup (Rs.12 per unit for Generator backup). Considering the load, I will always be on the higher slab (expected monthly bill for electricity will be over Rs.10000 + additional generator charges).

Based on the recommendations I am hearing, a hybrid system may be the best option. I may still have to add the stabilizer to protect the appliances.

[chakky]

Originally Posted by sj_koova

BTW, this is for a new house that is under construction. I plan to keep it on terrace or I have exterior space in the ground floor itself.

At my current residence, I have a 2.5KV UPS with 4 batteries on the BESCOM line. I added a servo stabilizer as well due to high voltage spikes. These batteries are on it's 6th year. Efficiency has reduced, but none of them have failed so far.

I considered solar option at my new place due to longer power outages and voltage issues I have been experiencing in the area. Several LED lights and appliances failed. It got better after I added the stabilizer.

My approved load in the new house is 10KV and the residence community provides 100% power backup (Rs.12 per unit for Generator backup). Considering the load, I will always be on the higher slab (expected monthly bill for electricity will be over Rs.10000 + additional generator charges).

Based on the recommendations I am hearing, a hybrid system may be the best option. I may still have to add the stabilizer to protect the appliances.

Go for two systems instead of one hybrid. Keeping them separate ensures a redundancy that will be much better.

Hybrids are catching up but so far have not seen a mass adaptation. I initially had transformer less solar inverter. It's mother board kept burning out due to over load or over current. Finally they themselves replaced it with one that has transformer. Though older technology it's maintenance free ...

Usually the ongrid ones are transformerless and hybrid too. Hence i worry if there will be more frequent downtimes for the entire system than normal.

[wocanak]

aim120 had asked for the full size photo showing the connections to DCDB, Inverter and ACDB. So posting them here with more labels.

These are the changes near the main supply panel.

These are the earthing pits and the two pipes coming down from the terrace.

This should give a good idea of all the connections.

[Sandegov]

Originally Posted by wocanak

aim120 had asked for the full size photo showing the connections to DCDB, Inverter and ACDB. So posting them here with more labels.

Attachment 2419001

These are the changes near the main supply panel.

Attachment 2419000

These are the earthing pits and the two pipes coming down from the terrace.

Attachment 2418999

This should give a good idea of all the connections.

This should help a lot of folks,who are setting up rooftop solar, get an idea of cabling - thanks for this.

I am no expert in electrical things, I may be wrong but is it ok to connect your DC and AC earthing to a common cable?

And then to lightning arrestor? I thought the lightning arrestor should be completely isolated and run via separate cable and seperate conduit to ground?

[wocanak]

Originally Posted by Sandegov

This should help a lot of folks,who are setting up rooftop solar, get an idea of cabling - thanks for this.

I am no expert in electrical things, I may be wrong but is it ok to connect your DC and AC earthing to a common cable?

And then to lightning arrestor? I thought the lightning arrestor should be completely isolated and run via separate cable and seperate conduit to ground?

Guess, the text was not fully clear. In the image I have mentioned three separate earthing cables going out in the end.

It is three separate shielded earthing cables running inside the same pipe and going to three different earthing pits, spaced at least 2 meters apart. Since they are shielded cables, the vendor said it is fine to run them inside the same pipe/conduit and I think that is reasonable.

[Thad E Ginathom]

A basic question!

EB supply is 3-phase; solar power is single phase, right? How does that work? Or is something that is simply dealt with in the bidirectional meter?