Rooftop Solar Power Plant

From the time i took a pledge to be a little green in my living, i wanted to run my house on solar power. I am a great believer that Solar, wind and small hydro power are really a sustainable solution for the energy crisis that we are facing. 

Solar power, however is an expensive technology and does not yield economic returns in the short to medium term. But i still feel its affordable for the middle class. It is because of subsidized grid power that solar power has not gained popularity and its a general feeling that solar power technology does not break even at all. Also the environmental costs of producing conventional power (Coal, Large scale hydro) is never captured in our calculations. 

The idea of this post is not to argue for an economic case for solar but its about my efforts to put up a solar power plant on my rooftop. We designed and installed the rooftop power plant in our house in March 2014. 

Below i try to put down my experience in designing and installing the power plant. 

Energy Requirement:

The First step in designing the system is to carefully examine one's Power requirement.

The power you need is the instantaneous intensity of electricity required to power the appliances you use; this is measured in kilowatts. The more appliances that are used at the same time, the more power required. Energy is a measure of the length of time you have used a given amount of power. It depends on the power required by the appliances and on how long and how often you use them. Electrical energy is measured in kilowatt hours (Kwh). You need to know the electrical power and energy requirement for lighting, heating, cooking and other uses for your home.  How large a system do you really require is a function of Power requirements which is not very easy to measure .

To estimate how much electricity you need:

• List all your electrical appliances and lights and note when and how long they are used.

• Note the power that each appliance consumes. An appliance’s power rating is usually written on the back of the appliance and is measured in watts or kilowatts. 

• Record the number of hours each appliance is used in a typical day.

• For each appliance, multiply the power rating in watts by the number of hours used each day to obtain the number of watt hours (or kWh) that the appliance uses per day. 

• Energy-use patterns change with the seasons (e.g., lighting is generally used more in monsoon/winter).

• Add up the watt hours for all your appliances. This total is an estimate of your electrical energy consumption per day. Then you can calculate how much energy you would need per month.

The above exercise was done for the lighting loads of my house (Excluding heaters, refrigerators, microwave oven and iron). 

The table below are the results

Sl No	Utility	Power rating  (W)	No  of Hrs	Watt Hours   Consumed         (Wh)	Units             (Kwh)
1.00	Fan 1 (Office)	70.00	8.00	560.00	0.56000
2.00	Fan 2 (Hall)	80.00	4.00	320.00	0.32000
3.00	Fan 3 (Room)	70.00	7.00	490.00	0.49000
4.00	LED 1 (Office)	7.00	5.00	35.00	0.03500
5.00	LED  2 (hall)	10.00	4.00	40.00	0.04000
6.00	CFL 1 (room)	14.00	2.00	28.00	0.02800
7.00	CFL 2 (kitchen)	14.00	2.00	28.00	0.02800
8.00	CFL 3 (utility)	8.00	0.50	4.00	0.00400
9.00	CFL 4 (Bathroom)	5.00	0.25	1.25	0.00125
10.00	CFL 5 (Toilet 1)	5.00	0.50	2.50	0.00250
11.00	CFL 6 (Toilet 2)	5.00	0.25	1.25	0.00125
12.00	CFL 7 (Toilet 3)	5.00	0.25	1.25	0.00125
13.00	Computer 1	90.00	9.00	810.00	0.81000
14.00	Computer 2	90.00	6.00	540.00	0.54000
15.00	Television	100.00	6.00	600.00	0.60000
16.00	Set top box	5.00	10.00	50.00	0.05000
17.00	Misc				0.25000
Total				3,511.25	3.76

So i need to generate about 3.8 Units of power per day to power all my non inductive loads. 

The next step is to choose the type of system. That is to design an optimum configuration where the solar power, the battery power (Charged from solar and grid) and the grid power is used in the most efficient manner. Broadly there are three configurations. 

1. Off Grid System: Off Grid or stand-alone system refers to being independent of the state grid. The design would support all the loads and sufficient back up can be provided to cater to the power needs worst conditions.

One can go off-grid for low intensity loads. In other words, all equipments having a power rating lesser than 500W can be taken off grid. 

2. Grid Tied System : In grid tied systems, the system is interfaced to the state power grid. Here, Solar takes the first priority to run the loads. The excess power, if generated will charge the battery bank. The excess from the battery bank is fed into the state power grid. Grid tied system can be configured without battery bank also.

In case there is deficit of solar power, the differential power is drawn from the state power grid.

In case of grid tied system, a meter to record the net power (Net metering) will be installed.

3. Hybrid System or Grid interactive system: Hybrid system is a smart system involving, solar, grid , battery bank. A DG can also be added if required.  Here, Solar takes the first priority to run the loads. Excess power generated will charge the battery bank. During night battery will support the loads till a safe battery voltage. System will switch over to grid automatically below battery safe voltage. (If GRID is not available and battery has been discharged, PCU can command DG to start and supply power to the loads till Grid or solar is restored).

