|GATE - 1/84 - Wind Energy (GTZ GATE, 1984, 56 p.)|
by Gerd Spenk
Techniques for converting wind energy into mechanical energy, for pumping water or for driving simple machines such as mills, have been known for centuries. From the mid-19th century onwards, wind pumps in the form of multi-bladed wind turbines came to be used extensively, especially in the Mid-West of the United States, and later also in other countries. In the course of the 20th century these Installations have been Increasingly replaced by motor pumps powered by cheap diesel fuel or electricity.
As a result of the drastic rises in oil prices at the beginning of the 1 970s, energy planners have once again been turning their attention increasingly to the utilization of wind energy. State-sponsored research and development grants have provided a fresh stimulus to the development of technology for the utilization of wind energy. Efforts have been concentrated on developing wind energy converters for generating electricity, because in the industrialized countries the application of wind pumps is of minor importance.
On the other hand, wind pump technology is still of major interest for applications in the developing countries because of the importance of water supplies in rural areas, and the relative simplicity and transparency of the technology. It was this reasoning that prompted numerous technologists and engineers dedicated to development aid to improve wind pump technology.
This article is concerned with the relative value of wind pumps as part of the energy mix in rural areas.
Wind Pumps as a Source of Energy in Rural Area
In view of the varying amount of wind energy available and the fact that, for economic reasons, the amount of storage capacity is limited, it can only be assumed in extremely rare cases that a single wind pump installation will be capable of ensuring a 100 percent reliable power supply. Hence, as a rule, these renewable energy sources can only be used as part of a combination of different systems appropriate to the case in question.
This means that for pumping water, be it for a drinking water supply, irrigation, or drainage, a suitable combination of different pumping systems with an optimized storage capacity should be installed. For small pump capacities up to approx. 10 m³/d, systems such as hand and foot pumps, capstans and, with certain limitations, solar pumps may be considered in addition to wind pumps where the water requirement is greater, motor pumps (diesel or electric) become competitive.
The question as to which combination of possible systems is the right one, i.e., the one which is most economical and best adapted to local conditions, depends on a variety of physical, socio-economic and sociocultural conditions which can differ considerably from one region to another. All of these conditions, which are not dealt with in more detail here for reasons of space, are of vital importance in the planning of rural water supply systems. Failures of projects for the introduction of wind pumps can, without exception, be traced back to the non-obervance of one or more of these conditions or prerequisites.
Thus, for example, a combination of wind and hand pumps can be the right solution for providing a drinking water supply for a settlement, always provided that there is a sufficient amount of wind available. In the case of a small-scale irrigation system with wind pumps, a small, transportable diesel pump which can be used by several farmers is more suitable as a back-up system.
In addition to local business management considerations for the user, national economic factors should also be borne in mind. If wind pumps can be manufactured and extensively used in the country concerned, thus substituting imported diesel pumps, for example, then there will also be a positive effect on the national economy, such as a saving of foreign exchange, an easing of unemployment, and the development of technological expertise. Therefore, it should be considered whether encouragement to buy locally manufactured equipment can be given in the form of state sponsoring measures such as subsidies or low-interest loans, even when - from a business management viewpoint - it would be better to use imported equipment for the water supply installation.
A Case in Point - Tunisia
To conclude this article with an example, developments in the use of wind pumps in Tunisia are described.
The first few wind pumps were installed in widely dispersed locations in the 1 920s. In the 1 950s their numbers increased sharply, until there were up to 500 installations in use. Most of the wind pumps were concentrated on the extremely fertile Cap Bon peninsula, where they were used for garden irrigation and to provide drinking water supplies. The majority of them were imported American pumps made by Samson, Aeromotor or Dandy and had an average daily capacity of approx. 30 m³; practically all of them were privately owned. Even at that time, the purchase price was about 1800 diners. Servicing and repairs were carried out by small-scale local enterprises.
Since 1960, the number of installations in use has been on the
decline. There are two main reasons for this:
- The Tunisian government began to subsidize the purchase of diesel pumps, and later also of electric pumps;
- it became increasingly difficult to obtain spare parts.
Even so, out of over 100 wind pumps installed in the Hammamet region, about 20 percent are still in use.
As the prices of commercially available sources of energy continue to increase, the use of wind pumps is being reconsidered in Tunisia, as elsewhere. Endeavours are being made to repair defective wind pumps and to produce wind pump installations in Tunisia. During the last few years one small service company has built several such installations. The possibilities of industrial production are also being studied.
Wind pumps are also being used increasingly in state development projects in northern Tunisia. Not only are new installations being bought; pumps which where no longer in use are also being purchased, dismantled and re-assembled at new locations. This is now being done without outside help: the work is carried out by Tunisian mechanics, who are subsequently also responsible for maintenance and repairs.
Similar undertakings are at present in progress in other countries; it remains to be hoped that this development, backed up by careful planning and aided by a mutual exchange of experience, will continue successfully.