1. SURFACE TENSION DRIVEN WATER PUMPING by J. Fraser & R.T. Dobson University of Stellenbosch Energy Postgraduate Conference 2013

2. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Overview Introduction Background and Objectives Main Theory Problems Why it works Conclusion Falling water droplet

3. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Introduction Nature has adapted of millions of years Humans can learn much from nature Biomimicry = nature inspired design Examples: –Elephant trunk –Gecko feet –Shark skin –Lotus leaves –Beehive structure –Insect Nano robots –And many more

4. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Introduction (cont.) Surface tension: similar to elastic membrane on fluid surface Nature found myriad of exploitations: –Small insects stride on water –Bacteria releases surfactant for driving force –Some larva employs vector control for propulsion Recent applications: –Small object propulsion –Nano-robots maneuverability –Capillary action –Micro pumping –etc Plant life thrived on Earth for thousands of years Pump water seemingly effortlessly Giant Redwoods grow up to 100 m tall Useful mechanism for water pumping In a time of water shortages, climate change, power consumption and emmision concerns

5. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Background & Objectives Plant Leaves: –Photosynthesis: water + carbon dioxide + energy  carbohydrates +oxygen Ingenious water transport mechanism of plants Capillary-driven heat pipe technology mechanisms Construct mechanical/artificial pump First step in a larger project: –wherein hydrogen, food (carbohydrates) and fuel are artificially produced. For this project: –build mechanically-constructed experimental simulation working model of transport mechanism –Theoretical thermal-hydraulic simulation model + validation against experimental model. After validation use of such a water pump in an artificial photosynthesis program to be established.

6. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Main Theory Overview Water Transport in trees  Transpiration pull (TACT) –Transpiration –Adhesion –Cohesion –Tension

7. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Problems

8. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Why it works

9. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Why it works Secret  Strong adhesion forces  Strong cohesion forces  Evaporation  Surface tension forces Must prevent nucleation sites –Prevent embolisms Require a continuous channel of water: –Rerouting –Dissolve bubbles

10. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 In Conclusion Nature offers many lessons and techniques Surface tension useful mechanism Tree water pumping mechanism investigation Theory, build, experiment & validate

11. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 Acknowledgements Mr. Dobson Family

12. iThemba LABS SAHPA ® South African Heat Pipe Association Energy Postgraduate Conference EPC2013, 11-14 Aug 2013 END THANK YOU