The news wires were abuzz recently after the BBC ran a story about four Nigerian school girls who had invented a urine-driven generator.
By Brian Bakker
This intriguing story originated from Maker Faire Africa 2012, which was held in Lagos, Nigeria. Four teenagers – Duro-Aina Adebola (14), Akindele Abiola (14), Faleke Oluwatoyin (14) and Bello Eniola (15) – from Doregos Private Academy in Ipaja, located in the Nigerian city of Lagos, accomplished this amazing feat. Apparently the unique invention can provide up to six hours of electricity with just one litre of urine.
The way it works is as follows:
• Urine is put into an electrolytic cell, which separates out the hydrogen.
• The hydrogen goes into a water filter for purification and is then pushed into the gas cylinder.
• The gas cylinder pushes hydrogen into a cylinder of liquid borax, which removes any moisture that may remain.
• The now purified hydrogen gas is pushed into the generator.
But this description raises some questions – particularly for technically inclined readers. For example: an electrolytic cell requires electricity to separate hydrogen from the urine. The girls’ project supervisor, Lawal Olaide, was kind enough to answer this question when approached via e-mail.
“Initially, at the onset of the project, the urine electrolytic cell is powered using an external battery (for about two minutes). This is to generate enough hydrogen-oxygen mixture in the storage tank. Once this is done, the hydrogen runs the generator, which in turn powers the cell,” explains Olaide.
However, the project supervisor notes that the design has since been refined to include a bridge storage tank which stores some of the hydrogen-oxygen mixture whenever the generator is switched off. This stored hydrogen can be used to start the generator, which then powers the electrolytic cell, eliminating the need for a battery and making the device self-powering.
Another key aspect of the system is the use of urine: why? The raw material required to drive the generator is hydrogen, which is found in water (H2O). According to Olaide, urine is preferable to ordinary water or salt solution (brine) because urine is 95% constituted of water.
“Furthermore, unlike water, urea has four hydrogen atoms per molecule and these atoms are less tightly bonded than hydrogen atoms found in water molecules. To break the molecule down, a voltage of 0.37V needs to be applied across the cell – much less than the 1.23V needed to split water,” notes Olaide.
“12 volts is required to initially start the urine electrolytic cell to produce the hydrogen-oxygen mixture. The DC port of the generator is connected to the electrolytic cell, which ensures continuous charging of the cell. The required power for the urine electrolytic cell is approximately 100 watts while the hydrogen-oxygen mixture it produces powers a 1.9 kVA generator.
“A similar result is not obtainable if water is used as the electrolyte as we will require more energy input. [And] brine (salt water) will give off dangerous gases such as chlorine and can also be damaging to the surface of the electric plates, resulting in uneven voltage output,” concludes Olaide.