SMALL SCALE WIND ENERGY SYSTEMS

 


"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 (DGIS-DML/KM). Citation is encouraged on the condition that the source is indicated.


May 1999

EDITORIAL

Since the last SSWES issue in December 1997, lots of things have happened to get the newsletter continued. The idea was to bring the newsletter directly there where people may benefit of it and assist them in getting the news, finance printing and distribution, and stimulate the exchange of local experience and knowledge. By bringing the newsletter among the people, it is hoped to add to the importance given to "small wind" by institutions in the region. Fortunately, the Ministry of Foreign Affairs of the Netherlands has decided to support the newsletter for two more years, covering two issues yearly.

RED has found two partners interested in co-editing and producing the magazine. They are GEDA in Gujarat, India and ITDG´s local office in Lima, Peru. Both have been involved in wind energy since many years and are currently promoting the use of "small wind" in their region. GEDA is partner in the regional Wind Pumping Network India, which maintains relations with Vietnam, China and the Philippines. ITDG has close contacts with CINER in Bolivia and many organisations involved in small hydro in Latin America.

GEDA has recently initiated publication of a new and attractive wind energy magazine, FIRKI. With the extra financial inputs from SSWES and the supply of world-wide news, GEDA expects to be able to consolidate their initiative and improve the quality. ITDG plans to include the SSWES in their existing HIDRORED magazine and offer information on both wind and hydro-energy to a large group of subscribers. RED will do an important part of the newsgathering and act as a co-ordinator between both partners.

At the start of the new SSWES-project, the Asian and the South American version will have the same contents; this will change in the future as both editions acquire their own, regional accent. Right from the beginning however, the GEDA-letter will be published in English and the ITDG-version in Spanish.

The project foresees in setting up an electronic version of the newsletter by the local partners GEDA and ITDG. While the initial goal is merely to make it accessible to people world-wide without the need for costly, printed copies, in the future the electronic newsletter may evolve towards some bulletin board to announce events, seek for project partners, and link to valuable information resources nowadays available on the web.

We hope you enjoy it and as always... contact us!

Jan de Jongh and Remi Rijs, editors

 

Wind Energy in Northern Patagonia

Patagonia -in the South of Argentina- is one of the windiest regions around the world. While quasi-permanent western winds blow with a yearly average speed above 6 m/s, the major problem affecting the development of this wind resource for small wind applications, is the lack of inhabitants.

Nevertheless, in the province of Chubut, located between 42º and 46º S, a significant number of people live dispersed in small communities. During nine months of the year, their children live in boarding schools located in small villages or on isolated sites. Electricity is supplied by a diesel-generator only during the morning and evening, with the diesel fuel being provided regularly by the province government. In 1997, small wind turbines were installed on some selected sites in Chubut to increase the quality of life of the people in the villages and the children who attend school.

Since August 1997, a cluster of eight small wind turbines is producing energy for the isolated boarding school of Piedra Parada (north-west of Chubut). Thirty-eight people live there: the director of the school, three teachers, one librarian, nine assistants (most of them going home on Saturday and Sunday), and twenty-four students. The wind turbines are built in Cordoba, Argentina, and consist of a three-bladed rotor with a diameter of 2.05 m that drives a 600-watt asynchronous generator. The rotor is mounted on a triangular, open-lattice tower of 6-m height.

The turbines charge two units of eight 6V/200 Ah batteries each that are used for school and domestic lighting only; only high-efficiency lamps are used. The batteries, control panel and the diesel generator are installed in a small building.

 

Figure: Small Windchargers at the Piedra Parada site, Argentina

During the first five months of operation, the energy production was 995 kWh during 1711 hours. Mr. Angel Torres, the director of the school, affirms that "thanks to the wind generator we are able to have twenty-four hours of electricity, minimising the use of the diesel generator." The local supplier however, claims that even though the system reliability is quite good in the field, the site maintenance is fairly poor. This affects in some cases the normal functioning of the wind turbines, particularly under strong wind conditions when it is necessary to stop them manually.

