Nick Jones

A couple of weeks ago Samsung announced a “Blue Earth” mobile phone with built-in solar cells for charging. My initial reaction was that this sounded like a good idea; but then I asked a few questions and am now feeling much less positive for two reasons:

Practicality.Samsung tell me that a full charge of Blue Earth using solar cells alone takes around 15 hours. So in a UK winter that’s 2 days when a phone would have to be by a window rather than in my pocket. And on many days I’d be using energy by talking faster than I could replenish it by solar charging. So from that perspective this looks a bit impractical even when the sun is shining, which is often not the case here in London. At best the solar cells might top up the handset a bit but would seldom charge it fully.

Embodied energy. A more serious worry is whether solar cells in a handset can ever pay back their manufacturing energy debt. Calculating such debts is a contentious and confusing activity but some of the articles I’ve seen suggest that domestic generating installations of photovoltaic (PV) cells need to run for somewhere in the range 2 to 8 years just to generate the energy that was used in their manufacture. And these calculations assume cells which are operating continuously during the hours of daylight. PV cells in a phone which might only be in the sun for a small fraction of daylight hours might take one or two decades to pay back their embodied energy debt. And the life of a handset is far less than that.

So based on what I know at the moment putting solar cells into a handset has a negative environmental impact. They can’t replace the charger and it looks as if they won’t ever repay their embodied energy debt. I’ve asked Samsung to comment and will pass on any interesting information if I learn more.