Solar power isn't used for mobile phones? My previous mobile lasted 11 days on 1 charge. Surely a small solar cell could collect enough light in 11 days to charge the battery? Then we'd have a phone that never needed charging!! Wouldn't work with these new phones with huge color screens though. :-)
A solar cell small enough to fit on a mobile almost certainly wouldn't generate enough charge to be useful. You could do the numbers to find out based on average solar insolation, surface area, efficiency etc
But then you add in all the other practical usability factors like:
1) Many people put them in a case of some sort
2) Solar cell would have to be on the back of the phone to get the most useful surface area, and people like to keep their phone face up so they can see the screen. "Flip" phones with the small front LCD are a bit better in this respect I guess.
3) Solar exposure would be very low. Most people would keep them indoors or in their back pocket or bag etc, and of course it's useless at night. Usable expose could be as low as few hours a days or less.
4) Adds extra cost, so those models simply won't sell in the cuthroat market. Try making it look sexy too...
5) People don't want the inconvenience of remembering to leave it in the sun or other light, esp considering that plugging it in for 30min while in the car will generate more charge than a week in the sun.
6) A big proportion of the market (i.e. teens) use their phone 50 times a day on their $300/month plan, that means much higher battery usage than someone like me who is lucky to use it once a week.
I don't think any of these issues are insumountable though. For example, heavy users would just need to charge the phone. However looking at this site
it looks like a 1" x 2.5" solar cell will be out 0.240 watts in ideal conditions (I presume they're quoting ideal conditions). The nokia 6310 has a 600mAh battery which divided over 11 days gives an average of 0.002 watts. So the cell is putting out 120x the power required by the phone. With inefficiencies, time not in light, lower output from indoor lighting and a smaller solar cell we might still make it.
The 1 x 2.5" cell is $1.60, most likely a lot cheaper in bulk.
The idea would be they wouldn't have to remember, incidental light during the day would be enough.
I calculate 8mW ((600mAh/264h)*3.6V). Not that it really matters, factor in the multitude of practical engineering issues and it looks bleak. Eg. you have to have multiple cells in series to get the voltage needed, extra charging circuitry of some sort, inefficiency in the charging circuitry and the battery at low charge currents, indoor lighting is quite a large difference etc etc Read below for how much time my phone spends in any form of light, let alone full sun.
I think you'll find if you did a proper engineering analysis taking everything into account, then it just isn't practical.
To a mass market item like this, that's a LOT of money. Every single cent counts in high volume consumer items like this.
Really? I don't know if I'm an "average" user or not, but I would be lucky if my phone spends a few percent of an average week in any sort of ambient light let alone full sun. I leave it in my bag at work and home, if I go out it's in my back pocket, when I go to the gym it's in my bumbag, when I'm out adventuring it's in the pack etc. In fact the only time it's really getting any light is when I use it or I'm charging it! So I would have to drastically change the usage of my phone to get any benefit at all from solar power.
I agree with points 1), 3) and Dave except you can change peoples habits in regards to usage and storage with design. You could bring back the nineties trend of hanging your mobile from your belt/pocket/other for example plus in areas with unreliable power it would be great and with phones turning into PPC's cameras and diaries the demand for power and having a charged unit will be higher. Other people that could be sold on this idea apart from people who are caught out with a flat battery (I haven't in years) are people who like camping, boating, fishing, push bike riding, motorcycle riding, horse riding.................. Another plus is more phones would be stolen and then in turn more sold. It's not a feature I would look for or consider and advantage.
Sure you can, and any manufacturer is willing to try if they want. I won't change though just so I can get some trickle charge here and there.
No good if the cell has to be on the back of the phone. And not much good if you are indoors all day anyway. Driving too and from work you'd have to stick the thing on the dash, that sucks when you can just plug it into your cigarette plug and charge it 10 times quicker.
and with phones getting smaller and smaller where do you put the solar cell?
Just use a seperate solar charger - hey another accesory they can sell...
When I go bush I turn my phone off, peace and quiet.
I don't think anyone would. All the market cars about is how many MP the camera is and how the ring tones sound.
Surely they could design the cells to output the voltage required.
Maybe so but they still manage to put out phones with 3.2mp cameras, 320x240 color screens, 4gb hard drives, a second camera, a second lcd display, radios, sd cards, headsets, usb cables etc etc etc.
I don't think you're an average user. I leave my phone on the table the entire time I'm home, I have on my desk most of the time I'm at work, I take it out of my pocket in the car in case it rings. I'd say it would be in some sort of light for 10 hours a day.
I think the real killer though would be it's just not cool enough.
Sure, but the point is that having to do so reduces the effective area of the cell. That is particually important for small applications like this.
So where does that leave room for the solar cells? :->
Most people I know are the same as me. Still may not be "average", but's that's good enough for me to know that for myself and most people I know, it would be a waste of time.