Notwithstanding this comment, it is expected that the experience at Piedra Parada, together with that of other projects in the Chubut province, can stimulate the use of small wind turbines in remote areas, as well as the development of a potential market.

(Oscar A. Frumento, Centro Nacional Patagónico Area Física Ambiental, Boulevard Brown S/N, (9120) Puerto Madryn, Argentina; phone: (54)(965)51 375; fax: (54)(965)51 543; email: oscar@cenpat.edu.ar)

 

Rope Windpump Evaluation in Nicaragua

In the first half of 1998 the Nicaraguan rope windpump was evaluated as part of a project to transfer the technology to other countries in Latin America. The evaluation project was carried out by RED vof from the Netherlands with inputs from Gamos Ltd (UK), ERA (Costa Rica) and the Universidad Nacional de Ingeniería and CICUTEC from Managua, assisted by host organisation CESADE and workshop AMEC. The project was financed by the Royal Embassy of the Netherlands in Managua and addressed three major issues: the evaluation of the rope windpump on technical, social and economic aspects; the dissemination of the results at two workshops in Managua; and a first transfer of the technology to four selected manufacturers in Latin America.

The evaluation of the rope windpump was based upon an evaluation mission to Nicaragua, an end-use survey and a technical measuring programme. The main objective was to draw conclusions on the current status of the windpump in Nicaragua and to give recommendations regarding technical improvements and transfer.

The results were presented during two workshops in Managua. The first workshop was held on Friday 24 April and had an informative character to draw the attention of the many institutions involved in rural development in the country. It was visited by almost a hundred people.

 

Figure: Meeting at the Workshop AMEC in Managua, April 1998

The second workshop was held from 27-29 April and brought together 12 people from 8 different countries in Latin America. These people were selected from among potential manufacturers and development organisations, which had shown their interest in promoting the windpump in their home country. The workshop discussed the possibilities for transfer and viewed the potential fields of application outside Nicaragua. Also, contacts were established with potential candidates with whom to start a transfer of the rope windpump. (In the second half of 1998 and the first months of this year, the rope windpump was transferred to Peru, Bolivia, Cuba and Guatemala -see also the article "Rope Windpump Transfer to Guatemala" elsewhere in this issue.)

The evaluation confirms that the rope windpump can be operated and maintained by the user, basically because of the widespread availability of spare parts for the rope (hand) pump in Nicaragua. Small damages to the windmill structure can often be repaired with some creativity and locally available material. Its initial cost is between 25% and 40% compared to that for a traditional windpump, while the recurrent costs are sufficiently low to make it an attractive option to other pumping technologies. Based on the limited field data, one estimates a unit water cost of about US$ 0.15,- per m3 at a pumping head of 20 m.

As yet, little data are available on the economic impact of the rope windpump as used in small irrigation schemes by subsistence farmers. However, it clearly has the potential to bring along an important improvement in quality of life for this target group and their families; there is a growing demand for the windpump in the country both from small farmers and the wealthier cattle holders.

The standard rope windpump has the peculiarity that the transmission rope limits the free movement of the windmill head under variable wind directions (the head can turn over a range of 270 degrees). In countries with a rather constant wind direction this is not much of a problem, but in areas with variable winds it considerably reduces its functionality. AMEC and CESADE are now working on the improved "multigiratorio" model to eliminate this drawback, but this is still under development. If one succeeds in further improving the current design and develops a general-purpose model, the Nicaraguan rope windpump would not only be a valuable pumping option for the lower market segment, but also become a competitive windmill for the more demanding user, even under variable wind conditions.

(Remi Rijs – editor)

 

Interest for Rope Windpump in Guatemala

US-based organisation NRECA and the Catholic non-governmental organisation Caritas have recently introduced the Nicaraguan rope windpump in Guatemala. This introduction was part of a project financed by the Dutch Embassy in Nicaragua to evaluate and transfer the windpump to other countries.

