In an ideal solar cell efficiency in p-n junction PV cells is “only” 33.7%. Though, some of the highest efficiencies for residential use are reaching into the 24% zone.
What does it mean? It means we’re going to have to find a better way in the next decade or so. Fortunately, we’re already on the way to new materials and new technologies at higher efficiencies that can be used anywhere.
But what is solar cell efficiency and what do the ratings even mean? Keep reading to find out!
What Solar Cell Efficiency Means for Your Solar Power System
When you find a solar company and start the design phase, many people quickly breeze through the different types of solar panels and construction methods picking only ones with the highest efficiency ratings.
Is that the best way? Well, it depends.
Solar cell efficiency is determined in STC (standard testing conditions) temperatures of 25°C or 77°F.
From these temperatures, they determine the efficiency in terms of the percentage of a given amount of energy harvested per area. Even the mass of the air is nominalized for the test. This is because air density plays a role in scattering photons from a source before hitting panels.
Balancing the Equation
The equation looks something like: Pmax / (Area * 1000W/m2) * 100 = Efficiency
If that’s confusing to you, you’re not alone.
“Pmax” is the panel’s maximum power expressed in Watts.
The 1000W/m2 is the sun’s output of electricity within an Air Mass rating of 1.5 (AM 1.5). In other words, for every area 3.3 feet square, the sun radiates 1 kiloWatt of energy or 1000 Watts.
As you go up or down in temperature, there is a heat coefficient. Every type of construction has its own coefficient value that lowers efficiency from these STC values.
For example, IBC cells (interdigitated back contact) are the most efficient, heterojunction (HJT) cells are right behind them, but have almost half the heat coefficient as IBC cells do.
If you’re in Phoenix or Florida, you know that most of the year you’ll never see 77°F or STC temperature.
Why Only 33.7% Solar Cell Efficiency?
Part of the reason why other materials like perovskite have a chance at higher efficiency is something called “bandgap.” Silicon’s bandgap is perfect for light waves in a certain range right above infrared and ending after yellow.
To capture light from the green and blue range, where more energy is bound up, it has to go through a special film. This film will step the solar light energy down into the high-infrared light spectrum. It’s again right on the edge of what the cell can absorb it isn’t an ideal level of efficiency.
Much — but not all — energy is lost this way. There are plans in the works to try something like this with UV light in the future, too.
Using plans to capture energy like this could theoretically boost efficiency up to or surpassing 35%.
Solar Cell Efficiency in a Jiffy
Solar cell efficiency is a big and complex topic, with a lot of factors involved. Even the color of the backing material used on a solar cell can affect efficiency. Heat buildup will eat into a solar power panel’s heat coefficient and degrade it faster than STC predicts.
This only means that manufacturers have a long way left to go before maxing out on solar power.
Did you learn what you needed to know about solar cell efficiency? Keep browsing our articles to find more solar power facts and how to take advantage!
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