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Technology and implementation issues related to water-pumping windmills
Letters
Technology and implementation issues related to water-pumping windmills
paper picks up on these issues as they relate to the introduction of windpumps for new markets, and also draws upon the contributions made at an international seminar held at Silsoe College, Bedfordshire, UK, July, 1994 [I.T. Power, 1994].
N.W.M. Bishop
2. A review of water-pumping windmill technology developments
Random Loading and Design Group, Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom J.D. Burton Dept. Ing. Mecánica, La Universidad de Los Andes, Apartado aereo 4976, Santa Mé de Bogotá, Colombia 1. Introduction The UNDP Global Windpump Evaluation Programme [UNDP, 1988] undertaken by the World Bank in 1987-88 estimated a potential market for 500,000 low-cost windpumps worldwide. In fact water-pumping windmills are already in use in developing countries and are important to local communities. For instance, windpumps are used for human drinking water supply, livestock maintenance and crop irrigation. With this in mind, substantial research and development projects aimed at providing low-cost windpumps have been undertaken, particularly in the UK for the Overseas Development Administration and in the Netherlands for the Dutch government. However, successful projects focused on implementation of the technology are very rare. Certainly, realisation of even a fraction of the potential which exists has not occurred, and so the question that needs to be asked is: why? Probably the most important factor is that many of the so-called ‘‘soft’’ technology problems were not addressed. Unfortunately most of the new technology development with windpumps was undertaken by universities and research organisations, who predictably focused on technological innovation. Some of the ‘‘soft’’ problems in Padgett’s [1995] list were for the most part overlooked. Padgett identified a number of wider aspects to be taken into account when transferring technology from the ‘‘West’’ to small developing country manufacturers. These included: intellectual property; financial resources; manufacturing and marketing capability; design and development; test facilities; business and technical consultancy requirements; and quality control. At the present time the British ODA has an ongoing programme to look at the obstacles to, and opportunities for, marketing of windpumps in some 22 developing countries [Hacker and Munro, 1995]. Other than this, at the present time, new activities aimed at implementing water-pumping windmill technology are almost non-existent. At a recent British Wind Energy Association-sponsored workshop a paper was presented [Smulders, 1995], ‘‘Wind water pumping – the forgotten option’’, that correctly sums up the present situation and examines some of the reasons for lack of widespread activity. This present
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The majority of people, when asked about windpumps, would envisage the so-called ‘‘American’’ style of machine which was developed in the USA during the 19th century. This technology has gained widespread acceptance throughout the world with many hundreds of thousands being installed. It is a relatively expensive piece of equipment, in part because it has a gearbox to reduce the speed of the pump, and is generally not suitable for local production because of its complex construction. A cost running into several thousands of dollars would not be untypical. It has, however, gained a very good reputation for reliability. This kind of technology has therefore addressed the needs of a particular market where cost is less important, such as for large ranches where the windpump needs to operate unattended for long periods with a minimum of human intervention. The technology is unusual in that it has remained largely unchanged for over one hundred years. Established manufacturers exist in Australia (e.g., the Southern Cross or Yellowtail machines), South Africa (e.g., the Climax machine), the USA (e.g., Aermotor, Dempster or Fiasa machines) and Argentina (e.g., Fiasa). Figure 1 depicts a typical American type of machine. From this technology the so-called second generation windpumps have been developed (see Figure 2). Most of these machines have appeared over the last 20 years, e.g., ITDG (UK), Gaviotas and Jober (Colombia), CAAMS (China), CWD (Netherlands), BHEL (Kenya) and Oasis (France), and were developed with local production in mind. The three main requirements of such machines are that they must be cheap to buy or make, efficient in terms of output, and structurally reliable. As a consequence of the economic situation in most developing countries the first requirement usually means that the windmill must be made using local materials and labour, and this is why local manufacturability is so important. The use of standard materials, e.g., angle iron, ball-bearings, pipes, steel plates, etc., and the absence of more complex manufacturing details such as castings are important. Gearboxes are also usually not employed. In some cases the rotor has fewer blades in order to save on material costs, and so rotates faster. The second generation machines have focused on a different market for water pumps where there is an important local need for water but where initial capital is limited. This includes, for instance, provision of drinking water to rural areas and irrigation. In this case local manufacturability becomes the overriding issue because of the importance of cost mentioned above and because of the lack of foreign capital.
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3. Recent solutions to engineering problems With the introduction of these new second generation windpumps there have come a wide variety of reliability problems. Perhaps it was because the American type of machine was so reliable that too little effort focused on this issue. However, the behaviour of the two kinds of machines is fundamentally different. The American type of machine was developed through trial and error over a long period of time. Furthermore, because of its relatively slow-running rotor and the presence of a gearbox, the response of the machine can be accurately characterised using static design principles. In contrast, modern or second generation windpumps usually comprise a direct drive (no gearbox), are lightweight (for reduced cost) and relatively fast-running (because of the small rotor size or because of fewer rotor blades). Sometimes the rotor is made deliberately large [Polak and Dawson, 1995] so as to slow the rotor down to speeds that the direct-coupled single-acting pump can handle. For the faster-running machines, and probably also for the not so fast machines, there is a strong interaction between the dynamic behaviour of the ‘‘topside’’ tower and rotor system and the ‘‘bottomside’’ pump system. It is therefore essential that any design nowadays is founded on sound dynamic analysis principles. This is perhaps where much of the recent work on second generation machines has been lacking. Many of these second generation machines have no softness built into the design. A simple analogy is to drive a car down a bumpy road after removing the shock absorbers and springs [Bishop, 1991]. A good parallel to make is the contrast between a 19th century stone arch bridge and a modern aircraft. Stone arch bridges like the traditional American windpump were developed over a long period of time through trial and error. Aircraft design like modern windpump design requires an analysis approach founded on sophisticated dynamics and reliability tools. Dynamic loads which originate in the pump system can, at least in part, be dealt with using improvements and modifications to the pump and fluid system. It might be thought that after centuries of use, the lift-pump, together with its dynamics, was well understood. This is not the case. Most hand-pump arrangements are driven at speeds where dynamic behaviour hardly matters, and even the traditional American fan mill has gear reduction to slow the pump down. Only in recent times, when there has been a move towards either electric motor drive (from solar panels), or direct coupling to small diameter mills, has the pump moved sufficiently fast for dynamic behaviour to become important. Both riser pipe flow transients, together with distributed hydraulic impedance, and lift rod loads, together with attendant elasticity, have to be taken into account at these higher speeds [Burton and Davies, 1996]. The valve sequencing with the lift-pump, and how it is controlled, is vital. Hydraulic load is carried on the bottom valve and riser pipe on the down stroke and on the piston valve and lift rod on the upstroke. How the load is switched from one to the other at the end of each stroke Energy for Sustainable Development
Figure 1. A typical ‘‘American’’ type of water pumping windmill.
