December 2000






This issue of our SWESS newsletter is again the last one in a row of four financed by the Dutch Minister. What will come after this is not clear yet, but we will be in touch!

We hope the newsletter could give you a vivid idea of the developments of small-scale wind systems around the world. Still, we perceive a huge gap between the complex and expensive equipment offered by industrialised-world manufacturers, and local efforts focussing on effective, low-cost solutions. Designers and manufacturers in the South continue to be hampered by scarce resources and limited production skills. While at the consumer side, the initial investment is too high a barrier.


End-user surveys on water pumping technologies in India, Sri Lanka, Colombia and Kenya, have pointed out that windpumps are generally far cheaper than any other pumping alternative, PV in particular. A large and comprehensive support for windpump implementation, including marketing, distribution, access to credit facilities and ongoing product development, would be a key factor to change the picture. A regional or global “windpumping network” could provide effective support on all these subjects, assisting local manufacturers, customers and bank lenders. Of course, the large industries behind photovoltaics since long have proven their capabilities to tackle market issues.


Notwithstanding, professional manufacturers of small windmills (with a focus on the developing world) do exist. Kijito in Kenya, Jober in the Philippines, Poldaw in the UK, Aureka in India, to mention just some of them. In this issue, we can report good news regarding Zimbabwe, both from Zero/Manx and from Poldaw. The rope windpump proves to be an attractive research subject worldwide and progress will inevitably come.


Support from donor organisations will remain necessary to link local efforts and help people to learn from each other. There should be no reason for a manufacturer in a developing country to start fully from scratch, if he can learn from his peers elsewhere “in the field”. At Arrakis, we keep our Website open as a platform for the exchange of experiences and knowledge. Please post your messages!


But to enable a sustained product development and address the marketing and investments issue, more is needed. Manufacturers, rural development agencies and small farmers by themselves cannot generate the momentum required for a progressive implementation of windpumps and small wind-electric systems. Regional co-ordination and the input of external financial resources are indispensable. We therefore make here a strong plea for a long-term programme by an interested donor organisation.


Jan de Jongh

Remi Rijs






The Nicaraguan rope wind pump has been extensively described in previous issues of SSWES. Apart from being an interesting, low-cost option for water pumping for both cattle farmers and small farmers, it has been pointed out that the restricted rotational freedom of the windmill head limits its application potential. A first improvement has been implemented in 1995 by Henk Holtslag, in which both sides of the rope are brought as close as possible to the tower axis by means of a pulley. This model allows a pivoting freedom of 360º, but the rope can get tangled after several turns of the head.


We received progress on this issue from two groups, a university work from England / Colombia, the other from the Nicaraguan producer.


University work in England and Colombia:

“The main problem with the present design lies in the transmission between the turbine and the rope pump. The pulley attached to the rotor is connected to the fixed pulley driving the pump. The head is free to pivot around the tower, but its angular course cannot exceed 250º. When the wind direction changes, the transmission rope becomes tightened and twisted.


An improved system should enable the windmill head to rotate without restrictions around the vertical axis. An option would be to use bevel gears between the rotor shaft and an extra, vertical shaft running down the tower along the axis of rotation of the head. A second pair of gears could then be used to drive the pump pulley. Such a system however, would require facilities and precision manufacturing that are rarely available in a local windpump workshop.


More Solutions


Another solution needed to be found. Inspiration from similar cinematic problems proved little fruitful, so a new line of thinking had to be followed: an additional, double-pulley was mounted, turning around the axis of the turbine head. The driving power is now transmitted in two stages: 1) the wind rotor shaft driving the upper pulley by means of a polythene rope loop; 2) the lower pulley (fixed to the upper one), driving the pump pulley through a second rope. The figure shows the functioning of this principle.



The lower pulley driving the Pump Outlay through a second rope: Rope Wind Pump.



Schematic diagram


The system was built and implemented in an existing test wind pump at the "Universidad Tecnológica de Los Llanos" in Villavicencio, Colombia. Two assistants helped manufacturing the modified assembly in a small workshop where basic facilities were available. The structures added mainly consisted in four arms, each with a small pulley at the end. Two were welded to the windmill head, the other two to the upper part of the tower. The pulleys were mounted on slightly inclined tubes that were adjusted to length, bent to bring the pulleys into exact alignment, and welded in place.