Hybrid systems can also be configured as grid interactive systems where only solar and grid are present. Here, the first priority is given to solar. Excess power generated will charge the battery bank. During night battery will support the loads, till a safe battery voltage. System will switch over to grid automatically below battery safe voltage. This would extend the battery life and provide seamless power supply. There will be no power exported to grid. 

In view of economy and ease of use, the grid interactive system is the best. One can slightly under design the system also if budget is a constraint. 

In my house, i decided to go in for a grid interactive system. The system consists of 

1. Solar Panels

2. Battery Bank

3. PCU or Power conditioning unit. 

In bangalore weather conditions, one kilowatt peak (KWp) will generate about 2.5 units of power per day on an average bright day. So if my requirement is 3.8 units per day, i would need 1.52 KWp. 

So i would need a power conditioning unit (PCU or inverter) that can support 1.6 KW. However, it is prudent to go for slightly higher PCU to account for accidental higher loads (or in event of guests at home).

The battery bank is designed to cater to maximum night loads. Also many PCUs needs a basic minimum voltage to even start. As such for a 2KW system that i decided to put, i had to connect 4 batteries of 12 V each in series to give 48V. 

So my final configuration was

1. 6 modules of 230Wp solar panels (total of 1380Wp)

2. 4 numbers of 100Ah, 12 V deep discharge batteries in series. 

3. 2KW PCU (i decided to go with a PCU with transformer).

The mounting structure proved to be the most difficult part of the installation. There were two riding considerations for mounting structure. 
1. The structure has to be non penetrative. That is we did not want to drill the roof to fix the structure. 
2. We wanted to keep the cost to care minimum without compromising on quality and safety.  

The mounting structure was designed in view of economy and wind loads. The design we arrived was a very simple "Z" section of 3mm thickness, web length of 6 inches and flange length of 9 inches with oblong slots. We got the same fabricated with powder coating. 6 such sections were fixed to each panel.  

The panels were just anchored to the mounting angles with nuts and bolts. The panels with angles were placed on the roof. A rubber pad was placed between the angle and the RCC roof to minimize friction caused by wind. A simple clay brick counter weight was placed for additional safety. 

For the DC wiring, we got double sheathed DC cables specifically designed for solar purposes. We got the right switches and the wires. 

After all the electrical and structural design, we had aesthetics to care of . Thanks to power  tools from Bosch we did and re-did the wiring (DC and AC) thrice before we were happy with the aesthetics. It took full three days for three people for installation. All in all it was a terrific time designing and installing the system. (A short video is at the end of the post). 

The final phase of the work was to check the system and measure the efficiency. So after about two weeks of installation, we measured the key parameters. A graph of array current and array voltage against time was prepared to study the system. Below are the results. 

Time	Array voltage  (V)	Array Current  (A)	Total Power Produced (W)	O/P current (%)	O/P Voltage (V)	Battery Current (A)	Battery Voltage (V)
09:00:00	54	2.9	156.600	10	231	1.6	51
09:30:00	53	3.2	169.600	4	231	0.1	54
10:00:00	54	5.3	286.200	6	231	0.5	51
10:30:00	59	13.8	814.200	9	231	7.3	56
11:00:00	59	12.8	755.200	5	231	7.9	57
11:30:00	59	12.2	719.800	6	231	7.3	56
12:00:00	60	12.6	756.000	5	231	2.1	56
12:30:00	61	13.9	847.900	7	231	9.5	58
13:00:00	61	15.6	951.600	8	231	2.8	58
13:30:00	65	6.6	429.000	8	231	0.9	54
14:00:00	62	4.9	303.800	6	231	2	54
14:30:00	63	6.5	409.500	5	231	3	54
15:00:00	54	3.1	167.400	5	231	1	52
15:30:00	63	5.7	359.100	6	231	2.3	54
16:00:00	62	4.7	291.400	5	231	1.7	54
16:30:00	54	2.1	113.400	6	231	1.1	52
17:00:00	53	2.1	111.300	4	231	0.7	51

Key metrics from the above table are.

Parameter   Reading   Units   Max instantaneous power produced          951.60  W   Total hours of power production              4.02  Hours   Max Power produced per panel (W)          158.60  W   Total units of power produced              3.82  Kwh   Total power produced      3,821.00  W   Number of hours of power production              7.00  Hours   Power consumed by charger          100.00  W   Power lost during charging          700.00  W   Power available at the battery end      3,121.00  W   Battery to inversion efficiency            70.00  %  Power available at distribution box      2,184.70  W

Maximum units produced                                       2.67       Kwh
 (after all losses)                       

The power production was actually less than expected. There are two reasons for that.

1. The day was not that bright. We had few spells of cloud cover. 

2. There was a tree shadow on one of the panels after 2 PM. Since the modules were made of polycrystalline cells, practically the whole panel will not function if there is shadow on any portion of the panel. 

However for a 1.38Kwp power plant we can easily expect about 3 units of power on a moderately bright day. 

Since it is a grid interactive system, the balance power requirement for the day was met by state utility grid power. 