The Nicaraguan rope windpump is a lightweight, innovative windmill built around the proven technology of the rope handpump, of which twenty thousand have been sold in Central America. The windpump is a combined effort of the organisation CESADE and manufacturer AMEC in Managua to develop a simple, effective and cheap windpump design suitable for domestic use, cattle watering and small-scale irrigation. Costing about US$ 750,- (in Nicaragua), it is much cheaper than a classical "American" windpump but it also requires more attention from the user.

NRECA, a non-profit organisation working in rural electrification with offices in most Central and South American countries, develops electrification projects based on conventional and renewable energy sources. Tipped by Mr. Hugo Arriaza from NRECA-Guatemala, Mr. Carlos Sett from the Caritas office in Guatemala and Mrs. Rosina from Caritas-El Salvador visited the "International Workshop on the Nicaraguan Rope Windpump" held in Managua in May 1998.

Mr. Carlos Sett is director of Caritas in the Zacapa region in the western part of the country. He recognises the need for low-cost water pumping in the area, especially in the dry season. Besides, some 20% of the people do not have electricity yet. Since the capacity of the people, well properties and wind characteristics in Zacapa are more or less comparable to those in Nicaragua, it was concluded that the rope windpump might bring some relief to these people. Therefore, NRECA and Caritas applied for a transfer of a demonstration rope windpump to verify its appropriateness for domestic water supply and small-scale irrigation in this area. As part of the transfer, one would also test the combination of the windpump with a generator for battery charging.

January 1999, two specialists from CESADE and AMEC travelled to Guatemala to transfer the windpump to local manufacturer Galdamez and several technicians from Caritas. Galdamez is a small workshop with six employees with a serious interest in producing and commercialising the rope windpump. Apart from the wind pump, a rope handpump was also built and both systems were installed on two domestic wells at a 3-km distance from Zacapa. Since then, many families, farmers and other interested people visited the demonstration sites and showed to be enthusiastic about the idea to have a rope handpump or windpump near their house or on their land.

Caritas and NRECA are now formulating a project to further disseminate the rope pump technology, including the local production of about 60 pumps (rope handpumps, bike (pedal) pumps and windpumps). One has also scheduled the installation of several windchargers. This allows to make a cost-benefit analysis and compare it to other technologies, particularly photovoltaics. In this phase a number of components will be imported from Nicaragua.

Personnel from Caritas and Galdamez will receive "on-the-spot" training. This will cover technical aspects such as design, production, installation and maintenance of the windpump, but also its application for distributing water for household use to improve water quality, and for setting up irrigation methods for fodder, crops and vegetables. Hugo Arriaza and Carlos Sett consider this project as a first step to the commercial production of the rope pump in Guatemala, independent from donations and support organisations.

(Henk Holtslag, CESADE, Apartado Postal JN 4317, Managua, Nicaragua; phone: (505)266 9149; fax: (505)266 9270; email: holtslag.dapper@wxs.nl)

 

News from the Philippines

Windmill manufacturer Hector Jover (Jover Light Industries) reports about the advances in the development of a small windcharger and his windpump sales during the last period. Hector co-operates with Mr. Silverio Navarro from Solar Electric Co. who designs small-scale electrification systems and charge controllers. Both live on the island of Iloilo, one of the larger islands of the country. They write:

"We are having a project of a windcharger using a car alternator in which the exciter coil has been replaced with a permanent, toroidal magnet. Silver Navarro was able to purchase some neodymium magnets in Hong Kong according to my design. Using Silver’s 1.5-m rotor, the highest current we obtained was 15 amps to charge a 12-volt battery. With the American wind turbines in our office, we were able to copy some blade profiles and built fibreglass replicas. It is still a long way to go but we are on the right track.

Figure: The Jober Windcharger

Another windcharger delivers 50 watts at a wind speed of 10 m/s with just one-meter rotor diameter. The power curve is almost linear thanks to the furling mechanism design and the cut-in wind speed is around 3 m/s. The mechanical design is stable, also in turbulent winds, but the major problem is the metal blade that does not withstand fatigue.

