A section from a Ting Ting painting, by a Tanzanian artist, showing the use of a solar rope pump in the 'Solar village'

Back in the UK
I've now returned to Bristol to complete the final year of my masters degree in Mechanical Engineering. Comprehensive system specification and engineering drawings of the solar powered rope pump will be produced during the summer.

As mentioned in my last blog, from September the findings from my study will be used by a student from Mzuzu University in Malawi; who is yet to be selected.

The student will then be responsible for:
• Sourcing all the parts
• Constructing the pump
• Fully testing the system
• Adding any improvements as appropriate
• Carrying out a comprehensive comparative cost-benefit analysis of the pump and its competition.

The final design should then be ready for manufacture and installation by April 2010!

Plans for the future
This project has inspired me to formulate a clearer career path in a field that I was already committed to. I now plan to pursue the development and dissemination of the rope pump technology more generally.

Me back at Bristol

After graduation (and paying off some debt!) I plan to visit Nicaragua, where I will learn Spanish and hope to learn as much as I can from a Nicaraguan rope pump business, which has been providing 25% of the country's water over the last 15 years.

In the longer term, I hope to set up a rope pump business. Based in Africa, I imagine it's market would be NGOs, the government, private small-holdings, farmers and families. I hope the business model I employ would allow the business to be managed locally within a couple of years, helping to boost local economy.

With the help of good business and some investment, over the coming years the rope pump is set to help many thousands of people to lift themselves out of poverty in Malawi as well as across Africa.

Thank you for reading about the rope pump developments and for following the project!
Cai

A month was spent constructing, testing and demonstrating the solar-powered rope pump on a borehole at Mzuzu University.

Children help with testing the example rope pump, near Mzuzu University

It was agreed with Maxon, Head of the Teaching Centre for Renewable Energy Technologies Department (TCRET) at Mzuzu University and SolarAid's Milawi Trustee, that a student would take on the project as part of their fourth and final year at the University. The pump was then demonstrated to the whole year to unanimous interest!

The temporary pump installed at the University was intended to be a proof of concept and a demonstration for TCRET to gain support for future local development.

The brief test of the example pump drew 0.14 litres per second from a 15 metre depth and was powered by an 80watt PV panel, capable of running for 6 hours per day. The pump could therefore produce 3000 litres of water per day!

A large amount of further investigation is needed (especially in sourcing the motor) but a very provisional cost breakdown is: pump - $100, motor - $200, PV - $500, totalling $800. At this prices the pump at over double that of a small diesel pump but significantly less than any other comparable solar pump. However, if fuel prices over several years are considered, the solar rope pump looks to be highly competitive.

Please support our work in the development of the rope pump. Help SolarAid to reach thousands of people in Malawi and beyond, to have access to a resource we take so much for granted...water. Thank you.

More from me again soon,
Cai

Local children help me test the example solar powered rope pump, near Mzuzu University.

The solar powered rope pump project breaks down into three main phases...

Phase One- RESEARCH
The first three weeks were spent researching the appropriate balance between pump capacity and cost.

Firstly I visited Pump Aid, an NGO which has been successfully installing hand-powered rope pumps in Zimbabwe for 10 years and has recently moved into Malawi to continue its work. The visit provided invaluable information on manufacturing techniques.

I collected information on local water requirements from the Ministry of Water and Irrigation, the Water Resources Board, Water Aid's Malawi office, the Department for Agriculture and the University of Mzuzu. It was decided that a pump capable of delivering between 3000 and 10,000 litres of water a day would be the most appropriate balance between pump cost and capacity. This specification would also position the pump in the market gap between hand-operated and larger automated pumps powered by diesel or photovoltaic (PV) panels.

Phase Two- SOURCING MATERIALS
The next month was spent sourcing materials and assessing local resources, hardware suppliers, manufacturing capabilities and then shipping any parts not locally available. This is probably the period of the project that I personally learnt the most from; an invaluable experience giving me knowledge otherwise unobtainable and essential for any work in the field of development engineering.

The kids pictured above couldn't afford to go to school so they used to hang out with me while I was working on the pump. As you can see, they were intrigued by its capabilities!

I'll be summarising the final stage- testing- in my next blog posting soon.

Bye for now,
Cai

I'm now back in Bristol, where I'm carrying out more lab tests on the system. I will update you soon with more developments.

Please support our work by donating to this project. Thanks!

Until next time,
Cai

I have tried to assess the market, including the current demands and sources of water for the potential users. I have therefore toured the Land Management Department at the university, visited a couple of charities that install hand pumps around Mzuzu, The Agricultural Development Ministry, the Ministry for Irrigation and Water Development and the Rural Water Board.

So, after much consultation I believe the most appropriate solar pump would be one aimed at people looking for a step up from the hand pump, but who are unable or unwilling to pay the high running costs of the diesel and electric pumps on the market.

I have decided to test a range of configurations around a nominal system that would cost $700 and supply 8000 litres of water a day from a depth of 7m (the average well depth in Malawi). Although the initial capital cost is higher than existing diesel pumps (a comparable diesel pump costs around $300) there will be virtually no running costs for this solar pump and it would have a lifespan of around 15 years. When compared to a diesel pump producing the same amount of water, fuel and spares would require between $100-150 per year.

8000 litres a day is enough water for 80 inpatients at a hospital and would meet the domestic needs of about 250 people. It is also enough water for 120 cattle, or to irrigate enough land to feed one household of around six people.

65% of the cost of the solar pump goes on the solar panel, the cost of which drops every year, meaning that the pump will only become more competitive as fuel prices continue to rise.

I have also now ordered a motor and all the pump parts. Unfortunately that means that I have now reached the limit of the budget allocated to me by SolarAid and, ultimately, you!

It would be very useful to be able to try and test out different motors, for example the windscreen-wiper motor from a car. These motors are already mass produced and therefore will be considerably cheaper than the industrial motor I have bought in the UK. These other options are likely to be less efficient but I will only be able to find this out by testing them. I will only then be able to evaluate whether the money saved is worth it when compared to the increased size of solar panel needed.

Therefore, any donations made to the project now would potentially allow an even cheaper solar pump to be produced.

I have been very frugal with my budget so far and promise to make the most of any future donations.

Thank you,
Cai

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

Please support our work and donate to this project.

Thank you,

Cai

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

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.

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.

'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.

Remember that you can donate to this project by clicking on the 'Support This Project' button on the right.