Newbie - 1.2KW System design for India

**Naptown** · 03-18-2013, 02:19 PM

Originally posted by vbhoj74

First off, thanks for the awesome information posted all over this forum.

I'm trying to size and arrive a cost for a 1.2Kw system for my apartment, for the cost part I would specially appreciate existing Indian users to come forward and help me.

Here we go:
-----------------
Determine the load in energy for a 24-hour period. Not the watts, but the watt-hours:

Device- W- Nos- Hrs/Day- WH/Day
CFL- 13- 4- 5- 260
Fan- 43- 3- 18- 2322
TV- 165-2- 4- 1320
Total: 3902 Watt/hr/daily

Total load at any given time: 511 watts (devices X w X Nos)
Determine the size of the solar array to be used: 3902X1.5 = 5853whr
DETERMINE SOLAR INSOLATION IN HOURS: 4.67kWh/m2/day
DETERMINE THE SIZE OF THE SOLAR PANEL ARRAY: 5853/4.67 = 1253 watts

DETERMINE BATTERY SIZE:
1 day backup and 50% discharge cycle: 3902 *2 = 7804 watts
Using 48v batteries: 7804/48 = 163Ah

DETERMINE CHARGE CONTROLLER SIZE IN AMPS: 1253/48 = 26Amp MPPT
Pure Since wave Inverter = Upper ceiling of Total load at a given time = ceiling of 511w = 600/650VA
------------------

Now for the queries:

1. I've taken only a 1 day backup time for the batteries since I stay in a Metro area and I do not have power cuts more than 2-3 hr. So 1 day backup should cover me for the power cuts as well let me use the energy at night time. Hope this assumption is correct.

2. I think finding a 165Ah/48v battery is difficult, I can see more of 24v and 12v around. I would be more happy with a single 165Ah/48v to maintain and that I have a space crunch. Any ideas ?

3. Is my calculation for Inverter correct ? or for that matter is there anything I missed our in the entire calculations ?

-------------------

Final BOQ for the system:

1. PV Panels 240w X 5 This is 960Watts a bit smaller than your calculations
2. Charge Controller (48v / 30a / 1400w max) X 1 Based on panels above you will need a 150V input 30A MPPT charge controller This is also an odd number of panels I would go up to 6 to make the strings on the Charge controller work I would get a 45A one.
3. Sukam Shiny 650 VA Inverter (Pure Sinewave) X 1 Don't know anything about this inverter )(but it is shiny)
4. Batteries 163AH/48V - FEI0-IN2000PLUS(200Ah/48v) X 1 or 4 165AH 12V batteries in series
5. Copper Wiring - As required.
6. Panel Mounting Stands - Any good local availability ?

Comments in red

**vbhoj74** · 03-19-2013, 03:04 AM

based on the inputs Naptown, here is the new BOQ I came up with (also took into account 80% efficiency of the inverter):

1. PV Panels 240w X 6 = 1440w
2. Charge Controller (150v / 45a / 1500w+) X 1
3. Sukam Shiny 650 VA Inverter (Pure Sinewave) X 1
4. Batteries 200AH/48V - FEI0-IN2000PLUS(200Ah/48v) X 1
5. Copper Wiring - As required.
6. Panel Mounting Stands - Any good local availability ?

How did you get to 150v for the charge controller ?

Is my calculation for the Inverter correct ? i.e. total load 511w/.8(PF) = 639VA rounded to 650VA or do I need higher, maybe 850 or 1KVA ?

**green_regards** · 03-19-2013, 05:37 AM

Originally posted by vbhoj74

First off, thanks for the awesome information posted all over this forum.

I'm trying to size and arrive a cost for a 1.2Kw system for my apartment, for the cost part I would specially appreciate existing Indian users to come forward and help me.
Since you mentioned "apartment", it would be helpful to mention the total no. of floors and the floor your flat is in. You will have to take into account losses in wiring. Also, there should not be any shading on the southern side of the apartment rooftop. The panels are usually mounted with a tilt towards the southern direction.

Also, do you have permission to mount the solar panels on the terrace? I think you will have to get a clearance from the apartment society.

