Using the sun's energy to power electrical devices seems like a pretty good idea to us. In fact, it seems like an ideal solution! But just how effective and reliable are solar devices? We'll be putting all kinds of solar-powered products to the test to find out whether or not they're worth the investment.
In this section of the site, you'll find reviews of all kinds of devices that use solar panels to turn the sun's energy into electrical power. For the moment, most of the products we're testing tend to be portable solar panels designed for occasional charging or emergency power. However, we could well start testing larger solar panels or other types of solar device in the future.
No plug? Use the sun!
You may be wondering why we've decided to start testing solar chargers, especially when, these days, none of us are ever really that far from a plug socket. But what if you're lost on a mountain hike or off-piste in the Alps? What if, by some miracle of fate, you have network coverage but no battery left on your mobile? It's at times like these that a solar panel can prove incredibly useful, as with a portable solar charging system, you can power up your phone wherever you happen to be—no plug required!
Sounds great doesn't it? But what we really need to know is how long solar charging systems take to power-up the average mobile device. It'll also be interesting to see just how big a solar panel needs to be to get a decent power output.
How does it work?
Solar panels contain photovoltaic cells which convert the sun's rays into electrical energy via a principle known as the photoelectric effect. This in turn produces direct current, which is ready to consume. In other words, you can hook up an electrical device directly to the solar panel to either charge it or run it. This current generated can also be stored in a battery, which can then be used to charge or run a device either straight away, as an intermediary power source, or at a later date. However, the amount of power required by the device you're charging must be compatible with the output from the solar panel.
Note that while batteries and solar cells produce direct current (DC), the electricity we get from the National Grid is alternating current (AC). Unless you're using the solar panels to charge a battery or run a batter-operated device, you'll need to hook up a power inverter to change the DC into AC for products that are mains-only.
Making sense of Watts, Amps and Volts
The key equation some of you may remember from school is: Power (P, measured in Watts) = Voltage (V, measured in Volts) x Current (I, measured in Amps), or P = V x I. Current measures the number of electrons moving though a given circuit whereas voltage effectively measures the 'pressure' pushing those electrons along, otherwise known as electromotive force. Imagine it's like water in a pipe: the Amps are like the water flow rate (in a given section of pipe), the Volts are like the water pressure (you'll feel it if you try and block the pipe) and the power (Watts) is the product of these two factors. Logically, if you increase water pressure, then more water will come out of the pipe. Similarly, increasing voltage will increase the flow of current.
Debunking the myths
Solar panels work just as well indoors through glass as outdoors. False! We did a few tests with the powermonkey (see below), and through a window, the solar panels generated 3 to 20 times less power!
Solar panels work best when it's hot. False! Solar panels like the sun, not the heat. A solar panel will work better on a chilly but bright mountainside than in the middle of the Sahara with 50°C heat but overcast skies.
If a solar panel is advertised with an output of 240 Wp, I can use it to power a device that runs on 240 Watts. Not exactly. Take a look at the insert (above, right) to find out exactly how that little 'p' changes things. The output provided needs to fit the device's needs.
You should look for a solar panel with a surface that's all the same colour. It depends. Monocrystalline panels are usually one single, solid colour, and offer the best output performances. However, they're also the most expensive type of solar panel. In descending order of both output and price, it goes monocrystalline, then polycrystalline and then amorphous, which is the kind of basic solar cell found in solar-powered calculators, for example. Polycrystalline panels therefore make a good compromise. So how can you spot one? If you look closely at the surface of a polycrystalline solar panel you'll see different coloured patches, like in the picture below:
No plug? Use the sun!
You may be wondering why we've decided to start testing solar chargers, especially when, these days, none of us are ever really that far from a plug socket. But what if you're lost on a mountain hike or off-piste in the Alps? What if, by some miracle of fate, you have network coverage but no battery left on your mobile? It's at times like these that a solar panel can prove incredibly useful, as with a portable solar charging system, you can power up your phone wherever you happen to be—no plug required!
Sounds great doesn't it? But what we really need to know is how long solar charging systems take to power-up the average mobile device. It'll also be interesting to see just how big a solar panel needs to be to get a decent power output.
How does it work?
Solar panels contain photovoltaic cells which convert the sun's rays into electrical energy via a principle known as the photoelectric effect. This in turn produces direct current, which is ready to consume. In other words, you can hook up an electrical device directly to the solar panel to either charge it or run it. This current generated can also be stored in a battery, which can then be used to charge or run a device either straight away, as an intermediary power source, or at a later date. However, the amount of power required by the device you're charging must be compatible with the output from the solar panel.
Note that while batteries and solar cells produce direct current (DC), the electricity we get from the National Grid is alternating current (AC). Unless you're using the solar panels to charge a battery or run a batter-operated device, you'll need to hook up a power inverter to change the DC into AC for products that are mains-only.
Making sense of Watts, Amps and Volts
The key equation some of you may remember from school is: Power (P, measured in Watts) = Voltage (V, measured in Volts) x Current (I, measured in Amps), or P = V x I. Current measures the number of electrons moving though a given circuit whereas voltage effectively measures the 'pressure' pushing those electrons along, otherwise known as electromotive force. Imagine it's like water in a pipe: the Amps are like the water flow rate (in a given section of pipe), the Volts are like the water pressure (you'll feel it if you try and block the pipe) and the power (Watts) is the product of these two factors. Logically, if you increase water pressure, then more water will come out of the pipe. Similarly, increasing voltage will increase the flow of current.
Debunking the myths
Solar panels work just as well indoors through glass as outdoors. False! We did a few tests with the powermonkey (see below), and through a window, the solar panels generated 3 to 20 times less power!
Solar panels work best when it's hot. False! Solar panels like the sun, not the heat. A solar panel will work better on a chilly but bright mountainside than in the middle of the Sahara with 50°C heat but overcast skies.
If a solar panel is advertised with an output of 240 Wp, I can use it to power a device that runs on 240 Watts. Not exactly. Take a look at the insert (above, right) to find out exactly how that little 'p' changes things. The output provided needs to fit the device's needs.
You should look for a solar panel with a surface that's all the same colour. It depends. Monocrystalline panels are usually one single, solid colour, and offer the best output performances. However, they're also the most expensive type of solar panel. In descending order of both output and price, it goes monocrystalline, then polycrystalline and then amorphous, which is the kind of basic solar cell found in solar-powered calculators, for example. Polycrystalline panels therefore make a good compromise. So how can you spot one? If you look closely at the surface of a polycrystalline solar panel you'll see different coloured patches, like in the picture below:
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