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DC-only Solar PV Deployment at Haitian School to Charge 500 Laptops

By Laura Hosman
August 18, 2011   |   6 Comments

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6 Reader Comments
Comment
1 of 6
August 20, 2011
DC-only Solar PV to power Laptops in Haiti - very interesting. Yes. DC PV can be a boon in developing countries.

Dr.A.jagadeesh Nellore(AP),India
Wind Energy Expert
E-mail: anumakonda.jagadeesh@gmail.com
Comment
2 of 6
August 23, 2011
Electrotech 101-let's not forget the voltage drops that'll curse low voltage DC supplies unless thick & costly copper wiring is used! This naturally was a major reason behind the adoption of AC back in the 1890s. Higher voltages mean lower currents & thus less line loss for the same power. Given the high global cost of copper,thinner supply wires are often being used, and even a few 10s of metres/yards at 12V may suffer significant losses.

Silicon is often now cheaper than copper - & less likely to be stolen! Sine wave inverters are highly efficient & increasingly cost effective. In such applications it's often better to invert to mains voltage very early on.

IMHO using PV energy just to charge laptops is very short sighted, especially given the usually more pressing need to run LED night lighting & charge cell phones. The rapid rise of smart phones means today's laptops may soon be quaint items as well!
Comment
3 of 6
August 23, 2011
For this project, the grid electric network has failed and recharging the "existing" laptops became impossible. To keep system cost affordable (no expensive inverters) and to prevent energy diversion (plugging in any AC powered device), the system was designed DC only. The focused project goal was to recharge laptops only, not lighting, cell phone charging, air conditioning, etc. Since laptops run on DC why convert from DC to AC then convert from AC to DC again? So this was a very purpose built solution, not a general school electrification project. The laptops are charged in one room then taken to the class rooms each day and returned for charging. Keeping the solution DC reduced project costs and kept the system straight forward and simple.
Comment
4 of 6
August 23, 2011
Aircon. is a power hog, so forget it in such skinflint setups. But-argh-you mean there's now NO ELECTRIC LIGHTING in the classrooms?! Surely this is a TOP priority, especially given the wonderful efficiency of today's LED systems! I consider suitable lighting essential in education, especially in the tropics where building interiors are often very dark. The ability to use the rooms after sunset will also then be beneficial.

FWIW,for just a few hundred $US,high efficiency pure sine wave inverters (running off perhaps a couple of 12 V automotive batteries)could provide mains voltages for conveniently powering low drain devices. There's always a demand for running printers, small TVs and (yes!) cell phones in schools. If the grid has failed for the school then it's probably down for neighvours as well,& such a charging availability could be a welcome community service- especially at weekends.

I repeat that heavy duty copper cabling is valuable,& hence may be stolen.This alone is often reason enough to use an inverter - "silicon is cheaper than copper".
Comment
5 of 6
August 23, 2011
Interesting work. I worked on a simlar 12V system in Kenya once using white LED lights. Here is a paper I wrote about it, if you are interested: http://library.queensu.ca/ojs/index.php/ijsle/article/view/2089/2189

Also, I recently wrote about a biogas/biomas system I toured in Honduras. It was fascinating: http://lifeobservationsfromorangehouse.blogspot.com/2011/08/african-palm-trees-real-power-plant.html
Comment
6 of 6
August 24, 2011
Orangehouse: An interesting project indeed. Since that time (assumed 2006?)solar PV cost have fallen, fuel costs have risen and LEDs have become brighter AND cheaper. Off grid solar lighting projects hence have become even more viable.

FWIW observers have noted LED developments tend to follow the so called "Haitz's Law" (a LED equivalent of Moores Law) -see =>http://en.wikipedia.org/wiki/Haitz%27s_Law.
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Laura Hosman

View Laura Hosman's Profile
About: Laura Hosman is Assistant Professor of Political Science in the Department of Social Sciences at Illinois Institute of Technology. Prior to IIT, Professor Hosma... more »

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