Here we go:
-----------------
Determine the load in energy for a 24-hour period. Not the watts, but the watt-hours:

Device- W- Nos- Hrs/Day- WH/Day
CFL- 13- 4- 5- 260
Fan- 43- 3- 18- 2322
TV- 165-2- 4- 1320
Total: 3902 Watt/hr/daily

Total load at any given time: 511 watts (devices X w X Nos)
Determine the size of the solar array to be used: 3902X1.5 = 5853whr
DETERMINE SOLAR INSOLATION IN HOURS: 4.67kWh/m2/day
DETERMINE THE SIZE OF THE SOLAR PANEL ARRAY: 5853/4.67 = 1253 watts

DETERMINE BATTERY SIZE:
1 day backup and 50% discharge cycle: 3902 *2 = 7804 watts
Using 48v batteries: 7804/48 = 163Ah

DETERMINE CHARGE CONTROLLER SIZE IN AMPS: 1253/48 = 26Amp MPPT
Pure Since wave Inverter = Upper ceiling of Total load at a given time = ceiling of 511w = 600/650VA
------------------

Now for the queries:

1. I've taken only a 1 day backup time for the batteries since I stay in a Metro area and I do not have power cuts more than 2-3 hr. So 1 day backup should cover me for the power cuts as well let me use the energy at night time. Hope this assumption is correct.

2. I think finding a 165Ah/48v battery is difficult, I can see more of 24v and 12v around. I would be more happy with a single 165Ah/48v to maintain and that I have a space crunch. Any ideas ?

3. Is my calculation for Inverter correct ? or for that matter is there anything I missed our in the entire calculations ? Regarding the inverter size, a 650 VA inverter will allow you to connect atmost a 520 - 550W load at any point in time. It is better to go in for a 1KVA inverter atleast.

-------------------

Final BOQ for the system:

1. PV Panels 240w X 5
2. Charge Controller (48v / 30a / 1400w max) X 1
3. Sukam Shiny 650 VA Inverter (Pure Sinewave) X 1
4. Batteries 163AH/48V - FEI0-IN2000PLUS(200Ah/48v) X 1
5. Copper Wiring - As required.
6. Panel Mounting Stands - Any good local availability ?

I have tried to answer the queries based on my limited knowledge. Hope you find this useful.

**vbhoj74** · 03-19-2013, 05:52 AM

thanks for your valuable inputs green regards.

It is a G+4 structure, I'm on the top floor. I'm yet to read on wiring losses and how much max length can I run without any compromise. There is no shading on the southern side, and a permission to mount the panels has already been applied for, I don't see that as a bottleneck. Based on my Latitude, below are the panel title figures I calculated:

Winter: 44.1H/44V
Summer:-3.5H/90V

H=Horizontal Angle, V=Vertical.

Talking about the inverters, just a standard home inverter would do or do I have to have a solar inverter ?

**Naptown** · 03-19-2013, 08:11 AM

Originally posted by vbhoj74

based on the inputs Naptown, here is the new BOQ I came up with (also took into account 80% efficiency of the inverter):

1. PV Panels 240w X 6 = 1440w
2. Charge Controller (150v / 45a / 1500w+) X 1
3. Sukam Shiny 650 VA Inverter (Pure Sinewave) X 1
4. Batteries 200AH/48V - FEI0-IN2000PLUS(200Ah/48v) X 1
5. Copper Wiring - As required.
6. Panel Mounting Stands - Any good local availability ?

How did you get to 150v for the charge controller ?
I assumed you were using grid tie or 60 cell panels these will have a Voc of about 37 Volts Made 2 parallel strings of 3 collectors in series.

Is my calculation for the Inverter correct ? i.e. total load 511w/.8(PF) = 639VA rounded to 650VA or do I need higher, maybe 850 or 1KVA ?
Since loads tend to grow the 850 may be more appropriate but not much larger or efficiency will drop off

Comments in red

**vbhoj74** · 03-21-2013, 01:22 AM

Thanks for clarifying Naptown, tying up the panels in series or parallel was new to me, your answer made me dig into it.

Bad thing is, the best price as of now I got is Rs 50/w for the PV panels in my City, where as its available as low as Rs 32/w in some other cities. Huge difference I know, which is why I'm holding on to the investment till I manage to narrow the gap. Companies who quote for the entire system can be ridiculously high uptp Rs 350/w for the entire system, so doing it on your own is the only way I can go about it.

Info: 1USD = 54RS (roughly)

**green_regards** · 03-22-2013, 05:20 AM

[QUOTE=vbhoj74;69603]thanks for your valuable inputs green regards.