becomes, at higher speed, a problem requiring careful consideration if an adequate level of reliability is to be achieved. Tools are available today to both understand and engineer these pumps properly. Industrially, high-speed reciprocating pumps run at eight or ten times the speed of lift-pumps, and have involved modern dynamic techniques in their design. Unfortunately, many windpump manufacturers exercise little control over the size of the pump, and even more importantly, the size of the riser pipe attached to their mill. The riser pipe is often restricted in the interests of economy but can easily cause very high dynamic loads on the lift rod. Structural vibrations, component vibrations and shock forces in the pump rod can be analysed by looking at the topside dynamics of the system. Various aspects of structural behaviour can be included under this heading, such as ‘‘pump rod shock forces’’, ‘‘component vibrations and response’’ and ‘‘global structural vibration and response’’. Although ‘‘pump rod shock forces’’ can be envisaged as originating in the pump fluid system, they also affect the topside of the windmill. They can cause both failure of the pump rod itself and failure of the tower and its components. Vibration of the tower, vanes, rotor blades, etc. can be described under the heading ‘‘component vibrations and response’’. Once individual components, such as the tower, start to vibrate, the movement itself can then form an additional load for other components. An understanding of such dynamic interaction between structural elements is vital if structural reliability is to be assured and this can be included under the heading ‘‘global structural vibration and response’’. In order to obtain a complete design methodology it is important that a thorough understanding of the above types of structural behaviour !
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College London and the University of Reading. The main findings would indicate the need to decouple the peak transient loads between topside and bottomside. In order to verify the theoretical work a test site has been set up at Silsoe College, Bedfordshire, in the UK. Three test beds are available, two with boreholes (at 25m and 43m respectively) and one with a surface tank. The location of the site is reasonable for testing, being of undulating hills with a mean wind speed of 5.0 m/s. A monitoring station on the site is capable of storing both performance data (output, wind speed, direction, etc.) and structural responses (rotor speed, yaw position, tower and blade stresses, etc.). A computer-based system is used to acquire, analyse and store the results. Currently three machines are being tested, these being the CWD2000, CWD2740 and Gaviotas direct-drive machines. It is hoped that the site can become an established location for wind-pumping test work. It is clear from the above that although many of the hard engineering issues have been solved, or are currently being addressed, the question that remains is, how to utilise these solutions, and this is where the issues of technology transfer and market development need to be addressed. 4. Lessons to be learnt from the past
Figure 2. A typical 2nd generation machine, the Gaviotas machine.
is obtained. The cyclic behaviour of the lift pump can interact with the rest of the system through either the drive input (the lift rod) or through the riser pipe flow transients at discharge. Rod loads may be modified by adjusting the elasticity in the windmill tower (topside dynamics), at the point of support of the riser, or in the rod itself (bottomside dynamics). Flow transients may be modified by either altering the discharge (riser pipe) impedance or by the incorporation of elastic elements into the pumping chamber. A recently completed project shared between the Technical University, Eindhoven, Los Andes University in Colombia, and the University of Reading [Smulders et al., 1994] has focused particularly upon this latter approach. The dynamic safety system used to keep the rotor pointing into the wind (and to point it out of the wind at high wind speeds) has a significant effect on the loads present in the tower because of gyroscopic and shock forces caused by overspeeding (topside dynamics) and in the pump rod and pump system (bottomside dynamics) because of the resulting pumping speed variation. It is therefore obvious that an understanding of both topside and bottomside dynamics, as well as the interaction between the two, is an essential prerequisite to a reliable structural system. Both ‘‘topside’’ and ‘‘bottomside’’ dynamic interaction have been the subject of a recently completed UK-funded project (June 1993-December 1995) between University 46
Energy for Sustainable Development
Much effort and many person-years have been expended over the last 20 years developing modern or second generation windpump machines and yet successes in the field are rare. It is worth considering what might be the dominant factors behind these failures in order to see what lessons can be learnt for the future. First of all, much of the effort has been uncoordinated. Two of the largest European programmes of work, the CWD programme (1976-1991) and the ITDG-IT Power work (1976 onwards) have been undertaken almost completely separately. Furthermore, because many programmes of work have been undertaken using developing country projects it has been very difficult to transfer results between different programmes. The Dutch-UNDP support for the Colombian Gaviotas project in the late 1970s and early 1980s which resulted in the production of some 8000 mills is a case in point. As a result of this lack of coordination many different programmes of work have been undertaken in parallel with much replication of effort. Secondly, the programmes appear to have been sometimes poorly focused towards certain objectives. There is a balance to be sought between widespread and rapid diffusion of what proved to be an unreliable machine (Gaviotas Columbian programme), and slow penetration, with a conservative design, in a small region of, for example, Mauritania (the French GRET experience [Gaillard and Monvois, 1994]). Other developments, to suit a niche market such as the Kijito experience in Kenya [Batchelor and Harries, 1991], have proved to be difficult to replicate elsewhere. Thirdly, it would appear that many ‘‘key’’ players have not even been involved in the overall process. This is !
