Watch this video blog, made by Cai Williams, SolarAid's engineering volunteer. Cai has recently gone out to Malawi to research the use of solar powered water pumps.
I have been trying to prepare myself as best I can for Malawi, so I can hit the ground running.
I've been reading everything I can on solar power in Africa, national energy strategies, photovoltaic introduction and dissemination reports, assessments of private verses NGO implementation of water and sanitation in developing countries. I haven't even read the last few papers on the rope pump yet.
Based on this research, it seems my initial plan to attempt to persuade as many local manufacturers and suppliers as possible to add the solar pump to their product list as quickly as possible would be counter-productive. However, I still definitely plan to install the prototype solar pump on as many different depths of well as possible, so that I can confidently specify the system requirements for any system.
However the reports I've read, on the rope pump in particular, state that a new product (such as the solar rope pump) can too easily gain a bad reputation due to poor economic and/or quality control management. So, I plan to carry out a thorough lifetime cost analysis of the pump, and its competition. With this information we'll be able to confidently state exactly the period over which the solar pump becomes competitive. And along with careful quality-control of the solar pumps' manufacture we'll be able to successfully achieve the pump's very promising potential!
The next time you hear from me I'll be in Malawi (and I'll hopefully include some photos) where I can put all these theories to the test. I can't wait!!
Cai
I have now booked my flights to Malawi! I managed to save a couple of hundred quid by taking a 31 hour trip back, but this does mean that I get to spend a night in Addis Ababa (the capital of Ethiopia) which should be pretty interesting.
I have also now arranged to visit Pump Aid's operations in southern Malawi. They are a highly successful charity which have installed several thousand hand powered rope pumps for rural communities in Zimbabwe and are now expanding their operations into Malawi and Mozambique. They have a lot of invaluable experience not only in the technical aspects, but also in the very important sociological side of things, which is often the downfall of projects like this. I hope to learn as much as possible from them when I visit their workshop and the site of one of their installations when I first arrive in Malawi.
SolarAid's contacts at the University of Mzuzu's Department of Energy Studies (located in the north of Malawi) have agreed to host the prototype solar powered rope pump. This is great news, as I will be able to take advantage not only of their vast knowledge of solar energy, but also of their solar panels, wells and boreholes. This will save the project a huge amount of time and money. It will also allow a lot more configurations (of flow rates and pumping depths) to be tested, which in turn will increase the range of sites the solar pump will be able to comfortably cater for. All in all, it should be a very worthwhile trip!
Please support our work and donate to this project.
Thank you,
Cai
I thought I might talk about why the rope pump is such a uniquely appropriate design for use with a solar panel.
Firstly, I should point out that there is a theoretical limit imposed by the maximum depth a pure vacuum can suck water up from atmospheric pressure. In theory this limit is about 10 metres. However, in practice, the maximum depth water can be sucked from is more like 7-8 metres. This means that all pumps located at ground level are limited to drawing water from this depth.
Some designs locate the pump below ground level, connecting it to the power supply at ground level via a rotating shaft (or with electric cables) but this always adds complexity, and cost!
The rope pump's unique design means that the weight of the water column inside the pump's pipe is spread evenly across all the pistons, and the water is 'pushed' rather than 'sucked'. The pump can therefore draw water from a theoretically unlimited depth (in practice, water has been drawn from up to 90 metres!) whilst keeping the bulk of the mechanism above ground. The fact that the water's weight is spread across all the pistons also means that the pressure remains relatively low throughout.
Therefore, cheap PVC piping can be used as the rising main material- the pistons can even be cast by the user from melted plastic bags! Alternatively, the user can plat the rope from sisal (a native plant in many parts of Africa) and the pulley can be made from a recycled car tyre! This not only means that the pump mechanism can be made for just £20-30 but also that it is light enough to be removed by just one man (this is important as most pumps require specialist lifting equipment to remove them from the well). Combining this, with the simplicity of the design, means that the rope pump can be easily maintained by the user.
The rope pump is also unusual in its property of requiring the most 'torque' when it's only running normally, once the pipe is full. Torque is the measure of how much a force acting on an object causes that particular object to rotate by. This is unlike other pumps which have friction at start up, making them 'sticky'. This is important as most motors only produce their highest torque once up and running. The rope pump is also unique in being the only rotary hand pump. These two facts mean that the rope pump is particularly suited to being powered both by hand and by a motor.
Did you know that there are over 100,000 rope pumps are in operation worldwide? Most of these are hand powered! However, there is little to no data available for either the torque and power requirements of the pump or for the delivered flow-rates for a given head (or 'drawn depth') and rotational speed.
