How useful is solar energy to go?

Especially for the summer, 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 with you.

But how suitable are these solar gadgets really for everyday use? An overview of the offer:

Solar-Powerbanks: A power bank serves as intermediate storage for electricity and is suitable as an additional battery on the go. You can use it to charge your electronic devices such as your cell phone or tablet. If the battery is equipped with solar cells, the longer you can travel without worries, so the promise. The power bank is repeatedly recharged with solar energy. Most solar power banks also have a connection for charging at the socket.

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Solar cell phone cases: Cell phone cases with built-in solar cells and batteries promise the same function. The panel charges an extra battery that supplies the mobile phone with power when required.

Solar backpacks: Solar bags are available in a wide variety of designs. A number of solar cells are attached to the front. Most of the backpacks do not have an integrated power bank, but instead have a USB port that can be used to directly power your devices. If you only need the electricity at a later point in time, you should charge a normal power bank as a buffer. And if the sun is not shining or all batteries are already charged, the solar panel can often be easily removed.

Solar clothing: Fashion manufacturers are also repeatedly experimenting with photovoltaic modules. In 2007, the underwear company Triumph presented a bathing suit equipped with solar cells. In 2014, Tommy Hilfiger developed a solar jacket in collaboration with the solar panel manufacturer Pvilion. Some solar clothing offers the option of charging batteries with the electricity generated. Others use the electricity to warm their wearers.

Solar bluetooth speakers and radios: Portable loudspeakers provide background music 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 cell phone and thus also serve as a power bank.

Solar lamps, light chains 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 contain a twilight sensor that automatically switches the light on as soon as it gets dark.


The solar cell converts sunlight into electricity on the way.

Foto: Sunnybag

Solar gadgets are not as suitable for everyday use as they initially appear

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 established themselves in everyday life – there are reasons for this.

Thomas Seltmann from the NRW consumer advice center points out: “With mobile applications, you really have to look carefully. Most devices often do not deliver the functionality they promise. “

In order to generate a lot of electricity in a short time and thus quickly charge electronic devices, solar panels that are as large as possible are required. However, solar gadgets should be used on the go and are therefore small – consequently so are the integrated solar panels. The charging process takes a correspondingly long time.

Numerous consumer tests also show that charging solar products not only takes a lot of patience, but also direct sunlight. “In some cases, it is questionable whether the charge generated with 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 has to lie in the blazing sunshine for a few days so that it can begin to get full.

But batteries shouldn’t actually be in the sun. Because heat damages the durability of the batteries and in the worst case can even be dangerous. The TÜV only recently warned against using 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 can lead 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 a cool shade. “If you put the solar-powered batteries in the sun, then for a short time. And you have to regularly check that it is not getting too hot, ”warns Hermann Dinkler, fire and explosion protection expert at the TÜV association.

Solar panels as an additional charging option

In practice, the devices are therefore not as suitable for everyday use as they appear at first glance. With the right expectations, consumers can still benefit from solar energy while traveling.

There are definitely sensible solar gadgets. “What works are small, economical applications like a radio, a little bit of LED light,” explains Björn Hemmann from the German Society for Solar Energy. You can also charge a battery with a solar backpack. That’s enough to listen to two to three hours of music. Then the electricity is 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 your trip and recharge it again and again when the sun is shining, you can at least use your devices for longer.

Solar lamp

The electricity is stored in the batteries of the solar lights and can be called up when it gets dark.

Foto: Little Sun

“You should think about what you need solar energy for when you are out and about,” advises Hemmann. You have to distinguish whether you really need electricity or whether you would like to benefit from solar energy, but can get the electricity somewhere else in an emergency.

According to Hemmann, those who need more energy, for example for a cool box, have to think in terms of the size of the solar panels in terms of square meters rather than DIN A4 sizes in order to really benefit from them.

Experts recommend external panels

Experts recommend a separate solar panel for an additional power supply when you are out and about. “What works very well as an alternative is a fold-out solar module. A cable is used to connect this to a device that is in the shade, ”recommends Heinrich. The panels are available in different sizes and they can be folded up – so they also fit in a backpack.

The variant solves two problems at the same time: On the one hand, the panel is significantly larger than with mobile solar gadgets and thus produces significantly 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 standard power bank with a USB connection can be attached as temporary storage.

Power banks come in different sizes. If you want to charge larger devices such as a laptop, you have to invest a little more and choose larger panels. “You can produce any type of power supply with photovoltaics. It’s always a question of effort and what you want to achieve with it, ”explains Seltmann.

More: Energy industry wants to spark the photovoltaic boom


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