The vertical double-pulley needed to be inserted between the head and the tower, while rotating freely from each of them. The upper wooden yawing bearing appeared to be the most suited element for mounting this double-pulley. Due to the size of the wooden piece, a large ball bearing would result much too bulky and expensive for this purpose. Therefore, a set of three standard roller skate wheels (with ball bearings) was mounted on a three-spoked, aluminium wheel. While the inner bearing cylinders were bolted to the double pulley, the soft plastic skate rollers would run smoothly on the cylindrical, vertical wooden yawing bearing. This idea, adapted from C.E. Oram, proved cheap and effective. Also, the size of the bearings is not very important, as long as all three are identical.


The modified drive train was tested in Villavicencio and found to perform as expected. The use of the local workshop proves that this modification can be implemented using basic means and therefore appears as a feasible solution for developing countries.


One observation was important: with the new drive system: the pump pulley is now turning in the opposite direction compared to the original situation. “



- Jean-Sébastien Chevassu:

- Mauricio Gnecco:

- Arthur Williams,

Dept. Electrical & Electronic Engineering,

Nottingham Trent University,

Burton Street, Nottingham, NG1 4BU,

United Kingdom

Tel.: +44-115-848 2313

Fax: +44-115-848 6567



Ongoing work in Nicaragua:

“A new transmission for the rope windpump was designed by the Nicaraguan organisation CESADE, with technical support from the Dutch organisation DOG. Again, the transmission should be low-cost, and easy to produce and maintain. After two years of testing several angular transmissions, a “three-pulley transmission” was installed in a windpump for field trials by the end of 2000. The new design incorporates an angular transmission while retaining the eccentric rotor mounting, essential for the hinged vane mechanism to guarantee adequate furling behaviour. If this new transmission proves successful, the cost of the model will raise with about US$ 60-100,-.”



Henk Holtslag





The “Three-pulley transmission”.




The Poldaw range of windpumps started in 1991 with the design of the Poldaw 3.5-m model. This development made use of all available information and experience from traditional and modern windpump designs. The design objective was to produce a machine which was low cost, but without compromising anything on strength and reliability. Commercial manufacture started in 1994 in Zimbabwe and UK and is entirely local. Since then, manufacturers in Pakistan, Nigeria, India, Ethiopia, and Turkey have started making Poldaw windpumps.



The small wind pump developed by Poldaw for Bolivia.


In 1996 a 5-m windpump was developed, which has twice the output of the 3.5-m model at cost increase of only 50 to 75%. This model went into production in 1998 and is now manufactured in several of the countries.


Our manufacturers in Zimbabwe, Pakistan, and UK are doing particularly well, with more than 100 units now running overall.


In Pakistan they are installing windpumps on the Baluchistan drought alleviation government project. The first phase is 25 windpumps, and phase 2 will include approx. 250 windpumps.  These windpumps supply water to remote villages, where the existing diesel, wind and hand pumps are largely out of action, and the villagers have been drawing water by the traditional bucket and rope method.


In Zimbabwe, the machines are now largely being sold for small-scale irrigation for vegetables, and units are also being exported to Zambia for the same type of use.


In the UK, there are a surprisingly large number of situations where the use of a windpump is actually cheaper than an electric pump, largely because of the cost of installing electricity cables over distances of a kilometer or more.  Therefore, although the Poldaw range was principally aimed at the needs of developing countries, it is also being sold in the UK. 


The Indian collaborator has unfortunately given up making the Poldaw windpumps. Since it has no gears in the mechanism, it is not eligible for the full Government subsidy scheme. Hopefully the situation will change in due course when an effective “level playing field” is created.



The Poldaw Wind Pumps help in small-scale irrigation of vegetable farming in Zimbabwe.



Responding to the Market Needs


This year we were approached by a charitable organisation in Bolivia who required a very small windpump. The wind regime there is extremely good, and we have designed for them a 1.8-m rotor windpump which can sell commercially for under US$ 500.  A number of these units are undergoing trials, and when they have been sufficiently tested to assure us of adequate reliability, the design will be released for commercial manufacture, sometime in 2002.


We are always keen to encourage new manufacturers to start producing the Poldaw windpumps. The Poldaw website is a useful information source for potential manufacturers and users and describes the machines in more detail.