Over the last year, whilst at Bristol University, I've developed a theoretical flow model of the rope pump and tested it against a real model rope pump. I now am reasonably confident in predicting exactly what type and size of motor and solar panel I will need for a range of well depths.
SolarAid have been put me in touch with a very useful academic at the Department of Energy, at the University of Mzuzu in Malawi. His name is Maxon Chitawo. He has offered to let me use some of the facilities at the university which should be invaluable. I hope to set up a working solar rope pump on a range of well depths. I will record the methods and materials needed and collate enough concise information so that others will be able to install solar pumps on any well once I've left Malawi.
My other main aim while I am in Malawi is to establish a substantial number of suppliers of the solar rope pump by demonstrating its low cost, ease of maintenance, versatility and output flow rates. I believe that with a little more work the solar rope pump could be commercially supplied, especially to those who already have the solar panel or who have budget horizons of more than a couple of years. These might include schools, small businesses, hospitals and other community centres or groups.
Bobby Lambert received a lot of interest when he visited Tanzania last year, and I hope to follow up on these as well as find new potential suppliers.
I hope you've found it useful to read a little more about why the solar rope pump is such a simple yet highly effective invention, and how it works well with solar power. If you would like to support our work and help us with further research, please donate to this project!
Thank you,
Cai
I'm all ready to go to Malawi to test my prototype solar powered rope pump. The Institute of Mechanical Engineers has given me a small grant towards my travel expenses, while SolarAid will be providing the materials. Upon arrival, I will visit PumpAid, which specialises in rope pumps, to get their feedback on rope pump technology and how to integrate it with a solar system. SolarAid met with PumpAid 18 months ago when we first started developing this project. We're also in touch with WaterAid to find out about their experience of what works and what doesn't.
Once in Malawi, I'll have to find a test site. It looks like Mzuzu University, where one of SolarAid's local trustees is Senior Lecturer in Renewable Energy, will be able to help. I'll then build the solar powered rope pump next to a well and test it for pumping water. So if you'd like to support me in my endeavours - as we still need some funds for the cost of the materials - please do donate to this project.
Thank you!
Cai
This is Cai Williams, an Engineering student who is volunteering for SolarAid.
For the technically minded among you, here is the original concept paper written by engineer Bobby Lambert last year when we started thinking about this rope pump project:
Solar Pumping Concept paper.doc
Bobby is a Chartered Engineer with 25 years professional experience. He has 12 years practical experience in rural development in Africa, including eight years of academic and field based research, mainly in Zimbabwe in the late 1980s. He served as Chief Executive of RedR-Engineers for Disaster Relief until August 2006. He's our expert advisor on this project.
This is very interesting. We just came across an academic article in the Journal of Water and Health that confirms our view that the rope-pump model is a great one. Read the following summary:
'The conventional handpump is the most popular technology choice for improved potable water supplies in rural sub-Saharan Africa. To date, however, it has failed to deliver satisfactory levels of sustainability, largely due to inadequate maintenance capacity. An alternative option to standardised imported handpumps is the locally manufactured rope-pump, which is considerably cheaper and easier to maintain but has been rejected in the past due to fears of impaired water quality.
'The findings of the study indicated that the rope-pump out-performed the conventional handpump on the majority of counts and that, contrary to widespread perceptions, there was no significant difference between pump types with respect to the impact on microbiological water quality. Consequently, the rope-pump provides a significant technological opportunity to improve water supply sustainability in Africa.'
This extract was taken from the 'The case for the rope-pump in Africa : A comparative performance analysis', Journal of Water and Health, 2006, vol. 4, no4, pp. 499-510, by Harvey and Drouin, published by IWA Publishing, London.
If you'd like to see how a manual rope pump works, watch this:
Remember that you can donate to this project by clicking on the 'Support This Project' button on the right.
Good news! My bursary application for my personal expenses from the Institute of Mechanical Engineers and Bristol's Knowlson Trust has been successful. The student development engineering charity Engineers Without Borders (EWB) have asked for further details regarding my bursary application with them, but my chances look promising.
The World Water Day in Trafalgar Square was very interesting. The rope pump proved to be very popular with passing families, despite the apocalyptic weather! The guys from Zimbabwe made it along too, and seemed impressed with the pump Ben and I had built. They invited me to visit their workshop in southern Malawi this summer, which should be a very valuable experience.
I also recently met a graduate of Bristol University at an EWB research conference who will be spending 6 months this year in South Africa on a project, working at introducing the rope pump over there. It looks like we will be able to share a lot of useful information and experiences.
Cai
We've just received a video from Guente Nueva, our partner organisation in Argentina with whom we are also developing a solar powered rope pump. The video is in Spanish, but still worth watching even if you don't speak Spanish. It explains their hand-powered rope pump project, which will be used as the basis for developing a solar powered one:
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