Most of time you have your phone on the desk at work or home you are only getting very inefficient fluorescent lighting. I've got one of those solar powered Citizen Eco watches, and they are really cool, but they don't work very well in fluorescent lighting. 30 minutes in the full sun is much better than days in a room. In fact, if I leave it on the table in a room it eventually dies through lack of charge. And this uses a "specially designed" cell that is supposed to work in all types of ambient light.
Also, if you are in the car why not simply plug it into your car charger that can charge it 10 times quicker?
No, I think the real killer is that it's most likely quite difficult from a manufacturing and engineering point of view. It being of little benefit is beside the point really I guess, it never stops the marketing department! Solar power is very "cool", and it would I suspect be a good marketing gimmick, but no one has ever done it - why? The cheap "clamshell" construction of todays phones would probably not lend itself well to adding any sort of solar cell. It ain't as easy as looking at a data sheet and saying, hey this could work, there is a massive amount of engineering and packaging work involved, the devil is in the detail.
Obviously this would have to be a low feature business phone. Before you say who'd buy it, try buying a nokia 6310i. They're still up around $200 when I can get the new nokia wizz bang phone for the same price.
That is simply not true. Most people don't have their phone in their pocket all day. Everywhere I go I see mobile phones on desks and all day at work the damn things are ringing and no one's there to answer them. Most people put them out somewhere at home so they can hear them ringing.
Funny you should mention that I've got that same watch, the WR100. I've never had it stop in 5+ years and it's the reason I'm posting this thread :-) It's such a cool idea, I never have to worry about batteries, the watch just runs, forever.
I don't have a car charger. I probably need one but am sick of buying chargers for everything. I've also got a bluetooth headset, laptop and digital camera that could do with car chargers. I find them a hassle having those cords in the car and the contact with the lighter socket is never very good.
Dunno, i think if they wanted to do it they could. They could probably integrate the solar cell into the LCD display which would give plenty of room. There are patents for solar cells integrated into laptop displays. Or they could have some sort of clear keyboard and put it behind that. Or as you said have it on the front of a flip phone.
Well, when you're away from the charger and the phone would otherwise be dead I could see it as a huge benefit.
As I said if they really wanted to do it they could.
It is true for most people I know. As for my work place, hardly anyone leaves their mobile on their desk. Your experience is obviously opposite to mine, so that must mean half the people leave it out and half leave it away? :->
Not that it matters, fluorescent light just isn't very efficient.
Mine is a dress watch so spends most of it's time on the table. If it doesn't get direct sunlight it will die after a few months. So fluorescent light can barely cut it for a watch, let alone a phone. Watches have a massively lower power requirement than a mobile phone, in the order of a few microwatts.
Get a phone car charger at least, they cost a few dollars and will save your sanity. I find the most conveinet time to charge my phone is in the car.
Of course they could, but your question was "Is there any reason solar power isn't used for mobile phones?" There are many reasons as I've gievn, plus there are many more if you actually do a full enginering and cost/complexity/benefit analysis, which no one but the phone manufacturer is capable of doing really. That doesn't mean someone won't eventually do it though, if it can be done it probably will be done. Just don't expect it to be practical like your solar powered watch.
BTW, some of the new Casio watches have a 10 year battery life, no need for solar at all. Impressive stuff.
My EcoDrive watch is smart too, when the battery gets low it first goes into a "lower power" mode that doesn't move the second hand to save power. Then if the battery gets even lower it stops all hand movement, but not before shifting the hands to a position which indicates "charge me", and it still keeps the time going internally. Then if it finally doesn't get any charge, as it's last gasp of breath it moves the hands to a position which indicates "time lost". If you charge it back up before it loses the time it moves the hands back to the correct position. Very cool.
Possibly but that just means the technology wouldn't work for some people. The phone would have to come with a charger anyway so those people would just have to charge it, but at least less often.
I'd be interested to see exactly how much power could be extracted from fluros.
We don't really know how they've implemented it though. The face of the watch doesn't look like a solar cell so I suspect it is behind the face. The actuall cell itself might be very small and most of the light might be blocked by the face.
I probably should.
You've raised a lot of good points although I don't think any of them are show stoppers except possibly for the amount of power that can be taken from indoor light. But we don't have any real data on that, just something I got from a website and your estimations.
Shows a "cloudy day" is 3-4 times better than indoor lighting, and that's 20cm under a 30W fluoro! The difference between a full sunny day with high solar radiation and a typical room in which you aren't 20cm away from the fluoro tube would have to be at least an order of magnitude.
Shows that due to the super efficent cell used the new ulta low power technology, the face can be only 20% transparent and still work well enough.
Slightly askew of the topic, but I've thought it would be a good idea to get rid of the cigarette lighter socket altogether and standardise on a more appropriate power supply adaptor with multiple connection points throughout the vehicle, since most people use the socket for power supply rather than lighting cigarettes these days. I'm surprised this hasn't happened already.