Especially for the summer time, there are now more and more creative ideas on the market that enable the mobile generation and use of photovoltaic electricity: the offer ranges from solar fans to solar razors to solar flashlights and even solar swimwear. Solar panels on surfaces convert the energy of sunlight into electricity and thus produce green electricity to take away.
But how suitable are these solar gadgets for everyday use? An overview of the offer:
Solar Power Banks: A power bank serves as a temporary storage for electricity and is suitable as an additional rechargeable battery on the go. With it you can charge your electronic devices such as your mobile phone or tablet. If the battery is equipped with solar cells, you can travel all the longer without worries, according to the promise. The powerbank is recharged again and again with solar energy. Most solar power banks also have a connection for charging at the socket.
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Solar Cell Phone Cases: Mobile phone cases with a built-in solar cell and battery promise the same function. The panel charges an extra battery that supplies the mobile phone with power when needed.
Solar Backpacks: Solar bags are available in a wide variety of designs. A row of solar cells is mounted on the front side. The backpacks usually do not have an integrated power bank, but a USB port where you can directly supply your devices with power. If you only need the power at a later date, you should load an ordinary power bank as a temporary storage device. And when the sun is not shining or all the batteries are already charged, the solar panel can be easily removed in many cases.
Solar Clothing: Again and again, fashion manufacturers are experimenting with photovoltaic modules. The underwear company Triumph presented a swimsuit equipped with solar cells back in 2007. Tommy Hilfiger had developed a solar jacket in 2014 in cooperation with the solar panel manufacturer Pvilion. Some solar garments offer the possibility to charge batteries with the electricity generated. Others use the electricity to warm their carriers.
Solar Bluetooth Speakers and Radios: Portable speakers provide the musical background in the park, on the beach or on the terrace. If you are on the road for a long time and listen to a lot of music, you can also rely on models with an integrated solar panel that supplies the box with power on the go. Some solar speakers even have an additional connection for a mobile phone and thus serve as a power bank at the same time.
Solar lamps, string lights and bicycle lights: The integrated solar cells collect the sunlight and convert the energy into electricity. The electricity is stored in the batteries of the solar lights and can be called up when it gets dark. Some lights also include a twilight sensor that automatically switches on the light as soon as darkness falls.
The solar cell converts sunlight into electricity on the go.
Solar gadgets are not as suitable for everyday use as they initially seem
So there are numerous solar gadgets and thus theoretically a lot of possibilities to charge your own devices on the go. But not all ideas are new, and only a few have so far become established in everyday life – there are reasons for this.
Thomas Seltmann from the consumer Center NRW points out: “With mobile applications, you really have to look closely. Most devices often do not fulfill the functionality that they promise.“
In order to generate a lot of electricity in a short time and thus quickly charge electronic devices, solar panels as large as possible are needed. However, solar gadgets should be used on the go and are therefore small – consequently, the integrated solar panels. Accordingly, the charging process takes a long time.
Numerous consumer tests also show that in order to charge the solar products, it takes not only a lot of patience, but also direct sunlight. “In some cases, it is questionable whether the charge generated by the solar gadgets is really sufficient,” says Martin Heinrich from the Photovoltaics team at the Fraunhofer Institute for Solar Energy Systems. A power bank with a small solar module should already be in full sunshine for a few days, so that it is almost full.
But batteries should not actually lie in the sun. Because heat damages the durability of the batteries and can even be dangerous in the worst case. The Tüv recently warned against the use of power banks at high temperatures and recommended avoiding direct sunlight. If the battery overheats, an internal thermal reaction can be triggered, which in extreme cases leads to an explosion.
According to the recommendation of experts, smartphones and other electronic devices should also be protected from heat and, if possible, stored in cool shade. “If you put the solar-powered batteries in the sun, then for a short time. And you have to check regularly whether it is not getting too hot,” warns Hermann Dinkler, fire and explosion protection expert of the Tüv Association.
Solar panels as an additional charging option
In practice, the devices are therefore not as suitable for everyday use as they seem at first glance. With the right expectations, consumers can still benefit from solar energy even when traveling.
There are certainly useful solar gadgets. “What works is small, economical applications such as a radio, a little bit of LED light,” explains Björn Hemmann from the German Solar Energy Society. You can also charge a battery with a solar backpack. That’s enough to listen to music for two to three hours. But then the electricity would also be gone quickly.
The solar panels on the devices can also be used as an additional charging option. If you charge your power bank with conventional electricity before the trip and recharge it again and again on the road when the sun is shining, you can at least use your devices for longer.
The electricity is stored in the batteries of the solar lights and can be called up when it gets dark.
Photo: Little Sun
“You should think in advance why you need solar energy on the road,” advises Hemmann. One has to distinguish whether one is really dependent on electricity or whether one would like to benefit from solar energy, but could get the electricity elsewhere in an emergency.
According to Hemmann, if you need more energy, for example for a cooler, you have to think in square meters rather than in DIN A4 sizes when it comes to the size of the solar panels, so that you really benefit from it.
Experts advise on external panels
For an additional power supply on the go, experts advise using a separate solar panel. “What works very well as an alternative is a foldable solar module. With a cable you connect it to a device that is in the shade,“ recommends Heinrich. The panels are available in different sizes, and they can be folded – so they also fit in a backpack.
The variant solves two problems at once: on the one hand, the panel is much larger than with mobile solar gadgets and thus produces much more electricity in a shorter time. On the other hand, this solution also avoids the heat problem. Because the external panel works outdoors even when the sky is overcast.
Unlike solar power banks, panels do not store the electricity themselves, but a commercially available power bank with a USB connection can be attached as a temporary storage device.
Power banks are available in different sizes. If you want to charge larger devices such as a laptop, you have to invest a little more and also choose larger panels. “You can produce any power supply with photovoltaics. It’s always a question of effort and what you want to achieve with it,“ explains Seltmann.
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