Roof Top Solar PV System for residences - my experience

I noticed some discussions on Roof Top Solar PV System for residences. I would like to share my experience and assumptions.

I have installed a SPV system on my roof top as a back up to grid supply 4 years ago, and is functioning satisfactorily although some improvements in the overall operation of the system is desirable and achievable.

Assumptions first:

1. Renewable energy sources are the future; and solar power has the most advantages;
2. Conventional power sources are fast depleting and getting costlier; social and environmental cocerns with these sources are huge and cannot be ignored any longer. Their real cost to the society is much more than what we see now as electricity prices.
3. In order to make use of SPV systems work effectively, the electricity demand has to be managed carefully.  Usage of heavy duty appliances such as fridges, ACs, washing machines, water pumping, electric iron box, etc should be avoided as far as possible OR carefully managed. My requirement was only for lighting, PC, TV, and cell phone recharging.
4. Some financial risk taking is involved for individuals if we want to hasten the wider use of these renewable energy sources.
5. Living in a village a decent backup for the grid power was necessary for me to be able to use my PC at any time.
6. Also I wanted to demonstrate to otheres (especially the authorities: I demonstrated my SPV system to the state energy minister in 2009) the efficacy of these systems.

Experience:

• a. A system of capacity  [50*2 watts, 125 AH battery, control cubicle (for charge controlling, changing over from grid to solar and vice versa, preference to charge the battery either from grid or from solar, a switch and few indicating lamps), iron stand, testing and commissioning all included] was quoted for about Rs 80,000 in 2008. Warranty of 20 years for the panels, and 5 years for the battery was obtained. I held back about Rs. 10,000 as performance gaurantee. The supplier never asked for this money; so huge must be the profit.
• b. The system is functioning satisfactorily for my uses: CFLs, TV, PC, two small table fans, two small table lamps, and power sockets for charging the cell phoness. System is connected to the AC wiring of the house, and hence the soalr power can be used anywhere in the house.
• c. Once the battery is charged fully (say about 4 hours of sunlight), I can manage without grid supply for one whole day.  Supply changeover from grid to solar and vice versa isgenerally smooth and is almost un-noticeable.
• d. I also have a decent after-sales-service as can be expcted in a rural environment.
• e. Since the system is modular in nature no. of panels can be added; accordingly the cable and control cubicle may also need to be changed.

Observations:

• i) The price for a simialr system has come down by more than 50% in 2012.
• ii) The system can be very useful in most parts of Karnataka including Bangalore. There will be some charging of the battrey even on cloudy and rainy days, but to a reduced extent;
• iii) If we know our load requirements well and are ready to accept small sacrifices SPV systems can provide good service.
• iv) Most residences will not need more than 2 kW capacity fo the system, if we manage the usage carefully
• v) Best usage is to make use of all the solar energy generated during day time; and keep the battery energy only for lights, TV and PC for the night.;
• vi) There can be no doubt that responsible usage of the scarce energy resource we have cannot be compromised. We have to decide whether some of the appliances such as fridge, AC, washing machine, micro wave oven etc. are indispensable.
• vi) Small size water pumping sets should be of problem. Best to sue them during day time.
• vii) Cost of 1 KW SPV system can be less than Rs. 2 lakhs; one has to shop around for best buy. Bangalore may offer many good options.
• viii) Before finalising the buy it is advisable to check with one or two who are already using the system; preferanly consult a professional
• iX) Since the system is modular one can go for a smaller systen to start with, and decide to updgrade depending on one's experience and needs
• x) There can be no doubt with more and more people opting for sush systems the prices will come down further and better systems will be made available.
• xi) Subsidy may be available for sytems of capacity  more than 1 kW; need to very with KREDL, Bangalore and MNRE, Delhi.
• xii) As always the pioneers will have to bear some extra costs and risks; but that is why they are called as pioneers.
• xii) As a thumb rule about 1 kW of SPV can be installed in a surface of 60 Sq. ft. Even if it is 100 Sq. ft per kW it is adeqaute in most cases. A  house built on a 30*40 Feet site can offer a surface of more than 500 sq. ft. Hence getting a minimum of 5 kW of solar power capacity is feasible on most of the roof tops.
• xiii) Installing SPV for a group of house will become little bit more complicated not only in the cost, design and operation, but there may be licensing issues to be considered. some one has to take the ownership of the entire system and may have to get license from the electricity regulator. I am not sure about this and hence need to be checked with KERC, Bangalore.