solar PV rooftop system study and learn

In a solar rooftop system, the solar panels are installed in the roof of any residential, commercial, institutional and industrial buildings. This can be of two types
(i) Solar Rooftop System with storage facility using battery, and
(ii) Grid Connected Solar Rooftop System.

In grid connected rooftop or small SPV system, the DC power generated from SPV panel is converted to AC power using power conditioning unit and is fed to the grid either of 33 kV/11 kV three phase lines or of 440/220 Volt three/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 systems generate power during the day time which is utilized fully by powering captive loads and feed excess power to the grid as long as grid is available. In case, where solar power is not sufficient due to cloud cover etc., the captive loads are served by drawing power from the grid.

Such rooftop systems can be installed at the roofs of residential and commercial complex, housing societies, community centers, government organizations, private institutions etc.

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

Subsidies are available from multiple channels for setting up Rooftop PV projects.
Subsidy/Support from Central Government through MNRE: 
Capital Subsidy at the rate upto 30% of the benchmark cost for general category states (upto 70% of the benchmark cost for special category states i.e., North MNRE PV Rooftop Cell, pvrooftop@gmail.com, Supported by EU, DCI/ASIE/2014/343-602 LOT 1 3/4 Eastern States including Sikkim, Uttarakhand, Himachal Pradesh, Jammu & Kashmir and Lakshadweep, Andaman & Nicobar Islands) is being given in residential, institutional (hospitals, educational institutes, etc.), social sector etc.
Commercial and Industrial sectors will not be eligible for the above mentioned subsidies.
Government Institutions including Public Sector Undertaking (PSU) shall not be eligible for subsidy; instead they will be given achievement-linked incentives/awards.
Subsidy/Support from State Government through State Nodal Agencies (SNAs):
Subsidy support is also available in various states. The percentage of subsidy varies according to the state policies.

There are provisions of concessional import duty/ excise duty exemption, accelerated depreciation and tax holiday for setting up grid connected rooftop power plants.

Department of Financial services has instructed to all Public Sector Banks to encourage home loan/ home improvement loan seekers to install rooftop solar PV plants and include cost of system in their home loan proposals. So far, nine PSBs namely Bank of India, Syndicate Bank, State Bank of India, Dena Bank , Central Bank of India, Punjab National Bank, Allahabad Bank, Indian Bank and Indian Overseas Bank have given instructions to extend loan for Grid Interactive Rooftop Solar PV Plants as home loan/ home improvement loan.

CAPEX Model : Here, the entire system is owned by the rooftop owners. Responsibility of O&M for the system lifetime (25 years) is also with the rooftop owner. Developer is responsible for installing the system and initial 2 years O&M.
RESCO Model : Here, the entire system is owned by the developer. Responsibility of O&M for the system lifetime (25 years) is also with the developer. Rooftop owners may consume the electricity generated, for which they have to pay a pre-decided tariff on a monthly basis. Excess generation may be exported to the grid, subject to availability of requisite state regulations.

For consumers that have adequate manpower/expertise for O&M, rooftop access concerns, availability of funds upfront, CAPEX model is better. Consumers in states that have net- metering regulations can take benefit of the same in case they have 4/4 MNRE PV Rooftop Cell, pvrooftop@gmail.com, Supported by EU DCI/ASIE/2014/343-602 LOT 1 substantial excess generation.
On the other hand, consumers who prefer not to take responsibility for the system O&M, do not have rooftop security concerns and prefer to pay on a monthly basis rather than bulk upfront payment may choose to go for RESCO model.

The grid connected rooftop system can work on net metering basis wherein the beneficiary pays to the utility on net meter reading basis only. Alternatively two meters can also be installed to measure the export and import of power separately. The mechanism based on gross metering at mutually agreed tariff can also be adopted.

In feed-in-tariff the Government offers a tariff for purchase of the solar power generated from such plants.

(i) States should have conducive solar policy to allow the grid connectivity.
(ii) State Regulators have issued tariff order for appropriate tariff, netmetering/feed-in tariff and the grid connectivity, and
(iii) The Distribution Companies agree to allow grid connectivity and purchase the electricity on feed-in-tariff or through net metering arrangement.

Individual household consumers can get off-grid rooftop systems installed on their roofs through MNRE channel partners to avail government subsidy. The list of MNRE channel partners can be found at http://mnre.gov.in/filemanager/UserFiles/list-of-Accredited-Channel-Partners-Rooftop-Gridconnected.pdf

(i) Electricity generation at the consumption center and hence Savings in transmission and distribution losses
(ii) Low gestation time
(iii) No requirement of additional land
(iv) Improvement of tail-end grid voltages and reduction in system congestion with higher self-consumption of solar electricity
(v) Local employment generation