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because research organisations have attempted to do everything and it is important to remember that what research organisations do best is research. They are not equipped to take responsibility in the field of design, production engineering, marketing or sales without close cooperation with industries. Consider the structure of a typical windpump country project as previously undertaken. Firstly, a research organisation develops, through research and testing, a new machine. After a certain period of time this ‘‘design’’ is transferred to a developing country where, usually in association with another research organisation, or a company with weak commercial credentials, the design is further tested with the intention of obtaining a ‘‘fixed design’’. However, in numerous cases the whole process has broken down with disappointing results or no results at all; either due to lack of market uptake, or unreliability and poor back-up service to clients. Furthermore, even if the project is perceived as a ‘‘success’’ it is difficult to see how the results can be successfully applied elsewhere with a new developing country participant without that participant going through the full learning curve again. 5. Problems in technology transfer It is important to remember that wind pumping activities are much broader than has been so far mentioned. In general, 3 levels of activities are required, as shown below. Level 1: Introduction of proven technology – market tests Level 2: Technical support – design support, development of new and existing products Level 3: Training and education This article is focused mainly on the Level 2 activities, these being related to technical support. It is envisaged that the Level 1 activities would be undertaken and organised entirely by the developing country partners, probably those companies responsible for selling the product. The third level of activities, although crucial to a successful project overall, can be organised separately from the technical support. The technical support structure for introducing engineering equipment into a developing country may take many forms. Figure 3 depicts one possible scheme and links responsibilities of the various participants/actors involved in the three levels of activity. There is little doubt that one of the areas of great weakness, in windpump market development, has been the absence of inputs from commercial engineering companies from the industrialised countries, prior to the technology being transferred abroad. On the other hand it has to be recognised that there is little incentive for a European engineering company to get involved. There are almost no home markets for mechanically-driven windpumps and all other equipment can usually be made in the overseas developing country. This is the great strength, and weakness, of windpump technology compared with wind electric or solar photovoltaic equipment. In the latter cases there is always something in it for the engineering manufacturer from the industrialised country. With market penetration there is the prospect of selling, if not the whole equipment, then Energy for Sustainable Development
at least key component packs made up of those components which are most difficult to make in the developing country. Probably the most that can be hoped for is that future windpump designs from each organisation and/or university in developed countries are properly tried, tested, and then reviewed by competent design consultants. The latter, provided they are constantly involved in industrial product design evaluation, should be able to make good, to a certain degree, the absence of a European manufacturing company in the transfer processes depicted in Figure 3. Recognising the above limitations, the technical support part of a successful strategy might involve the key activities outlined in Table 1. One of the key problem areas, inevitably, will be the choice of local manufacturers/participants in the last two rows of Table 1. Who will make the wind pumps and why? As Padgett [1995] puts it, the problem of finding a recipient with ‘‘the right type of management dealing with the same markets, with the right production facilities, and with access to the right supplies of parts and raw materials’’. Down the right-hand column of Table 1 appears the problematic question of money and finance. Let us consider the life-cycle of a typical project, not necessarily a windpump project. (See Figure 4a.) Of particular interest is the breakdown of the costs. (See Figure 4b.) Of significance here is that although the long-term material and manufacturing costs are quite low, there are substantial initial costs associated with development and production set-up. Obviously very few developing country companies can tolerate a large debt, and so they have to get loans and then build the loan repayments back into the costs. This is highlighted in Figure 4c. This kind of debt can, and usually does, make the idea of new product development highly risky and probably uneconomical. Because of relatively high interest rates it is likely that the combined costs of materials, manufacturing and loan repayments would make the long-term economic viability of any project doubtful. The question arises: can mechanisms be provided in such a way that promotes the use of beneficial technologies and products but without promoting products which are not self-sustaining in the longer term? In other words the question of why anyone will make windpumps needs to be addressed because no one does something for nothing. It is essential that any way forward provides a mechanism for all key players to gain from a successful project. For instance, one mechanism for enabling design consultants to benefit would be for them to be able to market their finished designs, licensing them to individual manufacturers in different developing countries. The scheme described by Polak and Dawson [1995] is particularly interesting in this respect. The best way to financial viability of a project is to keep the first cost of a locally-produced windpump down to a minimum. One of the authors was involved in obtaining finance for a Poldow windpump for a remote school in Zimbabwe. The 3.5m windpump cost just over US$ 2000 (i.e.. $208/m2) with another $1400 for replacing the existing pump ports, !
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Figure 3. An approach towards the successful implementation of proven technology.
provision of foundations, labour and transport. However, if the construction of a well had been needed the project finance costs would have been substantially higher, and one problem local windpump manufacturers face is the decision of whether to be involved in well-drilling as part of an overall customer service. One basic aim of a windpump project should be that the industry should eventually be self-sustaining. Help, in the form of aid/subsidies, should only therefore be given for the initial ‘‘proven’’ design development, production engineering, technology transfer and initial manufacturing set-up costs. From there on, sales should be sufficient to obtain a healthy profit over and above the on-going costs, i.e., materials, manufacturing, maintenance and other related services. With reference to the earlier product lifecycle diagram the purpose of aid should be to cover the 48
Energy for Sustainable Development
costs that would otherwise be covered by a bank loan, i.e., the initial set-up costs. Aid should also be provided to cover the basic investment costs required to produce a finished design. This aid could be provided for the technology transfer process. The organisational structure shown in Table 1 is therefore one way to provide the incentives required to initiate the development of a self-sustaining local developing country industry producing windpumps. The specific objectives, (1) to develop proven designs, (2) to facilitate technology transfer, and (3) to thereby enable the manufacture of large numbers of windpumps, could also be achieved through such an arrangement. 6. Conclusions This paper has focussed on some of the technology trans!
