The Little Sun project is an example where you can see the combination of “design” and an idea of energy harvesting, being esthetical and at the same time benefitting people in Africa.
http://www.littlesun.com/
From the project site:
“Launched in July 2012 at London’s Tate Modern”. (citation from the site)
This already is interesting, that this kind of project is started at a Museum for Modern Art. This clearly shows the interest for and repercussions of “Design”.
Also:
“Was recently introduced into Centre Pompidou’s permanent design collection and has been nominated for Design Museum’s 2013 Designs of the Year Award”. (citation from the site)
It certainly has an impact, because already 200.000 of these energy harvesting devices have been sold. (Again according to the site.)
The price for Europe and the USA is 22 euro’s. For Africa it is 9.60 dollar.
Pictures (my own) of the little sun:
https://www.flickr.com/photos/contrechoc/sets/72157649652696089/
Design side
The Design side of this product is twofold. Basically it is a solar panel which three batteries, and a very bright LED. These technical parts are contained in a playfully designed circular object which has the shape, color and rays of the Sun.
The second part of the Design is the goal or the mission of the project, giving clean electricity to Africa. The selling of this item should also strengthen local entrepreneurship.
Technical side
This design object can be compared to three other setups that are under investigation in this research:
- A DIY setup with a solar panel and an LTC chip charging a Lipo
- A Chinese gadget garden lamp of 2-3 euro’s.
- A conventional charger with a solar panel and lipo batteries, which can be bought nearly everywhere for 5 – 15 euro’s.
Pictures of these comparable setups (from the technical point of view):
Charging my cellphone with solar panels and an LTC harvesting chip
The Chinese gadget chargeable garden lamp is fun and cheap (2-3 euro’s), it has a “smart” chip which charges in the sun and lets the LED’s shine at night, but it has one big disadvantage: no protection against over-charging. Eventually the battery inside is damaged and the gadget doesn’t work anymore.
See also:
https://www.flickr.com/photos/contrechoc/sets/72157647755005814/
The solar charging device can be bought for around 15 euro’s and charges cell phones etc. It takes two days of full sun to charge and has than capacity for half charging my cell phone. In the Dutch climate it only “works” in the summer and in full sunshine.
This charger has basic design (or non at all). On the other hand it has indicators of the rate of being charged, and a switch to select the output voltage (from 5 to 9 V). This means this device has some sort of an harvesting step up chip inside. There are no screws visible, so opening this device means destroying the casing – the circuit is not checked.
This device is comparable to the Little Sun in function and charging time. The Little Sun is lacking some kind of charging indication compared to this solar charger.
see also:
https://www.flickr.com/photos/contrechoc/sets/72157649679173918/
Little Sun will work in Africa with it’s full sun. In Europe with all the clouds it will sometimes take long to charge it.
Effect
The amount of light coming from the very bright LED on Little Sun is “blinding”, but not comparable to normal lighting of a room at night as we (Europeans) are used to. The light effect is that of a light torch, you can read when you shine upon a book, but you don’t have the feeling of being in a light environment.
Circuit
The Little Sun is certified and there are many items sold, so I suppose there is a protection against over charging (which happens to the Chinese gadgets.). I could not open the Little Sun (it was a present of a friend to his son :-)) to inspect the electronics. On the site there is a page about the circuit, but it doesn’t has information about battery protection or if it has an energy harvesting chip, how it has balanced the charging and the load etc.
Conclusion
The Little Sun has appeal because of it’s nice shape and color design. This esthetical side sells the product reminding (conforting) us of “good deeds” we have done for “the poor people” of Africa. Probably we here in Europe (Holland, Germany) can only use it in full summer and even then we need some very beautiful sunny days.
In Africa the energy used for this product is “clean”. On the other hand the amount of energy harvested in the end is tiny and inefficient compared to bigger setups. “Normal” amounts of energy will be harvested by bigger solar panels. Little Sun will stay a toy and serve more the purpose of making us conscious of energy than be of pratcial use.
Comparing the irradiance (solar energy received from the sun on a surface) for Rotterdam and Rabat ( Morocco, Africa):
from: http://solarelectricityhandbook.com/solar-irradiance.html
You see that a surface in Morocco receives about twice as much energy if the Sun is around, because you have to take cloudy days into account. ( http://www.currentresults.com/Weather/Netherlands/sunshine-annual-average.php )
Rotterdam:1624 hours of Sun
Rabat: 3000 hours of Sun.
So not only is the amount of energy twice as much, the time the Sun is really shining on your solar cell is also around twice as much!
making Africa getting around 4 times more solar energy.
Of course this is energy from the Sun, which has to be transformed in electricity.
http://en.wikipedia.org/wiki/Solar_cell_efficiency#mediaviewer/File:PVeff%28rev141208%29.jpg
On this plot you can see that the most efficient cells nowadays transform 44% of the energy of the Sun, average is around 20% efficiency.
energyharvestingresearch 
