What Are the Different Types of Solar Panels?

There are 3 foundational categories for standard residential, commercial, utility installations. Here is a quick overview:

While these three are the foundational physical build of the panel, they are subdivided in N-type, P-type, TOPCon, and HJT. They are specific cell technologies and architectures that are only available on monocrystalline silicon solar cells.

1. Monocrystalline Solar Panels

Whenever you dive into the market for the most efficient and cost-effective PV solar cells, you will almost always see yourself in front of monocrystalline solar panels.

What They Are

Monocrystalline solar panels are single continuous crystals of silicon. During the manufacturing process, a single silicon seed crystal is drawn out of a vat of molten silicon to create a pure cylindrical ingot. This ingot is sliced into thin wafers to make individual monocrystalline solar panels. As they are created from a single continuous crystal, the electron generated electricity has more room and makes them highly efficient in generating stronger direct current DC.

Advantages

Monocrystalline solar panels are known for their superior space efficiency. Due to this, they yield the highest power output per square foot. They fare better in higher heat conditions and have a longer lifespan.

Limitations

Due to its advanced manufacturing process and cutting of a single silicon crystal, these panels tend to cost more, but ultimately are more cost-effective for larger solar EPC projects.

Where They're Commonly Used

Monocrystalline solar panels are industry favorites and thus are utilized in all types of projects ranging from residential to full-fledged solar EPC commercial projects.

2. Polycrystalline Solar Panels

Polycrystalline panels, aka multicrystalline panels, are the dominant force in the global market due to their lower production costs.

What They Are

Polycrystalline solar panel cells, as the name suggests, are made by melting multiple fragments of raw silicon. Then molten silicon is poured into a large square mold and cooled and then later sliced in perfect square wafers. Due to using multiple silicon fragments, the final product gives a shattered-glass appearance and has a distinct blue hue.

Advantages

The main advantage of Polycrystalline solar panel cells is their price. A simple manufacturing process means more availability and requires less energy while having zero silicon waste. These panels are advantages for very small projects with lower energy needs which only require a few PV panels.

Limitations

Polycrystalline PV solar cells are manufactured with multi-silicon and thus have microscopic barriers which reduce its efficiency. When light electrons hit the panel, due to these crystal grain boundaries, some energy is lost due to internal resistance. These panels also perform less effectively on hot days and some prefer the look of sleek black panels over blue panels.

Typical Applications

Polycrystalline panels are suited for old-type facilities, projects based on cost, commercial flat roof constructions, and ground utility projects where space is not an issue and the efficiency of the panels is not a priority, but the overall costs per watt are.

3. Thin Film Solar Panels

Thin film solar panels are entirely different in manufacturing to harness the power of the sun.

What Thin Film Solar Cell Means

A thin film solar cell is made by depositing one or more extremely thin layers of photovoltaic material onto other supporting substrates like glass, plastic, or metal. These panels are hundreds of times thinner than traditional silicon wafers and are better at absorbing light at microscopic levels. This makes the final product extremely lightweight and flexible.

Main Thin-Film Technologies

Thin filmed material encompasses several distinct chemical makeups:

• Amorphous Silicon (a-Si): This is a type of non-crystalline silicon which is used in a thin layer state and is usually found in devices such as calculators.
• Cadmium Telluride (CdTe): This is the most widely practiced technology in thin-film technology, famous for its very low cost of production and high energy yield in practice.
• Copper Indium Gallium Selenide (CIGS): This is the most advanced form of thin film whose efficiency potential is the highest compared to other technologies. However, it is extremely difficult to manufacture at a larger scale.

Advantages

Thin film solar cells are physically versatile, lightweight and don't require a heavy racking structure. These thin film solar panels are also incredibly resilient to high temperatures and perform amazingly well in low-light conditions. And with automated manufacturing processes, they are highly scalable.

Limitations

The biggest limitation of thin film solar cells is the requirement of massive space to match the electrical output of crystalline silicon arrays. Furthermore, their lifespan is also shorter than average crystalline silicon panels under harsher conditions.

Where They're Useful

Thin film solar cells are dominant in specialized applications such as large-scale commercial roofs with weight limitations, large utility-scale desert installations using CdTe, integrated in solar shingles and solar windows for large buildings and for portable solar RV or marine use.

N-Type, P-Type, TOPCon and HJT Solar Panels

With each advancement in solar PV technology, industry as moved pass mono vs poly into more denser architecture and here you will encounter terms like N-types, P-types, TOPCon, and HJT solar PV cells

P-Type vs N-Type

In order to make the silicon wafer conductive, it has to be "doped" with particular chemicals. The industry standard for years has been the P-type (positive-type) cell, which means that the silicon is doped with boron. Cells doped with boron, however, have a problem known as Light-Induced Degradation (LID), where the panel loses a fraction of its efficiency immediately upon being exposed to sunlight.

N type solar panels use silicon doped with phosphorus as a negative electrode. N-type cells are largely resistant to boron-oxygen defects which reduces their degradation rate significantly, allowing for longer lifetime and initial efficiency values compared to conventional alternatives. The modern photovoltaics industry has moved to N-type cells as a replacement for older P-type designs due to their superior performance characteristics.

TOPCon

Tunnel oxide passivated contact (TOPCon) technology is one of the most promising concepts in the photovoltaic industry. TOPCon cells are produced using an n-type substrate and a thin layer of silicon dioxide and doped poly-silicon on their backside. These layers benefit the performance of solar panels by reducing the electron-hole recombination in the silicon wafer. As a result, the output voltage and current rise substantially, thus increasing the energy efficiency. The technology is very attractive to the producers since it allows upgrading the existing equipment and, therefore, lowering the production costs of high-efficiency cells.