It is a G+4 structure, I'm on the top floor.

Then it should not be much of a problem. Just ensure that nobody damages the panel, as entry to the terrace is not restricted.

Talking about the inverters, just a standard home inverter would do or do I have to have a solar inverter ?
It is better to go for solar inverters as they have the additional electronics built in, to restrict the charging of the battery ( to 100%) from grid.. especially in situations when you have used up the battery and there is no sun...

**green_regards** · 03-22-2013, 05:43 AM

[QUOTE=vbhoj74;69933]

Bad thing is, the best price as of now I got is Rs 50/w for the PV panels in my City, where as its available as low as Rs 32/w in some other cities.

Rs.50/W is a good price for very good panels. They must have 25 yrs performance warranty..

Rs.32/W are low quality panels...They will probably not last long... will not suggest panels of this price.... and I guess they are given with a warranty of 10 years or so...

Huge difference I know, which is why I'm holding on to the investment till I manage to narrow the gap.

Even if you are ordering about 20 KW of panels per model ( say multiples of 250W), the best price a good solar manufacturing company will quote you will be Rs. 38 or Rs.40. Add to it the freight and transit insurance( usually Rs.1 /W) and packing( a company that does good packing will charge about 2%). Generally a distributor gets it at this price, the dealer will get it at another Rs.3 + more...and he will probably sell you at Rs.50/-

Companies who quote for the entire system can be ridiculously high uptp Rs 350/w for the entire system, so doing it on your own is the only way I can go about it.

The Govt of India prices it at Rs.270/W for an offgrid system. They offer a subsidy of 30% or Rs.81/W, whichever is lesser for systems upto 1KW.
A 1KW system should generate 3 units of energy per day. The price is for a system designed to give this output. However, there is no uniformity.. some say 1KVA solar system ( meaning they are using 1KVA inverter and not necessarily 1KW solar panels), some say 1KWp system. However, it is important to know how much back up the system gives. They should be able to specify the load and the no.of hours of back up. You can check if that 1KW system gives 3 units..if they have promised more, then iam sure the battery will be charged from grid....

However, Rs. 350/W is too expensive.

**vbhoj74** · 03-22-2013, 06:33 AM

Most people will bash me for this thinking, but I'm having this huge confusion w.r.t the viability of the project. The best turnkey prices after govt subsidies is Rs 185/w, I'm working on a 1440w capacity panels sizing in total which should give me approximately 4.5 kwh a day.

Case 1: market price from turnkey supplier
Rs 185 * 1440 = RS 2,66,400 / 7.5 = 35,520 kwh (investment / present rate of energy)
35,520 / 4.5 = 7,893 days required for ROI
7893/365 = 21.62 yrs
The increase in rate of energy will almost negate the interest on the investment.

Case 2: DIY with panel prices aroun Rs 32/w
Rs 52.08/w cost * 1440 = Rs 75,000 / 7.5 = 10,000 kwh
10,000 / 4.5 = 2,222 days / 365 = 6.08 yrs

Clearly case 2 makes a lot of sense. You get free electricity for the rest 19 yrs with only the cost of batteries. Check with surana ventures website, they seems to have advertised somewhere of Rs 32/w prices and their panels comes with 25 yrs performance warranty of 80% for the last 15 yrs if I remember. Issue is they don't seem to sell in my state or even respond to my mails. I don't mind paying the shipping, insurance and packaging etc, which will not be more than 10-15%.

**Naptown** · 03-22-2013, 09:36 AM

Originally posted by vbhoj74

Most people will bash me for this thinking, but I'm having this huge confusion w.r.t the viability of the project. The best turnkey prices after govt subsidies is Rs 185/w, I'm working on a 1440w capacity panels sizing in total which should give me approximately 4.5 kwh a day.

Case 1: market price from turnkey supplier
Rs 185 * 1440 = RS 2,66,400 / 7.5 = 35,520 kwh (investment / present rate of energy)
35,520 / 4.5 = 7,893 days required for ROI
7893/365 = 21.62 yrs
The increase in rate of energy will almost negate the interest on the investment.