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Table 1. Possible key activities in technical support part of a successful strategy Activity
Type of organisation
Funding source
Research and new development
Research organisation
Aid organisation
Design
Engineering design consultants in cooperation with research or technical organisations
Aid organisation
Field testing
Engineering design consultants in cooperation with research organisations
Aid organisation
Technology transfer and key component engineering
Local industry in conjunction with design consultants
Aid for technology transfer
Local developing country manufacturer, marketing, maintenance and customer relations
Local industry in conjunction with training consultants
Aid for set-up costs, then machine sales
Figure 4a. The life-cycle of a typical engineering product.
Figure 4b. A breakdown of the various costings.
Figure 4c. The use of loans to avoid large overdraft requirements.
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fer problems associated with windpump technology. Solutions for these problems are required if the use of windpumps is to be successfully promoted. Fundamental to any new strategy should be that it is not specific to any particular country. Once a proven design has been established the technology should be so portable, through the technology transfer process, that it can be applied to other similar countries. However, some prerequisites with regard to a minimum level of manufacturing skills may be required for any particular country to be suitable. Furthermore, minor redesign to take account of local availability of materials or re-matching of the system may be necessary as described earlier. It is important to let each organisation do what it does best. It is also vital that suitable contractual arrangements be put in place if the strategy is to achieve its objectives. Aid organisations have a vital role to play in facilitating the widespread introduction of these new second generation windpumps. They should not be deterred by mistakes of the past and neither should these mistakes be forgotten. Several crucial developments mean the time is now right for positive action. Firstly there is a new framework of international collaboration. Secondly, recent technological advances have resulted in a new and better understanding of the challenges the new technology poses, and finally the need for an effective implementation strategy, as set
out in this paper, is now gaining wider acceptance.
Computer-aided design for feeders: a realistic approach
station. A distributor on the other hand is a circuit of conductors from the distribution transformer to the service mains of the individual consumer. A ring main is adopted for feeders, forming a closed circuit having more than one feeding point. This is basically advantageous for minimising the voltage drop and losses and improving reliability and economy. It has been for quite some time the common practice to consider the voltage drop in a distributor and neglect it in the case of a feeder. Kelvin’s law was adopted for the design of feeders based on current carrying capacity and financial loss [Cotton, 1960]. This approach is not most suitable because the voltages on the secondary side are far below the required standards of electricity supply satisfying the voltage regulation. The above suggestion becomes more important when the distribution transformers are numerous and the feeders run for long distances in an open manner. In the case of distributors, the loads become heavy and the distributors are run for long distances [Manohar, 1986]. The voltages at the far end of the distributors are very low. To avoid this, ring distributors have been adopted. They form a closed circuit and have one or more feeding points. Copper conductor can be saved in this manner. One can attempt to adopt the same property for feeder circuits. Power transformers replace distribution transformers, the feeders replace the distributors and the distribution transformers replace loads when applying the same principles to feeders. On the whole the high-voltage,
C. Kumar Ratnavel Subramaniam Polytechnic, Dindigul-5, Tamil Nadu, India K. Srikrishna Department of Electrical and Electronics Engineering, Thiagarajar College of Engineering, Madurai-15, Tamil Nadu, India 1. Introduction Electrical power today plays an increasingly important role in the life of the community and development of various sectors of the economy. In every country, electrical power consumption has been continuously rising. This in turn has led to more power stations and consequent increase in power transmission lines from generating stations and the number of feeders and distributors from various sub-stations to the load centres. Transmission lines transmit power over long distances. If the transmission voltage is 275 kV and above, it is called primary transmission and if it is 66 kV to 220 kV, it is called secondary transmission [Wadhwa, 1993]. The electrical power system has two components: the feeder and the distributor. A feeder in a network is a circuit carrying power from a main sub-station to a secondary sub50
Energy for Sustainable Development
References Batchelor, S.J., and Harries, M.A.A., 1991. ‘‘An evaluation of Kijito windpumps’’, Proceedings of the European Wind Energy Conference on Wind Energy: Technology and Implementation’’, Amsterdam, pp. 861-865, Elsevier Science Publishers B.V. Bishop, N.W.M., 1991. Recorded discussion, Part II, Proceedings of the European Wind Energy Conference on Wind Energy: Technology and Implementation, Amsterdam, p. 115, Elsevier Science Publishers B.V. Burton, J.D., and Davies, D.G., 1996. ‘‘Dynamic model of a wind-driven lift pump’’, Proc. I, Mech. Eng, Vol. 210, Part A, Journal of Power and Energy, UK. Gaillard, M., and Monvois, J., 1994. ‘‘Le project Alizes en Mauritanie’’, Groupe recherché et d’Echanges Technologiques, Systèmes Solaire 100, pp. 97-107. Hacker, R.J., and Munro, D.K., 1995. ‘‘Market potential for renewable energy systems’’, Proceedings of BWEA/RAL Workshop ‘‘Technology and Implementation Issues Relating to Renewable Energy Systems in Developing Countries’’, UK, June. I.T. Power, 1994. Proceedings of International Workshop ‘‘Prospects for International Collaboration on Windpumps’’, Silsoe, UK, published by I.T. Power, UK. Padgett, B., 1995. ‘‘Commercial links with developing countries’’, Proceedings of BWEA/RAL Workshop ‘‘Technology and Implementation Issues Relating to Renewable Energy Systems in Developing Countries’’, UK, June. Polak, T.A., and Dawson, P., 1995. ‘‘Wind and water: The Poldaw windpump’’, Appropriate Technology, Vol. 2, No. 4, pp 34-35, UK, March. Smulders, P.T., 1995. ‘‘Wind water pumping – the forgotten option’’, Proceedings of BWEA/RAL Workshop ‘‘Technology and Implementation Issues Relating to Renewable Energy Systems in Developing Countries’’, UK, June. Smulders, P.T., Burton, J.D., Pinilla, A.E., and Stacey, G., 1994. ‘‘The 3S-pump project: piston pump innovation for wind pumps’’, Paper presented at the European Wind Energy Conference (EWEC 94), Thessaloniki, Greece. UNDP, 1988. UNDP Global Wind Pump Evaluation Programme 1987-88.