HJT

Heterojunction Technology (HJT) is one more advanced type of cell. The HJT cell uses a standard crystal silicon wafer with two very thin layers of amorphous (thin film) silicon attached to each side. The resulting structure takes full advantage of the high-power capacity of crystalline cells while also capitalizing on the superior low-light and high-heat characteristics of thin film. Panels made from these cells have an incredibly low temperature coefficient, meaning that their efficiency is reduced by only a fraction during hot summer days.

What gives? Why are these found in modern modules? The conventional P-type cell has topped out in terms of performance. In order to get the needed wattage per square meter to advance past this barrier, manufacturers are forced to use new cell designs like N-type, TOPcon, and HJT to wring out every possible electron from incoming photons.

Monocrystalline vs Polycrystalline vs Thin-Film

Here is Monocrystalline vs Polycrystalline vs Thin-Film:

What This Means for Customers:

If you have a smallish roof and want to cover you bill 100%, you need the heavy lifting of high efficiency mono panels. If you own some land, and have lots of room, and want the cheapest possible ground mount installation, poly will still work (though it's seeing less and less use in the modern marketplace). If you need to power a cabin off-grid but have a metal roof that can't support standard roof mounts, you might need to go with some peel-and-stick thin film.

Which Is the Best Type of Solar Panel?

When asked for the one best type of solar panel, a certain knee-jerk reaction might suggest something about high-efficiency monocrystalline being the clear winner. However, this is a vast oversimplification. The best technology depends on the constraints of the project.

For Homes

When thinking about residential solar, efficiency is the name of the game. Your roof can only support so many watts in a limited footprint. To fulfill a modern household's energy needs, you need to utilize every square inch of installable roof space (preferably a south-facing tilt with no shade nearby), which makes high efficiency crystalline silicon (N-type or TOPcon, if you want to get specific) the clear winner.

For Commercial Projects

For commercial buildings, the variables change. Efficiency is still good, but you now have much more space to play with (a commercial rooftop is typically a large flat concrete slab), and you now need to consider the balance of project economics and long-term project survivability. You'd likely install less powerful but more durable modules for a commercial building. A slightly less efficient, but longer-lasting and cheaper module could actually have a higher ROI than a premium all-around product.

For Utility-Scale Projects

For a utility-scale project, it's all about the LCOE (Levelized Cost of Energy) calculations on a massive spreadsheet. Factors such as total yield, bifacial yield (if the ground adjacent to the panels is a reflective surface), power degradation over 30 years, and high-temperature performance all factor into choosing the best possible solar panel. A utility farm in the middle of a desert might favor a highly bifacial HJT solar panel to maximize output during the day, and it will have a lower LCOE than the high-efficiency panel would in that locale.

What Is the Highest-Efficiency Solar Cell?

The race to develop the highest efficiency solar cell is one of the most fiercely contested areas of the renewable energy industry. It is crucial to distinguish between cell efficiency and module efficiency. The former determines how much electricity is produced by a single, ideally optimised, laboratory-tested square of silicon. The latter describes the power output of an installed solar panel comprising dozens of cells connected together by wires encased in glass. Module efficiency is always lower than cell efficiency due to the power loss along the circuits and the inevitable power loss due to reflection at the front glass layer.

In recent years, laboratory-cell efficiency records have scored remarkably high: over 34.85% for tandem perovskite-silicon cells, over 27.81% for purely silicon cells (LONGi’s HIBC technology), and others. However, in practice, the module’s efficiency is lower by several percent due to the abovementioned losses during the production of the solar panel.

It is also essential to understand that the most efficient solar cells in laboratory conditions are not always the best choice for a particular project. One must balance the efficiency and cost: novel record-breaking cells are often too expensive or uncommon to be economically viable.

Solar PV Panel vs Solar Flat Plate Collector

As you research Renewable Energy you may stumble onto a term called solar flat plate collector. You may also be confused as to how it relates to an array of solar panels. Let me clear that up for you.

A standard PV panel is a photovoltaic panel. Which means that it absorbs photons (sunlight) and stores them as electrical energy to power your lights and appliances.

A solar flat plate collector is a main ingredient in a solar thermal system. They are used to collect the sun's energy to heat water for your home or even heat your living quarters. They are large boxes that have been insulated on all sides except the top. On the top there is a black plate that absorbs the sunlight and a set of pipes that run along the top. As the sun beats down on the collector it heats a fluid (usually water or antifreeze) that runs through the pipes. The heated fluid is then pumped into your home to supply your hot water needs or heat your home. They are not in competition with one another. These are two completely different systems that happen to harness the same resource. One system produces electricity while the other captures the sun's heat to warm water or your home.

How Does a Photovoltaic Cell Work?

To fully understand solar systems, it's a good idea to understand the mechanics behind a photovoltaic cell working. Although there is a technical process that takes place on the inside, the photovoltaic cell working can be simply explained in a few easy steps.

The solar photovoltaic cell at the heart of this technology is made of layers of silicone that have been treated with chemicals to create a positive and negative pole, and therefore an electric field.

Now let's describe the process in a solar photovoltaic cell working:

• Sunlight reaches the surface of the PV cells: Particles of sunlight, called photons, collide with the surface of the PV cells
• Creating electrons: The energy from these photons is transferred to the cells' silicone, forcing electrons from the atoms on the surface to move away from their nucleus
• Directed movement of electrons: The electric field of the cell directs the movement of these free electrons to metal plates on the sides of the cell
• Generating DC electricity: This directed movement of electrons creates Direct Current (DC) electricity
• Converting DC to AC electricity: Inverters are used to convert DC to Alternating Current (AC) electricity because the electricity used in homes and businesses is in this form