Segway Inventor’s Innovative Cow Dung Powered Water Purifier

An estimated 900 million people worldwide do not have access to clean drinking water, causing 3.5 million deaths annually. Dean Kamen, the ingenious inventor of the Segway, Autosyringe, DEKA Arm, Ibot and many other innovative creations, has introduced a self-powered water purification system he calls, The Slingshot. This water vapor distillation system was invented to address the key public health issue of lack of access to clean water, especially in remote, developing areas of the world. And now with a multi-million dollar partnership with Coca-Cola, he may be on his way to putting a big dent in this huge problem.

Dean Kamen, Inventor of the Segway. Can his Slingshot provide the developing world with clean and fresh drinking water?

What is the Slingshot?

The Slingshot device is powered by a Stirling engine running on combustible fuel, and can produce clean drinking water from any source. In an initial demonstration, Kamen used the device to distill his own urine, which he then drank. A vapor compression distiller which can produce 250 gallons of fresh water a day purifies the water. The Slingshot can purify water from polluted rivers and lakes, ocean salt water, and even raw sewage.

How Does a Stirling Engine Work?

The Stirling engine which powers the Slingshot is a heat engine that uses cyclic compression of air or another gas to convert heat energy into mechanical work, which can then be converted to electrical energy. The engine can be constructed from two cylinders, one hot and one cold, with chambers physically connected by an internal heat exchanger called a regenerator, allowing the two chambers to share the same air. Alternately, the engine can be constructed from a single cylinder which is hot at one end and cold at the other, containing a loose-fitting shunter that acts as the regenerator by forcing the air to circulate as the piston moves.

The Stirling engine is similar to a steam engine, but notably more efficient and able to run on almost any heat source. The hot cylinder is warmed by the heat source while the cold cylinder is cooled by a heat sink, and the thermal energy is transferred from one to the other by the shared compressed air while the piston produces mechanical energy from the cycling movement. This closed system allows for highly efficient use of the heat energy(fuel) with very little CO2 emission or wasted energy.

Dean Kamen with his Slingshop prototype on the right and his Coca-Cola backed production model on the left.

Powered by what?

The Stirling engine makes alternative energy sources more viable because of its efficiency. While the heat source powering a Stirling engine does not need to be a combustible fuel, any form of fuel will work, including methane from cow dung, which is exactly what Kamen is proposing for villages in remote regions of the world. Their Slingshot systems would be powered entirely by fuel created by decomposing cow dung.  This would provide them with sustainable, clean and fresh drinking water, which they could purify with their own locally generated power, from the waste of their herd animals. Additionally, the unit could be powered by Solar panels, in areas where they are available and economical.

What is Vapor Compression Distillation?

Vapor compression distillation uses a jet of compressed hot air to evaporate the water source. The compression of the air causes the water to condense at a higher temperature than uncompressed air, which allows this distillation process to collect the water without having to cool the air as much as usual. The hot air retains more energy which can be used to vaporize more water, making the system more efficient than regular distillation.The Slingshot device uses the hot air exchange of the Stirling engine to vaporize and condense pure water with high efficiency and with any available source of heat.

While the Slingshot remains costly, full-scale production and support from the Coca-Cola partnership aims to drive the cost down to about two thousand dollars per unit. The lower-cost device is intended to allow impoverished communities to invest in an efficient, reliable source of clean water to dramatically improve their quality of life and prevent millions of deaths each year.

What do you think about Dean Kamen’s Slingshot initiative?  Will it make a difference?