In many cases, the component decisions for rooftop solar power plants are made by the installer and not by the owner of the solar power plant.

If you have chosen your installer with care, trusting the installer’s decision is indeed correct as he/she has expertise on solar power systems. But it still is a good idea for you to understand some critical aspects of the main components of a rooftop solar power system.

Details are provided for the following components

Inverters

There are three main types of inverters – central inverters, string inverters and micro inverters

Central inverters, as the name suggests, are inverters which could have large capacities, so much that just one inverter could suffice for the entire output of the solar panels. String inverters are relatively modular, so instead of having one 100 kW central inverter, you could opt for 4×25 kW string inverters. While string inverters cost a bit more than the central inverters, they have the advantage of lesser maintenance requirements and lower effect on output in case of inverter failure as such failure affects only one of the multiple inverters. Micro-inverters, as the name suggests, are small inverters that can be fitted at the solar panel level. These are most costly than both the string and the central inverters, but they provide the added significant benefits over these.

Do check with your installer on all the three types of inverters and check with him why he prefers a particular type of inverter over another.

Batteries

Most solar rooftop installations worldwide still use deep cycle lead acid batteries, though some of the emerging   solutions have   started using Li-ion batteries and other high-energy-density batteries.

Batteries are a critical element to your rooftop solar solution, as this is one component that could require constant replacement (lead acid batteries will need to be replaced every 4-5 years). While Li-ion batteries have a much longer lifetime, they cost much more than the lead acid batteries. Hence, it is important that you have a discussion with your solar installer on which of the battery types he is choosing, and why.

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Panels

Solar panels seem to be the easiest choice to make, and usually they are

Good quality solar panels usually come for 25 years and longer and work well, according to the specifications made by the manufacturer.

But you might want to dig up a bit more about the solar panels as well before you settle down on the final choice.

Today, almost all rooftop solar installations use crystalline solar panels, and we feel it is the right choice too. While the main alternative, thin film solar panels, has its merits, when it comes to rooftop solar power plants, crystalline solar panels are the better choice. Why? Because, except in very select cases, crystalline solar panels have much higher efficiencies than thin film solar panels. Higher the efficiency of solar panels, lower the area you require per kW. Thus, for rooftop solar, where the space is many times a constraint, it will be a better idea for you to go for crystalline solar panels.

But even within crystalline solar panels, you will need to decide on whether to go for monocrystalline panels (which are higher cost and higher efficiency) or polycrystalline (relatively lower cost and relatively lower efficiencies than monocrystalline panels). This decision again will involve your evaluating the importance of accommodating more kW within the existing space at higher costs.

Mounting Structures

The type of mounting structures that are suitable for you depends on the roof structure and the roof material. While the installer is perhaps the best person to decide on the precise type of mounting structure design based on your roof, do spend some time with the installer and specify some of the aspects such as whether you require a penetrating mounting structure or a mounting that does not penetrate your roof and other such requirements.

To know more about component selection for your rooftop solar power plant, read Solar Mango’s India Rooftop Solar Advisor

Other Balance of Systems

Other balance of systems comprise cables, junction boxes, connectors. Monitoring systems and the like. These are not as critical as the above from a decision making point of view. However, do spend some with your installer to understand some of the key specifications of each of these balance of systems.

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