Solar panels consist of a series of solar cells placed together in arrays to generate electricity from the sun. A rooftop solar system is one in which solar panels are mounted on the roof of residential, commercial, institutional or industrial buildings to generate electricity.

Energy demands of the host can be met by a rooftop solar system and any excess energy can either be stored in a battery or be transmitted to the grid.

Solar panels can be installed on both sloped as well as flat roofs. On the flat roofs, additional mounts and racks are needed in order to angle the panels for higher efficiency. In terms of the rooftop material, reinforced concrete, metal and asphalt shingle roofs are the most preferred for solar panel installations.

The material should have a high strength to weight ratio, be durable and energy efficient. For a complete assessment, consult a specialized solar EPC contractor.

A solar project is made to last for about 25 years. Therefore, before installation, it is essential that a structural evaluation of a roof is carried out to ensure it can withstand the panel weights.

On average, a solar panel weights around 1-2kg per square foot, which can be supported by most roofs. The main parameters to be considered while making this assessment are:

• 1. Rooftop Material
• 2. Distribution of solar panel weight
• 3. Balancing of solar panels across the roof

Metal roofs are considered especially good for rooftop installations because they have a high strength to weight ration. Asbestos and Plastic would not be ideal.

Yes. Asbestos and plastic roofs are not well suited for solar project installations. They are lightweight and may not be able to provide support to solar panels. Moreover, asbestos sheets have not been used for the contruction of rooftops in the recent past.

Thus, they may rupture and need replacement before the 25 years for which solar panels are usually installed. This may mean you will need to bear the additional costs of removing the entire solar PV project, installing another roof and then re-installing the solar modules.

It is true that solar panels work most efficiently when exposed to direct sunlight. However, these panels utilize both visible light and infrared light to create electricity, both of which are present during cloudy or rainy days as well. Thus, even during full fledged monsoon season, the output of your solar panels will not be zero.

The efficiency of a solar panel on a cloudy or rainy day is dependent on the material utilized in the panels as well as the angle at which panels are installed. On average, panels manage to maintain 50% efficiency even on a rainy day.

Given the current structure of solar PV projects, going completely off-grid once an installation is complete would not be possible. In order to rely completely on the sun for all energy needs one would have to:

• 1. Install a battery pack which would be used to store energy. This stored energy would be used to meet a consumers needs during times of low sunlight and post sunset, when there is no sunlight. Batteries increase the overall cost of the project, need addtional maintenance and must be replaced every 4-5 years
• 2. Ensure the reference voltage is not obtained from the grid. Most inverters in solar PV projects are designed to use grid power as reference voltage. This reference is needed because, during the day, the amount of sunlight falling on the solar panels varies. This means that power output of a solar panel fluctuates during the day and this can harm appliances powered by solar. Therefore, the solar project inverter needs another source of power to get a reference voltage it can match with.

Thus, because of the following reasons one cannot go completely off-grid:

• A. power generation via solar fluctuates during the day and also across days and months
• B. consumers cannot match their energy need timings with power generation timings
• C. currently, inverters in solar projects use the grid for reference voltage

There are two possible reasons why solar panels may not operate during power cuts:

• 1. Dependence on the grid for reference voltage - If the inverter in the solar project has no other means of obtaining a reference volatge, like through a diesel generator or battery, and relies entirely on the grid, then solar panels will noto function during a power cut
• 2. Anti-Islanding - During a power cut, a part of the grid is not energised and this part is referred to as the island. If during this time, the solar project pumps energy into the grid, it could lead to electrocution of the people working at the grid. To avoid this, inverters tend to turn off the solar power system during power cuts.

The scenarios in which one would utilize a DG set in conjunction with a solar project are:

• 1. During power cuts/load shedding
• 2. Absence of a regular grid based electricity connection

In the first scenario, if power cuts are during the day when sunlight is in abundance, one's fuel costs will reduce substatially. If, however, there tend to be long hours of power cuts, especially during time periods when the solar cells cannot generate electricity, the monetary benefits could vary and should be properly evalutated before any decision is made. In the second scenario, there would be a definite benefit resulting from lower fuel costs.

The solar industry has developed a mechanism through which they classify solar panel manufacturers into three different tiers based on a variety of different factors such as experience, manufacturing scale, durability and quality of the products, etc.

Tier 1 manufacturers are supposed to be the best followed by tier 2 and then tier3. Just because the manufacturer is tier 1 doesn't imply that every solar panel produced by that firm will be of the highest quality, but there is a positive correlation between tier of company and solar panel quality.

In most studies we have read so far, the list of top 10 solar panel manufacturers tends to be dominated by Chinese players. Thought China produces a lot of junk products as well, the panels from tier 1 companies can be trusted.

Tier 1 companies use the best grade of silicon, are vertically integrated - they make their own cells and wafers, control the manufacturing process with advanced robotics and invest heavily in R&D. Thus, they tend to provide the best products at reasonable rates.

Panels from Tier1 companies, though a little more expensive, are worthwhile in the long run because:

• 1. They will be more durable and in the long term, prove to be more cost effective
• 2. They tend to come with a performance warranty from re-insurer