Engineers for a Sustainable World is a non-profit organization working to build a better world. Through collegiate chapters they mobilize students and faculty members, and solicit entries for yearly engineering challenges. In 2011, students from Stanford University were awarded a grant to develop solar-charging stations for the developing world. Their findings and process highlight important aspects of sustainable design and engineering, like understanding user needs, designing for adoption, designing for serviceability, and creating a modular product architecture.
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Research and Understanding Appropriate Technology
During their project, the Stanford team investigated various aspects of developing a solar charging station for a variety of batteries, such as for cell phones or flashlight. They then looked into a variety of technical options to meet these needs. For example, they looked into unique solar concentrating techniques, such as using a catenary curve reflector (the curve taken by a hanging chain). They eventually chose to use a large framed stand with basic solar panels, as the ease of construction and low cost were very important factors.
To deal with the wide variety of batteries that may need charging and voltage output variation of the solar panels, they developed their own charging circuitry. This is extremely important to ensure safe and non-destructive charging. The circuitry and structure utilized readily available off-the-shelf components to reduce cost and ease repair in developing countries.
An Inventor rendering of their initial design
Modifying Designs based on User Needs and Expert Feedback
Perhaps the most interesting aspect of the project was a major shift in design direction taken by the team partway through their prototyping phase.
At first they had worked on developing a large immobile charging kiosk that people could visit to charge their cellphones and other mobile devices. However, after talking with people who had experience developing projects in the developing world, they realized there were several problems with this solution, such as security and capital investment.
By then looking at food carts in many impoverished countries as a design inspiration, they realized the need for a simple, portable, and securable charging station. From this realization came the concept of a modular solar “wheelbarrow.” This design met all of their design criteria, and incorporated the unique ability for independent “charge blocks” to be inserted that would allow for charging of a variety of sizes of batteries.
An example of the food carts that inspired their final design
By developing a robust and easily movable solar charging station the students hope to create a scalable tool for solar charging entrepreneurs to spread throughout the developing world. Their design still needs a great deal of work, but it is a good first step towards a more realistic use of solar energy for much of the world’s population.