During the past two years, business has been very poor since the economy went down because of El Niño. Some big companies were forced to close and a number of my employees voluntarily took a leave knowing the situation. I will try to recall them as soon as we have rain and hope the business will recover. Over the past two years, I was able to sell three JB-150 windpumps and heard that people really appreciated it. However the problem is the lack of money. Last year we had a video coverage about windpumps by the English BBC that was broadcasted here. This video was a great source of information about the use of windpumps.

Recently we mounted larger bearings on the rotor axis of the JB-150, as the original bearing did not last long enough. Further, we eliminated the bearings in the lever arm that connects the pump rod and the connecting rod and replaced them with a rubber strip, thus reducing maintenance."

(Silverio T. Navarro Jr., Solar Electric Co. Inc., Lopez Commercial Arcade, E. Lopez Street, Jaro, Iloilo City, Philippines; email: jover@skyinet.net; Hector H. Jover, 104-A Divina Gracia Street, La Paz, Iloilo City 5000, Iloilo, Philippines; phone: (63)(912)520 1456; fax: (63)(33)335 1017; email: silver@iloilo.net)

 

Review of Mboro Village Windfarm

In the framework of the project "Eau pour les Villages" (Water for the Villages), a water supply facility was set up in the village of Mboro, Senegal, in 1988. The village has a population of 10,000 inhabitants and is located at the Atlantic West Coast at about 80-km from the capital Dakar. The facility consisted of: 10 ISEA wind-electric generators of 10 kW each, backed up by a diesel-generator of 36 kVA; a boring of a well with 50 m depth and a submersible centrifugal pump with a capacity of 110 m3/h; and a water reservoir of 2,000 m3.

The area is well known for its market gardening in the period from November till February, which coincides the period of highest wind speeds. The pumping facility was built to irrigate an area of 150,000 m2 and would be operated by a village association of 60 market gardeners.

The project was carried out by the Senegalese Ministry of Scientific Research and Technology and the Foreign Ministry of Italy. The families of market gardeners were organised and a plot of 2,500 m2 was fitted up for each of them. A village technician who had participated in the installation was trained to ensure the sustainable operation of the windfarm. Further, an agreement was made between the Scientific and Technical Affairs Delegation of the Ministry, and a heavy industry operating nearby, to authorise the villagers to use its infrastructure, cranes and pulleys.

From 1989–1991, the windfarm worked quite well and there was little maintenance and no fuel cost. Later, the rotor blades started to fail one by one. As the operator said: "The main problem encountered was the stick of the blades. Then, we failed to repair them because of a lack of proper documentation." By now, all the wind generators are out of service.

Despite the failure of the wind generators, the village association still exists. During the gardening period, a diesel-set is hired to provide power for the submersible pump. This pump has not failed once and produces water for irrigation. As the operator told: "From the lessons I learnt, I do hope an entrepreneur will rehabilitate the windfarm and hire two or three villagers to work in the garden, which would then be operated as a business and the whole community would benefit." He believes that private management would be much more efficient than a village association.

(Zaccaria Koïta, SENELEC Services Energies Renouvelables, 28 Rue Vincens, BP 93 Dakar, Senegal, phone: (221) 393 143, fax: (221)225 955; Alassane Niane, Délégation aux Affaires Scientifiques et Techniques, Ministère de la Recherche Scientifique et Technique, 23 Rue Calmette, Dakar, Senegal)

 


October 1999

EDITORIAL

The coming end of the year always submerges us into reflection, especially now it means a good-bye to the nineteen hundreds. Though many already announce it, in fact we must wait until the end of December 2000 to welcome the new millennium - assuming that the Year One finished at the end of the first year of the Western Era. Calendars are relative and far from perfect.

