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FAQs on Solar Photovoltaic System

What are solar rooftop systems?

A solar  rooftop  photovoltaic (PY)  system converts  sun's  light  energy into electricity energy through solar panels mounted  on  the  rooftop  of  a  building. As light hits the solar panels, the solar radiation is converted into  direct  current  (DC).  The  direct  current  flows from the panels and is converted by the solar inverter into alternating current (AC) used by local electric utilities. The plant can be connected to the grid or can be designed to be off-grid. Components  that  are  required  for  rooftop  solar installations are: photovoltaic panels (to convert solar sunshine  into  direct  electricity),  batteries  to  store electricity when power is not required and the sun is shining, inverters to convert direct current (DC) into AC, cables and other miscellaneous items like junction boxes, earthing, lighting arrestors and conduits. Panels account for about 50 per cent of the total cost

Solar panels are increasingly being installed by homeowners wishing to take advantage of a system that produces green energy and insulates them from rising energy prices.A rooftop solar power system can provide us with a clean and efficient source of energy for the home, saving us money and reducing dependence on the power grid. If you are worried about the amount of money spent in installation, just know that it will pay you back in just six to nine years in terms of savings in monthly bills. The useful life of a typical solar power plant is considered to be 25 years. The Indian government has committed to generate 100 GW of solar energy by 2022. By choosing solar, you make an investment you can be proud of and show your commitment to clean, renewable energy. In this report, we explain the common types of solar electric systems, the parameters on the basis of which one may choose the one that best suits their requirements, and other points that may concern the consumer.

Why Solar Rooftop?
  • Your   vacant   rooftop   space   will   be fruitfully utilised.
  • Your electricity bills will be reduced.
  • This will be your contribution towards reducing dependence on grid.
  • This will also contribute in reduction of CO2 emissions.
Types of Solar Electric System
The  common  types  of  solar  electric  system  are described  here.  Each  has  distinct  applications  and components.
  •  Grid-connected
In this system the solar panels are connected to your  local  utility  electrical  grid.  A grid-connected system consists of:
  •   Solar panels mounted on the roof
  •   An inverter to convert electricity from DC energy into AC.
  •   A  junction  box  that  connects  the  solar-panel wiring to the breaker panel on the home
  •   A power meter that displays how much power the home produces and uses
  •  Grid-connected with battery backup
Very  similar  to  the  grid-connected  system,  this system  adds  a  battery  bank  to  collect  the  power generated from the solar panels. Power stored in the batteries can be used during outages. The battery bank collects power produced by the solar panels, sends it to breaker box, and then into the house power system.
  •  Off-grid or standalone
Off-grid systems are not tied to any utility power lines  and  are  most  common  in  remote  areas  where connecting to the utility grid is more expensive than purchasing  an  off-grid  system.  In  off-grid  systems, the solar electric system represents the home's main source of power. Batteries store unused solar energy for  use  at  night.  Generators  and  other  backup  fuel sources  are  sometimes  used  as  backup  power  when the solar power stored in the batteries is not enough to meet household needs.
What is a grid-connected rooftop solar PV system?

In    grid-connected    rooftop,    the    DC    power generated from the solar photovoltaic (SPY) panel is converted into AC power using a power conditioning unit  (PCU)  and  it  is  fed  to  the  grid,  either  of  33 kY/11  kY  three-phase  lines  or  of  440  volt/220  volt three-phase   lines/single-phase   line,   depending   on the  capacity  of  the  system  installed  at  institution/ commercial establishment or residential complex and the regulatory framework specified for respective states. These SPY systems generate power during the daytime which is utilised fully by powering captive loads and feed excess power to the grid. Where solar power is not sufficient due to cloud cover, etc., the captive loads are served by drawing power from the grid.

Where can such solar plants be installed?

Such   SPY   systems   can   be   installed   at   the rooftops  of  residential  and  commercial  complexes, housing  societies,  community  centres,  government organisations, private institutions, etc.

How much roof area is required to set up the grid-connected rooftop solar PV system?

A 1 kW rooftop system generally requires 12 sq. metres  (130  square  feet)  of  flat,  shadow-free  area (preferably   south-facing).   Actual   sizing   depends also  on  local  factors  of  solar  radiation  and  weather conditions and shape of the roof.

Do you need a contractor or is it a do-it- yourself (DIV) thing?

You  need  to  install  the  system  through  a  state nodal agency or an MNRE-empanelled agency (that is, contractor) for getting MNRE subsidy.

What are the other fiscal benefits available for installing grid-connected rooftop solar PV power plants?
  •  Generation-based incentive (GBI)
  •   Exemption on open access as provided by DERC
  •   Exemption on conversion charges for residential consumers
  •   Exemption on wheeling charges, banking, cross- subsidy and other charges for installing SPY power systems installed under net-metering scheme.
  •   Excise  duty  exemption  as  provided  by  Ministry of Finance, Government of India, for installing a minimum 100 kWp grid-connected rooftop SPY power plant
  •   Accelerated depreciation benefit and tax holiday


Is any Central Financial Assistance (CFA) provided for residential consumers by MNRE for installing grid-connected rooftop solar PV power plants?

Central financial assistance (CFA) of 30 percent of the benchmark cost or as applicable from time to time  is  provided  for  installation  of  grid-connected rooftop solar power plants, of capacity 1 kWp up to 500 kWp. This is available to residential consumers (irrespective of the electricity connection).

What are the requirements for installing grid- connected rooftop solar PV power plants?
  •  A   vacant   roof   area   of   10-12   sq.   metres   for installation of 1 kWp SPY system
  • A three-phases/one-phase      supply      service connection
  • Mandatory safety precautions/features installed as per the norms
  • A single   bi-directional   meter   for   export   and import
  • Standard equipment as per the norms of MNRE
  • Ownership permission and necessary documents
What is the annual energy generated from a 1 kW solar power plant?
The usual benchmark for energy generated from a 1 kW solar power plant is 1,500 units per annum. The amount  of  actual  energy  generated  depends  on  both internal and external factors. External factors that are beyond the control of a solar power developer can include these: a) number of sunny days, b) solar irradiation, c) day temperatures, d) air mass, and e) location.
What are the factors affecting generation?

a) Plant location,
b) quality of equipment used,
c) workmanship
d) module cleaning
e) operations and maintenance (O&M) activities

Sources: EEREM/Home/

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