UNDERSTANDING SOLAR ENERGY
The Electromagnetic Spectrum
What is The Electromagnetic Spectrum?
Scientists describe all forms of light as electromagnetic radiation. In fact, all light waves are electric fields and magnetic fields coupled together. Therefore, the electromagnetic spectrum is the range of wavelengths of all forms of light, visible and invisible.
Including visible light, there are a total of seven forms of light on the electromagnetic spectrum. From left to right, the invisible forms of light include radio waves, microwaves, infrared, ultraviolet, x-rays, and gamma waves. Some of these invisible forms of light may be familiar, as we use them on a daily basis.
The Sun emits all forms of electromagnetic energy, but only infrared light, visible light, and ultraviolet light reach Earth’s surface.
Solar Energy
The sun has a surface temperature that is estimated to be about 10,000 degrees Fahrenheit and a core temperature that exceeds 27 million degrees. This thoroughly violent state is fed by nuclear reactions, and it is estimated that you’d need to explode 100 million tons of dynamite every second to equal the energy produced by the sun.
The sun emits a vast amount of energy through the visible and invisible energy spectrum. In fact, NASA calculates that an impressive 1.365 kilowatts of energy per square meter reach our upper atmosphere. The majority of the solar energy reaching the Earth is visible light, with particular emphasis on the blue spectrum with wavelengths just under 500 nanometers. The energy from the sun at lower wavelengths than violet light is called ultraviolet (UV) light. UV light is in the 10 to the 400-nanometer range. On the other side of visible light is infrared energy (IR). IR energy falls in the 700 nanometers to 1 µm region. IR energy is responsible for the transmission of heat to the Earth’s surface. In total, UV light makes up 5%, visible light makes up 43% and infrared light makes up 52% of the sun's total heat that reaches the Earth's surface.
Not All Window Film Is Created Equally
Window Film, Visible Light and UV Specifications
When manufacturers design window film, they incorporate different materials designed to block specific energy wavelengths. Most films do a great job blocking UV energy. As a generalization, dyed films resist about 96 percent of UV energy, and premium ceramic films block 99 percent.
Films that have a low Visible Light Transmission block energy in the visible light region between 400 nanometers and 700 nanometers. Specifically, a 5 percent VLT film blocks all but 5 percent of the visible light to make your vehicle darker inside. A film with a 70 percent VLT rating allows 70 percent of visible light to pass into the vehicle making the inside light and bright.
How Window Tint & Heat Rejection Works
Window films designed to block heat transfer comes in three designs: dye, metallic, carbon /ceramic, or variations of those. Most window tint manufacturers offer one or two specifications that describe a film’s ability to block Infrared energy. Some companies focus on the Total Solar Energy Rejected (TSER). This value describes the total amount of solar energy blocked across the entire spectrum and includes ultraviolet, visible light, and infrared energy. On its own, it’s not a good way to determine how much heat will be blocked since a dark film will have a much higher TSER than a film that is almost clear.
IR specifications would seem to be the best way to quantify how much heat a film will block. A higher value means less heat will transfer into the vehicle. Premium films can supposedly block between 50 and 75 percent of solar energy. High-end ceramic films claim to block as much as 97 percent of IR energy, but often there’s an asterisk or note associated with the specification.
The Fine Print of IR Rejection Specifications
Any time you compare numbers, you need to be 100 percent sure the measurements are the same. When it comes to IR rejection, different manufacturers target different IR energy frequency bands when rating their films.
One company rates IR rejection from 900 to 1,000 nanometers. Another uses two specifications – one called Infrared Energy Rejection (IRER) and another called Selective Infrared Rejection (SIRR). IRER covers the 780-2,500 nanometer range and includes “absorbed and re-radiated energy.” The SIRR covers the same range but quantifies that the measure is “not directly radiated through the glass.” Looking at a third manufacturer, they don’t offer any clarification as to what wavelengths are blocked by their Infrared Reject (IRR) specification. A fourth company changes its ratings depending on the grade of film you choose. Their carbon film is rated between 900 and 1,000 nanometers and their nano-ceramic film is rated from 780 to 2,500 nanometers.
As you can see, the numbers simply aren’t comparable because the measurement criteria and test methods change by the manufacturer. How frustrating is that? This is why it's extremely important you purchase the film from a reputable window film manufacturer like LLumar Window Films.
How to Choose a High-Quality Heat-Rejecting Window Film
If you’re shopping for a quality heat-rejecting window film, your best bet is to seek out a retailer like All Florida Tinting Co. with an interactive display in their showroom. Our displays use a heat lamp to create lots of IR energy, then you can select films to put in front of the lamp to demonstrate how much heat is blocked. Seeing is believing! We also have BTU meters and heat measuring devices that show in real time how well the film you are interested in is performing. Visit our showroom @ 801 Maplewood Dr. Suite 13 in Jupiter, Florida today for a full one-on-one consultation.