How Do Solar Panels Work?

iStock
iStock
They’re an increasingly common sight on the tops of buildings and residential properties: sometimes blindingly reflective panels that absorb sunlight and convert it into usable energy. Noted futurist Ray Kurzweil thinks we’ll all be using them by 2028. But how do solar panels work? Your basic understanding of solar panels—that they convert sunlight directly into electricity—is true. It’s called the photoelectric effect, and it was first discovered in the 1800s. Scientists learned that photovoltaic (PV) cells made of selenium were ideal for this purpose. While they later turned to the semi-conductor silicon, the idea remained the same: Up to a third of the energy found in the sun’s rays could, theoretically, be harnessed for electrical power under the most basic setup, and over 40 percent for the more expensive and complicated models. Silicon crystals by themselves aren’t necessarily great for this purpose, though. They need to be altered with boron and phosphorus and layered. The layer of boron-altered silicon has fewer electrons than it needs to form a bond, so an electron “hole” is created. The layer of phosphorus-altered silicon, meanwhile, has too many electrons. The space between is known as the P-N junction. As the sun’s photons enters the PV cells and starts dislodging electrons, the charge attempting to travel through the P-N junction gets diverted to an external circuit that can then carry the power to an inverter. You may not realize that the power generated with this method is a direct current, or DC, the same type found in batteries. To use the energy in a home or building, it needs to be converted to AC, or alternating current, the type found in outlets. And this is the role of the inverter. This kind of green energy has numerous benefits. Electricity doesn’t need to be transported by a utility company to the premises, and excess can be returned right back to the grid. If you’re thinking of installing a system, however, there are some caveats. For one, the upfront cost can be significant—around $10,000 to $13,475, depending on where you live, after tax credits. While you may be able to cut those costs with state rebate incentives or financing, it may take some time to recoup that investment. On the other hand, once installed, solar panels don’t appear to require much maintenance. Without moving parts, they’re not likely to suffer from mechanical issues, although you may need to replace the inverter at some point, which can get expensive. A site like EnergySage.com can also use your specific location to calculate how much a solar panel system might save you. So how do solar panels work? It’s one part the photoelectric effect and one part economy. If Kurzweil is correct, it won’t be long before we’ll all be well-versed in both benefits. Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

11 Masks That Will Keep You Safe and Stylish

Design Safe/Designer Face Covers/Its All Goods
Design Safe/Designer Face Covers/Its All Goods

Face masks are going to be the norm for the foreseeable future, and with that in mind, designers and manufacturers have answered the call by providing options that are tailored for different lifestyles and fashion tastes. Almost every mask below is on sale, so you can find one that fits your needs without overspending.

1. Multicolor 5-pack of Polyester Face Masks; $22 (56 percent off)

Home Essentials

This set of five polyester masks offers the protection you need in a range of colors, so you can coordinate with whatever outfit you're wearing.

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2. 3D Comfort Masks 5-Pack; $20 (25 percent off)

Brio

The breathable, stretchy fabric in these 3D masks makes them a comfortable option for daily use.

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3. Reusable Face Masks 2-pack; $15 (50 percent off)

Triple Grade

This cotton mask pack is washable and comfortable. Use the two as a matching set with your best friend or significant other, or keep the spare for laundry day.

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4. Active Masks 3-pack; $23 (14 percent off)

RipleyRader

Don’t let masks get in the way of staying active. These double-layer cotton masks are breathable but still protect against those airborne particles.

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5. Washable Protective Cotton Face Masks 2-pack; $13 (35 percent off)

Its All Good

Avoid the accidental nose-out look with this cotton mask that stays snug to your face.

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6. Washable 3D Masks 12-pack; $24 (44 percent off)

Elicto

With this 12-pack of protective masks, you can keep a few back-ups in your car and hand the rest out to friends and family who need them.

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7. Reusable Dust-Proof Mask with 5 Filters; $22 (45 percent off)

Triple Grade

This dust-proof mask can filter out 95 percent of germs and other particles, making it a great option for anyone working around smoke and debris all day, or even if you're just outside mowing the lawn.

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8. Reusable Fun Face Cover / Neck Gaiter (Flamingo); $20

Designer Face Covers

Channel some tropical energy with this flamingo fabric neck gaiter. The style of this covering resembles a bandana, which could save your ears and head from soreness from elastic loops. Other designs include a Bauhaus-inspired mask and this retro look.

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9. Seamless Bandana Mask; $8 (52 percent off)

Eargasm Earplugs

This seamless gaiter-style mask can be worn properly for protection and fashioned up into a headband once you're in the car or a safe space. Plus, having your hair out of your face will help you avoid touching your eyes, nose, and mouth before washing your hands.

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10. Two-Ply "Love" Face Masks 2-Pack; $18 (40 percent off)

Design Safe

These statement masks allow you to have a voice, even if your mouth is covered.

Buy it: The Mental Floss Shop

11. Neoprene/Fleece Neck and Face Mask (Purple); $10 (66 percent off)

Its All Good

This mask will definitely come in handy once winter rolls around. It features a fleece neck, face, and ear covering to keep your mask secure and your face warm.

Buy it: The Mental Floss Shop

Prices subject to change.

This article contains affiliate links to products selected by our editors. Mental Floss may receive a commission for purchases made through these links. If you haven't received your voucher or have a question about your order, contact the Mental Floss shop here.

Does Putting a Penny in the Microwave Really Make It Shrink?

J E Theriot, Flickr // CC BY 2.0
J E Theriot, Flickr // CC BY 2.0

It's a lesson even the worst home cooks (hopefully) know: Putting metal in the microwave is a recipe for disaster. Thanks to a viral image circulating on the web, some people may be tempted to ignore this piece of common sense in the name of experimentation. The picture shows one normal-sized penny next to three smaller pennies with the caption: "This is what happens when you put a penny in a microwave for 2 minutes." But according to Snopes, microwaving a penny won't cause it to shrink—if anything, it will just leave you with a broken microwave.

Microwave ovens heat food by bouncing microwaves around a metal box. Certain molecules, like the molecules in your leftovers, absorb these waves via dielectric loss and convert them into heat. Not all substances are compatible with microwaves, however. Metal contains high concentrations of electrons, and when microwaves hit a metallic surface, these electrons become very active and block the wave's path. Instead of absorbing into the metal, the microwaves bounce off, which can cause electrical sparks. Sometimes these sparks are strong enough to burn a hole in the oven's walls and damage the electronic equipment.

Even if you could somehow shrink coins in a microwave, the science explained above should be reason enough to resist the urge to try it at home. Anyone who tries the experiment against their better instincts will be disappointed. The photo that's been shared on social media is a hoax, with Snopes explaining that the smaller pennies likely originated in a magician's trick kit.

The post inspired some people to share false claims of their own. One response to the image showed a melted microwave that had allegedly fallen victim to the penny trick. In reality, the years-old picture came from a blogger who set their microwave on fire accidentally while heating a pot of oil. So while microwaving a penny may cause some sparks and potentially damage your appliance, a dramatic explosion isn't likely. (Please just take our word on that, too.)

[h/t Snopes]