About Solar Rooftop

Solar PV system comprises of electrical and electronic equipment such as solar modules, inverters, cables, switch gears etc. When all these components are combined together and placed in open space facing sunlight, the system starts generating electricity. The electricity thus generated can be stored in batteries or used directly by the consumer. If consumer is not storing electricity and not able to consume complete power generated by solar PV system, he can also feed the excess power to the utility grid. The function of each component of solar PV system is explained below along with images.

  • SPV Modules: It converts solar energy into electrical energy. There are primarily two kinds of PV modules:
    • Crystalline
    • Thin-film
  • Inverter: It converts the DC power produced by PV modules into AC power. The AC power is then either injected directly into the grid or consumed onsite
  • Balance of System (BoS): All components other than the PV modules are termed as balance of system. The components included in BoS are:
    • Mounting Structure: It is used to support and hold the PV panels. The structure is designed depending on the roof type, structural strength, cost, wind loads, etc.
    • Wiring and cabling: DC cables are used to connect solar panels and connect the string with inverter.
    • Safety equipment: Safety feature protects the solar system from being damaged or harming people during the events such as lightning event, power surge, and malfunctioning equipment. The safety equipment consists of safety disconnect, grounding equipment, and surge protection.
    • Bi-directional Meters: Bi-directional meters are used to keep track of the electricity that solar system produces and the electricity that is used from the grid.

There are two types of SPV systems that are most common:

Off-grid SPV System

Off-grid SPV systems are designed to operate independent of the electric utility grid and are generally designed and sized to supply certain DC and/or AC electrical loads. These types of systems use solar panels to generate electricity during morning time, and the electricity generated is stored in the battery to be used during the night time.

Grid-Connected SPV System

A grid-connected rooftop SPV system generates electricity that can either be injected directly into the distribution grid or used for captive consumption at the premises of the installation.

Costs of a Grid-connected Rooftop SPV System

The capital cost of grid-connected SPV systems ranges from '65/watt to 100/watt'. The cost for small size solar plant is high but as the size increases, the cost of plant comes down.

  • The cost of the plant is inclusive of transportation, installation, connectivity, civil works, and operation and maintenance (O&M) for five years.
  • The typical warranty period for the solar panels is 25 years and, for inverters, it is 7–10 years.

Advantages of grid connected solar rooftop solar rooftop

Benefit to consumer

  • Low cost of electricity generation – Cost of power generated from solar is around Rs. 5.8–6.5/kWh. Most of the industrial and commercial consumer are paying higher tariff and the cost of electricity is increasing at a rate of 3%–4% every year. It is beneficial to install solar rooftop that will give clean and cheap source of electricity in long run.
  • Cheaper than diesel power- The cost of power generated from diesel is around Rs. 16–18/kWh which is much higher than solar electricity cost. Installing solar reduces the load form diesel generator and reduces the consumption of diesel.
  • Accelerated Deprecation benefits- Accelerated depreciation of 80% is available under the Income Tax Act for Solar Photovoltaic Systems. This can provide significant tax savings to profits making entities.
  • Central and State Government subsidy- Central government is providing 30% subsidy for residential, institutional, and social consumer (not for profit institution). MNRE is providing achievement-linked incentive for PSUs, Central and State Government building and establishments for the installation of solar rooftop. Gujarat State Government is also providing addition subsidy of Rs. 10 ,000/- per kW limited to maximum of Rs. 20 000/- over and above MNRE subsidy for residential category of consumer
  • Payback Period- The payback period for the plant is around 5–7 years. In the initial 5–7 years, the consumer is able to recover the cost of solar plant through savings in electricity bills. After this period, consumer uses free electricity and saves money in electricity bill for next 18–20 years.

Benefit to Government

  • Electricity is consumed at the point of generation hence saving in transmission and distribution losses
  • Low gestation period as a plant of 1 MW solar rooftop can be installed in a month time
  • No requirement of land, which is a scarce resource in city
  • Improvement in tail end grid voltage and reduction in system congestion with higher consumption of solar electricity

Benefit to Society

  • Local employment generation
  • Pollution free source of electricity, which ultimately help in reduction of CO2 emission

Why to Install Grid-Connected Solar Rooftop?

The reasons for industrial/commercial sector and domestics going for rooftops is primarily driven by two factors.

Unreliable supply of grid power

  • Frequent load shedding as well as power quality issues

Cost of power

  • Increasing cost of grid power
  • Very high cost of diesel power