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Volume III No. 2
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July 1996
Technology and implementation issues related to water-pumping windmills
paper picks up on these issues as they relate to the introduction of windpumps for new markets, and also draws upon the contributions made at an international seminar held at Silsoe College, Bedfordshire, UK, July, 1994 [I.T. Power, 1994].
N.W.M. Bishop
2. A review of water-pumping windmill technology developments
Random Loading and Design Group, Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom J.D. Burton Dept. Ing. Mecánica, La Universidad de Los Andes, Apartado aereo 4976, Santa Mé de Bogotá, Colombia 1. Introduction The UNDP Global Windpump Evaluation Programme [UNDP, 1988] undertaken by the World Bank in 1987-88 estimated a potential market for 500,000 low-cost windpumps worldwide. In fact water-pumping windmills are already in use in developing countries and are important to local communities. For instance, windpumps are used for human drinking water supply, livestock maintenance and crop irrigation. With this in mind, substantial research and development projects aimed at providing low-cost windpumps have been undertaken, particularly in the UK for the Overseas Development Administration and in the Netherlands for the Dutch government. However, successful projects focused on implementation of the technology are very rare. Certainly, realisation of even a fraction of the potential which exists has not occurred, and so the question that needs to be asked is: why? Probably the most important factor is that many of the so-called ‘‘soft’’ technology problems were not addressed. Unfortunately most of the new technology development with windpumps was undertaken by universities and research organisations, who predictably focused on technological innovation. Some of the ‘‘soft’’ problems in Padgett’s [1995] list were for the most part overlooked. Padgett identified a number of wider aspects to be taken into account when transferring technology from the ‘‘West’’ to small developing country manufacturers. These included: intellectual property; financial resources; manufacturing and marketing capability; design and development; test facilities; business and technical consultancy requirements; and quality control. At the present time the British ODA has an ongoing programme to look at the obstacles to, and opportunities for, marketing of windpumps in some 22 developing countries [Hacker and Munro, 1995]. Other than this, at the present time, new activities aimed at implementing water-pumping windmill technology are almost non-existent. At a recent British Wind Energy Association-sponsored workshop a paper was presented [Smulders, 1995], ‘‘Wind water pumping – the forgotten option’’, that correctly sums up the present situation and examines some of the reasons for lack of widespread activity. This present
44
Energy for Sustainable Development
The majority of people, when asked about windpumps, would envisage the so-called ‘‘American’’ style of machine which was developed in the USA during the 19th century. This technology has gained widespread acceptance throughout the world with many hundreds of thousands being installed. It is a relatively expensive piece of equipment, in part because it has a gearbox to reduce the speed of the pump, and is generally not suitable for local production because of its complex construction. A cost running into several thousands of dollars would not be untypical. It has, however, gained a very good reputation for reliability. This kind of technology has therefore addressed the needs of a particular market where cost is less important, such as for large ranches where the windpump needs to operate unattended for long periods with a minimum of human intervention. The technology is unusual in that it has remained largely unchanged for over one hundred years. Established manufacturers exist in Australia (e.g., the Southern Cross or Yellowtail machines), South Africa (e.g., the Climax machine), the USA (e.g., Aermotor, Dempster or Fiasa machines) and Argentina (e.g., Fiasa). Figure 1 depicts a typical American type of machine. From this technology the so-called second generation windpumps have been developed (see Figure 2). Most of these machines have appeared over the last 20 years, e.g., ITDG (UK), Gaviotas and Jober (Colombia), CAAMS (China), CWD (Netherlands), BHEL (Kenya) and Oasis (France), and were developed with local production in mind. The three main requirements of such machines are that they must be cheap to buy or make, efficient in terms of output, and structurally reliable. As a consequence of the economic situation in most developing countries the first requirement usually means that the windmill must be made using local materials and labour, and this is why local manufacturability is so important. The use of standard materials, e.g., angle iron, ball-bearings, pipes, steel plates, etc., and the absence of more complex manufacturing details such as castings are important. Gearboxes are also usually not employed. In some cases the rotor has fewer blades in order to save on material costs, and so rotates faster. The second generation machines have focused on a different market for water pumps where there is an important local need for water but where initial capital is limited. This includes, for instance, provision of drinking water to rural areas and irrigation. In this case local manufacturability becomes the overriding issue because of the importance of cost mentioned above and because of the lack of foreign capital.
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3. Recent solutions to engineering problems With the introduction of these new second generation windpumps there have come a wide variety of reliability problems. Perhaps it was because the American type of machine was so reliable that too little effort focused on this issue. However, the behaviour of the two kinds of machines is fundamentally different. The American type of machine was developed through trial and error over a long period of time. Furthermore, because of its relatively slow-running rotor and the presence of a gearbox, the response of the machine can be accurately characterised using static design principles. In contrast, modern or second generation windpumps usually comprise a direct drive (no gearbox), are lightweight (for reduced cost) and relatively fast-running (because of the small rotor size or because of fewer rotor blades). Sometimes the rotor is made deliberately large [Polak and Dawson, 1995] so as to slow the rotor down to speeds that the direct-coupled single-acting pump can handle. For the faster-running machines, and probably also for the not so fast machines, there is a strong interaction between the dynamic behaviour of the ‘‘topside’’ tower and rotor system and the ‘‘bottomside’’ pump system. It is therefore essential that any design nowadays is founded on sound dynamic analysis principles. This is perhaps where much of the recent work on second generation machines has been lacking. Many of these second generation machines have no softness built into the design. A simple analogy is to drive a car down a bumpy road after removing the shock absorbers and springs [Bishop, 1991]. A good parallel to make is the contrast between a 19th century stone arch bridge and a modern aircraft. Stone arch bridges like the traditional American windpump were developed over a long period of time through trial and error. Aircraft design like modern windpump design requires an analysis approach founded on sophisticated dynamics and reliability tools. Dynamic loads which originate in the pump system can, at least in part, be dealt with using improvements and modifications to the pump and fluid system. It might be thought that after centuries of use, the lift-pump, together with its dynamics, was well understood. This is not the case. Most hand-pump arrangements are driven at speeds where dynamic behaviour hardly matters, and even the traditional American fan mill has gear reduction to slow the pump down. Only in recent times, when there has been a move towards either electric motor drive (from solar panels), or direct coupling to small diameter mills, has the pump moved sufficiently fast for dynamic behaviour to become important. Both riser pipe flow transients, together with distributed hydraulic impedance, and lift rod loads, together with attendant elasticity, have to be taken into account at these higher speeds [Burton and Davies, 1996]. The valve sequencing with the lift-pump, and how it is controlled, is vital. Hydraulic load is carried on the bottom valve and riser pipe on the down stroke and on the piston valve and lift rod on the upstroke. How the load is switched from one to the other at the end of each stroke Energy for Sustainable Development
Figure 1. A typical ‘‘American’’ type of water pumping windmill.
