Problem
Rural communities in Africa, South America, and other parts of the world have limited access to conventional power; portable generator carts, the common alternative, are expensive to acquire and operate (some pay as much as $40 per kilowatt hour). The lack of accessible power has however not hindered the growth of mobile phone users. A country like Ghana for example has about 88% of its population being active mobile phone users whereas just about 20% of its rural population have direct access to electricity. With northern and southern parts of Africa being an exception, much of the continent experiences about 8 - 10 sunshine hours per day, which makes it good ground for harvesting solar energy.
Customer
HCJB Global, a non-denominational, non-profit, evangelical
missionary organization proposed a design competition amongst Christian
colleges to develop a solar-powered community lamppost with portable
device charging capabilities. This model would imply a proprietor for
the lamppost who would maintain the security of the charging devices, a
feature that should be of interest to the “Business as Missions” and
micro-business communities. The lamppost would allow for devices to be
recharged day or night and enough power generated to provide light at
night.
Solution
The solution to this problem is a solar-powered lamppost that is able to provide light at night for the people of these communities, and fitted with USB charging ports to enable charging of mobile phones. The system will consist of a 50-Watt solar panel mounted on a 18 - 21 foot Schedule-40 galvanized steel pole, with an 8-Watt LED bulb serving as the source of light. Power from the solar panels would be stored in two separate AGM Lead-Acid batteries - one to provide power for the light and the other to power the charging ports. The block diagram below shows an overview of the system architecture:
General Facts
- Operating temperature 0 - 130 F
- Power consumption of LED bulb 8 Watts
- Approximately 7 hours of direct sunlight will fully charge the system
- Up to 2 days of reserve power to allow of successive cloudy days
- An ambient light sensor controls automatic on and off illumination
- System feedback provided by LCD screen
- Estimated usage before maintenance 3 - 4 years
Electrical System
- Operating voltage 12 V
- 50 Watt polycrystalline solar panel
- Switched-mode power supplies with up to 80% efficiency
- Solar controllers with Maximum Power Point Tracking
- Universal USB charger
- Interactive user interface
Mechanical Structure
- Completely weatherproof
- Withstand winds up to 60 mph
- Entire structure (besides pole) is collapsible into 30" suitcase for shipping
- Can be assembled with basic hand tools in 2 hours
- Lockable enclosures for added security