         Installation Video

Business should not be "Business as usual"

The thought of this post came to me while i  was lying under partial anesthesia on the surgery table of St Philomena's hospital on the 15th of September 2014. I did not have sense of the lower portion of my body. Lying half naked, my legs tied up like a pregnant woman about to deliver, I was waiting for the surgeon to cut out some pus in my ano-rectum area and cut open some part of the tissue so that a fissure there could heal properly. In medical terms the surgery was called "Lateral sphincterotomy". It was a small surgery nevertheless painful.  This was the culmination of bad and stressful life for more than a year.  While i could not have directly cut down the stress levels, i could have been more disciplined in life. 

This was my first encounter with the operation theater. I was told that the this surgery is quite common and its not a cause of worry. Surgery apart, it is the lifestyle which caused my hapless condition. 

For over an year, i am leading a pretty undisciplined life. Very bad food habits, no exercise, plenty of driving, bad sleep habits, pollution and stress both in family and work has taken a very huge toll on my health and hobbies. Health and work obviously has suffered a great deal. But for no plausible reason, i have stopped photography (After publishing my collection early this year), i have not done any travel for pleasure or holiday, my passion for academics has come down, my orthodoxy in religion has almost vanished,  i have stopped following kannada theater so on and so forth. 

The reason for all the above is indiscipline in life and lack of will power. No doubt there has been a sea change in life in the last two years. I am no longer at my will to do all the silly adventures. I have a wife and a one year old who are dependent on me. They take most of my time. 

Not everything is in my control as well. I have lost many dear ones in the last 15 months. My mother and my always witty, selfless and always helpful doctor cousin left me in a span of 5 weeks. My uncle who was like a father figure for me after my father's demise left me just a couple of days after naming his grandson (My son) as "Sri Krishna" in the first week of August this year. 

Nonetheless, being disciplined even amidst the worst onslaught is what makes a man successful. One can never have control over the external factors but one should have determination to stick to his game plan and work towards a goal. Unfortunately i have failed in the latter two so far. 

Running a business is not "So cool" thing to do. Being on your own requires lot of discipline and willpower. Many things will be pulling you in many directions. But staying focussed is the key. 

 "You are so lucky", " Oh its cool to be working from home". These are the typical reactions i get from many people who i meet. They envy me because i work mostly from home. Rather i work at home!!.. 

While it is really good to be working from home, it has its own inherent repercussions. An entrepreneur needs to be very disciplined at work. Working from home many times may become "Working for Home". Household chores are a never ending task. There will be something or the other every day. When we heed too much for the household work, business obviously takes a back seat.
Entrepreneurs are normally creative people . But sometimes, they use the creativity to justify inaction and lethargy since there is no reporting manager on top of him.

One big reason for my bad health over the last one year has been my lifestyle. I tend to do work at odd timings. I haven't taken care of my diet. I heed too much for domestic chores and concentrate too little on professional deadlines and plans. Creativity has taken a back seat since i am more involved in household work.

Kids are awesome. They really are. My one year old son is super cute and super naughty. I can play with him all day and all night. But playing all day also means losing all day of business. Since i work from home, my son always wants to come to me while i am working. He does not like when i ignore him. I cannot go out of the house(office) when he is awake.

"Business" for entrepreneurs is not "Business as usual". Entrepreneurs are normally creative and enthusiastic people. They always want to do new things and experiment. The key driver for their creativity is the discipline. Once the discipline is gone in life, creativity goes down and business suffers. For sustenance, the business becomes business as usual.

Out of my experience of running a very small company pretty successfully for sometime which earned me a lot of social capital and , also failing quite badly in the last 12 to 14 months, i would like to pen down a few guidelines for myself and for other people going through a similar phase of life.

• Having discipline in work is very important. To be more precise, one needs to have a very clear distinction between professional and personal life. There must not be any overlap in time allotted for each respectively.
• If possible, have a separate office however small it is. But the office must be neat.
• Keep the family away from business and office. Resist the temptation of playing with kids at office hours. 
• Have a good routine. Start up entrepreneurs have a lot of travel to do. But one must keep in mind that health suffers during travel. One must have control over eating outside food. Fast food can kill you faster. 
• Starting the work early helps leaps and bounds. I do not know if it is by design of luck, but most of the project meetings and negotiations that i have had in the early hours in the morning have invariably clicked. 
• Another important observation is that whenever i have been late for the meeting, those projects have not clicked. So a priceless lesson is to be on time for every meeting, be it with clients or with subordinates. 
• Stress and restlessness are the biggest enemies for entrepreneurs. One must find out a way of overcoming it. One nice way which has started working for me is music. Few weeks back i started learning Mridangam, something i wanted to do for many years now. I am very bad at it right now. But learning something new , particularly music which is both an art and science has been a very refreshing experience. 
• Most importantly life for an entrepreneur should never become "Business as usual". It is the most dangerous thing that could happen which will kill his creativity. One must keep on experimenting, creating, innovating and enjoy his or her evolution. 

I am completely aware that many things are easier said than done. I am also trying to incorporate many of the above into my life.

This post is my acknowledgement to my indiscipline, weak determination and very bad health, and my resolve to reverse it.  I wrote the above post to reinvent myself and renew many of my interests and passions.