(Sandy Polak, Poldaw Designs, a division of:

Neale Consulting Engineers Ltd   

Highfield, Pilcot Hill, Dogmersfield, Hants RG27 8SX,  

United Kingdom

Tel: +44   1252 629199

Fax: +44   1252 815625


Website: )






The ZERO network of environmental experts in Harare, Zimbabwe together with Manx Wind Energy Services, UK, developed a 500 W wind battery charger to be operated cost-effectively in the low-windspeed conditions characteristic of sub-saharan Africa. The project was funded by the local Dutch Embassy in Harare.


The principal objective was to demonstrate that such a machine could be manufactured in-country, and a maximum local manufacturing content was pursued as a design criterion.


Designing the Charger


Based on local wind data, a 3.6-m diameter fixed pitch rotor was chosen. This was directly coupled to a locally produced PM alternator. The three turbine blades were handmade using an indigenous wood. An 18 metre guyed tubular tower, with gin pole and pulleys for on-site winching completes the system.


The turbine design aimed at an output of 50 kWh/month in a monthly windspeed of 4 m/s, which is common in sub-saharan Africa. A hinged tail vane mechanism was chosen to protect against gusts. For a description see


Growth Opportunities


As part of the project, wind potential measurements were carried out at four sites around Harare, using Wind Prospector dataloggers.  The programme shows that mean wind speeds are generally in the range 2 - 4 m/s. The results from the test programme, carried out between July and November 1999, show an average monthly energy production of 106 kWh, 134 W mean. This output is the equivalent of nineteen 50-W PV-panels at that site at an equivalent cost of only 20% of the PV alternative.


The turbine is being manufactured in Harare by African Windpower (Pvt) and main exports have been within the SADC region, but its has also been exported to Europe and the USA. The project has demonstrated the potential for linking specialist external design expertise with local industrial capacity. The outcome is a locally-manufactured product for both the domestic and export markets, capable of competing in one of the fastest growing sectors of the renewable energy industry.


( Source: Renewable Energy 16 (1999), p. 934-939, Pergamon Press, Elsevier Science Ltd.; Contact: Dr. Geoff Watson,






The SWHPTC (Small Wind and Hybrid Power Test Centre) at Mithapur, Gujarat, has been set up by TERI with financial assistance from the MNES (Ministry of Non-conventional Energy Sources). The SWHPTC aims at providing testing and certification, product development, performance monitoring and training services. The SWHPTC covers five acres of land at Mithapur on the west coast of India, 10 km south of the port of Okha. The land is ideal for testing wind turbines as it is very flat and has no obstacles to the wind flow in the vicinity.


A site building provides 80 m2 of covered space for instrumentation, a small workshop, diesel genset, battery bank and office space. A 25-m high wind mast is used for monitoring wind speeds and directions at three levels. The NRG-9300 datalogger, used for monitoring the wind data, also records atmospheric pressure, ambient temperature and several electrical parameters.


Future Plans


The SWHPTC plans to take up the following programmes in the coming years:

- Testing and certification of: wind battery chargers; wind pumping systems; hybrid power systems.

- Research and development on: desalination systems based on renewable energy: ice-making for fishing villages; wind pumps for special applications (aquaculture, salt pans).

- Prototype development, field testing and commercialisation of: wind-solar hybrids for home lighting; wind-solar-diesel hybrids for village electrification; wind-diesel hybrids for island diesel grids.

- Training programmes on: design and manufacture; installation, operation and maintenance; monitoring and performance evaluation.


Currently a mechanical wind pump system and a several hybrid systems are being tested and monitored.


(More information is available from:

K. Raghavan, Consultant Hybrid Systems TERI, Darbanri Seth Block, Habitat Place, Lodhi Road, New Delhi - 110 003

Tel: +91 (11) 468 2100/11, Fax:  +91 (11) 468 2144/45, Email:

Website: )






"Small Scale Wind Energy Systems" is a half-yearly newsletter co-edited and published in English by GEDA (India) and in Spanish by ITDG (Peru). The English edition is included in GEDA´s magazine “FIRKI”; the Spanish version appears as a section of ITDG´s “HIDRORED”. It is financially supported by the Ministry of Foreign Affairs of the Netherlands (NEDA-DML/KM).


Co-ordination and editing: Arrakis, Wilhelminastraat 26, 5141 HK  Waalwijk, The Netherlands; phone: +31(40)281 9454; fax: +31(40)281 9602; email:; Website:


Citation is encouraged on the condition that the source is indicated. For subscription, articles or reactions please contact the editors.