becomes, at higher speed, a problem requiring careful consideration if an adequate level of reliability is to be achieved. Tools are available today to both understand and engineer these pumps properly. Industrially, high-speed reciprocating pumps run at eight or ten times the speed of lift-pumps, and have involved modern dynamic techniques in their design. Unfortunately, many windpump manufacturers exercise little control over the size of the pump, and even more importantly, the size of the riser pipe attached to their mill. The riser pipe is often restricted in the interests of economy but can easily cause very high dynamic loads on the lift rod. Structural vibrations, component vibrations and shock forces in the pump rod can be analysed by looking at the topside dynamics of the system. Various aspects of structural behaviour can be included under this heading, such as ‘‘pump rod shock forces’’, ‘‘component vibrations and response’’ and ‘‘global structural vibration and response’’. Although ‘‘pump rod shock forces’’ can be envisaged as originating in the pump fluid system, they also affect the topside of the windmill. They can cause both failure of the pump rod itself and failure of the tower and its components. Vibration of the tower, vanes, rotor blades, etc. can be described under the heading ‘‘component vibrations and response’’. Once individual components, such as the tower, start to vibrate, the movement itself can then form an additional load for other components. An understanding of such dynamic interaction between structural elements is vital if structural reliability is to be assured and this can be included under the heading ‘‘global structural vibration and response’’. In order to obtain a complete design methodology it is important that a thorough understanding of the above types of structural behaviour !
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College London and the University of Reading. The main findings would indicate the need to decouple the peak transient loads between topside and bottomside. In order to verify the theoretical work a test site has been set up at Silsoe College, Bedfordshire, in the UK. Three test beds are available, two with boreholes (at 25m and 43m respectively) and one with a surface tank. The location of the site is reasonable for testing, being of undulating hills with a mean wind speed of 5.0 m/s. A monitoring station on the site is capable of storing both performance data (output, wind speed, direction, etc.) and structural responses (rotor speed, yaw position, tower and blade stresses, etc.). A computer-based system is used to acquire, analyse and store the results. Currently three machines are being tested, these being the CWD2000, CWD2740 and Gaviotas direct-drive machines. It is hoped that the site can become an established location for wind-pumping test work. It is clear from the above that although many of the hard engineering issues have been solved, or are currently being addressed, the question that remains is, how to utilise these solutions, and this is where the issues of technology transfer and market development need to be addressed. 4. Lessons to be learnt from the past
Figure 2. A typical 2nd generation machine, the Gaviotas machine.
is obtained. The cyclic behaviour of the lift pump can interact with the rest of the system through either the drive input (the lift rod) or through the riser pipe flow transients at discharge. Rod loads may be modified by adjusting the elasticity in the windmill tower (topside dynamics), at the point of support of the riser, or in the rod itself (bottomside dynamics). Flow transients may be modified by either altering the discharge (riser pipe) impedance or by the incorporation of elastic elements into the pumping chamber. A recently completed project shared between the Technical University, Eindhoven, Los Andes University in Colombia, and the University of Reading [Smulders et al., 1994] has focused particularly upon this latter approach. The dynamic safety system used to keep the rotor pointing into the wind (and to point it out of the wind at high wind speeds) has a significant effect on the loads present in the tower because of gyroscopic and shock forces caused by overspeeding (topside dynamics) and in the pump rod and pump system (bottomside dynamics) because of the resulting pumping speed variation. It is therefore obvious that an understanding of both topside and bottomside dynamics, as well as the interaction between the two, is an essential prerequisite to a reliable structural system. Both ‘‘topside’’ and ‘‘bottomside’’ dynamic interaction have been the subject of a recently completed UK-funded project (June 1993-December 1995) between University 46
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Much effort and many person-years have been expended over the last 20 years developing modern or second generation windpump machines and yet successes in the field are rare. It is worth considering what might be the dominant factors behind these failures in order to see what lessons can be learnt for the future. First of all, much of the effort has been uncoordinated. Two of the largest European programmes of work, the CWD programme (1976-1991) and the ITDG-IT Power work (1976 onwards) have been undertaken almost completely separately. Furthermore, because many programmes of work have been undertaken using developing country projects it has been very difficult to transfer results between different programmes. The Dutch-UNDP support for the Colombian Gaviotas project in the late 1970s and early 1980s which resulted in the production of some 8000 mills is a case in point. As a result of this lack of coordination many different programmes of work have been undertaken in parallel with much replication of effort. Secondly, the programmes appear to have been sometimes poorly focused towards certain objectives. There is a balance to be sought between widespread and rapid diffusion of what proved to be an unreliable machine (Gaviotas Columbian programme), and slow penetration, with a conservative design, in a small region of, for example, Mauritania (the French GRET experience [Gaillard and Monvois, 1994]). Other developments, to suit a niche market such as the Kijito experience in Kenya [Batchelor and Harries, 1991], have proved to be difficult to replicate elsewhere. Thirdly, it would appear that many ‘‘key’’ players have not even been involved in the overall process. This is !