Our magazine, as small as it is, feels proud to bring its message to so many of the calendars in use on Earth; to Africa, China, India and to the American continent. To Israel and to the Middle East. Many of you left behind the Year 2000 already centuries ago, if not millenniums. Others must wait a little longer.

I write these words in Mexico City, which dresses like a Christmas tree in December. The increment of the electricity bill of the City of Cities for just this month will difficultly be matched by the generating power of all the small windmills together that will be installed in the next century. Evil tongues say that there exist small forgotten towns that pass these days in darkness, sacrificed to lighten a new cycle of life.

Christmas is the celebration of the light in the darkest days of the year on the Northern Hemisphere. It is winter solstice: may the Sun please think it over and come back one more year! With the arrival of electricity in apparent abundance, Christmas has become the party of the artificial light, and this interpretation has spread all over the world with the help of the expansionism and commercialising character of the western culture.

But it is precisely at the other side of the Equator where Christmas really is the party of the light. Perhaps nowhere on Earth the feelings of joy, heat and life are more tangible during these days than in Patagonia, even though for a nordic (as me) it may be difficult to conceive. Would Santa Claus -he is not exactly a saint- take off his hat while eating an ice cream? I am sure that, once completed his arduous task in the North, on the same Christmas morning he will straight set forth for his holiday in the South -and enjoy the light that has given life to our planet.

As the editor of SSWES I feel proud to know that our little seven years of existence have already brought us global coverage. The next year we hope to bring you better and faster communication when we hook up to the Internet and this way help to bring a bit of light to all those who are in need of it. Merry Christmas!

Remi Rijs, Arrakis

 

Electrification Project in Madagascar

The Dutch foundation "De Evenaar Projecten" (The Equator Projects) has scheduled to produce and install several Virya windchargers on the island of Madagascar. The windmills will be used for lighting the homes of families of artisans and provide energy for their workshops. After tests with the smaller Virya 2.2, the foundation aims at installing 20 Virya 3.3 windmills in the future.

Fair-trade organisation The Equator acts as an intermediate between the local people and sales companies in the Netherlands. Through its daughter-foundation The Equator Projects, it executes projects in two countries: Madagascar and Southern India. The main objectives are the improvement of logistics, the development and selection of products, as well as marketing.

On Madagascar, The Equator Projects currently supports a group of about 150 families of artisans who make toy cars from welded cans, as well as baskets and pottery. They supply to the local, commercial enterprise Vitagasy, made up of three shareholders: The Equator Projects, Solidarmad (an association of the families) and IREDEC, a local non-governmental organisation.

For the families, who live in the countryside, energy is a serious problem: charcoal has become scarce and expensive and there is no access to the electricity grid. Yet, they need a lot of coal for welding and foresee they will require more energy in the future to offer more varied products and of a better quality. Now the people have more money than before thanks to their handicrafts, they also start to think about having a radio or a television set. Therefore, The Equator Projects tries to find alternatives for the charcoal.

They came into contact with the designer of the Virya windmill, Kragten Design, just when they were in Madagascar to study the energy situation. They managed to get funding for the installation of the small Virya 2.2 windmill in the village Imertsiatuski where most of the families are concentrated. The approach of The Equator Projects is to begin slowly and with something small and manageable; their experience is that planning and organisation can fit well on paper, but that in practice things usually work out very differently.

As part of the tests, wind speed measurements were carried out during more than half a year and it seems that the wind resources are acceptable. It is important that the people already have a habit to charge car batteries at a grid connection point; therefore they have to travel considerable distances. These car batteries are used to light their homes. The people are used to pay for this electricity and The Equator is convinced that they should also pay for the wind-generated electricity. The tariff will be based on the costs of generation and probably be some 30% below the current costs.

The current electricity demand of a family is very low and estimated at not more than 0.5 kWh per two weeks. This will obviously increase if they want to connect new tools, such as a 70 W welding iron. The Equator Projects has calculated that a Virya 3.3 may produce 2-3 kWh/day under the prevailing wind conditions, which should be sufficient to supply five homes with electricity.

