The Indian government is working on becoming a serious player in the renewable energy game. By 2022, it hopes to achieve the target of 100 gigawatts in solar capacity.

Few Facts: 

• As of March 2019, India had already installed 28 GW of solar capacity, four times more than the previous year. Source – IEEFA.org
• By the end of 2019, India’s solar rooftop power generation capacity was 4375 mW, more than 70% compared to 2018. Source – Business Standard

Why do residential societies need to ride the growing wave of renewable energy? We’d be lying if we said that lower light bills aren’t the main reason. Societies in Mumbai, Pune, Delhi and Bangalore have successfully reduced their light bills by 65-70% after installing solar panels on the rooftops, saving lakhs in electrical bills annually.

At a community and national level, every society that adopts renewable energy alternatives helps reduce global negative environmental impact.

What is a solar panel?

Technically made of smaller photo-voltaic cell units, solar panels generate Direct Current (DC) by allowing ‘photons’ or the light from the sun to separate electrons from atoms. The solar inverter takes the electricity from the solar panels and converts them into Alternating Current (AC) electricity which is supplied inside the households through power grids.

Why use solar panels in apartment complexes?

• Reduced electricity bills
• Common spaces, lifts, water pumps can be powered without using main supply
• Curbs negative environmental impact
• Long term investment
• Lower maintenance costs
• Easy installation even post apartment construction
• Safe and recoverable
• Has strong government support

Types of solar panels for residential buildings

There are two main types of PVs currently in use:

1. Monocrystalline

These are made of single-crystal of pure silicon, thereby allowing more room for the electrons to generate more electricity from the light of the sun.

2. Polycrystalline

Fragmented silicon slabs (not pure silicon) are melted together to form wafer panels. These are also known as multi-crystalline solar panels.

Difference between mono and poly panels

Concentrated PV panels (CPV)

Available in low, medium and high concentrations, CPVs are considered the future of solar energy with curved mirror surfaces and lenses placed strategically and are recommended to be integrated into the building at the design stage.  Even a low concentration CPV panel can produce 2x more energy than regular PV panels whereas multi-junction HCPV is known to be 40% or more efficient.

Installation and cost

Equipment needed for installation are solar panel modules, mounting/racking system, electrical wiring to connect with the general power system, solar inverter, (charge controller and lead battery for off-grid systems).

Grid-tied vs off-grid solar systems

On-grid systems are connected to the local power grid and have a lower installation and maintenance cost. If your system produces more energy than you use, the surplus is fed into the main system and turned into credit which you can cash out. A net metering system is installed to track usage which eliminates the need for battery storage or back-up. But the supply is disconnected during power outages.

An off-grid system is self-sustaining and independently installed from the main supply and uses batteries for power storage. They are perfect for places with lack of electricity grid or inconsistent supply. Maintenance is required for the generator and battery, not so much for the panels. 

Depending on the type of solar system (off-grid or on-grid), sq feet and generated watts, prices will vary from one manufacturer to another.

Off-grid system for an apartment complex approximation

On an average, an off-grid system installation would cost Rs 800,000 to Rs 1,60,000 lakh including batteries (1-2 KW). However, the government provides a 30% subsidy for residential rooftop solar panel installation. Additionally, there is 80% accelerated depreciation offered by the rules of the Income Tax Act. However, if more kW are required, the price can go up. For instance, a 10 KW system can cost up to Rs 7,00,000. However, an on-grid 10KW system can cost around Rs 4,50,000 which means that the lowest 1KW can cost between Rs 65,000 to Rs 75,000 depending on types of panel and inverters.

Frequently Asked Questions

1) What’s the warranty period of solar panels?

Minimum 15 to a maximum of 25 years. Installation warranty is 2-5 years.

2) Should I use Thin Film solar panels for my apartment building?

These are less expensive but short-lived and space-consuming, thus generally not recommended for residential buildings.

3) What certifications should I be aware of?

Solar panels should be approved by MNRE (Ministry of New and Renewable Energy), and fulfil requirements of IEC 61215/ IS 14286 and IEC 61730 Part I.

4) Which are the types of solar inverters?

String inverters are the most commonly used residential solar inverters. However, microinverters + power optimisers are also gaining traction.

5) What’s a smart solar inverter?

They have algorithms for real-time monitoring through an app, usage pattern detection and predictive data insights on demand and supply.

6) What are the rooftop requirements for solar system installation?

Best positioning for maximum sunlight is facing south. The roof should be repaired if damaged and be sturdy enough to bear the load. According to the government, a grid-tied 1 kW rooftop system requires 10 sq metres of shadow-free area. Click here for government requirements for grid-connected rooftop systems.

7) How do I apply for a grid-connected rooftop solar system?

You can make an online application at https://solarrooftop.gov.in/ for Delhi and www.mahaurja.com for Mumbai. Other states also welcome online applications. 

8) How do I select the vendor to get Central Financial Assistance?

According to the government, the beneficiary should select a valid selected vendor of the State Nodal Agency through bidding, empanelment, rate contract against MNRE sanctioned capacity.

It’s imperative that you conduct enough research on configuring the type of solar system you wish to install by comparing prices, services and overall cost-effectiveness offered by private manufacturers providing off-grid services as opposed to grid-connected rooftop systems.

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