Keeping your gadgets going with power is tricky business, which is a little unusual when you consider that there's an immense source of power constantly erupting over our heads. At a gadget level, there's plenty of solar chargers out there, but uptake has been relatively slow -- and for a very good reason. There's certainly no shortage of solar-powered chargers for your gadgets, with everything from the bigger, better known brand names -- things like Powertraveller's Powermonkey series, for example -- right down to more DIY installations.
We've got plenty of sun in Australia -- well, OK, as I write this, Sydney is blanketed in torrential rain, which isn't going to help any solar gadget, but I've got faith that at some point the sun will peek back through the clouds. I hope.
Plenty of sun plus solar powered chargers should be the most obvious solution in the world, and it certainly has its place in some home solar installations to go partially or fully off-grid, but at the smaller charger level, it's worth noting that things don't often go that smoothly, as the reality of using a solar charger for day to day gadget work can be more than a touch frustrating.
The reason for this is quite simple; while most of them work well at providing power to your gadgets, getting power back into them is a much more convoluted process, and one that's not all that well suited to the small size of the photovoltaic cells that actually perform the power generation. In order to understand why, it's worth dipping briefly into the science behind solar power generation.
Sunlight travels to earth in the form of photons, and photons that hit a photovoltaic cell such as those found in solar chargers knock loose the electrons between two semiconducting layers. This creates a electrical potential difference that means a current begins to flow; in most solar cells that current is captured in a battery that then goes on to supply a steady charge out to whatever needs the power. It's theoretically possible to charge something directly from the sunlight captured by a photovoltaic cell, but the rapid changes in intensity of sunlight makes it inadvisable, as you're never going to get the kind of regular power flow most gadgets require.
That works well enough over time for, say, a large house installation where a huge surface area of combined cells can generate large amounts of power, but on the smaller panels found with most portable solar chargers, there's a lot less capability for power creation. It gets worse when you realise that the angle of the cells relative to the sun also affects the level of charge created. Again, for something that's in a fixed position this isn't as much of a problem, but when you're using a small portable cell, a difference in angle relative to the sun can have a large effect on the amount of current generated.
What all this boils down to is exceptionally slow charging times; it's not uncommon to see solar charging units that come with mains chargers for their batteries as well, and that's because the difference in charging times can be considerable. Experimentally some years back, I drove in the middle of Summer from Adelaide to Sydney with a Powermonkey Xplorer blu-tacked to the dashboard of my car. After some eighteen hours of driving (not all of it under direct sunlight, of course), I'd managed to charge up a bar on the supplied battery, thanks to the changing angle of the car as I moved around, and the relatively low power generation of the cell. Two hours after reaching my destination and plugging the same battery into a mains socket plug, it was 100 per cent full.
Does that mean that solar power is bunk? No, not at all, but it's a question of appropriate use for appropriate outcomes. It's still relatively clean energy with zero emissions in use, and the actual source of it is effectively inexhaustible -- or certainly moreso than the expected life of your gadgets, anyway! It may be worthwhile picking up a small solar charger, as long as it wasn't your sole source of charging -- most gadgets will simply use more power than you can easily generate over a given day.