Cai and Ben, from Bristol, have been working on the concept of integrating a well pump with a solar power installation, as an economically viable method of improving access to water for drinking and irrigation in areas with poor infrastructure. The rope pump was selected as the most appropriate design for integration with a solar panel based on cost, maintenance requirements, efficiencies, achievable heads and flow rates. To assess the power demands of the pump a theoretical model was developed and compared to a physical model based on those supplied by the charity PumpAid.

The theoretical model was backed emperically for the configurations where the slip flow remained laminar. Analysis of the empirical data proved that the frictional shear forces of the slip flow were negligible. The mechanical power and discharge rates of the rope pump were extrapolated up to the full 10m head desired and found to be approximately 140W and 0.611l for a 40mm OD rising main. The 40mm rising main was found to have an efficiency over 3 times that of the 21mm OD rising main. Considerable scope for improvements to the rope-pump efficiency was also apparent. The cost of the addition of pump and motor (if purchased in a batch of over 100) to an existing solar installation was found to be £100, the additon of a solar panel was found to add a considerable £1200.

Read their summary presentation, view Cai's full report on the mechanical part of the project and a summary of Ben's work on the electrical engineering. Cai is going to continue with this project next year as part of his university studies.