How Viable Is Solar Power Production In India?

1. A Basic Solar System

Now to the basics of a solar system. A solar panel, regulator/charge controller, battery and inverter.
This section covers only the basic information. Later in the blog, I have refined this system for greater efficiency and lower cost.
Click here for a brief overview of basic components.

2. Practical considerations

There are many practical concerns and doubts when installing a solar panel. Some are as simple as what happens on a cloudy day and some concerns require some thought and planning. Please click here to know the same.

3. Calculating Power Consumption

A simple calculator for how many solar panels do I need? As a first step, calculate your power consumption. This way you don't install beyond (or) below your needed capacity.

In my case, a 5 BR 5 Bath house in Tamil Nadu would consume 500 watts per hour for 12 hrs (6KWH in 12 hrs) in the morning and 333 watts per hour for 12 hours (4 KWH for 12 hrs) at night.

Please click here to see the detailed calculation I did for my house.

4. FAQ (On Solar Panel basics and power calculation)

Please click here if you have some questions on solar panel basics or power calculation. You need to have a clear understanding of section 1 (Basic Solar System) and 3 (how to calculate power consumption) before reading further. 

5. Calculating Power Requirements In Detail

Assuming 60/40 distribution i.e., 60 percent of the power is consumed in morning and 40% of the power is consumed at night, I computed I need a 3 KVA battery to be 70% independent of the Grid i.e. to produce 70% of the electricity needed through solar power. But it is very expensive and not practical for some one like me to spend that much money on battery.

I therefore decided to go with just a 1.5 KVA battery, tuning it to be 50% threshold. In short, the inverter will switch to grid power when the battery discharges below 50%. This threshold setup can be done on the inverter. These inverters are usually called 'Hybrid' inverters. This threshold setup is a MUST to get maximum life of the battery.

Moreover, for the first 100 units of power consumed the cost is only Rs 110. So, it is not required for my house to be independent of the grid, i.e produce 100% of the power needed..

Click here to see the calculation and apply the same to your needs.

6. Load Efficiency.

Understand Load efficiency  from your house hold appliances, to install the right solar power system.

Say if 200 watts of more power need to be produced it would mean spending more on 4 things,

more solar panels,
thicker wires ,
bigger capacity battery and
bigger capacity inverter.

Thinking in converse, if the load is some how made more efficient then it saves money on these 4 things.

Before installing a solar system it is therefore important to identify the energy guzzlers in the house and replace them with energy efficient devices. It is however not practical to replace ALL energy guzzlers, replace only the ones that make economical sense.

Click here for the most common energy efficient alternatives.

7. Calculating Cost for A Simple Assembly.

S.No	Electrical Component	Rating	Cost
i	Solar Panel cost for 1000 watts	4 X 250 Watts each	Rs. 60,000
ii	Grid Tie Inverter	1 X 1000 Watt Inv	Rs. 18,000
iii	Charge Controller	1 unit	Rs. 9,000
iv	SLA Battery	1 unit	Rs. 75,000

The cost of power generation (i + ii) would be Rs. 78,000. But the cost of power storage (iii + iv) is Rs. 84,000.Total system cost is Rs. 1,62,000. In addition, the batteries only have a life of 4 years.The cost of batteries are very expensive to some one like me. In the next section, I discuss a modified assembly with trade offs to provide a better return on investment to the user.

8. Modified Solar system for better Return On Investment.

The main reason for going with a 3 KVA battery is to be able to power devices at night. If only 1 KVA battery is used, then during the day power can be generated and consumed. At night power can be taken for consumption from the grid.
Just ensure the installed capacity of the solar panels is twice more than the power consumed. Otherwise the batteries discharge during the day, and as a result the batteries will not last long.

Circuit Diagram:

Grid tie inverter produces the AC power to feed the house. Any excess AC power will be used by the other (Dual) inverter to charge the battery. When the grid tie inverter is not operational at night, the inverter converts DC power from battery to AC power and feeds the house. This way we have eliminated the charge controller, but added an additional inverter (dual inverter).

NOTE:- Please buy quality components from known brands for your solar system. Do not buy cheap components. Power generation does pose a hazard and needs to be done carefully.

Click here to read about this diagram in more details.
Click here to know about pitfalls.