The choice of the battery size and type has not been covered yet. It is well known that car batteries are not very suitable and one will therefore start tests with deep-cycle batteries in January 2000. The battery issue is not only technical, since the local habits and the organisation of private property also interfere. In the future, solar energy might be a complement during low wind speeds, but the country´s very high import taxes (60%) may simply be prohibitive.

The idea is to install and test at least two Virya 3.3 windmills in Imertsiatuski. Here about 60 of the families who collaborate with The Equator Projects, are concentrated -other 90 live dispersed in remote areas. In the town are some good mechanics who could experiment with the equipment, carry out repair and put through modifications if required. The first two Viryas were built in Belgium, but the intention is to partly produce the following units in Antsirabe. The magnets, the generator box and the electronics will be bought in the Netherlands, but the construction and assembly should occur locally, possibly in collaboration with a technical school.

Very encouraging in this project is that new production methods are being achieved thanks to the arrival of the electric energy. Now the welding is carried out faster and with a better quality, which opens up new opportunities for diversification.

(information: Mr. Piet Pieters, De Evenaar Projecten, Bergstraat 18 - 5298 VK Liempde, The Netherlands; phone: +31 (411)632 112; fax: +31 (411)631 824; email: de.evenaar.projecten@wxs.nl)

 

IT Power’s Windpump under Testing

IT Power has put its innovative small windpump under testing in conjunction with counterparts in four countries (see SSWES, September 1996). The tests were commenced in the first half of 1999 and will take one full year. The outcomes of the tests will be used to finalise the windpump design and have a clear view on the performance under a variety of field conditions (average wind speed and pumping head). As a result, IT Power expects the local partner to be in the best conditions to fine-tune the basic concept to the specific local technical and market situation.

Currently, the parties involved are:

More information about the IT windpump will be included in the next issue of SSWES!

(information: Paul Cowley, Frances Crick & Peter Fraenkel, IT Power Ltd, The Warren, Bramshill Road, Eversley, Hampshire RG27 0PR, United Kingdom; phone: +44 118 973 0073; fax: +44 118 973 0820; email: itpower@itpower.co.uk; Web: www.itpower.co.uk)

 

Experiences with the Mexican Avispa-IIE Wind Generator

The "Avispa" Wind Generator

The small windcharger Avispa ("Wasp") is a development of the Institute of Electrical Research (IIE), which is the main research centre in this field in Mexico. The institute carries out R&D projects for the two national, state-owned electricity companies, the Mexican industry of electric components and the oil company PEMEX.

The Avispa is a product of the Alternative Energies group of the IIE and was designed to meet the energy demands at remote locations in areas with good wind conditions. It is a horizontal-axis, three-bladed windcharger with a fixed pitch and variable speed (Figure 1). The design wind speed is 11.5 m/s and the nominal power is 500 W. The system uses a three-phase car alternator with a nominal current of 75 A, driven by an accelerating belt transmission with a ratio of 1:2.5. The Avispa should perform well on sites with an average yearly wind speed of 4 m/s or more.

 

Figure 1: The Avispa-IIE windcharger

The orientation and safety mechanism is of the hinged side-vane type and protects the windmill against excessive rotor speed and vibration. An electric and a mechanical brake are foreseen for stopping the rotor (manually or automatically). The Avispa can be connected to a battery bank or integrated into a hybrid generation system. The output voltage is 12 V d.c.

 

Windcharger Avispa-IIE

rotor configuration 3-bladed, glass fibre
nominal power 500 W
rotor diametre 1.80 m
nominal wind speed 11.5 m/s
starting wind speed 3.5 m/s
tip speed ratio (lambda) 5
transmission ratio 2.5
electric generator car alternator, 12 V - 75 A
orientation system tail with hinged vane

Table 1: Characteristics of the Avispa-IIE wind generator.

