The purpose of this article is to give a brief overview of how we solved a common infrastructure problem for rural schools in Haiti. Hopefully, this page will provide useful guidelines which could be used all over the world in any context where electricity is necessary but not readily available. I’ll start with a few of the concerns our “Suitcase Solar” power system was meant to address: Cost, Portability, Security, Reliability, and Usability.
What does the solar system consist of?
In general a solar system will need the following… (You can find a list of the actual parts we used below.)
- Solar Panel
- Charge Controller
- Deep-Cycle Battery (Gel (zero-maintenance) or Flooded (longer-lasting))
- Clamps (It is a good idea to clamp the wires to the solar panel or panel frame to relieve stress on the soldered connections at the panel)
- Voltmeter / Multimeter
- Inverter, if you need it (Our XO Laptops do not need an inverter as they can charge from DC)
The cost of a solar power system puts it out of reach for many schools, especially in the rural areas where these systems are most needed. As such, we solicited donations and/or self-funded these projects. Since Haiti is an island nation, the cost of materials are often inflated. It made sense to us to buy whatever we could in the United States and bring it along. The panel, charge controller, wires, and connectors were bought in the United States, mostly from amazon.com. We bought the battery in Haiti, in Port-au-Prince, at a large store called “MSC Plus.” Shipping batteries seems to carry extra fees as the battery contains dangerous chemicals, so it is probably best to buy your batteries at your destination when possible.
Our deployment teams tend to be small, sometimes just a single person with an extremely small budget. What we basically needed was a whole solar power solution that could be brought to the deployment in one trip on a motorcycle. We found portable “rollout” solar panels that made this possible. The battery is heavy and the solar panel is large, but you can fit this whole system in one large backpack.
While I found Haiti to be pretty safe, security is a major concern of the local population. Solar panels are pretty precious, so there is always a chance that they will be stolen if left out, especially overnight. This is another place where the rollout solar panel has a great advantage. It can be rolled out in the morning, and then rolled up and locked away at night when it won’t be useful anyway. Theft of the battery and charge controller is also a concern. In some cases, these elements can be kept in a locked room indoors with wires run permanently to the panel on the roof with quick-release connectors. Ideally the quick-release connectors would be color-coded or numbers to prevent accidentally switching the positive and negative feeds and potentially ruining the battery.
Reliable parts are expensive, but it is far more expensive if you have to return to your deployment to fix or replace something. In our experience, it is critically important to get a charge controller that is robust enough to handle more load than you plan on drawing. The other parts we have found fairly reliable. You can find links to the products we used (or similar products) at the bottom of this page.
Some team of local staff, volunteers, students or other people should be trained in how to hook up all the equipment. As I mentioned before, I think color-coding is a good solution to ensure positive and negative leads are not crossed. Be sure to test thoroughly and find any potential issues and train for them. In our case, the charge controller needs to be set manually for Battery Type and Charging Mode. There is a chart in the manual which specifies which Battery Type to use for Gel-type batteries or Flooded batteries. For Charging Mode we set it to “Always On,” which disabled a built-in timer function. All of this is set with one button, tapping it to select the function, holding it to get to “edit mode,” and then tapping again to change the selected setting. When you find the selection you want, you have to touch nothing, after several seconds, the setting will be saved. Figuring this out took some time and we put stars next to the relevant settings in the manual which we left with the local staff. Furthermore, each time you tap that button, it toggles the output of the charge controller on and off. We went over this several times with the local staff, basically saying that if you’re getting no output, just tap this button once and measure again. The single-button toggled output is a big enough issue that I will be looking for another charge controller for future deployments.
Our Setup at Ferrier School
Below is the list of parts we used, with notes, and with links for purchasing the same or similar products.
Solar Panel: UNISOLAR PVL 136 Watt 24V Panel (~$200)
Note that if using a 12V battery, you’ll need a charge controller that can handle the 24V to 12V conversion. Even though the panel supposedly outputs at 24V, we measured over 40V of output in full sun directly from the panel to the multimeter. This likely overloaded the first charge controller we used (as well as a spare unit), requiring a second visit to install a “beefier” model.
Unfortunately, these panels are can be hard to find, but can often be found on eBay.
Currently, a third-party is selling them at amazon.com for about $200:
Charge Controller: MPPT Tracer1210RN (~$80)
The thing to look out for here is the single button.
Tapping the button will change cycle through “settings” display AS WELL AS toggle the output (powering your device(s)) ON and OFF. This can be very confusing because once you’ve gone through and set the battery type, and set the mode to “always on,” you have a 50% chance of measuring no voltage at the output leads. The LEDs will all look lit up and correct, causing more confusion. If you’re not seeing any voltage, tap the button and remeasure. It’s probably a good idea to read the manual beforehand, and print and leave on behind for whoever will maintain the system, highlighting the correct settings.
The part we used is available from Amazon for about $80 (and has been updated to a MPPT Tracer1215RN): http://www.amazon.com/gp/product/B008KWPGS6?tag=s601000020-20
Deep-Cycle Battery: (~$250 USD in Port-au-Prince Haiti from MSC Plus)
We decided on a “Flooded” battery since the local staff had experience with flooded batteries and this style of battery lasts longer. We also left a gallon of distilled water and a battery water tester at the school. From what I was told, if maintained, Flooded batteries last longer, but if not maintained, they will lose their ability to hold charge after several months. If you aren’t sure that the locals can and will maintain the battery, you should probably go with the Gel type. The Gel type was also slightly more expensive for the same amp-hours, about $280 vs $250.
Flooded type Trojan J150 (similar to what we used): http://www.amazon.com/Trojan-J150-150AH-Flooded-Battery/dp/B009M7AXI6/ref=sr_1_4?ie=UTF8&qid=1392846680&sr=8-4&keywords=trojan+battery
Gel type: VMAX MR127 http://www.amazon.com/VMAXTANKS-VMAX-MR127-Ebbtide-trolling/dp/B0087FQLDU/ref=sr_1_2?ie=UTF8&qid=1392847026&sr=8-2&keywords=trojan+battery+gel+12v
Battery Hydrometer (for Flooded Batteries): (~$15-30) http://www.amazon.com/E-Z-Red-SP101-Battery-Hydrometer/dp/B000JFHMRU/ref=sr_1_1?ie=UTF8&qid=1403250225&sr=8-1&keywords=battery+hydrometer
Be sure to get enough, as in, it’s best to get a good deal more than you think you’ll need.
Wire Connectors, Multi Tool Stripper, Cutter & Crimper:
Neiko 175 Pieces Solderless Wire Terminal & Connection with Wire Stripper Crimper Tool
This kit has most of what you’re likely to need. If you plan to do a complicated setup, you may need extra connectors.
Multimeter: ($20 – $200)
The higher the accuracy the higher the cost. If you will do multiple deployments or if accurate measurements are a priority, it’s probably worth getting a good, reliable model.
More Accurate: http://www.amazon.com/Fluke-117-Electricians-True-Multimeter/dp/B000O3LUEI/ref=sr_1_9?ie=UTF8&qid=1392848199&sr=8-9&keywords=multimeter
Putting it all together
These parts combine into a cheap and simple yet flexible and highly practical classroom solar system. For this project, we spent less than $600 on equipment (other main expenses being time to setup and the costs of transportation. Follow our blog for more stories of success and failure in our off-the-grid deployments.