A practical guide to selecting solar panels

How to choose solar panels for your home, office, apartment, or educational institution.

A short history

In a world where most energy comes from non-renewable resources, solar panels have been one of the great pillars of renewable energy technology.

Solar panels are often associated with new-age technology. But scientists have been working with solar cells for nearly 200 years, now. Today, with rapid advances in technology, solar PV is a worthy recipient of this progress.

Types of solar panels

Hundreds of companies are manufacturing solar panels now. With different solar panels available on the market, it is difficult for one to distinguish them. In this simplified guide, to help make the right choice, the focus is on the types of solar panels, their quality, brands available, and the latest innovations.

Solar panels fall under one of mono-crystalline, poly-crystalline, or thin-film. These panels vary in their manufacturing, appearance, performance, cost, and the kind of installation. They all work on the same principle of the photovoltaic (PV) effect – the creation of voltage and electric current upon exposure to light.

Silicon-based solar panels

Silicon is the building blocks of solar cells. The silicon purity determines the efficiency of the solar panels. Solar cells with perfectly aligned silicon molecules are more efficient at converting solar energy into electricity. However, enhancing the purity of silicon is an expensive process.

Mono-crystalline solar panels

Average efficiency range: 16% – 20%
Cell manufacturing process: Wafers cut from blocks of highly pure silicon crystals
Appearance: Uniform surface, solid black
Pros:
high efficiency
reliable performance in high temperatures and shaded conditions
ideal for rooftops that have space constraints
highly durable
Cons:
high silicon waste in the manufacturing process
relatively expensive (when compared with conventional silicon-based solar panels)

Poly-crystalline solar panels

Average efficiency range: 15% – 18%
Cell manufacturing process: Fragments of multiple silicon crystals are heated, melted, and pressed together to form a large solar cell
Appearance: Multi-faceted, non-uniform, gem-like surface; and are blue
Pros:
less silicon waste in the manufacturing process (than mono-crystalline)
most commonly used solar panels, globally

less expensive (than mono-crystalline)

Cons:
lower efficiency (than mono-crystalline)

Thin-film solar panels

Thin-film solar cells are classified based on the substrates they constitute.

Average efficiency range: 7% – 12%
Cell manufacturing process: A thin layer of photovoltaic material or combination of materials such as non-crystalline amorphous silicon (a-Si), Cadmium Telluride (CdTe), or copper indium gallium selenide (CIGS) is deposit onto a surface like glass, plastic, or metal.
Appearance: Uniform surface
Pros:
ideal for curved surfaces
flexible, portable, and lightweight
flexible pricing
easy to produce
Cons:
well-suited for small scale applications

short lifespan

Brands offering different types of solar panels

(Limited to solar companies that have a presence in India and/or Bangalore)

* does not include thin-film solar panel manufacturers

** rating based on the following metrics: efficiency, warranty, reputation, bankability, Solarify’s installation experience

What’s new with solar panels?

Solar panel manufacturers today offer a range of models with various features and efficiencies. Solar panel efficiency has increased substantially over the last few years due to many advances in PV technology. Such solar panels used in India, include:

PERC (Passivated Emitter Rear Cell)
HIT (Heterojunction with Intrinsic Thin-layer)
Split modules with half-cut cells
BIPV (Building-integrated Photovoltaics)
Bifacial solar panels
Duplex solar panels

PERC:

Principle: PERC stands for Passivated Emitter Rear Cell or Passivated Emitter Rear Contact. PERC technology adds a di-electric passivation layer to the back of the cell.
Benefits: PERC panels have a higher energy density per square foot and perform well under low-light conditions and high temperatures.
Applicability: Mono-crystalline, poly-crystalline solar cells

Heterojunction with Intrinsic Thin-layer (HIT):

Principle: The HJT solar cell combines the best attributes of mono-crystalline silicon cells (superior absorption) with that of amorphous-silicon cells (excellent passivation). The amorphous silicon layer reduces the electrons lost on the surface resulting in high efficiency.
Benefits: Heterojunction cells show a considerably lower temperature coefficient than conventional silicon solar cells.
Applicability: Mono-crystalline solar cells

Split Modules with half-cut cells:

Principle: Panels with REC TwinPeak technologies enables them to generate electricity even in partially shaded conditions (cloud cover, objects, and more).
Benefits: REC TwinPeak panels provide more power output when compared to standard poly-crystalline panels. The REC TwinPeak 2 Series delivers 20 Wp higher per solar panel.
Applicability: Mono-crystalline, poly-crystalline solar cells

Building-Integrated Photovoltaics (BIPV):

Principle: Building-integrated photovoltaics (BIPV) are solar panels that can replace building materials such as roofs, skylights, facades, and more.
Benefits: With BIPV, the initial cost gets offset by reducing the expenditure on building materials and labour.
Applicability: Mono-crystalline, poly-crystalline, and thin-film solar cells

Bifacial solar panels:

Principle: Captures sunlight from both the front and the back of the solar panel, thus producing more electricity than conventional solar panels.
Benefits: High efficiency achieved as both sides of the panels are functional.
Applicability: Mono-crystalline, poly-crystalline solar cells

Duplex solar panels:

Principle: Two-in-one or duplex solar panel generates electricity and heats water.
Benefits: Functions as both solar water heaters and power panels
Applicability: Mono-crystalline, poly-crystalline solar cells

Cost vs. Efficiency

A grid-connected utility and amount of shadow-free area available are essential components of any solar power project. Therefore, module efficiency a critical element for solar power system integrators and installers. For most applications, a mono- or poly-crystalline solar PV solution provides the right balance of price, efficiency, and reliability.

* cost taken over average of all types (incl. recent technological advancements)

** efficiency taken over average of all type (incl. recent technological advancements)

How to choose solar panels in 3 simple steps:

Determine solar panel efficiency and compare to an industry average of 16-18%
Check solar panel warranties against an industry average of 10 years
Check solar panel generation guaranties against an industry average of 25 years
Compare the cost to the relative efficiency of the solar panel

Not just panels, but choosing the right solar installer is critical to the success of any solar installation. Choosing a solar installer is a challenge in India because of the large number of options. Information related to the installer’s track record, revenue, client success, and team; can help in making a prudent decision.

[Also read: How are solar panels made? A simple explanation.]

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A practical guide to selecting solar panels

A short history