The Hybrid System

The Avispa can be used as part of a hybrid system as depicted in Figure 2; apart from the wind generator, this includes several PV-modules; a battery bank; a main interrupter for disconnecting the batteries; an electric switchboard with control and safety functions; and a dumpload for the electric braking function. An electronic circuit connects and disconnects the windcharger, the PV-panels and/or the load in function of an algorithm that uses the battery voltage and time as input variables. The electronics should maintain the battery voltage within acceptable limits and this way avoid overcharge or deep discharge conditions.

 

Figure 2: Configuration of the micro-hybrid system.

For a hybrid power system of this kind, it is possible to predict the energy contribution of the windcharger using the available information about the local wind resources as an input data, for example the average monthly wind speed. Whether and to which extent this wind energy indeed is used, depends on the connected load and the intervention of the control electronics. The ratio between the total electric energy available for the load and the contribution of the wind generator is about 70%. This overall efficiency is very important for dimensioning the system and to meet the specifications under practical conditions.

Installation of the Hybrid Systems

In December 1995, twelve of these systems were installed in the centre for ecological tourism Villas Carrusel, located at the Paraiso beach on the Yucatan peninsula (Quintana Roo). Each of the systems was made up of one Avispa wind generator, a set of PV-panels (2x75 Wp), a set of lead-acid batteries and the electronic charge controller. The load consisted of "PL" high-efficiency lamps for lighting of the tourist homes.

Because of space limitations and to adapt to the architecture of the hotel, the wind generators were installed in-line at the roof of the main building on top of a tubular tower. The total installation height above ground level varied between 15.3 and 16.5 m with a tower length of 3.5 - 5.9 m; the distance between the wind generators was approx. 6.5 m. The systems were equipped with 2 PV-panels for a load of 132 Ah/day, and with 3 panels to provide 155 Ah/day. The total capacity of the battery bank was 570 Ah per system, giving autonomy for 2-3 days. The average wind speed at this site is about 5 - 5.5 m/s.

During the first year of operation "shading" problems occurred, which caused strong oscillations of the machines around the preferred direction of orientation, giving rise to fatigue of the blades and other elements. This problem was solved by reducing the sensitivity of the tail and incorporating some friction in the arm mechanism, together with an additional reinforcement of the blade structure. The effect was certainly related to the inevitable placement of the wind generators on top of the building, in combination with the prevailing wind direction during specific periods.

Conclusions

In general, one may say that the Avispa-IIE windcharger is reliable, safe and silent during operation; the integration of the windmill into a hybrid system has shown to be satisfactory as well. Once installed, the windmill works independently and is very convenient for the user. However, it does require a certain training of the personnel in charge in order to maximise the lifetime and availability. The actual installation of the system is not difficult but should occur in the right order and following the instructions, to ensure the correct mounting of the windmill, the physical integrity of the personnel and the appropriate operation of the system. All the instructions and recommendations for installation and operations are included in the user´s manual. The preventive maintenance takes up about one hour per month. The necessary tools are limited to a few keys, some grease and a safety belt for the operator.

The survival wind speed of the Avispa is 20 m/s; therefore, in case of higher winds or the approach of a hurricane, one should stop the rotor and fix it to the tower or better, dismount it to avoid serious damage.

The Avispa offers new opportunities for our country and satisfies the needs of users with small energy requirements. Experiences with similar systems from abroad have revealed many problems. These vary from simply not meeting the product requirements to an inappropriate application by the user, related to a lack of knowledge about the functioning and operation. The IIE believes that the Avispa, with local, technical support at hand, may be adopted by some national manufacturers and taken into a commercial production. This would mean an appropriate solution for one of the needs of the country with a product that is locally sustainable.

(Raúl González Galarza, IIE Instituto de Investigaciones Eléctricas, Reforma 113, Col. Palmira, Apartado Postal 475, Temixco (Mor), CP 62000, Mexico; phone: 52-73-183 811; fax: 52-73-182 436;email: rgg@iie.org.mx)

 


 

 

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