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because research organisations have attempted to do everything and it is important to remember that what research organisations do best is research. They are not equipped to take responsibility in the field of design, production engineering, marketing or sales without close cooperation with industries. Consider the structure of a typical windpump country project as previously undertaken. Firstly, a research organisation develops, through research and testing, a new machine. After a certain period of time this ‘‘design’’ is transferred to a developing country where, usually in association with another research organisation, or a company with weak commercial credentials, the design is further tested with the intention of obtaining a ‘‘fixed design’’. However, in numerous cases the whole process has broken down with disappointing results or no results at all; either due to lack of market uptake, or unreliability and poor back-up service to clients. Furthermore, even if the project is perceived as a ‘‘success’’ it is difficult to see how the results can be successfully applied elsewhere with a new developing country participant without that participant going through the full learning curve again. 5. Problems in technology transfer It is important to remember that wind pumping activities are much broader than has been so far mentioned. In general, 3 levels of activities are required, as shown below. Level 1: Introduction of proven technology – market tests Level 2: Technical support – design support, development of new and existing products Level 3: Training and education This article is focused mainly on the Level 2 activities, these being related to technical support. It is envisaged that the Level 1 activities would be undertaken and organised entirely by the developing country partners, probably those companies responsible for selling the product. The third level of activities, although crucial to a successful project overall, can be organised separately from the technical support. The technical support structure for introducing engineering equipment into a developing country may take many forms. Figure 3 depicts one possible scheme and links responsibilities of the various participants/actors involved in the three levels of activity. There is little doubt that one of the areas of great weakness, in windpump market development, has been the absence of inputs from commercial engineering companies from the industrialised countries, prior to the technology being transferred abroad. On the other hand it has to be recognised that there is little incentive for a European engineering company to get involved. There are almost no home markets for mechanically-driven windpumps and all other equipment can usually be made in the overseas developing country. This is the great strength, and weakness, of windpump technology compared with wind electric or solar photovoltaic equipment. In the latter cases there is always something in it for the engineering manufacturer from the industrialised country. With market penetration there is the prospect of selling, if not the whole equipment, then Energy for Sustainable Development
at least key component packs made up of those components which are most difficult to make in the developing country. Probably the most that can be hoped for is that future windpump designs from each organisation and/or university in developed countries are properly tried, tested, and then reviewed by competent design consultants. The latter, provided they are constantly involved in industrial product design evaluation, should be able to make good, to a certain degree, the absence of a European manufacturing company in the transfer processes depicted in Figure 3. Recognising the above limitations, the technical support part of a successful strategy might involve the key activities outlined in Table 1. One of the key problem areas, inevitably, will be the choice of local manufacturers/participants in the last two rows of Table 1. Who will make the wind pumps and why? As Padgett [1995] puts it, the problem of finding a recipient with ‘‘the right type of management dealing with the same markets, with the right production facilities, and with access to the right supplies of parts and raw materials’’. Down the right-hand column of Table 1 appears the problematic question of money and finance. Let us consider the life-cycle of a typical project, not necessarily a windpump project. (See Figure 4a.) Of particular interest is the breakdown of the costs. (See Figure 4b.) Of significance here is that although the long-term material and manufacturing costs are quite low, there are substantial initial costs associated with development and production set-up. Obviously very few developing country companies can tolerate a large debt, and so they have to get loans and then build the loan repayments back into the costs. This is highlighted in Figure 4c. This kind of debt can, and usually does, make the idea of new product development highly risky and probably uneconomical. Because of relatively high interest rates it is likely that the combined costs of materials, manufacturing and loan repayments would make the long-term economic viability of any project doubtful. The question arises: can mechanisms be provided in such a way that promotes the use of beneficial technologies and products but without promoting products which are not self-sustaining in the longer term? In other words the question of why anyone will make windpumps needs to be addressed because no one does something for nothing. It is essential that any way forward provides a mechanism for all key players to gain from a successful project. For instance, one mechanism for enabling design consultants to benefit would be for them to be able to market their finished designs, licensing them to individual manufacturers in different developing countries. The scheme described by Polak and Dawson [1995] is particularly interesting in this respect. The best way to financial viability of a project is to keep the first cost of a locally-produced windpump down to a minimum. One of the authors was involved in obtaining finance for a Poldow windpump for a remote school in Zimbabwe. The 3.5m windpump cost just over US$ 2000 (i.e.. $208/m2) with another $1400 for replacing the existing pump ports, !
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Figure 3. An approach towards the successful implementation of proven technology.
provision of foundations, labour and transport. However, if the construction of a well had been needed the project finance costs would have been substantially higher, and one problem local windpump manufacturers face is the decision of whether to be involved in well-drilling as part of an overall customer service. One basic aim of a windpump project should be that the industry should eventually be self-sustaining. Help, in the form of aid/subsidies, should only therefore be given for the initial ‘‘proven’’ design development, production engineering, technology transfer and initial manufacturing set-up costs. From there on, sales should be sufficient to obtain a healthy profit over and above the on-going costs, i.e., materials, manufacturing, maintenance and other related services. With reference to the earlier product lifecycle diagram the purpose of aid should be to cover the 48
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costs that would otherwise be covered by a bank loan, i.e., the initial set-up costs. Aid should also be provided to cover the basic investment costs required to produce a finished design. This aid could be provided for the technology transfer process. The organisational structure shown in Table 1 is therefore one way to provide the incentives required to initiate the development of a self-sustaining local developing country industry producing windpumps. The specific objectives, (1) to develop proven designs, (2) to facilitate technology transfer, and (3) to thereby enable the manufacture of large numbers of windpumps, could also be achieved through such an arrangement. 6. Conclusions This paper has focussed on some of the technology trans!
