PERGAMON Renewable Energy 16 (1999) 944-947

IUM SIZE WIND TURBMES:

Paper prepared for the World Renewable Energy Congress-V Florence, 20-25 September 1998

William Hopkins, B.Eng, M.Sc, D.1.C VERGNET S.A.

6, rue Henri Dunant 45 140 Ingr.6

Orleans FRANCE

Summary Ar a time when wind turbines are getting

larger. and the electricitv injected into the nrid fiok ‘kbines is becoking- more compet&e, VERGNET has chosen the small scale wind turbine side of the wind energy market to develop its business.

I. Introduction As wind turbines in recent years have

progressively become larger, more reliable and produce electricity at more competitive costs, VERGNET has concentrated on the development and the manufacture of smaller wind turbines, in the power range of 1 kW to 200 kW aimed at supplying electricity to sites where wind energy can already provide a competitive alternative to conventional solutions.

Rather than competing directly with cheap electricity on interconnected grids generated by fossi and fissile fuels, why not compete against the more expensive kWb generated on small electricity grids powered by diesel generators ? Rather than concentrating energy produced from the wind with a large turbine and distributing it, why not take advantage of the diffusion of wind energy to install smaller wind turbines, closer to the end users?

The lower energy output per swept area from smaller wind turbines inevitably means that the cost per installed kW is higher than that from a large wind turbine. However, there are many windy areas in the world where access is limited for cranes and heavy trucks for installation and maintenance, where weak grids can only accept small power inputs or where there is no grid at all. A smaller, reliable and versatile wind turbine is often the most economic solution.

?? Electricity supply to remote sites : reliable and cheaper than traditional

?? Integration of small- to medium

MW (embedded generation or wind-

II. Markets These applications for wind energy are by

no means new, small turbines have been charging batteries ever since the 1930s and “large” grid connected wind turbines were in the 50 kW range just ten years ago. However, small to medium power wind turbines have benefited in recent years from their uptake by professional and industrial companies.

New turbines have been developed in the medium power range from 10 kW to 200 kW which combine reliability, simplicity, flexibility and include technical develooments from the larger wind turbines. VERGN’&T has developed since 1989 a ramre of wind turbines from 1 kW to 200 kW. Th&.e turbines can be installed in compkx and diffkult access sites thanks to their tiltable guyed towers, they are resistant to very hizh winds - even cvclones. sand storms and sea sP;ay, can operate. ii temperatures from -H)oC to +5O*C and enable high wind energy penetrations into diesel powered grids.

0960-1481/99/$--see front matter 0 1998 Published by Elsevier Science Ltd. All rights reserved. PII: SO960-1481(98)00334-6

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Thanks to the success of the large wind turbine market, small to medium power wind turbines have also benefited from their image of Credibility, reliability, performance and professionalism.

The approach to the market has also changed, it has been recognised that electricity supply to island communities, however small, requires all the ingredients of a conventional power project: technician training for operation and maintenance, availability of spare parts, constructor performance and generation guaranties and even financing packages including public money and private investment. For a remote site application, the customer has the right to expect the reliability and security that a grid extension would offer - this requires an efficient after sales service.

VERGNET keys to success in this market al-e:

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reliable and robust technology, designed for installation, operation and maintenance in complex conditions a private and high wind test site in France equipment, performance and production guarantees systematic training of local technicians for operation and maintenance world-wide availability of spare parts to be prepared to become involved in the financing of projects

This approach to the use of wind energy has revealed a large market which VERGNET has only started developing.

III. Applications

111.1. Wind- Diesel ‘he most economic application of wind

energy in this range is connected to decentralised diesel grids of a few tens of kW to a few MW. Gn small grids powered by thermal power plants, relying on expensive supplies of fossil fuels and high maintenance costs, a wind farm made up of a number of small units can make an important contribution. Until recently, the connection of wind turbines to a grid was limited to supplying a small proportion of the total load: 10 to 15%.

Today, VERGNET has achieved high wind energy penetrations - in some conditions covering 7O% of the total load.

The need for such penetrations is essential to conquer the market for small isolated or island grids in the windy regions of the world. Indeed, to suggest to an electricity utility a displacement of only a few percent of diesel generator operating hours by wind energy would not have been sufficient, given the turbine capital costs, necessary extra training and specific wind-diesel plant management.

A wind-diesel system typically consists of 5 to 30 turbines, connected in low or medium voltage to the grid. VERGNET continuously adjusts the number of wind turbines connected in order to optimise the wind resource and to follow the load while maintaining the diesel generators above their minimum design load. Each turbine is opemted automatically and independently, which makes the system extremely reliable.

