Renewabh" Ener, qy Vol. 3. No. 8, pp. 907 91 I, 1993 0960-1481/93 $6.011+.00 Printed in Great Britain. Pergamon Press Ltd THE USE OF SMALL HYDROELECTRIC POWER PLANTS IN THE AMAZON MANOEL FERNANDES M. NOGUEIRA, CARLOS UMBERTO DA S. LIMA and RAIMUNDO ROSEMIRO P. RIBEIRO Universidade Federal do Para, Campus Universitario do Guama, Centro Technologico, 66059 Belem-Pa, Brazil Abstract Generating power with large hydroelectric plants and sending the electricity to supply users by networks of transmission lines is the present system adopted in Brazil. This system presents many difficulties in the Amazon rain forest. In that region, there are many small towns (few need more power than 500 kW) : they are far from each other : the lines must cross large rivers and permanently exist in the tropical and humid jungle. Both the hydroelectric plants and lines have a violent environmental impact. Further difficulties are presented by the roads to the isolated cities which are bad or simply do not exist. Based on this analysis, faculty members of the Federal University of Para (UFPA) concluded that the best way to solve the problem would be to build isolated power plants using small rivers of the region. These make a small environmental impact, supply high quality energy all day long, and need little operation and maintenance attention, which can be done by the people of the community that will receive the energy. Today, this energy is supplied by small diesel engines for only a few hours a day, and used more for domestic needs than to improve agricultural or industrial production. 1. THE BRAZILIAN ELECTRICITY SYSTEM Brazil is a country with large geographical dimen- sions. Its topography varies from region to region and its hydrographical basis presents different hydro- logical cycles. For this reason, the government decided to build and connect hydroelectric power plants in order to attend to the demands of the consumers. This way, a spell of dry weather in one area would mean that help could be provided by hydroelectric plants in another area. This system was first implemented in the south of the country where the topography and the flora were appropriate to the construction of the hydroelectric plants and their transmission lines. When the hydro- logical resources of that region were declining, the system was expanded to the northeast and west regions of the country and finally to the Amazon region. 2. THE PROBLEMS THE CONNECTED SYSTEM FACED IN THE AMAZON The rivers of the Amazon Region which form tribu- taries of the Amazon River carry much water but there is large variation in measurements of tide reflux this variation being about 5:1. In addition, they are low speed rivers becausc their declivity is small, and to build a large or medium size hydroelectric power plant in the region it is necessary to have a large lake. The cost for transportation and maintenance is very high because the infrastructure of the region is very poor. The price for removing wood from flooded regions is so high that this project is unfeasible. The submerged trees rot and release gases that pollute the water and create health problems for the inhabitants of the area. It is not possible to foresee a date for the regen- eration of all existing large hydroelectric power plants in the region. In order to carry electricity to consumers, it is necessary to travel long distances through tropical forest, which entails clearing 100 m each side of the power line, and developing a process to prevent the forest regenerating. The power lines have to cross large rivers, which entails building high towers on the banks or in the centre of the rivers. The cost of a power line is equivalent to the cost of a plant in the Amazon Region. The electricity from these plants can be beneficial only to those projects where large amounts of elec- tricity is used or in the few villages with state and federal roads, along which the power lines can run. Even some regions that have road systems do not receive electricity because it is not economically prac- ticable. The villages and small towns are far from each 907