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Table 1. Possible key activities in technical support part of a successful strategy Activity
Type of organisation
Funding source
Research and new development
Research organisation
Aid organisation
Design
Engineering design consultants in cooperation with research or technical organisations
Aid organisation
Field testing
Engineering design consultants in cooperation with research organisations
Aid organisation
Technology transfer and key component engineering
Local industry in conjunction with design consultants
Aid for technology transfer
Local developing country manufacturer, marketing, maintenance and customer relations
Local industry in conjunction with training consultants
Aid for set-up costs, then machine sales
Figure 4a. The life-cycle of a typical engineering product.
Figure 4b. A breakdown of the various costings.
Figure 4c. The use of loans to avoid large overdraft requirements.
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fer problems associated with windpump technology. Solutions for these problems are required if the use of windpumps is to be successfully promoted. Fundamental to any new strategy should be that it is not specific to any particular country. Once a proven design has been established the technology should be so portable, through the technology transfer process, that it can be applied to other similar countries. However, some prerequisites with regard to a minimum level of manufacturing skills may be required for any particular country to be suitable. Furthermore, minor redesign to take account of local availability of materials or re-matching of the system may be necessary as described earlier. It is important to let each organisation do what it does best. It is also vital that suitable contractual arrangements be put in place if the strategy is to achieve its objectives. Aid organisations have a vital role to play in facilitating the widespread introduction of these new second generation windpumps. They should not be deterred by mistakes of the past and neither should these mistakes be forgotten. Several crucial developments mean the time is now right for positive action. Firstly there is a new framework of international collaboration. Secondly, recent technological advances have resulted in a new and better understanding of the challenges the new technology poses, and finally the need for an effective implementation strategy, as set
out in this paper, is now gaining wider acceptance.
Computer-aided design for feeders: a realistic approach
station. A distributor on the other hand is a circuit of conductors from the distribution transformer to the service mains of the individual consumer. A ring main is adopted for feeders, forming a closed circuit having more than one feeding point. This is basically advantageous for minimising the voltage drop and losses and improving reliability and economy. It has been for quite some time the common practice to consider the voltage drop in a distributor and neglect it in the case of a feeder. Kelvin’s law was adopted for the design of feeders based on current carrying capacity and financial loss [Cotton, 1960]. This approach is not most suitable because the voltages on the secondary side are far below the required standards of electricity supply satisfying the voltage regulation. The above suggestion becomes more important when the distribution transformers are numerous and the feeders run for long distances in an open manner. In the case of distributors, the loads become heavy and the distributors are run for long distances [Manohar, 1986]. The voltages at the far end of the distributors are very low. To avoid this, ring distributors have been adopted. They form a closed circuit and have one or more feeding points. Copper conductor can be saved in this manner. One can attempt to adopt the same property for feeder circuits. Power transformers replace distribution transformers, the feeders replace the distributors and the distribution transformers replace loads when applying the same principles to feeders. On the whole the high-voltage,
C. Kumar Ratnavel Subramaniam Polytechnic, Dindigul-5, Tamil Nadu, India K. Srikrishna Department of Electrical and Electronics Engineering, Thiagarajar College of Engineering, Madurai-15, Tamil Nadu, India 1. Introduction Electrical power today plays an increasingly important role in the life of the community and development of various sectors of the economy. In every country, electrical power consumption has been continuously rising. This in turn has led to more power stations and consequent increase in power transmission lines from generating stations and the number of feeders and distributors from various sub-stations to the load centres. Transmission lines transmit power over long distances. If the transmission voltage is 275 kV and above, it is called primary transmission and if it is 66 kV to 220 kV, it is called secondary transmission [Wadhwa, 1993]. The electrical power system has two components: the feeder and the distributor. A feeder in a network is a circuit carrying power from a main sub-station to a secondary sub50
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References Batchelor, S.J., and Harries, M.A.A., 1991. ‘‘An evaluation of Kijito windpumps’’, Proceedings of the European Wind Energy Conference on Wind Energy: Technology and Implementation’’, Amsterdam, pp. 861-865, Elsevier Science Publishers B.V. Bishop, N.W.M., 1991. Recorded discussion, Part II, Proceedings of the European Wind Energy Conference on Wind Energy: Technology and Implementation, Amsterdam, p. 115, Elsevier Science Publishers B.V. Burton, J.D., and Davies, D.G., 1996. ‘‘Dynamic model of a wind-driven lift pump’’, Proc. I, Mech. Eng, Vol. 210, Part A, Journal of Power and Energy, UK. Gaillard, M., and Monvois, J., 1994. ‘‘Le project Alizes en Mauritanie’’, Groupe recherché et d’Echanges Technologiques, Systèmes Solaire 100, pp. 97-107. Hacker, R.J., and Munro, D.K., 1995. ‘‘Market potential for renewable energy systems’’, Proceedings of BWEA/RAL Workshop ‘‘Technology and Implementation Issues Relating to Renewable Energy Systems in Developing Countries’’, UK, June. I.T. Power, 1994. Proceedings of International Workshop ‘‘Prospects for International Collaboration on Windpumps’’, Silsoe, UK, published by I.T. Power, UK. Padgett, B., 1995. ‘‘Commercial links with developing countries’’, Proceedings of BWEA/RAL Workshop ‘‘Technology and Implementation Issues Relating to Renewable Energy Systems in Developing Countries’’, UK, June. Polak, T.A., and Dawson, P., 1995. ‘‘Wind and water: The Poldaw windpump’’, Appropriate Technology, Vol. 2, No. 4, pp 34-35, UK, March. Smulders, P.T., 1995. ‘‘Wind water pumping – the forgotten option’’, Proceedings of BWEA/RAL Workshop ‘‘Technology and Implementation Issues Relating to Renewable Energy Systems in Developing Countries’’, UK, June. Smulders, P.T., Burton, J.D., Pinilla, A.E., and Stacey, G., 1994. ‘‘The 3S-pump project: piston pump innovation for wind pumps’’, Paper presented at the European Wind Energy Conference (EWEC 94), Thessaloniki, Greece. UNDP, 1988. UNDP Global Wind Pump Evaluation Programme 1987-88.
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