Solar Cell Phone Charger Nicaragua, Spring 2011

Project Goals To design and develop a simple low cost solar cellphone charger such that the end product costs less than $20 and can be built indigenously.

Background Sabana Grande is a district in rural Nicaragua that does not have access to grid electricity. However, a number of the locals in the area use mobile phones. A lack of accessible power outlets requires them to pay shopkeepers in the city of Ocotal (half an hour away by car) to get their phones recharged and they do so once or twice a week on average.

Problem They are often over charged and exploited by the people who charge their mobile phones. It is also extremely inconvenient to have to go in to the city to charge their phones.

Sidhant Pai Department of Civil and Environmental Engineering

Visit to Nicaragua Over Spring Break 2011, my team and I stayed in Sabana Grande to survey the area and further focus our design goals to best serve the community. We worked with an organization called the Solar Women of Totogalpa, a group comprised of local women in the area dedicated to the implementation of photovoltaic technology in their community. Under the guidance of an organization called GrupoFenix, they have created a center near the village where they use industrial reject solar cells shipped from the US to make solar panels for use locally.

Project Development We considered a number of factors in designing the final prototype. It was important that our design could be replicated in Sabana Grande under local conditions and with locally available materials. It was also important that the final product was cheap enough to be economically viable for the co-operative to manufacture and sell to the local residents. It was necessary to design the charger to cater specifically to the most common mobile phone models in the region and be durable enough to withstand considerable environmental wear and tear. Keeping these factors in mind, and through regular correspondence with our community partner in Nicaragua, we developed our final prototype.

Pedal Powered Butter Churn Tanzania, Summer 2011

Project Goals To design and develop a low cost bicycle powered butter churn for use by the Maasai Tribe

Background The Maasai are a pastoral tribe in rural Tanzania that live off the milk produced by their cattle. Tanzania has two main seasons – The wet season and the dry season. During the wet season, the cattle have enough water to drink and milk is plentiful. However, during the dry season, milk production suffers since the cattle do not get enough to eat or drink.

Problem Milk goes to waste during the wet season but the Maasai are often strapped for food during the dry season.

Sidhant Pai Department of Civil and Environmental Engineering

Project Development We considered a number of solutions before narrowing down on the butter churn (See Pugh chart). We hypothesized that the Maasai could sell the butter at the local market for more money than the corresponding amount of milk would earn them. This would provide a welcome source of secondary income which they could use to buy food during the dry season Different churn designs were considered before settling on the cycle attachment. Our design keeps the cycle chain and bearings separate from the churn itself thus ensuring that there is no contamination of the butter with dirt or grease. The milk is contained within two easily available plastic bottles and churn can be attached and detached within minutes. The material cost to build the attachment is less than $10 making it financially viable for the Maasai.

The above table is a Pugh Chart, a useful tool for comparing various qualities of different design possibilities with a simple +1 for improvement and -1 for the opposite. Here each design was evaluated against the baseline of the current Maasai practice of churning raw milk in recycled plastic bottles.

Testing in Tanzania Over the summer, my partner and I travelled to the Maasai village of Laiboni in Tanzania to test our prototype. We also worked with Global Cycle Solutions, our local community partner, to distribute our product.

Low Cost X-Ray Machine 2011-2012

Background The project revolved around researching and developing a low cost X-Ray device for use in developing countries. Medical institutions in these regions do not have access to the capital required to invest in high-cost commercial devices. If a low cost device can be prototyped, it will be of immediate use to medical staff in these regions.

Project Goals To design and develop a sub $500 dollar X-Ray machine using a 2X2A vacuum tube operated in ‘Cold Cathode’ mode. The design must stress portability and economic viability while ensuring the safety of both the operator and the patient. It is also important that the device be maintained locally using available materials and should thus be built accordingly

Sidhant Pai Department of Civil and Environmental Engineering

Project Development We started by focusing on low cost methods of stepping up 12V DC (from a commonly available car battery) to 50,000 V DC . The high voltage, when placed across a vacuum tube produces radiation in the X-ray spectrum. We considered a number of alternatives and decided to use a Cockcroft-Walton set up. Based on our research, we decided to use a 2X2A rectifying tube as our X-ray emitter. We also fashioned a simple lead shield to prevent the radiation from going astray and ran experiments to test for X-ray radiation.

Preliminary Testing Our test set up is shown on the left. We placed a 50kV DC voltage across the 2X2A tube and measured the radiation dosage in the output radiation. Our goal was to achieve X-ray radiation around 40keV. We focused the radiation by drilling a circular hole in the lead shielding and used Polaroid film to capture the X-ray radiation and produce X-ray images. Our testing indicated that we were close to our marks but our tube was often unreliable due to arcing issues.

Summer Testing Over the summer, I worked on increasing the output radiation energy and experimented with using different types of vacuum tubes. After that, most of the research focused on capturing X-ray images using scintillation screens and solving our arcing issues. I also housed the X-ray in a safer casing (as seen in the picture). Having solved the arcing issues, the entire set up cost around $350 and will produce reliable X-ray radiation in the range of 30 to 35 keV.