Note that, unless otherwise stated, this article focuses on solar panels using crystalline silicon (c-Si) cells – by far the most common cell type used in solar panel manufacturing.
It’s no surprise that as solar PV has become mainstream over the past 30 years, technological improvements have led to dramatic gains in the power a single solar panel can produce. What is surprising is that during this period, the dimensions of solar panels have not increased so much despite gains of more than 7 times the power output of a single PV panel. This testifies to the following facts:
- Since solar panels are really just arrays of photovoltaic cells, the output power of a solar panel is mainly determined by:
- How many photovoltaic cells does the panel contain, and
- The efficiency of these cells
- The dimensions of a solar panel (physical size) are mainly determined by:
- How many photovoltaic cells does the panel contain, and
- The size of the silicon wafers used in these cells
Small, medium, large and extra large solar panels
Before getting too specific, let’s be generic. There are no formal definitions or hard and fast rules regarding solar panel size and what makes a particular module “small”, “medium”, “large” or “extra large”. But from a freight shipping perspective, anything over 8 linear feet usually incurs an oversize surcharge, so we’ll use that as a threshold for “extra large” solar panels. Note that because we are talking about shipping here, an item slightly smaller than 8′ will incur an oversize charge if the pallet it is shipped on (including the packing material used to protect it) is longer than 8′ (it is precisely the box with the Q CELLS DUO XL-G10 475/480W modules, available soon altE Store).
Broadly speaking, this means that we can think of first-generation solar panels (which typically have 36 cells) as “small”, the 60 and 72-cell modules that have dominated the industry for the past decade as “medium” and “large”, and modules with more than 72 cells as “extra large”.
Click on the image to enlarge.
Of course, there are exceptions to many rules, and we have a few here. Please note that :
- Many solar panels today use half-cut cells to reduce resistive power loss and are often marketed as having 120 or 144 cells, but are actually still 60 or 72 cell modules and would therefore fall into our categories of medium or large size. Although…
- Some 72-cell panels using M6 or larger wafers are XL solar panels by our length-based definition (see below for more information on wafers).
- Interestingly, some 96 cell panels aren’t long enough to incur oversized shipping charges because their cell arrangements are 12×8 not 16×6, which means they aren’t longer than 72 cell panels, just wider.
In summary, solar panels over 8′ in length (or panels shipped on pallets over 8′ in length) are considered extra large solar panels.
What to know about super-large solar panels
Extra large solar panels have implications for installers and DIYers planning photovoltaic systems. Although not too common yet, XL-sized solar panels are here to stay. What does this mean for you?
- It is not possible for someone to install them – or even move them – without the help of at least one other person. Plan your installation accordingly!
- It is not possible to lay them flat in a 7′ truck bed and be able to close the tailgate.
- They are long enough to incur oversize charges from most shipping companies, which means shipping is more expensive, especially when ordering in small quantities.
- They are also long enough that fork extensions are needed to move pallets of them with a forklift.
- Their extra weight and length over medium and large panels may require different products and shelving configurations than you are used to.
- Although the width and especially the length are increasing, there is no indication that the thickness of the frames of the modules will increase (and no reason to expect it), which means the same widely available and proven. solar panel clamps that have been on the market for years will continue to be compatible with extra large solar panels.
How did solar panels get so big?
The efficiency of photovoltaic cells has improved slowly and steadily over the past few decades. In the mid-1990s, efficiencies approaching 15% were at the forefront of solar cell technology. Today, efficiencies of 29% have been achieved under laboratory conditions, while numbers in the 20% range are becoming the norm for modern commercially available modules. We will likely see more efficiency improvements in the coming years before the theoretical efficiency limit of single-junction c-Si-based cells of around 30% (known as the Shockley- Queisser) does not become a real obstacle.
The raw silicon is melted and shaped into long ingots, which are then sliced into paper-thin slices that form the backbone of photovoltaic solar cells.
Photovoltaic cell efficiency improvements come in many forms, but the one related to the physical size of the cell is the silicon wafer around which the cell is built. In the 1980s and early 1990s, slices measuring 100mm square were the standard size. In the mid-1990s, 125 x 125 mm wafers became the new standard, and these were eventually replaced by 156 x 156 mm wafers (known as the “M0” wafer) and thus launched a new silicon wafer naming convention that currently extends to 217×217 mm plates called “M12+”).
Along with the increase in efficiency (and size) of solar cells, the number of cells per module has also increased over time. 36-cell modules were the first standard size and are still commonly used as 12V “off-grid” panels. 60-cell modules eventually became standard and are still manufactured today, with 72-cell modules eventually becoming a additional standard – and the benchmark for commercial and large-scale solar projects.
Today, with ever-increasing consumer demand for electricity and incremental improvements in solar power generation, we are seeing more and more powerful panels hitting the market. Generally speaking, this is a good thing for consumers because it can help reduce system costs on things like rack, mounting, and balancing system components – as long as increased shipping and labor costs are carefully considered when purchasing extra large solar panels.