Case 2: DIY with panel prices aroun Rs 32/w
Rs 52.08/w cost * 1440 = Rs 75,000 / 7.5 = 10,000 kwh
10,000 / 4.5 = 2,222 days / 365 = 6.08 yrs

Clearly case 2 makes a lot of sense. You get free electricity for the rest 19 yrs with only the cost of batteries. Check with surana ventures website, they seems to have advertised somewhere of Rs 32/w prices and their panels comes with 25 yrs performance warranty of 80% for the last 15 yrs if I remember. Issue is they don't seem to sell in my state or even respond to my mails. I don't mind paying the shipping, insurance and packaging etc, which will not be more than 10-15%.

The problem is you have only priced the panels. Add in the balance of system components and you will be much closer to the 185Rs cost.

**AMAR** · 03-22-2013, 11:57 AM

Don't worry

Mod note - No advertising - next time you will be banned

**vbhoj74** · 03-22-2013, 10:03 PM

Originally posted by Naptown

The problem is you have only priced the panels. Add in the balance of system components and you will be much closer to the 185Rs cost.

Rs 52.09/w I mentioned was for the entire system only with Rs 32/w for the panels. Since I was on a tablet when I posted it, my figures were off a bit. Here are the details:

Panels Rs 7680 X 6 = 46080
MPPT Charge Controller (150v/21a input / 45a output / 1500w+ max) - Rs 12,000
850 va inverter - Rs 5000/-
Batteries 163AH/48V - Rs 12,000
Wiring - Rs 2300/-
Panel Mounting - Rs 4500/-

Total - Rs 84180/1440Kwh = 58.45/w

Other equipment may cost 5-10% +/-, but it all depends on the success of being able to buy a good panel at 32/w. Else maybe I'll try it next year when the panel prices will come down.

**Naptown** · 03-22-2013, 10:15 PM

Originally posted by vbhoj74

Rs 52.09/w I mentioned was for the entire system only with Rs 32/w for the panels. Since I was on a tablet when I posted it, my figures were off a bit. Here are the details:

Panels Rs 7680 X 6 = 46080
MPPT Charge Controller (150v/21a input / 45a output / 1500w+ max) - Rs 12,000
850 va inverter - Rs 5000/-
Batteries 163AH/48V - Rs 12,000
Wiring - Rs 2300/-
Panel Mounting - Rs 4500/-

Total - Rs 84180/1440Kwh = 58.45/w

Other equipment may cost 5-10% +/-, but it all depends on the success of being able to buy a good panel at 32/w. Else maybe I'll try it next year when the panel prices will come down.

I wouldn't count on the part in red. I anticipate a rise in panel prices as the industry shakes out and the pricing comes back into the business sustainable range of about 15-20% more than today.

**green_regards** · 03-23-2013, 09:23 AM

[QUOTE=vbhoj74;70134]Rs 52.09/w I mentioned was for the entire system only with Rs 32/w for the panels.

I guessed you were talking about Surana panels @ Rs.32/W.My suggestion would be to stay away from them. They offer panels even at Rs. 28/W.

Panels Rs 7680 X 6 = 46080
MPPT Charge Controller (150v/21a input / 45a output / 1500w+ max) - Rs 12,000
850 va inverter - Rs 5000/-
Batteries 163AH/48V - Rs 12,000 . Well, a 12V, 180Ah battery costs Rs.12000 + VAT. Only one wont suffice. You will need to wire 4 such batteries in series, so you are looking at 4Nos X 12000 = 48,000/-. Please correct me if iam wrong.

Wiring - Rs 2300/- ( This is quite low as well. The wiring between the panel and inverter is usually done using a 16qmm single core cable. For 1m it costs around 1500/- or so. So, you are talking about nothing less than 10m )

Panel Mounting - Rs 4500/- ( a very good mounting structure to hold 1KW panels will cost nearly Rs.18,000/-, believe it or not. In coastal areas and in high rise apartments, it is better to go for a good mounting structure because of the winds!!
Total - Rs 84180/1440Kwh = 58.45/w

Other equipment may cost 5-10% +/-, but it all depends on the success of being able to buy a good panel at 32/w. They would have driven the Rs.50/W panel manufacturing companies out of business by now.

Else maybe I'll try it next year when the panel prices will come down. ( As Naptown has pointed out the panel costs may rise. Also, the trend in the last year or two has been that the lower cost of panels has been offset by the rising battery prices. The price of lead has been fluctuating and the battery prices rose up by over 15% in Dec and they are set to rise again in April..)