The cost per kWh is naturally higher than that from larger turbines, but with costs between 8 and 12 US cents per kWh wind energy becomes competitive compared to costs of diesel power, which am often above 12 US cents and can sometimes reach over one US dollar depending on location and accessibility. The main cost of wind generated electricity is the initial capital cost and the amortisation of the equipment. The operation and maintenance costs are very low, these recurring costs are affordable by small villages who often suffer from cash flow problems.

For all the small island grids of Cap Verde (western Africa), the Caribbean, the Mediterranean, on the east coast of Canada and the isolated grids of Siberia, Northern Canada, Morocco, etc.. wind energy can now offer an exttemely attractive and economic solution alternative.

VERGNET reckons wind-diesel applications represent the most significant market for turbines in the 10 kW to 200 kW range: it concerns hundreds of millions of people world-wide.

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111.2. Autonomous wind powered grids

Another particularly promising application is “the autonomous wind powered grid” (see fia.1). Rural electrification bv solar photovoltaics has been disseminated for remote and dispersed sites whose energy requirements are very low. The case for energy supply to relatively small villages with higher electricity demands - unable to afford a collective electricity supply system, has until recently not found an affordable solution. Diesel generators require maintenance, technical know-how, significant spare parts and consumables, which does not give satisfaction and in all cases induce high kWh costs.

A solution developed and implemented by VERGNET, first on the islands of Cap Verde and then more systematically, consists of power generation systems including wind turbines of 10, 25 or 60 kW, associated to battery storage and an inverter. A diesel generator back-up guarantees, in case of need, security of supply.

The power output from the invetter is distributed via a low voltage grid to the consumers, in general up to a hundred inhabitants, equipped with preferably efficient but conventional AC powered equipment. As in conventional systems, the consumers have energy meters and pay for their electricity to an operator. This solution has the same advantages as conventional electricity supply service with more significant power levels than with photovoltaics: users can power conventional equipment and small industrial facilities such as welders, lathes, saws, drilling,etc.

III.3 Remote site electrification Another application, which has been applied

many times in the French overseas territories, but -also in France and in other European countries. is the electrification of individual remote sites where the electricity grid has not been able to reach due to cost.

For sites with sufficient wind resource (over 5 m/s annual average), a wind energy system can offer a reliable and economic solution able to power all conventional domestic electrical equipment.

III.4 Other applications i) Weak end of grid support At the weak ends of grids, where the length

of distribution line per consumer is high, any increase of power demand over and above that originally designed for will create voltage drops thereby reducing the quality of supply to the customer. Small to medium size wind turbines connected to grid end-points in windy sites can produce power at competitive costs compared to distribution and line maintenance costs in rural areas with low population density. A wind turbine can alleviate the need for the reinforcement of grid lines with a lower investment.

VERGNET has supplied 8 turbines to the Italian electricity utility ENEL for this application.

Reverse Net Billing is also an attractive application where a private user can generate power for their own use and discount excess g;er fed into the grid from their electricity

ii) Water pumping A wind energy pumping system consists of

a wind energy converter and a submersible or surface pump. It operates without electricity storage, the water is pumped when there is wind and stored in a reservoir to satisfy a continuous demand. The wind turbine generates AC current, it can be installed up to 500 metres from the water source, which enables the choice of the best site and optimum wind resource. Water volumes can reach 200 m3/day (at a depth of 20 metres) - which is suitable for irrigation.

iii) Sea water desalination In many areas of the Mediterranean but also

in the coastal regions of developing countries, over consumption of limited resources of potable water is causing salt infiltration, lack of water availability at reasonable costs and migration of populations towards urban areas - which are in turn being confronted with potable water supply problems.

This is also the case in many islands and coastal regions in other parts of the world, such as Cap Verde, Mauritania, the Caribbean, Brazil, etc.

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The use of wind energy for the production of potable water by sea water desalination (reverse osmosis) constitutes a serious opportunity to satisfy needs in these regions, the reliability achieved by wind energy technologies today and the availability of the resources in the regions concerned enable the production of potable water in quantities up to 50 m3/day in positive economic conditions.

IV. Conclusions With the improvements of small to medium

power wind turbine technology, the market is realising the benefits of decentralised systems, where obiections to noise and visual impact are very much reduced. The industry can offer these turbines, at cost-effective pfi~e-~ able to withstand extreme conditions and provide for the first time an economic and reliable service.