How Do Solar Garden Lights Work?

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Do you like fairy lights? Do you think 'solar fairy lights' sounds futuristic, environment-friendly and above all, cool? Do you know how solar fairy lights work? Does secondary school physics feel like a really long time ago? Read on, fairy light fan, as we attempt to answer the most common questions we get asked about the ins and outs of solar garden lights. We'll start with the basic ingredients: we've got the sun, the solar panel, and the fairy lights. The sun gives out energy in the form of light, the solar panel gladly accepts this energy, and the fairy lights come on.

But why does my solar panel have batteries in it?

Don't panic, we haven't sent you the wrong thing - they're supposed to be there. They're special rechargeable solar batteries. A lot of people think (and you'd be forgiven for thinking this, because this is complicated stuff) that the solar panel laps up the sunlight and passes the solar energy directly along to the LED bulbs in your fairy lights, but you're forgetting the essential middleman: the battery. In actual fact, the solar panel never speaks directly to the lights. The panel is just there to charge your solar battery (or batteries), which it does by absorbing solar energy from the sun during daylight hours and passing that power as electrical energy along to the battery, where it gets converted and stored as chemical energy and then changed back to an electrical output when you want to turn your lights on and then you're talking about light energy from electrical energy and so on and so forth, go to the top of the class you physics genius you.(If you actually are a physicist, we know this is a little over-simplified but we're trying our best. Please don't write in.)

Ok, but what actually is a solar panel?

Yes, good question! Ladies and gents we present to you a solar panel!

The panel itself is a flat surface made up of silicon chips that are called PV (or photovoltaic) cells. These cells are stacked in layers on the panel, backed by a piece of metal. When sunlight passes through these layers, all sorts of things happen very quickly within the structure of the silicon with the end result being a charge in that piece of metal at the bottom of the panel. The wires that you can see in the photos above connect the metal base to the battery, and that's where all the power is stored.

Right. So how do the lights know when to come on?

It's called a photoresistor, and it's not someone who avoids having their picture taken. It's a little device that controls the circuit inside your solar lights depending on how light or dark it is in the area where you've put your lights. Basically, during daylight hours the solar panel happily charges the battery but the photoresistor stops the lights from coming on. When it's nighttime and the photoresistor detects little or no light, it activates the battery and the fairy lights come on. It does all this automatically like some kind of tiny circuit overlord. It's only a little thing but that photoresistor is pretty much running the show in there.

And is the solar panel on my fairy lights weatherproof?

As solar panels are really only ever used outside, they are indeed all weatherproof. We'd just recommend giving yours the odd wipe down with a clean cloth to remove any dirt or debris that might have settled on the panel's surface, as this could make it slightly less effective at charging the solar battery inside.

So do my solar lights need constant sunlight to charge?

Yes and no. We're not saying you have to relocate to the Bahamas if you want solar lights in your garden (although if you decide that's the right move for you, invite us please). We know that the British weather is unreliable at best, and 15 years ago solar lights in Yorkshire wouldn't have been much use to anyone but technology has come on leaps and bounds in the past decade or so meaning that yes, solar lights are the right choice for you even in a nation as drizzly as ours. However, the solar panel does still need some sun. And we're talking direct sunlight, not sunlight that has to fight its way through a canopy of evergreens and a canvas awning before it reaches your lights. Some solar panels even charge through a layer of snow, but they're not going to charge in your shed, for example, unless you've got the panel on the roof and the lights trailing inside through an open window (we're not joking, that would actually work).To learn more about the reliability of solar lights from season to season and to find out if your solar lights will work in winter, read our blog post