Cost of this system:

S.No	Electrical Component	Rating	Cost
i	Solar Panel cost for 1000 watts	4 X 250 Watts each	Rs. 60,000
ii	Grid Tie Inverter	1 X 1000 Watt Inv	Rs. 18,000
iii	Dual Inverter Cost (1000 W rating)	1 unit	Rs. 12,000
iv	SLA battery (1.5KVA)	1 unit	Rs. 22,000

The cost of power generation ( i + ii ) would be Rs. 78,000. The cost of power storage (iii + iv) is Rs. 34,000. Total system cost is Rs. 1,12,000.

Run all heavy appliances during the day and keep the power consumption minimal at night. One such example would be to run the air conditioner around 5:00 p.m to cool the bedroom to 23 degree Celsius. This power is supplied by solar energy.

Anything you can think of to do, to consume power in the morning is basically power savings for you.

At 9:00 p.m turn off the (dual) inverter and consume power from the grid till 6:00 a.m the following
morning. This prevents the battery from discharging to 50% below the rated capacity. So basically the battery is only used from 6:00 p.m to 9:00 p.m.

Once-again this 50% threshold is necessary to get the maximum life on the battery.

For me, it will reduce power consumption from the grid by 70%. That would be 628 units * 0.70 = 440 watts. So net power consumption would be 188 units.

Unit Slab	No Of Units X Cost Per Unit	Cost In Rs
For First 100 units	100 X 1.10	110
For next 88 units	88 X 1.80	158.4
Total	188	268.4

Total savings would be 1400 – 268.4 = 1131.60  every 2 months.

Over the year it saves 1131.60 * 6 = Rs. 6789.60
Say the battery under this usage lasts for 8 years (if used as stated it will easily last that long). That would mean a depreciation of Rs 2,500 per year. Even after that, the battery can be easily cycled to 80% of the previous capacity to last an other 2-3 years. Its up to you.

Overall, the system saves Rs 4,500 an year. That is a return on investment of 5% WITHOUT ANY SUBSIDY. At 30% subsidy, the return on investment would be 6% per year.

For commercial power utility lines as the power tariffs are as high as Rs 8 per unit. The return on investment for commercial buildings would be 10% per year.

In addition to providing a return of 6% per year, I can protect my lifestyle from the un-announced load shedding in Tamil Nadu, that killed most of my home town industries in Coimbatore.

9. FAQ (For Sections 7, 8 and 9)

Why go Solar? Especially if it is this expensive?

Valid question, I have made an attempt to answer the same. It may not be convincing to everyone. Please click here to read the same.

10. A Little Luck Experiment.

Up on producing excess power if the watt-meter (power meter) runs backwards, you have won a jack pot. You will not need any batteries. Just add an additional 250 Watt solar panel for Rs 15,000 and you are done. So the total system cost would be Rs. 75,000 (Rs. 60,000 + Rs. 15,000) only. No batteries required.

Click here to know about net metering, how net metering is subsidized in Tamil Nadu, and what this means to you.
 

11. Expanded Solar system (If you have a good Neighbor).

 
If you have a good neighbor then you can read this section. Otherwise skip this section. In the assembly discussed above just add 1 more mono crystalline solar panel. This will double your solar system capacity. Then run a 3 point AC wire between your house and your neighbor's house with a 250 Watt resettable fuse and watt-meter in between. The fuse will prevent the neighbor from consuming more than 250 watts.If using more than 250 watts, the fuse will disconnect automatically and needs to be reset. 
 

The watt-meter will show how much power your neighbor is consuming. Say you can sell this power to your neighbor (that is why I said good neighbor) at Rs 3.00 per unit. That would sum to a minimum of Rs. 400 month, for even a small family house with 4 people. 

The additional cost to you would be as follows,

Electric Component	Rating	Cost In Rs
Additional panels	1 X 250 W	15,000
Wire	1.5 KWH rating 20 mts.	1,000
Wattmeter	1.5 KVA rating	3,000
Resettable Fuse	1.5 KWH rating	1,000
Total	188	20,000

So your neighbor gets cheap and reliable power at Rs.400 a month. You would use your solar system to the maximum and get a return of Rs. 4,800 for an investment of Rs. 20,000.  

Note: Please do not run the wires across houses if it is not safe to do so. Also buy good double insulated outdoor copper wires that withstand moisture and humidity. Stably mount the wires above the ground.