原创 Rooftop Solar to Charge Home Inverter Lead Acid Batteries

I wanted to understand the cost versus benefits of investing in Rooftop solar for powering homes between 7and 10PM everyday.

Here is what I have and I am thinking aloud. So please feel free to comment on my thoughts:

225 Watts x 2 = 450W @ Rs. 60/Watt = Rs. 27,000.00
100AH x 2 Lead Acid batteries = 7,500 x 2 = Rs. 15,000.00
12V @ 200AH or 24V @ 100AH = 2400WH- Total Available Power
1KVA Pure Sinewave Inverter = Rs. 10,000.00
Battery Charger 450W/14.4 (LA Float Voltage) = 31.25A
On an average we can assume 20A of charge current being available from a 450W panel at 14.4V. So the battery charge time would be 10 hours. 20A Switched Mode Battery Charger with LA state Machine ( Trickle, Bulk, equalize & Float) and MPPT algorithm = Rs. 8,000.00

Installation/Wiring/Circuit Breakers/Switches etc. = Rs. 5,000.00

Total Cost = Rs. 65,000.00

Here is what I have for a Regular Household Power Consumption:

All Lights are CFLs.

Portico, 1 light = 40W
House Entry way = 20W
Hall, Living Room = 80W
Two Bed Rooms = 80W
Dining Room = 80W
Kitchen = 40W
Fans Throughout the House 4Nos = 160W
Refrigerator 385L = 200W

Total Power = 700W.
Inverter efficiency loss is 5%. So input power is 700/0.95 = 737Watts
737W for three hours is = 2211W = 2.211KWH = Rs. 15.00 + Taxes = Rs. 20.00
Per Month this utility bill = Rs. 600.00
Per year = Rs. 7,200.00

Payout Period = 65,000/7,200 = 9.0 Years

This additional 2.21KWH may push you into the next SLAB of the Utility bill or the utility KWH rate will only go up. In that case, the payout period may come down.

Assumptions:
1. all lights/fans will remain on simultaneously
2. wattages specified are norms in households
3. prices of all the hardware is close approximation

Advantages:
1.Dependancy of State Supplied Power is minimized
2.Power at home is independent of climatic conditions
3.no utility power required to charge the batteries

Disadvantages:
1. High initial investment
2. battery replacement every 3-5 years
3. battery + battery charger+ inverter space

2400W capability offers additional emergency standby power when needed.
Inverters are rugged compared to Uninterruptible Power Systems for these don't have to phase lock to the utility power and inverters also don't have to work as converters to charge the LA batteries when Utility power is present.
Lastly the solar panels are guaranteed for 30 odd years of operation so after the payout period, the energy cost is equivalent of battery service cost. This may look beneficial.

340W worth of CFL lighting can potentially be replaced by 200W of LEDs. Barrier to Entry in LED bulbs today is Cost. It can reduce your solar system cost marginally while adding lighting reliability.

Please let me know your thoughts.

Thanks,
Ram