Installing roof top solar PV systems on your building


Installing a solar Photovoltaic system require a basis understanding of technical, economic and regulatory aspects to take a call for the viability of these systems. Installing a solar PV system is different than installing a typical solar water heating system as it has many sub systems such as inverter selection and net metering etc. PV systems have limitations that they produce power intermittently because they work only
when the sun is shining. It is difficult for PV systems to furnish all the power you need, and are typically used in conjunction with utility-supplied electricity.
Is your roof good enough to install solar PV?
The best orientation for a PV system is on a south-facing roof; hence it is important that your roof has a south facing option available to install solar PV systesm. A flat horiezontal roof is also elligible for solar PV facing clear sky and having shadow free area.
The amount of roof space needed for a roof top solar PV systems is determined on the basis of your selection of your PV generating capacity. Typically you require about 100 ft2 area to house a 1 kW solar roof top system.
How much does a roof top PV system produce?
PV systems produce the most electricity during the October to march when the sun is shining. Energy production will vary, of course, depending on geography and climate. A typical 1 kW roof top PV system will produce about 1600-2000 kWh in a year depending the location. If we consider a typical household demand of 12000 Units a year, then a typical 5 kW roof top system will meet about 60-70% of the household annual electricity demand.
Is solar PV really expensive?
PV-generated electricity is still more expensive than conventional grid electricity, however it all depends on how much is the opportunity cost of displaced electricity. If the displaced electricity is a combination of grid and DG based electricity, in that case the cost of displaced electricity is about 9 Rs/unit which makes solar PV system much more attractive to the roof top installer. Although the utility grade solar pv is now costing about 80-90 Rs/Wp, the rooftop PV systems will cost about 120-150 Rs/Wp due to economy of scale. Considering a cost of 150 Rs/Wp for a typical roof top system a 10 kW roof top system will cost about 15 Lac. The building owner is also eligible for 30% capital subsidy (4.5 Lac) and accelerated depreciation 9about 4 Lac). Hence the building owner hes to spend about 40% of the total cost of the systems, which makes PV attractive in terms of low capital cost.
How do I get finance for my roof top system?

Government of India has launched a low interest based financing scheme for roof top systems and it is available from many commercial banks and also through NABARD. The interest rate charged for the roof top systems is of the order of 5%.

What is net metering?

Net metering alows a roof top solar PV system owner to connect his solar PV system to the grid and sell its surplus electricity to the grid. Net metering allows electricity meter to spin forward when electricity flows from the grid into your building, and backward when your system produces surplus electricity that is not immediately used. Your excess electricity is “banked” on the utility grid. Currently CERC is under developing guidelines for net metering for roof top systems.

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