There is no such thing as a standard solar panel size anymore. Therefore, is “NOCT power density” (W/m2) the efficiency comparison gauge to cut through the sales spin? Short answer, yes. And we’ve made it super easy for you to calculate, You simply need 5 variables that should be readily available on every manufacturer’s datasheet, which possibly it’s better to identify later with the formula. Once calculated, compare your solar panels NOCT Power Density against the average industry values.
What must be noted is that Power Density at STC provides some insight, but is often directly proportional to Efficiency at STC in most panels with no consideration for temperature derating. Example 19.9% efficiency = 199 W/m2, or a 21 % efficiency module will present a power density at 210 W/m2. However, in the interest of greater knowledge. What happens to the efficiency or power density when temperature derating figures are applied? Welcome to NOCT Power Density, the true measure of power and performance on your installation.
NOCT Power Density Ingredients.
In this instance, we’re combining two calculations in order to provide 3 answers which aren’t often available on a solar module manufacturer’s datasheet. Here’s what you’ll need which should be available on most reputable manufacturers data sheets;
- Module Watts (Standard Test Conditions – STC).
- Nominal Operating Cell Temperature – NOCT (also referred to as Nominal Module Operating Temperature – NMOT).
- Temperature Coefficient of Pmax.
- Module Length.
- Module Width.
Image: NOCT Power Density ingredients for calculator identified on a manufacturer datasheet.
NOCT Power Density Calculator.
Enter your values into this calculator. Note: Enter values as on the datasheet. NOCT; exclude the ± variables, eg 45±2oC listed, enter 45. Temperature Coefficient Pmax; enter the negative symbol, eg -0.30%/oC listed, enter -0.30.
PMax under NOCT and Efficiency NOCT are supplementary results certain researchers may find helpful if not listed on the manufacturers datasheet.
NOCT Power Density Guide 2022/23.
What do the resulting numbers mean? Not much without a gauge. The below chart identifies the industry best known NOCT Power Density values for commercially available solar panels as measured across a diverse module landscape in 2022.
Save this post and calculate solar module power density anytime. For more information on Solar Analytica Classifications visit; https://solaranalytica.com/module-assessment-criteria/.
Why NOCT Power Density?
Gone are the days of typical 6 inch, 60 or 72-cell module variants. When shopping for a particular solar panel, comparing the (STC) output Wattage no longer provides the technical advantage one would assume. Doing so could result in paying a premium for inferior technology. This is an industry-wide result of many manufacturers racing to produce higher output solar modules. Without a significant technical improvement, many solar modules occupy a larger surface area to improve power output. Even more apparent with Nominal Operating Cell Temperatures (NOCT) and temperature derating factors applied.
How to Calculate The NOCT Power Density of a Solar Panel?
NOCT Power density is the answer to confusion when gauging efficiencies of solar panels (cell efficiency, module efficiency, max efficiency, efficiency NOCT) and the relationship with a nominated area. A simple solar module power density calculation normalises all solar panels power output to a square meter, W/m2 at the Nominal Operating Cell Temperature. As would be the case if every solar panel ever produced was 1m x 1m in dimensions and measured in derating conditions similar to your roof or project (not laboratory conditions).
The calculation can either be 1 or 2 steps depending on the manufacturer;
Sometimes Pmax NOCT isnt available on many datasheets. This may need to be determined first.
1. Pmax NOCT = Module power STC x (100% + (NOCT – 25) x Temperature Coefficient Pmax) x 0.8
Irradiance on cell surface = 800 W/m2. Air Temperature = 20oC. Wind velocity = 1 m/s. Air mass 1.5.
Once you have the Pmax NOCT the power density in conditions more likely to be simulated in the real world can be calculated;
2. W/m2 NOCT = Pmax NOCT / (Panel Length m x Panel Width m)
Many leading solar module manufacturers have begun displaying solar module power density on their datasheets in order to provide the greater insight in technology differential. To assist transparency Solar Analytica encourages the display of NOCT power density to assist consumers in making a transparent buying decision.